| 1. |
- Elustondo, Diego, et al.
(författare)
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Mathematical modeling of moisture evaporation from foodstuffs exposed to subatmospheric pressure superheated steam
- 2001
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 49:1, s. 15-24
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a reduced expression to calculate the drying rate of foodstuffs being dried with low pressure superheated steam is developed. It is based on a theoretical drying mechanism which assumes that water removal is carried out by evaporation in a moving boundary making the vapor to flow through the dry layer built as drying proceeds. The theoretical model can be applied to any form and features dimensionless parameters to allow for the influence of form, shrinking effect and boiling point rise. To make the application easier, a simplified expression was derived, which has only two experimentally determined parameters and allows the calculation of the drying rate of a given product. Different foodstuffs were dried with this technique and the empirical parameters were calculated from the experimental data fitting equation. Interestingly, those parameters can be considered constant within the 10000-20000 Pa pressure range and the 60-90°C temperature range
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| 2. |
- Elustondo, Diego, et al.
(författare)
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New thermal conductivity probe design based on the analysis of error sources
- 2001
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 48:4, s. 325-333
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity determination by means of the thermal probe is a classical non-stationary method, suitable for foodstuffs because of the relatively short period of time and the small temperature rise required during experimental measurements. Even though its simplicity, this method has theoretical and practical implicit errors, their main sources being evaluated in this paper. The theoretical analysis shows that experimental errors can be kept within acceptable values, if the testing time period is within certain limits, out of which the errors grow quite rapidly. The error arising from the calculation of the thermal conductivity by means of an approximate equation is studied and a new way to express it is presented. Also, testing times were calculated for different probe dimensions. Finally, on the basis of two former probe which exhibits some advantages upon each other, a new probe design is proposed which recoveries those features.
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| 3. |
- Funebo, Tomas, et al.
(författare)
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Microwave heat treatment of apple before air dehydration : Effects on physical properties and microstructure
- 2000
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 46:3, s. 173-182
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Tidskriftsartikel (refereegranskat)abstract
- Golden delicious apple cubes were heated with microwave energy of high intensity (20 W/g), as a pre-treatment before air-dehydration at 40 °C, 60 °C and 80 °C. After the microwave treatment extending for 0.75 up to 5 min, the cubes were finish-dried with only forced air at 2 m/s. Dehydrated and rehydrated samples were analyzed with a puncture test using a texture analyzer. The microstructure of the samples was studied with confocal laser scanning microscopy (CLSM). Dried apple pieces were harder and more shrunk when pre-treated with microwaves, compared to only air dehydration. Despite the shrinkage and increased firmness, the rehydration capacity of microwave `blanched' apple cubes was higher than when they were only air-dehydrated. Image analysis of the rehydrated apples showed that large voids (up to 0.5 mm in diameter) had developed, and that these increased with air temperature. Higher magnification of the images revealed cell separation and disruption of cell walls, caused by the microwave heating.
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| 4. |
- Prothon, F., et al.
(författare)
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Application of the Guggenheim, Anderson and De Boer model to correlate water activity and moisture content during osmotic dehydration of apples
- 2004
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 61:3, s. 467-470
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Tidskriftsartikel (refereegranskat)abstract
- Water activity and moisture content are the most valuable characteristics for assessing the stability of dried foods. The aim of this work was to evaluate if a desorption isotherm model could be used to describe the relationship between the water activity and moisture content in the product during osmotic dehydration. This model can lead to a better understanding of how water activity of a product can be reduced during osmotic dehydration. The Guggenheim, Anderson and De Boer (GAB) model was chosen because it has been proven to best fit the desorption and adsorption of foods over a large range of water activities. The studied material was apple pieces, and the osmotic medium with a water activity of 0.939 was prepared with sucrose. The osmotic dehydration process was studied by collecting moisture content and water activity data at different temperatures and times. The model was shown to fit well the experimental points at temperatures 25, 45 and 55 °C. At 65 °C, however, the model is satisfactory if aw is below 0.970 but not above. The effect of temperature can be expressed on the C-parameter of the GAB model. © 2003 Elsevier Ltd. All rights reserved.
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| 5. |
- Skjöldebrand, Christina, et al.
(författare)
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A computer simulation program for evaluation of the continuous heat treatment of particulate food products. : Part 1: Design
- 1993
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 20:2, s. 149-165
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Tidskriftsartikel (refereegranskat)abstract
- Computer simulation programs used by the food industry today are not very well developed, partly because few food processes ar easily described by mathematical equations. The heat treatment of food, however, is one group of processes for which mathematical modelling exists. Programs used for prediction of the time-temperature relationship for various food products during heat treatment have been developed at SIK. A specially designed program calculates the temperature in viscous liquid foods with discrete solid particles. This program facilitates study of the influence of processing conditions on the product quality in an aseptic processing system. The F value is a measure of the safety and a so-called C value (cook value) is a measure of the quality of the product. The simulation program has been further developed to take into account product flow rate, residence time distribution, particle size and geometry, equipment specifications, particle load and the thermal properties of the product. The simulation program makes it possible to analyse the entire sterilisation system, including cooling, and determine the required holding time to reach a desired lethality value in the centre of the fastest-moving particle. The design of the program is described in this paper, and some applications are treated in a following paper. © 1993.
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| 6. |
- Skjöldebrand, Christina, et al.
(författare)
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A computer simulation program for evaluation of the continuous heat treatment of particulate food products. : Part 2: Utilisation
- 1993
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 20:2, s. 167-181
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Tidskriftsartikel (refereegranskat)abstract
- A computer program for calculation of temperatures in a liquid containing particles during continuous heat treatment has been developed at the SIK. The program facilitates the study of the influence of processing on product quality in an aseptic processing system. The calculated F value is related to the safety, and the cook value (C value) is related to the quality of the product. In this paper, results of some calculations using the program are presented. They concentrate on the influence of the processing conditions on the process design. These results indicate that factors such as particle heat transfer coefficient, both in the holding tube and in the scraped surface heat exchangers (SSHEs), flow conditions, particle diameter and sterilisation temperature have consequences for the holding tube length, i.e. the processing time, for a given lethality. For example, for small particle heat transfer coefficients (< 100 W m2 K), a small change will have a large effect on the required processing time (i.e. the holding tube length). However, at particle heat transfer coefficients > 150-200 W m2 K a small change does not greatly affect the processing time (i.e. holding tube length). The program can thus be used to examine whether the surface heat transfer coefficient is the rate-limiting factor, or whether the heat conduction inside the particles is more important in the design of the process. © 1993.
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| 7. |
- Skjöldebrand, Christina, et al.
(författare)
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Optical properties of bread in the near-infrared range
- 1988
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 8:2, s. 129-139
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a method for determination of the optical properties of bread. The optical properties of white bread have been studied. The measurements were carried out for dough, crumb and crust. The transmission and reflection measurements were made with a Beckman spectrophotometer with an integrating sphere. Transmission functions and penetration depths were calculated and compared with previous investigations made at this institute (SIK). The influence of peak power wavelength and spectral range (800-1250 nm and 1250-2500 nm) on the penetration depth for crust and crumb have been determined. This study has shown that it is possible to calculate penetration depth for any radiator using transmission data in the range 800-2500 nm. © 1989.
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| 8. |
- Thorvaldsson, K., et al.
(författare)
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A model for simultaneous heat, water and vapour diffusion.
- 1999
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 40:3, s. 167-172
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Tidskriftsartikel (refereegranskat)abstract
- A model for simultaneous heat, water and vapour diffusion was developed to use for prediction of the diffusion of water inside foods during heat processing. The model is based on Fourier's and Fick's Laws. The diffusion of liquid water is separated from the diffusion of water vapour. The model was evaluated in a drying process. Slabs of bread crumbs, 12×12×2 cm3 in size, were dried in a conventional oven at 210 °C and the local water content and temperatures were measured during the drying in the centre, halfway to the centre and at the surface. From the measurements, the diffusion coefficient as a function of temperature and concentration and several other material parameters were estimated. The results show that the measured water content slowly increases in the centre of the sample. During the increase, the temperature remains on a plateau. When the centre starts to dry the temperature increases. Halfway to the centre the water content also increases slightly before it starts to dry out, while the surface starts drying immediately. The simulated water content levels and temperatures conform well to the experimental values and show that the evaporation and condensation model describes well the diffusion mechanisms in a porous food.
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| 9. |
- Thorvaldsson, K., et al.
(författare)
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Method and instrument for measuring local water content inside food
- 1996
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 29:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- A new method of measuring local water content inside food during heat processing has been evaluated. The method uses a fibre optic NIR-Instrument. The evaluation was mainly based on investigations of the influence of structure and temperature. The instrument was found to be very sensitive to both the structure and the temperature of the sample. The dependence on the temperature of the sample can be incorporated into the calibration and is thereby not an impediment to the measurements. The structural dependence makes quantitative measurements at different places in the sample difficult for inhomogeneous materials. However, measurements of dynamic changes in the water content in one spot work well for both homogenous and inhomogeneous materials and are probably the best application of the instrument. By using two or more optic fibres, the diffusion of water can also be measured. Copyright © 1996 Elsevier Science Limited.
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| 10. |
- Thorvaldsson, K., et al.
(författare)
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Water transport in meat during reheating
- 1996
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 29:1, s. 13-21
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Tidskriftsartikel (refereegranskat)abstract
- A study of heat and water transport in meat during a heating process was conducted. The meat samples were heated from 10 to 100°C in a conventional oven at 175°C and local water content and temperatures were measured during the heating process. Using whole meat from bovine muscles, the mechanism behind water transport inside the sample during heating was investigated. The anisotropy of meat in terms of heat and water transport was also studied. The study yielded two main results: When heating commences, water moves towards the centre of the samples. At a centre temperature of ?70°C, water transport stops and changes direction. A theory for transport phenomena has been developed and is described in this paper. The results also indicate that, as expected, both water transport and heat transport are faster parallel to the meat fibres than perpendicular to them. Copyright © 1996 Elsevier Science Limited.
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| 11. |
- Walkenström, Pernilla, et al.
(författare)
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Effects of flow behaviour on the aggregation of whey protein suspensions, pure or mixed with xanthan
- 1999
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 42:1, s. 15-26
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Tidskriftsartikel (refereegranskat)abstract
- The effect of prior thermal treatment on radiation sensitization were investigated on proton irradiated Type 304 stainless steel (SS) of initially as-received (AR) and thermal-sensitized (SEN) conditions. The Cr depletion profiles were measured by field emission gun transmission electron microscopy/energy dispersive spectroscopy (FEGTEM, EDS), and were calculated by a radiation induced segregation (RIS) model. The different initial conditions were input in the RIS model calculations. For the as-received condition, the initial Cr profile was modeled by a uniform concentration distribution. Overall, the results show that radiation sensitization is characterized by a very narrow Cr depleted zone.
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| 12. |
- Wählby, Urban, et al.
(författare)
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Impact of impingement on cooking time and food quality
- 2000
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 43:3, s. 179-187
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study has been made, with the objective to find the impact of directed forced convection (impingement) on food quality. Two different foods were chosen for the study, yeast buns (representing category bread) and pork cutlet (representing meats). The tests were made in an experimental oven intended for the domestic market. The main results were a shorter cooking time and more uniform browning for meat (a reduction by up to 50% at similar air temperature as recommended). For smaller pieces of meat, browning was a general problem, as centre temperature increased to rapidly, at the air temperatures tested here. Buns were slightly more uniform in browning on the surface. The cooking time was basically similar to a traditional oven, but at much lower air temperature setting.
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| 13. |
- Wählby, Urban, et al.
(författare)
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NIR-measurements of moisture changes in foods
- 2001
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 47:4, s. 303-312
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Tidskriftsartikel (refereegranskat)abstract
- Mass transfer and especially the movement and loss of water are important for the quality of cooked foods. Measurements of the water content changes during cooking are therefore valuable when it comes to controlling cooking processes. A near infrared reflection fibre optic probe is here used to measure water content changes inside pork meat and buns during heating. The results are compared with a moist porous brick (in the following called model food). Five different periods were seen locally in the centre. First a period of constant water content, then a period of constant decrease (constant rate period). The constant rate was followed by a period, an intermediate period where the temperature levelled at 100 °C, while the water content decrease was small. In the fourth period the slope of the water content vs time curve became steeper and the temperature began to increase above 100 °C. Finally, the water content moved to zero while the temperature rose towards the air temperature. The results for buns indicated that the water content near the surface began to decrease almost instantly and continued for the whole heating time in a falling rate manner. At the centre, the water content fell initially and then levelled. The major difference compared to the model food was the levelling off temperature, roughly 100 °C in the food and 75 °C in the model food.
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| 14. |
- Wählby, Urban, et al.
(författare)
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Reheating characteristics of crust formed on buns, and crust formation
- 2002
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 53:2, s. 177-184
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Tidskriftsartikel (refereegranskat)abstract
- The idea of this paper to examine some characteristics of crust formation during baking of yeast leavened dough. The aim is to find the impact of the crust on the heat and mass transfer rates. In a second test series, buns were baked under different conditions, and the rate of crust browning and thickness evolution was followed. The aim was further to see whether a baking at 145 °C under high convective boundary conditions could match traditional baking (hot air at 175 °C and top-bottom at 200 °C). Ready baked buns were reheated some with and some without (peeled off) crust. The results show a difference in heating behaviour. The temperature in buns heated with crust rose faster and levelled off at significantly higher temperatures than in buns without crust. The buns heated without crust lost weight at a rate about three times that of buns with crust. Air temperature and velocity influenced the loss rate for both kinds of buns. For the comparative study, it was found that although the internal heating rate of the buns was similar for the three heating technologies, the crust browning was faster and greater in the traditional processes. It was also found that the rate of browning is not significantly increased by impingement, even when varying the air velocity. © 2002 Elsevier Science Ltd. All rights reserved.
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| 15. |
- Åström, Annika, et al.
(författare)
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Heat transfer between fluid and particles in aseptic processing
- 1994
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 21:1, s. 97-125
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Tidskriftsartikel (refereegranskat)abstract
- The particle heat transfer coefficient, hfp, is one of the critical factors, besides the residence time distribution, that has to be known for the design and development of continuous heat processes of particulate food products. In the present work, data and methods for determining hhp for conditions relevant to aseptic processing have been studied. The influence of product characteristics, such as size and composition of particles, fluid properties, temperature differences and fluid motion, have been investigated. Among the parameters investigated, the flow field around the particles was shown to be the most important for heat transfer but for special conditions the particle size, particle shape or thermal properties of the particle, as well as the apparent viscosity and the thermal properties of the fluid, are equally important for the value of hfp. For safety considerations, the present investigation indicates that hfp values corresponding to an Nu value of 5-6 should be relevant for medium-sized spherical particles transported by a highly viscous liquid. For the quality aspects, different conditions have to be considered. Particles at different positions in·the tube flow will experience different heat transfer. The few particles in the centre of the tube will experience a low heat transfer and hfp values corresponding to Nu values ranging between 5 and 10. The larger amounts of particles are transported in the liquid with a pronounced velocity gradient which yields Nu values of 10-17, while for extreme conditions occurring for sedimented particles, Nu values between 20 and 45 could be expected. © 1993.
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| 16. |
- Andersson, Johanna, et al.
(författare)
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Comparison of steaming and boiling of root vegetables for enhancing carbohydrate content and sensory profile
- 2022
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 312
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Tidskriftsartikel (refereegranskat)abstract
- Root vegetables have unique techno-functional and nutritional properties however, their use in processed foods is limited to a few species, partially due to a lack of knowledge related to the impact of thermal treatments on the sensory properties. This study investigated the effect of steaming and boiling on the microstructure, mechanical properties, and sensory profile of three model root vegetables with distinct carbohydrate composition: Jerusalem artichoke (Helianthus tuberosus L.), parsnip (Pastinaca sativa), and beetroot (Beta vulgaris). Thermally treated Jerusalem artichoke and parsnip showed higher content of cell wall polysaccharides, particularly β-glucans (e.g. cellulose) and pectic components, compared to raw. Steaming produced more cell shrinkage and loss of cell-cell adhesion than boiling, leading to softer vegetables. Processed beetroot showed loss of cell turgor and drastic softening but not clear changes in overall carbohydrate content. The scores for several flavour and in-mouth attributes were higher for steamed vegetables compared to boiled. Our results give insights on the processability of root vegetables towards products with enhanced sensory and nutritional properties.
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| 17. |
- Berta, M., et al.
(författare)
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Correlation between in-line measurements of tomato ketchup shear viscosity and extensional viscosity
- 2016
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 173, s. 8-14
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Tidskriftsartikel (refereegranskat)abstract
- The viscosity and shear thinning behavior are essential characteristics of tomato ketchup. A real-time monitoring of those characteristics during processing is important to obtain a good quality of the final product and to reduce production waste. This work investigates the measurement of rheological in-line flow properties of tomato ketchup, using a real-time technique that combines ultrasound velocity profiling (UVP) and pressure difference (PD) assessment. In-line data were compared to those obtained off-line using a rotational viscometer. There was a poor correlation with the Bostwick measurement, whereas the flow curves calculated from flow velocimetry data were very similar to those measured off-line. The extensional viscosity of ketchup was determined through the measurement of Hyperbolic Contraction Flow; the curve followed a trend similar to that for the shear viscosity over the deformation rate investigated.
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| 18. |
- Bor, Yasemin, et al.
(författare)
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Polylactide stereocomplexation leads to reduced migration during microwave heating in contact with food simulants
- 2014
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 134, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- The effect of stereocomplexation on the stability and migration resistance of polylactide during microwave and conventional heating in contact with different food simulants was evaluated. The heating effects were followed through mass loss measurements, molecular weight measurements and identification of the individual migrants by electrospray ionization-mass spectrometry (ESI-MS). Increased mass losses were observed as a function of time and temperature, but approximately 50% smaller mass losses were always measured for PLA stereocomplex as compared to the corresponding regular PLEA material. The stability of the stereocomplex material was, thus, significantly higher. Microwave heating increased the mass loss as compared to the conventional heating at the same time and temperature. This effect was especially significant when 10% ethanol was used as food simulant instead of water. The amount of water-soluble migrants was in most cases under the detection limits, but when heating temperature was increased to 95 C, ESI-MS revealed the formation of homologous series of linear lactic acid oligomers. Results indicate that PEA stereocomplex materials could have potential in single-use microwave applications.
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| 19. |
- Botha, G.E., et al.
(författare)
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Microwave assisted air drying of osmotically treated pineapple with variable power programmes
- 2012
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 108:2, s. 304-311
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Tidskriftsartikel (refereegranskat)abstract
- Variable power programmes for microwave assisted air drying of pineapple were studied. The pineapple pieces were pre-treated by osmotic dehydration in a 55° Brix sucrose solution at 40 °C for 90 min. Variable power output programmes were designed and ran with different inlet air temperatures between 30 and 70 °C. Results indicated that the use of variable microwave power combined with low air temperatures can result in a fast drying process without significant charring of pineapple pieces. High microwave powers need to be reduced quickly, faster than the decrease in water content would suggest, to minimize charring. In this study an inlet air temperatures of 70 °C was found to be excessive when combined with microwave energy (5 W/g - after compensating for the moisture loss), resulting in fast temperature increase. Microwave power was found to be most effective in the first hour to 1.5 h of processing. It should then be reduced to 0.1 W/g (initial product weight) in the final stages of drying to avoid charring of the fruit pieces. The best microwave programme tested lead to 20% water content with just 1% losses due to charring, but the results allow to conclude that charring could be completely reduced by switching off microwave energy altogether after 1.5 h and then finish off drying with higher air temperatures. The use of low air temperatures (30-50 °C) is advantageous with microwave energy in the first stages of drying as it limits the peaks of specific energy absorption, but it slows down drying towards the end probably because of a too low point of equilibrium (saturation humidity of air). Microwave energy did not significantly influence the drying process towards the end, although drying rates showed a "memory effect", that is, drying rates in processes with the same conditions after a given time depended on the conditions up to that point. © 2011 Elsevier Ltd. All rights reserved.
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| 20. |
- Dahlenborg, Hanna, et al.
(författare)
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Effect of particle size in chocolate shell on oil migration and fat bloom development
- 2015
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 146, s. 172-181
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Tidskriftsartikel (refereegranskat)abstract
- The effects of chocolate shell particle size were investigated by means of its influence on rate of oil migration and fat bloom development. The particle size of the non-fat particles in the chocolate, i.e. sugar and cocoa particles was varied between 15, 22 and 40 mu m. A novel set of analytical techniques was used and by combining migration results with surface topology results clear differences could be observed between the samples. At 23 degrees C storage the samples with a particle size of 15 mu m showed higher rate of oil migration and, further, the earliest development of fat bloom at the surface. This could be observed both macroscopically and microscopically. Thus, it appears as a larger specific surface area of the nonfat particles facilitates migration of filling oil, possibly due to a more heterogeneous and coarser crystal network with higher permeability. Molecular diffusion cannot explain the level of oil migration observed and, thus, convective flow is assumed to be an important contribution in addition to the molecular diffusion. (C) 2014 Elsevier Ltd. All rights reserved.
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| 21. |
- Dalvi-Isfahan, Mohsen, et al.
(författare)
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Review on identification, underlying mechanisms and evaluation of freezing damage
- 2019
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Ingår i: Journal of Food Engineering. - : Elsevier Ltd. - 0260-8774 .- 1873-5770. ; 255, s. 50-60
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Tidskriftsartikel (refereegranskat)abstract
- Although freezing is known as the best method of food preservation, physical and chemical changes that occur to the cellular structure during processing and storage may damage the quality of food products. Most freeze damages are associated with ice crystal morphology (size, number, shape and distribution) which in turn affects the microstructure of the frozen food. Therefore, the evaluation of frozen food microstructure provides opportunities for monitoring the ice crystal morphology and also identifies freeze damage at cellular level which can be linked with the final quality of frozen food products. In this review, the most important physical damages that occur during freezing and storage of food matrices are described. In addition, methods for evaluating and observing the morphology of ice crystals and microstructure of frozen food stuffs are comprehensively discussed. An understanding of the freeze damage and their relationship with ice crystal morphology can contribute to the improvement of the freezing process as well as to the frozen product quality.
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| 22. |
- Dalvi-Isfahan, Mohsen, et al.
(författare)
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Review on the control of ice nucleation by ultrasound waves, electric and magnetic fields
- 2017
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 195, s. 222-234
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Tidskriftsartikel (refereegranskat)abstract
- Freezing is the most popular and widely used food preservation method of the modern times. The freezing process of food matrices is related to their high water content and its metamorphoses into ice on cooling. The final quality of the frozen product is highly depended on the ice crystal morphology because it can cause irreversible damage on the microstructure of the food matrix. Supercooling and ice nucleation temperature need to be controlled both in suppressing and inducing the solidification to improve technological processes such as freeze drying, freeze concentration, cryopreservation, ice formation and cold-energy storage both in food industry and domestic preservation. However, the mechanism of freezing is not yet well known and it is affected by several factors. Several emerging technologies have been recently proposed for ice nucleation control during freezing. This review article is focused on the alternative freezing methods such as ultrasound waves, magnetic, electric, and electromagnetic field assisted freezing. In addition, the properties, mechanism of action and possible applications of electrofreezing are extensively discussed.
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| 23. |
- Erdogdu, S. Belgin, et al.
(författare)
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Experimental determination of penetration depths of various spice commodities (black pepper seeds, paprika powder and oregano leaves) under infrared radiation
- 2015
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 161, s. 75-81
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Tidskriftsartikel (refereegranskat)abstract
- During infrared processing, transmitted energy is attenuated exponentially with penetration distance, and its intensity is gradually lost while passing through absorbing or scattering media. Penetration depth is a complex function of chemical composition of a food product, its physico-chemical state and physical properties and wavelength spectrum of energy source. Knowing penetration depth leads to better designing commercial sterilization processes for food products like spices. Therefore, the objective of this study was to determine penetration depth of various spices (paprika powder, black pepper and oregano) as a function of water activity under infrared processing conditions. For this purpose, spice samples were prepared at various water activity (aw) levels, and heat flux measurements were carried out to determine the penetration depth. Penetration depth was determined to increase with increasing aw for black pepper seeds and paprika powder while there was no significant change for oregano leaves as a function of aw. Knowing penetration depth is important to design an effective infra-red processing system and an important issue for surface pasteurization processes since infrared radiation effects on microbial inactivation decrease with sample thickness
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| 24. |
- Fritzson, Anna, 1977, et al.
(författare)
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Efficient energy use in a slaughter and meat processing plant-opportunities for process integration
- 2006
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 76:4, s. 594-604
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, process integration methods are used to investigate the potential to decrease the energy usage in the slaughtering and meat processing industry. Above ambient temperatures, heating of water with different target temperatures is a large heat demand in a plant, while at subambient temperatures the refrigeration plant needs almost all of the shaftwork used at the site. Interaction between, on one hand, energy demands above ambient temperature and, on the other, cooling needs below ambient temperature can take place with freezing compressors or heat pumps. By using process integration methods above and below ambient temperatures, potentials for saving both shaftwork and external heat demand in food plants can be identified. A case study at a modern plant illustrates that even though many energy-saving measures have been taken there is still a technical potential for saving 30% of the external heat demand and more than 10% of the shaftwork used in the plant. The economic potential for the savings is dependent on the conditions at the plant.
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| 25. |
- Fritzson, Anna, 1977, et al.
(författare)
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Energy efficiency in the slaughter and meat processing industry-opportunities for improvements in future energy markets
- 2006
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 77:4, s. 792-802
-
Tidskriftsartikel (refereegranskat)abstract
- In the study presented in this paper different energy efficiency measures that can be carried out in a slaughter and meat processing (SMP) plant were evaluated both in terms of economy and CO2 emission reduction for four different future energy market developments. It was found that it is economically interesting to invest in an increased heat exchanger network or heat pumps in the fictitious non-integrated plants studied and that between 5% and 35% of the total CO2 emissions can be saved. The most cost effective way of reducing CO2 emissions was found to be switching fuel from heavy fuel oil to natural gas or wood chips. For the studied plants that are already heat integrated it was shown that investing in a new heat pump can be economically interesting and can reduce CO2 emissions. The profitability of investing in a combined heat and power (CHP) unit for the SMP plants was also investigated and found to be smaller than extended heat recovery or new heat pumps in the studied plants. However, the payback period for CHP units installed at an ecocyclic industrial park, consisting of an SMP plant and for example a Swedish dairy, was found to be short enough to be interesting. © 2005 Elsevier Ltd. All rights reserved.
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| 26. |
- Funebo, Tomas, et al.
(författare)
-
Microwave-assisted air dehydration of apple and mushroom
- 1998
-
Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 38:3, s. 353-367
-
Tidskriftsartikel (refereegranskat)abstract
- Microwave-assisted hot-air dehydration of apple and mushroom was performed with low-power microwave energy. The purpose of the investigation was to compare hot-air drying and microwave-assisted hot-air drying. The air velocity, the microwave output power and the air temperature were the variables in the experiments. The microwave energy was supplied by either microwave applicators with transverse magnetic (TM) modes as dominant modes, or by a multimode cavity microwave oven. The quality parameters were rehydration capacity, bulk density, and colour. Low air velocity caused a browning of the products and a minimum air velocity of 1 m/s was identified. It was possible to reduce the drying time by a factor of two for apple and a factor of four for mushroom by using microwave-assisted hot-air drying. Rehydration capacity was 20-25% better for TM applicator-dried apples and mushrooms than for multimode cavity dried ones. © 1999 Elsevier Science Limited. All rights reserved.
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| 27. |
- Gogou, Eleni, et al.
(författare)
-
Effect of water activity on the thermal stability of Thermomyces lanuginosus xylanases for process time temperature integration
- 2010
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 100:4, s. 649-655
-
Tidskriftsartikel (refereegranskat)abstract
- Three strains of the thermophilic fungus Thermomyces lanuginosus were used to produce β-xylanases. The thermal stability of these xylanases at low levels of water activity was studied. Isothermal inactivation experiments were performed in the temperature range of 100–130 °C. Reduction of water activity to 0.63 and as low as 0.13 had a drastic effect on the observed D and z-values. At water activity of 0.13 the D120 °C and z-values of the three xylanases ranged from 20.4 to 37.6 min and from 23.3 to 28.9 °C, respectively. The applicability of the developed kinetic models was tested under time–temperature profiles representative of typical thermal processes. The developed systems can be applied as time–temperature integrators (TTI) at this high thermal processing range. Calculations demonstrated that the use of a triple xylanase TTI system could provide acceptable F-values prediction for z-values lower than the achieved range.
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| 28. |
- Guo, Zhiming, et al.
(författare)
-
Quantitative detection of apple watercore and soluble solids content by near infrared transmittance spectroscopy
- 2020
-
Ingår i: Journal of Food Engineering. - : ELSEVIER SCI LTD. - 0260-8774 .- 1873-5770. ; 279
-
Tidskriftsartikel (refereegranskat)abstract
- Near-infrared (NIR) spectroscopy as an emerging analytical technique was used for the first time to quantitatively detect the watercore degree and soluble solids content (SSC) in apple. To reduce the data processing time and meet the needs of practical application, the variable selection methods including synergy interval (SI), successive projections algorithm (SPA), genetic algorithm (GA) and competitive adaptive reweighted sampling (CARS) were used to identify the characteristic variables and simplify the models. The spectral variables closely related to the apple bioactive components were used for the establishment of the partial least squares (PLS) models. The predictive correlation coefficient (R-p), root mean square error of prediction (RMSEP), and residual predictive deviation (RPD) were used to estimate the performance of the models. The CARS-PLS models displayed the best prediction performance using 600-1000 nm spectra with R-p, RMSEP, and RPD values of 0.9562, 1.340% and 3.720 for apple watercore degree; 0.9808, 0.327 (o)Bx and 4.845 for apple SSC, respectively. These results demonstrate the potential of the NIR transmittance spectroscopy technology for quantitative detection of SSC and watercore degree in apple fruit.
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| 29. |
- Hakansson, Andreas, et al.
(författare)
-
Extent and mechanism of coalescence in rotor-stator mixer food-emulsion emulsification
- 2016
-
Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 175, s. 127-135
-
Tidskriftsartikel (refereegranskat)abstract
- Food-emulsions often have high volume fractions of dispersed phase and are thus expected to show coalescence during emulsification, however, food-emulsion coalescence is difficult to measure in homogenizer equipment. This study experimentally estimates the rates of fragmentation and coalescence in a high viscosity and high volume fraction model emulsion subjected to pilot-scale rotor-stator mixing in order to quantify the relative effect of coalescence and discuss the mechanism of coalescence during batch processing of high-fat emulsion foods. Rate constants of both processes are estimated using a previously suggested method relying on parameter fitting from the dynamic evolution of the total number of emulsion drops (Hounslow and Ni, 2004). The results show substantial coalescence taking place. Scaling of rates with respect to rotor tip speed suggests coalescence and fragmentation controlled by a turbulent viscous mechanism. (C) 2015 Elsevier Ltd. All rights reserved.
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| 30. |
- Henningsson, Marcus, et al.
(författare)
-
CFD simulation and ERT visualization of the displacement of yoghurt by water on industrial scale
- 2007
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 80:1, s. 166-175
-
Tidskriftsartikel (refereegranskat)abstract
- The rinsing step, in which yoghurt is displaced by water, was monitored in a dairy plant using electrical resistance tomography (ERT), with a new hygienic design of the ERT sensors. The same displacement situation was simulated using computational fluid dynamics (CFD) and showed good agreement with the ERT measurements. CFD was also used to study how different properties, such as flow velocity, wall slip and the rheological properties of the yoghurt, could change the effectiveness of rinsing. (c) 2006 Elsevier Ltd. All rights reserved.
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| 31. |
- Henningsson, Marcus, et al.
(författare)
-
Plug flow of yoghurt in piping as determined by cross-correlated dual-plane electrical resistance tomography
- 2006
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 76:2, s. 163-168
-
Tidskriftsartikel (refereegranskat)abstract
- Cross-correlation of electrical resistance tomography (ERT) was used to determine the velocity profile of yoghurt in a pipe of industrial dimensions. In viscometry, at shear rates higher than 10 s(-1), the yoghurt followed the power law model with a K-value of 3.7 Pa s(n) and an n-value of 0.37. In pipe flow, however, within the tested mean velocity range of 0.05-0.25 m s(-1), the yoghurt appeared to flow as a plug. The local velocity was constant from the centreline to within 3 mm of the tube wall, which corresponds to the resolution of the ERT method. (c) 2005 Elsevier Ltd. All rights reserved.
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| 32. |
- Henningsson, Marcus, et al.
(författare)
-
Sensor fusion a a tool to monitor dynamic dairy processes
- 2006
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 76:2, s. 154-162
-
Tidskriftsartikel (refereegranskat)abstract
- A system for monitoring milk and fat concentration in a dynamic milk/water system by fusing information from several sensors was investigated. Standard instrumentation for food production was used, the sensors were a conductivity meter, a density meter and an optical instrument used to measure backscattered light. The system was applied to a dynamic mixing situation. Prediction error did not exceed 2% in the milk concentration and 0.1% fat in the total fat concentration. The applicability of the sensor fusion approach in field conditions was demonstrated by mounting the sensors in a dairy plant and monitoring the start-up of a pasteurizer.
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| 33. |
- Herting, Gunilla, et al.
(författare)
-
Corrosion-induced release of chromium and iron from ferritic stainless steel grade AISI 430 in simulated food contact
- 2008
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 87:2, s. 291-300
-
Tidskriftsartikel (refereegranskat)abstract
- Ferritic stainless steel grade AISI 430 with three different surface finishes, glossy, line and abraded has been evaluated regarding changes in metal release rates and corresponding changes in surface composition when immersed in 3 vol% acetic acid at two different temperatures, 40 degrees C for ten days and 100 degrees C during three consecutive immersions of 30 min each. Test parameter intervals were set by one of the very few regulatory texts for metal release in food applications, the Italian law text D.M. 21-03-1973, Art. 37. The metal release process was found to be strongly dependent on surface area to solution volume ratio where a specific surface finish would be within the allowed limit, 0.1 mg Cr L-1 for the lowest ratio, 0.5 cm, but exceeded for the highest ratio, 2 cm(-1). The amount of released metal increased with increasing temperature and increasing surface roughness (surface finish). Generated data show the regulatory text insufficient and to provide large degrees of freedom, specifically in terms of defining the surface area to solution volume ratio and the acidic cleaning of test vessels, essential parameters to enable reproducible and relevant migration data.
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| 34. |
- Herting, Gunilla, et al.
(författare)
-
Multi-analytical investigation of stainless steel grade AISI 420 in simulated food contact
- 2009
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 93:1, s. 23-31
-
Tidskriftsartikel (refereegranskat)abstract
- Martensitic stainless steel grade AN 420 intended for cutlery knives and scissor blades has been investigated in all attempt to correlate microstructure and surface finish (polishing procedure) to metal release rates of the main alloy constituents, iron and chromium. Metallographic investigations proved the knife steel and, in particular the scissor steel to have very inhomogeneous microstructures. The knife steel contained bands of ferrite in the martensitic structure while the scissor steel revealed large amounts of tempered martensite and inclusions of manganese sulphides and silicon oxides. Samples of different surface finish were immersed in 3 vol% acetic acid at 40 degrees C from 1 to 10 days for metal release testing. simulating food contact. The largely inhomogeneous microstructure of the scissor steel results in high and greatly varying metal release rates. despite a fairly high chromium content Of the Surface oxide. Areas of inclusions seem to act as initiation points for accelerated metal release and the forming of a surface oxide depleted in chromium, but rich in copper. The generation Of high Surface temperatures during polishing was found beneficial from a metal release perspective as a result Of the formation of a surface oxide of improved passivating properties.
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| 35. |
- Holtz, Emma, 1969, et al.
(författare)
-
The influence of dielectric and sorption properties on drying behaviour and energy efficiency during microwave convective drying of selected food and non-food inorganic materials
- 2010
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 97:2, s. 142-153
-
Tidskriftsartikel (refereegranskat)abstract
- The average energy efficiency of microwave convective drying is strongly related to drying time and thus to drying kinetics. This study investigates the energy efficiency of materials with different material properties and drying rates. Four solid, porous materials (swede, potato, bread, and lightweight concrete) were dried under the same microwave convective drying conditions. Drying behaviour, temperature development, hygroscopicity, dielectric properties, and specific energy consumption were studied. Despite differences in kinetics and product properties, the specific energy consumption (MJ/kg evaporated water) was approximately the same for all materials at intermediate to high moisture contents. When drying was pursued into the hygroscopic region, however, the specific energy consumption increased. The results indicate that a relationship between microwave penetration depth and water activity of the materials may be found. Drying of the food materials was limited by burning either due to temperature runaway in the hygroscopic region or due to development of hot spots, possibly induced by material structure.
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| 36. |
- Håkansson, Andreas
(författare)
-
Experimental methods for measuring coalescence during emulsification : a critical review
- 2016
-
Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 178, s. 47-59
-
Forskningsöversikt (refereegranskat)abstract
- Emulsification is a common process in the production in many non-solid foods. These food-emulsions often have high disperse phase volume fractions and slow emulsifier dynamics, giving rise to substantial coalescence during emulsification. Optimal design and operation of food-emulsification requires experimental methods to study how emulsification in general and coalescence in particular progresses under different conditions. Methods for coalescence quantification during emulsification has been suggested in literature but they are rarely used in food-emulsification research. This contribution offers a critical review of the different methods that have been suggested with special emphasis on their applicability to technical food-emulsification. The methods are critically compared in terms of design limitations, degree of quantification and applicability. A state-of-the-art in the form of two methods is identified and guidelines for their application are suggested. (C) 2016 Elsevier Ltd. All rights reserved.
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| 37. |
- Håkansson, Andreas, 1983-
(författare)
-
Scale-down failed : dissimilarities between high-pressure-homogenizers of different scales due to failed mechanistic matching
- 2017
-
Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 195, s. 31-39
-
Tidskriftsartikel (refereegranskat)abstract
- The high-pressure homogenizer (HPH) is used extensively in the processing of non-solid foods. Food researchers and producers use HPHs of different scales, from laboratory-scale (∼10 L/h) to the largest production-scale machines (∼50 000 L/h). Hence, the process design and interpretation of academic findings regarding industrial condition requires an understanding of differences between scales. This contribution uses theoretical calculations to compare the hydrodynamics of the different scales and interpret differences in the mechanism of drop-breakup.Results indicate substantial differences between HPHs of different scales. The laboratory-scale HPH operates in the laminar regime whereas the production-scale is in the fully turbulent regime. The smaller scale machines are also less prone to cavitation and differ in their pressure profiles. This suggest that the HPHs of different scales should be seen as principally different emulsification processes. Conclusions on the effect or functionality of a HPH can therefore not readily be translate between scales.
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| 38. |
- Jha, Piyush, et al.
(författare)
-
Benchmarking of techniques used to assess the freeze damage in potatoes
- 2019
-
Ingår i: Journal of Food Engineering. - : Elsevier Ltd. - 0260-8774 .- 1873-5770. ; 262, s. 60-74
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, benchmarking of methods used for assessing freeze damage in potatoes was carried out. Initially, the samples were frozen by subjecting them to three different temperatures (i.e. at –18 °C, − 30 °C, and at −74 °C). Then, different analytical techniques comprising of focused methods (i.e. cryo-Scanning elctron microscopy-cryo-SEM, confocal laser scanning microscopy-CLSM)and global methods (i.e. texture analysis, low field nuclear magnetic resonance (NMR), exudate loss and colour change)were used to assess the impact of the freezing treatment from the different point of view addressed by each method. As a result, each of these methods were able to distinguish significantly fresh samples from the frozen-thawed samples. Focused methods like cryo-SEM and CLSM methods could differentiate the impact of all three different protocols. Meanwhile, texture analysis (including conventional method and novel method based on a touchless laser puff firmness tester), NMR and exudate loss could only determine the quality difference between −18 °C and − 74 °C freezing conditions. Colour analysis was found as an inappropriate parameter for comparing the three freezing protocols. Among all analytical techniques, cryo-SEM provides the most authentic information about the product as the analysis is performed in frozen state, while for other techniques the product is thawed prior to analysis.
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| 39. |
- Kaunisto, Erik, et al.
(författare)
-
A thermodynamical finite element model of the fibre formation process during extrusion of high-moisture meat analogues
- 2024
-
Ingår i: Journal of Food Engineering. - : Elsevier Ltd. - 0260-8774 .- 1873-5770. ; 362
-
Tidskriftsartikel (refereegranskat)abstract
- A finite element model of spinodal decomposition in a power-law fluid in the extruder cooling die has been developed to investigate the effects of different parameters on fibre formation and alignment. The model makes use of the Cahn-Hilliard equations with a thermodynamic potential and numerical approximations to simulate local compositions in the separated state. The constitutive model is calibrated towards extrusion-relevant strain rates and temperatures by using a combination of rheometry techniques. The simulations show that the effect of decreased wall cooling has a limited effect on fibre development. Instead, decreasing the die width or increasing the die length can be used somewhat interchangeably to achieve fibre formation at the die exit. Viscosity also seemed to influence fibre formation in the outer viscous regions of the die by yielding comparably finer lamellar structures. The local composition of fibres also varied across the die, which may indicate differences in fibre consistency.
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| 40. |
- Loutfi, Amy, 1978-, et al.
(författare)
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Electronic noses for food quality : a review
- 2015
-
Ingår i: Journal of Food Engineering. - : Elsevier. - 0260-8774 .- 1873-5770. ; 144, s. 103-111
-
Forskningsöversikt (refereegranskat)abstract
- This paper provides a review of the most recent works in electronic noses used in the food industry. Focus is placed on the applications within food quality monitoring that is, meat, milk, fish, tea, coffee and wines. This paper demonstrates that there is a strong commonality between the different application area in terms of the sensors used and the data processing algorithms applied. Further, this paper provides a critical outlook on the developments needed in this field for transitioning from research platforms to industrial instruments applied in real contexts.
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| 41. |
- Malafronte, Loredana, et al.
(författare)
-
Coalescence and agglomeration of individual particles of skim milk during convective drying
- 2016
-
Ingår i: Journal of Food Engineering. - : Elsevier. - 0260-8774 .- 1873-5770. ; 175, s. 15-23
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents a methodology, which combines experiments and modelling, for investigating the coalescence and agglomeration ability of a product and to support the modelling of product properties during spray drying. Two particles were dried simultaneously and contact tests were performed along the drying time. A validated mathematical model describing the drying kinetics of milk particles was used to predict surface conditions during contact tests. Three major mechanisms were observed, coalescence, stickiness, and non-stickiness, which were related to adhesion and cohesion forces. The simulation model allowed evaluation of the surface Ohnesorge dimensionless number and surface glass transition temperature, which showed to be good parameters for predicting contact mechanisms. The model was also used to predict shell formation in drying particles. Wet and dry shell formation was simulated over the drying time, to improve understanding of observed contact behaviour.
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| 42. |
- Malafronte, Loredana, 1986, et al.
(författare)
-
Combined convective and microwave assisted drying: Experiments and modelling
- 2012
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 112:4, s. 304-312
-
Tidskriftsartikel (refereegranskat)abstract
- The drying process is largely used in many different industrial applications, such as treatment of foods,production of cosmetics and pharmaceuticals, manufacturing of paper, wood and building materials,polymers and so on.Physical and mathematical models can constitute useful tools to establish the influence of the main process variables on the final product quality, in order to apply an effective production control. In this work, simulation model was developed to describe combined convective/microwave assisted drying. In particular, a multi-physics approach was applied to take into account heat and two mass balances (for liquid water and for water vapor) and Maxwell’s equations to describe electromagnetic field propagation.Potato matrix was selected as food material; a waveguide with a rectangular cross section, equipped with a hot air circulator device, was used as microwave applicator. The proposed model was found able to describe the process, being thus a useful tool for design and management of the process itself.
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| 43. |
- Malafronte, Loredana, et al.
(författare)
-
Estimation of the effective diffusion coefficient of water in skim milk during single-drop drying
- 2015
-
Ingår i: Journal of Food Engineering. - : Elsevier Ltd. - 0260-8774 .- 1873-5770. ; 147:C, s. 111-119
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new approach combining experimental methodology and modelling, developed to evaluate the effective diffusivity of water in skim milk during drying over a full range of water contents and temperatures. This parameter is important to support modelling of spray-drying processes and designing of equipment. The effective diffusion coefficient is evaluated using a combination of nuclear magnetic resonance (NMR) and parameter estimation. NMR is used to determine the temperature dependence and parameter estimation is used to estimate the water concentration dependence of the effective diffusivity of water in skim milk (0.90 on total weight basis) during drying by comparing the experimental data obtained using a suspended-drop method, which allows the recording of weight and temperature changes during drying, with the results of a distributed heat and mass transport model. The results indicate that the free-volume theory best predicts the dependence of the effective diffusion coefficient of water in skim milk. A mathematical correlation of effective diffusivity over a full range of water contents and temperatures (from 50 to 90 °C) was obtained and experimentally successfully validated for concentrated skim milk (0.70 on total weight basis).
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| 44. |
- Malafronte, Loredana, 1986, et al.
(författare)
-
Exploring drying kinetics and morphology of commercial dairy powders
- 2015
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 158, s. 58-65
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the effect of the initial composition of a liquid feed on the spray drying process and morphology of powders is important in order to reduce the time and costs for process design, and ensure the desired properties of the final product. In this work, seven commercial dairy products with different fat content were selected. The effect of initial composition on drying time during single drop experiments was studied. The morphology of powder particles and the influence of morphology changes on the drying rate were investigated in order to assess the effect of fat content on the effective diffusivity of water in dairy products. Results show that fat content influences drying time and morphology of powder particles. The higher the fat content the longer the drying time and particles appear to be less shrivelled. Changes in morphology and the drying rate seem to be related. Two falling drying periods were observed for most of the products. During the first period the drops shrink spherically, while during the second period shrivelling occurs. The effective diffusivity of water shows that high fat contents lead to a lower diffusivity of water in the products.
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| 45. |
- Mazinanian, Neda, et al.
(författare)
-
Comparison of the influence of citric acid and acetic acid as simulant for acidic food on the release of alloy constituents from stainless steel AISI 201
- 2015
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 145, s. 51-63
-
Tidskriftsartikel (refereegranskat)abstract
- To ensure the safety of metals and alloys intended for food contact, a new European test protocol (CoE protocol) using citric acid as a food simulant was published in 2013. This study investigated the influence of citric acid and exposure conditions on the metal release from an austenitic manganese stainless steel (AISI 201). Exposures in 5 g/L citric acid resulted in significantly lower metal releases compared with specific release limits set by the CoE protocol. 5 g/L (0.3 vol%) citric acid was more aggressive than 3 vol% acetic acid (Italian protocol) due to higher metal complexation. Studies on abraded surfaces revealed that most metals were released during the first 0.5 h of exposure due to surface passivation. Surface abrasion, increased temperature (40-100 degrees C), increased surface area to solution volume ratio (0.25-2 cm(2)/mL) and increased citric acid concentration (0-21 g/L) all resulted in increased released metal quantities.
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| 46. |
- Munkevik, Per, et al.
(författare)
-
A computer vision system for appearance-based descriptive sensory evaluation of meals
- 2007
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 78:1, s. 246-256
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a complete machine vision system for automatic descriptive sensory evaluation of meals. A human sensory panel first developed a set of 72 sensory attributes describing the appearance of a prototypical meal, and then evaluated the intensities of those attributes on a data set of 58 images of example meals. This data was then used both to train and validate the performance of the artificial system. This system covers all stages of image analysis from pre-processing to pattern recognition, including novel techniques for enhancing the segmentation of meal components and extracting image features that mimic the attributes developed by the panel. Artificial neural networks were used to learn the mapping from image features to attribute intensity values. The results showed that the new system was extremely good in learning and reproducing the opinion of the human sensory experts, achieving almost the same performance as the panel members themselves. (c) 2005 Elsevier Ltd. All rights reserved.
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| 47. |
- Olsson, E E M, et al.
(författare)
-
Flow and heat transfer from multiple slot air jets impinging on circular cylinders
- 2005
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 67:3, s. 273-280
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents flow and heat transfer predictions of multiple slot air jets impinging on circular cylinders using CFD (computational fluid dynamics). The distribution of Nusselt numbers around the cylinders for different Reynolds numbers (23,000-100,000), distances between the jets, and openings between them was determined for two and three jets and compared to simulations of a single jet. The flow characteristics and the heat transfer distribution around the cylinders are found to be dependent on the distance and the opening between the jets. The interaction between two jets is found to be most advantageous. The heat transfer increases for higher Reynolds number in general; for two jets the heat transfer in the stagnation point is Nu(s) = 0.20Re(0.68). For three jets, the heat transfer distribution is different on the outer cylinders, as compared to the cylinder in the centre. (C) 2004 Elsevier Ltd. All rights reserved.
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| 48. |
- Olsson, E E M, et al.
(författare)
-
Heat transfer from a slot air jet impinging on a circular cylinder
- 2004
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 63:4, s. 393-401
-
Tidskriftsartikel (refereegranskat)abstract
- Heat transfer from a slot air jet impinging on a cylinder shaped food product placed on a solid surface in a semi-confined area as investigated using computational fluid dynamics (CFD). Simulations of a cylinder in cross flow with the k-epsilon, k-omega and SST models in CFX 5.5 were compared with measurements in the literature. The SST model predicts the heat transfer better than the other models and is therefore used in this study. The distribution of the local Nusselt numbers around the cylinder for various Reynolds numbers (23,000-100,000), jet-to-cylinder distances, H/d (2-8), and cylinder curvature, d/D (0.29-1.14) was determined. The results show that the local Nusselt numbers varies around the surface of the cylinder and that the average Nusselt number and the stagnation point Nusselt number increases with increasing Reynolds numbers and surface curvature but has little dependency on the jet-to-cylinder distance. The result is Nu(m) = 0.14Re(0.65)(H/d)(-0.077)(d/D)(0.32) and Nu(s) = 0.46Re(0.59)(H/d)(-0.026)(d/D)(0.32). (C) 2003 Elsevier Ltd. All rights reserved.
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| 49. |
- Penha, Frederico Marques, et al.
(författare)
-
Evaluation of permeation of macauba oil and n-hexane mixtures through polymeric commercial membranes subjected to different pre-treatments
- 2015
-
Ingår i: Journal of Food Engineering. - : ELSEVIER SCI LTD. - 0260-8774 .- 1873-5770. ; 155, s. 79-86
-
Tidskriftsartikel (refereegranskat)abstract
- Macauba is a Brazilian palm tree with high edible oil productivity and of great interest to many applications. In the oil extraction process, solvent recovery is one point of major concern, due to its high energy consumption and oil quality losses. Those drawbacks can be partially overcome by integration of membrane technology to the usual solvent distillation step. The present work tested four ultrafiltration (UF) and one nanofiltration (NF) membrane (Microdyn-Nadir) on the solvent recovery of synthetic mixtures of macauba oil and n-hexane. Membranes were pre-treated before use with different solvents in specific time lengths, according to preliminary studies. The membrane performance was evaluated by permeate flux and oil retention. Macauba (pulp and kernel) oil was evaluated by determinations of acidity, peroxide value and fatty acid profile. Membranes showed usual flux behaviour, compatible with other studies concerning oil/solvent mixtures permeation, although its values were quite above the expected. Best results for retention (>30%) are related to the membranes with lower molar mass cut-off (MMCO), and the best balance between permeate flux and oil retention was found for the NF membrane (12.4 g m(-2) h(-1), 34.7%).
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| 50. |
- Pereira, N.R., et al.
(författare)
-
Effect of microwave power, air velocity and temperature on the final drying of osmotically dehydrated bananas
- 2007
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 81:1, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a study of the final stage of microwave-hot air drying of osmotically dehydrated bananas, focusing on the effects of microwave power, air temperature and air velocity on drying kinetics and product quality, evaluated in terms of colour, apparent volume and porosity. The drying process was divided into three periods: phase I (760 W; 2 kgmoisture/kgdry matter); phase II (380 W; 0.67 kgmoisture/kgdry matter); and phase III (0 W, 76 W, 150 W or 230 W up to the final sample moisture of 0.17 kgwater/kgd m). Three conditions for the hot air were tested: 50 °C and 3.3 m/s; 70 °C and 3.3 m/s; 70 °C and 5.7 m/s. The results show that increasing the microwave power in phase III increased the drying rate, thus making the drying time shorter. However, higher microwave power also caused temperature runaway leading to charring on the dried product. Air flow cools the product surface and improves product quality by reducing charring. © 2006 Elsevier Ltd. All rights reserved.
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