FATS & OILS
INTRODUCTION Edible fats and oils are not highly perishable foods because of their absence of water. Microorganisms require water to grow. Fats and oils have variable shelf lives during which minor changes occur. Fats are generally solid at room temperature and oils are liquid at room temperature. Fats and oils contain a glycerol backbone and three fatty acids that make up triglycerides. The number of carbon units in the backbone determines its length. The longer the fatty acid, the more likely the triglyceride is to be a fat; the shorter the fatty acid, the more likely the triglyceride is to be an oil.
acids instead of the whole triglyceride. Dairy products are mostly affected by hydrolytic rancidity. Keeping fats and oils
QUALITY AND PURCHASE Fats and oils are the raw materials for liquid oils (e.g. vegetable oil, olive oil), shortenings, margarines, and other specialty or tailored products that are functional ingredients in food products. They are commonly found in almost any grocery store, usually in plastic containers of different sizes. The quality of edible fat depends on three factors: the type of raw material employed; the storage time and temperature of the raw material before rendering, and the type of rendering equipment used. Do not home can butter for emergency storage. Rancidity is a chemical reaction of fats and oils that produces off flavors and off odors. Fats and oils go rancid because of two chemical processes; hydrolytic rancidity and
cold slows down the hydrolytic rancidity process, but even freezing does not stop the quality deterioration completely (McWilliams, 2006). Oxidative rancidity occurs in fats and oils that contain unsaturated fatty acids; mostly because unsaturated fats are less stable than saturated fats. Oxidation produces an accumulation of aldehydes and ketones, which are compounds that are also responsible for the unfavorable flavors and odors. Heat, light, oxygen, and metal ions encourage (speed up) oxidative rancidity. To prevent oxidative rancidity, products should be kept cool and covered or sealed from air. Do not combine new and old fats (Klein, 2013).
PACKAGING
oxidative rancidity. Hydrolytic rancidity occurs when the fat
Solid fats are often sold in cans or plastic containers looking
(triglyceride) is broken up into free fatty acids and glycerol by
like cans. Oils are most often sold in plastic bottles. Oils
the presence of water. The presence of the enzyme lipoprotein
are rarely sold in glass containers. Metal cans are the most
lipase (LPL) quickens this process. The unfavorable odor and
resistant to long-term oxygen transfer (transmission of oxygen
flavor are the results of tasting individual short chain fatty CANNED FOOD, FAT & OIL STORAGE
37
