ISHS Acta Horticulturae 297: II International Symposium on Kiwifruit
KIWIFRUIT JUICE PROTEINS: CHARACTERIZATION AND REMOVAL DURING PROCESSING OF CLARIFIED JUICE |
| Authors: | H. Dawes, P. Struebi, S. Boyes, D. Heatherbell |
| Keywords: | actinidin, haze formation |
| Abstract:
Kiwifruit juice (KFJ) contains a high concentration of soluble protein (0.2% w/w) which must be removed to obtain a haze-free, stable, clarified juice product. The soluble protein composition of KFJ and changes affected by processing have been studied. Using electrophoretic techniques (SDS-PAGE and PAGE-IEF), protein fractions of 14 000 to 32 000 molecular weight (MW) and isoelectric point (pI) ranging from 3 to 10 were identified in pressed KFJ. The proteolytic enzyme actinidin, which constitutes a major proportion of the soluble protein present, is thermally unstable and is readily coagulated under high temperature short time conditions. Approximately a third of the soluble protein present is heat-stable, comprising primarily fractions of 20 000 to 25 000 MW with a wide range of pls. Excessive amounts of bentonite of up to 4 500 mg/L were required to remove the last traces of these heat-stable protein fractions. | |
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