GB/T 45294-2025Code of practice for silk quality evaluation of silkworm cocoons (English PDF)

1 Scope

This document establishes the procedure for evaluating the silk quality of mulberry silkworm cocoons and sets out technical requirements for the preparation of the cocoon sample, floss removal and cocoon sorting, cocoon cooking, the reelability test, the neatness and cleanness tests, data processing, grading and the writing of the test report.

It applies to the evaluation of small-lot cocoon samples.

2 Normative references

The content of the following documents constitutes indispensable provisions of this document through normative reference in the text. For dated references, only the version corresponding to that date applies to this document; for undated references, the latest version, including all amendments, applies.

GB/T 1798 Test methods for raw silk; GB/T 8170 Rules for rounding off of numerical values and expression and judgement of limiting values; GB/T 9111 Test methods for mulberry dried cocoons; GB/T 9176 Mulberry dried cocoons; GB/T 15268 Mulberry fresh cocoons.

3 Terms and definitions

No terms and definitions are needed in this document.

4 Evaluation procedure

The procedure for evaluating the silk quality of mulberry silkworm cocoons is shown in Figure 1, entitled Flow chart of the procedure for evaluating the silk quality of mulberry silkworm cocoons.

5 Preparation of the cocoon sample

5.1 Numbering of the sample. A test number shall be written for each cocoon sample to be tested, and the number tag shall be tied beside the mouth of the bag.

5.2 Check weighing of the sample. The requirements are as follows: a) weighing instrument: range 1 000 g, scale interval 0.1 g; b) weighing: weigh the mass of the cocoon sample to one decimal place and enter it in the corresponding check-weight column.

5.3 Drying of the sample. Carry this out in accordance with the relevant provisions of GB/T 15268.

6 Floss removal and cocoon sorting

6.1 Floss removal. Remove the floss with a floss-removing machine or by hand, keeping the bare cocoons and the floss separate.

6.2 Sorting inspection. 6.2.1 Equipment. The equipment for the sorting inspection comprises: a) a sorting table; b) a weighing instrument with a range of 1 000 g and a scale interval of 0.1 g; c) a cocoon counter. 6.2.2 Method of operation. In accordance with GB/T 9111, sort out the inferior cocoons, weigh the mass of the reelable cocoons, the inferior cocoons and the floss, and calculate the reelable cocoon percentage. 6.2.3 Operating requirements. Carry these out in accordance with the relevant provisions of GB/T 9111 and GB/T 15268. 6.2.4 Division of the test cocoons into zones. Divide them by the equal-number, equal-mass method according to the quantity of the sample, as follows: a) for a sample of 80 cocoons, take 50 cocoons for the reelability test and 20 cocoons for the neatness test; b) for a sample of 400 cocoons or more, or a sample of 1 kg, divide it equally into 2 zones, with 100 cocoons per zone for the reelability test, the remaining sample, not more than 500 g, being used for the neatness and cleanness tests.

7 Cocoon cooking

7.1 Equipment. Cocoon cooking apparatus, comprising the cooking pan, the penetration vessel, the water-absorption trough and the like.

7.2 Process conditions. The cooking process shall be set sensibly according to the quality of the cocoons and of the water so that proper cooking is obtained. Cocoon cooking shall meet the following conditions: a) high-temperature penetration: 98.5 plus or minus 1.5 degrees C; b) low-temperature water absorption: 60 plus or minus 5 degrees C; c) cooking-through temperature: 99 plus or minus 1 degrees C; d) temperature of the bucket bath: 40 plus or minus 3 degrees C; e) water quality: total hardness below 1.5 mmol/L and total alkalinity below 1.5 mmol/L.

7.3 Method of operation. Load each zone or sample separately into a cooking basket or bag, carry out high-temperature penetration for about 1 min and low-temperature water absorption for 10 min to 15 min, then cook the cocoons for a further 1 min to 1.5 min, take them out, tip them into the cocoon bucket and send them to the reeling machine.

8 Reelability test

8.1 Equipment. A sitting reeling machine with a stable and adjustable reel speed.

8.2 Process conditions. The process conditions for the reelability test are as follows: a) reel speed: 96 plus or minus 3.2 m/min; b) bath temperature: the reeling bath at 36 plus or minus 2 degrees C and the brushing bath at 84 plus or minus 2 degrees C; c) number of ends: 3 ends for a 50-cocoon test and 6 ends for a 100-cocoon test; d) number of cocoons per end: 8; e) pupa-skin percentage, that is the mass of the pupa skin as a percentage of the mass of the whole cocoon: 2.4 % to 2.8 % for spring cocoons and 2.8 % to 3.2 % for summer and autumn cocoons.

8.3 Method of operation. The method of operation for the reelability test is as follows: a) the 100-cocoon reelability test on the two zones is carried out by two reelers working as a pair; b) after the ends have been picked up, count the cocoons with an end and those without an end and check the number of test cocoons; c) start the ends to the prescribed number of ends and the prescribed number of cocoons per end; before starting, turn back 5 revolutions and set the number of cocoons per end exactly, then divide the ends and start the reels; in the 50-cocoon reelability test all the reels are started at once, whereas in the 100-cocoon reelability test 4 edge reels may be started first and 2 more added in turn until all are running; d) after starting, keep to the number of cocoons per end, feeding new and thin cocoons evenly and adding an end before pinching one off; avoid discarded silk and looped waste silk, and if there is not time to feed an end the reel may be stopped; e) when a cocoon has been reeled down to the point where the pupa skin wrinkles and is about to break, pinch it off deliberately; f) find the ends by hand; g) when the cocoons fed to an end are nearly used up, combine the ends, the first started being the first combined, combining them one after another, and when the last end can no longer hold 8 cocoons per end stop reeling, mark it properly and take the reel down; h) during the reelability test, measure the reel speed once a day, taking the second small reel from the left or right side as the measuring position.

8.4 Rules. If inferior cocoons are found during reeling to have been missed in sorting, the reelable cocoon percentage and the number of test cocoons shall be adjusted again. Cocoons that become over-cooked, cocoons pierced during brushing and cocoons left over from reeling that arise in the course of reeling shall not be deducted from the number or the mass of the test cocoons of that zone.

8.5 Determination of dropped-end cocoons. Carry this out in accordance with the relevant provisions of GB/T 9111.

8.6 Classification of the cocoons left after reeling. Carry this out in accordance with the relevant provisions of GB/T 15268.

9 Re-reeling (determination of silk length)

9.1 Equipment. A re-reeling machine fitted with an automatic break-stop device and a counter, with a reel circumference of 1.5 plus or minus 0.005 m.

9.2 Process conditions. The process conditions for re-reeling are as follows: a) reel speed: 230 plus or minus 20 m/min; b) temperature of the machine chamber: 40 plus or minus 4 degrees C.

9.3 Rules. The rules for re-reeling are as follows: a) the circumference shall be taken as the outer circumference of the skein measured after re-reeling; b) in the determination of silk length, waste silk discarded from small skeins whose end cannot be found shall be weighed separately and added to the mass of the skein, and the raw silk length shall be converted accordingly.

10 Conditioned weight test

10.1 Equipment. The equipment for the conditioned weight test comprises: a) an electronic balance with a maximum range of 1 kg and a scale interval of 0.01 g; b) an eight-basket drying oven.

10.2 Rules. The rules for the conditioned weight test are as follows: a) drying temperature: 140 plus or minus 2 degrees C; b) drying time: 2.0 h to 2.5 h; c) interval between the two weighings: 10 min; d) permitted difference between the two weighings: less than 0.05 %.

10.3 Method of operation. The method of operation for the conditioned weight test is as follows: a) place the silk test samples in the respective baskets of the eight-basket oven and dry them at the prescribed drying temperature to constant dry mass; b) switch off the fan, wait 1 min and then begin weighing; if the difference between the two successive weighings is within the permitted tolerance, record the second mass.

11 Neatness and cleanness tests

11.1 Reeling. 11.1.1 Equipment. As in 8.1. 11.1.2 Process conditions. The reeling process conditions are as follows: a) reel speed: 96 plus or minus 3.2 m/min; b) bath temperature: the reeling bath at 36 plus or minus 2 degrees C and the brushing bath at 84 plus or minus 2 degrees C; c) number of ends: 2 ends for the 20-cocoon test and 10 ends for the other tests; d) number of cocoons per end: 8 for the 20-cocoon test, and for the other tests a number set to give a raw silk size of 21 dtex to 26 dtex, that is 19 den to 23 den.

11.2 Method of operation. 11.2.1 The 20-cocoon neatness test. After 2 ends have been reeled with 8 cocoons each, the remaining 4 cocoons are wound at the same time at the other end of the sitting reeling machine, so that the number of cocoons per end can be made up and the outer, middle and inner layers of the sample cocoons stay consistent.

11.2 Method of operation (continued). 11.2.2 Tests on the other cocoon samples. a) Follow the process rules, keep the number of cocoons per end exact and feed new and thin cocoons evenly; the treatment of the pupa skin is the same as in the reelability test, and where reelability is particularly poor and the number of cocoons per end cannot be kept, some reels may be stopped. b) When the new cocoons are nearly used up and the ends can no longer meet the normal cocoon-feeding requirement, begin combining the ends from left to right until the last end can no longer hold the number of cocoons per end. c) When reeling is finished, keep the 10 small reels separate; re-reel every 5 small reels into one large skein, making two skeins in all, one for the neatness and cleanness tests and the other kept in reserve.

11.2 Method of operation (continued). 11.2.3 Testing. 11.2.3.1 The 20-cocoon neatness test. Wind the silk from the small reel that has been taken down directly onto the black board and apply the scoring method specified in GB/T 1798. 11.2.3.2 Tests on the other cocoon samples. Carry these out in accordance with the relevant provisions of GB/T 1798.

12 Data processing

12.1 Original data. The units of measurement and the number of significant decimal places shall be as specified in GB/T 9111.

12.2 Compilation of the data. An original test sheet shall be filled in for the test of every item under each sample number, and it serves as the basis for calculating the results. The data on the original test sheets shall be checked and the individual test items calculated.

12.3 Calculation of the results. Carry this out in accordance with the relevant provisions of GB/T 9111 and GB/T 15268.

12.4 Rounding of values. Carry this out in accordance with GB/T 8170.

13 Grading in the evaluation of cocoon silk quality

Carry this out in accordance with the relevant provisions of GB/T 9176.

14 Test report

A test report shall be issued on the basis of the results of the individual test items.