Lactose

8 Key excerpts on "Lactose"

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  Dairy Science and Technology

  • P. Walstra, Pieter Walstra, Jan T. M. Wouters, Tom J. Geurts(Authors)
  • 2005(Publication Date)
  • CRC Press

    (Publisher)

  Lactose can be separated from milk or, in industrial practice, from whey, by letting it crystallize. Crystalline Lactose is produced in large amounts, and it is mainly used in foods and in pharmaceuticals; nearly all pills contain Lactose as a filling material. Lactose is also used as raw material for a range of chemical or enzymatic derivatives, such as lactitol, lactulose, and oligosaccharides. 2.1.1 C HEMICAL P ROPERTIES Lactose is a disaccharide composed of D -glucose and D -gaLactose. The aldehyde group of gaLactose is linked to the C-4 group of glucose through a β -1, 4-glycosidic linkage (Figure 2.1). Both sugar moieties occur predominantly in the pyranose ring form. Chemical reactions of Lactose involve the hemiacetal linkage between 18 Milk Components C 1 and C 5 of the glucose moiety, the glycosidic linkage, the hydroxyl groups, and the –C–C– bonds. Furthermore, Lactose is a reducing sugar . As shown in Figure 2.1, the O–C 1 bond in the glucose moiety can break, leading to an open-chain form that has an aldehyde group. It is also shown that conversion of the α -anomer into the β -anomer, and vice versa, does occur via the open-chain form. This phenomenon is called mutarotation. Presumably, less than 0.1% of the Lactose in fresh milk is in the open-chain form. At high temperatures, and also at high pH values, this is a much higher proportion, say, between 1 and 10%. Because the aldehyde group is by far the most reactive one of Lactose, this means that the reactivity of the sugar then is greatly enhanced. Suitable reagents or enzymes can cause mild oxidation of Lactose, whereby the aldehyde group is converted to a carboxyl group. Somewhat more vigorous oxidation ruptures the glycosidic linkage and produces carboxyl groups in the remaining sugars. Gentle reduction of Lactose converts the aldehyde group to an alcohol group. More intense reduction cleaves the glycosidic linkage and results in the formation of alcohol groups in the remaining sugars.

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  Dietary Sugars

  Chemistry, Analysis, Function and Effects

  • Victor R Preedy(Author)
  • 2012(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  Lactose is a disaccharide derived from the condensation of D-gaLactose and D-glucose, which form a b -1 -4 glycosidic linkage (Figure 47.1). Its sys-tematic name is b -D-galactopyranosyl-(1 -4)-D-glucose. The glucose can be in either the a -pyranose form or the b -pyranose form, whereas the gaLactose can 822 Chapter 47 only have the b -pyranose form: hence a -Lactose and b -Lactose refer to anomeric form of the glucopyranose ring alone. Two isomers of Lactose exist a -Lactose and b -Lactose, which differ in their specific rotation to polarised light, ( þ 89.4 1 or þ 35.0 1 , respectively, in water at 20 1 C), in their melting point and their solubility in water etc. The most stable form is a -Lactose monohydrate, C 12 H 22 O 11 H 2 O and the ratio of isomers is temperature dependent. The solubility and sweetness of Lactose is low compared to other sugars (1/6 in relation to sucrose) (Ga¨ nzle et al . 2008). In general, there are considerable differences in composition and properties of milk from the four main milk-producing species, such as cows, sheep, goats and buffalos (Table 47.1). Indeed, bovine, ovine and buffalo milk contain B 4.8 g Lactose 100 g 1 , whereas caprine milk generally contains a lower level of Lactose (Harper 1992). In the milk of some mammals, such as sea lions, some seals and opossums, Lactose is absent, or only present in very low concentra-tions (Jenness and Holt 1987). Lactose is responsible for B 50% of the osmotic pressure of milk, which is equal to that of blood. In bovine milk, the con-centration of Lactose decreases progressively and significantly with lactation stage, and with increasing somatic cell count of the milk (Walstra and Jenness 1984) – in both cases due to the influx of NaCl from the blood and the resultant need to maintain the osmotic equilibrium (Fox 2003).

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  Ultra Performance Liquid Chromatography Mass Spectrometry

  Evaluation and Applications in Food Analysis

  • Mu Naushad, Mohammad Rizwan Khan(Authors)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  Lactose makes up around 2~8% of milk (by weight), although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from lac , or lactis , the Latin word for milk, plus the “ose” ending used to name sugars. Lactose is the main car-bohydrate in dairy products. This disaccharide is composed of glucose and gaLactose and is the only saccharide synthesized by mammals. Lactose plays an important role in the formation of the neural system and the growth of skin (texture), bone skeleton, and cartilage in infants. It also prevents rickets and saprodontia [1]. The need to quantify Lactose came up with the knowledge of its importance in the human diet. It has been reported that cow mastitis can cause a reduction of milk yield and also of its nutritive value. Determination of the Lactose content is one of the methods used to evaluate whether milk is acceptable for human consumption [2]. Moreover, the precise control of the amount of Lactose in dairy food products is vital, as many people are intolerant to this carbohydrate. Therefore, the precise determination of Lactose during the production process, as well as in the final product, is fundamental for the food industry. It also has economic value since the price of milk is based on HO O O OH OH OH OH O OH HO HO FIGURE 15.1 Structure of Lactose. 391 UPLC–MS and Its Application milk solids content. The Lactose content of cow milk can vary from 3.8% to 5.3% (38,000–53,000 μ g/mL). Modern 1% and 2% milk have higher levels of Lactose. The Association of Official Agricultural Chemists (AOAC) official method (984.15) for Lactose in milk is both complex and time consuming. It involves enzymatic hydroly-sis of Lactose to glucose and gaLactose at pH 6.6 by β -galactosidase [3]. Subsequent oxidation of the β -gaLactose released to galactonic acid at pH 8.6, as catalyzed by β -gaLactose dehydrogenase, then occurs with concomitant reduction of nicotinamide adenine dinucleotide (NAD + ).

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  Sweeteners

  Nutritional Aspects, Applications, and Production Technology

  • Theodoros Varzakas, Athanasios Labropoulos, Stylianos Anestis(Authors)
  • 2012(Publication Date)
  • CRC Press

    (Publisher)

  The solubility of Lactose is less than that of most other sugars, which may present problems in a number of foods containing Lactose (Izydorczyk 2005). Finally, like all reducing sugars, Lactose can undergo Maillard (nonenzymatic browning) reaction, resulting in (off-) flavor compounds and brown poly-mer production (Fox 2009). Maltose : Maltose is a disaccharide formed from two units of glucose joined with an α -(1 → 4) glycosidic bond (Figure 2.18). It rotates the plane-polarized light to the right and has a specific optical rotation of [ ] α D ° 20 136 = + . Maltose is the major end product of the enzymatic degradation of 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 Solubility (g anhydrous Lactose/100 g water) Temperature (°C) Usual range of supersaturation 93.5°C Initial solubility of β-Lactose Initial solubility of α-Lactose Final solubility at equilibrium Figure 2.17 Solubility of α - and β -Lactose as a function of temperature. (Adapted from Fox, P. F. and McSweeney, P. L. H., Dairy Chemistry and Biochemistry , Chapman & Hall, London, 1998.) CH 2 OH CH 2 OH OH OH H H H H H H H O OH H H O O O H H OH OH Figure 2.18 Structure of maltose. 25 CHEMISTRY AND FUNCTIONAL PROPERTIES OF CARBOHYDRATES AND SUGARS starch by maltases, and it has a characteristic flavor of malt. It is a readily yeast-fermentable sugar, reduces Fehling’s solution, is easily soluble in water and slightly soluble in ethanol, and presents mutarotation (deMan 1999). Cellobiose : Cellobiose is a reducing disaccharide formed from two units of glucose joined with a β -(1 → 4) glycosidic bond (Figure 2.19). It can be obtained by enzymatic or acid hydrolysis of cel-lulose. Cellobiose is differentiated from maltose in the kind of glycosidic bond between the glucose units. It is enzymatically hydrolyzed by the enzyme emulsine (deMan 1999). 2.4.2 Trisaccharides and Tetrasaccharides The most important trisaccharide is raffinose that is composed of gaLactose, glucose, and fruc-tose (Figure 2.20).

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  Lactose

  Evolutionary Role, Health Effects, and Applications

  • Marcel Paques, Cordula Lindner(Authors)
  • 2019(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 6

  Lactose in the dairy production chain

  Kasper A. Hettinga,    Dairy Science & Technology, Food Quality & Design Group, Wageningen University & Research, Wageningen, The Netherlands

  Abstract

  Lactose, the main carbohydrate in milk, is a unique sugar produced in the mammary gland of mammals. Lactose is synthesized in the mammary gland of cows from its precursor glucose. Lactose, being a main determinant of the osmotic pressure of milk, drives the milk yield of cows. The Lactose produced in the mammary gland is the main carbohydrate in the newborns’ diet and an important source of energy. Compared to other sugars, Lactose has many specific physical and chemical properties, such as its relative low solubility and specific crystallization behavior. In other aspects, it is similar to other reducing sugars, for example, as reactant in the Maillard reaction. These physical and chemical properties of Lactose play a major role in the properties and quality of many dairy products and dairy-based ingredients. It is the energy source for the lactic acid bacteria used during fermentation, and its breakdown leads to the formation of specific flavor components in such fermented products. In concentrated and dried dairy products, the concentration of Lactose becomes so high that many of the properties of the product are determined by Lactose. In addition to playing a role in dairy consumer products, Lactose can also be present in, or form the basis of several, dairy-based ingredients. Many dairy-based ingredients are based on whey and therefore rich in Lactose. From such streams, it can be isolated for direct use in, for example, animal feed or pharmaceutical applications, and it can also be chemically converted into many Lactose-derived components, which have very different functionalities. Lactose, in both dairy products and other food products containing dairy-based ingredients, is important from consumer perspective as well. Finally, at the end of this chapter, a perspective is given on future research needs with regard to Lactose in the dairy chain, from primary production to the consumer level.

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  Penta- and Higher Polyhydric Alcohols, Their Oxidation Products and Derivatives, Saccharides

  A Modern Comprehensive Treatise

  • S. Coffey(Author)
  • 2013(Publication Date)
  • Elsevier

    (Publisher)

  Octa-acetate, m.p. 176-178 0 , [ ] +153° (chloro-form) . 2-O-β-Ό-Galactopyranosyl-O-glucose, monohydrate, m.p. 175 0 (decomp.), [OC]D +48° — > +39 · 3° (water, calculated on an anhydrous basis), has been synthesised by Königs-Knorr type condensations (Beck and K. Wallenfels, Ann., 1962, 655, 173). See also A. M. Gakhokidze, Soobshcheniya Akad. Nauk Gruzin, S.S.R., 1948, 9, No. 9/10, 561; CA., 1956, 50, 10657. 3-O-ß-O-Galactopyranosyl-O-glucose, monohydrate, m.p. 202-204°, [a] 0 + 7 6 -7 —>+4i-2° (water), is prepared by the condensation of tetra-0-acetyl-a-D-galactopyranosyl bromide and 1,2-5,6-di-O-isopropylidene-a-D-glucofuranose (R. Kuhn and H. H. Baer, Ber., 1954, 87, 1560). Phenylosazone, m.p. 184-185°. Lactose, 4-O-ß-O-galactopyranosyl-O-glucose, m.p. 252 0 , [ + 55*4° (water), monohydrate, m.p. 202 0 , [ +55*4° (water). For a review of the chemistry and biochemistry of Lactose see / . R. Clamp et al., Adv. Carbohydrate Chem., 1961, 16, 159. Lactose occurs in the milk of mammals, both free and in the form of Lactose-containing oligosaccharides. The concen-tration present varies from about 2% to 9%. It also occurs in a number of fruits and in the pollen of the Forsythia plant. Crystals of Lactose are gritty to the tongue, and only faintly sweet. The disaccharide is readily converted to lactic acid by the lactic bacillus, this process being responsible for the souring of milk. The proof of the constitution of Lactose is of historical interest. That the gaLactose moiety is in the non-reducing part of the molecule was shown by the hydrolysis of lactobionic acid to gaLactose and gluconic acid, by the hydrolysis of the Lactose carboxylic acid formed by the Kiliani reaction to glucoheptonic acid and gaLactose (Ann., 1893, 2 7 2 > τ 9%) a n d by the hydrolysis of lactosone to gaLactose and glucosone (E. Fischer, Ber., 1888, 21, 2633).

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  Organic Chemistry

  • David R. Klein(Author)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  Several dairy products are produced via processes that remove the Lactose, and these products are marketed as being “Lactose free.” In addition, the enzyme lactase is available in tablet form without a prescription and can be taken prior to eating any products containing Lactose. Lactose Intolerance Medically Speaking Sucrose Sucrose, commonly referred to as table sugar, is a disaccharide comprised of glucose and fruc- tose linked at C1 of glucose and C2 of fructose. Hydrolysis of sucrose yields glucose and fruc- tose. Honeybees have enzymes that catalyze this hydrolysis, allowing them to convert sucrose into honey, which is primarily a mixture of sucrose, glucose, and fructose. Honey is sweeter than table sugar, because fructose is sweeter than sucrose. Unlike the other disaccharides we have seen thus far, sucrose is not a reducing sugar and does not undergo mutarotation. This can be explained by noting that sucrose is comprised of two units that are linked to each other via their anomeric positions. As such, neither unit has a hemiacetal group and neither unit is capable of adopting an open-chain form. HOCH 2 O HO HO O OH CH 2 OH OH OH O OH 1 2 Glucose (α-pyranose form) Fructose (β-furanose form) Sucrose (a 1 2 glycoside) 1132 CHAPTER 24 Carbohydrates Artificial Sweeteners Practically Speaking A variety of health problems have been associated with excessive consumption of sucrose, including diabetes and tooth decay. These issues, together with the desire of many people to reduce their caloric intake, have fueled the development of many artificial sweeteners, such as the following compounds.

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  Food Science

  Research and Technology

  • A. K. Haghi(Author)
  • 2011(Publication Date)
  • Apple Academic Press

    (Publisher)

  Lactose, a disaccharide, can also be named as lactase, an enzyme of the β -galactosidases group that acts to hydrolyse this sugar. RAFFINOSE FAMILY OF OLIGOSACCHARIDES The raffinose family of oligosaccharides or α -galactosides belongs to compounds widespread in the higher plants. Large amounts of them occur in plants where they constitute the main fraction of water soluble carbohydrates. These oligosaccharides are very important components of the carbohydrates reserve in the vegetative storage organs and seeds of many plants and they play various physiological functions (Musquiz et al . , 1999) comprise 30–80% of the total soluble sugars. The raffinose family of oligosaccharides has a more definitive antinutritional effect (Deshpande, 2002). The absence of the α -galactosidase enzyme in the low gastroin-testinal tract (responsible for the hydrolysis of α -1, 6 galactosides linkages) and its accumulation in the large intestine, results in the fermentation by anaerobic bacteria (Fleming, 1981). It is the behavior that produces the flatulence for which the consump-tion of this oligossacharides is noted (De Lumen, 1992; Viana et al., 2005). The ac-cumulation of flatus in the intestinal tract results in discomfort, abdominal rumblings, cramps, pain, and diarrhoea and is characterized by the production of hydrogen, car-bon dioxide, and small amounts of methane gas. Sugars of the raffinose family are believed to be largely responsible for the often reported problem of flatulence after consumption of diets containing beans and other legumes. The raffinose family of oligosaccharides is represented by the predominant oli-gossacharide stachyose (tetrassacharide), followed by raffinose (trissacharide) and verbascose (pentassacharide), depending on the type of grain (FAO, 1998; Petterson Advances and Applications of Galactosidases in Food Industry 59 and Mackintosh, 1994).

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