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)

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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.

Some propewties of 3-P-glycerate phosphatase from developing caryopsis of rice (Oiyza sativa L., variety IR26) were studied. The enzyme was found to be soluble and not bound to starch, and concentrated mainly in the pericarp-aleurone layer; its maximum activity was at 12 to 14 days after flowering. Contents of 3-P-glycerate and chlorophyll were highest in the grain at 7 to 8 days after flowering when starch synthesis was at a maximum. The enzyme was purified about 100-fold by precipitation with 50 to 80% ammonium sulfate, followed by chromatography through Sephadex G-200 and CM-Sephadex C-50. The pH optimum was from 5.7 to 6 and no cation was required for activity. The purified preparation had an apparent Km of 2.85 mM and was inhibited by Cu2+, Hg2+, Zn2+, Fe3+, molybdate, and F-. The enzyme also exhibited high activity toward UTP, ATP, and p-nitrophenyl Grains were tagged at flowering and sampled in the mornings at specified intervals up to 21 days after flowering. These tagged grains were used as standards to classify periodic bulk samples used subsequently in the developmental study. The samples were dehulled and classified at 0 to 4 C. Duplicate batches of grains were analyzed at each developmental stages. For the study of enzyme distribution in the grain, samples at 9 to 10 days after flowering were dissected into their respective components: the hull, pericarp-aleurone layer, embryo, and endosperm. Statistical analyses were run on the data and LSD (5%) were calculated.Chemical Analysis. 3-P-Glycerate was extracted from freshly dehulled grains with 20% HCIO4 at 0 to 4 C and immediately assayed by the method of Latzko and Gibbs (1 1). Samples were taken in the mornings. Grains were dehulled directly from intact plants and the caryopses (dehulled grains) were immediately frozen in Dry Ice. Chlorophyll was also extracted from fresh grains by boiling 80% (v/v) aqueous acetone and was determined after Bruinsma (2). Soluble protein of the redissolved trichloroacetic acid precipitate (for the crude extract) and of the enzyme solutions (for the more purified fractions) was measured using the method of Lowry et al. (12).Enzyme Assay. 3-P-Glycerate phosphatase was assayed at 30 C with 10 Atmol sodium cacodylate buffer (pH 5.5) in a total volume of 1 ml. The reaction time was 15 min for the crude enzyme and 12 min for the more purified preparations. The reaction was terminated by adding 0.25 ml 10% trichloroacetic acid and the precipitate was removed by centrifuging at 2,500g for 15 min. Phosphate released was determined in the supernatant as described by Anderson and Tolbert (1).

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