Pectins dehydration

Lactic acid is used in the jams, sweets, and drinks industries. This acid is the best acid to control the acidity and assure the transparency of brine in pickles. Calcium lactate can be used as a taste enhancer, as a baking processing aid, to proof the dough, as an inhibitor of decolorization of fruits and vegetables, as a gelatinization factor during pectins dehydration, or as an improver of the properties of milk powder or condensed milk. The ethyl esters of lactic acid can be used to enhance taste. Calcium lactate can be nsed in dietetic foods as weU as nutrition supplements (Table 13.4). 

The structural features of ceU wall polysaccharides of carrots have been studied by Stevens and Selvendran (1984) and Massiot et al.(1988). Plat et al.(1991), Ben Shalom et al.(1992) and Massiot et al.(1992) investigated the changes in pectic substances of carrots after blanching, dehydration and extended heat treatment. Data on the changes in ceU waU polysaccharides of canned carrots are lacking. This study aims to investigate the effect of preheating time at low temperature and the addition of CaCL on texture and on the composition of various pectin fractions of carrots canned by conventional and by a new process. 

The analysis of how differently soluble pectin fractions of strawberry slices are modified by air dehydration, combined osmotic-air dehydration,... 

Fomi, E., Longoni, F., Maestrelli, A., Bertolo, G., and Torreggiani, D. 1998. Effect of osmotic dehydration on texture and pectin composition of 3 cultivars of strawberries. In Proceedings 4th Plenary Meeting EU-FAIR Concerted Action CT96-1118, Improvement of Overall Food Quality by Application of Osmotic Treatments in Conventional and New Processes , pp. 28-34. Thessaloniki, Greece. 

Lenart, A. and Dabrowska, R. 1998. Mass transfer during osmotic dehydration of apples with pectin coatings. In Drying 98 (C.B. Akritis, D. Marinos-Kouris, and G.D. Saravacos, eds), Vol. A, pp. 903-910. Ziti Editions, Thessaloniki, Greece. 

The mechanism of pyrolysis reactions of biomass was extensively discussed in an earlier study (Demirbas, 2000). Water is formed by dehydration. In the pyrolysis reactions, methanol arises from the breakdown of methyl esters and/or ethers from decomposition of pectin-like plant materials. Methanol also arises from methoxyl groups of uronic acid (Demirbas and Giillii, 1998). Acetic acid is formed in the thermal decomposition of all three main components of wood. When the yield of acetic... 

Moledina, K. H., Haydar, M., Ooraikul, B., Hadziyev, D. (1981). Pectin changes in the precooking step of dehydrated mashed potato production. J. Sci. FoodAgric.,32,1091-1102. 

The fact that 27 is produced by dehydration both of uronic acids and of pentoses has led to the suggestion112 that pentoses may be intermediates in decarboxylation reactions of uronic acids, and that treatment of such glycuronans as pectin with strong acids results in the production of pentosans.113 Little evidence supports this theory, be-... 

Concentrations and types of sugars or oligosaccharides also affect the viscosity of pectin solutions. Chen and Joslyn (1967) and Kar and Arslan (1999a) found that sucrose, dextrose and maltose increased the viscosity of aqueous pectin solutions whereas dextrins reduced it. The viscosity-enhancing effect of the sugars was interpreted in terms of the decrease in dielectric constant of the solvent, dehydration action and hydrogen bonding formation. However, the effect of dextrins on the viscosity of pectin was apparently an artifact due to ionic impurities in the dextrin. 

Pectins are also readily degraded by oxidation (Neukom, 1963), y-irradiation (Sjoberg, 1987), mechanical treatments such as grinding and extrusion (Bock et al., 1977 Ralet and Thibault, 1994), and dehydration (Ben-Shalom et al., 1992). 

Dehydration of pectin requires time to come to equilibrium (to account for slow setting or low temperature of setting of certain pectin gels). 

The rate of dehydration of pectin has not been studied, but recently Hinton (12) and Harvey (7) have developed a theory of the setting temperature of pectin gels based upon the solubility of pectin in the gelling medium. The evidence favors the postulation that as the solubility of pectin decreases, the temperature of set increases or the time of set decreases. 

Pectins are used as gelling agents either through the use of calcium cross-linking in the case of LM-pectins or sugar-induced dehydration with HM-pectin. Pectins are used as thickeners and stabilizers in jams, jelly, and fruit products [82]. Pectin can act as a protein dispersion stabilizer in acidified dairy products like yogurt and milk-based fruit drinks. 

Smith-Barbaro a. (26) in our laboratory determined the capacity of various fibers to bind the colon carcinogen 1.2-di-methylhydrazlne (DMH) in vitro. The percent of DMH bound to wheat bran, corn bran, alfalfa fiber and dehydrated citrus pulp was dependent on pH of the medium as well as the type of fiber examined. Results from this study show that at colonic pH, a greater percent of DMH was bound by wheat bran than by citrus pulp. Therefore, it is possible that certain fibers bind carcinogen at colonic pH, thus making it unavailable for contact with the colonic mucosa. Other fibers such as pectin (soluble fiber) do not bind DMH at colonic pH, but may modify the metabolism of carcinogen via actlvation/deactlvatlon steps either in the liver and/or in the colonic mucosa. 

The effect of dietary wheat bran and dehydrated citrus fiber at 15% level and 5% dietary fat on intestinal carcinogenesis induced by AOM and DMAS was studied in male F344 rats (44,45). Composition of diets was adjusted so that all animals in different experimental groups consumed approximately the same amount of protein, fat, minerals and vitamins. The animals fed the wheat bran or citrus fiber and treated with AOM had a lower Incidence (number of animals with tumors) and multiplicity (number of tumors/tumor bearing rat) of colon tumors and tumors of the small Intestine than did those fed the control diet and treated with AOM (Table II 15). Although 15% purified pectin in the diet (41) inhibited the colon tumor incidence better than did 15% dehydrated citrus fiber, in this study the Inhibition of colon tumor multiplicity was more pronounced with the dehydrated citrus fiber compared with purified pectin. Because dehydrated citrus fiber contains about 20% pectin, the pectin content of this diet was considerably lower than that of the diet used in... 

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