Relating the microstructure of pectin and carrageenan in dairy desserts to rheological and sensory characteristics

Pectin and carrageenan are widely used as gelling agents in dairy products but little is known about their specific microstructure when used in combination. The purpose of this study was to investigate how the addition of low ester amidated pectins with varying calcium (Ca) reactivity affects the microstructure, rheology and sensory characteristics of model dairy desserts containing carrageenan and starch. Direct immunostaining was employed so the microstructure of pectin and carrageenan could be identified using a confocal laser scanning microscope. Image feature extraction distinguished between the dessert microstructures. The addition of pectin had a major impact on the microstructure, rheology and sensory characteristics of the dairy desserts. Increased Ca reactivity of pectin resulted in a microstructure with increased colocalization of pectin and protein and reduced phase separation. This was accompanied by increased gel strength and adhesiveness and, according to the sensory panel, reduced aqueousness and increased chewing time. The results can be explained by a combination of factors related to the gel strength of the pectin, convergence of pectin and carrageenan gelation temperatures, and hydrogen bonding between amide groups on pectin and protein.