Transfers of small analytes in a multiphasic stirred fruit yoghurt model

• Published in: Food hydrocolloids Vol. 21; no. 2; pp. 287 - 296
• Main Authors: Nongonierma, Alice B., Cayot, Philippe, Springett, Mark, Le Quéré, Jean-Luc, Cachon, Rémy, Voilley, Andrée
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2007; Elsevier
• Subjects: Biological and medical sciences; Colorants; Coupled transfers; Dairy gel; Diffusion; electrostatic interactions; flavorings; Food additives; food coloring; Food engineering; Food industries; Fruit and vegetable industries; fruit yogurt; fruits (food); Fundamental and applied biological sciences. Psychology; gels; General aspects; gluconolactone; hydrolysis; hydrophobicity; ion transport; Life Sciences; milk fat; milk proteins; model food systems; Pectin gel; pectins; Protons; Water; water activity; water content; yogurt; Protons; Water; COO; C; dg; Colorants; Ag; Cl; dM; C j; Dairy gel; Coupled transfers; D j; t; C j i; pg; erf; x; Diffusion; Pectin gel; Fruit; Dairy product; Pectin; Yogurt; Food additive; Gelling agent; Dietary fiber; Polysaccharide; COUPLED TRANSFERS; DAIRY GEL; PECTIN GEL; DIFFUSION; PROTONS; WATER; COLORANTS
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2006.04.007

The transfer of small analytes in a multiphasic stirred fruit yoghurt model, made of a pectin gel aimed to mimic fruit pieces and of a dairy gel done with milk acidified by glucono- δ-lactone hydrolysis, have been studied. The concentration gradients between the pectin gel and the dairy gel were the driving force for the migration of small analytes (i.e. water, protons and colorants). Water migrated from the dairy to the pectin gel, causing modifications in the water content of both gels and an equilibration of their water activity at 0.938±0.003. Inversely, protons migrated from the pectin to the dairy gel. These changes in composition of both gels being likely to have induced structure modifications. Migration of relatively small molar mass colorants did not depend on steric considerations, but rather on their charge and structure. In both gels, most of the colorants studied were charged at the equilibrium pH 4.1. This charge was linked to their diffusivity in the pectin gel. Negatively charged colorants were thought to be affected by the attractive electrostatic forces between the pectin carboxylic groups and Ca 2+, causing a decrease in their diffusivity. Transfer of colorants in the dairy gel were affected by electrostatic interactions with milk proteins and ions or by hydrophobic interactions with milk proteins and fat.