Think pink: Nitrite-free cure

Microbial meat treatment

 

Non-pathogenic microbes found in samples of Chinese dried pork could be used to form nitrosylmyoglobin in preserved meats without the addition of the nitrite preservatives commonly used in bacon products and other meats that have come under fire because of concerns about carcinogenicity. Raman spectroscopy and other techniques were used to demonstrate the formation of the nitrosylmyoglobin and provides critical data on potential safety and viability.

Peijun Li, Baohua Kong, Qian Chen, Dongmei Zheng and Ning Liu of the College of Food Science at the Northeast Agricultural University, in Harbin, Heilongjiang, China, have investigated Staphylococcus xylosus and Pediococcus pentosaceus isolated from Chinese dried sausage. They describe details in a forthcoming issue of the journal Meat Science currently online but due to be published in 2013.

The team brewed up the microbes in Mann-Rogosa-Sharp broth model systems and raw pork meat batters without the addition of nitrite preservative and tested the microbial bio-conversion of metmyoglobin to nitrosylmyoglobin in these mixtures. They used visual inspection as well as photochemical information from UV-Vis, electron spin resonance (EPR) and resonance Raman spectroscopic techniques to assess the degree of conversion. "The results showed that samples in model systems with S. xylosus cultures had an absorption spectra that is typical of nitrosylmyoglobin, an obvious pink colour and a significantly higher a*-value than the control samples or samples inoculated with P. pentosaceus," the team explains. The a*-values (redness) for S. xylosus samples were in fact almost the same as those for samples of meat treated with nitrite. The team suggests that this microbial approach to meat preservation may preclude the need to use nitrites.

Nitrites are widely used in meat processing by the food industry. Adding sodium or potassium nitrite helps to cure meat through the reaction of the nitrite with myoglobin (Mb), this not only generates a characteristic and desirable pink colour in the meat often associated with good quality preserved product but also leads to an enhancement of the flavour. The nitrite reaction also inhibits oxidation of the meat, which would otherwise lead to browning and rancidity. The same preservative crucially blocks the growth of pathogenic bacteria in the meat, including the potentially lethal Clostridium botulinum, which causes botulism.

Unfortunately, despite the benefits of nitrite preservatives the public image of these compounds has been tarnished by data that suggest a putative association with stomach and other forms of cancer. The presence of nitrite having been demonstrated in the laboratory to generate known carcinogens, nitrosamines. These same compounds are also mutagenic and teratogenic. The industry while generally keen to play down the issue and to point to the limited data and the tiny quantities of nitrite used is nevertheless also keen to find alternatives to nitrite preservatives that could be marketed as safer and more natural. Various attempts have been made but little success has been achieved safety notwithstanding but in particular regard to the pink colouration of preserved meats that is almost essential to a saleable product.

Meaty fermentation

The Chinese team point out that other researchers have studied conversion of Mb using Lactobacillus fermentum and other microbes. However, the fact that these microbes were tested on "fermented" meat products meant that the colour change reactions were not necessarily associated with the microbial action and may have been due to other side reactions taking place within the complex matrix of a cured meat. Li and colleagues hoped to separate the meat from the Staph and so determine with specific microbes are responsible for preservative changes.

"Our findings demonstrate a potential solution for colourising cured meat products and producing natural/organic foods without the addition of nitrite/nitrate," the team concludes.