Could anyone advise me 1) what chemistry causes cooked meats (in general) to acquire a "stale" flavor when reheated; 2) is there any mitigating remedy to restore the "freshness" in that meat. Thanks.
In page 165 of his seminal book "On food and cooking", Harold McGee writes:
A the same time that cooking develops the characteristic flavors of meat, it also promotes chemical changes that lead to characteristic stale, cardboard like "warmed over-flavors" when the meat is stored and reheated...... The principal source of off-flavors are unsaturated fatty acids, which are damaged by oxygen and iron from myoglobin. This damage occurs slowly in the refrigerator and more rapidly during reheating. Meats with a greater proportion of unsaturated fats in their fat tissue -poultry and pork- are more susceptible......
There are several ways to minimize the development of off-flavors. Season the food with herbs and spices that contain antioxidant compounds. Use low permeability plastic wraps to cover the meat (Saran or PVC but not polyethylene, surprisingly permeable to oxygen) and eliminate air pockets in the package. Eat the leftovers as soon as posible.
Juan J. Iruin. San Sebastián. Spain
Dear Mr. Iruin,
I suspected that maybe it was some type of oxidation reaction going on and you’ve confirmed that for me. Thanks very much! Also, your recommendation on how to minimize the flavor deterioration in meats is most helpful.
Warmed-over flavor is tricky because it's unsaturated phospholipids oxidized via catalysis by iron in the meat. It is not related to the visible fats, so a very fatty cut and a very lean cut are both susceptible. Antioxidants can help, but a better way is often encouraging maillard reactions in the meat itself with sugars like dextrose and xylose. The maillard compounds are anti-oxidative themselves. Obviously, this works best for ground/comminuted meats or vacuum-marinated cuts.
The oxidation compounds are small aldehydes like hexanal. This can't be reversed, and rarely covered with flavors. The best bet is to interrupt the oxidation. Conditions at slaughter can also make a difference, acidity and the presence of pro-oxidant stress compounds can exascerbate the problem.
The color sheen on cut meats is also an oxidation by iron, in this case the pigments in the meat. I'm not sure whether this can be interrupted, I haven't seen any literature about this.
Thanks for your comments, Terrence. It doesn’t appear there’s anything terribly practical that one can do to completely eliminate the “warmed up taste” in meats. However, I’ll experiment with your ideas and see how that works.
Herbs and spices must help because curried meat almost always tastes better when it is warmed up the next day. There seems to have been time for the flavor to infuse into the meat and seems to improve it.
Thanks, Ramee. I’ve noticed as well that the spicier preparations don’t seem to have the flavor deterioration of the “non- spiced” meats. Apparently the spices and herbs tend to block the oxidation process whereby the meat begins to taste ‘stale’. I doubt that the presence of the spices ‘per se’ could mask the staleness, so something else is going on here.