Study On Optimization Of Production Process Conditions Of Manchu Sour Tea

As a traditional grain fermented food of Manchu people,Manchu sour tea has good nutrition and function,as well as local characteristics and national characteristics.The traditional production process of Manchu sour tea relies mainly on the natural fermentation of cereal raw materials and microorganisms in the environment.The type of microorganisms in Manchu sour tea is unclear and the process control is difficult.It is difficult to achieve industrial production.The experiment analyzes the microbial diversity in the fermentation process of Manchu sour tea traditional production process,and provides a theoretical reference for the fermentation of lactic acid bacteria fermentation.The liquefaction and saccharification of the raw materials before fermentation of Manchu sour tea is completed by enzymatic hydrolysis.Screen out the suitable lactic acid bacteria for fermentation of Manchu sour tea and compounding.Using ultra-high pressure technology for passivation after fermentation to explore the effects of ultra-high pressure conditions on the quality and flavor of Manchu sour tea.The intention is to optimize the traditional production process of Manchu sour tea to achieve industrial production.The main conclusions are as follows:(1)In the fermentation process of the traditional production process,the microbial abundance in Manchu sour tea gradually decreased with the fermentation time extend.The content of acidogenic microorganisms such as Clostridium,Lactobacillus,and Lactobacillus plantarum increased with the prolongation of fermentation time.However,the content of Cyanobacteria decreased,and the content of some Enterobacteriaceae increased first and then decreased with the prolongation of fermentation time.(2)Using Amylase LT for liqueafaction of raw materials before fermentaion.On the basis of single factor experiments and response surface experiments,the main influencing factors affecting the dextrose equivalent can be obtained and they were liquefaction time,p H,Amylase LT amount and liquefaction temperature.The liquefaction technology of Manchu sour tea before fermentation was optimized by response surface methodology and the results showed the optimized condition of liquefaction were 6 U/g Amylase LT,33 min,72 ?,p H 6.5.Under the conditions,the DE value reached 21.32%.(3)On the basis of the best liquefaction process conditions,using Diazyme P25 for saccharification of raw materials before fermentaion.On the basis of single factor experiments and response surface experiments,the main influencing factors affecting the dextrose equivalent can be obtained and they were Diazyme P25 amount,saccharification time,p H and saccharification temperature.The saccharification technology of Manchu sour tea before fermentation was optimized by response surface methodology and the results showed the optimized condition of liquefaction were 140 U/g Diazyme P25,5 h,56 ?,p H 4.6.Under the conditions,the DE value reached 51.92%.(4)Through the research on the growth characteristics of Lactobacillus casei,Lactobacillus reuteri,Lactobacillus plantarum,Lactobacillus acidophilus and Lactobacillus rhamnosus,the growth of the five strains showed an upward trend.The growth rate of Lactobacillus plantarum and Lactobacillus casei was faster,and the growth rate of Lactobacillus rhamnosus was slower.Lactobacillus plantarum had the fastest acid production rate,followed by Lactobacillus casei and Lactobacillus rhamnosus.When the p H decreased to 3.0,the bacterial count of Lactobacillus casei was 4.0×106 CFU/m L,Lactobacillus plantarum was 3.0×106 CFU/m L,and Lactobacillus rhamnosus was 2.1×106 CFU/m L.The bacterial count of Lactobacillus reuteri and Lactobacillus acidophilus were 4.1×105 CFU/m L and 2.1×105 CFU/m L.None of the five lactic acid bacteria have the ability to break down proteins and fats.When the bile salt concentration increased to 1.0%,the bacterial count of Lactobacillus reuteri and Lactobacillus plantarum decreased to 1.2×103 CFU/m L and 1.1×10 4 CFU/m L,however the other lactic acid bacteria no longer grow and have no ability to resist bile salts.(5)Through the research of fermentation characteristics such as p H,titration acidity,free amino nitrogen content,bacterial count and rheological properties and sensory evaluation of different Lactic acid bacteria in Manchu sour tea,we can screen out the suitable lactic acid bacteria for the fermentation of Manchu sour tea.We know that Lactobacillus plantarum,Lactobacillus casei and Lactobacillus rhamnosus showed rapid acid production and a large number of bactrial count.The free amino nitrogen content reached 2.85±0.26 mmol/L,2.73±0.15 mmol/L and 2.71±0.14 mmol/L.They also had better rheological properties and sensory evaluation.Lactobacillus casei got the highest score of 7.42±0.61 points,followed by Lactobacillus rhamnosus and Lactobacillus plantarum with 7.18±0.49 and 6.78±0.41 points.In summary,we selected Lactobacillus casei,Lactobacillus plantarum,and Lactobacillus rhamnosus as fermentation strains and the optimal compounding ratio was determined by sensory evaluation to be Lactobacillus casei: Lactobacillus plantarum: Lactobacillus rhamnosus(When v:v:v)is 1:2:1,the sensory evaluation score of Manchu sour tea is 8.71±0.72 points,and this compounding ratio was selected for subsequent experimental research.(6)The fermentation process conditions of Manchu sour tea were optimized.On the basis of single factor experiments and response surface experiments,the main influencing factors affecting the titration acidity can be obtained and they are lactic acid bacteria inoculum,fermentation time,initial p H and fermentation temperature.The best fermentation process conditions of Manchu sour tea were 5% lactic acid bacteria inoculum,37 °C,initial p H 6.50,6 h.Under the conditions,the titration acidity reached 72.12 °T.(7)Using ultra-high pressure technology for passivation after fermentation of Manchu sour tea,and the conditions were 4 ?/0.1 MPa/24 h,4 ?/50 MPa/15 min,4 ?/100 MPa/15 min,4 ?/150 MPa/15 min and 4 ?/200 MPa/15 min.The conditions of 4 ?/0.1 MPa/24 h was comparison group.The contents of protein,fat and reducing sugar all decreased with the increase of ultra-high pressure after passivation.The amino acid content under partial pressure conditions such as serine,threonine,arginine,proline,methionine,isoleucine,leucine and phenylalanine was lower than that of the comparison group,and other amino acid contents were significantly higher than the comparison group.The effect of elevated pressure on p H was not significant.The titration acidity shows a downward trend with increasing pressure,and the sensory evaluation score has the opposite trend.It can be seen that the ultra-high pressure technology can effectively shorten the passivation time,so that the nutritional value of Manchu sour tea was higher and the sensory evaluation was better.(8)There were 96 main flavor substances identified from Manchu sour tea produced by five kinds of different passivation conditions.Classify these flavor substances according to alcohols,aldehydes,ketones,acids,esters.There were 29 kinds of alcohols,20 kinds of aldehydes,20 kinds of ketones,8 kinds of acids and 19 kinds of esters.With the increase of passivation pressure,most flavor substances that produce undesired flavors show a downward trend,such as pentanol,hexanol,trans-2-heptenal,hexanal,etc.Some flavoring substances with grain-specific flavors such as 1-octene-3-ol,trans-2-nonenol,decyl alcohol,2,3-butanedione,acetic acid,etc.,rise with increasing passivation pressure trend.The content of other flavor substances was lower,and there was no obvious law with the change of passivation pressure.In summary,using ultra-high pressure technology on passivation of Manchu sour tea can improve the flavor.