The effects of combined high pressure (0.1~600 MPa) and temperature (20~60 ℃) treatment for 20 min on beef protease activities were studied. The results showed that the protease activities decreased with increasing pressure up to 400 MPa at room temperature, after which there was no significant change of them. The content of free amino acid increased significantly at 200 MPa and then the increased speed decreased with the pressure increasing.400 MPa or higher pressure treatment at room temperature resulted in the increase of tryptic digestibility of protein in beef extract. There was no significant effect on protease activities and free amino acid content in beef after pressurized at 200 MPa, 40 ℃, but the protease was almost completely inactivated at pH 7.5 and free amino acid content reduced rapidly after treated at 600 MPa, 40 ℃. Part of protease activities survived in beef muscle when heated at 60 ℃. They did not change significantly when treated at 200 MPa, 60 ℃, but the free amino acid content increased obviously. Treatment of 600 MPa at 60 ℃ resulted in the inactivation of almost all the proteases and the free amino acid content also decreased markedly. The similar changes of tryptic digestibility of protein in beef extract were found when pressure applied at 40~60 ℃. 200 MPa treatment did not cause significant changes and 600 MPa treatment induced the tryptic digestibility of protein marked increase. These results suggested that high pressure treatment combined with heating could regulate proteases activities of beef and improve its quality.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |