Preliminary Study On The Compositions And Effect Of Baking Treatment On Trace Components Of Fresh Reeling Silk

Currently,according to the difference of silk reeling process,silkworm cocoon raw silk is divided into fresh reeling raw silk and dry reeling raw silk.With the progress of science and technology,conomic benefit is better than dry reeling silk,thence fresh reeling silk began to appear and widely used in silk weaving industry.According to many silk enterprises reflection,the weaving property of fresh reeling silk is worse than that of dry reeling silk,silken face is easy to expose quality problems.At present,fresh cocoon reeling factories tend not to clearly mark the fresh reeling silk on the product packaging,which makes it difficult for silk enterprises to identify when purchasing raw silk materials,such situation brings a negative impact on the silk market.Therefore,the study about the identification of fresh reeling silk and dry reeling silk is particularly important.According to the difference of polyphenols components in fresh/dry reeling silk,the fresh reeling silk and dry reeling silk can be identified by high performance liquid chromatography?HPLC?and gas chromatography-mass spectrometry?GC-MS?.Based on the previous research,fresh reeling silk was selected as the research object in this paper.The extract method of trace components of fresh reeling silk was firstly studied through single-factor design and orthogonal test.Then the influence of baking treatment under different conditions on water-soluble and volatile trace components of fresh reeling silk were studied by using the detecting technologies such as HPLC and GC-MS.Also the structure of the corresponding components with different retention times was analyzed through UV and FT-IR spectra and Mass spectrometry afterwards.The main results of the study are as follows.?1?Fresh reeling silk was extracted by ultrasonic assisted extraction technology,the extracts were detected via HPLC and UV spectra.The results showed that the extracts from fresh reeling silk through different ratios of ethanol-water solution had the maximum absorbance at 220 nm and 280 nm in UVspectrograms,which indicated that the extracts were mainly polyphenols.HPLC chromatograms of extracts from fresh reeling silk through different ratios of ethanol-water solution showed that the best extract solvent was pure water.The optimum ultrasonic assisted extract conditions optimized via orthogonal test were as follows:40? of extracting temperature,extracting 90 min,1:25?g/m L?of the liquor ratio.?2?The most essential distinction between fresh reeling silk and dry reeling silk production process is that the former does not need but the latter need to undergo baking at high temperature to kill the pupa,therefore the effect of baking treatment at high temperature on water-soluble trace components of fresh reeling silk.The results showed that baking treatment at high temperature made the mostly water-soluble trace components lost,therefore through detecting the relative contents of water-soluble trace components to make a judgement whether the raw silk undergone the dry heat treatment,which can identify the unknown raw silk is dry or fresh reeling silk.The structure of these thermally unstable compositions was analyzed,which indicated that the compositions were polyphenols orther than flavonoids.?3?The volatile components of fresh/dry reeling silk were analyzed by GC-MS.The research found that,the volatile compounds of dry reeling silk were mainly esters compounds,andthe content of ester was higher,however,the volatile compounds of fresh reeling silk were complex,including amide,saturated hydrocarbons,olefins,esters,aromatics and other compounds.The most significant difference between fresh reeling silk and dry reeling silk was that the volatile extracts from dry reeling silk contained a characteristic component?the retention time was 30 min under GC detecting conditions in this study?the GC chromatograms of extracts from dry reeling silk had a chromatographic peak at the retention time of about 30 min,and the substance was identified as hexacosyl acetate(C₂₈H₅₆O₂)by NIST standard spectral library matching.The substance was a long-chain ester with molecular weight of 424.74,it was confirmed as a product caused by the baking treatment on fresh cocoon material,which should come from the change of structure of trace components in fresh cocoon affected by high temperature.GC-MS can be used to detect whether the unknown samples contain Hexacosyl acetate,which can identify the raw silk sample is dry or fresh reeling silk.The indentification of fresh reeling silk and dry reeling silk is related to the quality of silk products and rational selection of raw materials.The research provides the basises and ideas of two kinds of instrumental analysis for the identification of fresh reeling silk and dry reeling silk,but it still needs to further research.