Changes in the colour and opacity of meat

Botulism control by nitrite and sorbate in cured meats: A review

Evidence that ingested nitrate and nitrite are beneficial to health.

Historically, nitrite has been a component of meat-curing additives for several centuries. In recent years the safety of nitrite as an additive in cured meats has been questioned mainly because of the possible formation of carcinogenic nitrosamines. Nitrite has many important functions in meat curing including its role in color development, flavor, antioxidant properties, and antimicrobial activity. The inhibition of Clostridium botulinum growth and toxin production is an especially important antimicrobial property of nitrite. This review discusses the effects of processing, curing ingredients (especially nitrite), and storage of cured meats in relation to the control of C. botulinum. If nitrite is eliminated from cured meats or the level of usage decreased, then alternatives for the antibotulinal function of nitrite need to be considered. Several potential alternatives including sorbates, parabens, and biological acidulants are discussed.

Nitrite, nitrite alternatives, and the control of clostridium botulinum in cured meats

Meat color is the primary criterion by which consumers evaluate meat quality and acceptability. Consumers prefer bright-red fresh meats, brown or gray-colored cooked meats and pink cured meats. Any deviations may result in reduced sales, consumer complaints and returned products. The relatively short shelf-life of fresh meats is the single greatest concern to retail meat markets. When brown metmyoglobin reaches 30–40% of total pigments on the surface of fresh retail beef, consumers make a nopurchase decision (Greene et al., 1971). It is estimated that 4–10% of retail meats are either discounted, processed into hamburger, or even discarded due to brown-color development. Efforts continue to extend fresh meat color stability through improved sanitation and antimicrobial treatments, temperature control, packaging, and also through diet modification and improved breeding and handling of live animals.

Color — its basis and importance

1 5 N-labelled nitrite was used to determine the amount of nitric oxide bound to unheated compared to heated myoglobin. Heated samples contained twice the amount of 15N as unheated samples. The globin portion was likely detached from the myoglobin by heating, and two sites for binding of nitric oxide were therefore made available.

Nitrite binding sites on myoglobin

When a cured meat model system was made from white muscle it contained less residual nitrite than if it were made from a red muscle; this effect is due to the lower pH of white muscle. If the pH of red and white muscle is similar then the slightly lower residual nitrite in products made from red muscle probably is due to the greater content of myoglobin in red muscle.

Effect of muscle type on residual nitrite in cured meat

Experiments were designed to determine the effect of the chemical state of myoglobin and presence of ascorbate on the conversion of nitrite to nitrate. In model systems, nitrate was not formed when nitrite was incubated in the presence of either metmyoglobin or ascorbate. However, most of the added nitrite was converted to nitrate when both ascorbate and metmyoglobin were present. It is suggested that ascorbate reduces metmyoglobin to myoglobin, and then, the myoglobin is oxidized simultaneously with nitrite to form nitrate. In cured meat products, a detectable level of nitrate was formed in the absence of ascorbate, but in the presence of ascorbate the level of nitrate formed was greater. The explanation suggested was that endogenous reductants in meat could play the same role as ascorbate in model systems. Such endogenous reductants were responsible for more than half of the nitrate formation in meat products containing sodium ascorbate.

Factors affecting the formation of nitrate from added nitrite in model systems and cured meat products

Ground pork trim was formulated with various levels of nitrite and one of two NaCl concentrations, canned and heated at 90, 100 or 110°C. Cured meats were similarly prepared with meat whose sulfhydryls had been reacted with silver ions. Antibotulinum activity in these cured products was tested by inoculating Clostridium botulinum spores directly into canned meats (96 spores/150g) or into homogenates (1:1, w/v) adjusted to 30 ppm NaNO2 (48 spores/16.5 ml). Antibotulinum activity was detected by both challenges. It was greater in meats cured with higher nitrite concentrations, was lower if processing was at high temperature (110 vs 90° C) and decreased during storage of the cured meats. Inhibitory activity was found in cured products made of silver-treated meats.

S. H. Lee

Papers

Nitrite binding sites on myoglobin

Effect of muscle type on residual nitrite in cured meat

Factors affecting the formation of nitrate from added nitrite in model systems and cured meat products

FACTORS AFFECTING INHIBITION OF Clostridium botulinum IN CURED MEATS