Changes in texture and nutritional quality of green asparagus spears (Asparagus officinalis L.) during microwave blanching and cryogenic freezing

Green asparagus spears were blanched for a short or long period by steam, w ater or microwave in two different systems, and spears were frozen by blast or liquid nitrogen under different conditions. The influence of the proces s conditions on shear force values (toughness), vitamin C, dietary fibre, c hlorophyll and drip loss was investigated. Spears with similar or higher sh ear force values and lower vitamin C were obtained by microwave blanching t han by steam and water. No differences were found in shear force values, vi tamin C, chlorophyll and dietary fibre between cryogenic and blast freezing , whereas cryogenic freezing reduced the drip loss significantly. Shear for ce values increased and vitamin C decreased slightly, whereas dietary fibre and chorophyll did not change during frozen storage.