Rat Studies on Quality of Protein and Growth-inhibiting Action of Alkaloids of Lupine (Lupinus termis)

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Abstract
Lupine (Lupinus termis) seeds are commonly consumed in the Middle East. The high protein content (35–40%) of the seeds makes them an inexpensive source of dietary protein. Before consumption the untreated bitter seeds are boiled, then soaked in water for several days which removes the bitter taste and the endogenous alkaloid substances in the seeds. This investigation was conducted to evaluate the nutritive quality of the lupine seed protein and the nutritional effects of consuming the alkaloid fraction, by rats. Amino acid analysis showed that, in a 10% lupine protein diet, methionine, lysine and threonine contributed less than half the requirements of the rat for each. Rats fed diets containing 10% protein from untreated lupine seeds failed to grow. Also when an extract of lupine containing the alkaloid fraction was added to a casein diet fed to rats, it suppressed growth severely. Growth of rats fed untreated lupine seeds was improved, however, by removing the alkaloid fraction from the seeds, by increasing the level of dietary protein, and by supplementing the diets with the limiting amino acids. It was concluded that poor growth observed in rats fed untreated lupine diets resulted from both the presence of alkaloid substances and the poor quality of dietary protein. If lupine is to be considered a source of food protein for humans, these 2 factors must be considered in the development of methods of processing lupine seeds for consumption.