Study On The Influencing Factors Of Drinking Cheese Flavor Yogurt

With its high nutritional value,cheese is known as "milk gold".The price of imported cheese products on the Chinese market is expensive,limiting the consumption of cheese,is not conducive to the development of cheese.In the fact of taste,the cheese is mainly satisfied with the taste of foreign people preferences,the strong flavor of its thick and stimulated is difficult to adapt to the needs of Chinese customer's flavor;and yogurt as the most important fermented dairy products of our country,with predominant health care function,delicate taste,soft flavor,sweet and sour taste,and other characteristics,consumers are increasingly inclined to choose yogurt as a daily drink.In this paper,Lactococcus lactis subsp.Lactis and Lactococcus lactis subsp.Cremoris were used as cheese-flavor fermentation bacteria,which were fermented with Lactobacillus.bulgaricus and Streptococcus thermophilus at the later stage of fermentation,explored and invented a kind of drinking cheese flavor yogurt.The effects of various factors on the flavor of yogurt during the fermentation process were studied,which provided scientific basis for the production of yogurt with characteristic flavor.The experiment consists mainly of the following components:The first part of the paper,the determination of fermentation characteristics of Lactococcus lactis.The main research on the changing tendency of viable cell number,acidity,viscosity and diacetyl with time during the process of Lactococcus lactis subsp.Lactis and Lactococcus lactis subsp.Cremoris single strain fermentation and two strains mixed fermentation,evaluated the quality by sensory when the fermentation finished,and analyzed the volatile flavor substances while Lactococcus lactis subsp.Lactis and Lactococcus lactis subsp.Cremoris single strain fermentation.The results showed: compared with Lactococcus lactis subsp.Cremoris,Lactococcus lactis subsp.Lactis have more vigorous growth vitality,more excellent capacity of product acid,viscosity and diacetyl,but the fermentation time of Lactococcus lactis subsp.Lactis was far shorter than Lactococcus lactis subsp.Cremoris,while fermentation was finished,viscosity and content of diacetyl were lower than Lactococcus lactis subsp.Cremoris;the sensory score was lowest when the Lactococcus lactis subsp.Lactis single strain fermentation,Lactococcus lactis subsp.Cremoris single strain fermentation got higher score on taste and smell,the highest sensory score was 93 points when Lactococcus lactis subsp.Lactis and Lactococcus lactis subsp.Cremoris were fermented at a ratio of 1: 1;15 kinds of volatile flavor substances were detected in the fermentation product of Lactococcus lactis subsp.Lactis,among them,there were 3 kinds of esters,4 kinds of ketones,6 kinds of aldehydes and 2 kinds of alcohols;18 kinds of volatile flavor substances were detected in the fermentation product of Lactococcus lactis subsp.Cremoris,among them,there were 5 kinds of esters,4 kinds of ketones,4 kinds of aldehydes and 4 kinds of alcohols,and 1 kind of acids.Through analysing,there were 7 kinds same flavor substances in the two strain: acetaldehyde,isobutyraldehyde,2,3-butanedione,2-methyl butyraldehyde,2-pentanone,3-hydroxy-2-Butanone,isoamyl alcohol.Everything considered,selected Lactococcus lactis subsp.Lactis and Lactococcus lactis subsp.Cremoris at a ratio of 1: 1 as the best ratio of cheese flavor fermentation,at this ratio,showed the highest sensory score,the strongest capacity of product diacetyl,the moderate capacity of product acid and viscosity,12 hours acidity reached 70.63°T,the viable cell number of lactic acid bacteria reached 73.5×106cfu/g,viscosity reached 3950 mPa.s,content of diacetyl could be up to 19.62mg/L,sensory score was 93 points.The second part of the paper,discussion on the process conditions.Through analyzed the volatile flavor substances while segmented fermentation and mixed fermentation,determined the changing tendency viable cell number,acidity,viscosity and diacetyl with time,and evaluated the quality by sensory to determined the best fermentation method.The results showed: 24 kinds of volatile flavor substances were detected in the fermentation product of mixed fermentation,among them,there were 8 kinds of esters,4 kinds of aldehydes,5 kinds of ketones,2 kinds of alcohols,2 kinds of acids,3 kinds other chemical compound;when pre-fermentation time was 3 hours,26 kinds of volatile flavor substances detected,among them,there were 5 kinds of esters,6 kinds of aldehydes,7 kinds of ketones,2 kinds of acids,3 kinds of alcohols and 3 kinds other chemical compound;when pre-fermentation time was 6 hours,21 kinds of volatile flavor substances detected,among them,there were 7 kinds of esters,4 kinds of aldehydes,5 kinds of ketones,1 kinds of alcohols,2 kinds of acids and 2 kinds other chemical compound;when pre-fermentation time was 9 hours,21 kinds of volatile flavor substances detected,among them,there were 9 kinds of esters,4 kinds of aldehydes,4 kinds of ketones,2 kinds of alcohols and 2 kinds other chemical compound.When pre-fermentation time was 3 hours,showed the vintage growth trend of viable cell number,viscosity and diacetyl,the capacity of product acid was strong,the volatile flavor substances were detected in the fermentation product was the most,the sensory score was the highest,thus,determined pre-fermentation time 3 hours as the best fermentation method.When pre-fermentation time was 3 hours,9 hours acidity reached 71.05°T,the viable cell number of lactic acid bacteria reached 112.2×106cfu/g,viscosity reached 4250 mPa.s,content of diacetyl could be up to 21.02mg/L,sensory score was 93 points.The third part of the paper,optimized the fermentation process and the quality variability of yogurt during the storage period.On the basis of the second part,researched the effects of sugar content,pre-fermentation temperature,addition of cheese starter(Lactococcus lactis subsp.Lactis,Lactococcus lactis subsp.Cremori),post-fermentation temperature,addition of yogurt starter(Lactobacillus.bulgaricus,Streptococcus thermophilus)and other factors on the sensory evaluation of yogurt,and through orthogonal test to get the best fermentation conditions.In addition,stored the yogurt product in a low temperature environment of 4 ?,and determined viable cell number,acidity,viscosity and diacetyl content periodically.The results showed: through single factor test,chosen addition of cheese starter,pre-fermentation temperature,addition of yogurt starter and post-fermentation temperature as the infiuencing factors,researched their effects on the quality of yogurt.On the basis of single factor test,the optimal fermentation conditions were determined by L9(34)orthogonal test: addition of cheese starter was 4%,pre-fermentation temperature was 33 ?,addition of yogurt starter was 3%,post-fermentation temperature was 37 ?.Under this condition,the sensory score of the fermented yogurt was 96 points,which was higher than the highest score in the orthogonal test.The changes of every index within the 20 days of storage period were as follows: at the 8 days forward,viable cell number,acidity,viscosity,diacetyl content and sensory score behaved good quality of yogurt;after 8 days,viable cell number reduced drastically,the acidity increased to above 85°T,the viscosity growth rate accelerated,whey separated gradually,diacetyl content decreased gradually,sensory score decreased slowly at the first,then decreased drastically,was not conducive to drinking.