Mixtures of alginate and high methoxy pectins formed thermoreversible gels below pH 3.8 without any addition of sugar, provided that D-glucono-deltalactone (GDL) was used as a slow acidifier in the cold. The gelling occurred at conditions where neither alginate nor the high methoxy pectin gelled alone. The strength and melting points of these synergistic gels increase with decreasing pH and increasing content of L-guluronic acid residues in the alginates. The gelling effect was correlated to the sequential distribution of the two monomers, D-mannuronic (M) and L-guluronic acid (G) residues, in the alginate chain. The results indicated that "blocks" of at least four contiguous G-units were necessary for gelling to occur. The results were discussed in view of existing molecular theories for synergistic gelation.In a search for thermoreversible gelling systems that could be used in low-sugar, low-calorie jams and jellies, Toft discovered that mixtures of high methoxy pectins and alginates with a high content of ^-guluronic acid residues formed gels under conditions where neither alginate nor pectins gelled alone (JJ .These warm-setting gels were formed below pH 3.8, and could be made with a sugar content as low as 20%. Later Toft reported (2^) that thermoreversible gels could be formed without any requirement for sugar, by using D-glucono-deltalactone (GDL) in the cold as a slow acidifier.Since the number of gel forming polysaccharides allowed for use in the food and pharmaceutical industries is limited, the discovery of new synergistic gelling systems may have potential commercial value, as have the well-known

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