Effect of time, temperature and extraction method on the trichloroacetic acid-soluble nitrogen of cheese

The effect of time, temperature and extraction method on the level of 12% trichloroacetic acid-soluble nitrogenous compounds (TCA-SN) of cheese was investigated. Analysis of the variance indicated significant differences due to all main effects (P < 0.05) but the differences induced by time and temperature were very small and of no practical interest. On the contrary, extraction method substantially affected TCA-SN. The composition of cheese extracts significantly varied both quantitatively and qualitatively; cheese to water ratio, pH of the extract, nature of the extractant (water or citrate buffer pH 7.0), and NaCl content affected not only the amount but also the kind of peptides extracted, as shown by the reversed-phase high performance liquid chromatography. However, the presence of peptides eluted with more than 30% acetonitrile had no effect on the level of TCA-SN. Specification of the cheese extraction method whenever data are presented for TCA-SN is considered important. (C) 1999 Elsevier Science Ltd. All sights reserved.