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Etude de la biodisponibilité des protéines et acides aminés du tournesol chez le rat et l’Homme ; mise en œuvre de la méthode double traceur

Abstract : In the search for new plant protein sources for human nutrition, sunflower is a good candidate. There is no study on protein and amino acid quality of sunflower protein isolate in humans. Ileal direct digestibility assessment is invasive, that is the reason why a less invasive method, called dual tracer, was developed. This method is based on the ingestion of a 15N or 2H labeled test protein and 13C labeled reference protein. Relative ratio between the two isotopes (15N/13C or 2H/13C) for a given amino acid in the meal and the plasma reflects the relative absorption between the two proteins. This thesis aims (1) to determine sunflower protein quality and (2) to validate the dual tracer method in rats and in humans.Sunflower was labeled either with 15N and 2H under a greenhouse or with 15N in open fields, and protein were isolated. Rat studies allowed to characterize sunflower isolate quality, to evaluate the use of 13C spirulina as reference protein of the dual tracer method and to challenge this method in this model.The clinical study aimed to determine sunflower protein isolate quality included in biscuits and to compare direct ileal digestibility values obtained with direct measurement with a naso-ileal tube to those from the dual tracer method.Sunflower protein isolate have a high digestibility (95%) in rats but a lower digestibility in humans when incorporated and cooked in biscuits (87%) despite a good postprandial utilization (72%). Although moderately limited in lysine (DIAAS of 0.78 to 0.94 according to the conversion factor protein/N), its use in human nutrition is interesting. The dual tracer method was hardly applicable in rats, because of the small amount of blood available sequentially. In humans, comparison between ileal digestibility and plasma 15N/13C absorption indexes shows that the dual tracer method produces physiologically relevant values but about 10% lower than digestibility values and with a high imprecision. Better results could have been obtained with the use of 2H.
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Romain Tessier. Etude de la biodisponibilité des protéines et acides aminés du tournesol chez le rat et l’Homme ; mise en œuvre de la méthode double traceur. Alimentation et Nutrition. Université Paris-Saclay, 2020. Français. ⟨NNT : 2020UPASA017⟩. ⟨tel-03267957⟩

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