The changes in the physicochemical properties of rices which had different amylose contents were studied when the rice was stored at 2°C and 29°C as rough rice, milled rice, defatted milled rice, and as starch. Changes in hardness index, water absorption, stickiness, viscosity, salt‐soluble protein, free fatty acids, and carbonyl compounds during storage are discussed.

The levels of reducing and nonreducing sugars, starch, soluble protein, and selected enzymes involved in the metabolism of sucrose, glucose-l-P, and glucose nucleotides were assayed in dehulled developing rice grains (Oryza sativa L. line IR1541-76-3) during the first 3 weeks after flowering. The level of reducing sugars in the grain was highest 5 to 6 days after flowering. (6) suggested that, in developing barley, the UDP glucose formed from sucrose is first converted to glucose-l-P by UDP glucose pyrophosphorylase and then the glucose-l-P is converted to ADP glucose by ADP glucose pyrophosphorylase (Fig. 1)

No abstract

High‐gelatinization temperature (GT) waxy rice starch amylopectin has higher sedimentation coefficient than low‐GT waxy rice amylopectin. Get filtration on Sepharose CL‐2B and TSK‐Gel G‐6000PW also showed higher mean molecular weights for high‐GT amylopectins than for low‐GT amylopectins. The harder texture of cooked rice products from high‐GT waxy rices, compared to the texture of products from low‐GT waxy rices, may be due to the higher molecular weight of their amylopectins.

Among three high‐amylose starches differing in gel consistency, the hard gel starch (IR42), corresponding to harder cooked rice, had higher amylograph consistency and setback, higher gel viscosity in 0.2 N KOH and higher alkali viscograph peak than starch with soft (IR32) or medium (IR36) gel consistency. IR42 starch had less extractable starch and amylose in boiling water than IR32 and IR36 starches. The three starches had similar amyloses; the differences in gel consistency were due to the amylopectin fraction. IR42 amylopectin had higher iodine affinity, more long‐chain linear fractions on isoamylase debranching and gel filtration or 1‐butanol precipitation, and less DPn 16–17 fraction than IR32 and IR36 amylopectins.