Oxidative gelation of sugar-beet pectins: use of laccases and hydration properties of the cross-linked pectins

Beet pectins are known to have feruloyl groups on their neutral side-chains . It is possible to cross-link the beet pectin through the oxidative coupli ng of these feruloyl groups leading to a new gelation process. We have inve stigated a new way of cross-linking by the use of a single enzyme, namely a laccase. Pectins have been extracted from beet pulp by various methods, in cluding acid treatment and extrusion-cooking. Results showed that beet pect ins can gel on the addition of laccases. More or less gellable pectins can be obtained but the gelation may be favoured using another enzyme, an arabi nofuranosidase which make the feruloyl groups accessible to the coupling re action. Chemical gels can therefore be obtained and the cross-linked pectin s may be obtained as powders after drying. The degree of cross-linking, whi ch can be modulated by the amount of pectin, of enzyme added and the reacti on time, was found to be very critical for the hydration properties of the powders. Swelling capacities were typically in the range 25-50 ml/g of prod uct, leading possibly to new applications for the beet pectins. (C) 1999 El sevier Science Ltd. All rights reserved.