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The mophane caterpillar, phane, the larval stage of the emperor moth, Imbrasia belina, is an important food source, with increasing popularity, in the southern African region. The protein and fat contents of phane have been estimated as 55% and 33% (w/w), respectively. Unsaturation content is about 60%, with α-linolenic acid being the dominant fatty acid in the lipid content of phane. An earlier investigation showed that the iodine values of two oil samples from two batches of phane at different ages, i.e., instars, varied significantly. The proximate fatty acid composition has now been determined by capillary GC for five oil samples from five batches of mophane caterpillar, ranging between early III and late V instars in order to investigate any differences in the nature of the lipid content due to age. The oil yield increased steadily from 19.8% (w/w) for early III instars to 38.3% for late V instars. The contents of palmitic and linoleic acids were 8.5% and 24%, respectively, for early III instars, and 31.1% and 10.7%, respectively, for late V instars. The composition of α-linolenic acid peaked at 39.1% for III/IV instars but decreased to 32.5% for late V instars. The lipid content of the leaves of the mophane tree, the principal food source of the mophane caterpillar, was found to be composed of 24% palmitic acid, 4.1% palmitoleic acid, 5.6% stearic acid, 14.85% oleic acid, 15. 6% linoleic acid and 32.9% linolenic acid, a fatty acid composition quite similar to that of mature phane, late V instars. Crude protein content varied irregularly with early III and late V instars being 59.3% and 62.0% (w/w), respectively. This study has demonstrated a dramatic variation in the composition of palmitic and linoleic acids in the lipid content from early III to late V instars of the larvae of Imbrasia belina. The study has also confirmed the larvae of Imbrasia belina as a rich source of protein and α-linolenic acid, the precursor of the w3 essential fatty acids.
KEY WORDS: Crude protein, Instars, Larval stages, Imbrasia belina, Emperor moth, Mophane caterpillar, •-Linolenic acid, Phane, Variations of fatty acid composition
Bull. Chem. Soc. Ethiop. 2004, 18(1), 67-72.