Variation in amylose content in three rice variants predominantly influences the properties of sushi rice

Abstract

AbstractSushi rice is a ready-to-eat traditional Japanese dish seasoned with vinegar, sugar and salt that has gained popularity worldwide. There are many rice cultivars grown in the world which vary in their cooking, sensory, and processing quality. The aim of this study was to analyse chemical, physical, and functional properties of three rice varieties (Vietnamese, Italian, and Australian) to determine their suitability for sushi rice production. Rice was cooked using industry norms and vinegar was then added; samples with no vinegar were prepared for comparison. The rice was stored during 5 days at 4 °C after cooking for texture profile analysis and samples were taken on day 1 and day 5. Flour composition as well as amylose content, gelatinisation properties using differential scanning calorimeter, pasting properties using Rapid Visco Analyser, water absorption capacity (WAC), oil absorption capacity (OAC) and swelling power of extracted starch were determined. Results showed that the amylose content (16.51 to 21.37%) had a large impact on the functional and quality characteristics of the rice variants including texture, pasting, gelatinisation and WAC properties. Australian starch showed the highest amylose content, setback viscosity, final viscosity, pasting temperature and lowest gelatinisation temperature. The lower amylose content and gelatinisation temperature contributed to a softer texture in the Vietnamese rice samples over life. The added vinegar aided in keeping the texture soft during the shelf-life of the rice. Since sushi rice is usually prepared with vinegar, Italian and Vietnamese rice are better candidates for sushi rice based on their lower hardness after 5 days of storage when compared to the Australian variety.