College of Food Science and Nutritional Engineering, China Agricultural University, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Beijing, China.
J Agric Food Chem. 2012 Jan 18;60(2):593-9. doi: 10.1021/jf203405u. Epub 2012 Jan 3.
High hydrostatic pressure (HHP, treatment pressure ≤700 MPa) is approved to be the most successful commercial nonthermal processing due to its minimal modifications in nutritional and sensory quality. However, for some pressure stable enzymes such as PPO, this unique technology can hardly inactivate them at treatment pressure below of 700 MPa. This study investigated the effects of ultrahigh hydrostatic pressure (UHHP, treatment pressure >700 MPa) on the activity of Agaricus bisporus mushroom polyphenoloxidase (PPO) both in the phosphate buffer and in the mushroom puree, and on the structure of the enzyme by means of circular dichroism (CD), fluorescence emission spectra, and sulphydryl group detection. The results showed that UHHP treatment at pressure from 800 to 1600 MPa caused significant inactivation on the PPO both in the phosphate buffer and in the mushroom puree. UHHP treatment at 1400 and 1600 MPa for 1 min reduced the enzyme activity by 90.4% and 99.2% in the buffer;, however, higher enzyme activity remained in the puree after UHHP treatment at the same condition. CD and fluorescence spectra analysis showed that the secondary and tertiary structures of UHHP treated mushroom PPO were changed. The sulphydryl group (SH) detection revealed that the SH content on the surface of UHHP treated mushroom PPO was increased. It has been suggested that the inactivation of mushroom PPO by UHHP treatment at pressure higher than 1000 MPa was due to the synergistic effect of the pressure and the heat arising from pressurization, in which heat plays a major role.
高静压（HHP，处理压力≤700MPa）被认为是最成功的商业非热加工技术，因为它对营养和感官质量的改变最小。然而，对于一些压力稳定的酶，如多酚氧化酶（PPO），这种独特的技术很难在处理压力低于 700MPa 的情况下使它们失活。本研究通过圆二色性（CD）、荧光发射光谱和巯基检测，研究了超高静压（UHHP，处理压力>700MPa）对双孢蘑菇多酚氧化酶（PPO）在磷酸盐缓冲液和蘑菇纯汁中的活性以及酶结构的影响。结果表明，800-1600MPa 的 UHHP 处理对磷酸盐缓冲液和蘑菇纯汁中的 PPO 均有显著的失活作用。1400 和 1600MPa 下处理 1min 可使缓冲液中酶活性分别降低 90.4%和 99.2%；然而，在相同条件下，UHHP 处理后纯汁中的酶活性更高。CD 和荧光光谱分析表明，UHHP 处理后的蘑菇 PPO 的二级和三级结构发生了变化。巯基（SH）检测表明，UHHP 处理后的蘑菇 PPO 表面的 SH 含量增加。研究表明，1000MPa 以上压力的 UHHP 处理使蘑菇 PPO 失活是由于压力和加压产生的热的协同作用，其中热起主要作用。
