EFFECT OF HIGH-PRESSURE TREATMENT ON THE TRYPTIC HYDROLYSIS OF BOVINEBETA-LACTOGLOBULIN AB

The effects of high-pressure treatment on the tryptic hydrolysis of bo vine beta-lactoglobulin AB were studied. Isostatic pressure (100-800 M Pa, 15 min) was applied to the protein substrate prior to its hydrolys is, as well as following its digestion at atmospheric pressure. Hydrol ysis (100 min at 40 degrees C) was also conducted under high pressure (100-400 MPa). To characterize the hydrolysates on a molecular level, peptide mapping by RP-HPLC was coupled on-line to detection by electro spray ionisation mass spectrometry. Under pressures up to 400 MPa, try ptic hydrolysis of beta-lactoglobulin was increased with an optimum at 300 MPa. Analysis of the digests showed that the enhanced hydrolysis was due to accelerated breakdown of large intermediate hydrolysis prod ucts into final tryptic peptides. Among others, it was found that unde r these conditions the Tyr20-Ser21 peptide bond splitting was complete , resulting to entire conversion of Val15-Arg40 intermediate into Val1 5-Tyr20 and Ser21-Arg40 end-products. Increasing pressures applied dur ing pre-pressurization (100-800 MPa) resulted in small but progressive reduction in residual intact beta-lactoglobulin, but no change in the peptide profile of the hydrolysates obtained was observed. Similar to this, post-pressurization of the tryptic hydrolysate had no measurabl e effect on the peptide profiles. (C) 1998 Elsevier Science Ltd. All r ights reserved.