Effect of soaking temperature and Germination time on minerals and cooking quality of Hashemi brown rice variety

Introduction: Brown rice has a higher nutritional value than white rice, but due to its harder texture and longer cooking time, it is often less accepted by consumers. It seems that germination time than white rice effects on textural and nutritional parameters improvement. In this research, in order to improving the nutritional value and cooking quality of brown rice, the germination process was used.

Materials and methods: Rough rice and brown rice samples of Hashemi variety were soaked at temperatures of 30 °c and 45° c for 24 and 48 hours for germination. So the samples were dried. In order to check the nutritional value of germinated brown rice samples and germinated peeled paddy (8 samples) and control sample (untreated brown rice), minerals such as iron, copper, zinc and manganese, and the cooking quality included solids loss factors, water absorption ratio, Volume expansion ratio and Alkali digestion were measured in the form of a randomized complete design with three replications. For data statistical analysis, analysis of variance was performed using SPSS software and comparison of means by Duncan test at 5% probability level.

Research findings: The highest amount of grain iron in the rough rice germination process was related to the sample with a soaking temperature of 45 °C for 24 hours (65.8 ppm) and the highest concentration of iron in brown rice germination processing belonged to the sample with soaking temperature of 30 °C for 24 hours (65.8 ppm). According to the results of this research, germination of brown rice in Hashemi variety had a negative effect on the amount of manganese in the seeds and in the studied samples, manganese was lower than the control sample. The highest concentration of zinc was observed by germinating rough rice at 45°C at 24 and 48 hours (30.8 ppm, 30.29 ppm, respectively). By germinating rough rice, no significant difference was observed in the amount of copper in the grain compared to the control sample. However, the highest amount of copper was found in brown rice germination at 30°C for 48 hours (13.5 ppm), which was significantly different from the control sample.

The highest amount of water absorption during cooking was related to the germinated brown rice sample with a soaking temperature of 45°C for 48 hours (3.5) And the highest percentage of solids loss belonged to the sample of brown rice germinated at 45°C for soaking temperature 24 hours with an average of 14.2%. Also, the highest amount of alkali digestion was observed for brown rice sprouted at 45°C for 24 and 48 hours.

Conclusion: The results showed that germination caused to increase mineral elements, especially iron, zinc and cooking quality and reduce cooking time in brown rice. Among the samples, the best conditions for germination in order to increase minerals were observed in brown rice germinated with rough rice raw material at a soaking temperature of 45°C for 24 hours. And the best cooking quality was belong to germinated brown rice with rough rice at soaking time of 48 hours at temperature of 45°C. The lowest cooking time belonged to sprouted brown rice at 45°C.Therefore, by choosing the optimal conditions in the germinating process, it is possible to create a positive effect in increasing the nutritional properties and cooking quality of the desired variety.