Selected physicochemical and antioxidant properties of Sabah upland rice in raw, cooked and fermented conditions

• Main Author: Noah Michael S. Liansim
• Format: Thesis
• Language: English; English
• Published: 2015
• Subjects: QK710-899 Plant physiology
• Online Access: https://eprints.ums.edu.my/id/eprint/40608/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/40608/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/40608/

Rice, Oryza sativa, is a staple food for more than half of population worldwide. Upland rice is mostly cultivated on hill terrain, because of their desirable characteristics and scarce reports on the physicochemical properties of upland rice varieties from Sabah, a research was done to uncovered more information. The objective of this study is to analyse the physicochemical properties (morphological traits, crude fat, moisture, ash and minerals content) and antioxidant properties (anthocyanin content and antioxidant power) of Sabah upland rice.For this study, eleven varieties (Tadong, Poroi, Nabawan, Silou, Baliung 2710, Telupid 2434, Bangalah 2719, Alubis 118, Ranau white, Nangoh red and Nangoh white) of upland rice varieties were collected from various districts in Sabah. Besides that, observations on the changes in these properties when the rice was cooked and fermented were also presented. Physicochemical were analysed with AOAC method, while the method for minerals were done by wet-ashing procedures prior to analysis. In term of morphological traits, the studied rice varieties were categorized as long to extra-long with length-to-width ratio of 2.0–3.0 and grain weight of 18.16–23.20 g per 1000 grains. The results for the selected physicochemical parameters in untreated (raw) rice varieties are in the range of as follows (in %, w/w): 0.83 – 1.14 ash; 1.23-1.81 crude fat and 2.24-51.12 total anthocyanin content (TAC). Meanwhile, minerals content (in mg/100g): 70.95-156.91 K, 38.72- 88.81 Mg, 13.40-21.92 Ca; 3.65-7.78 Na; 1.74-4.08 Zn; 1.50-4.80 Fe; 0.88-4.24 Mn; 0.314-0.96 Cu and 0.31-1.02 Se.Antioxidant property tested using FRAP method showed values in the range of 0.154 to 1.027 mmol g-1. The deeply pigmented rice varieties which were “tadong” from Tambunan (deep purple), “nangoh” from Beluran (deep red), “ragang” from Ranau (red) and “tadong” from Nabawan (red) have shown higher FRAP values compared to the non-pigmented varieties (fair or white in colour). Similarly, the pigmented rice varieties possess higher TAC; with the highest in tadong from Tambunan (51.12±1.80 mg 100g-1). The high antioxidant properties (FRAP) may be due to the high TAC in the deeply pigmented rice. Mineral contents in the pigmented rice varieties showed little differences when being compared with each other. Although the pigmented generally higher than in non-pigmented, for instance K, Ca, Na, Zn, Mn and Se were the highest in tadong rice. Cooking (boiling) had caused reduction in TAC of the rice varieties up to 73 % in tadong and a range of 16 to 68% in the rest of the rice varieties. FRAP value decreased between 40 to 73 % in the cooked rice. TAC and FRAP value decreased up to 81 % and 71 %, respectively, when the rice were fermented. As for the minerals content, the process of cooking and fermentation did not affect the content greatly. In conclusion, the physicochemical content were not affected by the type of the varieties. The pigmented varieties had a higher antioxidant properties and anthocyanin content compared to non-pigmented varieties. The process of cooking and fermentation affected the physicochemical, antioxidant activity and total anthocyanin content, however mineral contents did not affected by the type of grains and the processes.