PEF Extraction of Valuable Compounds from White Button Mushroom (Agaricus Bisporus)

Abstract

Pulsed electric field (PEF) is an emerging technology that involves the application of electric pulses to food materials placed between electrodes. Exposure of plant tissues to electric field causes an increase of the cell wall porosity and enhances extraction of the intercellular materials from fruits and vegetables. In contrary to the conventional extraction method of long duration high temperature treatment, the short time duration of PEF extraction can reduce the deterioration of these valuable compounds to a minimal level. White button mushrooms (Agaricus Bisporus) are rich sources of bioactive compounds, such as β-(1-3)/ (1-6)-glucans and polyphenols. Pulsed electric intensity in the range of 12.4 to 38.4kV/cm was applied with bipolar square pulses of 2μs pulse duration. The effect of continuous PEF treatment on the extraction of white button mushroom suspension (9% w/w) was studied. By evaluation of the characteristics of the extracts obtained with different conditions of PEF treatment, the optimum extraction yields of 98% ± 0.10 (7.9mg/g of mushroom) polysaccharide, 51% ± 0.07 (1.6mg GAE/g of mushroom) total polyphenols, and 49% ± 0.09 (2.7mg/g of mushroom) proteins were achieved, after exposing the mushroom suspension to electric pulses of 38.4kV/cm field intensity for 272μs and a treatment temperature of 85ºC. On the other hand, conventional extraction of 9%w/w mushroom suspension at 95ºC for 1 hour obtained yield of only 56% ± 0.06 (6.4mg/g of mushroom) polysaccharide, 25% ± 0.03 (1.3mg GAE/g of mushroom) total polyphenols, and 45% ± 0.10 (2.6mg/g of mushroom) proteins. Moreover, the temperature change during PEF extraction at optimum conditions was identified. The yield of conventional extraction operated at the same temperature and for few minutes was negligible for all of these compounds. This concludes that the extraction enhancement of PEF is not exclusively due to the ohmic heat generated during processing. Nevertheless, the ohmic heating of PEF permits further enhancement of extraction, suggesting a synergistic effect of electric pulses and temperature on the extraction performance. Evaluation of the A260/280 values of the extracts revealed that PEF-treated extracts obtained a higher nucleic acid/ protein ratio. In addition, there was no difference between the PEF extracted and conventional extracted juice with respect to its pH value and particle size distribution. This work demonstrated the advantages of PEF over conventional extraction and revealed that optimization of PEF processing parameters is of prime importance.