Determination of Acidic Substances in Food

Types and functions of acidic substances in food

The sour components in food are mainly organic and inorganic acids. Most organic acids have a refreshing sour taste, while inorganic acids generally have an unpleasant bitter taste, so people often do not use inorganic acids as food acidifiers.

Organic acids in food exist in both free and acidic salt states. Common organic acids include citric acid, malic acid, tartaric acid, oxalic acid, succinic acid, lactic acid, and acetic acid. Some of these organic acids are natural ingredients inherent in food, such as citric acid and malic acid in fruits, and lactic acid in fish and meat; Some are artificially added in food processing, such as citric acid in formulated beverages; Some are also produced during the production, processing, and storage processes, such as lactic acid in yogurt.

The role of acidic substances in food is reflected in multiple aspects. One is that it affects the odor and taste of food, such as organic acids with strong fruit aromas that can stimulate appetite. Secondly, it affects the color of food. The color tone of pigments contained in fruits and vegetables is closely related to their acidity. For example, reducing pH during fruit processing can inhibit enzymatic browning of fruits, thereby maintaining their natural color. Thirdly, it affects the stability of food, for example, organic acids can prevent the oxidation of vitamin C and improve its stability.

The significance and methods of measuring food acidity

Acidity measurement can evaluate the quality of food raw materials and products. For example, by measuring the content of sugars and acids in fruits and vegetables, the maturity of fruits and vegetables can be determined. During the ripening process of tomatoes, the total acidity decreases from 0.94% in the green ripening stage to 0.64% in the complete ripening stage, while the sugar content increases and the sugar to acid ratio increases, resulting in a good taste. The content of volatile acids is an important technical indicator for measuring the quality of fermented fruit products. If unqualified fruit and vegetable raw materials are used in production, normal process operations are violated, or semi-finished fruits and vegetables are left for too long before canning, the fermentation of sugar will increase the amount of volatile acids and reduce the quality of food. Acidity measurement can determine the freshness of food, such as the determination of effective acidity in fresh meat, which can determine the quality of meat. For example, the pH of fresh meat is 5.7-6.2, and if pH>6.7, it indicates that the meat has spoiled. Milk and its products, tomato products, beer, and beverage products, when the total acid content is high, indicate that these products have been caused by lactic acid bacteria causing rancidity. In the oil and fat industry, the quality and refining degree of oil can be distinguished by measuring the content of free fatty acids.

Acidity measurement provides important basis for color matching, seasoning, and controlling food stability, and has guiding significance for food processing and production processes. Control the browning of food by controlling pH; Obtain products with better flavor by adjusting the sugar to acid ratio. The quality standards of Baijiu, beer, soy sauce, vinegar and other fermented products have clear requirements for acidity.