Study On Brewing Technology And Flavor Control Of Noni Wine

Noni(Morinda citrifolia L.)is a tropical plant widely planted in Taiwan,Hainan and Xisha islands of China,which has attracted wide public attention with abundant nutritional values and biological activities as a new resource of food.Fermented juice is the main commercial product of Noni industry,and it is decomposed from mature fruits by endophytic bacteria in the traditional processing method.However,this inefficient parttern of production not only consumes time,but also has potential hazards because of the difficulty of quality control,which affects the product promotion and industry development.Noni has effective anti-microbial attributes,so it is hard to inoculate yeast for fermentation directly.Because the rich fiber content,juice yield and the utilization rate of the whole fruit are low,as well as a kind of special butyric acid odor leads to the undesirable sensory acceptance,which results in the challenge of processing.In this study,the antimicrobial components and properties of Noni were analysed and adjusted.By pulsed electric field pretreatment,the utilization rate and the quality of fruit juice were improved.Besides,the fermentation technologies were optimized and the kinetic models were established.The aroma profile of Noni was perfected by increasing contents of alcohols and esters within fermentation,which was evidenced by comparing the volatile components and characteristics of Noni at different maturity stages.The research major contents and conclusions are as follows:1.Due to the high content of fiber and low juice yield,the utilization rate of Noni is insufficient.Under the condition of the unipolar exponential wave with electric field intensity of 1.5 kV/cm,1 Hz,pulse width of 100 ?s and 30 pulses,the juice yield increased by 13.37% and the concentration of amino acids doubled.Pulsed electric field,as an efficient pretreatment technology,could significantly improve the utilization rate of whole fruit and the quality of fruit juice,which revealed a good application prospect in wine making industry.2.Noni has effective anti-microbial attributes,which leads to the difficulties of fermentation directly.Abundant polyphenols and flavonoids in Noni such as ferulic acid,chlorogenic acid,caffeic acid,p-hydroxybenzoate and rutin made great contributions to delay the logarithmic phase of the yeast and reduce its concentration.Ferulic acid and chlorogenic acid contributed the most to this attribute,and the contents in juice were 1046.83 mg/L and 163.29 mg/L respectivly,while the minimum bacteriostasis concentrations were 125 mg/L and 25 mg/L.pH value significantly affected the bacteriostatic activity.Specifically,ferulic acid and chlorogenic acid decreased below the minimum bacteriostatic concentration at pH 6.5 and 5.0,which indicated that the growth of yeast could be improved by reducing juice acidity.3.Noni has a special butyric acid odor resulted in the undesirable sensory acceptance,and the flavor profile could be improved by increasing the content of alcohols and esters through fermentation.pH,initial sugar content,yeast inoculation concentration and fermentation temperature affected the alcohol,fusel oil contents and sensory attributes significantly.The technological parameters were determined as: pH 6.8,initial sugar content 180 g/L,yeast inoculation concentration 400 mg/L and temperature 26°C.The changes of bacterial growth,residual sugar,alcohol and higher alcohols could be fitted by Logistic equation,substrate consumption equation and Leudeking-Piret equation well.4.The high concentration of chain fatty acids formed the distinct "rotten cheese" odor characteristics of Noni,as well as a special flavor of green fruit was originated form ?-terpineol,3-methyl-3-butene-1-alcohol and 3-methyl-2-butene-1-alcohol.Fermentation could significantly reduce fatty acids contents,promote alcohols and esters formation,which improved the product aroma profile.Higher alcohols such as isobutanol,isoamyl alcohol and active amyl alcohol enriched the decent fruit aroma in wine.Isoamyl acetate,ethyl benzoate,benzyl benzoate,2-hydroxybenzoate,DL-limonene,linalool and o-eugenol played a significant role in the flavor of Noni wine.5.Noni wine was insuffiecent in acidity with 14.17 g/L of dry extracts,which indicated that it lacked of skeleton with unbalanced taste.Jujube juice was selected as compound raw materials because of its great soluble solids with similar color could make up for the shortage of Noni and enrich aroma conpoentens.Before fermentation,50 pulses pretreatment towards jujube mash in 1.5 kV/cm,1 Hz could improve 10.02% dry extracts of the product.Sensory evaluation results showed that when the proportion of Noni: jujube was 80: 20,the product color and fragrance were bright and elegant with the balanced body,while still retaining Noni characteristics typicality.Fifteen new aroma compounds were identified,among which,acetal,heptaldehyde,3-methyl-2-hexanol,ethyl myristate,phenylethyl acetate,?-pinene and ?-Damastone all exceeded their odor thresholds and dry extrcts increased to 19.71 g/L finally.6.The physical and chemical properties and microbial indicators of the product acheived the national safety standards.The total phenols and flavones contents towarded 89.26 mg/100 mL and 24.01 mg/100 mL.DPPH,ABTS· and hydroxyl radical scavenging rates reached 56.28%,48.14% and 52.01%,respectively,which indicated a good antioxidant ability and health function effect.