Selection of yeast strains in naturally fermented cured meat as promising starter cultures for fermented cured beef, a traditional fermented meat product of northern China.

BACKGROUND: Fermented meat products are meat products with a unique flavor, color, and texture as well as an extended shelf life under natural or artificially controlled conditions. Microorganisms or enzymes are used to ferment the raw meat so that it undergoes a series of biochemical and physical changes. Common fermentation strains are lactic acid bacteria, yeasts, staphylococci, molds, and so forth. Studies on the inhibitory effect of yeast fermentation strain on N-nitrosamines in fermented meat products have not been reported. Two excellent yeast starters were identified to solve the problem of nitrosamines in fermented meat products. RESULTS: Meyerozyma guilliermondii and Debaryomyces hansenii led to weak acid production, strong resistance to NaCl and NaNO2 , and high tolerance to low acidic conditions. The inoculated fermented beef exhibited decreased lightness, moisture content, water activity, pH, protein content, nitrite content, and N-nitrosamine content in comparison with the control group fermented bacon. M. guilliermondii had a better effect, reducing pH from 5.69 to 5.41, protein content from 254.24 to 221.92 g·kg-1 , nitrite content from 28.61 to 25.33 mg·kg-1 and N-nitrosamine by 18.97%, and giving the fermented beef the desired meat color, mouthfeel, odor, taste, and tissue quality. CONCLUSION: In this study, two strains of yeast fermenters that can degrade N-nitrosamine precursors were identified, which to some extent solves the problem of the high risk of generating nitrosamines such as N-nitrosodiethylamine (NDEA) by processing fermented meat products with nitrites as precursors. These two strains are likely to be used as starter cultures for fermented meat products. © 2023 Society of Chemical Industry.

The nitrosamine contamination of drugs, part 3: Quantification of 4-Methyl-1-nitrosopiperazine in rifampicin capsules by LC-MS/HRMS.

Upon emergence of nitrosamines in various drugs, e.g in valsartan, metformin and ranitidine, 4-methyl-1-nitrosopiperazine (MeNP) was found in rifampicin in August 2020. Rifampicin is used, amongst others, for post-exposure prophylaxis of leprosy. The occurrence of MeNP can be explained by the synthesis, because 1-amino-4-methylpiperazine is concomitantly used with the organic oxidizing reagent isoamyl nitrite. According to a method reported by the FDA, the quantification of MeNP in rifampicin capsules was performed by LC-MS/HRMS. A significant contamination with MeNP was found in all samples, ranging from 0.7 to 5.1 ppm and exceeding the acceptable intake limit proposed by the FDA up to 32-fold. However, the severity of a possible leprosy infection outweighs the risks, which are concomitant with the intake of a single dose of rifampicin for post-exposure prophylaxis. Nevertheless, the extent of contamination is alarming, and countermeasures are needed to minimize public health risks. The presence of nitrosamines in rifampicin illustrates the need for better strategies in impurity profiling and compendial testing once again.

Nitrite metabolism in Debaryomyces hansenii TOB-Y7, a yeast strain involved in tobacco fermentation.

The Italian cigar manufacturing process includes a fermentation step that leads to accumulation of nitrite and tobacco-specific nitrosamines (TSNA), undesirable by-products due to their negative impact on health. In this study, growth and biochemical properties of Debaryomyces hansenii TOB-Y7, a yeast strain that predominates during the early phase of fermentation, have been investigated. With respect to other D. hansenii collection strains (Y7426, J26, and CBS 1796), TOB-Y7 was characterized by the ability to tolerate very high nitrite levels and to utilize nitrite, but not nitrate, as a sole nitrogen source in a chemically defined medium, a property that was enhanced in microaerophilic environment. The ability to assimilate nitrite was associated to the presence of YNI1, the gene encoding the assimilatory NAD(P)H:nitrite reductase (NiR), absent in Y7426, J26, and CBS 1796 by Southern blot data. YNI1 from TOB-Y7 was entirely sequenced, and its expression was analyzed in different media by Northern blot and reverse transcriptase polymerase chain reaction. The evidence that, in D. hansenii TOB-Y7, YNI1 was transcriptional active also in the presence of high ammonia concentration typical of tobacco fermentation, stimulated the development of an improved process that, on a laboratory scale, was proved to be effective in minimizing nitrite and TSNA accumulation.