This is for @voltaire. Here is a synopsis of a scholarly article I lifted from a website. The allicin and resultant compounds are apparently heat stable.
The website I lifted it from was:
http://www.phytochemicals.info/research/garlic-heat-stability.php
"Garlic contains many phytochemicals with therapeutic effects, including antibacterial, antifungal, hypolipidemic, hypoglycaemic, hypoglycaemic, antithrombotic, antioxidant and anticancer. In vitro studies and epidemiological studies have suggested that garlic has anticancer properties. Garlic contains both water soluble and oil soluble sulphur compounds with anticancer activity. Because garlic is mostly consumed in its cooked form it is important to know the activity of the sulphur compounds of cooked garlic. Other studies have already shown that heating reduces the antioxidant, antibacterial and vascular protective activity. The aim of this study is to determine the heat stability of the anticancer phytochemicals in garlic by heating the garlic in a microwave or oven.
The researchers found that heating the garlic during 1 min in the microwave or 45 min in the oven resulted in complete loss of anticancer activity. Strange enough, some of the anticancer activity was retained when the crushed garlic was allowed to stand for 10 minutes before the heat treatment. The heating resulted in the destruction of the alliinase enzyme, which is responsible for the production of the active allyl sulphur compounds. During the crushing of garlic the alliinase enzyme converts the alliin of fresh garlic into allicin,which is further transformed into diallyl sulphide, allyl sulphide and other larger sulphur compounds. Allowing alliinase to work for 10 min after crushing the garlic allows enough allyl compounds to be formed, resulting in some biological activity. "
Source: Song K and Milner JA. The influence of heating on the anticancer properties of garlic.. Journal of Nutrition. 2001 March;131(3s):1054S-7S
