S22 - Session O2 - Standardized evaluation method of tinctorial plant – The case of Punica granatum

Authors: Amelie Braye *, Christine Brunet, Anne de la Sayette

CRITT horticole is one of the pioneers that reintroduced dye plants and optimized dye molecules extraction. Since then, we are searching for new tinctorial plants to expand our knowledge in natural dye and transfer it to our customers. CRITT Horticole has developed a standardized method to assess the color potential of various plants. This method is applied to its own crops or to plants from various geographical origins on the request of international partners. More than 250 different plants or geographical origins have been tested. 1 n Biochemistry n We identify dyeing molecules and ensure that the plant is non-toxic, according to the literature. 2 n Extraction n We perform maceration with a natural solvent, then concentrate liquid extracts by rotary evaporation and then dry in a hot air oven or by freeze drying. The dried extracts are milled and extraction yield is calculated. 3 n Color evaluation, fastness n To characterize the coloring power of the extracts a spectrophotometer analysis is done from 200 to 800 nm. To evaluate the dyeing properties of the extracts, we do a silk dyeing under precise conditions (Alum 10% WOF + Extract 10% WOF). The dyed fabrics are submitted to a lightfastness test using a suntest (Atlas CPS+). 4 n Applications n In addition to textile application, we perform natural hair dyeing and we formulate some basic cosmetic products. 5 - Yields, color results, fastness and conclusions are compared to some other well-developed extracts from our range of extracts. As an example, we received dried pomegranate peel ( Punica granatum) fr om Tunisia, and we were asked to assess if a dyeing extract could be obtained from this material and be used for textile, hair dyeing or cosmetic applications. Extraction yield and lightfastness were satisfactory but the colors obtained both on silk and hair dyeing were disappointing as the color was not very intense. Tannins from Punica granatum could be useful in the hair dyeing industry to make natural dyes such as henna to last longer.