Effect of Drying Method on Physicochemical Properties of Lemon Pectin

The objective of this study was to explore physicochemical properties of lemon pectin dried by different methods. Dry lemon pectin was prepared from dry lemon peel under the same extraction and concentration conditions,dried by different drying methods including hot air drying,vacuum drying,freeze drying and spray drying. Index such as lemon pectin yield,galacturonic acid content,esterification degree,drying energy consumption,rehydration ratio,gelling strength and structure of dried lemon pectin among different drying methods were measured,and variation coefficient weight method was used to determine their comprehensive scores to find the optimal drying method. Results showed that the content of galacturonic acid in all pectins reached the national standard of 65%;and the esterification degree was higher than 50%,indicating that lemon pectin was a kind of high methoxyl pectin. Fourier Transform Infrared Spectrometry(FTIR)showed that pectins from different drying methods had pectin characteristic functional groups,indicating that the drying methods adopted would not affect the pectin structure. Different drying methods had a significant impact on all parameters involved(P<0.05),and the one with highest comprehensive score was vacuum drying at 60℃,which pectin yield,galacturonic acid,esterification degree,drying energy consumption,rehydration ratio and gelling strength were 17.84%,82.44%,73.16%,28.13 kJ/g,5.36% and 149.71 g,respectively. Vacuum drying equipment is relatively simple with low energy consumption and good quality of pectin,which is of great significance to the research of lemon pectin industry.