Cellulases, liquefaction

Enzymatic liquefaction is a relatively new process for the production of juices from fruits and vegetables [1]. Essentially the process is as follows the material is crushed to obtun a pulp which is treated with a combination of pectinases and cellulases. After a certain incubation time, the material becomes a liquid and the Juice can be recovered by decantation. 

In combination with hemicellulases and cellulases, pectinases can lead to fmits liquefaction. 

Cellulases. These enzymes may be used to facilitate the rapid removal of colour during fruit processing. Such enzymes have also been employed to good effect in recent years in the total liquefaction of plant tissues during processing, obviating the need to use a press, yet increasing yields. 

Enzymatic liquefaction of the pulp makes pressings redundant. Besides pectinase, the liquefaction process also requires cellulase (endo-cellulase, cellobiohydolase, P-glu-cosidase). Industrial liquefaction processes became possible when Trichoderma spp. cellulase became available. The combination of pectinase and cellulase leads to a very low viscosity liquid. This liquid is treated further by centrifugation and (ultra)filtra-tion to obtain the final clear fmit juice. 

Pectinases, cellulases and hemicellulases are used for clarification of fruit juices, juice extraction, improvement of cloud stability of vegetable and fruit juices and nectars, liquefaction and maceration of fruits and vegetables, reduction of cooking time of pulses and improvement of rehydration characteristics of dried vegetables. The chemical basis of these treatments and of the consequential changes in sensory and nutritional quality are discussed. 

The commercial liquefaction enzyme typically used (Rhoapect 7016) contained predominantly cellulase and hemicellulase activity but with some pectinase activity. The use of more pectinase and less liquefaction enzyme represented a more favorable treatment economically and was actually more effective in reducing viscosity (Table II). Also, as predicted, the steady state flux of the membranes was higher when pectinase predominated. 

The main causes of viscosity loss of cellulose ethers are of microbial (b u teria, fungi and enzyme) and chemical (redox process) natures. Biocides are used to kill bacteria and fVingi but they are usually not effective against enzymes. The enzymatic liquefaction is known to be the strongest process. Studies have been made on different cellulosic thickeners with bacteria, fungi and commercial cellulase enzyme juid the overall conclusion was that cellulase is the most significant cause of viscosity loss. ... 

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