Screening,Characterization And Application Of Lactic Acid Bacteria In Characteristic Natural Fermented Jiangshui

Traditional fermented food has a long history and wide coverage in China.Among them,Sichuan sauerkraut uses vegetables as the main raw material,and adopts the method of soaking stains,only the sauerkraut is eaten.Guangxi acid porridge and Guizhou acid soup use glutinous rice and rice water as fermentation raw materials respectively,while Jiangshui is fermented with vegetables and noodle soup.People use pulp to make noodles,soups,and blended drinks,which are common in Gansu and Shanxi.Jiangshui contains vitamins,organic acids,amino acids and other nutrients.The flavor of Jiangshui is very unique and it has the functions of strengthening stomach and digestion,clearing and relieving heat.So,it is loved by the masses.However,the current production of Jiangshui is mostly the traditional natural fermentation of family workshops,which is susceptible to the environment and the seasons,resulting in excessive nitrite content and deterioration of product quality.This research took traditional natural fermentation Jiangshui from Tianshui and Baiyin in Gansu as the research object,selected strains suitable for Jiangshui fermentation,prepared Jiangshui by pure strain fermentation,and used Jiangshui to make fermented beverage,aiming to improve the quality of traditional Jiangshui,control the nitrite content,and promote the modern production of Jiangshui and it's derivatives.The main research contents and related conclusions are as follows:Firstly,three strains of lactic acid bacteria were screened from Jiangshui,of which 2strains were identified as Lactobacillus fermentum and the other one was Lactobacillus plantarum.All three lactic acid bacteria have the ability to degrade nitrite.The degradation rate of nitrite after fermentation of Lactobacillus fermentum SJ-1 in liquid medium containing150 mg/L of nitrite at 35°C for 24 h is about 90%.The lactic acid bacteria were used to inoculate and ferment Jiangshui to prepare lactic acid bacteria fermentation Jiangshui,and the fermented strain and the grain flour raw material were screened.The changes of nitrite content,number of lactic acid bacteria colonies,pH value and total acid content,organic acids and volatile components were examined.The results showed that the fermentation of Lactobacillus fermentum SJ-1 was the best in lactic acid fermentation Jiangshui,the ability to produce acid,the ability to degrade nitrite was the strongest,and the sensory quality was good.After lactic acid bacteria fermentation,the peak of nitrite content decreased significantly.The nitrite content in the SJ-1 fermented samples was lower than that in the other experimental groups,and no significant nitrite content peake was detected;The total content of organic acids increased significantly after fermentation(p<0.05),and the content of lactic acid,acetic acid,formic acid and malic acid changed significantly.Compared with other experimental groups,the total amount of organic acid in the Jiangshui obtained by fermentation of Lactobacillus fermentum SJ-1 was higher.Compared with the initial stage of fermentation,the esters,aldehydes and ketones,acids and alcohols in the samples increased to varying degrees.The samples obtained by SJ-1 fermentation were rich in aldehydes and ketones,and the aroma components such as aromatic hydrocarbons and anthraquinones were higher than other experimental groups,with the best flavor and the highest sensory score.Compared with the Jiangshui made from other cereal flours,the samples made by wheat flour had a higher content of lactic acid bacteria,better sensory quality and lower nitrite content.Secondly,the culture conditions of the preferably obtained Lactobacillus fermentum were studied in order to determine suitable culture conditions to lay a foundation for the preparation and industrial production of the lactic acid bacteria fermentation Jiangshui and Jiangshui derived product.Studies have shown that the highest concentration of bacteria was obtained when added 8.21%of glucose,2.04%of soy peptone,0.42%of dipotassium hydrogen phosphate to the culture solution of Lactobacillus fermentum SJ-1,and adjusted the initial pH of the culture solution to 6.0,and culture at 35°C for 24 h.The concentration of the bacterial liquid detected at this time was 2.7×10~9 CFU/mL.And at this time,the biological activity of the lactic acid bacteria is high,and the fermentation liquid used in this stage is most effective for producing Jiangshui.Thirdly,the processing technology of artificial inoculation of fermented Jiangshui was studied.The results showed that celery could have better color protection effect,reduced the loss of nutrients and achieved passivation of peroxidase in celery when it was blanched at100°C for 60 s.When Added 12%of celery,2.5%of wheat flour,and inoculated 5%of lactic acid bacteria culture solution,Jiangshui obtained by fermenting in 35°C for 24 h was good in sensory quality.When celery juice and noodle soup mix 1:1,and added 5.0%white granulated sugar and inoculated 5.0%lactic acid bacteria,the Jiangshui beverage was good in sensory quality,and the lactobacillus content in the Jiangshui beverage continued to decrease under the condition of 0°C and 4°C during the cold storage,but the Jiangshui beverage was still contained with viable cells of 10~7~10~8 CFU/mL after 20 d of cold storage.Compared with4°C,0°C cold storage Jiangshui beverage's quality was more stable.In this research,Lactobacillus fermentum with good growth vigor,strong acid production ability and obvious nitrite degradation was isolated from natural fermentation Jiangshui and used for artificial inoculation fermentation of Jiangshui and preparation of lactic acid fermentation Jiangshui beverage.Compared with the natural fermentation Jiangshui,the obtained lactic acid fermentation Jiangshui is effectively controlled,the fermentation time is shortened,and the sensory quality is improved.Therefore,the Lactobacillus fermentum isolated in this research can be used for pure fermentation of Jiangshui,thereby shortening the fermentation cycle,improving the sensory quality,and controlling the nitrite content of Jiangshui.This study has certain reference value for the modern industrial production of Jiangshui.