Study On Extraction Technology And Properties Of Red Pigment From Mulberry Pomace

Mulberry contains large quantities of anthocyanins and has been a potential resource of anthocyanins pigment. In recent years, people have pained more and more attention to natural anthocyanins as its safety and pharmacological functions. However, the large-scale application is greatly limited because of its unstability and weak tinctorial strength.This dissertation mainly studies the extraction technology, physicochemical properties, stabilities, antioxidant activities and application of red pigment from mulberry pomace, purposing on providing stable foundation for the further research and application of mulberry red pigment.The orthogonal test design was used to ascertain the optimum technologies, of traditional ethanol extraction and micro-wave assisted extraction. The optimum conditions for microwave extracting were as follows: 30% ethanol (pH=2.5) as extraction solvent at high microwave power for 8 min, and the ratio of material to liquid was 1:20. While treated with the traditional technology, the best results can be achieved at: 80% ethanol (pH=2.5) extracting 90 min at 80℃ and the ratio of material to liquid was 1:20. Using the technological parameters above mentioned, the average extraction ratios of total anthocyanins from mulberry pomace were 0.407% and 0.313% respectively. Treating with each method twice, the extraction ratio of total anthocyanins were over 90%. The results showed that the micro-wave assisted method strengthened extraction of mulberry pigment and saved time and ethanol.The stability of mulberry pigment under pH1.0 was evidently better than those under pH2.8 or pH4.5. The treatment of N₂ saved 21.10% of pigment, and light proof condition saved 50.46% of pigment, also low temperature enhanced the stability. Besides, low degree of ethanol showed little effect on the stability of pigment.The thermal degradation kinetics of mulberry pigment also suggested that low pH was beneficial to the stability. And the treatment of N₂ greatly advanced the stability of anthocyanin. At pH1.0, pH 3.2, pH 4.5, the thermal degradation activation energy (Eo) was 34.512, 28.948, 17.399 kJ/mol in O₂, respectively. While treated by N₂, E₀ was 63.335, 50.299, 32.033 kJ/mol respectively. It showed that N₂ treatment can increase the stability of anthocyanin in mulberry. Also, E₀ decreased as the pH increased, regardless of O₂ or N₂ medium. Those means the higher stability of anthocyanin can be achieved in lower pH. Thus the mulberry pigment could be stored in low pH and temperature, avoiding light and oxygen conditions.The in vitro antioxidant activities of mulberry extracts were studied and evaluated. The total antioxidant capacity of lg mulberry pigment extract was equivalent to that of 0.72g Vc. The anthocyanin content was used to express the quantity of mulberry pigment. The IC50 values for lipid per-oxidation, -OH, DPPH- and ABTS+ were 18.56, 77.62, 35.91 and 109.33mg/L, respectively. These all suggested that the mulberry extract should be an excellent natural antioxidant and free radicals scavenger. Mulberry anthocyanin could be purified to find certain components which actually function.The optimal parameters of freeze-drying technology were that the desorption pressure of drying room was 90 Pa, heating temperature in desorption was 60 °C, and freeze-drying time was 12h. Under these conditions, a red homogeneous powder with good dissolvability was obtained. It showed good tinctorial strength in beverage and yogurt, with adding amount from 0.05% to 0.2%. Also it can be pressed into tablets as nutrition supplements.