Abstract:

The production process of superfine powder of vacuum freeze-dried Chaenomeles sinensis (Thouin) Koehne fruits was studied and the product obtained was analyzed for nutrients and sensory qualities. The optimal material granularity and thickness for vacuum freeze drying were 0.95 cm3 and 15－20 mm, respectively. A maximum freeze drying percentage was obtained under the following sublimation-drying conditions: vacuum degree 40 Pa, heating plate temperature 60 ℃, material temperature －40 ℃, and condensing temperature －35 ℃. The best secondary-drying conditions were: vacuum degree 20 Pa, heating plate temperature 85 ℃, material temperature 40 ℃, and condensing temperature －35 ℃. The freeze-dried material was firstly crushed to 60－80 mesh using a plant pulverizer and then micro-grinded to over 1000 mesh using a fluidized bed jet mill at pressures over 12 MPa and temperatures below 35 ℃ and a finished product was obtained. The product displayed good rehydration, dissolubility and activity, and the color, smell and taste as well as nutrients of raw material remained complete. Thus, it has a promising prospect in deep processing.

Key words: Chaenomeles sinensis (Thouin) Kotne, vacuum freeze-drying, superfine comminution, superfine powder