Fruit processing, pectic

The extent and mode of bioconversions of pectic substances in situ, their solubilization and depolymerization effect consistency, cloud behaviour, pressing characteristics, juice release, soluble solids, clarification, haze formation and browning potential. We have been studying plant cell wall degradation with pure and well characterized enzymes and from the results of these studies we are now able to better define the various stages in cell wall degradation and to understand implications for fruit processing. This will be demonstrated in apple juice production and stabilization of apricot nectar. 

A traditional system for the preparation of table olives, involves a treatment of the fresh fruit with a solution of NaOH to hydrolised the bitter glycoside oleuropein, followed by a lactic fermentation in brine. The modifications that take place on pectic polysaccharides of olives (Manzanilla variety) during this process was smdied. Processing induced a net loss of polysaccharides soluble in sodium carbonate and a paralel accumulation of water and Imidazole/HCl soluble polysaccharides. A general decrease of the apparent molecular weight of water and carbonate soluble polysaccharides was also detected. 

The quality of extracted citrus juices depends on enzyme reactions that occur not only in the fruit during the development period, but also in the juice during processing. When juice is extracted from citrus fruit, enzymes are released from their normal restraint in the cell. Several of these enzymes catalyze reactions that adversely affect taste and appearance of the juice. Unless the reactions are controlled, the juice products will not meet the standards of quality set up by the USDA Food Safety and Quality Service. The two reactions of commercial importance are the hydrolysis of pectin to pectic acid, which clarifies juice, and the lactonization of limonoic acid A-ring lactone to the bitter compound, limonin. Research efforts to identify and characterize the reactions, to isolate and purify the enzymes, and to develop methods to control the reactions are described in this review. 

Pectic substances are important structural components of the middle lamellea and the primary cell walls of higher plants, in particular fruits and vegetables. The extent and mode of their degradation by enzymes affect many aspects of the processing of fruits and vegetables and many quality attributes of fruit and vegetable products. 

The processing of fruits and vegetables cause changes in pectic substances. Changes in texture of fruits and vegetables during... 

Doesburg, J. J. Pectic Substances in Fresh and Preserved Fruits and Vegetables Institute for Research on Storage and Processing of Horticultural Produce Wageningen, The Netherlands, 1965 p. 44. 

Doesburg, J.J. Pectic substances in fresh and preserved fruits and vegetables IBVT-Communication No. 25. Institute for Research and on Storage and Processing of Horticultural Produce Vageningen, 1965. 

Protopectin is composed of water-insoluble pectic substances, which are fixed to the middle lamella and primary cell walls of plant cells. The neutral sugar side chain of the pectin is attached to the xyloglucan residues, which are bound to the cellulose fibers. The protopectin includes polyvalent such as calcium (Fig. 11.4-8). Protopectin is present in unripe fruits. During the maturation process of fruits or after harvesting, the protopectin is converted to soluble pectin11851. The insolubility of protopectin may be due to the polymerization of the molecule and to the cross-linking with divalent cations11861. 

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