COMPARISON OF THE PROTEIN-QUALITY OF 5 NEW NORTHERN ADAPTED NATTO SOYBEAN CULTIVARS BY AMINO-ACID-ANALYSIS

The total protein and amino acid compositions of five newly released n orthern adapted natto soybean cultivars, namely Canatto, TNS, Nattosan , AC T2853, AC Pinson, and their recurrent parent, Nattawa, have been determined. Mean protein values ranged from 30.4% in AC T2653 to 31.0% (AC Pinson), 31.0% (Nattawa), 32.1% (TNS), and 32.3% (Canatto), compa red to the protein content of Nattosan, which was 34.2%. The total nit rogen content was also variable among these cultivars, ranging from 5. 15% to 5.92%. All five new natto soybean cultivars were similar in the ir essential amino acid (EAA) content, i.e., EAA(9) = 45.0-47.0%, comp ared to the FAO/WHO reference protein pattern value of EAA(9) = 33.9% for a 2-5-year-old child. Each of the six soybean cultivars was limite d only in methionine and, to a lesser extent, in valine and isoleucine and had a protein digestibility corrected amino acid score of 91% for all cultivars, compared to the value of egg protein (97%). These resu lts suggest that the most accurate evaluation of protein quality in na tto soybeans, and possibly other legumes and cereals, is by the protei n digestibility corrected amino acid score.