| Pectin as a food additive is widely used in food industry,mainly used as thickener,emulsifier,gel,stabilizer and so on.At present,pectin is mainly derived from apple scum and citrus peel.The enterprises that processed aloe into food and health products have not considered the comprehensive utilization of aloe skin,resulting in waste of resources.This research study on the extraction,characterization and antioxidation of pectin from skin of Aloe barbadensis miller,and to explore the superfine grinding,as well as the influence of drying methods of pectin extraction,providing theoretical guidance for the comprehensive utilization of aloe.The main contents and results are as follows:(1)Four different drying methods including hot air drying,drying,microwave drying,vacuum freeze drying were adopted for aloe skin drying,then soluble sugar content was compared.The soluble sugar content was the highest in microwave drying,followed by vacuum freeze-drying and drying,and the lowest is hot air drying.Full factorial design method was used to explore the time and speed of two factors on the effect of aloe skin superfine grinding.In addition,the changes of particle size distribution,chromatic aberration,water holding capacity and water solubility index were studied.With the increase of time and speed,D(3,2)?D(4,3)?D(0.1)?D(0.9)?D(0.5)are decreased,and the specific surface area increased.L,B value of the powder increase with the reduction of the particle size,and L value increase by 57 to 75,B value decrease from 24.47 to 16.9.A value changes small,indicating that the surface is brighter with the decrease of particle size,and the yellow fades.With the decrease of particle size,the water holding capacity decreases,and the water solubility index increases and then decreases.(2)Based on single factor experiment and response surface method,the optimized conditions was extraction from Aloe skin by the acid hydrolysis alcohol precipitation method at temperature of 75?,extraction time of 120 min,extraction pH of 3.5,liquid-solid ratio of 30:1 in the result of experiment when the yield of pectin reached22.593%.In addition,the optimized conditions by enzymic method is:the concentration of enzyme of 0.2%,temperature of 40?,extraction time of 2 h,extraction pH of 5.5,liquid-solid ratio of 20:1 when the yield of pectin reached 21.324%.(3)The physicochemical property of pectin extracted by acid method and enzymic method are compared with national standard.The results show that there is some difference.The results showed that the substance was pectin.But the content of acid-insoluble ash by acid method was 12.72%while pectin by enzymic method was13.06%.It is indicated that there are many impurities in pectin,which need to decolourize and remove protein.The loss on drying of both kinds of pectin was less than 12%.In addition,the molecular weight distribution of the pectin is not a single peak,indicating a low purity.According to the results,the content of in the monosaccharide components:mannose>glucose>galactose.The pectin by enzymic method contains xylose,and pectin by acid method was not checked out.Therefore,improve the quality of pectin is important,and this is also our further study in the future.(4)It was founded that the ability of reducing·OH and ABTS~+·was increased in a range of concentrations.Pectin extracted by acid method has obvious effect on the removal of·OH.The pectin by enzymic method also has a good ABTS~+·scavenging activity,which can be used as a good ABTS~+·scavenger.The pectin from aloe skin had a antioxidant activity,and provides a theoretical basis of the pectin for further research and application. |
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