Comparative analysis of protein composition and digestibility of Ceratonia siliqua L. and Prosopis spp. seed germ flour

By virtue of exclusive nutrient composition and nutritional properties, seed germ flours from both European carob (Ceratonia siliqua L.) and South American algarrobo (Prosopis alba and Prosopis nigra) or vinal (Prosopis ruscifolia) have potential as a high nutritional value and health-promoting ingredient for food formulations. In order to define their compositional and functional properties, we investigated the germ protein content of carob compared to the P. alba, P. nigra and P. ruscifolia counterparts, applying proteomics and complementary methods. The mono- and two-dimensional electrophoretic profiles of Prosopis spp. were very similar among one another, while C. siliqua exhibited significant differences. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy highlighted a dominant beta-sheet structural conformation for C. siliqua, suggesting that carob germ flour might more suited than Prosopis germ flour for baking and food technological applications. In contrast, Prosopis spp. contained a more adequate nutritional value than C. siliqua, in terms of essential amino acid complement. Both carob and algarrobo germ flour samples were highly digestible, as demonstrated by in vitro simulated gastrointestinal digestion, releasing high amounts of free amino acids and only minor proportions of low molecular weight peptides.