生物谷报道：来自Warwick大学的科学家最近发现，传统的将蔬菜完全煮沸的英式烹饪方法将破坏芸苔类蔬菜——例如花椰菜、甘蓝、绿卷心菜等中的抗癌成分。
之前的研究显示，食用芸苔类蔬菜将降低肿瘤风险。这是由于芸苔类蔬菜中含有一种称为硫代葡萄糖苷的物质，它将会经由代谢产生一种抗癌物质硫氰酸盐。但是在这之前，科学家并不清楚硫代葡萄糖苷和硫氰酸盐是否受到蔬菜储存以及烹饪的影响。
来自Warwick医学院的Paul Thornalley教授以及化学系Lijiang Song博士从当地商店中购买了多种芸苔类蔬菜，然后在30分钟内运送到实验室。然后他们用不同方法烹饪，包括煮沸、蒸热、微波炉和煸炒等，来研究这些方法对其中相关物质的作用。
结果表明。煮沸对于蔬菜中的硫代葡萄糖苷的破坏最为严重。在煮沸30分钟后，硫代葡萄糖苷的损失为：椰菜77%，甘蓝58%，花椰菜75%，绿卷心菜65%。
其它烹饪方式分别为：蒸0-20分钟、微波炉加热0-3分钟、煸炒0-5分钟。这些方法都不会造成硫代葡萄糖苷的显著损失。而且在家中的室温下或是冰箱中储存也只会造成这类物质的少量流失。
但是在85度情况下会导致硫代葡萄糖苷损失达到33%。这是由于其中的蔬菜物质破碎融化造成的。科学家还发现，对于芸苔类蔬菜的一般烹饪前准备不会造成物质损失，但是如果是将它们切的很碎，则在切碎后的6小时损失量将达到75%。
英文原文：
http://www.physorg.com
Research says boiling broccoli ruins its anti-cancer properties
Researchers at the University of Warwick have found that the standard British cooking habit of boiling vegetables severely damages the anticancer properties of many Brassica vegetables such as broccoli, Brussel sprouts, cauliflower and green cabbage.
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Past studies have shown that consumption of Brassica vegetables decreases the risk of cancer. This is because of the high concentration in Brassicas of substances known as glucosinolates which are metabolized to cancer preventive substances known as isothiocyanates. However before this research it was not known how the glucosinolates and isothiocyanates were influenced by storage and cooking of Brassica vegetables.
The researchers, Prof Paul Thornalley from Warwick Medical School at the University of Warwick and Dr Lijiang Song from the University of Warwick’s Department of Chemistry bought Brassica vegetables, (broccoli, Brussel sprouts, cauliflower and green cabbage) from a local store and transported them to the laboratory within 30 minutes of purchasing. The effect of cooking on the glucosinolate content of vegetables was then studied by investigating the effects of cooking by boiling, steaming, microwave cooking and stir-fry.
Boiling appeared to have a serious impact on the retention of those important glucosinolate within the vegetables. The loss of total glucosinolate content after boiling for 30 minutes was: broccoli 77%, Brussel sprouts 58%, cauliflower 75% and green cabbage 65%.
The effects of other cooking methods were investigated: steaming for 0–20 min, microwave cooking for 0–3 min and stir-fry cooking for 0–5 min. All three methods gave no significant loss of total glucosinolate analyte contents over these cooking periods.
Domestic storage of the vegetables at ambient temperature and in a domestic refrigerator showed no significant difference with only minor loss of glucosinolate levels over 7 days.
However the researchers found that storage of fresh vegetables at much lower temperatures such as 85 °C (much higher than for storage in a refrigerator at 4–8 °C) may cause significant loss of glucosinolates up to 33% by fracture of vegetable material during thawing.
The researchers found that preparation of Brassica vegetables had caused only minor reductions in glucosinolate except when they were shredded finely which showed a marked decline of glucosinolate levels with a loss of up to 75% over 6 hours after shredding.
Source: University of Warwick
