BY-PRODUCTS TECHNOLOGY

Module 3. Processing and utilization of whey

Lesson 36
USES OF LACTOSE

36.1 Introduction

Lactose, a milk carbohydrate, has high nutritional value and is mainly used as constituent of foods and medicinal products. Lactose has various applications in food and pharmaceutical industries due to its multifunctional properties. In countries, such as New Zealand, where the lactation of the national herd is largely synchronized to match seasonal grass availability, the protein content of milk powder fluctuates markedly throughout the year. The addition of lactose to standardize protein level is now permitted, provided that the adjustment does not alter the whey protein to casein ratio of the milk being adjusted. Standardization of milk for protein as well as fat levels is being introduced within Europe also. This, at times, has resulted in a great demand for lactose causing a worldwide shortage. This effectively means that lactose has an inherent value approaching that of skim milk powder.

A significant part of the supply of lactose (approximately 80%) goes into food applications such as infant formula, meat products, confectionery and bakery products, and the remaining lactose primarily goes into different pharmaceutical products. Lactitol production is showing interesting new application opportunities and significant annual growth rates. In the last decade, a number of consumer products have been launched containing lactose ingredients, the new products during 2004-06 are illustrated in Fig. 36.1. The market for lactose ingredients is likely to be strengthened as the dairy industry focuses more on healthy and nutritional products. Much current research is being carried out in the area of lactose derivatives, with the aim of producing high-value neutraceuticals. This is area in which more commercial activity is likely to be seen and if it works, then it will be another driver in increasing the price of lactose. Lactulose, a derivative of lactose is used in the treatment of tumors.

36.2 Properties of Lactose Providing Basis for Its End Uses

Lactose has various applications in food and pharmaceutical industries due to its multifunctional properties:

36.2.1 Relative sweetness and solubility

Lactose is less sweet than sucrose, it can be used in foods such as icing, toppings and fruit pie added to filling to increase the total solids without excessive sweetness.

36.2.2 Reducing properties

Lactose is a reducing sugar and can react with proteins, peptides and amino acids to form brown pigments. Hence, it is used for controlled browning in the food industry, especially in baked goods.

36.2.3 Protein stabilizing properties

Lactose protects the solubility of the caseinate complex in milk during spray drying. In absence of lactose, the caseinate complex loses approximately half of its capacity to redisperse.

36.2.4 Influence on crystallization habits

The crystallization of lactose in ice cream and sweetened condensed milk constituted a defect if the crystals are large enough to provide a sandy or gritty texture. This can be avoided by seeding with fine lactose powder or rapid agitation of the mix to alter the crystallization habit of lactose.

36.2.5 Absorptive properties

Lactose absorbs flavors, aroma and coloring materials. The absorptive capacity of anhydrous lactose offers a great potential for foods, whereas, retention of volatiles is desirable, such as in coffee. It is also useful in trapping and removing undesirable volatile flavour through filtration.

36.2.6 Dispersing properties

The non hygroscopic and free flowing nature of µ-lactose offers wide potential in the food and pharmaceutical industry as a dispersing agent.

36.3 Applications and Uses of Lactose

Sweetness reduction, consistency improvement in confectionary & bakery goods, as carrier & anti caking agent in powder foods, carrier for tablets, controlled browning in bakery goods, flavor enhancer in sauces & dressings, nutritional importance in infant formulas etc, are some of the desirable functional properties and application of crystalline lactose powder.

36.3.1 Pharmaceutical products

Pharmaceutical grade lactose is widely used as diluents, filler, bulking agent and expecipient in tablets, drugs, capsules, pills, powders and other oral forms, of which tablets are most important in its purified form. Lactose is best carrier for tablet making. In capsules, it is filled along with the active materials and used as a coating agent for pills and tablets. Many of the properties of crystallized lactose make it suitable for tableting. It is a known fact that most active ingredients can’t be used in the form in which they have been obtained by the isolation of chemical synthesis. A drug can only be effective if it is released under proper conditions. A drug may be distributed uniformly in powdered lactose, which is then moulded or compressed into tablets. Other tablets may be given a lactose shell by first wetting the tablet surface with a small amount of coating syrup, and then tumbling the wetted pill in lactose powder. The coating seals in the contents, but is easily handled and readily dispersible. A series of different lactose products are available to provide a range of granular distribution, free flowability, bulk density and avoiding segregation of mixtures to meet the growing demands of the pharmaceutical industry. These products include those that offer directly compressible properties, eliminating the need for tablet producers to use the costly wet granulation process. In homeopathic medicines, lactose is used in making bio-chemic tablets and mixtures.

36.3.2 Confectionery products

The confectionery industry uses lactose in certain types of candies because it changes the crystallization behaviour of other sugars present and improves body, texture, chewiness and shelf-life. It can be added to fondants at 20% level to reduce sweetness without affecting other product characteristics.

Reduced sweetness, fortification of aroma, improved colour binding, better mouth feel and improved shelf life are the major reasons for using lactose (along with sucrose, dextrose and fructose) in confectionery products. In chocolate and sugar confections especially, lactose is a well established ingredient. The delayed crystallization brought about by the addition of lactose to concentrated sucrose solutions is useful in the coatings of various candies. It is particularly beneficial in caramels and fudges to improve body, texture, chewiness or shelf life.

36.3.3 Bakery products

In the baking industry, lactose can enhance the creaming properties of shortenings to improve product quality, facilitate baking operations, gives increased loaf volume and external appearance score and extend shelf-life, apparently by minimizing starch retrogradation. It can provide better elasticity to the gluten during heating, resulting in better crumb development, crumb stability and pastry volume. In addition, advantage is taken of the ability of lactose to participate in the Maillard reaction which improves browning and flavour of many baked products. The reducing and unfermentable nature of lactose offers unique characteristics to the baking industry. The addition of lactose increases the browning of the crust, which is often highly desirable. Since lactose is not fermented, the functional properties provided by the addition of lactose are not lost during manufacture (Zadow, 1984). The improvement provided by lactose in the emulsifying properties of shortenings result in uniform cell structure and desirable texture, thus promoting good distribution of shortening with minimal mixture. This is of particular value in making pie crusts, which are more tender and shorter, sheet out better and shrink less (Webb and Whittier, 1970). Cake batter containing 10-15% lactose on a replacement basis creamed better and yielded better volume, grain and texture.

Cookie and doughnut doughs made with lactose can be machined rapidly, are easily released from the moulds and retain their shape better in baking. Also, batters show more tolerance to variations in mixing and processing. The chemical reducing power of lactose is less than that of glucose. Therefore lactose can replace glucose in foods in warmer climates.

36.3.4 Meat and sausage products

In the meat and sausage industry, lactose may be added to raw sausage formulation as a carbohydrate source for fermentation by selected starter cultures to produce lactic acid for preservation in dry sausage types, such as salami. Lactose also contributes to controlled browning of these products due to maillard reactions and acids in masking off-flavours and after-tastes caused by emulsifying salts, phosphates and other bitter compounds.

36.3.5 Health foods

The most recent application for lactose and its derivatives is in the formulation of ‘nutraceutical’ health foods, believed by many to enhance health and well-being if not actually preventing the development of certain diseases, especially in Japan. Due to its slower rate of hydrolysis and absorption, lactose has little influence on the blood-glucose level and therefore is less burdening for diabetics than sucrose. Also for sportsmen this is a positive item. Lactose is a long lasting source of carbohydrate, independent of the insulin system. Long-endurance foods reformulated with high protein and lactose contents.

36.3.6 Baby/Infant foods

Bovine milk differs from human milk in several aspects. Human milk contains higher concentration of lactose than bovine while mineral load is less. For humanization of infant formulations lactose is to be adjusted to meet the intestinal requirement of the infants. A major use of lactose is in humanized infant formulae, where it is used to correct the balance between carbohydrate and protein in human milk replacers based on cow’s milk. Due to its relatively slow digestion, energy is provided to the infant over a period of several hours. Because of its bifidogenic activity, it is viewed as being necessary for the establishment of a healthy intestinal flora. Finally, lactose impacts on mineral absorption, enhancing absorption of calcium, magnesium and possibly zinc, perhaps by increasing the permeability of the villus membrane of the intestine. Lactose is also used for fortification of baby foods.

36.3.7 Instant powdered foods

Lactose is used as an additive to improve the free-flow properties of powdered foods. Lactose glass is used in the instantizing process to increase the dispersibility of such foods as instantized spray dried milk powder by crystallizing to form agglomerates. These products are free flowing and capable of dispersing rapidly, similar to instant milk powders. The hygroscopicity of lactose has been used for adsorbing the free moisture in low moisture foods and fixing it as water of crystallization. One example is the coating of food particles with a liquid flavouring and colouring material and tumbling the product in powdered lactose glass, which absorbs surface moisture and forms a capsule around the food particles.

36.3.8 Instant soups and sauces

Lactose is added to salad dressing, mayonnaise, soups and sauces to enhance flavour and confer added stability to various proteins in the formulations against flocculation at acid pH and pasteurization. Because of its properties as a free-flow agent, lactose may be added to instant powdered soups and sauces.

36.3.9 Beverages

Lactose can be used to increase viscosity, improve mouth-feel and flavor without making the product too sweet. The acceptability of milk as a beverage, especially skimmed milk, may be attributed in part to lactose. As a supplement in skimmed milk, butter milk or chocolate drink, it improves smoothness and mouth-feel, adds richness and enhances acceptance. Further, the addition of 1% lactose of milk chocolate drinks allowed the reduction of butter fat from 2 to 1%, while retaining the same richness in flavour. It has also been used in beer manufacture because it is not fermented by the yeast and remains in the finished product to increase viscosity and improve mouth-feel and flavor. It has similar uses in other beverages.

36.3.10 Other uses

Lactose acts as a stabilizer for proteins in acid fermented products, in frozen milk and in high protein milk powders and milk based coffee whiteners. Addition of lactose can improve the mouthfeel of low fat foods and impart a full flavor. Lactose is also a carrier for artificial sweetners such as aspartame and saccharine. In freeze dried solutions, lactose increase plug size and aid caking. In sugar coating solutions, it is used in combination with sucrose. Lactose also Improves flavor of raw fish.

Lower solubility of lactose than that of sucrose can be very helpful in special applications. For example hard boiled sweets often have a tough structure if glucose syrup is used as a crystallization retarder, replacing tartaric acid. In these products the original brittleness can be regained by the addition of finely ground lactose.

Other uses of lactose include its use as a substrate in the production of materials such as penicillin and other fermentation products. The use of lactose in fermentation broths offers advantages owing to the delayed decomposition of the lactose. Further, supersaturated lactose has been used as a binder in making salt-lick blocks for cattle.

Selected references

Singh, S. and Rai, T. 1989. Potential uses of lactose in food industry. Indian Dairyman, 41 (7): 369-382.
Jindal, J.M. 1989. Utilization of lactose in pharmaceutical industry. Indian Dairyman, 41 (7): 127-129.
Zadow, J.G. 1984. Lactose: properties and uses. J. Dairy Sci., 67: 2654-2679.