Effect of sourdough fermentation on kamut prolamine

Introduction Kamut is frequently recommended as an excellent dietary substitute for wheat for wheat-hypersensitive people because of its presumed low allergenicity (http://www.kamut.com). However, in vitro and in vivo experiments showed no differences in allergic potential between wheat and kamut, probably due to the close phylogenetic relationship of these cereals (1). Allergenic impact depends on the content of immunotoxic sequences in flour. Nevertheless a long-time fermentation by selected sourdough lactic acid bacteria (LAB) may contribute to hydrolyse toxic peptides (2). This research focused on detailed analysis of the kamut proteins. Moreover, the potential of sourdough fermentation to hydrolyze prolamines giving rise to different peptide profiles was investigated with respect to yeast fermentation. Methods The protein composition in kamut and wheat flours (KF and WF) and doughs (K and W), and kamut sourdough (SK) was analysed. A subfractionation method was used to obtain different soluble protein fractions (3) which were analysed quantitatively by Bradford assay and qualitatively by SDS–PAGE. The different proteolysis patterns have been studied in relation to the composition of sourdough LAB populations analysed by DGGE. Results Water soluble protein fraction was higher in KF than in WF; gliadin and glutenin fractions were quantitatively comparable. Albumin and globulin were dramatically reduced in doughs respect to their amount in flours. Moreover, a little gliadin reduction was observed in K and SK. Glutenin fractions were particularly higher in SK than KF. These results suggest that during fermentation process, water soluble proteins were similarly solubilised in the different flours, but glutenin proteins became more easily removable specifically from SK because of specific transformation processes mediated by LAB. About qualitative composition, water soluble protein fractions showed the same pattern in KF and WF; on the contrary gliadins and glutenins showed a different pattern of protein compositions. Moreover, an interesting proteolysis pattern in SK of glutenin fractions and particularly of gliadin fractions (100-20 kDa) was observed. Discussion The capacity of sourdough process to degrade gliadin proteins is related to the combination of peptidase profiles of sourdough LAB population. Even though the hydrolysis profile patterns of single LAB strains have non been analysed, the peptidase activity depends on concentration of sourdough and duration of the fermentation process. This is the first work on the proteolytic activity of kamut sourdough and on its ability to modify gliadin peptides involved in celiac disease. References 1. Simonato et al. Allergy 2002: 57:653–654 2. Hurkman and Tanaka, Journal of Chromatography B, 849 (2007) 344–350 3. Di Cagno et al. Appl.Environ.Microbiol 2002 68: 623-633