Impact of industrial and culinary heat treatment on the (Poly)phenols of Piquillo pepper (capsicum annuum cv. Piquillo), their bioaccessibility and metabolization along the gastrointestinal tract and the action of gut microbiota, and their bioavailability

Resum

Piquillo pepper (Capsicum annuum cv. Piquillo) is a variety of red pepper accredited with the European Protected Designation of Origin (PDO) recognition, generally commercialised after a grilling treatment (approx. 700 ºC for 15 s), followed by a peeling process and a subsequent canning technique (102 ºC for 30 min). The present work aims to evaluate the effect of the industrial and culinary heat treatments applied to Piquillo pepper (Capsicum annuum cv. Piquillo) on its (poly)phenolic compounds and their release from food matrix during gastrointestinal digestion, including the action of gut microbiota (bioaccessibility), as well as to evaluate the bioavailability of the (poly)phenolic metabolites produced after the intake of Piquillo pepper. In raw Piquillo pepper, a total of 40 (poly)phenolic compounds were identified and quantified, being flavonoids (10 flavonols, 15 flavones, and 2 flavanones) the predominant compounds (62.6%). The high temperature applied during industrial grilling, together with peeling, causes a decrease of 59.8% in total (poly)phenolic content being flavonoids strongly affected (87.2% reduction) compared to non flavonoids which only decreased by 14%. Moreover, 9 non flavonoids were generated during grilling, making non flavonoids the most abundant compounds in peppers after industrial and culinary heat processes (74.4-80.1% of total (poly)phenolic content). Industrial and culinary heat processes applied to Piquillo pepper, positively impact on the release of non flavonoids from food matrix during gastrointestinal digestion and resulted in an enhanced bioaccessibility (116-175% BA) of total (poly)phenolic compounds compared to raw ones (102%), being microwaving the heat treatment that better preserves these compounds. The in vitro colonic metabolism of raw and heat-treated peppers also revealed the positive impact of industrial and culinary processes, specially frying, on the metabolization of native (poly)phenols into higher absorbable low molecular weight compounds. Based on the concentration and time of appearance of these derivatives, catabolic pathways of (poly)phenols from Piquillo pepper were proposed. The main colonic (poly)phenol derivatives identified were 3-(3-hydroxyphenyl)propanoic acid, 4-hydroxy-3-methoxyphenylacetic acid and benzene-1,2-diol. Twenty urine compounds (out of 39 catabolites identified) were associated to the consumption of microwaved Piquillo pepper, of those 4 cinnamic acids derivatives and 2 phenylpropanoic acids derivatives accounted for the 86.2% of the total metabolites excreted, being glucuronidation the main phase II transformation of (poly)phenols after absorption. The in vivo metabolism of (poly)phenols from microwaved Piquillo pepper showed that, even some (poly)phenols are absorbed in the upper gastrointestinal tract, the majority of native (poly)phenols of Piquillo pepper, in particular flavonoids, reach the colon and undergo an extensive metabolization before absorption. A great interindividual variability was observed in the total (poly)phenols metabolites excreted in urine after 24h (2.52- 30.28 µmol) due to colonic microbiota.