Types of Fats and Rancidity
Author is Elizabeth Blessing, MSN, Green Bean Delivery
Last week’s blog post on Fabulous Fats discussed the vital roles fats play in the human body. This week, we will look at the different types of fats, chemically speaking, as well as rancidity.
Triglyceride is the most common form of fat found in plants and humans. It is made of three fatty acid chains that are attached to a glycerol backbone.
Saturated fat is a triglyceride made mostly of saturated fatty acids. The fatty acid is saturated with hydrogens, making the structure straight and rigid. This rigid structure makes it easy for the triglycerides to stack on top of each other and form a solid. Saturated fats are solid at room temperature. Food sources include animal foods, such as beef, lamb, chicken, pork, fish, dairy products, butter, lard and eggs as well as plant foods, including coconut and palm oil.
Monounsaturated fat is a triglyceride made mostly of monounsaturated fatty acids. The fatty acid has one point of unsaturation which means hydrogens are lost and a double bond is formed. This double bond forms a kink in the fatty acid which makes it difficult for it to stack together. Monounsaturated fats are liquid at room temperature. Food sources include olive oil, avocado, peanut oil and canola oil.
Polyunsaturated fat is a triglyceride made mostly of polyunsaturated fatty acids. The fatty acid has more than one point of unsaturation which means there are more hydrogens lost and more double bonds formed. Just like monounsaturated fat, this makes it difficult to stack together, and therefore polyunsaturated fat is a liquid at room temperature. Food sources include nuts and seeds, safflower oil, corn oil, soybean oil, sesame oil and sunflower oil. Most vegetable oils are in the form of polyunsaturated fats and are found abundantly in plant foods.
Trans fat is an unsaturated fatty acid that loses its natural kink through the process of hydrogenation. This makes it rigid like saturated fat and therefore solid at room temperature. The most common food sources include margarine, shortening, foods made with and/or fried in these fats, and in very small amounts, it is naturally found in meat and dairy products.
Rancidity is the deterioration of fat resulting in undesirable flavors and odors. Rancid fats are dangerous to the human body. They can cause free radical damage which leads to inflammation and a host of problems, such as heart disease, diabesity (obesity and diabetes), Alzheimer’s and several other conditions. The more points of unsaturation a fatty acid contains, the higher the risk of rancidity. This means saturated fat is the most stable and resistant to rancidity, while polyunsaturated fats are the least stable and most prone to rancidity. Exposing fats to heat, air and light increase the risk of rancidity. To protect fats and oils from rancidity, store them in tightly sealed containers in a cool, dark place. Store nuts, seeds and flour (flour contains a small amount of fat) in the freezer, and retrieve as needed. Store vegetable oils in the refrigerator, especially polyunsaturated oils. They will become cloudy, but allowing them to come to room temperature will clear that away. Buy oils in small amounts that will be consumed quickly. It is unsafe to buy in bulk and have the oil sit in the cabinet for several months.
Next week’s blog post will focus on what types of fats and oils should be used when cooking, baking and frying, and which ones should not be heated at all.
To stay up to date on the latest food and nutrition news, or to get recipe ideas, check out Green BEAN Delivery’s Healthy Times blog.
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