| Jujube(Ziziphus jujuba dates),also known as Chinese date,is the fruit of the genus Ziziphus,Rhamnaceae family.Originated in China’s Yellow River Basin,the history of jujube cultivation is over 8000 years.According to Chinese Statistical Yearbook,the production of jujube in 2012 reached 5.88 million tons which was more than 95%of world’s and maintains an annual growth rate more than 10%.At present,while a small amount of jujube was freshly consumed,a large amount was processed into dried jujube for directly eating and other raw materials.Furthermore,jujube was usually extracted by 95%ethanol,alkali and water to obtain jujube tincture,pigment and polysaccharide separately.But the jujube residue was not fully utilized which resulted a great waste.In this paper,the successive extraction technology was used to separate tincture,polysaccharide and pigment to achieve the full utilization of jujube resources.The main conclusion are as follows:1.The Zizyphus jujube cv.Junzao was used to investigate the main nutrients.The contents of each components are as follows:crude sugar 56.64%,moisture 18.04%,crude fiber 4.21%,ash 3.25%,protein 2.89%,crude fat 4.21%.Furthermore,the three factors four levels experiment of heating temperature(40,50,60,70℃),time(1,2,3,4 h)and solid-liquid rate(1:20,1:15,1:10,1:5 g/mL)on sensory quality of jujube tincture were investigated by 95%ethanol.The best extraction parameter was 80℃and 1:10 g/mL for 1 h.On this condition,the content of sugar,ethanol and paste were separately 49.5%,17.84%and 47.38%.The extraction ratio reached 47.38%.Besides,35 compounds were identified in jujube tincture by GC-MS.2.The raw material extracted by 95%ethanol was used to investigate the effect of heating temperature(60,70,80,90℃),time(1,2,3,4 h)and stage(1,2,3 series)on polysaccharide yield of jujube.The yield was 3.02%and extraction ratio of 3 times reached 98.32%under optimal extraction condition at 80℃ for 2 h.After that,the obtained jujube polysaccharide and amino acid were used for Maillard reaction.Thus,the effect of heating temperature(100,120,140℃)and time(0.5-5 h)on the changes of browning degree,color and pH value of Maillard reaction were investigated.The results showed that with the increased of time,A420 nm,color and pH value were separately increased,rose first down later and increased.Furthermore,bothtemperature and time significantly affected the sensory characteristics of the Maillard reaction products(p<0.01).The volatiles from 120℃ and 140℃ processed samples were more abundant than the 100℃.When processing time was less than 3.5 h,3,6,9,12-tetraoxatetradecan-l-ol,methoxy-acetic acid,ethyl ester and 4,8-dimethyl-undecane were major volatiles.Otherwise,tetradecane and nonadecane were major volatiles.Besides,the optimum extraction conditions was 120℃ for 2.5-3.5 h from the perspective of better sensory characteristics and more abundant volatiles.At last,partial least squares analysis also indicated that the overall preference,aroma strength,aroma persistence,sweetness,roasted fragrant and scorched bitter of products were closely associated with 4,14,13,14,4,14 volatiles,respectively.And the regression models based on these volatiles could also predict the score of overall preference,aroma strength,aroma persistence,sweetness,roasted fragrant and scorched bitter in each sample well.3.The raw material after polysaccharide extracting was used to study NaOH concentration,temperature,time,power and solid-liquid ratio by the value of A272 nm.The results showed that the optimal condition of ultrasonic-assisted extraction was at 1:15 g/mL,70℃,76 W for 40 min and the ratio reached 6.30%.The significance of each factor in a descending order was solid-liquid ratio,temperature,time and power.However,solvent extraction reached its best at 80 ℃ for 40 min and the ratio reached 2.40%.The results showed that the alcohol,water,alkaline can be used to successively extract flavor,polysaccharide,pigment to achieve the full use of jujube resources and the total utilization ratio reached 56.7%. |
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