| 1. |
- Carvalho, Irene, et al.
(författare)
-
From diets to foods: Using linear programming to formulate a nutritious, minimum-cost porridge mix for children aged 1 to 2 years
- 2015
-
Ingår i: Food and Nutrition Bulletin. - : SAGE Publications. - 0379-5721 .- 1564-8265. ; 36:1, s. 75-85
-
Tidskriftsartikel (refereegranskat)abstract
- Background. Linear programming has been used extensively as a tool for nutritional recommendations. Extending the methodology to food formulation presents new challenges, since not all combinations of nutritious ingredients will produce an acceptable food. Furthermore, it would help in implementation and in ensuring the feasibility of the suggested recommendations. Objective. To extend the previously used linear programming methodology from diet optimization to food formulation using consistency constraints. In addition, to exemplify usability using the case of a porridge mix formulation for emergency situations in rural Mozambique. Methods. The linear programming method was extended with a consistency constraint based on previously published empirical studies on swelling of starch in soft porridges. The new method was exemplified using the formulation of a nutritious, minimum-cost porridge mix for children aged 1 to 2 years for use as a complete relief food, based primarily on local ingredients, in rural Mozambique. Results. A nutritious porridge fulfilling the consistency constraints was found; however, the minimum cost was unfeasible with local ingredients only. This illustrates the challenges in formulating nutritious yet economically feasible foods from local ingredients. The high cost was caused by the high cost of mineral-rich foods. A nutritious, low-cost porridge that fulfills the consistency constraints was obtained by including supplements of zinc and calcium salts as ingredients. Conclusions. The optimizations were successful in fulfilling all constraints and provided a feasible porridge, showing that the extended constrained linear programming methodology provides a systematic tool for designing nutritious foods.
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| 2. |
- Chalermchat, Yongyut, et al.
(författare)
-
Effect of pulsed electric field pretreatment on solid-liquid expression from potato tissue
- 2005
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 71:2, s. 164-169
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of pulsed electric field (PEF) pretreatment on solid-liquid expression from potato tissue was studied on individual parenchyma tissue samples for different PEF intensities, varying relative deformations and deformation rates. The yield increased with relative deformation. The yield at any given relative deformation increased with increased PEF intensity and decreased deformation rates. The compressive force was reduced by a factor of 5 when pressing potatoes pretreated with electric field strength of 0.68 kV/cm and duration of 1 ms, at a relative deformation of 0.5 and a deformation rate of 0.1 mm/min. (c) 2004 Elsevier Ltd. All rights reserved.
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| 3. |
- Chalermchat, Yongyut, et al.
(författare)
-
Electropermeabilization of apple tissue: Effect of cell size, cell size distribution and cell orientation
- 2010
-
Ingår i: Biosystems Engineering. - : Elsevier BV. - 1537-5110. ; 105:3, s. 357-366
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the anisotropy of apple tissue and the orientation of applied electric field on electropermeabilization was investigated. Different tissue regions were sampled to perform a series of experiments. The tissue was viewed under the microscope to study cell size, shape and orientation. In a parallel experiment, cylindrical samples of tissue were subjected to pulsed electric fields and the change in electrical conductivity was measured by the voltage-current method. The measured electrical conductivity during pulsing was then converted into a permeability index which defined the relative change in electrical conductivity compared to the electrical conductivity of frozen/thawed tissue that served as a reference of completely damaged tissue. Electrical impedance was also measured to monitor the tissue changes as affected by pulsed electric fields. The results showed that elongated cells taken from the inner region of the apple parenchyma, responded to the electric fields in different ways. Fields of lower intensity were required to permeabilize these cells when the fields were applied parallel to the longest axis of the cells. Other field orientations required greater applied electric fields to permeabilize the cells. No field orientation dependence was observed for round cells that belonged to the outer region of the apple parenchyma. A condition in which a high degree of permeabilization during pulsing and very small change after pulsing were observed could be obtained at an applied field intensity of 900 V cm(-1). Thus reversible electroporation took place. (C) 2009 IAgrE. Published by Elsevier Ltd. All rights reserved.
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| 4. |
- Chalermchat, Yongyut, et al.
(författare)
-
Enhancement of solid-liquid expression by pulsed electric field pretreatment: Study on potato
- 2004
-
Ingår i: CHISA 2004 - 16th International Congress of Chemical and Process Engineering. - 8086059405 ; , s. 11377-11382
-
Konferensbidrag (refereegranskat)abstract
- The effect of pulsed electric field (PEF) pretreatment on solid-liquid expression from potato tissue was studied on individual parenchyma tissue samples for different PEF intensities, varying deformations and deformation rates. The yield increased with deformation. The yield at constant deformation increased with increased PEF intensity and decreased deformation rates. The compressive force was reduced by a factor of up to 5 when pressing PEF-pretreated potatoes at low deformation rate.
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| 5. |
- Chalermchat, Yongyut, et al.
(författare)
-
Pulsed electric field treatment for solid-liquid extraction of red beetroot pigment: mathematical modelling of mass transfer
- 2004
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 64:2, s. 229-236
-
Tidskriftsartikel (refereegranskat)abstract
- The extraction of red pigment and conductive matters from individual red beet tissue slices following pulsed electric field pretreatment of different durations was compared with a two dimensional bimodal Fickian diffusion model. The process appeared to be governed by two apparent diffusion coefficients, one slow and one fast. The values of these coefficients were independent of the duration of treatment, but the yield associated with each coefficient varied. Following the treatment of longest duration and treatment by freezing and thawing of the tissue, the yield from the faster diffusion coefficient accounted completely for the mass transport. The faster apparent diffusion coefficient was 2-5 times smaller than the diffusion coefficients in dilute solution. (C) 2003 Elsevier Ltd. All rights reserved.
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| 6. |
- Chambal, Borges, et al.
(författare)
-
Edible proteins from coconut milk press cake; one step alkaline extraction and characterization by electrophoresis and mass spectrometry
- 2012
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969. ; 47:2, s. 146-151
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Tidskriftsartikel (refereegranskat)abstract
- Coconut milk press cake, the spent endosperm left over after the extraction of coconut milk, was utilized to extract additional protein under alkaline conditions. The maximum protein yield was observed at 50 degrees C and pH 11 and corresponded to total endosperm protein yield of 71%, favourably comparable to yields of more complex extractions. The extract was characterized by amino acid analysis and 1D SDS-PAGE, 2D electrophoresis and MS MS spectroscopy. Coconut milk and insoluble milk sediment from the same individual nuts were also analyzed. The alkaline extract reproducibly differed from the other fractions and from those reported by others in amino acid content as seen in Principal Component Analysis, and had in particular higher threonine content The peptide found in the alkaline extract but with no counterpart in coconut milk or its sediment showed IP (approximate to 5) and mass (approximate to 40 kDa) and matched partially glutelin from oil palm. (c) 2011 Elsevier Ltd. All rights reserved.
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| 7. |
- Chambale, Borges, et al.
(författare)
-
Coconut Press Cake Alkaline Extract—Protein Solubility and Emulsification Properties
- 2013
-
Ingår i: Food and Nutrition Sciences. - 2157-9458. ; 4:9B, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- The solubility and the emulsification properties of a crude freeze dried alkaline protein extract (APE), 30% protein, obtained from coconut milk press cake by one step extraction at pH 11, were characterized at pH 2 to 11, and the cream and subnatant fractions of the emulsion studied by SDS-PAGE electrophoresis. The protein solubility followed U profile, showing a minimum at pH 3 to 4, close to but not identical to reported iso-electric points of 4 - 5 for many coconut protein fractions. The extract showed good capacity to form oil-in-water emulsion outside the low solubility pH range. The bands that appeared to play a role in the emulsification were found at 32 and 42 kDa in SDS-PAGE electrophoresis, but the most predominant absorbed band was at 23 kDa.
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| 8. |
- Chambale, Borges, et al.
(författare)
-
Heat Induced Gels from Coconut Press Cake Proteins
- 2014
-
Ingår i: Food and Nutrition Sciences. - : Scientific Research Publishing, Inc.. - 2157-9458 .- 2157-944X. ; 5:6, s. 562-570
-
Tidskriftsartikel (refereegranskat)abstract
- Freeze-dried coconut press cake powder (CPP), 43% w/w protein, was used to investigate the heat-induced gelation by heating in rheometer to 75℃ in a wide range of pH values, from 4 to 9. Low strain oscillatory method applied the measure visco-elastic propertieson 15% w/w CPP. The gel strength was also assessed by a texture analyzer. SDS-PAGE electrophoresis was conducted to identify the proteins evolved in the gel network structure and the gel micro-structure was also evaluated. At low pH, the CPP proteins formed soft (elastic modulus <100 Pa) particulate gels prone to syneresis, with aggregate size of the order of 4.2 micrometers. In the alkaline region, homogenous gels were induced by heating. Gel strength started to increase dramatically from 64℃ to 67℃, for pH 9 and pH 8 respectively, reaching the maximum gel elastic modulus over 1000 Pa at pH 9. The SDS-PAGE showed that the polypeptide sub-unities at 24, 32 - 34 and 53 kDa were the most prominent in gelation.
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| 9. |
- De Carvalho, Irene Stuart Torrié, et al.
(författare)
-
From diets to foods : using linear programming to formulate a nutritious, minimum-cost porridge mix for children aged 1 to 2 years
- 2015
-
Ingår i: Food and Nutrition Bulletin. - 0379-5721 .- 1564-8265. ; 36:1, s. 75-86
-
Tidskriftsartikel (refereegranskat)abstract
- Background. Linear programming has been used extensively as a tool for nutritional recommendations. Extending the methodology to food formulation presents new challenges, since not all combinations of nutritious ingredients will produce an acceptable food. Furthermore, it would help in implementation and in ensuring the feasibility of the suggested recommendations.Objective. To extend the previously used linear programming methodology from diet optimization to food formulation using consistency constraints. In addition, to exemplify usability using the case of a porridge mix formulation for emergency situations in rural Mozambique.Methods. The linear programming method was extended with a consistency constraint based on previously published empirical studies on swelling of starch in soft porridges. The new method was exemplified using the formulation of a nutritious, minimum-cost porridge mix for children aged 1 to 2 years for use as a complete relief food, based primarily on local ingredients, in rural Mozambique.Results. A nutritious porridge fulfilling the consistency constraints was found; however, the minimum cost was unfeasible with local ingredients only. This illustrates the challenges in formulating nutritious yet economically feasible foods from local ingredients. The high cost was caused by the high cost of mineral-rich foods. A nutritious, low-cost porridge that fulfills the consistency constraints was obtained by including supplements of zinc and calcium salts as ingredients.Conclusions. The optimizations were successful in fulfilling all constraints and provided a feasible porridge, showing that the extended constrained linear programming methodology provides a systematic tool for designing nutritious foods.
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| 10. |
- Dejmek, Petr, et al.
(författare)
-
Discussion session on food gels
- 2006
-
Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 20:4, s. 446-447
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 11. |
- Dejmek, Petr, et al.
(författare)
-
Relationship between the electrical and rheological properties of potato tuber tissue after various forms of processing
- 2002
-
Ingår i: Bioscience, Biotechnology and Biochemistry. - : Oxford University Press (OUP). - 1347-6947 .- 0916-8451. ; 66:6, s. 1218-1223
-
Tidskriftsartikel (refereegranskat)abstract
- The impedance at frequencies of 1-1000 kHz and dynamic bending storage modulus measured by the vibrating reed method were compared for potato tuber tissue, which had been processed by various methods. Raw potato tuber tissue strips were either heated for 30 min up to 100°C or frozen-thawed. Some samples were osmotically dehydrated in a mannitol solution up to a concentration of 0.7 mol/l. The electrical reactance correlated well with the storage modulus of heated or frozen-thawed potato tissues, but not with the storage modulus of the mannitol-treated tissue. The storage modulus appeared to be strongly dependent on the turgor pressure of the cells which was drastically decreased by the heating, freezing-thawing, and osmotic treatments. The electrical properties reflect the cell integrity, and a large difference was observed between the change in impedance after heating or freezing-thawing, and that after the osmotic treatment. A significant change in the electric properties was also observed for a starch suspension at the gelatinization temperature. However, the contribution due to gelatinization did not appear to play an important role in the change of electrical properties of potato tissue by heating.
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| 12. |
- Dejmek, Petr, et al.
(författare)
-
The syneresis of rennet curd
- 2004
-
Ingår i: Cheese: Chemistry, Physics, and Microbiology. - 0122636538
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- A review. Gels formed from milk by renneting or acidification under quiescent conditions may subsequently show syneresis, i.e., expel liq. (whey), because the gel (curd) contracts. In making cheese from renneted or acidified milk, syneresis is an essential step. Consequently, it is useful to understand and quant. describe syneresis as a function of milk properties and process conditions, particularly when new methods or process steps are introduced in cheesemaking.
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| 13. |
- Dymek, Katarzyna, et al.
(författare)
-
Effect of pulsed electric field on the germination of barley seeds
- 2012
-
Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 47:1, s. 161-166
-
Tidskriftsartikel (refereegranskat)abstract
- This study explores metabolic responses of germinating barley seeds upon the application of pulsed electric fields (PEE). Malting barley seeds were steeped in aerated water for 24 h and PEF-treated at varying voltages (0 (control), 110, 160, 240, 320, 400 and 480 V). The seeds were then allowed to finish germination in saturated air. It is shown that exposure of germinating barley to PEE affects radicle emergence without significantly affecting the seeds gross metabolic activity, as quantified by isothermal calorimetry. An exploration of protein 2-DE profiles of both the embryo and the starchy endosperm showed that, at the studied time scale, no significant changes were found in proteins present at concentrations higher than the detection limit. However, western blotting demonstrated that a-amylase concentration decreases in the PEF-treated seeds. (C) 2011 Elsevier Ltd. All rights reserved.
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| 14. |
- Dymek, Katarzyna, et al.
(författare)
-
Influence of Pulsed Electric Field Protocols on the Reversible Permeabilization of Rucola Leaves
- 2014
-
Ingår i: Food and Bioprocess Technology. - : Springer Science and Business Media LLC. - 1935-5149 .- 1935-5130. ; 7:3, s. 761-773
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Tidskriftsartikel (refereegranskat)abstract
- Reversible electropermeabilization of plant tissues with heterogeneous structure represents a technological challenge as the response of the different structures within the same specimen to the application of electric field may differ due to different cell sizes, extracellular space configurations, and electrical properties. The influence of five different pulsed electric field protocols with different pulse polarity, number of pulses (25, 50, 75, 100, 250, and 500), and intervals between pulses (no intervals and 1- and 2-ms intervals) on the reversible permeabilization of rucola (Eruca sativa) leaves was investigated. The electric field intensity was 600 V/cm. Electrical resistance of the bulk tissue was measured before and after electroporation, and propidium iodide was used to analyze the electroporation at the surface of the leaf. Leaf viability was assessed from survival in storage, and cell viability was investigated with fluorescein diacetate. Results indicate that the viability of the leaves could not be predicted by measurements of electrical resistance or permeabilization levels of the leaf surface. Higher survival rate was demonstrated when applying bipolar pulses compared with monopolar pulses, but the latter proved to be more effective than bipolar pulses for permeabilizing the surface of the leaves. Longer intervals between bipolar pulses resulted in increased viability preservation, while the number of electroporated cells on the leaf surface was comparable for all tested protocols.
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| 15. |
- Dymek, Katarzyna, et al.
(författare)
-
Influence of vacuum impregnation and pulsed electric field on the freezing temperature and ice propagation rates of spinach leaves
- 2015
-
Ingår i: LWT - Food Science and Technology. - : Elsevier BV. - 0023-6438. ; 64:1, s. 497-502
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Tidskriftsartikel (refereegranskat)abstract
- Efforts are currently directed towards improving the quality of sensitive tissues of fruits and vegetables after freezing and thawing. One of the methods under investigation is the combination of vacuum impregnation (VI) with cryoprotectants and pulsed electric field (PEF), applied to the plant tissue prior exposure to freezing. The influence of these processes on the freezing temperature and ice propagation rate of spinach baby leaves are here studied. Leaves impregnated with trehalose, sucrose, glucose and mannitol exhibited significantly lower ice propagation rate and higher freezing temperatures in comparison to non-treated controls. Leaves subjected to PEF also showed increased freezing temperatures compared to the non-treated leaves; however the ice propagation rate was not influenced by PEF for the cryoprotectants used in the study, except for leaves impregnated with trehalose, where it was significantly increased and water, where it was significantly decreased. The combination of VI and PEF resulted in comparable freezing temperatures and ice propagation rates as the leaves subjected only to VI. (C) 2015 Elsevier Ltd. All rights reserved.
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| 16. |
- Dymek, Katarzyna, et al.
(författare)
-
Investigation of the metabolic consequences of impregnating spinach leaves with trehalose and applying a pulsed electric field.
- 2016
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 112, s. 153-157
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Tidskriftsartikel (refereegranskat)abstract
- The impregnation of leafy vegetables with cryoprotectants using a combination of vacuum impregnation (VI) and pulsed electric fields (PEF) has been proposed by our research group as a method of improving their freezing tolerance and consequently their general quality after thawing. In this study, we have investigated the metabolic consequences of the combination of these unit operations on spinach. The vacuum impregnated spinach leaves showed a drastic decrease in the porosity of the extracellular space. However, at maximum weight gain, randomly located air pockets remained, which may account for oxygen-consuming pathways in the cells being active after VI. The metabolic activity of the impregnated leaves showed a drastic increase that was further enhanced by the application of PEF to the impregnated tissue. Impregnating the leaves with trehalose by VI led to a significant accumulation of trehalose-6-phosphate (T6P), however, this was not further enhanced by PEF. It is suggested that the accumulation of T6P in the leaves may increase metabolic activity, and increase tissue resistance to abiotic stress.
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| 17. |
- Dymek, Katarzyna, et al.
(författare)
-
Modeling electroporation of the non-treated and vacuum impregnated heterogeneous tissue of spinach leaves
- 2015
-
Ingår i: Innovative Food Science & Emerging Technologies. - : Elsevier BV. - 1466-8564. ; 29, s. 55-64
-
Tidskriftsartikel (refereegranskat)abstract
- Uniform electroporation of the heterogeneous structure of spinach leaf cross section is a technological challenge that is addressed in this investigation. Three dimensional models were created with cells arranged in specific tissue types, considering a leaf with its air fraction and a leaf where the air fraction was replaced by a solution of known properties using vacuum impregnation. The models were validated before electroporation, in the frequency domain, where alternating voltage and current signal at frequencies from 20 Hz to I MHz were used to measure conductivity of the tissue. They were also validated through measurements of current during electroporation when a single 250 mu s rectangular pulse with amplitudes ranging from 50 to 500 V was applied. Model validations show that both the frequency dependent conductivity and electroporation are well predicted. The importance of the wax layer and stomata in the model is thoroughly discussed. Industrial relevance: Our aim was to investigate electroporation of the spinach leaf by developing a model which would enable us to meet the technological challenge of achieving uniform electroporation in a highly heterogeneous structure in the context of a process aimed at improving freezing stability of plant foods. Pulsed electric field treatment may be used to introduce the cryoprotectant molecules into the cells, and hence improve the structure and properties of frozen food plants. (C) 2014 Elsevier Ltd. All rights reserved.
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| 18. |
- Edén, Jonas, et al.
(författare)
-
The influence of serum phase on the whipping time of unhomogenised cream
- 2015
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 49, s. 56-61
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to investigate how the properties of the serum phase, including ionic strength, protein content and specific milk salts, influence the whipping time of unhomogenised cream. This study showed that decreasing the protein content of the serum phase in cream resulted in shorter whipping time. However, addition of UF permeate to both deproteinated and proteinated creams indicated that other components than the protein fraction also influence whipping time of unhomogenised cream. Increasing the ionic strength by addition of NaCl, KCl and CaCl2 decreased whipping time, with the largest effect being found for CaCl2. A further increase in ionic strength by addition of NaCl and KCl resulted in an unfavourable effect on whipping time, whereas a pronounced effect, with shorter whipping times, was found for addition of CaCl2. (C) 2015 Elsevier Ltd. All rights reserved.
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| 19. |
- Elofsson, Ulla, et al.
(författare)
-
Heat induced aggregation of b-lactoglobulin studied by dynamic light scattering
- 1996
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946 .- 1879-0143. ; 6:4, s. 343-357
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Tidskriftsartikel (refereegranskat)abstract
- The in situ heat-induced aggregation of commercial β-lactoglobulin as such, or after further purification, was followed to a z-average hydrodynamic diameter of 15–20 nm at 59–63 °C by dynamic light scattering. In this temperature range, measurable increase of hydrodynamic diameter occurred after an apparent lag period, which was strongly dependent on heating temperature, pH and initial protein concentration. The changes in time scale of the aggregation process agreed with changes in amount of unfolded β-lactoglobulin, assuming a two-state model of the denaturation. The pH dependence reflected the midpoint unfolding temperature and not the sulphydryl group reactivity, suggesting that this reactivity was not rate limiting in the aggregation. The aggregation process was modelled numerically with FuchsSmoluchowski kinetics.
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| 20. |
-
Engineering aspects of food emulsification and homogenization
- 2015
-
Samlingsverk (redaktörskap) (refereegranskat)abstract
- Emulsions are found in a wide variety of food products, pharmaceuticals, paints, and cosmetics, thus emulsification is a truly multidisciplinary phenomenon. Therefore understanding of the process must evolve from the combination of (at least) three different scientific specializations. Engineering Aspects of Food Emulsification and Homogenization describes the state-of-the-art technology and brings together aspects from physical chemistry, fluid mechanics, and chemical engineering. The book explores the unit operations used in emulsification and homogenization processes, using fundamental theory from different fields to discuss design and function of different emulsification techniques. This book summarizes the present understanding of the involved physical–chemical processes as well as specific information about the limits and possibilities for the different types of emulsifying equipment. It covers colloidal chemistry and engineering aspects of emulsification and discusses high-energy and low-energy emulsification methods. The chapters highlight low-energy emulsification processes such as membrane emulsification that are now industrially feasible. Dramatically more energy-efficient processes are being developed, and this book clarifies their present limitations, such us scale-up and achievable droplet sizes. The present literature on emulsification is, to a large degree, influenced by the division between physical chemistry, fluid dynamics, and chemical engineering. Written by experts drawn from academia and industry, this book brings those areas together to provide a comprehensive resource that gives a deeper understanding of emulsification and homogenization in food product development.
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| 21. |
- Erdogdu, Ferruh, et al.
(författare)
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Determination of heat transfer coefficient during high pressure frying of potatoes
- 2010
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 96:4, s. 528-532
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Tidskriftsartikel (refereegranskat)abstract
- Besides traditional atmospheric frying, high pressure (super-atmospheric) frying might be an alternative approach to the frying of food products. In this study, convective heat transfer coefficient during atmospheric and high pressure frying was compared. For this purpose, a pressure cooker was modified to allow the immersion of a sample into frying oil under pressure and temperature measurement of sample and oil. Heat transfer coefficient versus frying time was determined on potato slabs using changes of total mass of the experimental set-up. At the pressure of 2 bar, the results showed an almost doubled heat transfer coefficient compared to the atmospheric pressure frying. The knowledge of heat transfer coefficient during pressure frying is expected to allow accurate determination of temperature distribution and hence the kinetic calculations to lead to development of an alternative frying process. All rights reserved. (C) 2009 Elsevier Ltd.
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| 22. |
- Fincan, Mustafa, et al.
(författare)
-
Effect of osmotis pretratment and pulsed electric field on the viscoelastic properties of potato tissue.
- 2003
-
Ingår i: Journal of Food Engineering. - 0260-8774. ; 59:2-3, s. 169-175
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Tidskriftsartikel (refereegranskat)abstract
- Compression stress relaxation of potato tissue exposed to pulsed electric field (PEF) treatment, with or without osmotic pretreatment, was measured and modelled with five parameter generalised Maxwell model. The changes in viscoelastic model coefficients were quantified as a response to applied field strength, pulse length, and pulse number and were correlated with conductivity changes. Using the same approach, additional effects of different osmotic treatments along with constant PEF treatment were also studied. As measured by the post-PEF conductivity, the residual elasticity was the parameter most affected at lower levels of PEF treatment. At high PEF levels, the longer of the relaxation times dropped from 10 to 2–3 s range. Maximal PEF treatment had a similar effect to 0.7 M hyper-osmotic treatment, implying that the effect of PEF on relaxation behaviour was dominated by loss of turgor. Neither hypo-osmotic nor hyper-osmotic pretreatment appeared to interact with the PEF treatment.
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| 23. |
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| 24. |
- Fincan, Mustafa, et al.
(författare)
-
In situ visualization of the effect of a pulsed electric field on plant tissue
- 2002
-
Ingår i: Journal of Food Engineering. - 0260-8774. ; 55:3, s. 223-230
-
Tidskriftsartikel (refereegranskat)abstract
- A new method was developed for in situ visualization of changes related to electropermeabilization of plant tissue. Onion epidermis stained with neutral red was subjected to a pulsed electric field (PEF), and serial images were captured by a camera connected to a stercomicroscope. Sample resistance was recorded simultaneously. Above a threshold level of a field strength of 0.35 kV/cm, it was possible to distinguish the individual permeabilized cells by their colour. Over 90-95% of the PEF-induced colour changes occurred during the first 2-3 min after the electric pulse and the rest after some 20 min. The size and rate of the observed changes were correlated with the severity of PEF, and were further influenced by the pH and conductivity of the solution used in mounting the epidermis, the sampling location on the onion epidermis, and cell size and number. The final conductivity increase was directly proportional to the number of permeabilized cells. Permeabilization was not randomly distributed but occurred along preferential paths connecting the electrodes. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 25. |
- Fincan, Mustafa, et al.
(författare)
-
Pulsed electric field treatment for solid-liquid extraction of red beetroot pigment
- 2004
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 64:3, s. 381-388
-
Tidskriftsartikel (refereegranskat)abstract
- Extractability of red pigment from red beetroot was investigated using pulsed electric field (PEF) treated tissue in a solid-liquid extraction process. Thin disks of the tissue were subjected to PEF at different intensities and, 3-4 min after the treatment, the release of red pigment and ionic species into an isotonic solution was measured in situ using a spectrophotometer and a conductivity meter. The highest degree of extraction achieved with PEF was compared with that of freezing and mechanical pressing. Subjected to 270 rectangular pulses of 10 Vs at 1 kV/cm field strength, with an energy consumption of 7 kJ/kg, the samples released about 90%,) of total red colouring and ionic content following I h aqueous extraction. The increase in tissue electric conductivity after PEF treatment correlated approximately linearly with the extraction yield of red pigment and ionic species only up to an extraction level of 60-800%. No differential permeabilization of the intracellular components was found. Higher degree of variation of the extractability of pigment and ionic species at intermediate PEF treatments was interpreted as related to non-homogenous permeabilization of the tissue due to cell size. (C) 2003 Elsevier Ltd. All rights reserved.
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| 26. |
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| 27. |
- Folkenberg, Ditte M., et al.
(författare)
-
Interactions between EPS-producing Streptococcus thermophilus strains in mixed yoghurt cultures
- 2006
-
Ingår i: Journal of Dairy Research. - 0022-0299. ; 73:4, s. 385-393
-
Tidskriftsartikel (refereegranskat)abstract
- Mixed cultures of different EPS-producing Streptococcus thermophilus strains in combination with a Lactobacillus delbrueckii subsp. bulgaricus strain with negligible EPS-production were used for yoghurt production. The yoghurt texture was characterised with respect to sensory, rheological and microstructural properties and the EPS-concentrations were determined. The cultures resulted in yoghurts with highly different texture properties, and positive interactions between certain Streptococcus thermophilus strains were observed. The underlying properties of yoghurt texture are multidimensional, but a number of microstructural characteristics were apparent in the yoghurts with the highest mouth thickness, creaminess and viscosity. A strong protein network, not too dense and with medium size pores containing EPS, seems associated with these properties. The presence of capsular polysaccharides (CPS) also appeared to be beneficial as did a combination of FPS types, which were distributed differently in the protein network (in serum pores, respectively in association with protein). Obviously, a certain concentration of FPS must be present to provide for these effects on yoghurt texture, but other factors than concentration per se seem more important.
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| 28. |
- Folkenberg, D M, et al.
(författare)
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Relation between sensory texture properties and exopolysaccharide distribution in set and in stirred yoghurts produced with different starter cultures
- 2005
-
Ingår i: Journal of Texture Studies. - : Wiley. - 0022-4901 .- 1745-4603. ; 36:2, s. 174-189
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Tidskriftsartikel (refereegranskat)abstract
- Set yoghurts produced with seven different exopolysaccharide-producing starter cultures were subjected to sensory texture profiling including texture evaluation before and after a stirring procedure carried out by trained assessors. The microstructure of four selected yoghurts was investigated by confocal laser scanning microscopy with special focus on the distribution of exopolysaccharides (EPS) in the protein network. Two different types of microstructures were observed, one in which EPS were associated with the protein network and another where EPS appeared to be incompatible with the protein; as a consequence, the EPS were situated in the void spaces in the protein network. The latter yoghurts were less ropy and had higher serum separation than the yoghurts where EPS were associated with the protein, and they exhibited a significant increase in mouth thickness as a result of stirring. Yoghurts in which the EPS were associated with protein had high ropiness, low serum separation and appeared more resistant to stirring. The nature of EPS-protein interactions is extremely important for the textural effects of EPS in fermented milk products, and such interactions depend on the specific starter culture used.
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| 29. |
- Folkenberg, D M, et al.
(författare)
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Sensory and rheological screening of exopolysaccharide producing strains of bacterial yoghurt cultures
- 2006
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 16:2, s. 111-118
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Tidskriftsartikel (refereegranskat)abstract
- Yoghurts were produced with 24 different cultures differing in their ability to produce exopolysaccharides (EPS). Rheological and sensory analyses showed large differences in texture properties in the yoghurt samples. EPS production was found to have a major effect oil the texture properties, but varying textures within the EPS +/- groups were also found. Yoghurts fermented with EPS-producing cultures showed increased mouth thickness and ropiness and tended to be creamier than yoghurts without these cultures; in contrast, these yoghurts had the lowest syneresis and highest gel firmness (initial gel strength before the yoghurt was subjected to shear). Correlations between rheological parameters and sensory texture attributes included G* correlating with gel firmness, while viscosity measured at 241 s(-1) correlated with mouth thickness. An interesting viscometry relationship was found between ropiness and hysteresis loop area.
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| 30. |
- Gomez, Federico, et al.
(författare)
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Exploring metabolic responses of potato tissue induced by electric pulses
- 2008
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Ingår i: Food Biophysics. - : Springer Science and Business Media LLC. - 1557-1866 .- 1557-1858.
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated the metabolic responses of potato tissue induced by pulsed electric field (PEF). Potato tissue was subjected to field strengths ranging from 30 to 500 V/cm, with a single rectangular pulse of 10 μs, 100 μs, or 1 ms. Metabolic responses were monitored using isothermal calorimetry, changes on electrical resistance during the delivery of the pulse, as well as impedance measurements. Our results show that the metabolic response involves oxygen consuming pathways as well as other unidentified events that are shown to be insensitive to metabolic inhibitors such as KCN and sodium azide. The metabolic response is strongly dependent on pulsing conditions and is independent of the total permeabilization achieved by the pulse. Evidence shows that calorimetry is a simple and powerful method for exploring conditions for metabolic stimulation, providing information on metabolic responses that can not be obtained from electrical measurements. This study set the basis for further investigations on defense-related consequences of PEF-induced stress.
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| 31. |
- Gomez, Federico, et al.
(författare)
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Metabolomic evaluation of pulsed electric field-induced stress on potato tissue
- 2009
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 230:3, s. 469-479
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Tidskriftsartikel (refereegranskat)abstract
- Metabolite profiling was used to characterize stress responses of potato tissue subjected to reversible electroporation, providing insights on how potato tissue responds to a physical stimulus such as pulsed electric fields (PEF), which is an artificial stress. Wounded potato tissue was subjected to field strengths ranging from 200 to 400 V/cm, with a single rectangular pulse of 1 ms. Electroporation was demonstrated by propidium iodide staining of the cell nucleae. Metabolic profiling of data obtained through GC/TOF-MS and UPLC/TOF-MS complemented with orthogonal projections to latent structures clustering analysis showed that 24 h after the application of PEF, potato metabolism shows PEF-specific responses characterized by the changes in the hexose pool that may involve starch and ascorbic acid degradation.
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| 32. |
- Gomez, Federico, et al.
(författare)
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Pulsed electric field reduces the permeability of potato cell wall
- 2008
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Ingår i: Bioelectromagnetics. - : Wiley. - 0197-8462 .- 1521-186X. ; 29:4, s. 296-301
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the application of pulsed electric fields to potato tissue on the diffusion of the fluorescent dye FMI-43 through the cell wall was studied. Potato tissue was subjected to field strengths ranging from 30 to 500 V/cm, with one 1 ms rectangular pulse, before application of FM1-43 and microscopic examination. Our results show a slower diffusion of FM1-43 in the electropulsed tissue when compared with that in the non-pulsed tissue, suggesting that the electric field decreased the cell wall permeability. This is a fast response that is already detected within 30 s after the delivery of the electric field. This response was mimicked by exogenous H2O2 and blocked by sodium azide, an inhibitor of the production of H2O2 by peroxidases.
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| 33. |
- Gutierrez, G., et al.
(författare)
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Production of vegetable oil in milk emulsions using membrane emulsification
- 2009
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Ingår i: Desalination. - : Elsevier BV. - 0011-9164 .- 1873-4464. ; 245:1-3, s. 631-638
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Konferensbidrag (refereegranskat)abstract
- The production of emulsions using milk as the continuous phase has a number of applications of interest from the food industry's point of view. In addition, producing an emulsion with a narrow drop size distribution is interesting since their increased stability could avoid Oswald ripening and creaming. Membrane emulsification is a novel technique which helps to obtain a narrower distribution compared to other emulsification techniques such as homogenizers or ultrasound. Moreover the use of membrane emulsification may reduce the energy cost. The food industry is interested in reducing the use of food additives, both to save money and increase consumer acceptance. Therefore the aim of this work was to investigate the use of the intrinsic emulsifying capacity of milk proteins to act as stabilizers for oil droplets produced by membrane emulsification. Using tubular SPG membrane (4.8 mu m pore diameter) in recirculation mode, at dispersed phase fluxes of either 5 L/hm(2) or 50 L/hm(2), a stable final emulsion of 30% w/w oil was obtained. The fat globule size distribution was more bimodal at higher oil concentrations and at the higher flux.
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| 34. |
- Helstad, Kristina, et al.
(författare)
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Liquid droplet-like behaviour of whole casein aggregates adsorbed on graphite studied by nanoindentation with AFM
- 2007
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 21:5-6, s. 726-738
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Tidskriftsartikel (refereegranskat)abstract
- AFM measurements in the force volume mode were performed over the total penetration depth for different positions on casein aggregates adsorbed to a graphite surface in a liquid cell. The stiffness of the force curves was correlated to indentation depths, layer depth and lateral position within the aggregates with the aim of arriving at a credible explanation for the shapes of the force curves. The commonly used Hertz-based models did not fit the experimental data. The ratio between the height and diameter of the adsorbed casein aggregates was found to be linear, suggesting surface energy dominated liquid droplet behaviour. To investigate the possibility, numerical simulations were performed using the Surface Evolver, an interactive finite element program for the study of surfaces shaped by surface tension and other energies. Simulated force curves were in good agreement with experimental findings, both with respect to slope as a function of indentation as well as describing the variation with indentation position on the aggregate due to interfacial and geometric effects. By comparing the simulated force curves to the measurement data it was found that there would have been an interfacial energy equivalent to 10 mJ/m2.
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| 35. |
- Helstad, Kristina, et al.
(författare)
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Nanorheological properties of casein
- 2005
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Ingår i: Food Colloids: Interactions, Microstructure and Processing. - : The Royal Society of Chemistry. - 0260-6291. - 9780854046386 ; :298, s. 218-229
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Konferensbidrag (refereegranskat)
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| 36. |
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| 37. |
- Henningsson, Marcus, et al.
(författare)
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CFD simulation and ERT visualization of the displacement of yoghurt by water on industrial scale
- 2007
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 80:1, s. 166-175
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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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| 38. |
- Henningsson, Marcus, et al.
(författare)
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Plug flow of yoghurt in piping as determined by cross-correlated dual-plane electrical resistance tomography
- 2006
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 76:2, s. 163-168
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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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| 39. |
- Henningsson, Marcus, et al.
(författare)
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Sensor fusion a a tool to monitor dynamic dairy processes
- 2006
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 76:2, s. 154-162
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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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| 40. |
- Henningsson, Marcus, et al.
(författare)
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The electrical conductivity of milk : The effect of dilution and temperature
- 2005
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Ingår i: International journal of food properties. - 1094-2912 .- 1532-2386. ; 8:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- The electrical conductivity of milk at various dilutions was measured at different temperatures from 2 to 70°C. The results showed that dilution has only a small influence on the temperature dependence of conductivity. A simple power-law model predicts that the conductivity is proportional to the milk concentration to the power of 0.84 and a two-term model describes the temperature dependency. The overall model has a standard deviation of 0.0067 mS cm-1, which corresponds approximately to 0.1% milk at 2°C and 0.07% milk at 70°C. It was further shown that for less than about 25% milk in water Kohlrausch's law and the Debye-Hückel-Onsager theory can be used to describe the relationship between the concentration, temperature, and conductivity using a representative limiting molar conductivity of milk ions of 75 mS cm2 mol-1. Copyright © Taylor & Francis Inc.
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| 41. |
- Håkansson, Andreas, et al.
(författare)
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Droplet Breakup in High-Pressure Homogenizers
- 2015. - 1st
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Ingår i: Engineering Aspects of Food Emulsification and Homogenization. - Boca Raton : CRC Press. - 9780429073236 - 9781466580435 ; , s. 125-148
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Bokkapitel (refereegranskat)abstract
- In this chapter, a detailed review of the current understanding of the physical processes of droplet breakup in a high-pressure homogenizer (HPH) is presented, covering breakup mechanisms by laminar shear in the gap inlet and its boundary layers, by local turbulence in the gap exit jet, and by cavitation. Experimental evidence of the effects of homogenization pressure, Thoma number, dispersed and continuous phase viscosity, and dispersed phase volume fraction in relation to implications on dominant mechanisms of droplet breakup is also discussed.
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Larsson, M, et al.
(författare)
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Primary proteolysis studied in a cast cheese made from microfiltered milk
- 2006
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 16:6, s. 623-632
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Tidskriftsartikel (refereegranskat)abstract
- Primary proteolysis was studied in a starter-free cheese model made from microfiltered (MF) milk (19.0% casein,<0.2% whey proteins). Specificity of plasmin and chymosin activity was investigated in the pH range 5.0–6.0, by analysis of peptide composition using high-performance liquid chromatography and liquid chromatography–mass spectrometry. Hydrolysis experiments with purified caseins were performed to aid identification of peptides released by specific activities. Plasmin had no activity in cheese below pH 5.4, while its activity increased from pH 5.4 to 6.0. Chymosin activity on the Phe23–Phe24 bond of αS1-casein had an optimum pH around 5.3, while release of the bitter peptide β-casein (f193–209), effected by chymosin, was highest at pH 6.0. At pH <5.3, the specificity of chymosin on αS1-casein changed, and the peptide bond Leu20–Leu21 was cleaved at an increasing rate with decreasing pH. Demineralisation of the MF retentate generally increased proteolytic activity.
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| 46. |
- Lodaite, Kristina, et al.
(författare)
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Fusion of skim milk cheese curd grains: Development of a method to measure the fracture stress of the bonds between fused curd grains
- 2002
-
Ingår i: International Dairy Journal. - 0958-6946. ; 12:5, s. 455-461
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental technique with which to measure the fracture stress of fused curd grains, submerged in ultrafiltered milk permeate, has been developed and applied to curd grains of rennet-induced skim milk at pH 6.40 during the first 25 min of fusion. Effects of applied compressive stress within the range of 25-50 Pa, syneresis time, fusion time and tension loading rate were investigated. Fracture stress increased with applied compressive stress and fusion time. For the system investigated it was found that very small changes in applied compressive stress dramatically increased the degree of fusion. The degree of syneresis prior to fusion was found to have a large impact on the fusion rate, The rate of fusion was greater for 30 min of syneresis compared to 6 min of syneresis. A longer syneresis time, up to 60 min, did not further improve the fusion rate.
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| 47. |
- Malmgren, Bozena, et al.
(författare)
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Changes in proteins, physical stability and structure in directly heated UHT milk during storage at different temperatures
- 2017
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946 .- 1879-0143. ; 71, s. 60-75
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Tidskriftsartikel (refereegranskat)abstract
- Changes occurring in directly heated UHT milk were studied during storage at 5, 22, 30 and 40 °C. Industrially produced UHT milk samples were analysed for changes in enzymatic activity, protein modification, destabilisation of casein micelles and relocation of milk proteins in relation to sedimentation and gel formation. Sedimentation occurred at all temperatures, and the protein composition of the sediments reflected the composition of its liquid phase; however, there was no α-lactalbumin, β-lactoglobulin or κ-casein present in sediments. Tendrils composed of β-lactoglobulin and κ-casein were seen on casein micelles after UHT treatment and grew in length prior to gelation. High degrees of lactosylation of proteins and peptides were clearly correlated with the absence of gelation and long tendrils. Gelled samples showed complete hydrolysis of intact β-casein, and limited lactosylation of β-lactoglobulin and κ-casein.
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| 48. |
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| 49. |
- Marefati, Ali, et al.
(författare)
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Fabrication of encapsulated oil powders from starch granule stabilized W/O/W Pickering emulsions by freeze-drying
- 2015
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 51, s. 261-271
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Tidskriftsartikel (refereegranskat)abstract
- The process stability of water-in-oil-in-water (W/O/W) double emulsions stabilized with food-grade OSA modified quinoa starch granules was investigated. The effect of oils with differing melting points, as well as the effect of in situ partial gelatinization of the granules, on stability of emulsions was also investigated. The physical stability and release of a tracer (carmine) from the internal aqueous phase of double emulsions were characterized after each process stage using particle size analysis, light microscopy and spectrophotometry. When liquid shea oil was used the particle sizes varied in mode of D[4,3] from 28 +/- 2 mu m for initial fresh double emulsions to 90 +/- 7 mu m for heat treated and 210 +/- 11 mu m for heat treated, freeze-dried and reconstituted emulsions. Non-heat treated emulsions collapsed on freeze-drying due to high susceptibility of liquid oil droplets towards destabilization, when the external aqueous phase is crystalized. When solid shea oil was used the mode of D[4,3] varied from 48 +/- 0 mu m in initial emulsions to 118 +/- 3 mu m for heat treated emulsions and the freeze-dried and reconstituted emulsions showed 62 +/- 3 mu m or 85 +/- 11 mu m for non-heat treated and heat treated samples respectively. Reconstituted freeze-dried emulsion retained the encapsulated marker to over 97%. Overall, application of oil phase solid at room temperature and in situ heat treatment had a positive impact on process stability towards freezing and freeze drying. The result of this study revealed the feasibility to develop food-grade oil filled powders from OSA modified starch Pickering emulsions with approximately 70 wt% oil content by freeze-drying. (C) 2015 Elsevier Ltd. All rights reserved.
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| 50. |
- Marefati, Ali, et al.
(författare)
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Freezing and freeze-drying of Pickering emulsions stabilized by starch granules
- 2013
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 436, s. 512-520
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the possibility to produce novel powder materials based on chemically modified starch granule stabilized Pickering oil-in-water (O/W) emulsions. This study also investigated the effect of partial starch gelatinization in situ, dispersed phase type (two oil types with different melting points), freezing method and thawing, and freeze-drying and rehydrating on the overall properties of the emulsions. The emulsions showed high freeze thaw stability. The results of this study demonstrated the feasibility of the production of oil containing hydrocolloid-based powders, through combination of heat treated or even non-heat treated starch Pickering emulsions and freeze-drying. The final powders comprised high weight percentage of oil (over 80%, w/w). Upon rehydration of powders, the starch stabilized oil drops were found to be only moderately affected by the process with some aggregation observed. (C) 2013 Elsevier B.V. All rights reserved.
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