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 to 5 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.
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