Food Colorants: Chemical and Functional Properties

Carmen Socaciu

Oct 2007 · CRC Press

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Drawing on the expertise of internationally known, interdisciplinary scientists and researchers, Food Colorants: Chemical and Functional Properties provides an integrative image of the scientific characteristics, functionality, and applications of color molecules as pigments in food science and technology, as well as their impact on health. The boo

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the term betalains (latin beta-beet) was coined in 1968 by Mabry and Dreiding for the yellow abd red N-heterocyclic pigments from cactus peat abd red beet, which until then had been erroneously called flavocyanains. in 1963 and 1964, betanin and indicaxanthin were the first betacyanin and betaxanthin structurally elucidated from red beet and cactus pear fruits (opuntia ficus indica (L).Mill). one year later, the term betalamic acid was proposed for theri mutual biosynthetic precursor. betalains and anthocyanins differ each other and evolutionary theory also indicate that betalains apperared after the anthocyanins. both the pigments share shikimate pathway, but the differentiation commences at the arogenate level, leading either tyrosine( betalaines) or phenylalanine anthocyanins) PHYSICAL AND CHEMICAL PROPERTIES: betalains are vaculora plant pigments. hence their hydrophilic nature is comprehensible. they are slighly soluble in ethanol and methanol, water is the best suitable solvent for stability and solubility reasons. the extinction coeffecient of betaxanthins and betacyanins 48,000L/mol*cm and 60,000L/mol*cm values respectively. the colour changes upon acidification or alkalization are most characteristic. while the betalains visibly change to a canary yellow tint at alkaline pH through release of betalamic acid.betalains are sensitive to the presence of metals, sulfurdioxide, light exposure, high water activity, enzymatic action, pH and elevated temperatures. the betaxanthins are most stable at pH2.5to 7, betacyanins at 5 to 6 and betalamic acid at pH9. usually, whole unpeeled beets are processed; more than 30% colour is lost by removal of the peels. this is noteworthy because the greatest polyphenoloxidase activity, which is deleterious of both betacyanins and betaxanthins, IS LOCATED IN THE Peel. previous balnching presents a tool to inactivate unfavourable enzymatic action. in theory, the oxidizing and hydroxylating activities of polyphenol oxidase action require monophenolic or diphenolic structures rarely found in betaxanthins and betacyanins and only after previous hydrolysis of beta glucosidase activity. hence for enzymatic betalain degradation, a concerted action of glucoside-cleaving enzymes, polypheoloxidases and peroxidases is required. in general, small beets are favored because they accumulate higher betalain concentrations. tissue comminuation is usually performed by milling, followed by acidfication ofthe resulting mash through the addition of citric acid until reaching pH4.0. lowering the pH will preclude the polyphenol oxidase activity while the peroxidases may still be active until the filtered juice is heated to a exceeding temperature 75C.through acidification, a low thermal load i.e pasteurazation instead of sterilization, suffices to secure microbial stability. thus pigments will less severly affected.notably little research has been dedicated to exploiting alternative food sources. this is even more surprising since red beet preparations are afflicted witj adverse flavors of geomisin and methoxy-pyrazine derivatives, high nitrate levels, and the risk of carry over of earth bound germs. P87-90

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Carmen Socaciu