Impact of polymerized whey protein/pectin thickening (PP) system on physical properties and volatile compounds of goat milk kefir mild and kefir.

Polymerized whey protein and low-methoxyl pectin were used as thickening agents in fermented dairy food formulations. Effects of polymerized whey protein and pectin (PP) system on particle size distributions, rheological properties, molecular weight distributions of polysaccharides, microstructures, and volatile compounds of goat milk kefir mild and kefir were investigated. Clustering analysis indicated that the PP system addition could increase the particle size distributions and rheological properties of both kefir products. Molecular weight distributions of polysaccharides shown that an intermolecular aggregation occurred between pectin and exopolysaccharides (produced by microorganisms from starter cultures). Micrographs suggested that polymerized whey protein interacted with casein network to form a dense structure. Meanwhile, PP system did not change the characteristics flavor of goat milk kefir mild and kefir. Results indicated that the PP system may be a good combination to improve the physical properties of kefir products. PRACTICAL APPLICATION: Goat milk kefir has gained more and more attention due to its specific flavor and functional properties. However, poor texture of milk curd limits the consumption of fermented goat milk. As a new combination of thickening agents, PP system could specifically improve the particle size distributions and rheological properties of fermented goat milk. And the characteristic flavor of goat milk kefir was not changed. Results indicated that PP system can be used as thickening agents for formulations of different fermented goat milk products.