ABSTRACTThe nitrogen (N/) extractability of several rice (Oryza sativa L.) bran samples was similar with 63, 65 and 67 of the N extracted at pH 9 from Spanish and U.S. bran and U.S. Protex (hexane‐extracted bran), respectively. Moist heat treatment, 95–100°C, of Spanish bran diminished N extractability with 21–22 extracted at pH 9 and 10. Although particle size reduction had little effect upon N extractability of heat treated bran, Wiley‐(20‐mesh) and ball‐milling the Spanish rice germ increased N extraction to 57 and 79, respectively, at pH 9 compared with 34 for the unmilled germ. With all by‐products studied nearly optimum extraction was attained at pH 9 with little or no increase observed at pH 10. Classical fractionation of the Spanish brans resulted in H2O‐, 5 NaCl‐, 60 EtOH‐, and 0.4 NaOH‐soluble fractions in ratios of 40:21:3:36 and 26:14:5:56 for the untreated and heat treated samples, respectively. Precipitation and recovery of N was optimized when sodium hexametaphosphate (0.1–0.5) was used in conjunction with HCl. Points of maximum N precipitation were pH 5 for Protex, and pH 4 for U.S. and Spanish brans and germ, in extracts which had been centrifuged at 650 ° G to remove f
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