Malic acid, also known as 2- hydroxysuccinic acid, has two stereoisomers because of asymmetric carbon atoms in the molecule. In nature, it exists in three forms, namely, D- malic acid, L- malic acid and their mixture DL- malic acid. White crystal or crystalline powder, with strong hygroscopicity, easily soluble in water and ethanol. It has a particularly pleasant sour taste. Malic acid is mainly used in food and pharmaceutical industries.

Function 1: acid regulator

The taste of L- malic acid is close to the sour taste of natural apples. Compared with citric acid, L- malic acid has the characteristics of high acidity, soft taste and long residence time. It has been widely used in high-end beverages, food and other industries, and has become the third food souring agent after citric acid and lactic acid. The beverage prepared with L- malic acid is more sweet and sour, and is close to the flavor of natural juice. The combination of malic acid and citric acid can simulate the sour characteristics of natural fruits, making the taste more natural, harmonious and full. Malic acid can be added to cool drinks, powder drinks, lactic acid drinks, milk drinks and juice drinks to improve their taste and flavor. Malic acid is usually used in combination with aspartic acid, a synthetic dipeptide sweetener, as a flavor fixative for soft drinks. 100g malic acid is almost 1.25 times stronger than adding 100g citric acid, or 80g malic acid and 100g citric acid have the same sour taste intensity, so the dosage of L- malic acid can be reduced by 20%, and adding malic acid to some foods can save10% ~ 20. In recent years, the application of L- malic acid in food industry has gradually replaced citric acid because its sour taste stimulating effect is better than citric acid. The application of citric acid in children's and elderly people's food has been restricted by FDA.

ferment

L- malic acid is an intermediate of the organism tricarboxylic acid cycle, which can participate in the fermentation process of microorganisms and can be used as a carbon source for the growth of microorganisms, so it can be used as a food starter. For example, it can be used as a yeast growth promoter or added to fermented milk.

freeze

When there is a certain amount of pectin and sugar, acid is the key condition for gel formation. In order to prevent flocculation and coagulation in concentrated juice production, it is necessary to control the coagulation conditions caused by pectin. Therefore, L- malic acid can gel pectin, so it can be used to make fruit cakes, jelly jams and purees.

Function 2: preservative

Malic acid can be widely used as food preservative. Microorganisms need to grow and reproduce normally in a certain pH environment. If the pH value in the environment is not suitable, it may affect the charged properties of the cell surface, thus causing changes in membrane permeability and affecting the normal metabolism of cells. The effect of acid on microorganisms is not only proportional to the concentration of hydrogen ions, but also related to the antioxidant effect of organic acids, anions of acids and non-ionized molecules. Malic acid ionizes under neutral conditions and does not ionize under acidic conditions, but its bactericidal ability under acidic conditions is more than 100 times higher than that under neutral conditions, mainly because organic acids in molecular state are more likely to act through cell membranes, while acids in ionic state are less likely to penetrate cells. In addition, it can promote the thermal denaturation of protein.

Inhibition of enzymatic browning

Cutting vegetables is a new vegetable processing product emerging abroad, which is increasingly favored by people because of its convenience and quickness. Especially in the United States, it is estimated that by 2005, chopping vegetables will account for 30% of the total sales in the US retail market. Potato is an important cash crop in China, and its browning problem has attracted people's attention. Malic acid can reduce pH value, produce chelation, inhibit the activity of phenol oxidase and prevent browning. In addition, it also inhibits browning for other reasons.

Function 3: Deodorant

Used as deodorant, can remove fishy smell and body odor, and is used for food storage. Adding L- malic acid to milk can also improve the quality.

Function 4: Pasta fortifier

L- malic acid can strengthen tableware. It can increase disulfide bonds in gluten, make protein molecules bigger, form a macromolecular network structure, and enhance the air permeability, elasticity and toughness of dough. In addition, flour contains cysteine and cystine, which are protease activators. L- malic acid can make them lose the ability to activate protease and prevent protease from decomposing protein in flour. In addition, flour can be bleached to improve the binding effect of protein.

Function 5: Reduce salt

L- malic acid can be used to make salty food and reduce the amount of salt. For example, sodium malate is moderately salty and can often be used to make salty food. Malic acid can form many derivatives. In recent years, malic acid has been successfully applied to foods with reduced sugar and salt in Japan. When some malate is used to soak pickles instead of salt, its salty taste is only 1/5- 1/7, but the soaking effect is twice that of salt. At the same time, it can be used as a salt substitute for patients with nephritis. Adding calcium malate to soybean milk can effectively improve its taste and flavor.

Function 6: Protect vitamin C and keep color.

The hue of pigments contained in fruits and vegetables is often affected by pH value, and acid is often an important component in some discoloration reactions. For example, chlorophyll will turn into yellow-brown pheophytin under acidic conditions, anthocyanin will gradually change from red to purple when it changes from acidic to neutral, and tannin will form pink "red powder" under acidic conditions. Therefore, L- malic acid can be used as a color fixative for some foods, such as natural sherbet.

Function 7: Anti-oxidation and inhibition of oil rancidity.

L- malic acid has good antioxidant capacity. The oxidation of lipids in food will lead to rancidity, protein damage and pigment oxidation, which will reduce the sensory characteristics, nutritional value and shelf life of food. Adding food antioxidants can delay oxidation, prolong shelf life and maintain the color, fragrance and nutritional value of food.