| 摘要 |
Natural food products containing starch cells and having a water content over 60 per cent, such as potatoes, apples or mixtures of cereal meals or vegetable pulp, are cooked to break down the starch cells and to destroy the enzymes and then extruded without further heating in the form of bars or ribbons of small cross-section, e.g. 1/8 -/ba1/4 inch diameter, which are subjected to streams of heated air, steam or vapour at a speed of 20-40, and preferably about 32, feet per second relatively to the surface thereof to convert them into tubes by the rapid drying of their outer surface prior to the drying out of the interior. The bars or ribbons may be extruded on to a travelling conveyer and dried thereon by heated streams of air &c. supplied through venturi nozzles from a chamber containing compressed air &c. The outer surface of the tubes may be slightly caramelised by initial drying at a temperature of between 250 DEG and 300 DEG F., but if the product is to be ground to flour, the temperature should preferably not exceed 220 DEG F. Flavouring materials, such as salt and cheese, may be included. |
