BIOCHEMICAL MECHANISM AND SUBSTANCES DETERMINATION OF ENZYMIC BROWNING OF YALI PEAR ( PYRUS BRETSCHNEIDERI REHD. )
Wu Gengxi,Zhou Hongwei, and Wang Jianmin ( Shandong Agricultural University, Taian 271018 )
Polyphenol oxidases and phenols extracted from Yali pear could react on each other,and the products became brown. Browning reaction could be stopped by an inhibitor.Enzymic browning was an important reason by which the core of fruits got "black" . Phenols contents in the core was 2.7 times higher than that in the flesh. The phenomenon of browning from core to flesn was related to the difference of phenols contents in these two parts. In the beginning of browning period,the contents of phenols increased and polyphonic oxidases activity showed a peak.Browning of Yali pears was an biochemical reaction in which phenol oxidations were catalyzed by polyphenol oxidases. The phenol isolated from the core was determined by paper chromatography, ultra-violet and infrared spectrum. The phenol is chlorogenic acid.