Vol. 8, Issue 11 (2019)

Author(s):
Raj Narayan Saraswat, Trishul Prakash Singh, Vikash Kumar and Heartwin A Pusphadaas

Abstract:
The rheological characteristics of Lassi were studied by using a computer-controlled rotational viscometer over a range of total solids (TS) sugar contents and stabilizers such as carrageenan, pectin and locust bean gum (LBG). The viscometric data were converted into the basic shear stress vs. shear rate form using Mitschka method. From the shear rate-shear stress data, the flow nature of Lassi was evaluated. The apparent viscosities of the systems decreased with increasing shear rate, indicating pseudoplastic behaviour with yield stress. The rheological behaviour of Lassi was adequately described by the Herschel-Bulkley and Casson models with a high coefficient of determination (R 2) and low root mean square error (RMSE). The Ostwald De Waele model did not fit very well because of the yield stress in Lassi. The Herschel-Bulkley yield stress (σ 0), consistency coefficient (K) and the flow behavior index (n) were determined. The values of σ 0, ‘K’ and ‘n’ ranged from 0.638-7.725 Pa, 0.330-0.834 Pa.s n and 0.514-0.701, respectively. The main and interaction effects of these selected factors on the apparent viscosity, yield stress, consistency coefficient and flow behaviour index were found to be highly significant.