Using Konjac Glucomannan Stabilize Curcumin Nanoemulsion And Slow Down Its Nutrient Release During In Vitro Digestion

Curcumin is a lipophilic polyphenol bioactive substance,it has been reported to have anti-tumour,anti-oxidant properties and other functions.However curcumin is sensitive to pH,temperature and light,and has low bioaccessibility which limit its application in food industry.Micro and nano delivery systems can protect,transport and release curcumin and increase its the bioaccessibility.Oil-in-water emulsion are one of the most widely studied micro-nano delivery system.Konjac glucomannan(KGM)is a polysaccharide derived from konjac with the function of assisting blood fat reduction.Using whey protein as a model emulsifier and corn oil as a carrier oil,a nanoemulsion carrying curcumin was prepared,and KGM was added to achieve the purpose of stabilizing the emulsion and controlling the release of curcumin.The optimum conditions for the formation of curcumin riched WPI emulsion containing KGM are 1%(w/w)WPI concentration and 0.3%(w/w)KGM addition.At this time,the emulsion has a smaller particle size and a significantly increased viscosity.The thermal stability of the emulsion after adding KGM was significantly increased.After 90 minutes of heat treatment,the curcumin content in the WPI emulsion containing KGM was 20% higher than that of the emulsion without KGM.Digestion behaviors of two emulsions were studied using an in vitro digestion model containing the gastric-intestinal stage.The addition of KGM inhibits the hydrolysis of proteins in the emulsion,and the hydrolysis rate of ?-lactoglobulin is reduced by 20%.The addition of KGM significantly reduces free fatty acid release rate at the later period of the small intestinal digestion.Because the digestion products of oil will cover the KGM backbone to form agglomerates to produce steric hindrance,hinder the entry of lipase,slow the release of fatty acids.After 2 hours of digestion,the bioaccessibility of curcumin in WPI emulsion containing KGM was 30%,while the bioaccessibility of curcumin in WPI emulsion without KGM was 41.2%.The emulsion can effectively protect curcumin in the gastrointestinal tract,and only 20% of curcumin break down during in vitro digestion.Experiment results show that the addition of KGM can effectively control the release rate of free fatty acid,releasing the bioactive compounds slowly and continuously.