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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. Th e number of carbon units in the backbone determines its length. Th e 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.
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. Th ey are commonly found in almost any grocery store, usually in plastic containers of diff erent sizes. Th e 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 fl avors and off odors. Fats and oils go rancid because of two chemical processes; hydrolytic rancidity and oxidative rancidity. Hydrolytic rancidity occurs when the fat (triglyceride) is broken up into free fatty acids and glycerol by the presence of water. Th e presence of the enzyme lipoprotein lipase (LPL) quickens this process. Th e unfavorable odor and fl avor are the results of tasting individual short chain fatty acids instead of the whole triglyceride. Dairy products are mostly aff ected by hydrolytic rancidity. Keeping fats and oils 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 fl avors 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
Solid fats are oft en sold in cans or plastic containers looking like cans. Oils are most oft en sold in plastic bottles. Oils are rarely sold in glass containers. Metal cans are the most resistant to long-term oxygen transfer (transmission of oxygen
STORAGE CONDITIONS & SHELF LIFE
All fat or oil foods deteriorate even when handled and stored under ideal conditions. Store oils away from oxygen (air) if possible. Storing oils below room temperature reduces the rate of oxidation and slows the development of rancid fl avors. Freezing oils or fats will not cause the container to explode out. Fats and oils will actually contract a little when frozen.
Oils that do not require heating to remain liquid resist deterioration more than the higher melting products. Most shortening and other similar products will maintain an acceptable fl avor and oxidative stability for 2 to 3 weeks in melted form with adequate controls (Shelf Life Advice, 2010).
NUTRITION
Lipids (fats and oils) perform many life-supporting functions in each cell of our body. Th ey are part of every cell membrane and every organ and tissue. Fats add fl avor to the foods that many of us are used to and savor and they also serve as a great energy source that provides 9 calories for every gram of fat consumed. A few vitamins only dissolve in lipids (Haas, 2006).
In a normal diet (non-emergency situation) there are healthier choices for fat intact. Polyunsaturated and monounsaturated fats are less likely to cause heart disease compared to saturated fat. Polyunsaturated and monounsaturated trans-fats also cause health concerns. However, during an emergency situation, long-term heart disease will take a back seat to immediate concerns for survival.
ALLERGIES: Th ere are no known allergies associated with fats or oils. Some may think that soybean oil would be an allergen; however, commercially processed soybean vegetable oil contains no protein and therefore it is not allergenic.
USE FROm STORAGE
Fats and oils can be used as is directly from storage. Once a container is opened and contacts air, the shelf life will drop. Th erefore, opened containers should be used relatively quickly. Rancid fats or oils cannot be made palatable. Few recipes could possibly add enough strong ingredients to distract the human palate. Simply discard rancid oils and replace them.
Type of Fat/Oil Refrigerator Freezer Pantry
Butter, opened Butter, unopened Vegetable oil, opened Vegetable oil, unopened Salad oil, opened Salad oil, unopened Margarine, opened Margarine, unopened Peanut butter, opened Peanut butter, unopened Vegetable shortening Olive oil* 2-3 weeks 1-2 months -- -- -- -- 1 month 4-5 months 6 months -- 6-9 months -- -- 9 months -- -- -- -- -- 1 year -- -- -- -- -- 1-3 months 6 months 2 months 3 months -- -- -- 2-3 months 6-9 months 3 months 1-2 weeks
*Olive oil can become rancid quickly at room temperature, but it develops fat crystals in the refrigerator. However, olive oil can be stored in the freezer and allowed to thaw.