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.

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.

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.

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 μm. 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 °C storage the samples with a particle size of 15 μm 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 non-fat 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.

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.

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.

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

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. © 2005 Elsevier Ltd. All rights reserved.

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.

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.

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.

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. © 2006 Elsevier Ltd. All rights reserved.

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 sn 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. © 2005 Elsevier Ltd. All rights reserved.

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. © 2005 Elsevier Ltd. All rights reserved.

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.

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. 

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).

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).

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.

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.

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.

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. © 2005 Elsevier Ltd. All rights reserved.

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 Nus = 0.20Re0.68. For three jets, the heat transfer distribution is different on the outer cylinders, as compared to the cylinder in the centre. © 2004 Elsevier Ltd. All rights reserved.

Heat transfer from a slot air jet impinging on a cylinder shaped food product placed on a solid surface in a semi-confined area was investigated using computational fluid dynamics (CFD). Simulations of a cylinder in cross flow with the k-?, k-? 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 Num=0.14Re0.65(H/d) -0.077(d/D)0.32 and Nus=0.46Re 0.59(H/d)-0.026(d/D)0.32. © 2003 Elsevier Ltd. All rights reserved.

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.

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.

In the present work, faba bean protein (FBP) films plasticized with glycerol and reinforced with different amounts (2.5, 5.0, 7.5 and 10% by weight of FBP) of lignin extracted from pine cones (PL) have been obtained by solution casting. The results obtained showed an elongation at break of 111.7% with the addition of 5% PL to the FBP film, which represents an increase of 107% compared to the FBP control film. On the other hand, it was observed by thermogravimetric analysis (TGA) that the incorporation of lignin improved the thermal stability of the FBP film, leading to an increase in the protein degradation temperature, being this increase higher in the sample film reinforced with 10% PL. The barrier properties of the FBP films were also affected by the presence of lignin, leading to a decrease in water vapor permeability (WVP) in comparison to the unreinforced film. The results show that the sample reinforced with 2.5% PL had the lowest WVP value, with a reduction of 25% compared to the control film. Chemical analysis by Fourier transform infrared spectroscopy (FTIR) confirmed the formation of intramolecular interactions between lignin and proteins which, together with the inherent hydrophobicity of lignin, resulted in a decrease of the moisture content in the films reinforced with PL. This research work has allowed the development of biobased and biodegradable films with attractive properties that could be of potential use in sectors such as packaging. © 2022 The Authors

Digital colour imaging (DCI) was applied in this study as a novel approach for assessing the mixture quality of binary food powder mixes. Three different binary powder mixes with different coloured ingredients [salt, paprika, black pepper and onion] were investigated using a commercially available system called DigiEye. The coordinates of CIELAB colour space were used to describe the colour of the samples. The sample colour variance was used as a measure of mixture quality. The results showed that DCI has potential for assessing the mixture quality of binary food powder mixes, provided that colour difference between the powders can be measured. The ability to assess mixture quality decreases as the colour difference between the components in the mix decreases. Furthermore, scale of scrutiny and composition also influence the capability of the method.

This work studied the effect of composition of powders and water content on mixture quality (MQ) of three binary powder mixtures with good (salt/paprika or salt/sugar) or poor mixing (salt/oregano) behaviour. The mixing behaviour was assessed using coefficient of variation. Results showed that mixture composition did not influence the MQ of sugar/salt and paprika/salt within 20-80% salt content range but it did influence the MQ of oregano/salt with a progressive dis-improvement in MQ with higher oregano content and also for low concentrations of 1% salt. Water content did have an effect on mixing behaviour. When paprika with high water activity (aw) was mixed with salt, the time required to reach good MQ was longer because of the increased cohesiveness and when oregano with high aw was mixed with salt it displayed improved MQ because salt particles were able to stick onto the larger oregano particles and reduced segregation.

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.

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.

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.

Infrared radiation (IR) was explored as a technique for decontaminating paprika powder. The effect of water activity (aw) and IR heat flux on paprika temperature and water loss were measured during near- or medium-IR heating. Paprika was evaluated in terms of colour, aw, natural flora, and inoculated Bacillus cereus spores. Surface temperatures were considerably higher than temperatures inside the powder, especially at low aw; greater differences were observed with medium- than with near-IR. Surface darkening was observed, though the overall colour was not considerably affected. IR effectively removed water from paprika, especially at aw 0.5 and 0.8, resulting in unsatisfactory spore reduction. However, at aw 0.8, the load of the natural flora was reduced (P < 0.05). In aw 0.96 powder, areas with high remaining aw displayed a reduction >6 log10 CFU/g for B. cereus (P < 0.05). In addition, no microbial counts of the natural background flora were observed in the paprika. © 2007 Elsevier Ltd. All rights reserved.

A process to decontaminate paprika powder using variable near-infrared (IR) radiation was tested using a closed sample holder allowing water to be retained in the powder. The reduction in the concentration of Bacillus cereus spores and changes in water activity (aw) and colour were measured during IR heating. High heat flux was applied initially to heat the powder rapidly to the desired temperature, followed by low heat flux to maintain the temperature for a given time. The water activity (aw) value of the powder could be maintained within the bulk of the closed sample, but the surface aw value decreased during heating. Due to carotenoid sensitivity to temperature, surface and overall colour values declined, though remaining acceptable values of medium red and red, respectively. For powder with an aw value of 0.88 heated to 95-100 °C, the load of B. cereus spores was reduced by 4.5 log10 CFU/g within 6 min; the final spore concentration remained approximately 2 log10 CFU/g due to tailing. Reducing pH to 4.0 from 4.5 did not significantly affect the reduction of the B. cereus spore concentration. © 2008 Elsevier Ltd. All rights reserved.

The effect of major chocolate ingredients (sugar, cocoa particles and lecithin), in combination with the two pre-crystallization techniques, seeding and non-seeding, was investigated with respect to the kinetics of cocoa butter crystallisation and the resulting microstructure. Confocal laser scanning microscopy (CLSM) was used to monitor microstructural evolution under dynamic thermal conditions. DSC measurements and image analysis were also applied in order to quantify the impacts of processing and formulation on microstructure. All ingredients and pre-crystallisation techniques considered proved to have a large impact on fat crystallisation kinetics and the resulting microstructure. Seeded samples tended to form multiple nucleation sites, inducing rapid growth of a crystal network. The non-seeded samples showed an altering structure, with some domains developing large spherical crystals while in other domains a more heterogeneous microstructure resulted. Lecithin showed a remarkable impact on crystallisation kinetics in both the seeded and non-seeded samples. For the seeded samples, the effect was most noteworthy in samples containing cocoa butter and sugar, where lecithin significantly reduced the induction time. In the absence of seeds, lecithin itself acted as the nucleation site for fat crystallisation. © 2010 Elsevier Ltd. All rights reserved.

Dark chocolate microstructures with different structure densities, i.e., close-packing of the fat crystal lattice, and homogeneity i.e., evenness and connectivity of the fat crystal network, were created by ?VI- seeding or conventional pre-crystallization with various degrees of temper and were evaluated with respect to storage stability. The structure characterization was conducted by measuring the strength of the cocoa butter crystal network with traction tests combined with DSC melting curves. Subsequent storage stability was evaluated with DigiEye technique for fat bloom development and gravimetrical techniques for fat/moisture migration. The two pre-crystallization processes generated significantly different structures and storage stability. Well-tempered ?VI-seeding resulted in a dense and homogenous chocolate structure directly after solidification, which was optimal in order to retard fat bloom and fat migration. However, a too high structure density generated heterogeneous structures with reduced ability to withstand fat bloom. A lower structure density exhibited optimal resistance against moisture migration.

To increase the utilization of side-streams from the food industry more investigations of multiple protein systems could be beneficial, complementary to the extensive studies available on single sourced protein isolates. Here, high moisture content protein-rich side streams were investigated in single screw extrusion. Vegetable protein mixtures comprising potato protein, oat protein and wheat bran were considered. Potato starch and potato fibers were used as structuring agents. Microstructurally, all compositions were dominated by protein aggregates. The structural agents enhanced the interconnected starch phase and/or additionally introduced fiber aggregates, with little apparent influence on the protein aggregates size and distribution. The moisture content was found to exert a dominant influence on the shear viscosity of the compositions. In addition, a saturation behavior of the power law parameters over 45% moisture content was apparent in the presence of the structural agents. An improved knowledge of industrial side-streams processability could increase their use in novel food products and exploited to create products with improved nutritional profiles.

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.

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.

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.

Different viscosity models were developed to describe the viscosity of unprocessed fruit and vegetable purees under dynamic conditions. Temperature hysteresis cycles were carried out for three purees with different structural characteristics (tomato, carrot, and broccoli), with heating and cooling phases from 10 to 80°C with isothermal (holding) phases at 10, 30, 60 or 80°C. The apparent viscosity was measured continuously with a rotational rheometer and the data was analyzed with time-independent and time-dependent models (quantifying rheopexy, thixotropy, or both). The results revealed clear thixotropic behavior in tomato puree, attributed to shearing effects, and rheopectic in broccoli puree, attributed to gel formation at the higher temperatures. Although carrot puree data from the isothermal periods could be quantified satisfactorily with no time dependency, analysis of the nonisothermal periods proved that rheopectic effects also needed to be included.

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.

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.

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.

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.

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.