萝卜肉质根辣味定量分析

Changes of MTB_ITC Content and the Pungency in Radish

用４甲硫基３丁烯异硫氰酸盐（ＭＴＢ－ＩＴＣ）作为辣味的定量指标，用气相色谱法测定其含量。在生食较辣的萝卜榨汁液中ＭＴＢ－ＩＴＣ含量为１００～２００μｍｏｌ／１００ｍＬ。肉质根生长初期其含量较低，定桩期增长最快，近露肩期达最大值，然后逐步下降；在整个生长过程中肉质根不同部位的辣味物质变化趋势一致；辣味物质在萝卜皮（韧皮部）的含量大于萝卜肉（木质部），萝卜肉中，真根部的顶端含量最高，向根头部的方向逐步减少。辣味强弱与播种期早晚有关。

The contents of MTB_ITC in pungent radish ranged from 100 to 200μmoL/100mL juice. MTB_ITC content varies at different growing stages. It was very low at the early stage of root swelling, getting high rapidly at root-stable stage and reached a peak before root-shoulder exposing stage, followed by a gradual decline. The change pattern of content in all parts was the same. Content in peel of fresh root was higher than that in xylem. The MTB_ITC content in the top xylem was the highest and was decreasing gradualy toward the root-neck. Among the radishes sown at different dates, radish sown at 16th, June showed the hightest content o MTB_ITC, followed by sown at 26th, July. The radish sown at 25th, August contained the lowest level of MTB_ITC.