Metallic flavor

Stark, W., Forss, D A. 1962. A compound responsible for metallic flavor in dairy products. I. Isolation and identification. J. Dairy Res. 29, 173-180. 

Methyl-2-furyl)methanethiol has a burnt, onion, metallic flavor (Chemisis, 1961). It is a little less potent odorant than furanmethanethiol, detectable at a level of 0.050 ppb in water, developing a meaty flavor between 0.5 and 1 ppb and exhibiting a sulfury-mercaptan note at higher concentrations (Tressl and Silwar, 1981). 

It has a powerful and penetrating smokey-tarry odor, in extreme dilution sweet, woody-herbaceous, slightly animal (Arctander, 1967). It has a green, beany, metallic flavor (Chemisis, 1997). 

Analysis of Trace or Minor Components. Minor or trace components may have a significant impact on quaHty of fats and oils (94). Metals, for example, can cataly2e the oxidative degradation of unsaturated oils which results in off-flavors, odors, and polymeri2ation. A large number of techniques such as wet chemical analysis, atomic absorption, atomic emission, and polarography are available for analysis of metals. Heavy metals, iron, copper, nickel, and chromium are elements that have received the most attention. Phosphoms may also be detectable and is a measure of phosphoHpids and phosphoms-containing acids or salts. 

Citric acid is used in carbonated beverages to provide tartness, modify and enhance flavors, and chelate trace metals. It is often added to jams and jellies to control pH and provide tartness. It is used in cured and freeze-dried meat products to protect the amino acids (qv) and improve water retention. Bakers use it to improve the flavor of fmit fillings in baked goods. Because citric acid is a good chelator for trace metals, it is used as an antioxidant synergist in fats and oils, and as a preservative in frozen fish and shellfish (7) (see Antioxidaisits). 

Polyunsaturated fatty acids in vegetable oils, particularly finolenic esters in soybean oil, are especially sensitive to oxidation. Even a slight degree of oxidation, commonly referred to as flavor reversion, results in undesirable flavors, eg, beany, grassy, painty, or fishy. Oxidation is controlled by the exclusion of metal contaminants, eg, iron and copper addition of metal inactivators such as citric acid minimum exposure to air, protection from light, and selective hydrogenation to decrease the finolenate content to ca 3% (74). Careful quality control is essential for the production of acceptable edible soybean oil products (75). 

The calcium form of EDTA instead of free EDTA is used in many food preparations to stabilize against such deleterious effects as rancidity, loss of ascorbic acid, loss of flavor, development of cloudiness, and discoloration. The causative metal ions are sequestered by displacing calcium from the chelate, and possible problems, such as depletion of body calcium from ingestion of any excess of the free chelant, had it been used, are avoided. 

Citric acid also inhibits color and flavor deterioration in frozen fmit. Here again the function is to inhibit enzymatic and trace metal-catalyzed oxidation. 

Canned Fruits and Vegetables. The use of citric acid to bring the pH below 4.6 can reduce heat treatment requirements in caimed fmits and vegetables. In addition, citric acid chelates trace metals to prevent enzymatic oxidation and color degradation, and enhances the flavor, especially of caimed fmits. 

Agricultural Use. Citric acid and its ammonium salts are used to form soluble chelates of iron, copper, magnesium, manganese, and zinc micronutrients in Hquid fertilizers (97—103). Citric acid and citrate salts are used in animal feeds to form soluble, easily digestible chelates of essential metal nutrients, enhance feed flavor to increase food uptake, control gastric pH and improve feed efficiency. 

In general, exempt colorants have less coloring power than certified colorants and thus have to be used at higher concentrations. Some, particularly those of plant origin, tend to be less stable, more variable in shade, and therefore more compHcated to use than certified colorants, and are more likely to introduce undeskable flavors and odors into the products in which they are incorporated. Also, depending on thek nature and origin, exempt colorants can vary substantially in composition from batch to batch, are more likely to be contaminated with undeskable trace metals, insecticides, herbicides, and bacteria such as Salmonella and can be more difficult to obtain in steady supply compared with certified colorants. 

You may have noticed Ca-EDTA on the list of ingredients of many prepared foods, ranging from beer to mayonnaise. EDTA acts as a scavenger to pick up traces of metal ions that catalyze the chemical reactions responsible for flavor deterioration, loss of color, or rancidity. Typically, Ca-EDTA is added at a level of 30 to 800 ppm. 

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