Analysis And Development Of Direct Vat Set Lactobacillus Hilgardii Q19 Malolacticacid Fermentation Starter And Its Brewing Characteristics

Most wine regions are located in the north China,and the grapes are usually high in sugar and low in acid.Therefore,after alcohol fermentation,with high alcohol content and high pH value in wine,the MLF environment is usually harsh.And with the influence of global warming,this trend is intensifying.In addition,the air temperature usually drop sharply during the malolactic fermentation(MLF)in north China.In some wine production enterprises with poor temperature control conditions,the low temperature tolerance of fermentation strains is also very important.In this study,a strain of Lactobacillus hilgardii Q19,which is resistant to high alcohol content and low temperature,was screened from the natural MLF process of Cabernet Sauvignon wine from Qingtongxia production area at the eastern foot of Helan Mountain in Ningxia.After high-density cultivation,the direct vat set is prepared by vacuum freeze-drying.And carry out the MLF pilot test under high alcohol content and low temperature conditions,measure and analyze the change of bacterial density before and after inoculation and fermentation,Changes in L-malic acid,changes in basic physical and chemical indicators before and after MLF fermentation,changes in volatile aroma components,and biogenic amines produced by fermentation,etc.In order to comprehensively evaluate the fermentation performance of directthrowing L.hilgardii Q19 starter in actual production.In order to provide theoretical basis and technical support for the popularization and application of L.hilgardii Q19 starter,It also provides a reference for the development of other strains of lactic acid bacteria starter.The main findings are as follows:1.The lyoprotectant formula of L.hilgardii Q19 was determined to be 8.5 g/100 mL of skim milk powder,14.5 g/100 mL of yeast extract,6.0 g/100 mL of sodium L-glutamate,Under this condition,The lyophilized survival rate was(87.85±1.19)%,And the viable count of the lyophilized powder was(4.36±0.34)×1011 CFU/g,Which could maintain good activity when stored at-20℃.2.In the MLF pilot test of Cabernet Franc&Yan 73 blended wine inoculated with L.hilgardii Q19 direct-throwing starter:Compared with Oeno1,The wine samples inoculated with Q19 had stronger acid-reducing ability,Produced more volatile substances,Produced less biogenic amines,And could reduce the content of histamine in wine samples.3.The MLF pilot experiment inoculated with L.hilgardii Q19 starter showed that it could degrade L-malic acid well under both high alcohol content and low temperature conditions,and the total acid content decreased and the volatile acid did not increase significantly after fermentation.The content of terpenes in wine has increased,and the content of geranyl acetone and squalene has increased significantly,Which increases the special aroma of flowers and fruits in wine,And less biogenic amines are produced.The above research results show that the direct-injection L.hilgardii Q19 starter can be well adapted to the MLF environment of the wine at the eastern foot of Helan Mountain in Ningxia.It can start and complete MLF normally and have a positive impact on the aroma of wine.At the same time,the content of biogenic amines produced is low,And it can be gradually popularized and applied in northern wine-producing areas of my country.