The typical cured-meat color is associated with the formation of nitrosomyoglobin, which results from a series of reactions involving the formation of nitrogen oxide (NO) and its reaction with myoglobin producing nitrosylated pigments, which yield a red color (61).
In the Mediterranean process, the substrate added to produce NO is mainly nitrate, whereas in the northern process, nitrite is added as coloring salt. Use of nitrate involves bacterial reduction to nitrite. It is carried out by coccal gram-positive bacteria but their nitrate reductases are inhibited by pH below 5.2 (62) (Table 5). Nitrite acts as a very
Table 5 Action of Starter Cultures in Dry Sausage
Mode of action
Condition of surface pH drop
Nitrate reduction Bacteriocin Amines degradation Prevention of mycotoxin Nitrate reduction pH drop
H2O2 breakdown pH drop Acid production Protein breakdown Fat breakdown Antioxidant properties Amino acid catabolism Fatty acid catabolism Apperance Protection from drying out Protection from O2 and light
: very important;
: important; +: noticeable effect; ( + ): weak effect; — : no effect
reactive oxidant and is reduced to NO immediately after preparation of the sausage mix. The reduction of nitrite to NO is favored by the acidification caused by lactic acid bacteria (Table 5). Color, tone, and intensity of products vary perceptibly according to whether they are cured with nitrite or nitrate (63).
Discoloration of cured meat can be observed by the formation of peroxide. This default can be avoided by the catalase activity of coccal gram-positive bacteria that protect the color (64) (Table 5).
During comminution, addition of salt solubilizes muscle proteins, which coagulate and form a gel surrounding lard and meat particles because of the acidification brought about by lactic acid bacteria (Table 5). The pH required for coagulation increases with increasing salt concentration and is 5.3 at the often-used salt concentration of 3% (7). Coagulation by acidification is associated with the release of water at the isoelectric point of the meat proteins (pH 5.3). The gel formed by coagulation is further stabilized by the release of water, and it forms a matrix surrounding fat and meat particles, which determine sausage texture. The drop in pH affects texture development during fermentation, whereas further texture development during drying is only affected by the loss of water. Numerous factors affect the interrelated rates of both acidification and drying. Lactic acid bacteria are known to increase the rates of acidification and drying and thus of texture development (65). Increasing sausage diameter clearly decreases the rate of drying and thus the rate of hardness development (66).
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