The blue-green alga, Spirulina maxima, examined in the form of a spray-dried powder, contains 11 % of lipid, which has been analysed in detail with a view to establishing both the classes of lipid present and their fatty acid profiles. The dominant lipids are mono-, di-and probably higher galactosyldiglycerides and phosphatidyl glycerol. Unlike other algae, Spirulina synthesises cis-6-cis-9-cis-12 octadecatrienoic acid in contrast to its 9-12-15 isomer.

Although freeze-dried leaf protein concentrate (1.p.c.) contains as much as 15-20 % of lipids in which linolenic acid (60%) is the predominating component fatty acid, it appears to be unexpectedly stable when stored under ordinary conditions, i.e. at room temperature and exposed to air. Linolenic acid, in the form in which it occurs in 1.p.c. is less prone to destruction than in the form of total lipid isolate, or in the form of more conventional linolenic-containing vegetable oils. Rates of disappearance of linolenic acid and also loss of protein quality as judged by dye-binding capacity, on heat treatment appear to follow a progressive trend as temperature is increased, without displaying a well-defined order of reaction. With increasing temperatures, increased moisture levels result in an increase in the rates of both lipid and protein transformations. In heat treatments involving temperatures below 100°C, the presence of the lipid fraction does not affect protein transformation. At higher temperatures, when the lipid itself undergoes substantial oxidation, protein quality as judged by dye-binding capacity is considerably affected.

Leaf protein concentrates contain 10 % or more of lipids which have been analysed in detail with a view to establishing both the classes of lipid present and their component fatty acid profiles. Variable factors such as the species of crop, its degree of maturity and the cellular origin of the concentrate fraction have been shown to have a quantitatively important influence on lipid patterns and on yields.

Studies extending throughout a period of 100 days' growth have been made on the total lipids of ryegrass, kale and fodder radish. Expressed in terms of % dry matter, lipids are at amaximum of about 10 to 11 % during the period of vegetative growth.Lipid yields in absolute terms are maximal at 200-300 kg/ha after 56 to 70 days from sowing, at which stage lipids have fallen to 7 to 9% of total dry matter, according to species.Considering the fatty acids as a whole, dominant components are linolenic and palmitic, the latter rising and the former falling as maturation progresses. Minor fatty acids show no clear trend. More specific changes in fatty acid profiles are revealed when individual lipid classes are studied separately.Lipid classes display a predictable change in pattern as maturation progresses. New growth is rich in partial glycerides and free sterols, and particularly in monoand digalactosyl diglycerides and sulphoquinovosyl diglyceride. Leaves from mature or senescing crops show progressive falls in these components, accompanied by the appearance of triglycerides, free fatty acids and steryl glycosides. In the case of fodder radish the accumulation of the hydrocarbon, n-nonacosane, is a noteworthy feature. The principal phospholipids do not change appreciably with maturation.The trends observed on maturation show common general patterns for all the leafy crops so far studied. They do emphasise, however, the crucial importance of specifying both species and duration of growth when quoting data on leaf lipid compositions.