Warmed-over flavor is an unpleasant characteristic usually associated with meat which has been cooked and then refrigerated. The deterioration of meat flavor is most noticeable upon reheating. As cooking and subsequent refrigeration is the case with most

convenience food Convenience food, also called tertiary processed food, is food that is commercially prepared (often through processing) to optimise ease of consumption. Such food is usually ready to eat without further preparation. It may also be easily p ...

s containing meat, it is a significant challenge to the processed food

industry Industry may refer to: Economics * Industry (economics), a generally categorized branch of economic activity * Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery * The wider industrial sector ...

. The flavor is variously described as "rancid," "stale," and like "cardboard," and even compared to "damp dog hair." Warmed-over flavor is caused by the

oxidative Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

(fatty substances) in the meat into chemicals (short-chain

aldehydes In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

or ketones) which have an unpleasant taste or odor. This decomposition process begins after cooking or processing and is aided by the release of naturally occurring

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

in the meat.

Occurrence of warmed-over flavor

The occurrence of warmed-over flavor begins as lipids, primarily lipids from the

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

of cells in the meat, are attacked by

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

. This process is aided by the release of

from iron-containing proteins in the meat, including myoglobin and

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

. The iron is released by the heat of cooking, or by mechanical grinding. The free iron then acts as a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

, or promoter, of oxidation reactions. The reactions break down some of the fats in the meat to form primary oxidation products. These chemicals are not directly responsible for the objectionable taste. Instead, they subsequently further decompose to secondary oxidation products including " alcohols, acids, ketones,

lactone Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the co ...

s and

unsaturated hydrocarbon 300px, Structure of an ethene molecule, the simplest unsaturated hydrocarbon Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. The term "unsaturated" means more hydrogen atoms may ...

s which produce the armed-over flavor" Many of these compounds, including

pentanal Pentanal (also called valeraldehyde) is the organic compound is an alkyl aldehyde, molecular formula C5H10O. It is used in flavorings, resin chemistry, and rubber accelerators. Its smell is described as fermented, bready, fruity, nutty, berry. ...

, hexanal, pentylfuran, 2-pentylfuran, 2-octenal and 2,3-octanedione have a strong odor and can be tasted at concentrations as low as 1 part per billion.

Prevention

Warmed-over flavor can be prevented by the addition of

preservatives A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or by ...

to processed meat. Many of the preservatives are antioxidants, ranging from

tocopherol Tocopherols (; TCP) are a class of organic chemical compounds (more precisely, various methylated phenols), many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rat ...

s (related to vitamin E) to plum juice to industrial additives such as

butylated hydroxytoluene Butylated hydroxytoluene (BHT), also known as dibutylhydroxytoluene, is a lipophilic organic compound, chemically a derivative of phenol, that is useful for its antioxidant properties. BHT is widely used to prevent free radical-mediated oxidat ...

(BHT),

butylated hydroxyanisole Butylated hydroxyanisole (BHA) is a synthetic, waxy, solid petrochemical. Its antioxidant properties have caused it to be widely used as a preservative in food, food packaging, animal feed, cosmetics, pharmaceuticals, rubber, and petroleum produ ...

(BHA) and propyl gallate. Other preservatives such as sodium pyrophosphate and

sodium hexametaphosphate Sodium hexametaphosphate (SHMP) is a salt of composition Na6 PO3)6 Sodium hexametaphosphate of commerce is typically a mixture of metaphosphates (empirical formula: NaPO3), of which the hexamer is one, and is usually the compound referred to by t ...

may work by binding iron and preventing it from catalyzing the chemical reactions which lead to warmed-over flavor; as these compounds are generally more soluble in water than the fat-soluble antioxidant preservatives, they may be more readily used to prevent oxidative decomposition in meat. Nitrites, a curing agent for meat, may prevent the development of warmed-over flavor by preventing the release of iron during cooking.

References

{{Reflist Gustation Meat

Occurrence of warmed-over flavor

Prevention

See also

References