Study On The Extraction Of Pectin From The Peel Of Guanxi Pumelo

Guanxi Pumelo is a kind of well known traditional fruit in Pinghe County, Fujian Province. In 2007, the growing area of Guanxi Pumelo in the whole county accounted for 1/3 of the one in the whole country, with annual yield being up to 630000 tons. For now, the industry of Guanxi Pumelo has become the backbone for the economical development of Pinghe County. More and more pumelo peel waste has turned out to be a problem of waste of natural resourse and environmental pollution while more and more pumelos are yielded year by year. Not too much importance has been laid on this problem, though. The amount of pectin in pumelo peel, especially in the white colored one, is very high. As being researched and revealed in this paper, the total pectin content on dry basis in the yellow colored and white colored peel were 12.10% and 19.52%, respectively. What's more, the quality, for instance, the jelly grade of the pectin extracted from the peel is very high. So, extracting pectin from pumelo peel is of great economical and social significance. In this paper, the producing technology of pectin from the peel of Guanxi Pumelo was detaily studied.Firstly, in terms of the method of extracting pectin from the peel to liquid phase, the technologies of microwave heating extraction and water bath heating extraction were studied, respectively. The best technology of microwave heating extraction of pectin was as follows: size of powder of pumelo peel 60 mesh, extracting temperature 90℃, time of heat preservation 5 min, solid/liquid ratio 1:60, extracting pH 2.0, number of extracting times 1. The resulting extraction yield of pectin on dry basis was 18.22%. The best technology of water bath heating extraction of pectin was as follows: size of powder of pumelo peel 60 mesh, extracting temperature 90℃, time of heat preservation 80 min, solid/liquid ratio 1:60, extracting pH 2.3, number of extracting times 1. The resulting extraction yield of pectin on dry basis was 18.15%.Secondly, in terms of the method of precipitating pectin out of liquid phase, the technologies of alcohol precipitation and alcohol-Al2(SO4)3 combining precipitation were studied, respectively. The best technology of alcohol precipitation of pectin was as follows: proper concentration of pectin solution, concentration and consumption of alcohol for pectin precipitation were chosen so that the concentration of pectin, alcohol and water in the mixed system was 3.7mg/ml, 44% and 56%, respectively, when pectin precipitation was carried out; time of precipitation 30 min, the concentration of alcohol used for washing of the pectin precipitate 40%, volume ratio of the alcohol described above to the original pectin extract 1:5, the number of washing times 1. The resulting yield of pectin precipitate was 98.31%. The best technology of alcohol-Al2(SO4)3 combining precipitation of pectin was as follows: the pctin solution has to be condensed to some degree if the concentration of which is less than 5.9mg/ml and then the pH of which has to be adapted to 4.0 with ammonia; proper concentration and consumption of solution of Al2(SO4)3 and alcohol were chosen so that the concentration of pectin, Al2(SO4)3,alcohol and water in the mixed system was 4.2mg/ml, 0.35mg/ml, 29% and 71%, respectively, when pectin precipitation was carried out; time of pectin precipitation 30 min at room temperature, desalting agent consisting of 1.5% of HCl, 40% of alcohol and 58.5% of water, the ratio of the volume of the desalting agent and the volume of pectin extract was 1:5. The resulting yield of pectin precipitate ex ash was up to 97.43%.Lastly, after the 4 kinds of technologies above were fixed, several pctin products were produced and detaily studied and compared in terms of their physical and chemical property. Thus the influence of different technologies on the quality of pectin products was properly evaluated. The pectin produced by the methods of microwave heating extraction and alcohol precipitation was of high quality while the one produced by the methods of water bath heating extraction and alcohol-Al2(SO4)3 combining precipitation was of somewhat lower quality.