| 1. |
- Malafronte, Loredana, 1986, et al.
(författare)
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Combined convective and microwave assisted drying: Experiments and modelling
- 2012
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 112:4, s. 304-312
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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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| 2. |
- Oliveira, H., et al.
(författare)
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Semi-industrial development of nutritious and healthy seafood dishes from sustainable species
- 2021
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Ingår i: Food and Chemical Toxicology. - : Elsevier Ltd. - 0278-6915 .- 1873-6351. ; 155
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to devise innovative, tailor-made, appealing, tasty and semi-industrialized dishes, using sustainable and under-utilized seafood species (bib, common dab, common carp, blue mussel and blue whiting), that can meet the specific nutritional and functional needs of children (8-10-years), pregnant women (20-40-years) and seniors (≥60-years). Hence, contests were organised among cooking schools from 6 European countries and the best recipes/dishes were reformulated, semi-industrially produced and chemically and microbiologically evaluated. The dishes intended for: (i) children and pregnant women had EPA + DHA and I levels that reached the target quantities, supporting the claim as “high in I”; and (ii) seniors were “high in protein” (24.8%-Soup_S and 34.0%-Balls_S of the energy was provided by proteins), “high in vitamin B12”, and had Na contents (≤0.4%) below the defined limit. All dishes reached the vitamin D target value. Sausages_C, Roulade_P, Fillet_P and Balls_S had a well-balanced protein/fat ratio. Roulade_P presented the highest n-3 PUFA/n-6 PUFA ratio (3.3), while Sausages_C the lowest SFA/UNS ratio (0.2). Dishes were considered safe based on different parameters (e.g. Hg-T, PBDEs, Escherichia coli). All represent dietary sources contributing to meet the reference intakes of target nutrients (33->100%), providing valuable options to overcome nutritional and functional imbalances of the three groups.
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| 3. |
- Raaholt, Birgitta
(författare)
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2 - Influence of food geometry and dielectric properties on heating performance
- 2020
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Ingår i: Development of Packaging and Products for Use in Microwave Ovens. - : Woodhead Publishing in Materials. - 9780081027134 ; , s. 73-93
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter, an introduction to microwave heating of foods and some commonly encountered phenomena in heating uniformity is given. The chapter is intended to help the reader make initial progress and to serve as a beginning for deeper understanding of microwave heating, hopefully resulting in improved heating results and well-designed products. The impact of dielectric properties as well as geometrical properties on the resulting heating is introduced.
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| 4. |
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| 5. |
- Raaholt, Birgitta, et al.
(författare)
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A tubular microwave sterilisation or pasteurisation process for pumpable foods
- 2013
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Ingår i: 14th International Conference on Microwave and High Frequency Heating, AMPERE 2013. - : Edinburgh University Press. ; , s. 80-83
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Konferensbidrag (refereegranskat)abstract
- A pilot-scale process for continuous in-flow microwave heating of pumpable foods was designed, built and evaluated for heat treatment of high-concentrated particulate foods at temperatures up to 135°C and at the microwave frequency 2450 MHz. In this work, the temperature uniformity of a particulate model soup after microwave heating is evaluated for selected goal temperatures and holding times, and the heating up time to goal temperature is investigated. Furthermore, choice of radial dimensions of the tube is discussed, as well as strategies for achieving an improved microwave heating uniformity of the product, based on calculated radial temperature profile and electromagnetic field distribution.
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| 6. |
- Raaholt, Birgitta
(författare)
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Applications of Microwave Heating of Foods
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractMicrowave heating of foods offers rapid and flexible heating both for consumer and industrial applications, with several advantages, such as reduced processing time (due to volumetric heating and reduced coming-up times (heating time required to reach the desired target temperature), selective heating, increased process flexibility and efficient heating (volumetric heating of the food does not require heating of a surrounding medium or package). However, successful installations requireknowledge in process design. Modelling could be used to accomplish this in a way that gives the desired electromagnetic field distribution. The resulting microwave heating pattern depends in a complex way on a large number of parameters, related to the food, the package as well as the oven. Among these parameters are: food dimensions and geometry, dielectric and thermo-physical properties of the food, design and geometry of the food package, placement of food components anddesign of the oven.This thesis deals with selected applications of microwave heating of foods at 2450 MHz, modelling of microwave heating of foods in a lab-scale microwave oven, and the evaluation of continuous tubular microwave heating of foods in pilot-scale, in terms of temperature uniformity in a homogeneous model food and with respect to rapidness in heating of a particulate model food and its resulting product quality. Additionally, an accurate method for determining the dielectric properties of liquids isdescribed. Dielectric properties of foods are required as input data for modelling of microwave heating, and also serve as a first basis for understanding the phenomena behind microwave heating of foods.In the food industry, process operations often require continuous processes, due to the desired high yield. This suggests a large potential for well-designed and controlled microwave continuous operations. High-temperature short-time (HTST) processing of foods could be used to achieve thermal processing as sterilisation, while exposing foods to heating for a shorter time than conventional heat treatment, with resulting minimal product degradation. It is suggested that continuous tubular microwave heating of particulate foods could offer an alternative to HTST processing for producing high-quality particulate foods with increased rapidness due to the volumetric microwave heating and the shorter coming-up times to achieve the necessary target temperature. The work presented in part of this thesis demonstrates that it is possible to achieve microwave-assisted HTST conditions in terms of continuous tubular microwave heating of a high-concentrated particulate model food product for a 12 mm tubular system at 2450 MHz. This is accomplished by combining modes that heat primarily in the centre (TM020) and in the periphery (TM120) of the tube. This process results in a more rapid and uniform heating where the product (particulates as well as the surrounding continuous phase) will reach the desired target temperature more rapidly (than in atraditional HTST system), with resulting reduced losses in product quality in terms of e.g. piece integrity. Additionally,microwave HTST processing offers product quality advantages due to reduced overheating of the continuous phase and also large process flexibility, since a wide interval of possible combinations of target temperature and holding time is accomplished in the same equipment. Moreover, combined centre and periphery heating is shown to give a more uniform temperature distribution, than periphery alone or centre alone heating could offer, in the 16 mm tubular microwave system.Furthermore, modelling of heating of foods in a microwave combination oven at 2450 MHz, in which the food is heated by combined microwave and convective heating, is described by solving for the electromagnetic fields in a model food load and then including these as a source term in a heat transfer model. Validation experiments of the numerical model showed good qualitative and quantitative agreement. Computers today are considerably faster than 10-15 years ago, which contributes to increased use of modelling tools for process design and development of optimised industrial microwave heating systems. It issuggested that this has contributed to increase the number of successful installations in food industry and will continue to support the steadily growing trend of industrial installations in the years to come.
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| 7. |
- Raaholt, Birgitta, et al.
(författare)
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Combined microwave infrared/convective baking of bread
- 2013
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Ingår i: 14th International Conference on Microwave and High Frequency Heating, AMPERE 2013. - : Edinburgh University Press. ; , s. 35-39
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Konferensbidrag (refereegranskat)abstract
- There are several advantages of industrial microwave-infrared baking of bread. Among these are: shorter process time, reduced energy consumption, less space requirement of baking equipment in the production facility and increased flexibility in production. Furthermore, the fast and efficient energy transfer due to volumetric microwave heating during baking, and due to infrared colouring of the bread, also means considerably reduced need for pre-heating, with resulting cost and time benefits. However, results are promising also when it comes to quality aspects. In this paper, this will be exemplified for two types of bread, which are microwave baked in a continuous pilot-scale oven and then coloured in a next pilot-scale oven section by infrared waves and/or convection. The resulting bread quality is presented in terms of colour and porosity for white tin loaves, and in terms of colour for rolls with seeds. The results are compared to the corresponding quality for conventionally baked bread. The comparison shows good agreement in quality between microwave-combination baked breads and conventionally baked breads. The results are promising also in terms of advantages for the bakery industry, from energy consumption, process time and flexibility aspects. The paper also presents electromagnetic modelling results for microwave baking of tin loaves. The latter results were valuable for the understanding of more uniform microwave baking.
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| 8. |
- Raaholt, Birgitta
(författare)
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Continuous in-flow microwave processing for food preservation applications
- 2017
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Ingår i: 16th International Conference on Microwave and High Frequency Heating, AMPERE 2017.
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Konferensbidrag (refereegranskat)abstract
- A pilot-scale process for continuous in-flow microwave processing of particulate pumpable foods, designed and implemented at RISE Research Institute of Sweden [1], was studied for heat treatment of a particulate, viscous model food at high temperature conditions at 2450 MHz. In this paper, the technology will be discussed as an alternative high-temperature short-time (HTST) processing method for a high-concentrated particulate model product. The technology combines TM 020 and TM 120 microwave mode heating. The rapidness in heating the product will be illustrated for selected time-temperature conditions after tubular microwave heating. The latter corresponds to the required microbiological inactivation, for a product intended for storage at ambient conditions or cool storage, respectively. As will be exemplified, the microwave HTST system studied results in large process flexibility. Additionally, it offers advantages in product quality.
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| 9. |
- Raaholt, Birgitta, et al.
(författare)
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Continuous tubular microwave heating of homogeneous foods: evaluation of heating uniformity
- 2016
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Ingår i: The Journal of microwave power and electromagnetic energy. - London : Taylor & Francis Group. - 0832-7823. ; 50:1, s. 43-65
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Tidskriftsartikel (refereegranskat)abstract
- A pilot-scale process for continuous in-flow microwave processing of foods, designed and implemented at SP Food and Bioscience, was evaluated for heat treatment of a homogeneous model food for high-temperature short-time (HTST) conditions, at constant total input microwave power, at 2450 MHz. The microwave system has three consecutive cavities, one excited by the TM020 microwave mode that heats primarily in the tube centre, and two TM120 mode cavities that heat primarily in the tube periphery. The temperature uniformity of the homogeneous model food after microwave heating is here evaluated in terms of spatial distribution, for different set-ups of input microwave power in each cavity and for different order of the placement of the cavities, while maintaining the total input microwave power. The microwave heating uniformity is evaluated, based on measured and calculated radial temperature profiles. Combined TM020 and TM120 heating was found to result in more uniform heating by means of spatial temperature uniformity over the tube cross section. Furthermore, appropriately selected microwave power distribution between the centre and periphery heating cavities results in a stable heating profile in the studied food, that differs only about 10 °C or less between highest and lowest average values directly after microwave heating.
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| 10. |
- Raaholt, Birgitta, et al.
(författare)
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Continuous tubular microwave heating of particulate foods at high temperatures
- 2017
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Ingår i: The Journal of microwave power and electromagnetic energy. - : Informa UK Limited. - 0832-7823. ; 51:4, s. 259-285
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Tidskriftsartikel (refereegranskat)abstract
- A pilot-scale process for continuous in-flow microwave processing of particulate pumpable foods, designed and implemented at RISE Agrifood and Bioscience, was evaluated for heat treatment of a particulate, viscous model food at high-temperature conditions at 2450 MHz. The microwave system has three consecutive cavities, one excited by the TM020 microwave mode that heats primarily in the centre of the tube, and two cavities fed by TM120 modes that heat primarily in the tube periphery. In this paper, combined TM020 and TM120 tubular microwave heating is evaluated as an alternative to high-temperature short-time (HTST) processing for a high-concentrated particulate model product. Rapidness in heating of the product was evaluated after tubular microwave heating for different time-temperature conditions, corresponding to the required microbiological inactivation for a model product intended for storage at ambient conditions. Moreover, the effects on product quality of the microwave heated model soup were investigated in terms of texture, piece integrity and colour. Microstructural analysis was used to gain an understanding of the effects of heating at a microscopic scale. It was found that the microwave-assisted HTST system results in large process flexibility. Additionally, it offers advantages in product quality in terms of piece integrity and texture.
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