Study On Immobilized Fermentation For Red Bayberry Vinegar And Its Antioxidant Activity

Nowadays, two-step submerged fermentation with free cells has became the fundamental process in red bayberry vinegar brewing. However, due to the long fermentation time and continuing oxidation in acetic acid fermentation stage, the original fruit flavor, color and polyphenol of red bayberry vinegar will be lost, and then lead to vinegar quality reducing significantly in this study, red bayberry of ’Dongkui’ species was used as main material, combined with the immobilized fermentation technology, to optimize fruit vinegar process with the selected carrier for Acetobacter adsorption. The basic chemical compositons, polyphenols and characteristic aroma components during red bayberry vinegar fermentation were investigated using chemical analytical and instrumental analysis methods. Furthermore, the health care effects of red bayberry vinegar were assayed using antioxidant activities and liver protection tests. The main researches of them are the following:1. Four strains of Acetobacter and eight kinds of carriers were used to screen the fermentation bacteria and natural carriers using index of acid rate and cell adsorption density. Two sets of operating parameters for immobilized fermentation with fermentation time within12days and95%of acid transfer rate were carried out: Ganoderma plasmid as carrier with up to106cfu/mg of acetic acid bacteria (XZJ002) as microbial strain, and bagasse as carrier with up to107cfu/mg of Malodorous Acetobacter (AS1.41) as microbial strain.2. The optimum immobilized fermentation technology for red bayberry vinegar with107/cfu/ml of acetic acid bacteria starter, cell adsorption density of up to106cfu/mg in carrier, and less than3.8%(v/v) of alcohol content in culture, was investigated from2to10little fermenters using acetic acid bacteria (XZJ002) adsorbed on Ganoderma plasmid.3. The results of compositions detected during different stages of vinegar fermentation show that, the total polyphenols contents will reduce gradually from juice, wine to vinegar cultures, but the proportion of organic acids will change greatly. The contents of total phenols among red bayberry juices, wine and vinegar were 94.5μg/mL,84.5μg/mL and84.0μg/mL, respectively. It is said that the polyphenol component partly lost in the two-step fermentation process. In this study, citric acid was the major organic acid in bayberry juice and wine, accounted for52.5%and53.9%of the total organic acids, respectively. The main organic acids of red bayberry vinegar are acetic acid and citric acid, accounting for46.9%and27.2%, respectively.4. The aromatic compositions of red bayberry juice (33constituents), wine (36constituents) and vinegar (42constituents) were identified using GC-MS method by extraction with methylene chloride. Red bayberry juice is dominated by caryophyllen, hexadecanoic acid,4,4,8-trimethyl-tricyclo [6.3.1.0(1,5)] dodecane-2,9-alcohol,2-cetyl alcohol, O-butylene terephthalate, octadecanoic acid,12-hydroxy stearic acid, B-phenylethanol, citric acid diethyl, citric acid ethyl ester, a-caryophyllene. Compared with bayberry juice, the aroma of wine is constituted mainly by B-phenylethanol, dihydroxyphenylethanol, ethyl succinate,9-octadecenoic trans enoate, octyl acetate, methyl amyl butyrate, butyrolactone,2-hydroxy diethyl succinate because of yeast fermentation, however, the original terpenes in juice such as caryophyllene, a-caryophyllene, iso-caryophyllene and caryophyllene oxide damnify seriously in wine. The volatile composition of the fruit vinegar is mainly dominated by alcohols (B-phenylethanol,4,4,8-trimethyl-tricyclo [6.3.1.0(1,5)] dodecane-2,9-alcohol,2-cetyl alcohol), esters (citric acid diethyl,citric acid mono ethyl) and acids (hexadecanoic acid). Phenyl ethyl acetate belongs to the new aroma, but ethyl succinate and octyl acetate which are original aroma in wine vanish in vinegar. By comparing the characteristic aroma components among batches of10L fermenter vinegar samples, the main aromatic components between batches showed no changes except ethyl succinate and t-hexadecyl mercaptan.5. The antioxidant activities of red bayberry fruit vinegar, juice and wine, as well as apple vinegar and sorghum vinegar, were comparatively assayed using hydroxyl radical scavenging, the1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenger, and the reducing capacity methods. The results show that the antioxidant activities of red bayberry samples decreased systematically from juice, wine to vinegar especially in low concentration testing level. However, the antioxidant power of the vinegar enhanced with88.3%of hydroxyl radical scavenging rate and63%of DPPH radical scavenging rate as testing level increasing to30%concentration. The antioxidant capacity of red bayberry vinegar was less than that of sorghum vinegar, however, significantly higher than that of apple vinegar. Strategically, red bayberry vinegar beverage with a higher content of original vinegar has potential application because of its favorable antioxidant power.6. The liver protective effects for red bayberry juice and vinegar were primarily studied. A mouse model of acute alcoholic liver injury using Erguotou wine with55%(v/v) alcohol content was established. Red bayberry vinegar, juice and glacial acetic acid were used to intervene alcohol metabolism of rats, and AST, ALT in Serum, ADH, MDA and SOD in liver were detected as evaluating indicators. The results show that there are significant difference among indicators between the model group and the control group, the model mouse were successfully acute liver injury. It means that bayberry vinegar and bayberry juice both express hepatoprotective effect, and that the effect of vinegar was better than juice. However, there was no relativity between red bayberry vinegar and its acetic acid content in hepatoprotective effect. Glacial acetic acid group hepatoprotective effect is not obvious and it may cause further damage to the liver.