Heat stability and flow behaviour of buffalo milk added with corn starch

• Published in: Food hydrocolloids Vol. 18; no. 3; pp. 379 - 386
• Main Authors: Nayak, S.K., Makrariya, A., Singh, R.R.B., Patel, A.A., Sindhu, J.S., Patil, G.R., Tomar, Priyanka
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2004; Elsevier
• Subjects: Biological and medical sciences; Buffalo milk; colloidal casein micelles; colloidal properties; Corn starch; Food additives; Food industries; Fundamental and applied biological sciences. Psychology; Gelatinization; General aspects; Heat stability; milk clotting; milk-starch mixture; Shear thinning; skim milk; Starch and starchy product industries; Viscosity; Viscosity; Heat stability; Gelatinization; Corn starch; Buffalo milk; Shear thinning; Shear; Stability; Starch; Corn; Quality; Cereal; Carbohydrate; Polysaccharide
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/S0268-005X(03)00125-5

In this study, heat stability and flow behaviour of buffalo skim milk and its concentrate added with corn starch and then gelatinized at 85 °C were evaluated with regard to level of corn starch (1 and 2%) and gelatinization time (10–80 min). Heat stability measured in terms of the heat coagulation time (HCT) at 130 °C of the starch–milk mixtures declined with increasing gelatinization time, the decline being slight in case of 1% starch but significant ( P<0.01) with 2% starch. The apparent viscosity ( η a, shear rate 500 s −1) of the heat-treated, i.e. gelatinized un-concentrated milk–starch mixtures was distinctly higher than that of heat-treated milk alone, but increasing gelatinization time from 10 to 80 min resulted in a relatively small rise in viscosity. However, in case of skim milk concentrate added with both 1 and 2% starch, the increase in viscosity induced by gelatinization beyond 10 min was significant ( P<0.01). The skim milk–starch systems showed a power law behaviour. An increase followed by a decrease in the consistency coefficient ( K) with increasing gelatinization time was noticed in the un-concentrated system, whereas the concentrate–starch mixtures exhibited steadily increasing K with increasing gelatinization time at 85 °C. The flow behaviour index ( n) of the mixtures was in the shear thinning range, but this characteristic was more prominent in un-concentrated system, the value of n decreasing with increasing gelatinization time. The heat treatment of milk–starch mixtures resulting into gelatinization-induced increase in viscosity was conceived to be due to water uptake by starch granules accompanied by increased concentration of the non-starch phase leading to rapid aggregation (coagulation of colloidal casein micelles during subsequent heating at 130 °C) and thus causing the HCT to decline. The HCT was directly correlated with pH, and negatively with apparent viscosity and consistency coefficient, the former correlation being highly significant ( P<0.01) in the milk-based system, while the latter correlations were so in the concentrate-based-one.