Stabilisation of acidified skimmed milk with HM pectin

• Published in: Food hydrocolloids 2010-06, Vol.24 (4), p.291-299
• Main Authors: Jensen, Søren, Rolin, Claus, Ipsen, Richard
• Format: Article
• Language: English
• Subjects: Acidification; acidified milk; Acidified milk drinks; Adsorption; Aggregates; Biological and medical sciences; Casein; Dilution; Food additives; Food industries; food processing; food processing quality; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; gelation; gels; General aspects; high methyl ester pectin; HM pectin; Milk; Networks; particle size; Pectin; pectins; protein aggregates; rheological properties; sedimentation; skim milk; Stability; stabilizers; temperature; viscoelasticity; viscosity
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2009.10.004

HM pectin was used to stabilise acidified milk drinks (AMD) against flocculation of milk protein. Two temperatures (16 and 27 °C) were used for acidification in order to obtain AMD of different average particle size. Stable samples were diluted with either serum simulating buffer (SSB) or water, and for these samples the adsorption of the pectin onto the casein aggregates was measured using HPLC. The particle diameter, viscosity and sedimentation, as well as the viscoelastic properties, were used to evaluate the amount of pectin needed to stabilise AMD. Additionally, confocal laser scanning microscopy was used with fluorescence recovery after photobleaching (FRAP) to assess protein mobility in samples. Upon diluting with water an increased adsorption of pectin onto the casein aggregates was observed and the stability decreased. In both water and SSB, a certain amount of pectin was firmly-possibly irreversibly-bound to the casein aggregates, and it could be inferred that the adsorbed pectin formed a multilayer on the casein aggregates. Even though the presence of a weak gel network was expected, no gel could be demonstrated in stable AMD by FRAP or the applied rheological measurements. We thus considerer it unlikely that formation of a network is solely responsible for the stability in AMD and propose a stabilising mechanism resembling steric stabilisation combined with secondary adsorption. [Display omitted]