Enzymes in fruit

Pectin-Degrading Enzymes in Fruit and Vegetable Processing... 

Table I. Commercial pectolytic enzymes in fruit and vegetable technology...

Ferreira, D.C.M., Mello, L.D, Mendes, R.K., Kubota, L.T. Biosensors for fruit and vegetable processing. In Enzymes in Fruit and Vegetable Processing Chemistry and Engineering Applications. CRC Press, Boca Raton (2010)... 

Pectin is a long chain of pectic acid and pectinic acid molecules. Because these acids are sugars, pectin is categorized as a polysaccharide. It is prepared from citrus peels and the remains of apples after they are squeezed for juice. In the plant, pectin is the material that joins the plant cells together. When fungus enzymes break down the pectin in fruit, the fruit gets soft and mushy. 

Whitaker JR (1984) Pectic substances, pectic enzymes and haze formation in fruit juices. Enzyme Microb Technol 6 341-349... 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

Several alkenes occur naturally in living organisms. Some of these alkenes act as hormones and control biological functions. Plants produce ethene as a hormone to stimulate flower and seed production and to ripen fruits. Ethene stimulates enzymes in the plants to convert starch and acids of unripe fruit into sugars. The enzymes also soften fruit by breaking down pectin in cell walls. 

In order to preserve, as much as possible, the phenolic content in fruit and vegetable samples, the literature proposed the application of cold temperatures, even reaching to freezing, when lyophilization is the objective. These procedures also could inactivate the enzymes. The freeze-drying is largely the main preservation technique used in the studies related to the identification and quantification of the phenolic compounds of fruit... 

Tomas-Barberan FA and Espin JC. 2001. Phenolic compounds and related enzymes as determinants of quality in fruits and vegetables. J Sci Food Agric 81(9) 853-876. 

Baysal T and Demirdoven A. 2007. Lipoxygenase in fruits and vegetables a review. Enzyme Microb Technol 40 491-496. 

Ripe tomato fruits accumulate significant amounts of lycopene, but only trace amounts of xanthophylls. Dharmapuri and others (2002) overexpressed the lycopene (3-cyclase (b-Lcy) and (3-carotene hydroxylase (b-Chy) genes under the control of the fruit-specific Pds promoter, and transgene and protein expression was followed through semiquantitative reverse- transcription PCR, Western blotting, and enzyme assays. Fruits of the transformants showed a significant increase of (3-carotene, (3-cryptoxanthin, and zeaxanthin the carotenoid composition of leaves remained unaltered, and the transgenes and the phenotype were inherited in a dominant Mendelian fashion. 

Appreciable amounts of polyphenols (PPs) associated with both IDF and SDF have been reported in fruit, vegetables, and beverages (Tables 8.3 and 8.4). These compounds may be considered DF constituents in view of the similarity of their properties in terms of resistance to digestive enzymes and colonic fermentability. 

The types of spoilage caused by bacteria in fruits and vegetables are diverse they include sensory changes, degradation of compounds, and formation of new substances such as acids, volatile compounds, and polymers. For example, the bacteria produce a set of enzymes such as pectinases, cellulases, proteases, and others that causes maceration and softening of tissue. Off-flavor development is common in contaminated tissues, caused by volatile compounds produced by microflora (Jay 1992). 

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