White button mushroom (Agaricus bisporus L.) was subjected to osmotic dehydration at different concentrations of common salt (sodium chloride) i.e. 10, 15, 20 and 25% and sugar solution i. e. 50, 60 and 70°B and dried in hot-air oven at 55 ± 2 °C. There were about 31.2, 29.4, 27.2 and 24.4% reduction in weight with 10, 15, 20 and 25% salt solutions and 35.4, 38.3 and 38.8% with 50, 60 and 70°B sugar solution respectively. It took about 240, 220, 200 and 180 minutes to dry samples after osmotic treatment with 10, 15, 20 and 25% salt concentration and 240, 220 and 220 minutes with 50, 60 and 70°B sugar solution respectively. The untreated samples took about 340 minutes for complete drying. The colour was brighter for samples dried after OT with 25% salt and 70°B sugar concentrations having lowest optical density (OD) values. The dried products were packed in 200 gauge polypropylene bags and stored at ambient condition for one year. The chemical, microbial and organoleptic changes were monitored for one year. Storage study showed that there was marginal increase in moisture content and decrease in organoleptic quality of osmoa-air dried (OAD) mushroom slices. The samples dried after osmosis with 25% salt and 70°B sugar concentrations were found microbiologically safe and organoleptically acceptable up to one year of storage at ambient condition.
Mass transfer characteristics during ultrasound-assisted osmotic dehydration of button mushroom (Agaricus bisporus)
