Studies On The Fermentation Process Of Mulberry Wine And The Antioxidant Activity Of Phenolics

In this dissertation, using nine mature fresh mulberry as raw material and adopting pure fermentation technique to produce mulberry wine at a constant temperature, summed up the fermentation process of simple,reliable and suitable for industrial production.The structures and activities of common phenolic compounds in the mulberry wine were analyzed by using quantum chemical method.On this basis, for gallic acid and caffeic acid, investigated the possibility of the synthesis of phenolic-metal salts.By studying the effect of apple juice concentration, mulberry juice concentration, fermentation temperature on the quality of mulberry wine, after the single-factor test and sensory evaluation to determine the optimum fermentation conditions of mulberry wine were below:sugar content of juice is 20°Brix, mulberry juice concentration is 8%, fermentation temperature is 20℃, after repeated tests to prove that the process conditions is reliable. Fermentation under these conditions, the mulberry wine was purple, pure taste, strong fruit aroma and best typicalness.With the Gaussian03 program, twelve kinds of phenolic copounds were calculated by DFT/B3LYP method at the 6-311++G** basis set level. Through molecular geometry optimization and energy calculation, quantum chemical parameters for characterizing the relationship between the compound structures and activities could be gained, such as:charge distribution, the frontier orbital energies, gas-phase bond dissociation enthalpies (BDE) and ionization potential (IP). The results showed that the differences in antioxidant property between twelve phenolic acids derived from dehydrogenation capacity of phenolic hydroxyl in the molecules and the influence of ortho substituent in the benzene ring. In non-polar solvents, the antioxidant activities of twelve phenolics in the following order:caffeic acid> gallic acid> chlorogenic acid> ferulic acid> sinapic acid> protocatechuic acid> p-coumaric acid> 2,4-dihydroxybenzoic acid> gentisic acid> vanillic acid> syringic acid> salicylic acid; and in polar solvents, the antioxidant activities of twelve phenolics in the following order:gallic acid> caffeic acid> chlorogenic acid> ferulic acid> sinapic acid> protocatechuic acid> p-coumaric acid> 2,4-dihydroxybenzoic acid> gentisic acid> vanillic acid> syringic acid> salicylic acid. Poassium gallate and caffeic potassium were synthesized in aqueous solution by using gallic acid, caffeic acid and potassium hydroxide as raw material. Through infrared spectroscopy and thermal decomposition behavior analysis, the synthesized salts were characterized. The results showed that the H ions on the carboxyl group was replaced by metal ions in the synthesis process of phenolic-metal salts, and the stability of the synthesized salts had a certain extent improved than phenolic compounds.