Thermal modification of foods involves heating foods to optimum temperatures so as to achieve desirable changes in the quality and flavor of the food. Thermal modification contributes to the flavor of traditional foods by inducing both desirable and undesirable flavors in the food which are responsible for the distinctive character of the food. The action of heat (cooking, frying, steaming, roasting, grilling, etc) contribute to the characteristic flavor of traditional foods by release of volatiles, induction of maillard reaction, condensation, polymerization, and degradation of organic and chemical compounds. The degree and manner to which foods are thermally modified determine the type of flavors produced, which also characterizes the distinctive flavor attributes of the food.
Lipid oxidation is the addition of oxygen molecules unto unsaturated fatty acids leading to the formation of peroxides, which are then degraded to form secondary oxidation products e.g. aldehydes, ketones, and hydrocarbons. Lipid oxidation can also contribute some desirable flavor attributes that are characteristic of processed foods.
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Can someone explain why the flavor of cooked meat seems to become more unacceptable with increased storage at refrigeration temperatures.
Hot-dog formulator, in response to your question, I am sure the reason has something to do with the action of residual enzymes on the proteins and fats of the meat. However, the action does not necessarily render the meat flavor offensive. It's rather objective as to whether refrigerated cooked meats are offensive to the consumer or not.
Meat-scientist, the term you are looking for to describe the changes that occur in cooked meat during refrigeration is 'warmed-over flavor'. I believe it's caused primarily by the action of lipoxygenase on the meat fat.
I agree with food-pro. I took a meat science class last spring and we learned all about enzymatic changes that takes place in cooked meat during refrigeration. Lipoxygenase is the primary cause of flavor change in refrigerated cooked meats like sausages, burgers, steaks, chicken breasts, etc.
Do you think the same process happens in refrigerated canned meats? I mean, since the meat is heated to a very high temperature during canning, wouldn't the enzymes (lipoxygenase, etc) be inactivated at that point?
Is there another mechanism for this 'warmed-over flavor' and does the process require the presence of oxygen to occur.
Lipoxygenase requires the presence of oxygen. It is an enzyme that catalyzes the oxidation of fats.
Just to add to what food-pro said earlier. Warmed-over flavor is the rapid onset of rancidity in cooked meat during refrigerated storage. After the cooking of meat, the progression of lipid oxidation becomes simultaneous with warmed-over flavor development and occurs primarily in the presence of oxygen.
The process takes place with the availability of oxidation promoters due to the release of heme and non-heme iron and phospholipids from disrupted muscle cell membranes.
Food-tech, I think this sort of addresses the question you raised.
However, there are some endogenous antioxidants present in meats that counteract the effect of lipid oxidation, i.e. tocopherols, carnosine, lipoic acid, and some maillard products.
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