Pilot Study On The Change Of Light Stable Isotopes During The Processes Of Nutrition Transition In Sericulture And Cleaning Of Silks

China is the hometown of silk.The silk has a special historical,cultural and artistic value.The original material of silk production comes from silkworm,one of the economic insects of silk cocooning feeding on mulberry leaves,which was domesticated from raw silkworm in ancient China.As a cultural symbol of Chinese national identity,it has made great contributions to Chinese history in the past 5,000 years and exerted a profound impact on human civilization through the Silk Road.Sericulture and silk weaving originated in China,but there are different views abroad in recent years.So it is imperative to identify the provenance of some important ancient silk.Through pilot study on the change of light stable isotopes during the processes of nutrition transition in sericulture and cleaning of silks,using the light stable isotope technique to explore the internal relationship light stable isotope composition between mulberry,silkworm and silk.The research results can provide basic information for traceability of silk geographical origin.The samples of mulberry leaves from Zhejiang and Sichuan provinces were collected.The mulberry leaves were dried and ground evenly.Mulberry leaf protein and polysaccharides were extracted.The stable isotope composition of mulberry leaf and mulberry leaf nutrients were detected by a TC/EA-IRMS instrument.Silkworms were fed on mulberry leaves from Hangzhou,Zhejiang.Silkworms and their excrements at different ecological stages and the final chrysalises and cocoons were collected to detect the light stable isotope compositions in different growth stages of the silkworms.Finally,the cocoons were degummed in various way to compare the influence of degumming on the light stable isotope compositions.In addition,silk fabrics were dyed by several natural dyes,contaminated in different ways,and then cleaned in a simple and safe way.The samples were detected to figure out the changing tendency of the light stable isotope compositions of in all of those processes.It was found that: there are some differences in the composition of hydrogen stable isotope between mulberry leaves from different areas;the heavier light stable isotopes of hydrogen and oxygen in mulberry leaf protein are relatively depleted to mulberry leaves,while the heavier light stable isotopes of hydrogen and oxygen in mulberry leaf polysaccharides are relatively enriched to mulberry leaves;silkworms may utilize light and heavy stable isotopes at different rate in different ecological stages.It seems a repulsive effect on D and 18 O isotopes happened during the process of feeding and excretion of silkworms,which resulted in the enrichment of D and 18 O isotope in the silkworm cocoon;a significant enrichment in 15 N and 13 C isotopes of the silkworm cocoon is shown,indicating that the process from feeding,excretion and to the final silkworm crusting had a rejection effect on 15 N and 13 C.It reflects that the silkworms may have different utilization efficiency of light and heavy stable isotope in different ecological processes;degumming has certain effect on the hydrogen stable isotopic composition of silkworm cocoon,while it has slight impact on the stable oxygen isotope of silkworm cocoon;the effect of cleaning on the stable isotope composition of silk was related to the type of contaminations and the removal degree of the contaminants.