Nonenzymatic Degradation of Citrus Pectin and Pectate during Prolonged Heating: Effects of pH, Temperature, and Degree of Methyl Esterification
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- 作者：Jerome V. Diaz ; Gordon E. Anthon ; Diane M. Barrett
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2007
- 出版时间：June 27, 2007
- 年：2007
- 卷：55
- 期：13
- 页码：5131 - 5136
- 全文大小：105K
- 年卷期：v.55,no.13(June 27, 2007)
- ISSN：1520-5118
文摘
The underlying mechanisms governing nonenzymatic pectin and pectate degradation during thermaltreatment have not yet been fully elucidated. This study determined the extent of nonenzymaticdegradation due to 
es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-elimination, acid hydrolysis, and demethylation during prolonged heating ofcitrus pectins and its influence on physicochemical properties. Solutions of citrus pectins, bufferedfrom pH 4.0 to 8.5, were heated at 75, 85, 95, and 110 es/entities/deg.gif">C for 0-300 min. Evolution of methanol andformation of reducing groups and unsaturated uronides were monitored during heating. Molecularweight and viscosity changes were determined through size exclusion chromatography and capillaryviscometry, respectively. Results showed that at pH 4.5, the activation energies of acid hydrolysis,es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-elimination, and demethylation are 95, 136, and 98 kJ/mol, respectively. This means that at thispH, acid hydrolysis occurs more rapidly than es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-elimination. Furthermore, the rate of acid hydrolysisis diminished by higher levels of methyl esterification. Also, citrus pectin (93% esterified) degradesprimarily via es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-elimination even under acidic conditions. Acid hydrolysis and es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-elimination causedsignificant reduction in relative viscosity and molecular weight.