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ThesisItem Embargo Ultrasound-assisted accelerated aging of paddy (rice): modification of structural and textural properties(Punjab Agricultural University, Ludhiana, 2023) Ramandeep Kaur; Bobade, HanumanRice (Oryza sativa) is a major cereal crop and a staple food for most of the world’s population. Most of the produced rice is consumed after cooking. However, the rice milled from freshly harvested paddy cooks to pasty consistency with undesirable eating qualities. Therefore, the commercial millers are compelled to store the freshly harvested paddy for at least 4-6 months of period under controlled conditions of temperature and relative humidity to obtain the rice with better cooking and textural properties. This storage of paddy, which is also called aging, is cumbersome from technical as well as economic point of view. The various accelerated aging techniques have been developed but with certain limitations. The ultrasonication is one of the green, novel, non-destructive, quick, adaptable, and promising technologies being applied in the food industry. The ultrasound processing has ability to bring changes in the milling, cooking, textural, and nutritional properties of rice. Therefore, the present investigation was undertaken for ultrasound assisted aging of paddy which was treated ultrasonically for 30, 60, and 90 min durations at different temperatures of 30, 40, and 50oC and the ultrasound process treatment using response surface methodology (RSM). The appropriate models were developed and used to optimize the best conditions of ultrasound treatment by running ANOVA based on the milling and cooking characteristics of rice. The head rice yield increased for increasing temperature from 30 to 50oC while decreased beyond 60 min ultrasound duration. The broken rice decreased with increasing temperature while increased with increase in ultrasound period from 60 to 90 min. Milling efficiency was increased with increase in time and temperature of ultrasound treatment. The ultrasound treatment decreased cooking time with the increase in time and temperature while increase the water uptake ratio, volume expansion ratio and cooking loss in rice with the increase in time and temperature of ultrasound treatment. The best-optimized ultrasound conditions by RSM were 60 min 50oC which increased the head rice yield, decreased the broken heads, and improved the milling efficiency and cooking qualities. The ultrasound treatment improved rice flour's functional properties (WAC, OAC, and SP). The phenolic content and antioxidant activity of rice increased significantly (p<0.05) with ultrasound time and temperature increase while decreased in rice obtained by milling of six month stored paddy. The in vitro digestibility of rice was also improved by ultrasound treatment as ultrasound treatment increased the content of rapidly digestible starch (RDS). Slowly digestible starch (SDS) and resistant starch (RS) also varied with various ultrasound conditions. Whereas, RD observed to be higher and RDS observed to be lower in six month stored paddy. Furthermore, ultrasound treatment significantly (p<0.05) improved the textural properties of rice. The pasting profile and color properties are also impacted by ultrasound treatment under various conditions. The pasting properties of rice obtained by ultrasound treatment for 60 min are similar to the rice obtained from paddy stored for six months. The structural changes in rice from ultrasound treated paddy witnessed by SEM, X-ray diffraction, and FTIR analysis. Ultrasound treatment for 60 min at 50oC temperature can be used as an alternative for the natural aging of paddy to accelerate the process.
