光对采后果蔬叶绿素降解动力学研究

Kinetics for photo-degradation of chlorophyll in postharvest fruit and vegetable

叶绿素对光不稳定,易降解,为探讨引起该类色素降解的主要因素,并在生产、加工及贮藏中予以克服和避免,更好地保证产品在货架期内的感官品质,提高经济效益。该试验利用紫外分光光度计、全自动色差计(CIE-L*a*b*)和高效液相色光谱法定量分析叶绿素光降解的变化情况,并对叶绿素光降解动力学过程进行了分析。结果表明:叶绿素光降解反应符合一级动力学模型;紫外线对叶绿素有很强的破坏作用,可见光中蓝光、红光对该色素降解作用次之,而红外线对叶绿素破坏作用较小;光照强度为500、1000、1500、2000、2500、3000、3500、4000、4500、5000 lux,温度为25℃的条件下,叶绿素降解半衰期分别为16.9、14.1、11.5、9.8、8.8、8.2、7.1、6.0、5.2、4.0 h;相同条件下叶绿素a的降解速率约为叶绿素b降解速率的3～4倍;叶绿素在温度60℃以下降解不明显;氧气在叶绿素光降解过程中有着非常重要的作用。本试验结果对绿色果蔬包装材料的选择和产品感官品质控制有一定的参考价值。

The chlorophyll showed unstability to light irradiation in processing and storage, it was determined by UV spectrophotometer and CIE-L^＊a^＊b^＊ and HPLC, and the kinetic models of chlorophyll photo-degradation with different monochromatic lights and light intensity were studied. The results indicated that chlorophyll photo-oxidation followed a first-order model. The chlorophyll was broken down seriously during ultraviolet radiation as well as blue and red light through visible spectrum, but was influenced slightly by infrared rays. The degradation speed was inconsistent among different light intensity and the half life of chlorophyll under 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000 lux was 16.9, 14.1, 11.5, 9.8, 8.8, 8.2, 7.1, 6.0, 5.2, 4.0 h, respectively. The speed of chlorophyll a degradation was almost three or four times faster than that of chlorophyll b under the same conditions. Chlorophyll degradation wasn＇t evident under 60℃ and concentration of oxygen affected photo-degradation seriously. The conclusion supplied useful reference on choosing fruits and vegetables wrapping materials and facilitating sense quality on green fruits and vegetables.