ters. At room temperature and above, the rate of reaction increases. Because of these characteristics, and its pleasant taste, cream of tartar is used in some baking powders and in the leavening systems of a number of baked goods and dry mixes.
Antioxidants, Sequestrants, and Synergists
Oxidation is promoted by the catalytic action of certain metallic ions present in many foods in trace quantities. If not naturally present in a food, minute quantities of these metals, particularly iron and copper, can be picked up from processing equipment. Oxidation is the cause of rancidity, an off flavor development in fat. It is also responsible for off color development that renders a food unappetizing in appearance. Hydroxy-polycarboxylic acids such as citric acid sequester these trace metals and render them unavailable for reaction. In this regard the acids function as antioxidants.
Hydroxy-polycarboxylic acids are often used in combination with antioxidants such as ascorbates or erythor-bates to inhibit color and flavor deterioration caused by trace metal catalyzed oxidation. The ascorbates and ery-thorbates as well as BHA, BHT, and other approved antioxidants and reducing agents are oxygen scavengers and are effective when used alone. The effect of the combination of a sequestrant, such as a hydroxy-polycarboxylic acid, and an antioxidant is synergistically greater than the additive effect of either component used alone.
Citric acid is the most prominent antioxidant synergist although malic and tartaric acid have been used. In meat products, U.S. Department of Agriculture regulations permit citric acid in dry sausage (0.003%), fresh pork sausage (0.01%), and dried meats (0.01%). A short dip in a bath containing 0.25% citric and 0.25% erythorbic acid improves quality retention in frozen fish. This treatment is also applicable to shellfish to sequester iron and copper that catalyze complex blueing and darkening reactions.
Untreated fats and oils, both animal and vegetable, are likely to become rancid in storage. Oxidation is promoted by the catalytic action of certain metallic ions such as iron, nickel, manganese, cobalt, chromium, copper, and tin. Minute quantities of these metals are picked up from processing equipment. Adding citric acid to the oil sequesters these trace ions, thereby assisting antioxidants to prevent development of off flavors. Although the oil solubility of citric acid is limited, this can be overcome by first dissolving it in propylene glycol. The antioxidant can be dissolved in the same solvent so that the two can be added in combination.
The acids approved by the U.S. Department of Agriculture for this function in meat products (1) must be used only in combination with curing agents. In addition to ascorbates and erythorbates, the approved acids are:
1. Fumaric acid to be used at a maximum of 0.065% (1 oz-100 lb) of the weight of the meat before processing.
2. GDL to be used at 8 oz to each 100 lb of meat in cured, comminuted meat products and at 16 oz per 100 lb of meat in Genoa salami.
3. Sodium acid pyrophosphate not to exceed, alone or in combination with other curing accelerators, 8 oz per 100 lb of meat nor 0.5% in the finished product.
4. Citric acid or sodium citrate to replace up to 50% of the ascorbate or erythorbates used or in 10% solution to spray surfaces of cured cuts.
In conjunction with sodium erythorbate or related reducing compounds, GDL accelerates the rate of development of cure color in frankfurters during smoking. This permits shortening smokehouse time by one half or more and products have less shrinkage and better shelf life.
The special property of GDL upon which these advantages depend is its lactone structure at room temperature. In this form there is no free acid group and the GDL can thus be safely added during the emulsifying stage of sausage making without fear of shorting out the emulsion. Under the influence of heat in the smoking process, the ester hydrolyzes rapidly and is converted in part to gluconic acid. This lowers the pH of the emulsion during smoking, providing conditions under which sodium erythorbate or other reducing compounds (erythorbic acid, ascorbic acid, and sodium ascorbate) react with greater speed to convert the nitrite of the cure mixture into nitric oxide. The nitric oxide, in turn, acts upon the meat pigment to form the desired red nitrosomyoglobin.
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