Study On The Bitter Substances And Its Control Technology Of Citrus Wine

The cultivation area and yield of citrus in China have been the highest in the world,but the domestic citrus processing capacity is less than 5%of the total yield.In order to extend the citrus industry chain and promote the healthy development of the citrus industry,developing citrus wine is an effective way.However,the bitter taste of citrus wine restricts its market’s acceptance seriously.The goal of this study is to reduce the bitter taste of citrus wine.The detection method of the main bitter substances in citrus was firstly established.Then,with navel orange as the raw material,the changes rule of bitter substances in citrus,citrus juice and citrus wine were deduced through laboratory tests and modern testing techniques.Finally,experiments were carried out regarding raw material treatment,optimization of brewing technology and improvement of citrus distilled wine technology,aiming to provide technical support and theoretical basis for the industrialization of low bitterness citrus wine.The main results are as follows:（1）Key parameters for Ultra Violet spectrophotometry（UV）and Ultra Performance Liquid Chromatography（UPLC）were selected.In particular,UV method was used to detect the limonin analogue.The maximum absorption wavelength and the optimal color developing time of UV for limonin analogue was 491 nm and 20 minutes,respectively.UPLC was used to detect limonin,nomilin and naringin,and the selected parameters for limonin and nomilin were as follows Mobile phase:the ratio of acetonitrile to water was 45to 55,isocratic elution;flow rate:0.3 mL/min;chromatographic column detection temperature:30℃;detection wavelength:215 nm;injection volume:1.0μL.Meanwhile,the selected parameters for detecting naringin by UPLC were as follows.Mobile phase:the ratio of methanol to water was 40 to 60,isocratic elution;flow rate:0.3 mL/min;detection temperature of chromatographic column:30℃;detection wavelength:283 nm and injection volume:0.3μL.（2）The change rule of bitter substances in citrus was studied.Fengjie navel orange was selected as the raw material.During the growth and development process of the citrus fruits,the contents of limonin,nomolin and naringin in the exocarp,endocarp,sac layer and juice cell all follow the trend that increased firstly and then decreased,and finally tend to be stable.During the brewing process of citrus wine,the contents of limonoids fluctuated,reaching the lowest value on the 8th day and restoring the higher level at the end of fermentation.Notably,during the brewing process of citrus wine at 4℃,the content of limonoids showed a decreasing trend.（3）Three main bitter substances in citrus,namely limonin,nomilin and naringin,were evaluated.Limonin,nomilin and naringin present different bitterness characteristics.The perceptual thresholds,recognition thresholds and limit thresholds for limonin,nomilin and naringin in purified water,simulated citrus juice and simulated citrus wine all showed increasing trend,but the three thresholds of naringin were higher than that of the other two bitter substances.The effects of sugar,acid and pH value on the thresholds of limonin and nomilin were basically the same,but differ from that of naringin.In addition,the perceptual thresholds of the three bitter substances would be inhibited mutually when coexisting in a certain proportion.（4）Citrus fruits were treated with six physical methods,i.e.infrared,microwave,pasteurization,ultrasonic,ultra-high pressure and ultra-high temperature,in order to evaluate their influence on the bitterness of citrus wine.The results showed that infrared,pasteurization,ultrahigh pressure and ultra-high temperature processing only reduced the content of limonoids and limonin in citrus juice,but failed to decrease the contents of the corresponding bitter substances.The turbidity of citrus wine were reduced after being treated by microwave,ultrasonic and ultra-high temperature for 2 min and 4 min.According to the sensory evaluation,all kinds of treatments could lead to the change of color and aroma of citrus juice and citrus wine,thus further lowering the overall qualities of citrus juice and citrus wine to some degree.（5）The low bitter fermentation process of citrus wine was optimized.The key points of the process can be summarized as follows.The storage temperature of raw materials should be 4℃,the airbag should be selected for juice extraction.In the brewing process of citrus wine,it is recommended to prohibit or minimize the addition of SO₂.The commercial yeast BV818（Saccharomyces cerevisiae）is recommended for brewing citrus wine.The brewing temperature of citrus wine is suggested to be about 18℃.Through the L₃⁴ orthogonal and L₂³optimization experiments,the best fining agents were agar of 125 mg/L and gelatin of 30mg/L.（6）The production technology of distilled liquor made from citrus wine was improved.According to the comparative study of citrus juice,citrus wine（citrus peel wine）and distilled liquor made from citrus wine（distilled liquor made from citrus peel wine）,with the increase of alcoholicity,the contents of limonoids were reduced,while the proportions and contents of aroma substances tended to be optimized and increased.The distilled liquor made from citrus wine has a promising market prospect,due to its similarity to grain liquor and abundant alcohol compounds,acid substances,limonoids and phenols with biological active.