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, water or microwave in two different systems, and spears were frozen by blast or liquid nitrogen under different conditions. The influence of the process conditions on shear force values (toughness), vitamin C, dietary fibre, chlorophyll and drip loss was investigated. Spears with similar or higher shear force values and lower vitamin C were obtained by microwave blanching than by steam and water. No differences were found in shear force values, vitamin C, chlorophyll and dietary fibre between cryogenic and blast freezing, whereas cryogenic freezing reduced the drip loss significantly. Shear force values increased and vitamin C decreased slightly, whereas dietary fibre and chlorophyll did not change during frozen storage.