Swelling kinetics of rice and potato starch suspensions

Granule size distribution of 8% w/w suspension of normal rice starch (NRS), waxy rice starch (WRS), modified potato starch (MPS), and normal potato starch (NPS) in water when subjected to heating at 60, 65, 70, 75, 80, and 85°C at different hold times (0–60 min) were characterized. The average starch granule diameter was larger at higher temperatures and hold times for NRS, WRS, and MPS indicating swelling, whereas for NPS it decreased indicating breakage. Swelling varied in the order: MPS > NRS > WRS. Earlier proposed pseudo first‐ and second‐order kinetic and Weibull models for swelling were evaluated. Swelling kinetics was also predicted using our previously developed mechanistic model (Desam et. al., 2018a Journal of Food Engineering 222:237–249) whose predictions agreed well with the experimental data of mean granule diameter and granule size distribution with time at different temperatures, and therefore can be employed to describe swelling at different processing conditions. PRACTICAL APPLICATIONS: Starches are incorporated in food products for a variety of reasons such as stabilizing, thickening, binding, and gelling. Starch occurs as discrete granules. Upon exposure to water, starch granules swell when heated. This results in thickening of starch suspension (known as pasting) due to an increase in volume fraction of swollen granules. Starch pasting results in an increase in its viscosity. Therefore, the texture of a variety of food products such as sauces, puddings, soups, batter mixes, and so forth are influenced by pasting. The rheology and texture of starch paste obtained by cooking of starch granules are governed by its swelling. It is, therefore, necessary to quantify swelling in order to predict the rheology of starch paste as well as to develop new food formulations. We developed a mechanistic model which predicts the swelling kinetics of rice and potato starch suspensions.