Optimization of microwave-assisted extraction and encapsulation of black mulberry rich anthocyanin extract as functional ingredient

Abstract

Black mulberry fruit contains high level of anthocyanins and this compound is known for its beneficial health properties. This fruit is easily perishable and thus, it must be transformed into powder form to preserve its health benefits. The project consists of three objectives. First, to optimise the processes of microwave-assisted extraction, secondly to optimize microwave-assisted encapsulation of black mulberry extract and thirdly to evaluate the storage stability of the encapsulated black mulberry extract and analyse its anti-diabetic property. To obtain the optimised conditions, a response surface methodology was applied. The factors studied for extraction were microwave power (200 – 800 W), extraction time (5 - 15 min), and solid to liquid ratio (0.1 - 1.0 g/ml). The optimised extraction condition was at power of 475.16 W, time of 10.73 min and solid to liquid ratio of 0.59 g/ml. The total anthocyanin content (TAC), 2,2 diphenyl, 1-picrylhydrazyl (DPPH) inhibition and ferric reducing antioxidant properties (FRAP) obtained at this optimized condition were 21.75 mg/g dry basis, 92.4 % inhibition and 0.49 mg Trolox/ml, respectively. For microwave-assisted encapsulation optimisation, the factors studied were the core to wall ratio (0.1 - 0.3 ml/ml), encapsulation time (2 - 4 min) and microwave power (450 - 640 W). Based on the results from the analysis, the optimized encapsulation condition found to be at core to wall ratio of 0.19 ml/ml, power at 450 W and time at 3 min. Under this optimized encapsulation condition, the encapsulated black mulberry extract contained TAC of 23.02 mg/g, with encapsulation efficiency (EE) of 90.08 %, DPPH inhibition of 85.58 %, FRAP of 0.4 mg Trolox/ml and moisture content of 4.31 %. From storage stability study, the best storage condition was at 4 °C where TAC, DPPH and FRAP experienced the lowest degradation (k = 0.0033, 0.0011, 0.0059 mg/day) and highest half-life (t1/2 = 201, 230, 117..5 days). In addition, this study demonstrated that the encapsulated black mulberry extract was capable of inhibiting alpha-glucosidase enzyme and thus, it can be used for preventing or treating diabetes. In conclusion, the results of this study show the potential of black mulberry fruit extract as a functional ingredient.