Contents lists available at ScienceDirect Journal of Functional Foods journal homepage: www.elsevier.com/locate/jff Effect of a polyphenol-rich plant matrix on colonic digestion and plasma antioxidant capacity in a porcine model Chunhe Gu, Kate Howell ⁎ , Anneline Padayachee, Thea Comino, Ratana Chhan, Pangzhen Zhang, Ken Ng, Jeremy J. Cottrell, Frank R. Dunshea School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, VIC 3010, Australia ARTICLE INFO Keywords: Purple carrots Polyphenols Cholesterol Short-chain fatty acids Dietary fiber Gut microbiota ABSTRACT Altering cellular structure by reducing the particle size and applying heat may enhance the release of poly- phenols from the plant cell matrix. The released polyphenols could ameliorate the impacts of a high-fat diet. Using a pig model in a 2 × 2 cross-over trial, we tested the effects of processing on the bioaccessibility of polyphenols in the diet, using low- and high-fat diets supplemented with raw and diced or cooked and pureed black carrots. Raw diced black carrots resulted in higher average particle size in the digesta of all gastrointestinal compartments and higher total and major short chain fatty acids in the descending colon. Supplementing the diet with raw and diced carrots also increased the colonic bacterial counts but with limited effects on gut microbiome diversity. The presence of carrots did not mitigate the negative impacts of decreased plasma antioxidant capacity and high atherogenic index induced by a high-fat diet. 1. Introduction Long-term consumption of high-fat diets has been widely reported to contribute to increasing intravascular low-density lipoproteins (LDL) levels, which is one of the major risk factors for the development of atherosclerosis and cardiovascular diseases (Dauchet, Amouyel, & Dallongeville, 2009; Glass & Witztum, 2001; Ross, 1999). Polyphenols, a class of secondary plant metabolites present in fruits and vegetables, form an integral component of the daily human diet, and have beneficial health functions of atherosclerosis prevention due to their enhancement of plasma antioxidant defences (Dauchet et al., 2009; Finley et al., 2011; Key, 2011). Absorbed polyphenols can in- crease the total antioxidant capacity (TAC) of plasma and therefore have the capacity to reduce the accumulation of oxidised LDL (Halliwell, 2006). However, plant cell walls (PCWs) can shield macro- nutrients from digestive enzymes and bile acids and therefore effec- tively reduce the digestibility and absorption of polyphenols in the stomach and small intestine (Capuano & Pellegrini, 2019). Also, poly- phenols can be restrained in the food matrix through ionic interactions and hydrophobic interactions with the PCWs (Padayachee et al., 2012a, 2012b). These factors limit polyphenol release in the stomach and small intestine (Fleschhut, Kratzer, Rechkemmer, & Kulling, 2006; Padayachee et al., 2013). Decreasing particle size of components in the diet is related to higher absorption of nutrients by the human body (Ercolini & Fogliano, 2018). Therefore, treatment of the food matrix may release and increase bioavailability of polyphenols, to allow these important compounds to interact with the digestive enzymes and the whole organism. Despite the possible improved bioavailability of the polyphenols, disrupting the plant cells walls may also allow the destruction of cell wall dietary fibers (DFs) to attenuate the beneficial functions of DFs in colonic health. DFs are resistant to digestion and help regulate and maintain the digestive tract as substrates for microbiota fermentation (Lee, Inglett, & Carriere, 2004; Padayachee, Day, Howell, & Gidley, 2017). The short chain fatty acids (SCFAs) produced during the colonic fermentation of DFs play important roles in the maintenance of colonic epithelium integrity (Scheppach, 1994) and lower the luminal pH, which helps supress tumour cell proliferation, and provides a protective https://doi.org/10.1016/j.jff.2019.04.006 Received 18 March 2019; Received in revised form 1 April 2019; Accepted 2 April 2019 Abbreviations: PCW, Plant cell wall; TAC, Total antioxidant capacity; ROS, Reactive oxygen species; GI, Gastro-intestine; SCFA, Short-chain fatty acid; PSFA, Polysaturated fatty acid; DF, Dietary fiber; RS, Resistant starch; AI, Atherogenic index; LDL, Low-density lipoprotien; HDL, High-density lipoprotein; FRAP, Ferric reducing ability of plasma; PCoA, Principal coordinate analysis; HFC, High-fat diet control; HFD, High-fat diet supplemented with raw diced black carrots; HFP, High- fat diet supplemented with pureed black carrots; LFC, Low-fat diet control; LFD, Low-fat diet supplemented with raw diced black carrots; LFP, Low-fat diet sup- plemented with pureed black carrots ⁎ Corresponding author. E-mail address: khowell@unimelb.edu.au (K. Howell). Journal of Functional Foods 57 (2019) 211–221 1756-4646/ © 2019 Elsevier Ltd. All rights reserved. T