A comparative study of milk gels formed with κ-carrageenan or low-methoxy pectin

Abstract

It explains gelation and thickening of dairy products one of the most important food applications of the carrageenans, particularly /κ-carrageenan. Low-methoxy (LM) pectins also form gels with milk and these too have food applications—mainly in dairy desserts. Rheometry and differential scanning calorimetry (DSC) are used to study the mixed gels formed with skimmed milk powder (SMP) and /κ-carrageenan and LM pectin. The results indicate very different gelation mechanisms for the two polysaccharides. /κ-carrageenan forms a complex with casein micelles and it appears to act as a molecular 'Velcro' - interaction between free ends of bound /κ-carrageenan molecules linking casein micelles to form a gel network. At high ratios of /κ-carrageenan to SMP, a purely /κ-carrageenan network also appears to form, presumably consisting of more extended cross-linked /κ-carrageenan structures within which the casein micelles are enmeshed. In contrast, there is no direct interaction between casein micelles and LM pectin. The casein appears simply to act as a source of calcium-ions which promote gelation of the pectin.