Industrial Leaf Concentrate Process (France)
1. Pulping and pressing of lucerne (alfalfa)
Immediately after cutting, the lucerne is pulped and pressed forcefully to separate a large part of the nutritional factors from the indigestible fibre. Done rapidly, this stage also limits hydrolysis of cellular proteins by proteases. The nutritional elements, consisting principally of chloroplastic and cytoplasmic proteins, pigments and vitamins, are recovered in the green juice expressed.
The co-product of this green juice, the ligneous and cellulosic bits of the stalk and leaves, is dried and used as fodder, it still contains plenty of nutrients. Its overall nutritive value, moreover, is improved because of the shattering of the stalk fibres (the nutrients are freed and the fibres themselves more easily digested by the cellulytic ferment in the rumen).
2. Heat coagulation of protein
The green juice, adjusted to pH 8,5 to slow down the action of phenyloxydase and to improve the struture of the coagulum, is pre-heated and then brought to 85-90* C by steam injection. This causes coagulation of almost all the proteins which are within the pigments; fat-soluble vitamins, lipids and minerals.
3. Separation of the coagulum
Next, the coagulum (moist green curd containing the majority of the nutrients) is centrifuged from the rest of the solution (brown juice).
This curd contains more than 50 % of crude protein, of which 80 % is true protein, accompanied by some free amino-acids or peptides. Heat coagulation extracts on average 8 % of the original DM of the crop and 20 - 25 % of its protein.
4. Drying and storage
The curd, as paste, having been mechanically separated from most of the brown juice is dried on a fluidised bed. So far, the making of concentrates for animal or human consumption is the same.
Then, the PX Super (commercial name of the concentrate destined for animal feed) is pelleted and stored in sealed silos' cells under inert gas, awaiting distribution.
For human feeding, the product called Extrait foliaire (or leaf concentrate) is ground. This leafmeal (on average with moisture content of 8 %) must be kept dry, away from air, heat and light. Thus, they are bagged hermetically immediately.
To protect pigments and vitamins an antioxidant is added
- For animal feed: Ethoxyquin (150 mg/kg)
- For human feed : Ascorbic acid (500 mg/kg).
5. By-product usage
The brown juice, still containing 13 - 15 % of the original dry matter (DM) is mainly soluble Nitrogen mineral salts and sugars It is mixed with the fibrous residue. This mixture is dried in high temperature air in a rotating drum. The by-product thus obtained is ground, pelleted and stocked for marketing. It contains 16-20 % protein, 25-30 % cellulose and 100-150 mg carotene/kg. It is excellent fodder for cattle and rabbits.
For the profitability of this industry, the realization of the value of the two products (protein extract and co-product representing- respectively 8 % and 92 % original DM) is essential.
6. Homogeneity of Leaf Concentrate
The protein content of LC varies slightly, from 50 - 60 %, although the protein content of lucerne as cut varies from 15 - 25 %, according to the timing of the cut and vegetative stage of the crop. Thus the variation in quality of the vegetation processed results in a quantity of LC
between 6 and 12 % of original DM with an average of 8%