Prediction of quality in protein concentrates by laboratory procedures involving determination of soluble nitrogen

Abstract Several laboratory procedures each involving the determination of soluble nitrogen were applied to a variety of protein concentrates, and correlations were sought with the values obtained by a biological procedure, the measurement of Gross Protein Value (GPV). The Protein Quality Index (PQI) correlated well with GPV for whale meals but not for meat and fish meals. Some correlations between the results of simple solubility tests and GPV were found for oilseed meals, the best being that shown by solubility in 0.02N‐NaOH in the case of cottonseed meals. The effects of varying the conditions of the solubility test were examined.