Product name: Lactose

CAS: 63-42-3

Molecular formula: C12H22O11

EINECS: 200-559-2

Lactose Properties

Effects of lactose on the human body

Lactose only exists in the milk of mammals in nature. One molecule of lactose can be digested into one molecule of glucose and one molecule of galactose. Galactose can promote the production of cerebrosides and mucopolysaccharides, so it is very important for intelligence. In nature, only the milk of mammals contains lactose, and various plant foods do not contain lactose.

Disaccharides

Lactose is a disaccharide naturally found in mammalian milk. It is secreted by the mammary glands of mammals and only exists in the animal kingdom. The molecular formula is C12H22O11. It is a disaccharide composed of glucose and galactose, that is, the hydroxyl group on the fourth carbon atom of glucose and the β-histial hydroxyl group on the first carbon atom of galactose lose water to form a glycosidic bond. Therefore, the reducing property of the aldehyde group contained in the glucose molecule is still maintained. There are two isomers, α-type and β-type. The α-type lactose crystallized from the mother liquor below 93.5℃ contains one molecule of crystal water, a melting point of 202℃, a specific rotation of +88°, and a solubility of 7.4 grams. The β-type lactose crystallized above 93.5℃ has a melting point of 252℃, a specific rotation of +34°, a solubility of 55 grams, and no crystal water in the molecule. α-type sugar has low hygroscopicity and does not absorb external moisture in a high humidity environment, which is extremely important for controlling the activity of water in food.

In dehydrated milk and whey products, lactose often exists in amorphous crystals, has strong hygroscopicity, solubility of 20 grams (room temperature), and sweetness is only 30% of sucrose. It is not suitable for sweeteners and can only be used when making low-sweetness or special flavor foods. The lactose content in liquid whey is about 6.5%. After deesterification and clarification, it is concentrated at 55-60°C to make it solid, and the content can be increased to 55-65%. After cooling treatment, a large amount of crystals are obtained. After removing the mother liquor and washing the crystals, slightly yellow edible lactose can be obtained, and its purity can reach 99.6%. If recrystallization is performed, high-purity medical lactose can be obtained. The lactose content in human milk and cow's milk is 5-7% and 4% respectively. Lactose is often used in baby food. In the food industry, it is also widely used in beverages, Western sausages, sauces, instant foods, spice mixtures and meat products to supplement low sweetness, enhance aroma, extend sales period and increase product value. It can also be made into other derivatives (such as isoemulsified sugar) for processing different foods, and is also commonly used for making tablets.

Solubility

The solubility of lactose is lower than that of sucrose, and there is also a difference in the solubility of α-lactose and β-lactose. When lactose is put into water, part of it dissolves in water. The solubility when saturation is reached is the solubility of α-lactose, also known as the initial solubility. The initial solubility of lactose is low and is less affected by water temperature. When the saturated solution above is shaken or stirred, lactose can still be dissolved when added, and finally reaches the saturation point, which is the final solubility of lactose. Therefore, the final solubility of lactose refers to the equilibrium solubility of α-lactose and β-lactose at a certain temperature. The solubility of lactose increases with the increase of temperature and is greatly affected by temperature.

Chemical properties

White crystals or crystalline powder. Sweet, about 70% of the sweetness of sucrose. Odorless or slightly characteristic odor. Relative density d4201.525 (water-containing). Reducing and dextrorotatory. Divided into two isomers, α-type and β-type.

α-Lactose can be decomposed into glucose and galactose by acid and lactase, and can be transformed into lactic acid by lactic acid bacteria, but yeast cannot use it.

The crystals precipitated in water are monohydrate C12H22O11?H2O. If heated at 120℃, it can become anhydrous. The melting point of anhydrous is 201~202℃, 1g can be dissolved in 5ml water or 2.6ml hot water, slightly soluble in ethanol, and insoluble in ether.

β-lactose precipitates in hot water above 93℃, and its solubility is different from that of α-type. 1g is soluble in 2.2ml water or 1.1ml hot water. Melting point 252℃, optical rotation [α] D20 + 53.6°. It can be hydrolyzed into glucose and galactose in 2% sulfuric acid emulsion.

It only exists in animal milk, about 7% (5% to 8%) in human milk and about 4.5% (4% to 5%) in cow milk. At body temperature, it is mixed in a ratio of two parts α-type and three parts β-type to form an equilibrium state. Ordinary lactose products are α-type.

Incompatibility

Lactose reacts with primary amine compounds to form brown products. Amorphous lactose is more likely to undergo this reaction than crystalline lactose. Lactose is incompatible with amino acids, aminophylline, amphetamine, isoniazid, etc. When the prescription contains tartrate, citrate or acetate, etc., or under the influence of alkaline lubricants, the color change reaction can be accelerated.

Solubility in water

(g/100ml) Grams dissolved in 100ml water: 8g/20℃

Uses

Nutritional sweetener; excipient; dispersant; flavoring agent; nutrient. Mainly used as an adsorbent and dispersant for powdered food pigments to reduce pigment concentration, facilitate use and reduce discoloration during storage. Taking advantage of its easy compression and low water absorption, it is used as an excipient for tableting. Taking advantage of the low caramelization temperature of lactose (sucrose 163℃, glucose 154.5℃, lactose only 129.5℃), for some special baked foods, a darker yellow to caramel color can be obtained at a lower baking temperature. Other functions include preventing crystallization, reducing sweetness, preventing adhesion and enhancing flavor. Used in baby food, candy and margarine, etc.

Widely used in making baby food, candy, margarine, etc. It can also be used as culture medium, chromatography absorbent and excipient, etc.

Production method

It is obtained by heating or adding lime milk to whey (containing about 5% lactose) in milk, removing protein, concentrating, cooling, crystallizing and drying. The yield is about 60% to 70%.

Stability and storage conditions

It is easy to be infected with mold under humid conditions (humidity greater than 80%). With the extension of storage time, the color of lactose may change to brown, and the damp heat accelerates this change. α-lactose monohydrate is stable in the air and is not affected by moisture at room temperature, but the amorphous form of lactose may be affected by moisture and converted to monohydrate depending on its dryness. The monohydrate becomes anhydrous when heated to 120℃. The saturated solution of β-lactose may produce α-lactose crystal precipitation during storage, and the solution has mutarotation. Lactose should be placed in a sealed container and stored in a cool and dry place.

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