Effect of processing and cream quality on protein profile and rheological properties of set and stirred sour cream

Abstract

This study aimed to investigate the effect of the growth of psychrotrophic bacteria in cream and different processing parameters on sour cream quality. Fresh cream was incubated with a proteolytic strain of Pseudomonas trivialis and incubated for 0 and 6 days at refrigerated temperature before production of sour cream. Two types of sour cream (set and stirred) with 35 % fat were produced. The set-type sour cream was produced using two-stage homogenisation (50 bar/30 bar) and two incubation temperatures (21 and 25 °C), while the stirred-type sour cream was produced using one- or two-stage homogenisation (50 bar and 50/30 bar, respectively) and only one incubation temperature (23 °C). Protein profiles, free amino acids, viscosity, and gel structure were analysed. An increase in incubation time of approximately 3 h for both types of sour cream, as well as an effect on the free amino acid and protein profiles, was detected for the products made from low-quality cream. Low-quality cream significantly affected the viscosity in the set-type but not in the stirred-type sour cream, while the two-stage homogenisation impacted the viscosity in the stirred-type sour cream. The gel structure was significantly impacted when low-quality cream was used, and changes in aggregates were observed when a higher incubation temperature and two-stage homogenisation were used. The results presented here indicate that high-quality raw material is essential for the quality of the final product. However, we also showed that adjusting the processing could overcome the quality issue originating from low-quality raw milk.