Study On The Fermentation Technology, Main Compositions And Antioxidant Activity Of Taro Vinegar

Taro has various amino acids with reasonable composition, low content of fat and high digestive starch. In addition, it is rich in vitamins, minerals, polysaccharide and so on. Therefore, taro is a high quality food and can prevent hyperacidity, improve the metabolism of free radical and enhance immune function. Taro resource is abundant in China, but taro is mainly used as fresh eating at present and the wastage after harvest is serious. In this study taro was used as raw material to preparing healthy fermented vinegar, on the basis of the research of fermentable sugar preparation, alcohol and acetic fermentation technology of taro pulp, the main components and antioxidant activity of taro vinegar were detected and analyzed, furthermore, the formula of taro vinegar beverage was explored primarily. The aim of this paper was to enhance the economic value of taro, enrich the demand of food therapy and health care, and provide the reference for the large scale production of taro vinegar and its beverage. The main results were as follows:(1) The particle size and apparent viscosity of taro paste were reduced effectively after the pretreatment of cellulase, pectinase and neutral protease. Then thermostable a-amylase and glucoamylase were used to treat the taro pulp, finally, the starch was almost completely hydrolysis and the reducing sugar content was high. The optimal enzymolysis conditions of cellulase and pectinase were enzyme dosage 70U/g, the ratio of cellulase and pectinase 3:1, time 50min, temperature 50℃, the juice yield was (67.93 ±0.10)%. The best enzymolysis parameters of neutral protease were enzyme dosage 2000U/g, time 5h, temperature 45℃, pH 7.4, the hydrolysis degree of protein was (26.85±0.03)%. The optimal liquefaction conditions were a-amylase 8U/g, time 2.Oh, temperature 85℃, pH 7.5, the DE value was (12.07±0.06)%. The best saccharification parameters were glucoamylase 170U/g, temperature 55℃, time 125min, pH 4.7, the DE value was (21.37±0.06)%.(2) Dry yeast with high activity was selected as starter for alcohol fermentation using taro pulp. The optimal method and conditions of this fermentation process which obtained by single factor experiments and Box-Benhnken design methods were using cloudy juice, initial sugar content 16g/100mL, volume-loading 50mL/100mL, time 3.0d, pH 5.6, temperature 29.5℃, inoculation volume 0.55%. Under these conditions, the degree of alcohol in the fermentation pulp reached (8.49 ±0.03)%. With Huniang 1.01 as strain, the acetic fermentation parameters were determined by one-at-a-time and Box-Benhnken experiments. The results were as follows:addition amount of peptone 1g/100mL, volume-loading 30mL/250mL, temperature 31℃, time 5d, rotate speed 155r/min, inoculation volume 11.5%、addition amount of glucose 3.3g/100mL, initial alcohol content 8.3%. Under these conditions, the content of total acid reached (6.35+ 0.03)%.(3) The detection results of the main components of taro vinegar showed that it contained 14 kinds of amino acids, among which arginine and histidine content were the highest and reached 34.84mg/100mL and 29.67mg/100mL respectively. There were seven essential amino acids (lysine content was the most) in all and the amount was 56.72mg/100mL, which accounted for 38.93%　of total amino acids. Taro vinegar was rich in acetic acid and had a certain amount of lactic acid, malic acid, citric acid and a small amount of fumaric acid. The total protein, polysaccharide, polyphenol and free amino nitrogen content of taro vinegar were significantly higher than white vinegar,9° rice vinegar and apple cider vinegar sold on market but the total acid content of it was lower than 9° rice vinegar. The results of antioxidant activity tests of taro vinegar revealed that the total antioxidant capacity, DPPH radical scavenging activity, hydroxyl radical scavenging ability and reducing power of it were higher than that of white vinegar,9° rice vinegar and apple cider vinegar, but the ability of scavenging superoxide anion was lower than that of 9° rice vinegar.(4) The formula of health fermented taro vinegar beverage was explored primarily, using taro vinegar and extraction of honeysuckle, chrysanthemum and Chinese wolfberry as principal raw material. And the optimal formula was 15%　taro vinegar, 40%　Chinese herbal medicines extraction (the ratio of honeysuckle, chrysanthemum and wolfberry was 1:1:2),0.03g/100mL sour agent (the ratio of citric acid and malic acid was 1:2),12g/100mL sweeteners (the ratio of honey and white granulated sugar was 1:5). This yellowish, glossy and clear beverage had moderate and refreshing taste, no precipitate and suspended matter. It also had strong fermented vinegar flavor, delicate fragrance of Chinese herbal medicines and no stimulate flavor. Fuzzy comprehensive evaluation method indicated that the grade of taro vinegar beverage was between "good" and "not so good", which showed a larger tend to be grade "good"...