Study On The Extraction And Application Of The Brown Pigment From Walnut Green Husk

The walnut green husk is the immature walnut epicarp and called pericarpium juglandis in traditional Chinese medicine (TCM) and it has some medicinal value and functional properties. The accumulation of a large number of walnut green husk not only can cause environmental pollution, but also can cause the great waste of resources. In this paper, the extraction technology, physicochemical property, stability,bioactivity and application on food of the pigment from the two kinds of preservation walnut green husk were studied.The natural pigment was extracted from walnut green husk by dilute alkali solution as the optimum extraction agent, the wavelength scanning of the pigment under the ultraviolet spectrophotometer showed 540nm as the detection wavelength.The extraction of the pigment from the walnut green husk was studied with single-factor method and orthogonal method and the results showed that the best concentration of the extraction agent for the pigment of dry walnut green husk is 0.15 mol/L, and the liquid ratio (m/V:g/mL) is 1:100, the temperature for the extraction is 55℃ for 30 min, extracted twice; the best concentration of the extraction agent for the pigment of cold walnut green husk is 0.15 mol/L,the liquid ratio (m/V:g/mL) is 5:100, the temperature for the extraction is 55℃ for 30 min, extracted twice.The physicochemical property and the stability of the pigment from dry and cold walnut green husk are studied. It showed that the pigment of walnut green husk for the two kinds of preservation method were stable to different temperature and common food additives. In addition, Na+, K+and reducing agent had no influence on the pigment, but pH, light, antioxidant and some metal ions had significant impact on the pigment.The composition of the pigment of dry and cold walnut green husk was analyzed. The result indicated that flavonoids content was 0.28 ± 0.02%,0.26 ± 0.02% respectively; polysaccharide content was 11.43 ± 0.08%,3.67 ± 0.07% respectively; protein content was 8.46±0.03%,4.94±0.03%; The crude fat content was 3.17±0.03%,3.28±0.02% respectively; polyphenol content was 0.34±0.01%,0.30±0.01% respectively; tannin content was 14.80 ± 0.05%,13.60±0.04% respectively; ash content was 37.65 ± 0.09%, 34.17±0.08% respectively.The pigment of dry and cold walnut green husk got a further research about the oxidation resistance and the bacteriostatic ability. The antibacterial test showed that the pigment of dry walnut green husk had inhibitory effect on Bacillus subtilis and Staphylococcus aureus and there was no inhibitory effect on Escherichia coli and Salmonella and four species of fungi and that the pigment of cold walnut green husk had inhibitory effect on four species of Bacteria and no inhibitory effect on the common fungi, too. The oxidation resistance test showed that the pigment of dry and cold walnut green husk on scavenging O2-·, DPPH·,·OH had a good effect.The acute toxicity experiment was studied for the pigment and the safety test showed that the maximum tolerated dose is equal to or more than 5000 mg·kg-1·bw and the pigment was safe, nontoxic and non-side effect.Through the comparative study of various aspects of the pigment from walnut green husk and based on the pigment under the condition of non-toxic, the application of the pigment was researched.