Method for simultaneously identifying feed silkworm rearing raw silk, mulberry leaf silkworm rearing raw silk and fresh cocoon raw silk / dry cocoon raw silk

Abstract

The invention relates to the technical field of raw silk inspection, in particular to a method for simultaneously identifying feed silkworm rearing raw silk, mulberry leaf silkworm rearing raw silk and fresh cocoon raw silk / dry cocoon raw silk, which comprises the following steps: grinding the feed silkworm rearing raw silk, mulberry leaf silkworm rearing raw silk, fresh cocoon raw silk and dry cocoon raw silk from the same source, adding equal amount of hydrochloric acid after grinding, mixing and reacting, stirring by using a glass rod, and standing for 24 hours; then carrying out ultrasonic treatment and centrifugation, and removing supernate; removing the supernatant, adding the same amount of deionized water, stirring, washing, standing, pouring out the supernatant, repeating for several times, centrifuging, taking the precipitate, drying, grinding and crushing to obtain an extract; and determining the obtained extract by adopting a stable isotope ratio mass spectrometer, and judging the silkworm rearing raw silk of the feed, the silkworm rearing raw silk of the mulberry leaves, the fresh cocoon raw silk and the dried cocoon raw silk according to the N content and the 15N relative content. The method for detecting the total N content and the < 15 > N relative content in the raw silk is reliable, high in recognition rate, visual and reliable in experimental result and high in accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of raw silk inspection, and in particular to a method for simultaneously identifying raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons or dried cocoons. Background Art

[0002] With the continuous progress of science and technology, the traditional silkworm breeding method has also ushered in changes and innovations, resulting in new feed silkworm breeding technology and new fresh cocoon reeling technology. Therefore, the types of silk can be divided into feed silkworm raw silk, mulberry leaf silkworm raw silk, fresh cocoon raw silk and dry cocoon raw silk. The raw silk obtained by silkworms eating feed, cocooning and silk making is called feed silkworm raw silk. On the contrary, the raw silk obtained by silkworms eating mulberry leaves, cocooning and silk making is called mulberry leaf silkworm raw silk. Fresh silkworm cocoons are not dried or boiled at high temperature, but only treated with vacuum hot water penetration and then directly reeled. Raw silk is called fresh silkworm raw silk. On the contrary, fresh silkworm cocoons are reeled after high-temperature drying, storage for a certain period of time, and high-temperature boiling. It is called dry silkworm raw silk. Due to the different processes of reeling fresh silk cocoons and reeling dried silk cocoons, the properties of the two raw silks are different; and the food used for raising silkworms with feed and raising silkworms with mulberry leaves is different, especially the protein nutrients are significantly different, which makes the silk fiber strength of the two raw silks different. At present, these four kinds of raw silk are difficult to distinguish when circulating in the market, making it difficult for silk weaving companies to choose the raw materials they need, which in turn affects the design and production of silk products.

[0003] Application No. CN201510446043.7, a method for quickly distinguishing fresh cocoon raw silk and dried cocoon raw silk, wherein the sample is subjected to HPLC analysis to obtain the HPLC analysis results of the standard and the HPLC analysis results of the sample to be tested respectively; when the HPLC analysis results of the sample to be tested are compared with the HPLC analysis results of the standard, at least one characteristic component peak appears more, the sample to be tested is determined to be fresh cocoon raw silk; otherwise, the sample to be tested is determined to be dried cocoon raw silk. Application No. 201510037780.1, a method for distinguishing fresh cocoon raw silk and dried cocoon raw silk by the gel properties of sericin, wherein fresh cocoon raw silk and dried cocoon raw silk are determined according to the length of gel time. Application No. 201510039141.9, a method for distinguishing fresh cocoon raw silk from dried cocoon raw silk by the solubility characteristics of sericin, which compares the sericin loss rate or sericin solution concentration of fresh cocoon raw silk and dried cocoon raw silk from the same source to judge fresh cocoon raw silk and dried cocoon raw silk. The above identification method can distinguish fresh cocoon raw silk from dried cocoon raw silk, but it cannot effectively distinguish feed silk from mulberry leaf silk. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a method for simultaneously identifying raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons, which can accurately identify raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, raw silk from fresh cocoons and raw silk from dried cocoons.

[0006] (II) Technical solution

[0007] The present invention adopts the following technical solution to solve the above technical problems: a method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons, comprising the following steps:

[0008] 1) Grind 1 portion of raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons, and add equal amounts of hydrochloric acid to the 4 portions of powder after grinding, mix and react for 2-4 hours, and stir with a glass rod every hour; then ultrasonically treat for 1 hour, centrifuge, and remove the supernatant; the concentration of the hydrochloric acid is 0.5-1 mol L-1, and the ratio of the amount of the hydrochloric acid added to the raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons is 60-100:3 mL / g;

[0009] 2) adding an equal amount of deionized water to each of the four portions of liquid after removing the supernatant in step 1), stirring and washing, standing for 0.5 h, pouring off the supernatant, repeating 3 to 4 times, and then centrifuging, taking the precipitate, drying, grinding and crushing to obtain an extract; the ratio of the amount of deionized water added to the four portions of concentrated liquid is 10:1 mL;

[0010] 3) The extract obtained in step 2) is measured by a stable isotope ratio mass spectrometer, and the detection conditions of the stable isotope ratio mass spectrometer are: N mode, oxidation tube temperature 1000°C, carrier gas is helium, flow rate 150mL / min, column temperature 50°C, O2 flow rate 175mL / min, oxygen injection time 3s, reference gas is high-purity N2, and the flow rate is 120mL / min.

[0011] Preferably, the ultrasonic treatment condition in step 1) is: power is 100-450W.

[0012] Preferably, the centrifugal conditions in step 1) and step 2) are: 6000-8000 r / min, time 10-15 min

[0013] Preferably, the drying temperature in step 2) is 40-60° C., and the grinding mesh size is 100-140 meshes.

[0014] Preferably, the stable isotope ratio mass spectrometer is a Thermo Fisher Scientific MAT 253 stable isotope ratio mass spectrometer.

[0015] Preferably, the N isotope ratio of the raw silk grown from feed is in the range of 10.50% to 14.00%; the N isotope ratio of the raw silk grown from mulberry leaves is in the range of 6.00% to 9.50%; 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰; 15 The ratio of N isotope determination ranges from 2.85 to 3.25‰.

[0016] Preferably, the method comprises the following: using the method for analyzing raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons as claimed in any one of claims 1 to 5 based on stable isotopes to treat the sample to be tested, and conducting N and 15 N isotope detection, using the total N content index to distinguish feed silk and mulberry silk, no matter dry cocoon or fresh cocoon silk, feed silk N isotope ratio range of 10.50 ~ 14.00%, mulberry silk N isotope ratio range of 6.00% ~ 9.50%; 15 The content of N isotope is an indicator for distinguishing dry cocoon raw silk from fresh cocoon raw silk. Whether it is bred by feed or mulberry leaves, the content of dry cocoon raw silk is 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰, which is still fresh silk. 15 The ratio of N isotope determination ranges from 2.85 to 3.25‰.

[0017] (III) Beneficial effects

[0018] In summary, the present invention has the following beneficial effects:

[0019] 1. The present invention uses isotope detection technology to detect the total nitrogen content and 15 By measuring and analyzing the relative content of N, raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, raw silk from fresh cocoons and raw silk from dried cocoons can be quickly and effectively identified. This can effectively avoid the phenomenon of selling inferior products as good ones in the raw silk market, maintain market trading order, guide healthy competition, and enable silk weaving companies to accurately select the raw materials they need, thereby improving the design and production of silk products.

[0020] 2. The present invention is based on the total N content in raw silk and 15 The method for detecting the relative content of N is reliable, has a high recognition rate, and the experimental results are intuitive and reliable, with a high accuracy rate. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with data and specific examples.

[0022] Embodiments of the present invention are as follows:

[0023] Example 1: Blind inspection and identification of 1#, 2#, 3# and 4# raw silk samples originating from Huzhou, Zhejiang

[0024] 3g of raw silk samples were taken and ground. After grinding, 80ml of 0.7mol L-1 hydrochloric acid was added to each of the four powders. The mixture was mixed and reacted for 3h. The mixture was stirred with a glass rod every 1h. Then, the mixture was put into an ultrasonic instrument and subjected to ultrasonic treatment at 250W for 1h. Finally, the mixture was put into a centrifuge and subjected to centrifugal treatment at 7000r / min for 13min. After the centrifugation, the supernatant was discarded.

[0025] After removing the supernatant, add 100 ml of deionized water to each of the four portions of liquid, stir and wash, let stand for 0.5 h, pour out the supernatant, repeat 3 times, and then put it into a centrifuge, centrifuge at 7000 r / min for 13 min, pour out the supernatant after the centrifugation, retain the precipitate, and finally put it into an oven at 50°C for drying, and grind it to a particle size of 120 mesh to obtain the extract;

[0026] Test N and 15 N isotope ratio: Weigh 3 mg of the sample prepared above and put it into a tin cup, put it into the instrument for detection, and record the data. The results are shown in Table 1;

[0027] The detection conditions of the stable isotope ratio mass spectrometer are as follows: N mode, oxidation tube temperature 1000 °C, carrier gas is helium with a flow rate of 150 mL / min, column temperature 50 °C, O2 flow rate 175 mL / min, oxygen injection time 3 s, and reference gas is high-purity N2 with a flow rate of 120 mL / min.

[0028] The analysis results are as follows: Table 1 shows the N and 15 The results of N isotope test showed that the total N content (%) of the dried cocoon silk from feed No. 1 was 13.78. 15 The N (‰) content is 2.45; the total N (%) content of fresh cocoon silk from 2# feed is 10.82, 15 The N (‰) content is 3.12; the total N (%) content of 3# mulberry leaf dried cocoon silk is 8.95, 15 The total N (‰) content of 4# mulberry leaf fresh cocoon silk is 9.25. 15 The content of N (‰) is 2.89. Therefore, the ratio of N isotope determination of feed silk is in the range of 10.50-14.00% (regardless of dry cocoon or fresh cocoon raw silk), and the ratio of N isotope determination of mulberry leaf silk is in the range of 6.00%-9.50% (regardless of dry cocoon or fresh cocoon raw silk). 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰ (whether it is bred from feed or ordinary mulberry leaves), or from fresh cocoon raw silk. 15The ratio range of N isotope determination is 2.85~3.25‰ (regardless of whether it is silk grown by feed or ordinary mulberry leaves). It can be judged that No. 1# and No. 2# are silk grown by feed, and No. 3# and No. 4# are silk grown by mulberry leaves; No. 1# and No. 3# are dry cocoon raw silk, and No. 2# and No. 4# are fresh cocoon raw silk.

[0029] At the same time, the experiment was repeated many times and the results were the same.

[0030] Test results of 4 samples:

[0031]

[0032]

[0033] Table 1

[0034] Example 2: 5#, 6#, 7# and 8# raw silk samples originating from Changsha, Hunan Province were blindly tested and identified; the testing was carried out according to the method described in Example 1.

[0035] The analysis results are as follows: Table 2 shows the N and 15 The results of N isotope test showed that the total N content (%) of the dried cocoon silk from 5# feed was 13.29. 15 The total N (‰) content of fresh cocoon silk from 6# feed is 11.16. 15 The N content of 7# mulberry leaf dried cocoon silk is 6.45. 15 The total N (‰) content of 8# mulberry leaf fresh cocoon silk is 6.12. 15 The content of N (‰) is 2.93. Therefore, the ratio of N isotope determination of feed silk is in the range of 10.50-14.00% (regardless of dry cocoon or fresh cocoon raw silk), and the ratio of N isotope determination of mulberry leaf silk is in the range of 6.00%-9.50% (regardless of dry cocoon or fresh cocoon raw silk). 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰ (whether it is bred from feed or ordinary mulberry leaves), or from fresh cocoon raw silk. 15 The ratio range of N isotope determination is 2.85~3.25‰ (regardless of whether it is silk grown from feed or ordinary mulberry leaves). It can be judged that No. 5 and No. 6 are silk grown from feed, and No. 7 and No. 8 are silk grown from mulberry leaves; No. 5 and No. 7 are dry cocoon raw silk, and No. 6 and No. 8 are fresh cocoon raw silk.

[0036] At the same time, the experiment was repeated many times and the results were the same.

[0037] Test results of 4 samples:

[0038] Sample No. N(％) <![CDATA[ 15 N(‰)]]> 5# Feed Dry Silk Cocoon 13.29 2.26 6# Feed Fresh Silk 11.16 3.08 7# Mulberry Leaf Dry Silk 6.45 2.67 8# Mulberry Leaf Fresh Silk 6.12 2.93

[0039] Table 2

[0040] Example 3: Blind inspection and identification of 9#, 10#, 11# and 12# raw silk samples originating from Tongliang, Chongqing; detection according to the method described in Example 1

[0041] The analysis results are as follows: Table 3 shows the N and 15 The results of N isotope test showed that the total N content (%) of the dried cocoon silk from 9# feed was 13.56. 15 The N (‰) content is 2.34; the total N (%) content of 10# feed fresh cocoon silk is 11.02, 15 The N content of 11# mulberry leaf dried cocoon silk is 7.56. 15 The total N (‰) content of 12# mulberry leaf fresh cocoon silk is 8.23. 15 The content of N (‰) is 2.90. Therefore, the ratio of N isotope determination of feed silk is in the range of 10.50-14.00% (regardless of dry cocoon or fresh cocoon raw silk), and the ratio of N isotope determination of mulberry leaf silk is in the range of 6.00%-9.50% (regardless of dry cocoon or fresh cocoon raw silk). 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰ (whether it is bred from feed or ordinary mulberry leaves), or from fresh cocoon raw silk. 15 The ratio range of N isotope determination is 2.85~3.25‰ (regardless of whether it is silk grown from feed or ordinary mulberry leaves). It can be judged that No. 9# and No. 10# are silk grown from feed, and No. 11# and No. 12# are silk grown from mulberry leaves; No. 9# and No. 11 are dry cocoon raw silk, and No. 10# and No. 12# are fresh cocoon raw silk.

[0042] At the same time, the experiment was repeated many times and the results were the same.

[0043] Test results of 4 samples:

[0044] Sample No. N(％) <![CDATA[ 15 N(‰)]]> 9# Feed Dry Silk Cocoon 13.56 2.34 10# Feed Fresh Silk 11.02 3.11 11# Mulberry Leaf Dried Silk Cocoon 7.56 2.51 12# Mulberry Leaf Fresh Silk 8.23 2.90

[0045] Table 3

[0046] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for simultaneously identifying raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons, characterized in that: The steps are as follows: 1) Grind 1 portion of raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons, and add equal amounts of hydrochloric acid to the 4 portions of powder after grinding, mix and react for 2-4 hours, and stir with a glass rod every hour; then ultrasonically treat for 1 hour, centrifuge, and remove the supernatant; the concentration of the hydrochloric acid is 0.5-1 mol L-1, and the ratio of the amount of the hydrochloric acid added to the raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons is 60-100:3 mL / g; 2) adding an equal amount of deionized water to each of the four portions of liquid after removing the supernatant in step 1), stirring and washing, standing for 0.5 h, pouring off the supernatant, repeating 3 to 4 times, and then centrifuging, taking the precipitate, drying, grinding and crushing to obtain an extract; the ratio of the amount of deionized water added to the four portions of concentrated liquid is 10:1 mL; 3) The extract obtained in step 2) is measured by a stable isotope ratio mass spectrometer, and the detection conditions of the stable isotope ratio mass spectrometer are: N mode, oxidation tube temperature 1000°C, carrier gas is helium, flow rate 150mL / min, column temperature 50°C, O2 flow rate 175mL / min, oxygen injection time 3s, reference gas is high-purity N2, and the flow rate is 120mL / min.

2. The method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons according to claim 1, characterized in that: Step 1) The ultrasonic treatment condition is: power is 100-450W.

3. The method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons according to claim 1, characterized in that: The centrifugal conditions of step 1) and step 2) are: 6000-8000 r / min, time 10-15 min.

4. The method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons according to claim 1, characterized in that: Step 2) The drying temperature is 40-60° C. and the grinding mesh size is 100-140 meshes.

5. The method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons according to claim 1, characterized in that: The stable isotope ratio mass spectrometer is the American Thermo Fisher MAT 253 stable isotope ratio mass spectrometer.

6. The method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons according to claim 1, characterized in that: The N isotope ratio of the raw silk produced by feed is in the range of 10.50% to 14.00%; the N isotope ratio of the raw silk produced by mulberry leaves is in the range of 6.00% to 9.50%; 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰; 15 The ratio of N isotope determination ranges from 2.85 to 3.25‰.

7. The method for simultaneously identifying raw silk from silkworms raised with feed, raw silk from silkworms raised with mulberry leaves, and raw silk from fresh cocoons / dried cocoons according to claim 1, characterized in that: The method comprises the following steps: using the method for analyzing raw silk from silkworms raised on feed, raw silk from silkworms raised on mulberry leaves, and raw silk from fresh cocoons / dried cocoons based on stable isotopes as described in any one of claims 1 to 6 to treat the sample to be tested, and conducting N and 15 N isotope detection, using the total N content index to distinguish feed silk and mulberry silk, no matter dry cocoon or fresh cocoon silk, feed silk N isotope ratio range of 10.50 ~ 14.00%, mulberry silk N isotope ratio range of 6.00% ~ 9.50%; 15 The content of N isotope is an indicator for distinguishing dry cocoon raw silk from fresh cocoon raw silk. Whether it is bred by feed or mulberry leaves, the content of dry cocoon raw silk is 15 The ratio of N isotope determination ranges from 2.20 to 2.75‰, which is still fresh silk. 15 The ratio of N isotope determination ranges from 2.85 to 3.25‰.

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