Pigments are the main components of cosmetics, which determine both toxicity and consumer color characteristics. Zn-Al layered double hydroxides intercalated with anionic food dyes are promising pigments. The best sources of dyes for intercalation are natural ones. The most promising are spices. Natural dyes from spices are often biologically active substances. The parameters of samples of Zn-Al (Zn:Al=3:1) hydroxides intercalated with natural food dyes, synthesized in the medium of aqueous tinctures of saffron and safflower, were studied. The crystal structure of the samples was studied by X-ray phase analysis; color characteristics were studied by spectroscopy and calculation of parameters in the CIE L*a*b system. The possibility of synthesizing Zn-Al colored layered double hydroxides intercalated with natural dyes in the medium of saffron and safflower tinctures was shown. X-ray phase analysis showed that both pigment samples were layered double hydroxides with the α-Zn(OH)2 structure. For the pigment intercalated with saffron dye, the phenomenon of partial decomposition of Zn-Al LDH to ZnO during synthesis was revealed. The color characteristics of the samples were studied. Zn-Al LDH pigment synthesized in a saffron tincture had a bright yellow color determined by intercalated saffron carotenoids (crocin and crocetin). It was suggested that safflower dye flavonoids were partially hydrolyzed (red ones - cartamine and cartamidine, and yellow - Safflor Yellow A), which led to the formation of a dark orange-brown color of the sample. The prospects of using Zn-Al LDH intercalated with saffron food dyes as a cosmetic pigment were shown
A simple mechanical method (grinding and sieving) was proposed to separate the composite into carotenoid-enriched and LDH-enriched materials. The method is based on the internal self-abrasion of the composite when grinding solid particles of LDH as grinding bodies. When removing carotenoids in the form of a composite, rapid precipitation of the sediment and ease of filtration under vacuum were found. X-ray diffraction analysis showed that the composite and products of its separation contain X-ray amorphous Zn-Al LDH, an oxide phase, and an amorphous phase of carotenoids. The method of dichloroethane extraction proved the effectiveness of the composite separation process. It was shown that for the optimal amount of Zn-Al LDH, the content of carotenoids in carotenoid-enriched material was 24.4 %, and in LDH-enriched – 4.4 %. For these conditions, it was found that the total yield of carotenoids was 184.3 mg/100 g of pumpkin pulp, of which 155.4 mg/100 g was in the carotenoid-enriched material and 28.9 mg/100 g was in the LDH-enriched material. A hypothesis was expressed regarding the chemical nature of the interaction of carotenoids and LDH in the composite due to π-d interaction. The resulting carotenoid-containing materials can be used as food additives or processed to obtain purified carotenoids.
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