Study Of The Prodution Process And Flavor Compounds Of Orange Vinegar

Fruit vinegar, using fruits as raw material, is a kind of brewed vinegar. It has the flavor and nutritional value of both fruit and vinegar, and can be used as a condiment to meet cooking needs and blended as a green drink to meet people’s pursuit of health and delicacy. Fruit vinegar has a long history and a wide range in Western countries, while the fruit vinegar market in China is just at the beginning stages and the species are mostly apple vinegar. China is the world’s largest producer of citrus but has a very low proportion of citrus processing. Defective citrus waste and unmarketable fresh citrus are the major issues of China’s citrus market. Therefore, this study focuses on Gannan navel orange, which accounts for the highest proportion of Chinese citrus, using the defective oranges as raw material to develop fermented orange vinegar and to study its flavor compounds.Firstly, the orange juice was pretreated before fermentation. The juice contains limonin and naringin, which can cause bitterness. The determination results showed that, in the juice of freshly picked oranges, the content of limonin was 7.16 mg/L(threshold of 1 mg/L), the content of naringin was 17.57 mg/L(threshold of 30 mg/L). So the bitterness was from limonin. The natural metabolic debittering and resin adsorption debittering was carried out and their conditions were optimized. The results showed that, under the optimum conditions of natural metabolic debittering(24°C, 12 d), limonin removal rate was 90.36%. The sugar-acid and p H of the juice increased and nutrients were unchanged. The limonin removal rate was 88.71% under the optimum conditions of adsorption debittering(R3 resin, the ratio of diameter to height 1:20, a flow rate of 8 BV/h), but the content of sugar, Vc and soluble solid declined. So the natural metabolic debittering was chosen.Secondly, the brewing process was studied. Two-step fermentation of alcohol and acetic acid fermentation were adopted. During alcohol fermentation process, the best fermentation conditions were sugar of 15 g/L, temperature of 30°C, 32 h. The output of ethanol was 52.26 g/L and the yield of ethanol was 92.78%. During the acetic acid fermentation phase, the optimized fermentation conditions were fermentation inoculum of 10%, temperature of 30°C, 168 h. The eventually total acids content was 50.95 g/L and the yield of acetic acid was 66.39%.Then, the sterilization and aging process were studied. The orange vinegar was processed by using pulsed electric field(PEF). The best sterilizing effect was 5.24 log reduction at electric field intensity of 25 k V/cm, treatment time of 300 μs, frequency of 200 Hz, and pulse width of 2.0 μs, which was better than that of the thermal pasteurization. The thermal treatment caused the loss of color and soluble solid but PEF processing did not. PEF also accelerated the aging of orange vinegar. The GC-MS showed that after PEF treatment, the changes of flavor compounds in the vinegar had the same trend as natural aging(one-month level). The esters content increased more than that of the natural aging, which made the orange vinegar taste mellower.Finally, after blend, with sensory evaluation as index, the optimum formulation of orange vinegar beverage was vinegar of 15%(v/v), fresh orange juice of 50%(v/v) and sugar of 2%(w/v). And the quality standard of orange vinegar beverage was established according to the relevant standards.