Optimization of ultrasound-assisted extraction of melanin from Auricularia auricula fruit bodies

Abstract

Abstract In this paper, ultrasound-assisted extraction (UAE) conditions of natural melanin from dried fruit bodies of Auricularia auricula (A. auricula) were investigated. By single-factor experiments, ultrasound power was determined at 250 W and the other factors (temperature, liquid–solid ratio and duration) were chosen to further optimize extraction conditions using response surface methodology (RSM). The Box–Behnken experimental results showed the optimum extraction conditions as follows: a temperature of 63 °C, a liquid–solid ratio of 43 mL/g and a duration of 36 min. Under these conditions, two extractions sufficiently reached the maximal melanin yield (120.05 mg/100 g). Light absorbance, solubility and redox properties of the melanin extracted from A. auricula were similar to those of the typical melanin. Industrial relevance Auricularia auricula (A. auricula) has been used as food and drug in China for a long time. The annual production of A. auricula in China was 1.44 million tons in 2007 ( http://www.mushroommarket.net/news/show.asp?id=19769 ). However, most of this precious macro-fungus product was only used as cuisine materials, and many of its functional components, such as melanin, a healthful natural food colorant, were not fully developed and employed. In this paper, ultrasound-assisted extraction (UAE) was applied to melanin extraction from A. auricula fruit bodies to improve the extraction efficiency. This research helps to develop a new and economical method of extracting natural melanin and to fully use this edible mushroom.