A study of saponins in legumes of importance to both human and animal nutrition

Ruiz, Raquel Gema (1996). A study of saponins in legumes of importance to both human and animal nutrition. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f79d

Abstract

This work describes the analysis and isolation of saponins using a range of chromatographic techniques, the development of a quantitative HPLC method for the determination of saponins as they occur in seed, and the study of various factors which affect both the saponin content and composition in different legume seeds.

Seed from 6 cultivars of lupin were grown in 4 regions of Australia, with up to 15 plots sampled within each region. Saponin contents ranged from 0 to 740 mg kg-1. Soyasaponin I, soyasaponin VI (the 2, 3-dihydro-2,5-dihydroxy-6-methyl-4H/-pyran-4-one conjugate of soyasaponin I) and a new saponin were found in the lupin seed. The changes observed in saponin content were dependent on cultivar, followed by the site and then the region where grown.

The saponin content of 20 cultivars of lentils grown in Spain ranged from 654 to 1269 mg kg-k Soyasaponins I and VI were present in all the cultivars. The saponin content depended on both seed size and testa colour.

The use of a mild extraction technique and an improved quantitative HPLC method showed soyasaponin VI to be the only saponin present in lupin seed whereas soyasaponin I was derived from soyasaponin VI when harsher extraction conditions were used.

The HPLC method was used to study the effect of soaking, cooking and germination on the saponin content and composition of two cultivars of both chickpeas and lentils. Soyasaponin VI was the only saponin detected in the unprocessed, soaked and germinated seed. Neither soaking nor germination modified the saponin content or composition of chickpeas and lentils. Soyasaponin VI was partially degraded during cooking into soyasaponin I, and both leached into the cooking solution. An overall loss of saponin content was found for lentil but none for chickpea.

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