XYLOGLUCAN ENDOTRANSGLYCOSYLASE ACTIVITY IN APPLES IS RIPENING-RELATED - IMPLICATIONS FOR FRUIT JUICE PROCESSING

In order to assess the role of endogenous enzymes during apple juice m anufacturing by enzymic liquefaction, apples of different maturity wer e assayed for various enzyme activities. Xyloglucan endotransglycosyla se (XET) activity increased dramatically from early September to mid O ctober, and decreased slowly during cold storage. It was shown that XE T is probably the most important, endo-acting activity in apple. The a pples of different maturity were also treated by pectin lyase and vari ous concentrations of cellulase. It appeared that less cellulase was n eeded for disintegration of apples with a high level of XET activity. This suggests that XET facilitates the liquefaction process. Under cer tain conditions,'high XET' apples could be transformed into a cloudy a pple juice. This cloud may be regarded as a dispersion of particles wh ich is predominantly composed of cellulose and xyloglucan. (C) 1998 So ciety of Chemical Industry.