Properties & Applications of Natural Colored Silk

Silk, a luxurious and versatile natural fiber, has been prized for millennia. While often associated with the creamy white hue of cultivated silk, silk fibers can naturally occur in a range of colors, a phenomenon arising from the pigments incorporated by silkworms during cocoon formation. These natural colors offer unique aesthetic and, in some cases, functional properties, expanding the applications of this already remarkable material. The exploration of naturally colored silk provides a fascinating insight into the intersection of biology, chemistry, and textile science.

1. The formation of colored silk

In December 2008, the world’s first fine-grained silkworm genome map was completed at Southwest University. Through the use of genetically modified methods, the research team also successfully developed China’s first genetically modified new colored cocoon practical silkworm variety, bred a pair of new green cocoon varieties with stable colors, and completed batch reeling and performance identification of cocoon silk. The inheritance of natural colored silk is controlled by the main gene, so that the characteristics of colored cocoon silk can be fixed, creating good conditions for breeding and production.

At present, colored silkworm cocoons are mainly obtained by two methods. One is to use modern breeding technology; the second is to obtain colored cocoons by adding bio-organic pigments to the silkworm.

Using Modern Breeding Techniques to Obtain Color Cocoon Silkworm Varieties

Soochow University transferred genes from the original domestic and foreign species of excellent color cocoon silkworms to high-yield and high-quality white cocoons through genetic recombination, and selected color silkworm cocoon varieties.

Obtaining colorful silkworm cocoons by adding biological organic pigments to silkworms

On the basis of conventional breeding of silkworms, various bio-organic pigments that have been screened and processed are added to artificial feed or mulberry leaves to change the coloring performance of silk glands after nibbling, and present various colors according to different food pigments. Colorful silkworm cocoons. There have been reports on the production of a variety of colored cocoons and their raw silk through the method of improving the varieties of colored silkworm cocoons or the method of adding food pigments at home and abroad. The Silkworm Research Institute of Soochow University has also independently developed color silkworm cocoons with three basic colors of red, yellow and blue as the main color, supplemented by multiple composite colors. Anhui took the lead in realizing the industrialization of artificial feeding and producing colorful silkworm cocoons.

2. The nature of colored silk

The color cocoons of the silkworm mainly include yellow-red cocoons and green cocoons. Yellow-red cocoons include light yellow, golden yellow, orange, flesh, pink, rust and other cocoon colors. Green cocoons include light green, yellow-green, green and so on. Compared with colored cotton, the cocoon color of colored silk is brighter, but raw silk is brighter in yellow and lighter in green; the color is stable after washing, and the color is easily faded in the sun. There are slight differences between individuals and the inner and outer layers of the cocoon. There is no special requirement for the production environment. .

Natural colored silk has a high ability to decompose free radicals. The use of colored silk into sanitary products, care products, underwear or cosmetics has a good skin care effect. Natural yellow silkworm silk and ordinary white silkworm silk have many internal pores and there is a large amount of air in the gaps. Air is a poor conductor of heat. Therefore, the more gaps, the better the warmth retention and the better the fiber flexibility. Natural yellow silkworm silk is a high-quality and porous natural protein fiber, and its flexibility, warmth retention, moisture absorption and release, and air permeability are more excellent.

Anti-ultraviolet ability of colored silk

Natural colored silk has good ultraviolet absorption ability. Domestic scholar Xu Shiqing and others have used ultraviolet rays to irradiate silkworm cocoons for a long time and found that the pupa development and emergence of silkworm moths and their offspring in the cocoons are normal. Severely affected, the emergence of silkworm moths and their offspring are often deformed. Experimental results show that mulberry silk has a good shielding and absorption effect on ultraviolet light (UV-B) with a wavelength of about 280nm, which is easy to induce genetic mutations and cause skin cancer and other carcinogenesis. The transmittance of UV-B is less than 0.5%. The transmittance of A and IUV-C is also less than 2%. Therefore, products produced with natural colored silk as raw materials have good absorption of ultraviolet rays. At the same time, the sericin in colored silk has the characteristics of inhibiting tyrosinase activity, which can effectively inhibit the formation of melanin in the skin, so it can effectively prevent Damage caused by oxidation in the human body caused by environmental pollution.

Antioxidant ability of colored silk

In biological activities, especially in a poor living environment, a variety of active oxygen free radicals will continue to be produced. Because these biological free radicals have a strong oxidizing ability, many biological functional molecules will be destroyed. It will cause certain poison to the body. SOD (Superoxide Dismutase) is an active substance derived from living organisms, which can eliminate harmful substances produced by organisms in the metabolic process, and continuously replenish SO to the human body, which has a special anti-aging effect. The SOD activity of cocoon colored silk is much higher than that of cotton fiber. The SOD activity of green cocoon silk is 30 times higher than that of cotton fiber and nearly 3 times higher than that of white cocoon silk. SOD can remove excess free radicals in the body and protect the body from Free radical poisoning. Therefore, color silk is made into clothes or cosmetics, which has a good skin nourishing effect and is suitable for the needs of the green and healthy consumer market.

Antibacterial ability of colored silk

Carotenoids can protect the body’s proteins and lipids from harm, enhance the activity of the immune system and the ability of phagocytic cells. In addition, carotenoids can effectively prevent other chronic diseases. In the research, it was found that the content of flavonoid pigment and carotenoid B of natural colored silk was higher. The content of flavonoid pigment of yellow silk was 30% higher than that of white silk, and the content of carotenoid was more than 30 times that of white silk. The outer layer of the cocoon silk of spun silk insects has a good antibacterial effect. Because part of the sericin will be retained during silk reeling, the silk also has good antibacterial ability. Among them, the antibacterial effect of colored silk is better, so that the fabric has a better antibacterial effect. Good antibacterial ability. Natural colored silk can inhibit the growth of strains such as Glucococcus aureus and Escherichia coli, and has an inhibitory effect on most strains. Therefore, clothing made from natural colored silk has a good health care effect.

3. Application of colored silk

Colored silk fabric has good flexibility, warmth retention, moisture absorption and release, ventilation, unique ultraviolet absorption function, anti-oxidation, anti-bacterial function, and the pigment of natural color silk is derived from mulberry leaves or self-synthesis in silkworm body, non-toxic harmless. The clothing made of silkworm natural cocoon silk fabric has a good health care effect, is an ideal close-fitting clothing material, and can be made into high-end underwear.

In the field of biomedicine, colored silk, as a biological raw material, is the same protein as the keratin and collagen of the human body. The structure is very similar and has good biological affinity. The fabric has good antibacterial ability and is rich in 18 kinds of amino acids. It can be made into a wound protective film in medicine for the treatment of skin defects such as shallow burns, wounds and plastic skin removal areas, and helps the regeneration and reproduction of skin cells. . It can also regulate the blood circulation and metabolism of the human body, and has special health care functions for keeping the skin clean, enhancing the vitality of skin cells, preventing skin aging and the decline of human white blood cells. In addition, silk can also be used to make medicinal protein.

Domestic researchers have also developed porous silk fibroin membranes with the goal of silk fibroin being used in porous drug carriers, cell culture media, artificial skin and other biomedical fields to improve the air permeability and moisture permeability of ordinary silk fibroin membranes. In addition, the silk fibroin drug slow-release material can adjust the pore size and porosity of the porous silk fibroin membrane.

4. Current status of research and development of colored silk

Applying biological gene recombination technology, introducing silkworm color cocoon genes, using modern breeding technology, combined with traditional breeding techniques such as hybridization, directional selection, etc., natural color cocoon practical silkworm varieties with main economic characteristics reaching the current summer and autumn silkworm varieties level have been selected and developed. Produce original research results such as natural color spun silk opening technology and trial production of natural color silk products. The Key Laboratory of Sericulture of Southwest University has developed a natural colored cocoon silk color fixation technology to solve the problem of oxidation and fading of silkworm cocoons during the silk reeling process, and developed more than 40 natural colors such as red, yellow, blue and pink. Varieties of silkworm cocoons.

5. The development and prospects of colored silk

Natural colored silk products are the products that the cocoon silk industry has been looking forward to in the past century. It is of great significance to reduce environmental pollution, promote human health, and enhance the influence of silk, and has huge development prospects.