Stability of saponins from chickpea, soy and faba beans in vegetarian, broccoli-based bars subjected to different cooking techniques

Recently, saponins have been controversially discussed due to increasing evidence on their health promoting impacts. The present study aimed to determine the stability of saponins in vegetarian, broccoli-based bars (BBBs) incorporating chickpea (cp), soy (sb) and faba beans (fb) as protein sources after being subjected to different cooking methods. Commonly domestic ways of BBB preparation were microwaving, frying, frying and microwaving, steaming and baking. Saponins were analyzed by high-performance thin-layer chromatography (HPTLC) coupled to mass spectrometry (MS). Results indicated that HPTLC analysis with post-chromatographic derivatization and coupling to ESI-MS was capable of separating, identification and quantification of two saponin bands in chickpeas and faba beans, i.e. saponin B and 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyranone (DDMP) saponin. Defatted soy bean flour exhibited four bands (saponin B, DDMP saponin, derivatives of soyasaponins A and B). The total saponin content was 297, 4446, and 113 mu g.g(-1) dw in chickpea, defatted soy bean flour, and faba beans, respectively. Pretreatments, for instance soaking and peeling of chickpeas and faba beans reduced the total amount of saponins by 8 and 35%, respectively. Subsequently, different cooking conditions significantly reduced the saponin content by 23-32%, 18-59% and 26-36% in sb-BBBs, cp-BBBs and fb-BBB, respectively. Particularly, the DDMP saponin/saponin B ratio was affected. Apparently, conversion of unstable DDMP saponin to saponin B has been observed during the treatments. However, percentile concentration of the different saponins in the processed BBB does not vary compared to the untreated BBB. Soy beans seem not only to be an adequate source of vegetative proteins, but might be also used as a source of valuable saponins. Finally, an efficient determination method was presented providing evidence for predicting the thermal impact on saponins in innovative vegetarian BBBs. In this regard, optimization of cooking conditions considering the retained saponin amounts is recommended, especially for designing new functional foods. (C) 2015 Elsevier Ltd. All rights reserved.