Zeta potential ( zeta ) analysis for the determination of protein content in rice flour.

摘要

Zeta potential ( zeta ) analysis was investigated as a means of rapid determination of residual protein content of rice flour during processing of rice starch. A rice flour sample was suspended in 0.3% sodium hydroxide solution to obtain rice flour slurry which was subjected to protein extraction by a decanter for five cycles. The samples from all cycles were collected, neutralized, dried, sieved through a 200 mesh sifter and subjected to zeta analysis. The data from zeta values (y) and chemical analysis of protein content (x) from six samples of rice flour were used in a regression analysis to develop an empirical equation to express the protein content of rice flour based on zeta value alone. The result of zeta value obtained from six samples of different protein contents suspended in a buffer solution of pH 12 yielded a standard linear equation of y=-1.29x-12.51. In another method of zeta analysis, the sample was suspended in DI (deionized) water without buffer by varying pH from 2 to 8 for the zeta measurement. A linear relationship between zeta and pH was obtained together with the constant value k (slope) which could be converted into protein content (x) of rice flour by a standard linear equation of k=-1.15x-4.90.