Developmentandcharacteristicsofoil-Soluble Ethyl Cellulose Microcapsules Containing Tea Polyphenols

Tea Polyphenols (TP) is a natural antioxidant material. It has a rich source. TP has the ability of scavenging free radical, inhibiting bacteria’s growth, preventing disease and other functions. However, TP’ water-soluble properties limited its application in edible oils. In order to change its poor solubility characteristics in edible oil and do not affect its chemical properties in the same time, this study prepared oil-soluble TP microcapsules through solvent-nonsolvent method that take ethyl cellulose (EC) as shell material and sucrose ester as emulsifiers to encapsulate TP. Also this paper described the characteristics of microcapsules. Single factor optimization and orthogonal experiments obtained the optimal preparation microencapsulation process:the viscosity of EC is 9 cpa · s and concentration is 4%; sucrose esters’s HLB value is 5; core to shell ratio is 1:6 and sucrose ester’s concentration is 1%. The encapsulation efficient of TP reached 81.07%. Microcapsules’ particle size distributed between 26.57 to 45.40 μm SEM observed the surface of the microcapsules is irregular shape and its surface is porous that’s relatively dense, which makes the microcapsules release the core easily and core material contact medium (soybean oil) as possible. According to Fourier transform infrared spectroscopy (FTIR) to observe the molecular structure inferred microencapsulation mechanisms:TP took nucleophilic reaction with EC, oxygen atom of carbonyl in sucrose esters joint oxhydryl group in TP or EC through hydrogen bond. Differential thermal scanning method and thermal gravimetric analysis found that that microcapsules experienced four weight loss between 20-500℃ and total weight lost 70.62%. Sharp weight loss of 48.90% occurred between 200-310℃, while in the daily edible oil processing temperature 200℃ or less, the microcapsules have only 3.89% of the weight loss. So microcapsules have high thermostability.The amount of microcapsules used in soybean oil was according to Chinese standard’s requirement (0.2 g/kg) for antioxidant. Investigate the influence of microcapsules to lipid oxidation by simulating high frying temperature and accelerated storage environment. The results showed that in the high temperature environment, microcapsules exhibited strong antioxidant effectiveness, even higher than the artificial antioxidant TBHQ, EC could protect core material in the high temperature. The microcapsules were divided into points through standard sieve mesh, then added in soybean oil and stored at 63℃ dark environment for a month.The microcapsules divided into points (finer) made the contact area of TP and soybean oil increased, the points of microcapsules 400 showed good antioxidant property, but also lower than TBHQ, which can be explained by the actual amount addition of polyphenols:2 mg TP microcapsules’s actual content is 0.2 mg, otherwise the content of TBHQ is 1 mg of, so polyphenols microcapsules have antioxidant property.Validated encapsulated efficient through comparison the differences diode array -HPLC method and spectrophotometry, found HPLC method is 1.123-1.542 times to spectrophotometry. Little difference exsit between the two methods, however spectrophotometry operated simpler, more convenient, costs lower. So spectrophotometry is more useful in practice.