Wild lupins’ protein could rival soy, say Spanish researchers

Lupin, or lupinus, is an ancient legume cultivated in the Mediterranean and the South American Andes. Amongst the major cultivated species are Lupin albus​ (white lupin), L. mutabilis​ (pearl lupin) and L, angustifolius (blue lupin). One of the major uses of lupin seeds is in animal feed, but they can be eaten by humans if the bitterness is removed.

Lupin seed flours can also be used for making protein isolates; and a lupin seed derived ingredient from Swiss firm Hochdorf is geared to the soy-free and lactose-free markets, as well as fat replacement for meat and bakery products.

While cultivated lupins have been seen to have a nutritional value comparable to soy beans – but suitable for quite different climates and soils – areas under cultivation have decreased in the last century, Javier Vioque of the Instituto de la Grasa in Seville and colleagues report. It is understood that only sweet lupins are currently consumed by humans, and the most important commercial cultivaton area for these is Australia.

They set out to evaluate the nutritional characteristics of seed proteins from six lupin species that grow in Southern Spain: L. angustifolius​, L. consentinii​, L. gredensis​, L.​ luteus​ and L. micranthus​. The seeds were collected from wild populations.

Comparable protein ​

The team found that the wild lupin seeds had protein levels ranging from 23.8 per cent for L. gredensis​ to 33.6 per cent for L. luteus​. Although cultivated lupin seeds tended to have more protein (for instance wild L. angustifolius averaged compared to 33.8 per cent in commercial samples ), these levels are still higher than other commonly consumed legumes like chick peas (24.7 per cent).

The animo acid composition was also analysed, as this indicates the nutritional quality of the protein. L. cosentinii​ was seen to have the most balanced animo acid make up, which was short only on lysine, and L. hispanicus​, which was also short on sulphur amino acids and tryptophan.

These amino acids are released on digestion, so an in vitro protein digestibility tests were conducted. Here the highest result was seen for L. cosentinii, with 89 per cent, and the lowest for L. gredensis with 82.3 per cent.

These figures are comparable to white lupin (86.9 to 88.8 per cent), soybean (85.8 per cent) and rice (84.8 per cent), and higher than for chickpea (76.2 per cent).

“Results confirm interest in studying wild populations if cultivated and non-cultivated Lupinus species as a source of seeds with good nutritional characteristics,”​ wrote the authors. “This may help in the domestication of new species or the use of wild populations in breeding programmes, favouring the bio-conservation of Lupinus.”​

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Source​

Food Chemistry 117 (3): 466-469, 2009

DOI: 10.1016/j.foodchem.2009.04.039

“Analytical nutritional characteristics of seed proteins in six wild lupinus species from Southern Spain.”​

Authors: Pastor-Cavada, E; Rocio, ; J; Pastor, J; Alaiz, M; Vioque J.