Thermal Food Processing

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Ohmic Heating for Food Processing 455 Electrode Electric field Electrode Electric field Alternating Power Supply Electrode Product inflow Product outflow Electrode a b c Electrodes Product outflow Product inflow Electric field FIGURE 14.7 Basic configurations for ohmic heaters: (a) batch, (b–d) continuous. Panels (b) and (c) correspond to the cross-field configuration, while panel (d) corresponds to the in-field configuration, depending on if the electric field lines are perpendicular or parallel to the direction of the flow of the food, respectively. they are spaced to account for the increase of σ with temperature. Therefore, as the product approaches the outlet of the heater, a lower value of the electric field strength is needed, and this is accomplished by increasing the spacing between each pair of electrodes. The choice of the best configuration will obviously depend on the food being processed and the objectives of the process (e.g., cooking, pasteurization, sterilization). Electrode Product outflow Product inflow Electrode Electric field d
456 Thermal Food Processing: New Technologies and Quality Issues Batch processes are typically used to cook, e.g., meat products, 70 while continuous processes are more appropriate for viscous fluids or fluids with particulates. 14.5 APPLICATIONS The OH technology provides new, high-added-value, shelf-stable products with a quality unachievable by the traditional processing technologies. The process can be used in (1) the thermal processing of high-acid food products, such as tomato-based sauces, (2) pasteurization of whole liquid eggs, 9 (3) fish pastes, and (4) on meat products processed as an alternative to the traditional smokehouse. 14.5.1 MEAT PRODUCTS The first experiments using OH in meat products were done in Finland in the 1970s, but operational difficulties led to the abortion of the project. Later on, in the 1990s, a project for cooking liver pâté and hams was carried out in France by the Meat Institute Development Association (ADIV) and Électricité de France (EDF). One OH application is the thawing process, when traditional thawing methods cannot provide high-quality products. Wang et al. 71 applied the technology to frozen meat samples, in a liquid-contact thawing method. The results demonstrated a uniform and quicker thawing process. Also, meat properties such as color and pH were not changed significantly, and the final products achieved a good thawing quality. These results demonstrate the potential uses of OH in contact thawing, especially for meat products. Although the initial batch results were very promising, the attempts to develop a prototype version for a continuous cooking process were unsuccessful. Canadian scientists 70 have been working on the ohmic cooking of meat products (sausages and ham) with promising results in batch operations. Brine-cured meat products were found to be admirably suited to OH having extremely reduced cooking times (e.g., a ham weighing 1 kg was cooked in less than 2 min). However, these flash cooking times did not reduce the bacterial load to levels that guaranteed product safety. Pasteurization had to be taken into consideration and a time–temperature profile was established. However, under these conditions, no noticeable changes were reported in the products’ taste, texture, or shelf life. 14.5.2 FRUIT AND VEGETABLE PRODUCTS Strawberry fruit jams are extremely important for the Portuguese fruit jams industry because they account for most of its sales (around 90%). The search for alternative processing technologies leading to higher-quality products is one of the main goals, and the economic viability of this technology depends on the possibility of applying it to most of the products processed by this industry. 8 In the study by Castro et al., 8 several strawberry-based products were tested by OH. The obtained results showed that for most of the products, high heating rates could be achieved, despite the significant differences of σ between the products tested. Also, the increase of the applied electric field could increase the heating rate (Figure 14.8a and b).
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Thermal Food Processing
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87. Polysaccharide Association Stru
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133. Handbook of Frozen Foods, edit
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Published in 2006 by CRC Press Tayl
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Various alternative thermal process
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Professor Sun is a fellow of the In
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Antonio Martínez Instituto de Agro
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Contents Part I: Modeling of Therma
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Chapter 17 Pressure-Assisted Therma
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1 CONTENTS Thermal Physical Propert
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Thermal Physical Properties of Food
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2 CONTENTS Heat and Mass Transfer i
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Heat and Mass Transfer in Thermal F
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74 Thermal Food Processing: New Tec
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5 CONTENTS Modeling Thermal Process
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Modeling Thermal Processing Using C
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6 CONTENTS Thermal Processing of Me
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Thermal Processing of Meat Products
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7 CONTENTS Thermal Processing of Po
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Thermal Processing of Poultry Produ
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9 CONTENTS Thermal Processing of Da
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Thermal Processing of Dairy Product
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10 CONTENTS UHT Thermal Processing
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UHT Thermal Processing of Milk 301
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11 CONTENTS Thermal Processing of C
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Thermal Processing of Canned Foods
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12 CONTENTS Thermal Processing of R
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Thermal Processing of Ready Meals 3
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Infrared Heating 505 TABLE 16.1 Com
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Infrared Heating 519 Temperature (
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Infrared Heating 521 and thawing ti
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Infrared Heating 523 15. T Takeo. F
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Infrared Heating 525 55. CM Liu, N
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638 Index Tea, 451, 510 Temperature
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640 Index Wax beans, 398, 411 Web s
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Thermal Food Processing

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