Study On The Yeast Addition During Fermentation Period Of High-salt And Diluted-state Soy Sauce

Soy sauce is originated in China and has a history of more than 2000 years.It is a great contribution of our ancestors to human diet culture and the world brewing industry.In recent years,soy sauce has developed rapidly and the output is large.The annual output of world soy sauce is about 8 million tons,including 5 million tons in mainland China,1.2 million tons in Japan,and2.6 million tons in other Asian countries and regions.It can be seen that China is a major producer and consumer of soy sauce.The brewing technology of soy sauce is unique.At present,the high-salt and diluted-state fermentation process has become the main production mode of high-quality,high-grade soy sauce in China,and it is also the traditional fermentation mode of soy sauce brewing in China.Increasing the utilization rate of raw materials for soy sauce products and improving the flavor will greatly benefit the international competitiveness of domestic soy sauce companies.At present,soy sauce products in China are mainly low-salt and solid-state soy sauce.Most of its fermentation strains are Aspergillus oryzae,which produces soy sauce with poor flavor and low-end products,and lacks competitiveness in the international and domestic markets.With the development of soy sauce industry technology,it has been difficult to produce a soy sauce with a full flavor and a prominent sauce.Therefore,the use of multi-strain mixed fermentation process is the core of modern soy sauce brewing technology.In this paper,the traditional high-salt and thin-state fermentation process is adopted with the sauce koji or sauce mash provided by the enterprise as raw materials.By controlling temperature and natural fermentation,the effect of yeast addition in fermentation of soy sauce mash is discussed.The main research contents and conclusions are as follows:(1)Study on Fermentation Characteristics of Saccharomyces rouxii and Torulopsis globosaStudies of Saccharomyces rouxii and Torulopsis globosa in YEPD medium indicate that:Saccharomyces rouxii and Torulopsis globosa have certain osmotic resistance,and the growth condition is better in the fermentation medium containing 15%NaCl.However,when the amount of NaCl in the medium is 15%,the growth of Saccharomyces rouxii is best when the fermentation temperature is 30?and the inoculum is 8%.Torulopsis globosa grows most vigorously at 30?,when the inoculum is 6%.The optimum pH values of the two yeasts grew well in the range of pH changes during the fermentation of soy sauce.The effects of salt(15%NaCl)and without salt on alcohol and ester production of Saccharomyces rouxii and Torulopsis globosa in the adjusted YEPD liquid medium(5%glucose)were studied:with and without salt have great influence on ethanol production of two yeasts,but have little effect on total esters.Among them,with and without salt,Saccharomyces rouxii produced the highest amount of ethanol earlier than Torulopsis globosa,and the ester-producing ability was significantly weaker than Torulopsis globosa.(2)Study on the Ways of Adding Saccharomyces rouxii and Torulopsis globosa in SauceReference to the production mode of the first high solid salt and thin salt soy sauce(In this process,the Sauce koji:brine=1:1 mixed into solid mash,then adding 1.7 times of salt water for30 days of fermentation for more than 6 months of dilute fermentation),the adding mode of yeast is studied at the laboratory level.The optimum adding time of Saccharomyces rouxii is the 30th day of fermentation,and the optimum adding amount was 2*10~6/g(sauce mash).Adding agent or bacterial liquid of Saccharomyces rouxii into sauce mash has little effect on the results.The optimum addition time of Torulopsis globosa is 60th day of fermentation,and the optimum addition amount is 2*10~6/g(sauce mash).(3)Study on Yeast Addition in Different Fermentation Methods of High-salt and diluted-state soy sauceDuring the 6-month fermentation cycle,the fermentation methods of high-salt and diluted-state soy sauce with different ratio of material to water(the Sauce koji:brine=1:1+1.7,1:2.25,1:2.7)under constant temperature,variable temperature and sunshine and night exposure were studied,changes in the main physical and chemical indicators of each sauce when adding different yeasts.SPME-GC-MS was used to detect the volatile aroma components of typical samples,and the effect of adding yeast to different salty soy sauces is discussed.The results show:(1)The ratio of material to water of JY2.25(1:2.25)is within the range of feed water ratio of industrial high-salt dilute soy sauce fermentation(1:2~2.5),and the fermentation result is best.Secondly,JY2.7 is better than JY1+1.7 in adding brine twice.However,the effect of prolonging the time of sunshine fermentation remains to be further studied.(2)By comparing the difference in the main physical and chemical indexes before and after the fermentation of soy sauce,the effect of soy sauce fermentation mode on the quality of the finished product is greater than the addition of yeast.(3)The flavor of typical soy sauce samples was detected by SPME-GC-MS,the results show:Within 180 days of the fermentation cycle,the temperature-controlled fermented soy sauce has more scent of aroma and alcohol,and the content of acetic acid and acetate in the sun-fermented fermentation is significantly higher than that of temperature-controlled fermentation.But,there is no significant difference in the indicators of phenols,ketones,furans and furanones between sun-fermented and temperature-controlled fermentation.At the same time,the color of the temperature-controlled fermentation sample is deeper.During soy sauce fermentation,the effect of fermentation method on the flavor of soy sauce was greater than that of yeast.There is no significant difference in the types of aroma substances between different fermentation methods,but the content is significantly different.(4)Changes in the number of Saccharomyces rouxii and Torulopsis globosa during the fermentation of High-salt and diluted-state soy sauceFor some samples of companies and laboratories,real-time quantitative PCR is used to track and detect the effect of yeast addition in high-salt and diluted-state soy sauce on the amount of yeast in the fermentation process of soy sauce under different fermentation modes.The study found that during a certain fermentation time,the addition of yeast will strengthen the yeast in the sample,thereby increasing the amount of yeast;as the fermentation time prolonged,the number of yeasts decreased,regardless of the difference in the previous period,and the fermentation was maintained in a certain amount range in the middle and late stages of fermentation.Under different fermentation methods,there are a certain number of Saccharomyces rouxii and Torulopsis globosa in the blank samples,and the specific reasons need to be further compared.