| Chinese rice wine is a kind of brewing wine,which is taken rice,wheat,corn,millet as the main raw material,and made by cooking,saccharification and fermentation,pressing,filtering,sterilization,storage and blending.But the molecular components of the new brewed Chinese rice wine is unstable,the taste is rough and fragrance is insufficient,so the aging process is needed.During aging process a series of chemical reactions took place,made the Chinese rice wine to be soft and valuable.However,the traditional process of rice wine aging is time consuming,so it's important to reduce the aging time of Chinese rice wine for brewing industry.Ultrasonic technology is useful to accelerate the aging process,which could provide transient high temperature and pressure in the process of the huge shear force.It's conducive to a series of physical,chemical and biochemical reactions,so it can improve the taste and flavor of rice wine,and shorten aging time.In this paper,four kinds of ultrasonic equipments were used to study the ultrasonic treatment effects on two kinds of rice wine.The optimum treatment condition was obtained by using the most suitable ultrasonic equipment.The changes of the main ingredients in rice wine stored for different days were analyzed,and the effects of free radicals produced during ultrasonic process on the maturation of rice wine were also analyzed.(1)The results of two kinds of Chinese rice wine treated by four kinds of ultrasonic equipments showed that the single-frequency ultrasonic of 40 kHz performed the most significant effect on the new base liquor.The total ester contents of the new base liquor treated by 40 kHz ultrasound increased by 7.33% compared with that of untreated wine.When stored for 7 days,the total ester and amino acid nitrogen contents increased by 9.60% and 5.39%,which showed significant difference compared to that of untreated wine(p?0.05).On the basis of single factor test and response surface experiment,the optimum treatment conditions were obtained as follows: the ultrasonic temperature 30 ?,ultrasonic time 20 min,ultrasonic power density 250 W/L.Under this condition,the contents of total acid and total ester were14.26 g/L and 4.10 g/L,which were increased by 4.31% and 12.75%,respectively,compared to the untreated wine.(2)When Chinese rice wine was treated by 40 kHz ultrasound,the total sugar gradually decreased with the increase of the standing time.The total sugar of sonicated wine reduced by 29.33% when after six months storage compared with theuntreated rice wine.The content of the total ester increased gradually,and it increased by 14.65% when stored for six months compared with the untreated rice wine.And the content of soluble solids increased as the storage time passed by,and there was a significant difference(p?0.05)compared to the untreated wine when stored for six months.The total aldehyde content increased firstly then decreased,and it was lower than that of the untreated wine.(3)The effect of ultrasound to organic acids in Chinese rice wine showed no significant difference in malic acid,citric acid,ketoglutaric acid,oxalic acid and tartaric acid compared to the untreated rice wine.The content of acetic acid decreased by 12.95% when stored for six months compared with the untreated rice wine.With the increase of the time after sonicated,the total amount of organic acids showed a gradual increase trend.The total amount of organic acids in ultrasonic and non-ultrasonic wines were 5184.47 mg/L and 5391.56 mg/L,respectively,when sonicated and stored for six months.(4)The effect of ultrasound on violate substances in Chinese rice wine were studied through the analysis of HS-SPME-GC-MS.The amount of alcohols and esters were relatively high,while the acids and aldehydes were relatively low.The esters and the total amount of the volatile compounds gradually increased with the increase of storing time,and they increased by 286.78% and 40.23% when stored for six months compared with the untreated rice wine.(5)The UV-Vis spectra of methylene blue solution using 40 kHz ultrasonic treatment at different ultrasonic time was measured.The results showed that the peak absorption of the methylene blue solution was 664 nm,and the intensity gradually decreased with the increase of ultrasonic time.The fluorescence emission spectrum of phthalic acid before and after sonication was detected,it was found that with the increase of ultrasonic time,the amount of hydroxylated terephthalic acid in the system increased.Taken DMPO as hydroxyl radical scavenger,the1-hydroxyethyl free radical was detected by using the electronic paramagnetic resonance spectroscopy between natural aging rice wine and rice wine after sonicated.However,the content of 1-hydroxyethyl radicals did not gradually rose with the increase of ultrasonic time.The ultrasonic cavitation yield was measured by ultraviolet spectrophotometry,it was found that the cavitation effect increased significantly as well as the content of total acid and total ester with the increase of ultrasonic time(P?0.05).(6)The sodium benzoate was used as free radical scavenger to verify the free radicals produced by ultrasonic cavitation.The results showed that no significant increases of total acid,total ester and amino acid nitrogen in ultrasonic treated rice wine which had been added sodium benzoate.It might be explained that the process of ultrasound could produce free radicals,and free radicals was conducive to the maturation process of rice wine. |
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