Lipid Oxidation/Stability

Abstract

Lipids are important macromolecules in food. A food product's nutritional value as well as its flavor, texture, general palatability, and storage stability are affected by lipids. Therefore, both physical and chemical criteria are needed by the food processor to assess or monitor the quality of fats and oils. The basic characteristics of certain food items, such as edible oils, will be dependent upon their source. Variation from these norms can be ascertained before the oils are used in other foodstuffs. In effect, knowledge of the quality of the lipid before shipping the product to market, or use in fabricated foods, is of economic importance to the processor.Lipids are susceptible to oxidation and, as such, analytical protocols are required to measure their quality. Autoxidation is one of the chief processes by which lipids degrade. During the early stages of this autocatalytic free-radical chain reaction, the positions of double bonds in unsaturated fatty acids are changed and hydroperoxides are produced. These alterations can be monitored by simple analytical protocols. Spectrophotometric, iodometric, and colorimetric methods for measuring the early stages of lipid oxidation are described in this unit. In Basic Protocol 1, UV absorbance, measured at 233 and 268 nm, is employed to monitor the formation of conjugated dienes (CDs) and trienes (CTs) of polyunsaturated fatty acids (PUFAs), respectively. Increasing absorption values are an indication that oxidation is proceeding. This physical method is performed on oils directly or on lipid extracts, and is anondestructive assay. For CD formation to occur, lipid samples that contain unsaturated fatty acids with at least two double bonds are required. The most important lipid of this class in foods is linoleic acid (18:2 036). Likewise, unsaturated fatty acid moieties with more than two double bonds are a prerequisite for CT formation. Due to the sensitivity of this technique, only small quantities of lipid are needed, especially when it is suspected that oxidation has taken place.

Atmospheric Cold Plasma Treatment of Soybean Oil with Hydrogen Gas

“…However, treated samples of soybean oil (1.9-5.0 meq/kg) showed a higher peroxide value (PV) than untreated (0.19 meq/kg). These values were below 10 meq/kg, which is the limit of peroxide content requirement for fats and oils (Pegg, 2005). PV is a critical parameter that should be monitored.…”