Chlorophylls heating

On the other hand, isomerization of sil-trans P-carotene was found to be comparatively faster in a model containing methyl fatty acid and chlorophyll heated at 60°C (Table 4.2.6), resulting in 13-cw-P-carotene as the predominant isomer. The first-order degradation rate of P-carotene significantly decreased with the increased number of double bonds in the methyl fatty acid, probably due to competition for molecular oxygen between P-carotene and the fatty acid. Since the systems were maintained in the dark, although in the presence of air, the addition of chlorophyll should not catalyze the isomerization reaction. 

Prepared by heating ammonium mucate, or from butyne-l,4-diol and ammonia in the presence of an alumina catalyst. The pyrrole molecule is aromatic in character. It is not basic and the imino-hydrogen atom can be replaced by potassium. Many pyrrole derivatives occur naturally, e.g. proline, indican, haem and chlorophyll. 

Hydrolysis of chlorophyll using sodium hydroxide produces the moderately water-soluble sodium salts of chlorophyllin, phytol and methanol (145). The magnesium ia chlorophyllin may be replaced by copper. The sodium copper chlorophyllin salt is heat stable, and is ideal for coloring foods where heat is iavolved, such as ia canning (146). 

The typical isocyclic ring E present in chlorophylls is susceptible to a number of different modifications such as epimerization, which produces stereoisomers by inversion of the configuration at C-13 of their parent pigments. These 13 -epichlorophylls, known as chlorophylls a and b, are minor pigments. They are considered artifacts produced in the course of handling plant extracts and sometimes are also found in small amounts in heated and deep-frozen vegetables, hi the old Fischer systan of nomenclature that can still be found in some literature, these epimers were named 10-epichlorophylls. 

Allomerized chlorophylls are oxidized compounds at C-13, forming theC-13 OH-chlorophyU catabolites. Other common positions for modifications and/or oxidation have been found at C-3, C-7, and C-8. Pyroderivatives of chlorophylls and their degradation products, usually found in heated and processed vegetables, lack the carbomethoxy group (-COOCH3) at C-13 of ring E, which is replaced by hydrogen. 

Studies of chlorophyll degradation in heated broccoli juices over the 80 to 120°C range revealed that chlorophylls degrade first to their respective pheophytins and then to other degradation products in what can therefore be described as a two-step process. Both chlorophyll and pheophytin conversions followed a first-order kinetics, but chlorophyll a was more heat sensitive and degraded at a rate approximately twice that of chlorophyll This feature had been observed by other authors. Temperature dependence of the degradation rate could adequately be described by the Arrhenius equation. ... 

Although chlorophyll and chlorophyllin colorants seem to be easily obtained, in practice their production as natural food colorants is rather difficult. The sensitivity of chlorophylls to certain enzymes, heat, and low pH, and their low tinctorial strength greatly limit their manufacture and application as food additives, principally when the pigments are isolated from the protective environment of the chloroplasts. The well-known instability of chlorophylls prompted extensive research for developing... 

In recent years, metallo-chlorophylls and metaUo-chlorophyllins have been considered alternatives to their natural chlorophyll counterparts due to their enhanced color potency, and greater stability against moderate heat, dilute acids, and oxidative agents in general, not to mention their alleged biological activities. 

Funamoto, Y. et al.. Effects of heat treatment on chlorophyll degrading enzymes in stored broccoli (Brassica oleracea L.), Postharvest Biol.TechnoL, 24, 163, 2002. 

Weemaes, C.A. et al., Kinetics of chlorophyll degradation and color loss in heated broccoli juice, J. Agric. Food Chem., 47, 2404, 1999. 

LaBorde, L.R and Von Elbe, J.H, Chlorophyll degradation and zinc complex formation with chlorophyll derivatives in heated green vegetables, J. Agric. Food Chem., 42, 1100, 1994. 

Liu, M.H. and Chen, B.H., Relationship between chlorophyll a and (3-carotene in a lipid-containing model system during heating, Food Chem., 61, 41, 1998. 

Chen, B.H. and Huang, J.H., Degradation and isomerization of chlorophyll a and (3-carotene as affected by various heating and illumination treatments, Food Chem., 62, 299, 1998. 

Havaux, M. and W.I. Gruszecki. 1993. Heat- and light-induced chlorophyll a fluorescence changes in potato leaves containing high or low levels of the carotenoid zeaxanthin Indications of a regulatory effect of zeaxanthin on thylakoid membrane fluidity. Photochem. Photobiol. 58 607-614. 

Copper Chlorophyll (E141). This is made from chlorophyll it is more blue than natural chlorophyll. The chemical modification makes it much more stable to heat and light. It is a more useful material than natural chlorophyll. 

A widespread method for determining the induction period for autoxidation of oils and fats consists of passing a continuous stream of air through the heated sample and collecting the volatile acids evolved in a water trap, where they are determined on a real time basis. The time plot usually presents a flat appearance for a certain period and then takes off in an accelerated manner. This test is the basis of several national and international standards (e.g. AOCS Cd 12b-92—oil stability index" ISO 6886—accelerated oxidation test for oxidative stability of fats and oils ) and the design of the Rancimat equipment, where the end determination is based on conductivity measurements . In addition to oxidation stability as determined by the Rancimat method and POV, which negatively affects virgin olive oil stability, other nonstandard properties were proposed for better assessment of the quality of this oil, namely LC determination of Vitamin E (21), colorimetric determination of total polar phenols and UVD of total chlorophyll. ... 

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