Application of ohmic heating for black pepper (Piper nigrum L.) oleoresin extraction compared with conventional heating

The aims of this research were to investigate the possibility of applying ohmic heating for assisting in solvent extraction of black pepper oleoresin and to compare the yield and quality of oleoresin with that obtained from the conventional heating method. The electrical conductivities were measured of black pepper powder mixed with different solvents and the residues from each extraction stage. The extraction was conducted in two stages using a black pepper powder-to-solvent ratio of 1:10. The electrical conductivities of the black pepper powder and residue mixtures ranged from 0.01 to 0.17 S/m depending on the ethanol-to-distilled water ratio and extraction stage. Ohmic heating extraction significantly improved the oleoresin yield and piperine content compared to conventional heating. The microstructures of the powder and residues obtained after extraction indicated that ohmic heating caused pores and fractures in the cell walls of black pepper cells that facilitated solvent and oleoresin transfer. Novelty impact statement This study revealed that the electrical conductivity is an indicator of the oleoresin content in the black pepper powder and raffinate. Moreover, ohmic heating has potential for the commercial extraction of black pepper oleoresin and provided scientific evidence of yield and quality improvement. The application of ohmic heating-assisted extraction could broaden the technology for extracting spice oleoresins in the food industry.

Automated summary

This study reveals that electrical conductivity can be used as an indicator of oleoresin content in black pepper powder and raffinate. Moreover, ohmic heating has the potential for commercial extraction of black pepper oleoresin and provides scientific evidence for improving yield and quality. The application of ohmic heating-assisted extraction could broaden spice oleoresin extraction technology in the food industry.