EXTRACTION OF BIOACTIVE COMPOUNDS FROM PURPLE CORN BY HIGH ISOSTATIC PRESSURE

Introduction: The purple corn (Zea Mays L.) is an ear that has the grain and the cob of purple color. It is an agricultural product originating in the Peruvian Andes and known around the world for having bioactive compounds found mainly in the cob. The most used method for the extraction of these compounds is the maceration with solvents, which demands prolonged periods of time and high amounts of solvent. Emerging methods, such as high-pressure technologies, have been successfully applied to extract bioactive compounds in less time and with fewer solvents. Objective: The objective of this study was to evaluate the effect of hydrostatic high pressure (250 MPa, 450 MPa and 650 MPa for three minutes) at constant processing temperatures (25°C, 45°C and 65°C) on bioactive compounds of purple corn compared to the conventional method. Methodology: A Peruvian purple corn cob was dried at 50 ° C for 24 hours, ground and sieved in No. 60 mesh. The centesimal composition and the determination of the particle size of the sifted cob were evaluated. The extracts were prepared with 20% ethanol-water solvent acidified to pH 2 with HCl 1N in a solid: liquid ratio 1:30 (w/v), processed by high isostatic pressure or by static maceration and vacuum filtered. All the extracts were stored in amber bottles, lined with aluminum foil and refrigerated at 4°C. The content of anthocyanins, phenolic compounds and color of the extracts were analyzed. Results and Discussion: The results showed at a constant processing temperature, the increase in the isostatic high pressure had a significant effect (p<0.05) in the content of bioactive compounds and the process at 650 MPa/65°C/3 minutes obtained the highest content of bioactive compounds (30.69 mg cyanidin 3-O-glucoside/g dry weight and 95.21 mg Gallic acid/g dry weight) showing a tendency to red color (L*:23.07, a*:0.03, b*:-0.35, C*:0.37, H°:260.83°). The content of bioactive compounds and color of the extracts processed with high isostatic pressure at 250 MPa/65°C/3 minutes corresponds to the best conditions found in the process by static maceration, that was at 2.5 hours/65°C (27.80 mg cyanidin 3-O-glucoside/g dry weight, 66.14 mg Gallic acid/g dry weight and L*:22.98, a*:-0.02, b*:-0.42, C*:0.41, H°:267.61°). This pressure-temperature interaction acts in a synergistic manner achieving greater extraction in less time than a conventional extraction. Conclusion: The content of bioactive compounds obtained by the high pressure technology was higher than the extracts obtained by the conventional method, showing that this emerging technology is very promising to improve extraction and decrease time for the extraction of bioactive compounds from plant tissue. References: Bligh, E. & Dyer, W. A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology, v.37, p. 911- 917, 1959.
Horwitz, W. Official methods of analysis of association of official analytical chemists, 13th ed.; Washington: A.O.A.C, 1980.
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)