Effects of Blanching, Chemical Treatments and Freezing Methods on Quality of Freeze‐dried Mushrooms

SUMMARY –Mushrooms, Agaricus bisporus, were cut into slices about 5 mm thick. The polyphenoloxidase activity in the sliced mushrooms was inhibited by: (a) dipping in sodium metabisulfite solution containing 200 ppm SO 2 ; (b) dipping in 2% NaCl solution; and (c) blanching in boiling water for 2 min followed by evaporative cooling. The products were frozen with Freon‐12 at –22°F for 60 sec. The frozen mushrooms were dried to 3% moisture in a Stokes freeze drier and sealed under vacuum in No. 2–1/2 cans. The freeze‐dried product made by the Freon‐dipping process was better in quality and firmer in texture than that made by the slow‐freezing process. Blanching the fresh mushrooms in boiling water for 2 min prior to freezing results in a lighter color in the freeze‐dried products after rehydration. However, the product was less attractive in flavor and texture. The blanching process caused considerable loss of water‐soluble solids and ascorbic acid. The effects of processing variables on the chemical, physical and organoleptic quality of the rehydrated products are presented.