Presentation on theme: "Understanding Food Chapter 10: Fats and Oils. Functions of Fats in Food."— Presentation transcript:
Understanding Food Chapter 10: Fats and Oils
Functions of Fats in Food
Shortening: A fat that tenderizes, or shortens, the texture of baked products by impeding gluten development, making them softer and easier to chew. Emulsion: A liquid dispersed in another liquid with which it is usually immiscible (incapable of being mixed). Surfactant: Surface-active agent that reduces a liquid’s surface tension to increase its wetting and blending ability.
Functions of Fats in Food-Heat transfer How is food heated in deep-fat frying? In deep-fat frying, food is quickly cooked in several stages involving: Moisture transfer Fat transfer Crust formation Interior cooking
Functions of Fats in Food There are two types of emulsions: 1. Oil-in-water, in which oil droplets are dispersed throughout the water. 2. Water-in-oil, in which water droplets are dispersed throughout the oil.
Functions of Fats in Food- emulsions There are three parts to an emulsion: The dispersed or discontinuous phase, usually oil. The dispersion or continuous phase, most likely water-based. An emulsifier, which is a stabilizing compound that helps keep one phase dispersed in the other.
Functions of Fats in Food
Creaming: In an emulsion, the collection and rising of the lighter phase, usually oil, to the top of the mixture. Creaming is a process that achieves temporary emulsion status. Stabilizers may be added to an emulsion to decrease the tendency of the emulsion to separate, which creates a viscosity similar to soft yogurt; this is referred to as a semi-permanent emulsion. Permanent emulsions are very viscous and stable, to the point that they do not separate.
Functions of Fats in Food Fat’s melting point is determined by the following four characteristics of the fatty acid: Degree of saturation Length Cis-trans configuration Crystalline structure
Functions of Fats in Food
Plasticity The plasticity of fat is its ability to hold its shape but still be molded or shaped under light pressure. Flavor The flavor developed in certain foods by fats is very difficult to duplicate. Texture Fats also contribute texture.
Functions of Fats in Food Appearance Foods are made more appealing by pigments located in a food’s natural fats. Satiety or Feeling Full Fats induce a sense of fullness, or satiety.
Types of Fats The different types of fats: Butter Margarine Shortenings Oils Lard Cocoa butter Fat replacers
Types of Fats Butter is made from the cream of milk.
Types of Fats Butter can be purchased in a number of forms. Choices are influenced by: Taste Texture Other options may include: Compound or flavored butter Powdered butter Clarified butter Brown or black butter Clarified butter: Butter whose milk solids and water have been removed and thus will not burn. Smoke point: The temperature at which fat or oil begins to smoke.
Types of Fats Butter can be purchased in a number of forms. Choices are influenced by: Taste Texture Standard stick margarine must contain at least 80% fat, about 16% water, and 4% milk solids.
Types of Fats Diacetyl is added to margarine for flavoring because it is largely responsible, in addition to short fatty acids, for butter’s characteristic flavor
Types of Fats Shortenings are plant oils that have been hydrogenated to make them more solid and pliable. Many different types of oils are available for food preparation purposes, and the type of oil used depends on the desired outcome.
Types of Fats Many refined oils are without any distinguishing characteristics. Unrefined, cold- pressed oils, such as peanut and olive oils, have the full flavor of the plants from which they were pressed. Winterizing: A commercial process that removes the fatty acids having a tendency to crystallize and make vegetable oils appear cloudy. Hydrogenation: A commercial process in which hydrogen atoms are added to the double bonds in monounsaturated or polyunsaturated fatty acids to make them more saturated.
Types of Fats These animal sources of fat are primarily saturated fat: Lard, which is the fat from swine. Tallow is also an animal fat, but it is derived from beef cattle or sheep. Suet is the solid fat found around the kidneys and loin of beef and sheep.
Types of Fats Interesterification: A commercial process that rearranges fatty acids on the glycerol molecule in order to produce fat with a smoother consistency.
Fat Replacers Substitutes physically resemble fats, are often lipid based, and usually replace the fat in foods on a one-to-one basis to duplicate the functional properties of fat. Fat mimetics are water-soluble, often protein or carbohydrate based, and imitate the mouthfeel of fat. Fat-soluble substitutes and extenders replace the weight added by fat.
Food Preparation with Fats Flash point: The temperature at which tiny wisps of fire streak to the surface of a heated substance (such as oil). Fire point: The temperature at which a heated substance (such as oil) bursts into flames and burns for at least 5 seconds. Polymerization: A process in which free fatty acids link together, especially when overheated, resulting in a gummy, dark residue and an oil that is more viscous and prone to foaming.
Food Preparation with Fats Lower-Fat Preparation Techniques Meal patterns that are lower in fat. Especially lower in saturated fat. Rely on lower-fat or nonfat cooking methods. Reduce the fat in recipes.
Food Preparation with Fats Other ways to reduce the amount or modify the type of fat in the diet include: Fruit preserves and honey Mustard, ketchup, or low-fat salad dressing or mayonnaise Purées of fruits such as plums, dates, apples, and figs Crumb crusts Double-crust pies can be converted to one- crust pies. A nonfat condiment such as salsa, relish, or chutney
Storage of Fats Storage of fat depends on its type. Fats such as butter and margarine are best stored in the refrigerator. Shortenings and most oils are usually stored at room temperature and should be kept tightly covered in a dark spot on the cupboard shelf. They will keep longer if refrigerated. Olive oil has a shorter shelf life than most vegetable oils and should be refrigerated fairly soon after opening.
Storage of Fats Rancidity: the chemical deterioration of fats, which occurs when the triglyceride molecule and/or the fatty acids attached to the glycerol molecule are broken down into smaller units that yield off- flavors and odors. There are two basic types of rancidity: Hydrolytic rancidity Oxidative rancidity
Storage of Fats Hydrolytic Rancidity: Fats become rancid when exposed to water, usually the water found frozen on food to be fried. Oxidative Rancidity: Fats can also become rancid when they are exposed to the oxygen in air.
Storage of Fats Flavor reversion: The breakdown (oxidation) of an essential fatty acid, linolenic acid, found in certain vegetable oils, leading to an undesirable flavor change prior to the start of actual rancidity. The two most commonly used oils: Cottonseed Corn …are very resistant to flavor reversion.
Storage of Fats Preventing Rancidity Rancid products have reduced shelf lives and must be discarded. In the past, cereal manufacturers incorporated predominantly saturated fatty acids into their products to reduce the risk of rancidity.
Storage of Fats Avoid Oxygen and Heat: Pack items which are high in unsaturated fatty acids in vacuum packs or nitrogen to prevent contact with oxygen. Antioxidants: Added to foods containing large amounts of unsaturated fats to prevent rancidity.