Starch swelling behavior and texture development in stirred yogurt

Abstract

The present work aims to study the application of thickening starches in the production of stirred yogurt and the resulting physical and organoleptic properties. Five yogurt samples were formulated with nominal starch phase volumes (cq) ranging from 1.05 to 2.35. Phase volume was calculated based on the effective starch concentration (c) in the continuous phase and effective swelling volume after processing (q). The increase in starch concentration resulted in an increase of viscosity and elastic modulus (G′) due to the uptake of water by swollen starch granules, resulting in the thickening of the continuous phase, and the formation of more particle-particle interactions. Increasing the starch swelling volume (from 30 to 50 ml/g) under conditions in which the void volume between starch granules has been removed (cq above 1.8) did not drastically increase the viscosity. On the contrary, the G’ decreased, possibly due to the phase separation of starch particles and casein particulates, which resulted in the transition from a gel-like structure to a paste-like texture. Sensory descriptive profiling revealed that increasing the starch concentration will increase sensory firmness and cuttability. Yogurts with high cq values (1.88 and 2.35) exhibit a cohesive texture, characterized by a long and stringy mouthfeel. This is due to the long relaxation time of the concentrated starch particles. In summary, the starch cq value provides informative insights into the textural properties of the yogurt. Yogurts formulated with low effective starch swelling volumes (30 ml/g) and phase volumes slightly above the close packing point (1.41) have desirable organoleptic properties.