Optimization of Extraction Conditions of Melanin from Liquidambar formosana Hance and Its Dyeing Characteristic on Glutinous Rice

PurposeTo optimize the extraction process of melanin from Liquidambar formosana Hance, and to study the apparent performance, sensory quality and antioxidant activity of dyed glutinous rice.

MethodThe melanin from L. formosana from Yunnan was optimized by one-factor-at-a-time method and response surface methodology, the melanin was used to dye glutinous rice, and the sensory quality, antioxidant activity and microstructure changes after dyeing were discussed.

ResultsThe best conditions were as follows: the extraction temperature was 70 ℃, the extraction time was 6 hours, the ratio of solid to liquid was 1∶50 (g/mL). Antioxidant studies showed that melanin had strong antioxidant activity, and the antioxidant activity of glutinous rice was extremely significantly increased after dyeing (P<0.001). However, the sensory score of dyed glutinous rice was significantly lower than that of white glutinous rice (P<0.05). The scanning electron microscope (SEM) results showed that the starch grains interact with melanin, resulting in an obvious increase in the size of starch grains, the changes of morphological. Meanwhile the gelatinization degree of dyed glutinous rice was lower than that of undyed glutinous rice.

ConclusionThis study laid a foundation for the development and utilization of the L. formosana and the industrialization of functional color rice.