| Sericulture is quite well developed in China, merely in GuangXi province, millions of tons of silkworm excrement produced every year. However, silkworm excrements were surveyed to lack utilizations, and much worse, they are carelessly disposed which results in sever environment pollution. Furthermore, bacteria and viruses caused by silkworm excrement will bring damages to silkworm in turn, which was surely to cause problems to sericulture. While there are many useful components in silkworm excrement, of which the extraction out of useful compounds could increase the added value of sericulture and the income of sericulture’s, and at the same time does good for the environment, but also guarantee a health and sustainable development of sericulture.Traditional extraction of pectin from silkworm excrement faces such problems as low yield, bad quality and filtration difficulties. In current article, a new process for silkworm excrement integrated utilization was proposed that is pectin extraction and following preparation of sodium zinc chlorophyll. And by this process, pectin was obtained in proved yield and with little pigment in the pectin, which vastly facilitated the following effective decoloration by macroreticular resin. In the process of pectin extraction, chlorophyll turned to phaeophytin with the porphyrin ring unbroken. Through the processes of zincing, saponification and basification, sodium zinc chlorophyll can be prepared with relative good stability. Some leaf proteins in silkworm excrement can also be extracted.(1) Extract pectin from silkworm excrement using diluted sulfuric acid. Through signal factor and orthogonal experiments indicate that the optimal extraction conditions were as follows:H2SO40.6vv%, reaction temperature70℃, solid-liquid ratio1:25, extraction time80min. Under the optimum conditions,2.63g pectin can be obtained from per20.0g silkworm excrement in a yield of13.1%.(2) The decoloration efficiencies of macroreticular resin X-5, D-101, H-103, HPD-100and S-8were studied, and S-8showed the best performance. The best decoloration conditions were obtained as follows:decolorization time1h,10mL of resin per100mL extraction liquid, decolorization temperature50℃, removal rate of pigment peaked at83.1%.(3) Preparation of sodium zinc chlorophyll from pectin extracted from silkworm excrement. The influences of the volume of ethanol, extraction time, the volume of zinc chloride et. on the yield of product were investigated, and the optimal conditions were obtained as follows:the volume of ethanol300mL, extraction temperature60℃, extraction time1h, the volume of zinc chloride4mL, zincing temperature60℃, zincing time30min. Under the optimum conditions, product was gained0.227g per20.0g silkworm excrement in a yield of1.13%. The UV spectrums showed that there were two singlets characteristic absorption peaks at411,644nm respectively, and the peak at411nm is exclusive to the product.(4) The stability of sodium zinc chlorophyll was studied. The results indicate that:it should be stored in dark and avoid of redox compounds; it was observed with good stability while the storage temperature was below100℃even under neutral and weakly basic environment; common food additive such as salt, starch, glucose, almost showed no influence on the stability of product.(5) Leaf protein was extracted from the waste residue of the first two products. Through signal factor and orthogonal experiments, the optimal extraction conditions were as follows:extraction time6h, NaOH0.4wt%, solid-liquid ratiol:15, reaction temperature60℃. Under the optimum conditions, leaf protein was obtained1.21g per10.0g waste residue in a yield of12.1%with protein content27.3%. |
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