Effect of aqueous and alkaline thermal treatments on chemical composition and oligosaccharide, alkaloid and tannin contents of Lupinus campestris seeds

The utilisation of Lupinus campestris seeds has been limited for some years owing to the presence of toxic quinolizidine alkaloids (QAs) and antinutri tional factors (ANFs). The oligosaccharide content was analysed by high-pre ssure liquid chromatography (HPLC). Gas chromatography coupled with mass sp ectrometry (GC/MS) was used to detect alkaloids, using caffeine (0.2mg ml(- 1)) as internal standard. Tannins were determined by the Folin-Dennis color imetric method. Two methods were tested to reduce or eliminate the QAs and ANFs, (a) aqueous thermal treatment and (b) alkaline thermal treatment (NaH CO3 0.5% solution), both of them for 6h at boiling temperature. In both cas es the removal of oligosaccharides, in amounts of 70 and 90% respectively, was also achieved. The alkaloid contents were reduced to innocuous levels i n both cases (less than 0.4-0.5%). The alkaline thermal treatment, in which the seed had a final alkaloid content of 0.002%, was more efficient than t he aqueous thermal treatment. The tannin content also showed a reduction of 71% with the aqueous treatment and 77% with the alkaline treatment. The re sults show that alkaline thermal treatment is more efficient at eliminating these ANFs. (C) 2001 Society of Chemical Industry.