A Modified Dye‐Binding Method for Estimating Soybean Protein¹

Abstract

Kjeldahl values that indicated 27 to 51% protein (N ✕ 6.25) were obtained in 95 soybean meal samples. A linear regression with modified dye‐binding values as independent variables was fitted to the percent protein data obtained by the Kjeldahl method. The correlation coefficient was 985. Analysis of variances of modified dye binding and Kjeldahl values showed that high drying temperature reduced the percent protein obtained by the dye‐binding method, but had little effect on the protein determined by Kjeldahl. At room temperature, there were no significan differences in values among the Kjeldahl, modified dye‐binding and Smalley soybean check series. The modified dye‐binding method can be used to estimate the protein fraction of soybean meal, or to obtain equivalent Kjeldahl values for protein estimation.

Improved dye method for estimating protein

“…Although the author has used AO-12 dye successfully on an extensive commercial basis since 1959, its use was first reported in a comparative study of the Udy and Kjeldahl methods applied to wheat in 1961 by Hart et al (6) and 1962 by Olson and Heiges (7) on barley. Other workers have applied the UDM using the improved AO-12 dyebuffer system to wheat (8), barley (9), milk (10-t2), rice (13), and soybeans (14). Mossberg (15) has utilized AO-12 dye to evaluate protein quality in cereals.…”