Sequential hydrolysis of swine carcass samples and determination of amino acid concentrations using pre-column derivatization with phenyl isothiocyanate

Comparing amino acid (AA) retention levels in pig carcass to true ileal dig estible AA intake provides an estimate of the marginal efficiency of AA uti lization. Accurate analysis of AA levels in the carcass samples is critical . However, the standard 24 h of hydrolysis does not always provide maximum AA values. A study was carried out to investigate the effect of hydrolysis time on AA measurements in pig carcass. Correction factors to standardize A A levels to 24 h of hydrolysis were also determined. Ground carcass samples were hydrolysed with 6 mol litre(-1) hydrochloric acid (HCl) in a 110 degr ees C oven for nine different time periods. Pre-column derivatization with phenyl isothiocyanate (PITC) was used to determine AA concentrations in all of the samples. Hydrolysis time significantly affected (P < 0.001) AA leve ls. The highest levels (P > 0.05) of valine, isoleucine, serine, glycine, t hreonine, alanine, arginine, proline, histidine and phenylalanine were not observed with 24 h hydrolysis. Therefore, correction factors and sequential hydrolysis curves are important for these amino acids. In conclusion, the effect of hydrolysis time should be considered in amino acids analysis. (C) 2000 Society of Chemical Industry.