S., Berghall; S., Briggs; S.E., Elsegood; L., Eronen; J.O., Kuusisto; E.J., Philip; T.C., Theobald; P., Walliander
In a collaborative project between British Sugar plc and Sucros Ltd, four sucrose inverting enzyme activities were identified in sugar beet: soluble acid invertase, insoluble acid invertase, soluble alkaline invertase and soluble sucrose synthetase. The activities of these enzymes were measured in the growing crop, during beet storage and through the extraction process. Crop sample results confirmed many of the previous understandings on the phasing of plant growth and sucrose accumulation. It is likely that the enzymes active in sugar beet before harvest are necessary in their entirety for healthy plant development. During clamping and storage, a relationship between beet invertase and sucrose synthetase activities, and invert sugar content was observed. Two distinct physiological pathways influencing these activities are proposed. Clamping and storage trials were performed both in U.K. and Finland under very different climatological conditions. Typical late autumn and early winter freezing and thawing in Finland caused significant invertase activity increase in beet starting to deteriorate. Microbial invertases analysed showed significantly higher thermostability compared to beet invertases. Results from healthy beet process sampling indicated that only a small fraction of the difference between sugar beet and raw juice invert sugar concentration was due to sugar beet derived invertase enzymes. While processing frozen and thawed beet material, the invert sugar difference was higher, but still only partially explained by elevated invertase enzyme activities in the beet material. The results emphasized the importance of rapid temperature increase in extraction. It is possible to estimate the considerable financial impact of invert sugar formation during clamping and processing. This report provides information useful in the reduction of this cost.
pdf download: 1997-520-530.pdf