猕猴桃果浆中叶绿素和颜色的热降解动力学

Kinetics of chlorophyll degradation and color loss in heated kiwifruit puree

为了研究猕猴桃果浆加工中叶绿素和绿色的热降解规律,测定了不同温度(70、80、90℃)和pH值(pH值3.3、6.0、8.0)对猕猴桃果浆叶绿素含量和色差的影响。结果表明,猕猴桃叶绿素a、b和绿色值(-a*)的热降解属一级动力学反应;在相同pH值条件下,随温度升高,叶绿素a、b和绿色值(-a*)的反应速率常数(k)降低,半衰期(t1/2)缩短;随pH值增加,叶绿素a的活化能(Ea)变化范围为14.69～66.02kJ/mol,叶绿素b为40.88～54.64kJ/mol,绿色值(-a*)为48.55～64.14kJ/mol;pH值3.3时叶绿素a、b的降解和绿色值(-a*)相关性较好。猕猴桃果浆加工中适量提高pH值可减少叶绿素和绿色的损失。

Abstract： In order to investigate thermal degradation kinetics of chlorophyll and green color of kiwifruit puree during heat processing, the effects of pH value on the chlorophyll degradation and visual green color loss in kiwifruit puree were studied at 70,80 and 90℃ combined with pH value of 3.3, 6.0 and 8.0. Results showed that the breakdown of chlorophyll a, chlorophyll b and green color loss （-α^＊） values followed a first-order reaction. With the increase of temperature and pH value, the rate constant and half-life value of chlorophyll a, chlorophyll b and green color loss （-α^＊） values decreased. The activation energies ranged from 14.69-66.02 KJ/mol, 40.88-54.64 kJ/mol and 48.55-64.14 kJ/mol for chlorophyll a, chlorophyll b and green color loss （-α^＊） values, respectively. In addition, significant correlation between chlorophylls and green color loss （-α^＊） values were found for kiwifruit puree at pH 3.3. Higher pH value would benefit for preserving chlorophylls and green color in heated kiwifruit puree.