Comprehensive molecular level characterization of protein- and polyphenol-rich tara (Caesalpinia spinosa) seed germ flour suggests novel hypothesis about possible accidental hazards

Tara (Caesalpinia spinosa, Leguminosae) seed germ (TSG), a by-product of tara gum (E417) extraction, has been used as a protein- and polyphenol-rich food ingredient for human and animal nutrition. Nevertheless, TSG is the alleged culprit for a recent foodborne outbreak of even severe acute illnesses that have affected hundreds of individuals in the USA, perhaps triggered by nonprotein amino acids such as baikiain. Herein, the composition of TSG has been characterized at molecular level, with a focus on proteins, phenolics, lipids, and mineral composition. TSG contains 43.4 % (w/w) proteins, tentatively identified for the first time by proteomics, and 14 % lipids, consisting of 83.6 % unsaturated fatty acids, especially linoleic acid. Ash is surprising high (6.5 %) because of an elevated concentration of P, K, Ca, and Mg. The detection of a rare earth element such as gadolinium (Gd, 1.6 mg kg-1), likely sourced from anthropogenic pollution, suggests alternative hypotheses for the origin of TSG hazards.