Application of pulsed vacuum acidification for the pH reduction of mushrooms

- Pulsed Vacuum impregnation (PVI) was studied as method to improve pH reduction of mushrooms.
- The response of mushrooms tissues was studied in different operative conditions.
- PVI was a useful tool to significantly improve pH reduction of mushrooms.
- Initial vacuum pulse was the most important process variables.
- The low rigidity of tissue allows to obtain a significant structural changes of capillaries.

A pulsed vacuum acidification (PVA) to improve the rate of pH reduction of mushrooms was studied. Two pressures at 400 mbar and 200 mbar maintained for a vacuum period of 2 min before the restoration of atmospheric pressure, were applied. Results stated that PVA may be used to significantly increase the rate of hydrogen ions diffusion into mushrooms due to the increase of acid solution-vegetable tissue contact area. The study of the response of vegetable tissue confirmed the importance of the initial vacuum pulse on total, gas and liquid volume changes. The results suggested the low rigidity of mushroom's tissues and highlighted the differences in terms of porosity reduction due to the impregnation level and the compression of pores at both the vacuum pressure studied. The remaining void fraction after PVA was in agreement with a greater impregnation at high vacuum pressure leading to a greater acidification rate.