Development of a new colorimetric method determining the yield of microencapsulation of α-tocopherol

Microencapsulation of α-tocopherol effectively protects α-tocopherol from oxidation and produces high-value-added and long-shelf-stable foods. High-performance liquid chromatography (HPLC) has been applied to measure the yield of microencapsulated α-tocopherol with high accuracy; however, it takes long analysis time. An alternative method is required to determine the yield of microencapsulated α-tocopherol in food industry. A new, easy, and sensitive colorimetric method using 5% cupric acetate pyridine and oleic acid was developed. Correlation coefficient (r) of colorimetric method on α-tocopherol in microencapsulation system and of results between colorimetric method and HPLC were +0.996 and +0.989, respectively, which indicates that this novel colorimetric method can be successfully applied to evaluate the yield of microencapsulated α-tocopherol instead of HPLC. The optimum storage temperature and pH of microencapsulated α-tocopherol for 7-day storage were 25 °C and pH 9, respectively, determined by this new colorimetric method.