| Pickle is one of the oldest traditional fermented foods in China, Chinese made pickledvegetables as early as more than3000years ago. To date, the production of the pickle ismostly based on spontaneous fermentation used fresh vegetables after segmentation with salt,sugar and spices. Various vegetables, such as Chinese cabbage, cabbage, radish, asparagus,cucumber and so on were pretreated and immersed in6-8%(w/v) salt solution and then left atambient temperature (20-25℃) for6-10days in pickle jar to undergo lactic acid fermentation.Pickle is rich sources of minerals and is easy for the body to process after thefermentation of lactic acid bacteria. However, the accumulation of nitrite is a commonproblem during vegetables fermentation. The nitrite can react with amines and amides toproduce N-nitroso compound, these have been related with cancers. For these reasons, thescavenging of nitrite in pickle has received increasing attention. However, to the best of ourknowledge, there appear to be limited investigations focusing on the mechanism of nitritedegradation. The objective of this study is to evaluate the correlation between the changes oforganic acids and the degradation of nitrite during pickle fermentation, and verify the effect oforganic acids on nitrite decomposing. The main research results are as following.(1) A method using high performance liquid chromatography was developed todetermine organic acids composition (oxalic, tartaric, malic, lactic, citric, succinic andpropionic acids) in pickles fermentation.Using Chinese cabbage as raw materials for pickles,nitrite content rose over time to reach a peak value, and then declined during the fermentationprocess of pickles, the nitrite content achieved the maximum at the5th day. The pH of brinehas declined until the pH was3.9. The level of oxalic, tartaric, citric, succinic and propionicacids decreased during fermentation, the content of malic and lactic acids changed undulately.The content of tartaric, succinic and propionic acids showed a significant positive correlationwith nitrite content, the correlation coefficient were0.96,0.96,0.95, a high correlation couldalso be found between the content of oxalic acid and nitrite content, however, a weakerrelationship could be found in lactic and citric acids.(2) The nitrite scavenging experiment in vitro. Batch tests were conducted to investigatenitrite reduction in the presence of organic acids based on the content of nitrite and organicacids in pickle. The results showed that the nitrite could be effectively reduced by oxalic,tartaric, malic, lactic, citric, succinic and propionic acids, the reduction efficiency of nitritedecreased quickly with increasing initial pH value, increased considerably with increasingtemperature and did not vary much at the nitrite concentration of50μg/mL when the excessive amount of organic acids from3to5μmol/mL in12h except for lactic andpropionic acid. The ability of nitrite reduction by organic acids were oxalic acid> citric acid>tartaric acid> malic acid> succinic acid> lactic acid> propionic acid, the nitrite degradationrate increased with the increase of the initial concentration of nitrite and was consistency withthe disappearance of the nitrite peak.(3) The nitric oxide was the product during the process of the reduction of nitrites, thecontent of nitric oxide increased with increasing nitrite concentration, the largest content was95ppm at the nitrite concentration of50μg/mL which added citric acid (250μmol); the nitriteconsumption by citric acid was the most, lactic acid was the least, the more consumption ofnitrite the more production of NO.(4) The content of nitrite reduced significantly by adding organic acids during thefermentation of the pickle, and it was lower in the pH=3of broth than that pH of4; thecontent of nitrite were significantly lower than other samples which adding succinic andpropionic acids and this confirmed that there were correlations between the nitrite reductionand succinic and propionic acids. |
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