Study On White Radish Beverage Fermented By Lactic Acid Bacteria

Lactic acid bacteria is a kind of bactetia that can use sugar to ferment and produce a large number of lactic acid.Also,protein can be decomposed into low molecular peptide and amino acid by lactic acid bacteria.The metabolites of lactic acid bacteria can increase the intestinal immunity of human body.It has been widely applied in the industry,agriculture and medicine field,such as pickled vegetables,dairy products processing,livestock and poultry disease prevention and control.Lactic acid fermented beverage possess not only the nutrition value of material itself,but also contains the probiotic effects of fermented products.The acids and alcohols produced can occur esterification reaction during the ripe stage of fermentation and generate aromatic substances.Currently,fruit and vegetable juice fermented drink are fermented with the method of natural fermentation,which has long fermentation cycle and cannot fully guarantee safety.Also,it has low degree of industrialization and standardization,and there are few reports about the radish juice fermented drinks.Although fermenting carrot drinks with single commercial strains can solve the problem of long fermentation cycle,but the commercial strains is not suitable as a special fermentation strains because of its poor beverage flavor.In this paper,Yunnan white radish varieties which is cultivated at the Vegetable Institute of Zhejiang Academy of Agricultural Sciences was chosed as raw material to start a natural fermentation and the flavor was used as the main criteria to screen out the fermentation strains with perticular flavor.The strain was inoculated in the white radish juice with L.Plantarum later and the orthogonal experiment was used to optimize the fermentation technology.The fermentation performance was researched finally.The main results were listed as follows:(1)Strain of lactic acid bacteria was screened to ferment white radish juice drink:The orthogonal experiment was used to optimize the natural fermentation technology of white radish juice.The best fermentation conditions were determined.The additive amout of sugar(25%),fermentation temperature(28 ?)and fermentation time(72 h)were determined.Under these conditions,the fermented liquor got high scores under different conditions of color,fragrance,taste,and refreshing degree.The natural fermented radish juice beverage was used as raw material to screen strains.The beverage was diluted with gradient,coated on culture medium and steaked to screen the single colony.The acid production and sensory evaluation were tested as the main criteria for first screen and second screen.And the morphological identification,Gram staining identification,physiological and biochemical identification and 16SrDNA sequences were researched to screen out the strains of lactic acid bacteria.The acid production of 24 strains screened was tested.The results showed that pH value of the beverage inoculated with strain No.18 was decreased fast and it was in a stable state after 48 hours.At this moment,radish juice beverage inoculated with YZ18 has a higher score(87 points)in four indicators of color,aroma,taste and refreshing degree.After bacterial colonies morphological identification,bacteria identification,physiological and biochemical identification and 16SrDNA sequences analysis,the bacteria was identified as intestinal membrane Leuconostoc(Leuconostoc mesenteroides subsp.),named Leuconostoc mesenteroides subsp.YZ18.(2)Inoculation process was identified and optimized:The perticular strain(Leuconostoc mesenteroides subsp.YZ18)was mixed with the commercial bacteria lactobacillus(L.Plantarum)to inoculate radish juice fermented drinks.One step fermentation(Leuconostoc mesenteroides subsp.YZ18 and L.Plantarum inoculated concerrently)was compared with two steps fermentation(Leuconostoc mesenteroides subsp.YZ18 and L.Plantarum inoculated respectively)in their fermentation characteristics.The best way of inoculation was determined with the evaluation standards including pH,acidity value,soluble solid content and sensory evaluation.The conditions of inoculation(total inoculation quantity,inoculation proportion and fermentation time)were optimized by single factor test and orthogonal test.The results showed that the two steps fermentation process was more suitable for radish juice fermented beverage.The order of inoculation was Leuconostoc mesenteroides subsp.YZ18 inocuated 12 hours earlier than L.Plantarum.The total inoculation quantity of 3%(V/V),inoculation ratio of 2:1(V/V)and fermentation time of 36 h were determined.(3)Nutritional ingradient and volatile components of white radish original juice,steep liquor and fermentation liquor were determined and analysed.The total sugar content of fermentation liquor was decreased.The total acid content was increased from 0.45 g/kg to 3.63 g/kg.Vc content was decreased from 11.93 mg/100 g to 3.93 mg/100 g and pH value quickly reduced from 5.99 to 3.61.Soluble solids were only reduced a little.The order of magnitudes of lactic acid bacteria was increased from 104 cfu/mL to 108 cfu/mL,and it was the same to that of active lactobacillus of beverage on the market.The total free amino acid content and the esssential amino acid content in the products were decreased along with the fermentation.16 kinds of amino acids were detected and the content of glutamate(Glu)was the highest in the total free amino acid and the content of histidine(His)was the highest in the essential amino acids.There are esters,sulfide,olefins in the volatile flavour compounds of these three liquor detected by SPME and GC-MS.The volatile flavor components of fermentation liquor were relatively abundant containing sulfide,esters,olefin,alcohols,phenols and ethers.The special esters material in the fermentation liquor areused as spices in food and they were the main source of characteristic flavor in fermented liquor with fruit flavor.The special olefin material has the function of antiphlogosis,and the special Menthol is generally used as odorant in toilet water.