Color Formation

The color of meat is directly related to the content of myoglobin, and the meat will thus appear more red at high myoglobin levels. Myoglobin is unstable and reacts easily with oxygen either under formation of the cherry red, and also unstable, oxymyoglobin or under formation of the stable, but brown, metmyoglobin. The red color in dry-cured meat products comes from the pigment nitrosylmyoglobin, which is formed in reactions between nitric oxide and myoglobin or metmyoglobin. The main nitric oxide source is the very reactive nitrite. Quantitatively, the reaction of nitrite with ascorbate is the most important with respect to formation of nitric oxide (8). Ascorbate or erythorbate (isoascorbate) is for this reason a typical ingredient in dry-cured sausage recipes. Nitric oxide is also formed via nitrous acid, the conjugated acid of nitrite, with a pKa of 3.22. Nitrous acid is unstable and dissociates into nitric oxide and nitrate. The more acidic the environment becomes, a condition promoted by the activity of lactic acid bacteria, the more the equilibrium is shifted in direction of nitric oxide and nitrate.

Nitrite is the most common curing agent and is added as nitrite salt, in the form of sodium chloride containing 0.4 to 0.5% sodium nitrite (9). Although 30 to 50 ppm nitrite is enough for proper color formation (9), EU regulation instructs addition of 150 ppm sodium nitrite and permits 50 ppm sodium nitrite in ready-to-sale dry-cured fermented meat products (10). However, nitrate can be added instead of nitrite. The corresponding values for nitrate are 300 ppm and 250 ppm sodium nitrate, respectively. U.S. regulation instructs 150 ppm sodium nitrite and 1700 ppm sodium nitrate and permits a maximum level of200 ppm sodium nitrite in the finished product (11).

Nitrate has no curing capability (9), and microbial reduction to nitrite is necessary to obtain curing effect. The reaction requires the nonendogenous enzyme nitrate reductase. The enzyme is produced by Staphylococcus /Kocuria, but even when nitrite is the only curing agent, Staphylococcus /Kocuria is reported to accelerate color formation (12). The reactions behind this formation are not known. It is hypothesized that because Staphylococcus /Kocuria utilizes nitrate as terminal electron acceptor for growth under anaerobic conditions, the reaction equilibria are shifted toward right, whereby the necessary nitric oxide for color formation is formed more rapidly.

Sleeping Sanctuary

Sleeping Sanctuary

Salvation For The Sleep Deprived The Ultimate Guide To Sleeping, Napping, Resting And  Restoring Your Energy. Of the many things that we do just instinctively and do not give much  of a thought to, sleep is probably the most prominent one. Most of us sleep only because we have to. We sleep because we cannot stay awake all 24 hours in the day.

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