不同贮藏温度对雪胆块茎褐变相关酶及底物的影响

Effects of different storage temperatures on browning-related enzymes and substrates of fresh-cut tubers of Hemsleya chinensis

  • 摘要: 【目的】研究贮藏温度对雪胆块茎褐变相关酶、底物及有效成分的影响,为控制褐变、提高雪胆块茎中药材的稳定性提供理论支持。【方法】将鲜切雪胆块茎放置在3个贮藏温度(-20、4和25℃)下,分别于贮藏第0、2、4、8和10 d时取样,测定其褐变度、过氧化物酶(POD)活性及丙二醛(MDA)、总酚、雪胆甲素和雪胆乙素含量等指标,并进行褐变度与其他测定指标间的相关分析。【结果】随着贮藏时间的延长,鲜切雪胆块茎褐变度均上升,贮藏至第10 d时,25℃下贮藏的鲜切雪胆块茎褐变度较-20和4℃显著升高(P<0.05,下同); 3个贮藏温度下的鲜切雪胆块茎POD活性均呈先上升后下降的变化趋势,整个贮藏期间25℃下的POD活性始终显著高于-20和4℃;贮藏温度越高,鲜切雪胆块茎的MDA含量越大,贮藏4~10 d,25℃的MDA含量显著高于-20和4℃,但-20与4℃的MDA含量间无显著差异(P>0.05,下同);贮藏第4 d后,25℃下贮藏的鲜切雪胆块茎总酚含量也始终显著高于-20和4℃。25℃下贮藏的鲜切雪胆块茎中雪胆甲素含量在第4 d后急剧上升,在第6 d达最大值(1.1410 mg/g),显著高于-20和4℃,而雪胆乙素含量在贮藏2 d后开始急剧增加,至第8 d时达0.01143 mg/g,也显著高于-20和4℃。相关分析结果表明,3个贮藏温度下的褐变度均与贮藏时间呈极显著正相关(P<0.01,下同),与总酚、雪胆甲素和雪胆乙素含量均无显著相关性;-20和4℃的褐变度与POD活性分别呈极显著和显著负相关,-25℃的褐变度与POD活性无显著相关性;-20℃的褐变度与MDA含量呈显著负相关。【结论】低温(-20和4℃)下贮藏,可通过抑制褐变关键酶POD活性,或减少褐变底物酚类物质的生成而有效控制鲜切雪胆块茎的褐变,以-20℃的控制褐变效果更佳。

     

    Abstract: 【Objective】 To investigate the factors that affected the browning of tuber of Hemsleya chinensis under storage temperature, and to study the mechanism and change law of the browning process, to provide theoretical support for controlling browning and improving the stability of tuber of H. chinensis.【Method】The fresh-cut tubers of H. chinensis were placed at three different storage temperatures (-20, 4 and 25 ℃) , and samples were taken on the 0, 2nd, 4th, 8th, and 10th d of storage respectively, to study the degree of browning, changes in peroxidase(POD) activity, malondialdehyde (MDA), total polyphenols,cucurbitacin IIa and cucurbitacin IIb contents, and the correlation analysis between the degree of browning and measured indexes was carried out.【Result】 With the prolongation of storage time, the browning degree of fresh-cut tubers of H. chinensis increased. At the 10th d,the browning degree of fresh-cut tuber of H. chinensis stored at 25 ℃ was significantly higher than that at -20 and 4 ℃(P<0.05,the same below). At this time, the POD activities of H. chinensis tubers at three temperatures showed a trend of first increasing and then decreasing, and the POD activities during the whole storage period were significantly higher than those under -20 and 4 ℃. The higher the storage temperature, the greater the MDA content of fresh-cut tubers of H. chinensis,stored at 4-10 d,the MDA content at 25 ℃ was significantly higher than -20 and 4 ℃, but there was no significant difference in MDA content between -20 and 4 ℃(P>0.05,the same below);the total phenolic content of resh-cut tubers of H. chinensis stored at 25 ℃ after 4 d was always significantly higher than-20 and 4 ℃. At 25 ℃, the content of cucurbitacin IIa in fresh-cut tubers of H. chinensis increased sharply after 4 d and reached the maximum value on day 6(1.1410 mg/g),significantly higher than at -20 and 4 ℃,the content of cucurbitacin IIb began to increase sharply after 2 d of storage,and on day 8,the content of cucurbitacin IIb reached 0.01143 mg/g,which was significantly higher than at -20 and 4 ℃. The results of correlation analysis showed that the BD at the three storage temperatures had an extremely significant positive correlation with the storage period(P<0.01,the same below), but no significant correlation with total polyphenols,cucurbitacin IIa and cucurbitacin IIb contents. BD had extremely significant and significant correlation with POD activity at -20 and 4 ℃ respectively,BD at -25 ℃ had no significant correlation with POD activity,BD at -20 ℃ had significant negative correlation with MDA content.【Conclusion】 Storage at low temperatures(-20 and 4 ℃)can inhibit the activity of POD,a key enzyme in browning,or reduce the production of browning substrate phenolic substances to effectively control the browning of fresh-cut tubers of H. chinensis. The browning control effect is better at -20 ℃.

     

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