Study On Extraction Technique Of Low Methoxy Pectin From Silkworm Excrement

Pectin, as natural linear polysaccharides with a high-molecular weight, is contained in cell walls of many high plants. The percentage of pectin consisted in silkworm excrement is 10-12% (by weight), and the pectin extracting from silkworm excrement is an excellent natural pectin with the low content of methoxy groups. It shows a great effect in treatment of diarrhea, glycuresis, cancer and slimming exercise. In the recent years, the production of pectin is in a great increase in the world, because its widely applications to many industries of pharmacy, food making, cosmetics, papermaking, and fine chemicals and so on. However, the research level of pectin extraction and its commercial production in China is still in the beginning stage. Due to fewer pectin manufacturers in China, the neediness of industrial pectin relies on import from abroad. Planting mulberry and sericulture is a traditional branch of social productions in China, in which millions tons of silkworm excrement are produced per year. Obviously, this situation makes a great waste of social resource and serious environmental pollution.In this paper, a method of solution extracting pectin from silkworm excrement by means of the acid extraction and then the molysite precipitation was presented. Depending on the technical process of extractions, such as material pretreatments, acid extraction, discoloration, molysite precipitation, watering and drying, the quality and yield in percentage of the obtained pectin were different widely. To determinethe influence of each parameter in the process, we have used eight different parameters in our experimental work listed as follows: the ratio of extracting liquid content to solid weight, the acid concentration of extracting liquid, the extracting time, the extracting temperature, the amount of molysite, pH used in the precipitation, the amount of active carbon, the proportion of deferrization agent. First of all, a single parameter experiment was designed to study the influence of each single parameter. However, the nonlinear effect between such factors was unknown at all, so a further research was provided based on an orthogonal experiment adopting orthogonal table [L9(34)] and [L16(45)], according to which we could obtain the optimum conditions after analyzing and checking the data using the method of Back-propagation neural network(BP). The optimum parameters obtained in such a way were as following: the bath proportion 1.5-2.0, the extracting time 60~90min, the extracting temperature 85~95C, the amount of molysite solution 8ml(approximately 0.4%), pH of the liquid bath in the precipitation 3.5, deferrization agent 1:6, discoloration with active carbon at 60 C, 1h . The quality of pectin obtained in the experiment was considered by the low content of methoxy group in the sample, which could be measured experimentally. The experimental content of methoxy groups was 6.18% for the sample of pectin obtainedin this way. This work is of great necessity in an efficient use of agricultural waste material such as silkworm excrement. It will be useful to apply the results of this work to a large-scale industrial process in both economical and social benefits.