pH对马铃薯‘转心乌’块茎花色苷颜色变化及降解速率的影响

用分光光度法在体外研究了不同pH条件下马铃薯'转心乌'块茎花色苷颜色呈现和降解速率的变化,以探讨马铃薯'转心乌,块茎颜色呈现的机理.结果显示:在pH 2.0时,该花色苷呈现最强烈的红色.随着pH从0增加到13.0,该花色苷在可见光区的最大吸收波长(λvis max)依次出现红移、蓝移,然后消失,在可见光区的最大吸收波长处的吸光值(Aλ,vis max)呈现为一条单峰曲线,峰值在pH 2.0处.当原始pH值被恢复到2.0后,如果原始pH小于或等于5.0,花色苷的红色均被恢复得更浓烈,λvis max不同程度地趋向537 nm,Aλ,vis max增加;如果原始pH大于或等于6.0,花色苷的红色根本不能被恢复,λvis max几乎不变,Aλ,vis max仍然维持低水平.在15℃、黑暗中,该花色苷在pH 0～5.0条件下均随时间推移而降解,在pH 2.0时的降解速度最慢;当pH小于或等于3.0时,该花色苷总体上降解缓慢,而且降解过程基本符合一级反应动力学.研究表明,'转心乌'块茎花色苷在可见光区的吸收光谱和在15℃、黑暗中的降解速度均具pH依赖性.

Effects of pH on the Coloration and Degradation Rate of the Stem Tuber Anthocyanins of Solanum tuberosum L. 'Zhuanxinwu'

In order to probe the mechanism of the stem tuber coloration of Solanum tuberosurn L. ' Zhuanx-inwu', we studied the changes of the coloration and degradation rate of the stem tuber anthocyanins of S. Tuberosurn 'Zhuanxinwu' under different Ph conditions in vitro with spectrophotometry. The results showed that:at Ph 2.0,the anthocyanins displayed the strongest red. Along with the increase of Ph values from 0 to 13.0,the maximal absorption wavelength in visible light (λvis max) of the anthocyanins expressed bathochromic shift and hypsochromic shift orderly, then disappeared, and the absorbance values at the max-imal absorption wavelength in visible light (Aλ,vis max) exhibited a single-peak curve, with the peak at Ph 2.0. After the primitive Ph values were restored to 2.0,if the primitive Ph was lower than or equal to 5.0,the red hues of the anthocyanins were all resumed to much stronger,the Aλvis max altered toward 537 nm in different degrees,and the Aλ,vis max inereased; If the primitive Ph was higher than or equal to 6.0,the red hues of the anthocyanins could not be resumed at all,the λvis max did not almost change,and the low Aλ,vis max also remained unchangeable. Being placed at 15℃ in darkness,the anthocyanins at the Ph values of 0～5.0 degraded totally along with time. The degradation rate at Ph 2.0 was the slowest,and when the Ph was lower than or equal to 3.0, the anthocyanins degraded slowly as a whole. In addition, the degradation cour-ses of the anthocyanins basically approximated first-order reaction kinetics. In a word, the research indica-ted that the visible light absorption spectra and degradation rates of the stem tuber anthocyanins of S. Tu-berosum L. 'Zhuanxinwu' at 15℃ in darkness are all Ph-dependent.