Effect Of Microbial Fermentation On Antioxidant Activity Of Ginger Oleoresin And Optimization Of Fermentation Conditions Of Ginger Wine With Mixed Bacteria

As a common spices,ginger contains a variety of bioactive components including non-volatile and pungent gingerol,thus having many functions such as antioxidant,inhibition microbes,getting rid of cold,promote blood flow.Ginger oleoresin is a semi-liquid mixture obtained by supercritical CO₂ extraction of dried ginger,which fully retains the active components and unique flavor of ginger.So it is a natural flavor and preservative and can be used as a substitute for ginger.However,its particular pungent smell made the products is not easy to be accepted by the public.The shogaol has higher bioactivity and weak bad smell,but its content in ginger is very little.It not only affects the functions,but also limits the application.Now,the methods for improving the ginger activities are chemical and physical,which has are low efficiency,high cost and having many side effects.But the research on transformation active substances of ginger by microbial fermentation is more less.In this experiment,three representative microorganisms,Rhizopus,yeast and lactic acid bacteria,were inoculated in the suitable medium and fermented with appropriate amount of ginger oleoresin.The effects of microbial fermentation on antioxidant activity were analyzed by the microbial biomass,pH value and the antioxidant activity of the culture.Based on the single factor experiment,the addition of ginger oleoresin,fermentation temperature and fermentation time as independent variables,antioxidant activity as response value,BBD design and response surface analysis were used to optimize the fermentation process.And the optimum fermentation conditions of Rhizopus oryzae MG1,Wickerhamomyces anomalus J2-5 and Lacotobacillus sp.LAB2 were obtained,and the fermentation products were analyzed by liquid chromatography?HPLC?.Then,the brewing experiment of ginger wine was designed by using laboratory brewing model.By inoculating the dominant microbes,optimizing the technological parameters,one healthy ginger wine was developed.The main results are as follows:?1?Rhizopus is an excellent strain in traditional fermentation industry,which can produce specific enzymes and other special metabolites under specific conditions.The effect of Rhizopus fermentation on antioxidant activity of ginger active substances is analyzed.It can provide a theoretical basis for the development of high value-added ginger flavor fermented food and the utilization of natural ginger resources.In the experiment of studying the effect of Rhizopus oryzae MG1 fermentation on the antioxidant activity of ginger oleoresin,through single factor test and response surface analysis,it was found that the optimum fermentation condition was that 70?L ginger oleoresin was added to 20 mL PDA medium and inoculated with 1%spore suspension,incubated at 33??150 r/min?for4 d.The smell of fermentation broth was fresher,the spicy smell was weakened,and the light lemon flavor was found,and the total antioxidant activity of the culture was increased by 69.15±1.01%.?2?Yeast is the most common food microorganism.In this experiment,the effect of Wickerhamomyces anomalus J2-5 fermentation on the antioxidant activity of ginger oleoresin was investigated.Through single factor test and response surface analysis,it was found that the optimum fermentation condition was adding 50?L ginger oleoresin to 20mL YPD medium.Inoculated with 1% logarithmic seed solution and incubated at 27? for 72 h,the total antioxidant activity of ginger oleoresin after fermentation was 47.60±1.77% higher than that before fermentation.?3?Lactic acid bacteria?LAB?are intestinal probiotics.LAB fermentation has a significant effect on the improvement of product flavor,nutrition and health care function.The effect of lactic acid bacteria fermentation on antioxidant activity of ginger oleoresin was analyzed.Firstly,the effect of the antioxidant activity by 5 LAB strains fermentation against ginger oleoresin was compared.The results showed that the total antioxidant activity by Lacotobacillus sp.LAB2 fermentation was significantly higher than that of other strains.The 16s rDNA sequence was compared by molecular biology method,and the similarity with Lacotobacillus plantarum was up to 99%.Then,through single factor test and response surface analysis,it was found that the optimum conditions for fermentation of ginger oleoresin by Lacotobacillus sp.LAB2 were as follows:adding 120?L ginger oleoresin to 20 mL MRS medium,inoculated with 1%logarithmic seed solution and incubated at 37? for 60 h.The total antioxidant activity of ginger oleoresin increased by 36.59±1.02% after fermentation.?4?High performance liquid chromatography?HPLC?was used to compare the standard products,essential oleoresin and microbial fermentation extract.The results showed that the content of active substances in the microbial fermentation broth of ginger oleoresin changed to varying degrees,and a variety of new substances were formed.After fermentation with three kinds of microorganisms,the content of substance 15 decreased significantly,the peak area of No.5 8-gingenol increased significantly,R.oryzae MG1 was newly formed 16,17,18,W.anomalus J2-5 formed 19,10,21,and Lacotobacillus sp.LAB2formed 19,20.?5?R.oryzae MG1 can significantly improve the antioxidant activity of ginger,and the smell of culture is fresh.So it could be used in the fermentation process of ginger wine to improve the flavor of ginger wine.During the optimizing process,several raw materials including white sugar,brown sugar,fructose syrup,sorghum juice and apple juice were added to fresh ginger juice to ferment,respectively.It was found that the sensory evaluation of culture added fructose syrup was the highest.Using fresh ginger juice and fructose syrup as raw materials,Saccharomyces cerevisiae and Rhizopus oryzae MG1 were mixed to ferment.The results showed that the initial sugar concentration was 17^oBx,and the inoculation of Rhizopus oryzae MG1 and Saccharomyces cerevisiae was 0.47% and 0.53%,respectively.After fermentation for 8 days,the fermented ginger wine has bright body,moderate acidity,excellent taste,rich ginger flavor,mellow wine and high popularity.The antioxidant activity of ginger wine fermented was higher than that of fresh ginger juice and single strain fermented ginger wine.