Development of saponin-rich baked goods

Cardiovascular disease is a major cause of death in the western nations that affects as many as 81.1 million citizens in the US each year (American Heart Association 2010). Recent studies showed that soy and chickpea saponins may play a role in cardiovascular disease prevention (Southon et al. 1988; Harwood et al. 1993; Matsuura 2001; Kerwin 2004; Kim et al. 2004; Yamsaengsung et al. 2010).;In this study, isolation protocol was optimized for high yield saponins extraction from food ingredients by semi-preparatory HPLC. Accurate analytical techniques were developed for identification and quantification of soy and chickpea saponins in food ingredients and biological samples by HPLC-PDA and LC-MS. Saponin extracts (in the form of isolates and mixtures) and breads developed with saponin-rich ingredients (soy flour, soy milk powder, chickpea protein isolate) were processed by in vitro digestion in order to assess saponin effect on cholesterol micellarization and their bioaccessibility in the in vitro model. Saponin-rich baked goods were developed for a broad variety of systems: pocket-type flat doughs reformulated with soy blend; soy bread added of soy saponin extract; wheat breads added of chickpea saponin isolate and soy bread reformulated with the addition of chickpea protein isolate.;Upon screening of several food ingredients by HPLC-PDA, soy and chickpea flours were chosen for saponin isolation. The isolation protocol resulted in high yield. Furthermore, control of temperature, pH and the extraction time were optimized, minimizing the conversion of DDMP to type B saponins. LC-MS detected 17 saponins in soy ingredients (A, B, E and DDMP type) while only Bb and betag in the chickpea counterparts. Conversion of DDMP to B type was observed in the protein isolates.;No significant effect of saponins on cholesterol micellarization was observed during in vitro digestion, thus suggesting an alternate path for their proposed hypocholesterolemic activity. LC-MS analysis confirmed stability of saponins during bread making with the exception of type E saponins (∼30% recovery). Some loss occurred upon in vitro digestion: recovery in digesta was 60% for type A, 100% for type B, 100% for type E and 90% for DDMP type suggesting minimal degradation and partial conversion of the DDMP type during digestion. Higher recoveries were observed for soy bread as compared to chickpea containing breads, thus suggesting a matrix effect on saponin stability and bioaccessibility. Micellarization rate was higher for DDMP type (80 vs. 60%) and low uptake of saponins by Caco-2 cells was observed with predominance of B type (1-3% test medium).;Saponin addition affected texture of baked goods differently, depending on the product and the system chosen. Soy blend addition to pocket-type flat doughs resulted in soft, yet tough and rubbery texture. Increased "freezable" water (from 7.0 to 16 g water/100 g sample) was observed thus depicting poor plasticization of the gluten-starch network. When soy saponins were added as an extract to soy bread, a dramatic reduction of hardness during 7 days ambient storage was observed, thus suggesting anti-staling properties of these compounds. Chickpea saponins (1% addition) in the form of solvent extract resulted in harder texture of the wheat breads, significant loaf volume increase and lower "freezable" water content. The isolate contained also water soluble fiber that may have contributed to such changes. Reformulation of soy bread with chickpea protein isolate resulted in harder and denser breads at 2/3 substitution.;In conclusion, a method for high yield isolation of soy saponins by semi-preparatory HPLC was optimized and a method for soy saponin identification and quantification by LC-MS was developed. Soy saponins were shown to be stable under bread making conditions and to degrade partially during in vitro digestion. Micellarization was necessary for the uptake of most soy saponins although the uptake measured by Caco-2 cells was very low (1-3%). Saponins addition to baked goods in the form of extracts negatively affected their physicochemical properties. Nonetheless, incorporation of saponin-rich ingredients (i.e. soy blend) improved textural qualities of flat products.