Lactose sweetness

Lactulose. 4-O-P -D-Galactopyranosyl-4-D-fmctofuranose [4618-18-2] (Chronolac) (12) may be made from lactose using the method described in Reference 9. It is a synthetic disaccharide that is not hydroly2ed by gastrointestinal enzymes in the small intestine, but is metabolized by colonic bacteria to short-chain organic acids. The increased osmotic pressure of these nonabsorbable organic acids results in an accumulation of fluid in the colon. Lactulose may not be tolerated by patients because of an extremely sweet taste. It frequently produces flatulence and intestinal cramps. 

Uses of lactose production by appHcation include baby and infant formulations (30%), human food (30%), pharmaceuticals (25%), and fermentation and animal feed (15%) (39). It is used as a diluent in tablets and capsules to correct the balance between carbohydrate and proteins in cow-milk-based breast milk replacers, and to increase osmotic property or viscosity without adding excessive sweetness. It has also been used as a carrier for flavorings. 

Lactose occurs in milk, mainly free, but to a small extent as a component of higher oligosaccharides. Cow and goat milks contain about 4.5% lactose human milk contains about 7.0%. Lactose is used as an excipient in tablets to provide bulk and rapid disintegration. It is also used in some food products where it contributes body with only about 40% the sweetness of sucrose and enhances colors and flavors. 

Whey is the fluid obtained by separatiag the coagulum from cream and/or skim milk, and is a by-product of either caseia or cheese manufacture. The composition of whey is determined by the method of curd formation, curd handling practices, and methods of handling whey as it is separated from the curd. Dried acid whey contains ca 12.5 wt % proteia (total nitrogea x6.38), 11.0 wt % ash, and 59 wt % lactose, whereas sweet whey contains 13.5 wt % proteia, 1.2 wt % fat, 8.4 wt % ash and 74 wt % lactose. The composition varies with the type of acid used (7). 

Whey has been used ia some substitute dairy products but aot as a source of proteia. Whey proteias have beea used ia dairy substitutes only siace the commercialisation of ultrafiltration (qv) technology. Membranes are used that retain proteia and permit water, lactose, and some minerals to pass through as permeate. Proteia coaceatrates are available from both acid and sweet whey and ia coaceatratioas of 35—80 wt % proteia. Whey proteia isolates are commercially available having proteia >90 wt%. The cost of these isolates is too high, however, to make them economical for substitute dairy foods. 

Disaccharides like maltose, lactose, and trehalose are used for their similarity to sucrose, but with differences in some properties, such as sweetness, melting point, or hygroscopicity. 

It is puzzling that the chlorine and other halogen substituents are not known to enhance the sweetness of other sugars, such as methyl -d-glycopyranosides, a,a-trehalose, maltose, or lactose. On the contrary, all of the deoxyhalo sugar derivatives tasted were extremely bitter. The high sweetness of the deoxyhalosucroses is clearly inexplicable in terms of either... 

Another established application in the dairy industry is the hydrolysis of lactose in milk and whey by lactases. Diminished digestibility problems, increased sweetness and prevention of lactose-crystal formation are the results. The lactose hydrolysis is worked out as a case later in this chapter (section 3.6). 

By pre-treating milk with lactase, all adults can enjoy milk and a whole range of other lactose-free dairy products can be made such as ice cream and yogurt. In the production of ice cream, lactose hydrolysis can also be used to improve certain properties such as the texture, sweetness and tendency to crystallize. The increased sweetness is also advantageous in the manufacture of flavored milk products because less sugar needs to be added. 

The hydrolysis of lactose conveys a number of desirable properties to whey—increased sweetness for one. Lactase-treated whey can be used as a sweetener in various foods such as ice cream, bakery products, beverages and corrfectionery. This treatment can save large qrrantities of whey from going to waste and presenting a potential pollution hazard. 

Lactose has a sweetish taste, and is used extensively in the pharmaceutical industry. It is the second most widely used compound and is employed as a diluent, filler or binder in tablets, capsules and other oral product forms, a-lactose is used for the production of lactitol, which is present in diabetic products, low calorie sweeteners and slimming products. As lactose is only 30 per cent as sweet as sugar it is used as a sugar supplement, and also in food and confectionery. It is used in infant milk formulas. 

Figure 2.15 Schematic representation of plant for the manufacture of crude and refined lactose, from sweet whey.

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. 

The glucose moiety can be isomerized to fructose by the well-established glucose isomerization process to yield a galactose-glucose-fructose syrup with increased sweetness. Another possible variation would involve the isomerization of lactose to lactulose (galactose-fructose) which can be hydrolysed to galactose and fructose by some / -galactosidases. 

Lactitol. Lactitol (4-0-/ -D-galactopyranosyl-D-sorbitol), is a synthetic sugar alcohol produced on reduction of lactose, usually using Raney nickel. It can be crystallized as a mono- or di-hydrate. Lactitol is not metabolized by higher animals it is relatively sweet and hence has potential as a non-nutritive sweetener. It is claimed that lactitol reduces the absorption of sucrose, blood and liver cholesterol levels and to be anticariogenic. It has applications in low-calorie foods (jams, marmalade, chocolate, baked goods) it is non-hygroscopic and can be used to coat moisture-sensitive foods, e.g. sweets. 

Acidophilus milk is a sharp, harsh, acidic cultured milk produced by fermenting whole or skim milk with active cultures of Lactobacillus acidophilus. Honey, glucose, and tomato juice may be added as nutrients to stimulate bacterial growth and contribute flavor. Plain acidophilus milk has the same composition as whole milk or skim milk, except that part of its lactose is converted to 0.6 to 1% lactic acid by the culture organisms. Speck (1976), who proposed the addition of L. acidophilus to pasteurized milk (sweet acidophilus milk), described the beneficial effects of implanting the organisms in the human intestines. 

Lactose is the characteristic carbohydrate of milk, averaging about 4.9% for fluid whole cow s milk and 4.8% for sheep and goat s milk. The commercial source of lactose today is almost exclusively sweet whey, a by-product of cheese making. Details of its production are given in Chapter 6. 

Relative Sweetness. It has been amply demonstrated that the relative sweetness of sugars changes with the concentration. Therefore it is misleading to say that one sugar is so many times as sweet as another, because this will be true only at certain concentrations. Table 6.5 summarizes results on the relative sweetness of some common sugars. It should be noted that lactose is relatively sweeter at higher concentrations than at lower concentrations and is sweeter than is usually reported in reviews of food applications. 

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