High True Ileal Digestibility but Not Postprandial Utilization of Nitrogen from Bovine Meat Protein in Humans Is Moderately Decreased by High-Temperature, Long-Duration Cooking.
BACKGROUND
Meat protein digestibility can be impaired because of indigestible protein aggregates that form during cooking. When the aggregates are subsequently fermented by the microbiota, they can generate potentially harmful compounds for the colonic mucosa.


OBJECTIVE
This study evaluated the quantity of bovine meat protein escaping digestion in the human small intestine and the metabolic fate of exogenous nitrogen, depending on cooking processes.


METHODS
Sixteen volunteers (5 women and 11 men; aged 28 ± 8 y) were equipped with a double lumen intestinal tube positioned at the ileal level. They received a test meal exclusively composed of 120 g of intrinsically (15)N-labeled bovine meat, cooked either at 55°C for 5 min (n = 8) or at 90°C for 30 min (n = 8). Ileal effluents and blood and urine samples were collected over an 8-h period after the meal ingestion, and (15)N enrichments were measured to assess the digestibility of meat proteins and the transfer of dietary nitrogen into the metabolic pools.


RESULTS
Proteins tended to be less digestible for the meat cooked at 90°C for 30 min than at 55°C for 5 min (90.1% ± 2.1% vs. 94.1% ± 0.7% of ingested N; P = 0.08). However, the particle number and size in ileal digesta did not differ between groups. The appearance of variable amounts of intact fibers was observed by microscopy. The kinetics of (15)N appearance in plasma proteins, amino acids, and urea were similar between groups. The amount of exogenous nitrogen lost through deamination did not differ between groups (21.2% ± 0.8% of ingested N).


CONCLUSIONS
Cooking bovine meat at a high temperature for a long time can moderately decrease protein digestibility compared with cooking at a lower temperature for a short time and does not affect postprandial exogenous protein metabolism in young adults. The study was registered at www.clinicaltrials.gov as NCT01685307.
['Oberli|Marion|M|', 'Marsset-Baglieri|Agnès|A|', 'Airinei|Gheorghe|G|', 'Santé-Lhoutellier|Véronique|V|', 'Khodorova|Nadezda|N|', 'Rémond|Didier|D|', 'Foucault-Simonin|Angélique|A|', 'Piedcoq|Julien|J|', 'Tomé|Daniel|D|', 'Fromentin|Gilles|G|', 'Benamouzig|Robert|R|', 'Gaudichon|Claire|C|']
D000328:Adult D000818:Animals D002417:Cattle D003296:Cooking D018592:Cross-Over Studies D004044:Dietary Proteins D004063:Digestion D005260:Female D006358:Hot Temperature D006801:Humans D007082:Ileum D007408:Intestinal Absorption D007413:Intestinal Mucosa D008297:Male D008460:Meat D009584:Nitrogen D009587:Nitrogen Isotopes D016037:Single-Blind Method D013997:Time Factors D055815:Young Adult
digestion postprandial protein metabolism healthy volunteers stables isotopes