Food products, periodate oxidative

Lipid oxidation in food products develops slowly initially, and then accelerates at later stages during storage (Figure 7.1). The induction period (IP), or shelf life at room temperature, is defined as the time to reach a constant percent oxidation of the fat or the end of shelf life. From an industrial point of view, shelf life is also defined as the storage time before the quality of a product becomes imacceptable to consumers. 

The oxygen uptake of an unsaturated fatty acid as a function of time is shown in Fig. 3.18. Studying this figure helps in the understanding of the elementary steps involved in autoxidation. The extreme case 1 demonstrates what has invariably been found in food the initial oxidation products are detectable only after a certain elapsed storage time. When this induction period, which is typical for a given autoxidation process, has expired, a steep rise occurs in the reaction rate. The proox-... 

Starches have been oxidized with numerous oxidizing reagents mainly to reduce molecular weight and to increase solubility, for paper and food applications. Commercial oxidized starches are batch prepared utilizing room temperature conditions and low oxidant concentration (<3%) such as hypochlorite, permanganate, hydrogen peroxide, persulfate, periodate, and dichromate [60, 82-84]. Starch oxides have found a large application in adhesive production. 

The time to reach a certain PV may be used as an index of oxidative stability for food lipids. The effects of antioxidants and food processing on fats are often monitored in this way. Thus, a longer time period to reach a certain PV is generally indicative of a better antioxidant activity for the additive under examination. However, a low PV represents either early or advanced oxidation the breakdown of peroxides to secondary oxidation products will result in a decrease in PVs during the storage period. For determination in foodstuff, a major disadvantage to the classical iodometric PV assay is that a 5-g test portion is required it is sometimes difficult to obtain sufficient quantities of lipid from foods low in fat. Despite its drawbacks, PV determination is one of the most common tests employed to monitor lipid oxidation. 

As oxidation normally proceeds very slowly at the initial stage, the time to reach a sudden increase in oxidation rate is referred to as the induction period (6). Lipid hydroperoxides have been identified as primary products of autoxidation decomposition of hydroperoxides yields aldehydes, ketones, alcohols, hydrocarbons, volatile organic acids, and epoxy compounds, known as secondary oxidation products. These compounds, together with free radicals, constitute the bases for measurement of oxidative deterioration of food lipids. This chapter aims to explore current methods for measuring lipid oxidation in food lipids. 

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