Lactose syrup production

A plethora of lactase-treated products are described in the literature (Zadow 1984 Holsinger 1978). The use of hydrolyzed lactose syrups has been proposed as an alternative sweetener to corn syrup solids. Storage of syrups as concentrated liquids can be a problem due to microorganism growth or to extensive precipitation of residual lactose or galactose. Generally, both problems can be controlled by storage at -10 to -20°C if syrup total solids were around 70%. Guy (1979) has reported on the sweetness of hydrolyzed, demineralized syrups. 

Saccharic acid. Use the filtrate A) from the above oxidation of lactose or, alternatively, employ the product obtained by evaporating 10 g. of glucose with 100 ml. of nitric acid, sp. gr. 1 15, until a syrupy residue remains and then dissolving in 30 ml. of water. Exactly neutralise at the boiling point with a concentrated solution of potassium carbonate, acidify with acetic acid, and concentrate again to a thick syrup. Upon the addition of 50 per cent, acetic acid, acid potassium saccharate sepa rates out. Filter at the pump and recrystaUise from a small quantity of hot water to remove the attendant oxahc acid. It is necessary to isolate the saccharic acid as the acid potassium salt since the acid is very soluble in water. The purity may be confirmed by conversion into the silver salt (Section 111,103) and determination of the silver content by ignition. 

Some individuals are unable to metabolise lactose and are lactose intolerant. This is because they lack the enzyme lactase that is needed to metabolise lactose. Lactose intolerance is common in those parts of the world where humans do not consume any dairy products after weaning. In practice this means in Asia, which means that most of the world s population might be lactose intolerant. It is possible to produce lactose removed skim milk. Another approach with lactose is to hydrolyse it to its constituent monosaccharides. As well as avoiding lactose intolerance this allows a syrup to be produced from cheese whey. These syrups are offered as an ingredient for toffees and caramels. 

Another reason for the reduced use of milk powder is the availability of substitute ingredients such as lactose, whey powder or syrups and speciality milk powder replacers. The speciality milk powder replacers are produced by the dairy industry from milk or whey components, combining them to produce a product that will act as a substitute for milk powder but is less expensive. 

In comparison with sucrose (the annual production of which is 93 x 106 tonnes) and glucose or glucose-fructose syrups, only relatively small quantities of lactose are produced. However, it attracts commercial interest because it has some interesting properties and is readily available from whey, a by-product in the production of cheese or casein. World production of cheese is c. 1.4 x 107 tonnes, the whey from which contains c. 6 x 106 tonnes of lactose c. 0.3 x 106 tonnes of lactose are contained in the whey produced during casein manufacture. According to Horton (1993),... 

Glucose-galactose syrups are about three times sweeter than lactose (70% as sweet as sucrose) and hence lactose-hydrolysed milk could be used in the production of ice-cream, yoghurt or other sweetened dairy products, permitting the use of less sucrose and reducing caloric content. However, such applications have not been commercially successful. 

Lactose hydrolysis with immobilized systems is the method of choice when regular production of hydrolyzed syrups on a large scale is required. The best-known of these is the Corning immobilized system, which uses lactase from Aspergillus niger covalently bound to a controlled-pore silica carrier. The particle size is 0.4 to 0.8 mm, the wet bulk density is 0.6, the activity is near 500 U/g at 50°C, and the optimal pH of operation is between 3.2 and 4.3. Estimated laboratory life is 2 years (Dohan et al. 1980). There are at least two of these plants in commercial operation, one in the Untied States and one in the United Kingdom, each a joint venture with Corning. 

However, for economy of production, maximum yields of alkaloids, and ease of recovery of the products, certain culture media containing relatively simple nutrient sources are preferred. For example, the media which are useful in the production of the alkaloids include an assimilable source of carbon such as glucose, sucrose, starch, molasses, dex-trins, corn steep solids, corn syrup liquor, sorbitol, mannitol, lactose, and the like. A preferred source of carbon is mannitol. Additionally, the media employed contain a source of assimilable nitrogen such as oatmeal meat extracts, peptones, amino acids and their mixtures, proteins and their hydrolysates, com steep liquor, soybean meal, peanut meal and ammonium salts of organic acids such as the citrate, acetate, malate, oxalate, succinate, tartrate and like salts. 

The production of sweet whey syrups is becoming increasingly important due to the use of carrier-bound lactase (P-galactosidase, EC. 3.2.1.23). In these syrups, lactose is hydrolyzed to glucose and galactose. Concentration to 60-75% solids is achieved by evaporation. 

---