Enzymic browning of apples by polyphenol oxidases
2000
Lachman, J. | Pivec, V. | Orsak, M. | Kucera, J. (Ceska Zemedelska Univ., Prague-Suchdol (Czech Republic))
Polyphenol oxidases cause enzymic browning of apples and apple juices. Their effect depends on many factors such as concentration and type of phenols, concentration and substrate specificity of PPOs, concentration of natural inhibitors of browning (ascorbic acid), oxygen concentration, pH and temperature values, content of lipidic compounds, etc. In two years (1997 and 1998) the rate of browning was investigated and with this factor connected PPOs` activity in three selected apple varieties (Idared, Gloster and Ontario) cultivated under same conditions on the experimental plot of Czech University of Agriculture in Prague-Suchdol. These parameters were investigated during a storage period of six months at +5 deg C. At the same time a relation was investigated between intensity of browning and ascorbic acid content expressed as index defined as the ratio of intensity of browning (%) to ascorbic acid content (mg/kg). There were found significant varietal and years of cultivation differences. The obtained results were compared with ascorbic acid and total polyphenol contents. Index values were in reciprocal ratio with ascorbic acid contents and in positive proportion with total polyphenol contents.
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