Future trends

We have demonstrated that ohmic heating is a very unique thermal process. Ohmic heating is considered a 'minimal process' besides the 'HTST' process. Potential uses of ohmic heating include 15,47-50 2 Sterilisation and pasteurisation. However, as mentioned earlier, there has been only limited research quantifying the potential benefits of ohmic heating processes in terms of nutrition preservation. More research is needed to realize the advantages of ohmic heating and to promote the...

Vitamin loss during processing

As already discussed, all vitamins exhibit a degree of instability, the rate of which is affected by a number of factors. Naturally-occurring vitamins in foods are susceptible to many of these factors during the harvesting, processing and storage of the food and its ingredients. It is particularly important that the effects of processing are taken into consideration when assessing vitamin stability in foods, as the food may have been subjected to a number of adverse factors during processing....

References

Akdogan H (1999), 'High moisture food extrusion', Intl J Food Sci Technol, 34(3), 195-207 alonso r, grant g, dewey p and marzo f (2000), 'Nutritional assessment in vitro and in vivo of raw and extruded peas (Pisum sativum L)', J Agric Food Chem, 48(6), 2286-90 alonso r, grant g and marzo f (2001), 'Thermal treatment improves nutritional quality of pea seeds (Pisum sativum L) without reducing their hypocholesterolemic properties', Nutr Res, 21(7), 1067-77 andersson y and hedlund b (1991),...

Vitamin D and other aspects of health Behaviour

Specific vitamin D receptors are found in parts of the brain and spinal cord (Maxwell, 2001). Seasonal changes in 25-OHD and 1,25-OHD could have an effect on hormonal function, mood and behaviour. For example, seasonal affective disorders (SAD) appear to have a latitude gradient, with mood changes due to a reduction in daylight hours and altered circadian secretion of melatonin. Whether seasonal changes in UV light and vitamin D contribute is unknown. Mortality rates from colon cancer are...

Factors affecting vitamin stability

One of the very few attributes that the vitamins have in common is that none is completely stable in foods. The stability of the individual vitamins varies from the relatively stable, such as in the case of niacin, to the relatively unstable, such as vitamin B12. The factors that affect stability vary from vitamin to vitamin and the principal ones are summarised in Table 10.2. The most important of these factors are heat, moisture, oxygen, pH and light. The deterioration of vitamins can take...

Commercial high pressure treated food products

With regard to the large-scale application of high pressure technology in the food industry, a problem still to be solved today is the improvement of the economic feasibility, i.e. the high investment cost mainly associated with the high capital cost for a commercial high pressure system. The cost of a vessel is determined by the required working pressure temperature and volume. Furthermore, once technically and economically feasible processes have been identified, one needs to evaluate whether...

The advantages of ohmic heating

Ohmic heating has unique characteristics with associated advantages, which will certainly have significant impact on the nutritional values of ohmically heated products. Briefly, these characteristics and advantages are 4,8 1 Heating food materials volumetrically by internal heat generation without the limitations of conventional heat transfer or the non-uniformities commonly associated with microwave heating due to dielectric penetration limit. 2 Particulate temperatures similar to or higher...

Infrared processing in the food industry

The basic concepts of infrared radiation are High heat transfer capacity Heat penetration directly into the product Good possibilities for process control No heating of surrounding air. These qualities indicate that infrared radiation should be an ideal source of energy for heating purposes (Skjoldebrand, 1986). Distinguished from microwave heating, the penetration properties of infrared radiation are such that a suitable balance for surface and body heating can be reached, which is necessary...

Fatsoluble vitamins Vitamin A

Nutritionally, the human body can obtain its vitamin A requirements from two sources from animal sources as forms of retinol, and from plant sources from b-carotene and related carotenoids. Both sources provide a supply of vitamin A, but by different metabolic pathways. In terms of stability the two sources are different from each other. Vitamin A is one of the more labile vitamins and retinol is less stable than the retinyl esters. The presence of double bonds in its structure makes it subject...

Faecal bulking index and wheat bran equivalents

Faecal bulking capacity is an important property of foods because bulk in the large bowel has a crucial role in large bowel function and health (Table 7.6). The direct relationship between faecal bulk and 'regularity' is of concern to a large Table 7.6 Putative links between properties and effects of bulk in the large intestine Toxin removal, colonic exposure reduced, decreased transit time. Replenishment of substrates for fermentation - decreased colon cancer Less protein putrefaction to...

Changes in frying oil Types of reaction

The oil is subject to three types of reaction during deep frying pyrolysis of oxidation products. Triacylglycerols in frying oil are hydrolysed by steam produced from water in the fried product when it is in contact with the hot frying oil. As the two reacting partners are not miscible, the reaction is relatively slow, resulting in the formation of diacylglycerols and free fatty acids. Diacylglycerols are more polar and therefore their contact with water vapour is better monoacylglycerols and...

Transformations not involving sugars crosslinked amino acids

Another kind of transformation of the side chains of protein-bound amino acids induced by thermal treatments of foods, particularly in basic conditions, is the formation of cross-linked amino acids. A dehydroalanine residue may be formed through elimination of a leaving group from protein-bound serine, O-phosphorylserine, O-glycosylserine, or cystine, and may undergo Michael addition by another nucleophilic amino acid residue (Fig. 11.12). For example the e-amino group of lysine may react to...

Relationship of structure to nutritional quality bioavailability

The overall content of a given nutrient in a food is not always a useful indicator of its nutritional value because not all of the nutrient present is absorbed. Nutritionists must concern themselves with understanding the proportion of an avail able nutrient that is digested, absorbed, and ultimately utilised. In the case of nutrients or phytochemicals, whose beneficial effects are directed towards inhibiting degenerative diseases, it is important to know whether or not the nutrient is reaching...

The effect of ohmic heating on nutrient loss diffusion

Betanin Cell

Studies40,42 have shown that compared with conventional heating, ohmic heating enhanced diffusion of charged species between solid particles and the surrounding liquid, which could have some impact on loss of nutrients from solid particles to carrier liquid. This becomes undesirable only if the carrier liquid is not to be consumed together with the solid particles. Figure 19.3 shows that the transfer of betanin dye between beetroot and the surrounding fluid increases linearly with applied...

Bioavailability of provitamin carotenoids

De Pee and West 1996 proposed that control of VADD depends to a large extent on an adequate supply of vitamin A and the vitamin A supply is determined by Food intake x pro -vitamin A content x bioavailability bioefficacy, where Bioavailability fraction of ingested nutrient available for normal physiological functions and storage Jackson, 1997 Bioefficacy efficiency of absorption and conversion of ingested nutrient to the active form e.g. b-carotene to retinol van Lieshout et al, 2001 . 3.4.1...

The history of food irradiation

As early as in 1885 and 1886 ionising radiation was discovered and in subsequent years its bactericidal effects were described. The purpose of the first patent on food irradiation Appleby and Banks, 1905 was to bring about an improvement in food and its general keeping quality. It was followed by an invention of an 'Apparatus for preserving organic materials by the use of X-rays' Gillett, 1918 . However, radiation sources strong enough for industrial exploitation were not available before the...

The effect of ohmic heating on nutrient loss thermal destruction

Since systematic research on ohmic heating has a much shorter history than has conventional heating, food scientists and technologists might look to microwave heating for information on nutrient changes. In general, many improvements in nutritional quality were found using microwaves cooking in a minimum of water retained more K, vitamin B12, and vitamin C, and the absence of surface browning retained more amino acid availability, especially lysine , and microwave heating induces no significant...

Dietary copper requirements

Despite the known essentiality of copper in humans, dietary requirements are still uncertain. World-wide, a number of Dietary Reference Values are recommended for copper intake see Table 5.2 but the variability between them is indicative of the lack of consensus between advisory bodies. Making dietary recommendations, even of Estimated Average Requirements EAR , is difficult owing to a lack of adequate data. In the UK, the Department of Health considers the available data on human copper...

Conclusion

There has been considerable emotive and public health debate over the last two decades on the relative importance of meat in the diet of modern humans. Early dismissive arguments have more recently been revisited and challenged as a result of the continual progress and review of nutritional science. The early focus on fat as the predominant cause of western style diseases of affluence led, na vely, to meat being blamed for diet related problems. More recently, the focus on the diets of our...

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Pyrroles Amadori

Fig. 11.4 Mechanism of the Strecker degradation of amino acids. Below pH 3 and above pH 8 or at temperatures above 130 C caram lisation , sugars will degrade in the absence of amines Ledl and Schleicher, 1990 . Ring opening followed by 1, 2 or 2, 3-enolisation are crucial steps in ARP transformation and are followed by dehydration and fragmentation with the formation of many very reactive dicarbonyl fragments. This complex of reactions is considered the intermediate stage of the MR. Maillard...

The principles of ohmic heating

Ohmic heating is a thermal process in which heat is internally generated by the passage of alternating electrical current AC through a body such as a food Fig. 19.1 A schematic diagram of an ohmic heating device. system that serves as an electrical resistance. Ohmic heating is alternatively called resistance heating or direct resistance heating. The principles of ohmic heating are very simple, and a schematic diagram of an ohmic heating device is shown in Fig. 19.1. During ohmic heating, AC...

The effect of MAP on the nutritional quality of fresh fruits and vegetables

During the last few years many studies have demonstrated that fruit and vegetables are rich sources of micronutrients and dietary fibre. They also contain an immense variety of biologically active secondary metabolites that provide the plant with colour, flavour and sometimes antinutritional or toxic properties Johnson et al, 1994 . Among the most important classes of such substances are vitamin C, carotenoids, folates, flavonoids and more complex phenolics, saponins, phytosterols,...