During meat curing

Tissue proteins are hydrolysed by thiol proteases called cathepsins (denoted by the letters B, D, L, H, S, M and T). They also act in post-mortem autolysis of proteins during meat curing. 

During the curing process, some of the nitrites are converted to nitric oxide. This combines with the myoglobin proteins in the muscle of the meat to form the deep red nitric oxide myoglobin, which causes cured meats such as ham to turn pink during the smoking process. 

Manufacturers Comments Meat curing (possible during paint-stoving Manufacturers Comments Rapid cure. 100% solids. High Tg. ... 

In the case of meat products such as dried ham, salt plays an important role in the development of flavors as well as in the texture of the product. As a matter of fact, the pH, the concentration of NaCl and the temperature are the factors that most influence proteolysis during ham curing. An ultimate low pH (< 5.7) promotes the release of proteases, whereas a strong concentration in NaCl is an inhibitor for the activity of proteases. As a result, the decrease in NaCl in dry ham not only causes problems of health safety but also texture defects (flabby and doughy) [HAR 14]. 

Sodium nitrite can react with proteins in the stomach or during cooking, especially in high heat (such as frying bacon), to form carcinogenic N-nitrosamines. To prevent this, ascorbic acid or erythor-bic acid is commonly added to cured meats. 

Sodium nitrate has been used for centuries to cure meat. Bacterial action during curing converts the sodium nitrate into sodium nitrite, which kills the bacteria that cause botulism, and combines with the myoglobin in the meat to form the pink color associated with ham. 

A review by Bailey and Swain ( ) cited several references which indicated nitrite was responsible for cured meat flavor. These same authors presented chromatograms of volatiles from cured and uncured hams and while the chromatograms were similar, some quantitative differences led to the conclusion that the major difference due to nitrite was its reactivity to retard lipid oxidation. Greene and Price ( ) suggested, however, that sodium chloride was the major factor responsible for cured meat flavor rather than sodium nitrite or an absence of lipid oxidation. It has been concluded from other recent work (2) that nitrite was necessary to produce a typical ham aroma and flavor as well as to retard the development of off-odors and flavors during storage of cooked cured meat. 

In fact, as will be indicated later in this manuscript, the proteins of meat are the major constituent with which nitrite reacts and explain the largest proportion of the nitrite lost from analytical detection during curing. While considerable discussion has occurred about this so called protein bound nitrite, little has been substantiated about identification and quantitation of the reaction products. Protein bound nitrite has been of concern in analysis for free nitrite because depending on conditions of analysis, some portion of it may be released and measured. 

Cured meat pigment (nitrosyl ferrohemochrome) may be prepared by gaseous NO treatment of hemin (Shahidi etal., 1985). O Boyle etal. (1990) used cured meat pigment produced by this method in the production of nitrite-free weiners, lowering the possibility for nitrosamine formation in these products during heat processing. This process also has not yet been incorporated into commercial practice. 

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