Ph.D. Dissertation:

Production of reconstructed rice grain fortified with fiber and micronutrients including vitamin D and zinc and evaluation of functional٫ textural٫ and sensory properties of cooked product

Rice is a major source of energy for about half of the world’s population, mostly Asians. Rice cracks during milling followed by breakage has turned into a great concern for rice growers. A suggested solution to reduce wastes is to produce rice grains from milling wastes using the extrusion cooking technique. The effects of extrusion cooking variable, i.e. moisture at inlet, on qualitative properties of rice including moisture content, bulk density, water uptake and water solubility index (WSI), lateral expansion, cooking loss, total color difference, and texture/organoleptic properties of the products were analyzed to determine the optimal conditions. To this end, different ratios of rice flour, guar gum, arabic gum, modified starch, mono- and di-glyceride emulsifiers, and titanium dioxide were used. Addition of 0.4% guar and 0.1% arabic gums to the extruded rice formulation had an effective role in improving most of the physicochemical, texture and sensory characteristics. Moreover, formulation was optimized by rice bran enrichment. Results showed that the 6% addition of rice bran to the optimal treatment significantly increased adhesiveness and the dark color of the extruded products, whereas increasing the rice bran content from 2% to 4% left no undesirable effects on the optimal treatment (30-G4A1). Additionally, in the sensory analysis of the effect of different bran contents on the optimal treatment, it was found that the scores for color, texture and total acceptance were more satisfactory in the samples containing 4% bran. Rice was enriched by food supplements such as zinc and vitamin D3. Results showed that the zinc oxide content dropped from 20 to 11 mg/100g after draining the rice samples due to its solubility in water. A part of vitamin D3 content was also lost to heat, and, following the cooking process, the rest of it was lost during draining and reheating. In general, if adding 1000 IU/100g to extruded rice, the remaining vitamin D3 content after cooking is 885.17 IU/100g enough for supplying the daily intake of an adult.

Keywords: Extrusion, Vitamin D3, Zinc, Guar gum, Arabic gum