Study on Optimization of Ultrasonic Extraction Technology, Stability and Antioxidation of Melanoidin from Black Garlic

Using black garlic as raw material, the melanoidin in black garlic was extracted by ultrasonic method, and the extraction conditions were optimized. On the basis of the single factor experiments, the volume fraction of ethanol, the ratio of material to liquid, the ultrasonic time and the ultrasonic temperature were selected to optimize the optimum extraction process by orthogonal experiments. At the same time, the stability and antioxidant activity of black garlic melanoidin were studied. The results showed that the optimum technological parameters for the extraction of melanoidin from black garlic by ultrasonic method were as follows: The volume fraction of ethanol was 10%, the ratio of material to liquid was 1:7, the ultrasonic time was 40 min, and the ultrasonic temperature was 70 ℃. Under these conditions, the yield was 3.465%. The results of stability study showed that when the temperature was higher than 50 ℃, the stability of melanoidin was not good, while under the conditions of −15 ℃ freezing and 4 ℃ freezing, the melanoidin showed good stability. Oxidizing agent H₂O₂ and reducing agent Na₂SO₃, sweetener and dark light had no significant effects on the stability of black garlic melanoidin, the direct light, sour agent, strong acid pH2~4 and weak base pH8~10 reduced its stability, while metal ions Zn²⁺ and Fe²⁺ had complex reaction with them. When the mass fraction was less than 2%, potassium sorbate and sodium benzoate would reduce the stability of melanoidin, while 0.05% sodium benzoate and 0.1% potassium sorbate had little effect on the stability of melanoidin, and could be used as preservatives for melanin food. The DPPH· and ·OH clearance rate of black garlic melanoidin were positively correlated with the concentration, when the original extract was diluted 10 times (0.842 mg/mL), it was up to 92% and 76%, respectively, indicating that black garlic melanoidin had strong antioxidant activity. Ultrasonic extraction of melanoidin would be beneficial to the dissolution of melanoidin, which could save extraction time and improve extraction rate. The melanoidin under ultrasonic extraction have strong antioxidant activity and great application prospects.