In April 2021, Professor Wu Caie from the School of Light Industry and Food, Nanjing Forestry University published a titled”Cocktail enzyme-assisted alkaline extraction and identification of jujube peel pigments” in Food Chemistry (IF=6.306), a TOP journal in the field of food science. Research papers. Master student Shen Dongbei is the first author, Professor Wu Caie is the only corresponding author of this article, and Nanjing Forestry University is the first author.
According to the statistics of the Ministry of Agriculture of the People’s Republic of China in 2018, China is the world’s largest jujube producer with an annual output of 7.36 million tons and a planting area of 3.31 million hectares. Jujube is more and more favored by consumers for its unique flavor and rich nutritional value. Dates can not be stored for more than 10 days at room temperature after they are mature, so 90%of dates are used in processed foods, including fruit plates, beverages, chutneys, kimchi, cakes and breads. Since the jujube skin will undergo lignification after maturity, the jujube skin cannot be directly degraded and absorbed by the human body. This not only causes a waste of resources, but also burdens the environment. In recent years, more and more studies have shown that jujube skin not only contains rich active substances, but also a lot of pigments. However, the traditional pigment extraction method takes too long and the use of a large amount of organic solvents will also bring food safety problems. The team optimized the ratio of compound enzymes (cellulase, pectinase, protease) through response surface, and got the best enzyme ratio. Then, apply the response face to further optimize the enzymatic hydrolysis conditions of the complex enzyme, and obtain the best enzymatic hydrolysis conditions. Under the optimal conditions, the total phenol extraction rate was 9.02 ± 0.63 mg GAE/g, the total flavonoid extraction rate was 11.14 ± 0.45 mg RE/g, and the pigment color a* value was 8.93 ± 0.43. The pigment composition of jujube skin was identified by UPLC-MS/MS, and the main composition of the pigment was found to be p-coumaric acid, (-)-epicatechin, quercetin-3-O-robinobioside, rutin, kaempferol 3-O-robinobioside, quercetin 3 -O-α-L-arabinosyl-(1→2)-α-L-rhamnoside, quercetin 3-O-β-D-xylosyl-(1→2)-α-L-rhamnoside, quercetin. This research not only provides guidance for the industrialized green production of jujube pigment, but also finds the value of reuse for jujube peel waste.
The research work was funded by the National Key Research and Development Project (2019YFD1002300) and the Subei Science and Technology Project (XZ-SZ201929).