Juice from fresh, pulped, leaves is freed from most of the starch grains, fibre and detritusThe protcin coagulum is filtered off, washed with water In this form i t keeps under Texture, colour and nutritive value of the final product are determined by the con-The precautions needed during drying, especially freeze-drying, are The products are fairly stable at room temperature but lipids have to be re-The conditions for doing this by acetoneThe composition of the protein and the uses to which it can be p u t are described briefly.and coagulated quickly with steam. at pH 4 and pressed into blocks with 30-40o/b dry matter. refrigeration.ditions of drying. described. moved before the protein will keep permanently. extraction are described.
ExtractionThe reasons for making leaf protein on a large scale as a human food have been discussed in earlier publications1a:During the 12 years since bulk production started, the machinery has been gradually improved but the process remains, in essence, the same. Fresh leaves are pulped, with the addition of water or alkali if necessary, and the juice is then pressed out. The advantages of combining these two operations into one process are recognised but a suitable arrangement t o do it has not yet been perfected ; in our experience the rollers and screw expellors that others have tried are not satisfactory. The pulper has been described briefly.lb* It is so designed that it cannot clog but discharges pulp whether disintegration has been satisfactory or not. This arrangement, in which the operator controls the amount of work done on the charge by varying the time for which it remains inside the pulper, is regarded as preferable t o adding large amounts of water and flushing the fine material through a screen as it is made. The latter process has, however, its advocatcs.3 The available methods for pressing juice from a pulp of this type have been described elsewhere4a as has the type of press now used.*With high-quality crops, such as winter wheat cut at the beginning of May, half the protein of the leaf appears in the first extract, and if the fibre residue from the press is pulped again, with the addition of an amount of water similar t o the amount of juice already extracted, about half of the protein remaining will be extracted. It is seldom worth whilc extracting a third time. As the crop matures, the percentage extraction diminishes and by the time a leaf is beginning to yellow and becomes harsh to touch, only 15-20% of its protein will be extractable even if water and alkali are added.The usual agricultural crops such as the cereals, mustard, clover and lucerne, and a few by-products such as pea haulm and sugar-beet tops have juices a t pH 5.6-62. Extraction is improved by raising the pH to about 8 but generally not to an extent commensurate with the trouble of pH control. If the sap pH is lower than 5.6, it is essential t o add alkali during the pulping. Some fibre comes through the mesh of the press and it is inadvisable to try to stop this by using a finer mesh because t...
