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HNSC 1200 (29)
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Lecture 25

HNSC 1200 Lecture 25: Unit 5.2

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Human Nutritional Sciences
HNSC 1200
Snehil Dua

Fat Preservation and Deterioration Learning Objectives: Describe the process of fat preservation and deterioration Define fat replacer and discuss options for fat replacement in foods Course Notes: interization of Fats - A process to produce salad oils that do not crystallize (i.e., become cloudy) at refrigerator temperatures  o Oils can become cloudy at lower temperatures because some of the  triglyceride molecules crystallize or become solid o Involves lowering the temperature of oil to a point at which the triglycerides with high melting points crystallize (20C-0C). The oil is then filtered to remove the crystals and the remaining oil has a lower melting point and does not crystallize  Rancidity - Chemical spoilage that commonly occurs with fats and fatty foods is called  rancidity  o Cause off-flavors and rancid odors o The longer a fat is stored, the greater the risk for rancidity oSDP o Fats and oils exposed to heat, oxygen and light are more likely to become rancid (i.e., fats and oils are used for cooking o Highly unsaturated fats/oils such as polyunsaturated fats are much more susceptible than saturated or monounsaturated fats Foods that easily go rancid are nuts, wheat germ and whole wheat flour Fats that have become rancid should be discarded, as they will transfer their off-flavors to the foods they are used in/with There are two types of Rancidity 1. Oxidative rancidity Occurs primarily with the unsaturated fatty acid portions of triglycerides Reaction begins with the addition of oxygen to carbon atoms next to a double bond in a fatty acid. The reaction results in formation of hydrogen peroxide. Hydrogen peroxide molecules readily breakdown into volatile products that have off occurs and flavors characteristic of rancid fat (e.g., ketones, alcohols and aldehydes). Oxidative damage can be prevented or slowed down through the use of antioxidants such as BHT (butylated hydroxytoluene, an antioxidant and antimicrobial compound) or vitamin E (an antioxidant). Hydrolytic rancidity Hydrolysis involves breaking of chemical bonds due to the addition of water and enzyme activity Hydrolytic rancidity is the result of the breaking of triglyceride structure composed of short chain fatty acids such as butyric acid and caproic acid (found in butter). o The short chain fatty acids are volatile and produce off flavors and odors o Heat acts as a catalyst for this reaction, which can cause problems when wet foods are deep-friend. This introduces water to the oil, making the oil prone to hydrolytic rancidity, especially when the oil has not been heated (as heat breaks down the enzymes that also fuel hydrolytic rancidity) Butter stored at room temperature can be at risk for hydrolytic rancidity, because this temperature is an ideal environment for the enzymes that contribute to the rancidity, and becau
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