Fruit enzymic activities

Figure 1. Pectinesterase activity in normal tomato fruit. Enzyme activity is exjM-essed as (ueq min gfwt)...

FRASER P D, KIANO I W, TRUESDALE M R, SCHUCH W and BRAMLEY P M (1999) PhytOene synthase-2 enzymes activity in tomato does not contribute to carotenoid synthesis in ripening fruit . Plant Mol Biol, 40, 687-98. 

KUNTZ M, ROMER s, suiRE c, HUGUENEY p, WEIL j H, scHANTZ R and CAMARA B (1992) Identification of a cDNA for the plastid-located geranylgeranyl pyrophosphate synthase from Capsicum annuum correlative increase in enzyme activity and transcript level during fruit ripening , Plant J, 2, 25-34. 

SALA J M and LAFUENTE M T (2000) Catalase enzyme activity is related to tolerance of mandarin fruits to chilling , Postharvest Biol Technol, 20 (1) 81-9. 

The improvement of our knowledge on fruits cell wall has allowed us to describe new enzyme activities to specifically degrade these substrates to optimize the performance of industrial equipments and to allow to produce juices and concentrates with a higher quality in terms of oxidization, aromas level and stability. 

Each fruit has specific quantities and ratio of pectin, hemicelluloses and cellulose. These polysaccharides are important concerning enzymes activities required to produce juices and concentrates. Moreover, even if molecular weight and methylation degree of the pectin are specific for each fruit, during the fruit maturation, endogenous pectinases depolymerases and esterase are changing the pectin characteristics This broad variability of raw material makes difficult the standardisation of fruits processing. 

In this presentation, we will take examples of different fruit juice processes and will try to relate enzyme activities, the role they play and the transformation they occur in terms of finished products. These examples will concern apple juice, french cider, pineapple and wine. 

Thanks to specialists to help us to better understand fruits composition and to associate biochemical structures to acurate enzyme activities able to answer to technical needs. 

With the description of new enzyme activities, we will be able to create very soon new fruits derivates and new types of beverages. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Capsaicinoids are synthesized by the condensation of vanillylamine with a short chain branched fatty acyl CoA. A schematic of this pathway is presented in Fig. 8.4. Evidence to support this pathway includes radiotracer studies, determination of enzyme activities, and the abundance of intermediates as a function of fruit development [51, 52, 57-63], Differential expression approaches have been used to isolate cDNA forms of biosynthetic genes [64-66], As this approach worked to corroborate several steps on the pathway, Mazourek et al. [67] used Arabidopsis sequences to design primers to clone the missing steps from a cDNA library. They have expanded the schema to include the biosynthesis of the key precursors phenylalanine and leucine, valine and isoleucine. Prior to this study it was not clear how the vanillin was produced, and thus the identification of candidate transcripts on the lignin pathway for the conversion of coumarate to feruloyl-CoA and the subsequent conversion to vanillin provide key tools to further test this proposed pathway. 

In many countries additives are forbidden in bread, except aromas in, for instance, fruit-flavored bread. Natural additives like enzyme active soya flour get only little attention for application in bread improvers because ... 

Amylases. In the case of pome fruits other enzyme activities are sometimes required. When fruit has been picked before maturity and then ripened under controlled atmospheric conditions in a cool store, there is a likelihood of starch retention originating from the unripe fruit. This starch can become gelatinised during juice processing and can give rise to precipitation and haze effects in the final product. Amylases are used here to break down any residual starch and overcome such problems. 

Phenolic acid Inhibits nitrosamines enhances enzyme activity Berries, broccoli, cabbage, carrots, citrus fruits, eggplant, parsley, peppers, teas, tomatoes, whole grains... 

Wild-Altamirano, C. (1 969) Enzymic activity during growth of vanilla fruit. 1. Proteinase, glucosidase, peroxidase and polyphenoloxidase. Journal of Food Science 34, 235-238. 

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