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Unit Food Science Problem Area Processing Animal Products Lesson Curing Ingredients in Meat Products Student Learning Objectives 1. Explain the effects of sodium nitrite and salt in cured meat products. 2. Describe the general role of food additives in meat products. Terms Antimicrobial agent Denature Enzyme Food additive Myoglobin Preservative Product yield Water activity What are the effects of sodium nitrite and salt in cured meat products? Sodium nitrite and salt have various effects on cured meat products. A. Sodium nitrite is commonly used in cured meats as an antimicrobial agent, an additive that prevents or slows down the growth of bacteria or microorganisms. Sodium nitrite reacts with myoglobin, a pigment in fresh meat, to form nitric oxide myoglobin, which has a dark red color. 1. When heat is applied to nitric oxide myoglobin, the substance becomes denatured. The term denature refers to the change of a protein by heating so that the original properties are changed due to a change in molecular structure. 2. Denatured nitric oxide myoglobin forms nitrosyl hemochrome, a pigment that gives the cured meat a bright pink color when cooked. 3. When meat is cooked without the addition of sodium nitrite (or chemical with similar action), the myoglobin becomes denatured and the meat turns brown. 4. In addition to the color change, sodium nitrite gives the product a cured meat flavor and helps to prevent spoilage. 5. Celery also contains nitrite, and if mixed with meat and allowed to equilibrate, the celery will develop a pink ring around the edges when the meat mixture is cooked. B. Salt acts as a food preservative by reducing water activity. A preservative is any type of food additive consisting of either antioxidants or antimicrobial substances. Since most bacteria and microorganisms depend on water to function, reducing water activity in meat will prolong the freshness of the meat product. Water activity is a measure of the unbound or free water that is available to support biological and chemical reactions. 1. Salt also interacts with meat proteins to increase their ability to bind with water, thus improving product yield. Product yield is the ratio of the weight of a sample of cooked meat product to the weight of the sample before cooking. The product yield is expressed as a percentage. 2. Salt also enhances flavor and retards bacterial growth, prolonging the shelf life of the product. In general, what are the roles of food additives in meat products? A. Food additives are useful chemicals of natural or synthetic origin used in small amounts to augment or modify the characteristics of a food product. Some common food additives are: 1. Antifoaming agents (dimethylpolysiloxane, mono- and diglycerides) 2. Colorants (azo and triphenylmethane) 3. Proteases for tenderness (ficin, papain, bromelain, fungal proteases) 4. Flavor enhancers (monosodium glutamate—or MSG) 5. Preservatives B. Proteases are enzymes, a group of catalytic proteins that are produced by living cells and that promote the chemical processes of life without being altered or destroyed. C. The color stability of fresh meat is largely dependent on storage temperature, packaging environment, and rate of effect of oxygen on the meat. 1. Higher temperatures accelerate discoloration (from red to brown). 2. When fresh meat is exposed to high levels of oxygen, as in the open air or high oxygen packaging, the myoglobin is converted to a bright red oxymyoglobin, which is resistant to further oxidation. However, with packaging materials having low oxygen permeability, myoglobin combines with oxygen to form metmyoglobin, which is brown in color. 3. Regardless of packaging, fresh meat will always turn brown, starting from the center where oxygen levels are lowest, and working its way outward. Different muscles exhibit different rates of metmyogobin formation, and therefore have different rates of color change. This also means that a brown color in fresh meat is not necessarily an indication of spoilage. Review/Summary What are the effects of sodium nitrite and salt in cured meat products? In general, what are the roles of food additives in meat products?