Effect of salt pretreatments on physico-chemical, cooking and rehydration kinetics of instant rice

Instant rice is well-suited for ready-to-use applications as low-moisture, light-weight military ration and emergency food for our Armed Forces, offering longer shelf life with rapid rehydration characteristics. Present investigation demonstrated the effect of different salt pretreatment during soaking as precooking operation on the physico-chemical, cooking and rehydration kinetics of instant rice. Application of salt pretreatment reduced bulk density and damaged grain percentage, while enhanced the porosity, volume expansion percent, weight gain percentage, and rehydration characteristics. The grain elongation ratio was not affected significantly by the application of salt pretreatments; however, water uptake and chemical composition were significantly affected. Soaking pretreatment with 1% calcium chloride, followed by open pan cooking and subsequently freeze-thaw-dehydrating until attainment of 5–6% moisture content was found to be the optimal processing condition for developing instant rice with less than 2 min of rehydration time by mere addition of hot water. Modelling of water absorption behaviour revealed that both Peleg (R2 0.980–0.999) and Singh and Kulshrestha (R2 0.966–0.999) models fitted well.