Enzymes during maturation

Various physico-chemical changes occur in the structural components of the para-casein matrix during maturation these changes are mediated by the residual rennet, microorganisms and their enzymes, and changes in mineral equilibrium between the serum and para-casein matrix. The type and level of the physico-chemical changes depend on the cheese variety, cheese composition and ripening conditions. These may include ... 

Maturation effected the following changes In enzymes and metabolites in orange fruit ethanol and acetaldehyde accumulated to levels of 10 mM and 0.08 mM, pyruvate decreased about 30%, pyruvate decarboxylase increased over 4 fold, alcohol dehydrogenase increased about 2 fold, the NADH to NAD ratio increased 21/2 fold and the terminal oxidase developed CN-insensitivity. The fraction of the total alternative respiratory pathway in actual use increased from 0.46 to 1.08. Induction of the alternative, CN-insensitive oxidase during maturation was interpreted as indicating that membrane function was modified which affected metabolic pathways resulting in the accumulation of ethanol and acetaldehyde. 

However, activity of the competing enzyme for pyruvate, PDH, is controlled by ratios of NADH to NAD and ATP to ADP in plant mitochondria (18). During maturation of Hamlin orange the ratio of NADH to NAD in juice vesicles increased from 0.09 in October to 0.24 in March, while the phosphorylated ratio (NADPH/NADP) was constant (17). The PDH from broccoli was very sensitive to increases in the mole fraction of NADH (19). A 10 to 15% increase in ratio in whole tissue decreased PDH activity 15 to 25%. The ratio of ATP to ADP in juice vesicles increased initially from 0.7 in October but plateaued at 1.0 after December. ATP inactivated PDH by enzymic phosphorylation in mitochondr from pea leaf (20). The phosphorylated PDH was activated by a Mg -dependent phosphatase. Both reactions were inhibited by ADP which suggests... 

Probably the most revealing study into the sequential maturational events induced by thymic peptides in precursor cells employed human thymocytes obtained from children undergoing cardiac surgery (Ho et al., 1983). During maturation, human thymocytes exhibit a series of sequential changes in the expression of various intracellular purine degradative enzymes including... 

Identification of the compounds which form the volatile profile and flavor of raw peanuts will advance studies concerning the mechanics by which these compounds are produced. For example, the findings in that the volatile profile and activity levels of alcohol dehydrogenase and lipoxygenase change during maturation prompted the hypothesis that the volatiles, e.g., acetaldehyde, ethanol, pentane and hexanal, are related to these enzymes and their substrates (30). 

Enzymes can be used to help the starch hydrolysis (typically a-amylases), solve filtration problems caused by P-glucans present in malt (P-glucanases), hydrolyze proteins (neutral proteinase), and control haze during maturation, filtration, and storage (papain, a-amylase, and P-glucanase). 

Cherry JH, van Haystee R (1965) Comparison of messenger RNA in photoperiodically induced and non-induced Xanthium buds. Science (Wash DC) 150 1450-1453 Choinski JS Jr, Trelease RN, Doman DC (1981) Control of enzyme activities in cotton cotyledons during maturation and germination. III. In-vitro embryo development in the presence of abscisic acid. Planta (Berl) 152 428-435... 

Pattee HE, Singleton JA, Johns EB, Mullin BC (1970) Changes in the volatile profile of peanuts and their relationship to enzyme activity levels during maturation. J Agr Food Chem 18 353-356... 

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