Effect of parboiling and rice varieties on physicochemical and starch digestive properties of ready to eat rice

Abstract

n recent years, people tend to consume ready to eat (RTE) rice. However, several disadvantages were encountered in RTE rice especially in texture and starch digestive properties, thus modifying the processing method is needed. This study was conducted to developing RTE rice processing using parboiling technique and to investigate the effect of parboiling and rice varieties on RTE rice in retort pouch characteristics. Brown rice grains of Pitsanulok (PSL) (29.17% amylose), Homnin (HMN) (21.22% amylose), and Sinlek (SLK) (21.91% amylose) were undergo parboiling and subsequently prepared into RTE rice packed in retort pouch. Their physicochemical characteristics, antioxidant activities, starch digestive properties, and sensory qualities were evaluated. Parboiling of brown rice gave significant changes in some physicochemical characterics including changes in moisture and ash content, decreased in hardness, adhesiveness, and lightness value. Each rice variety gave different value of physicochemical characteristics significantly. Compared to unparboiled rice samples, TPC of parboiled PSL was decreased, whilst parboiled HMN and SLK were increased. Furthermore, parboiling decreased the antioxidant capacities based on DPPH and FRAP activity methods. Rice variety of HMN has the highest TPC, DPPH, and FRAP, followed by SLK and PSL respectively. Furthermore, parboiling did not affect the resistant starch (RS) and glycemic index (GI) significantly. However, rice varieties affect the RS and GI significantly with PSL has the highest RS followed by SLK and HMN respectively (2.09-2.74, 0.38-0.60, and 0.34-0.59 g/100g sample, respectively) and HMN has the lowest GI followed by PSL and SLK respectively (83.84-89.54, 85.79-96.52, and 88.99-97.49, respectively). Based on sensory qualities, HMN-UP has the highest sensory scores compared to other products. Therefore, there was a possibility to apply parboiling technique into the specified rice variety to maintain the antioxidant, improve RS and GI, and obtain desirable sensory qualities. However, optimization of parboiling method is needed to obtain desirable results.