Mushrooms that are to be canned are typically blanched for long times to preshrink them. Our objectives were to compare the weight and volume loss of mushrooms during blanching under conventional and ohmic heating conditions and to investigate waveform and frequency effects of ohmic heating. In our setup, it was possible to heat mushroom caps with ohmic heating to above 70C in 40 s while maintaining a 50% solid mushroom content in water. Weight loss predicted using previously published kinetic models, and internal mushroom temperature data suggested that substantially greater shrinkage occurred than attributable to temperature alone. Shrinkage predictions were more consistent with experimental values when the temperature of the surrounding medium was used as a basis, suggesting that some combination of thermal and nonthermal permeabilization mechanisms may be in action. Ohmic blanching offers the advantage of being able to maintain a high solids content during blanching compared to the use of excessive amounts of water (60 kg/400 L) in conventional blanching. Frequency and waveform did not affect the weight loss during ohmic blanching in the range studied. Ohmic heating may have potential for this application due to its rapid, volumetric heating rates, and the enhancement of mass transfer even at relatively low temperatures.