The extraction of protein from leaves of two energy willow clones (Salic cv. Aquatica and S. viminalis) and the chemical composition and nutritive value of the leaf fractions were investigated in six experiments. The preservation of leaf juice and wet leaf protein concentrate (LPC) was also studied. The extraction of juice averaged 33 % of the fresh weight, and the extraction ratios of dry matter (DM) and crude protein (CP) were 10.5 % and 2.9 %. The percentages of juice DM, CP and TP (true protein) separated in LPC were 6 %, 21 % and 48 %, respectively. The separation values were higher when LPC was precipitated by heating than by acidification. Removal of nutrients from the leaves was low and there were only minor differences in composition between the pressed pulp and the leaves. The leaf juice contained 8.3 % DM, of which 20.9 % was ash, 4.9 % CP, 1.9 % TP and 43.2 % sugars. The LPC had an average DM content of 19.6 %, CP being 21.4 % and TP 19.5 % of DM. The in vitro digestibility and pepsin-HCI-solubility of the protein were low. The mean tannin content of the LPC averaged 3.6 % of DM. The mean lysine and methionine contents of the LPC were low, 3.3 and 1.5 g/16 g N, respectively. The preservation of the leaf juice was satisfactory even without addition of preservative. Preservation of wet LPC was good with additives used at the 1.0 % v/w level. Leaf protein extraction was low and the nutritive value of LPC was not particularly high. This may have been partly due to the late date of harvesting and to the fact that the leaves were frozen for storage.
Leaf protein production from energy willow leaves
