Stability of saponins from chickpea, soy and faba beans in vegetarian, broccoli-based bars subjected to different cooking techniques Hassan Barakat a,b,1 , Valeria Reim a,1 , Sascha Rohn a, ⁎ a Institute of Food Chemistry, Hamburg School of Food Science, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany b Department of Food Science, Faculty of Agriculture, Benha University, 13736 Moshtohor, Kaliuobia, Egypt abstract article info Article history: Received 22 January 2015 Received in revised form 17 March 2015 Accepted 24 March 2015 Available online xxxx Keywords: Innovative vegetarian broccoli bars Processing Saponins Stability HPTLC 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 μg·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, optimiza- tion of cooking conditions considering the retained saponin amounts is recommended, especially for designing new functional foods. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Saponins are widely distributed secondary metabolites in the plant kingdom. They act as a chemical barrier or shielding compounds against pathogens and herbivores in the plant defense system (Augustin, Kuzina, Andersen, & Bak, 2011). The name of these compounds derives from the ability to form stable, soap-like foams in aqueous solutions (Francis, Kerem, Makkar-Becker, & Becker, 2002; Kerem, German-Shashoua, & Yarden, 2005; Shi et al., 2004). They are divided into two major classes: triterpenoid and steroid glycosides. Structures greatly vary because of the number of attached sugar units at different positions in the molecule. One of the major sources for saponins is legumes. Soy bean and chickpea seeds comprise saponin contents of 1.0–5.6 g 100 g -1 dry weight (Kerem et al., 2005; Shi et al., 2004). Also, Sharma and Sehgal (1992) found saponin content in faba bean of about 1.3–1.5 g·100 g -1 dw. The chemical structures of soy and chickpea saponins (for both so-called “soyasaponins”) have been described previously. Soyasaponins are triterpenoidal glycosides structurally divided into two groups. Based on the individual aglycones (soyasapogenol) and the amount of attached sugar moieties they are classified in group A and B soyasaponins, respectively. Group A soyasaponins are bidesmosidic (two sugar moieties at C3 and C22) and are sub-divided in two further groups known as acetylated and de-acetylated types. Whereas group B soyasaponins have only one glycosylation site at C3 (monodesmosidic) and are categorized into two sub-groups based on the conjugation with a 2,3-dihydro-2,5- dihydroxy-6-methyl-4H-pyranone (DDMP) unit at the carbon atom C22. DDMP conjugated soyasaponins are named as soyasaponin αg, βa, βg, γa and γg while non-DDMP conjugated saponins are called soyasaponin I (Bb), II (Bc), III (Bb′), IV (Bc′) and V (Ba). Group E soyasaponins (Bd, Be) usually formed as artifacts during saponin extrac- tion are also reported (Zhang & Popovich, 2009). Soy comprises four Food Research International xxx (2015) xxx–xxx ⁎ Corresponding author. Tel.: +49 40 42838 7979; fax: +49 40 42838 4342. E-mail address: rohn@chemie.uni-hamburg.de (S. Rohn). 1 These authors contributed equally to this work. FRIN-05759; No of Pages 8 http://dx.doi.org/10.1016/j.foodres.2015.03.043 0963-9969/© 2015 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres Please cite this article as: Barakat, H., et al., Stability of saponins from chickpea, soy and faba beans in vegetarian, broccoli-based bars subjected to different cooking techniqu..., Food Research International (2015), http://dx.doi.org/10.1016/j.foodres.2015.03.043