A simulated in vitro digestion model was used to elucidate the impact of dietary fibers on the digestion rate of emulsified lipids. The influence of polysaccharide type (chitosan (cationic), methyl cellulose (non-ionic), and pectin (anionic)) and initial concentration (0.4 to 3.6% (w/w)) was examined. 2% (w/w) corn oil-in-water emulsions stabilized by 0.2% (w/w) Tween-80 were prepared, mixed with polysaccharide, and then subjected to an in vitro digestion model (37 °C): initial (pH 7.0); oral (pH 6.8; 10 min); gastric (pH 2.5; 120 min); and, intestinal (pH 7.0; 120 min) phases. The impact of polysaccharides on lipid digestion, ζ-potential, particle size, viscosity, and stability was determined. The rate and extent of lipid digestion decreased with increasing pectin, methyl cellulose, and chitosan concentrations. The free fatty acids released after 120 min of lipase digestion were 46, 63, and 81% (w/w) for methyl cellulose, pectin, and chitosan, respectively (3.6% (w/w) initial polysaccharide), indicating that methyl cellulose had the highest capacity to inhibit lipid digestion, followed by pectin, and then chitosan. The impact of the polysaccharides on lipid digestion was attributed to their ability to induce droplet flocculation, and/or due to their interactions with molecular species involved in lipid hydrolysis, such as bile salts, fatty acids, and calcium. These results have important implications for understanding the influence of dietary fibers on lipid digestion. The control of lipid digestibility within the gastrointestinal tract might be important for the development of reduced-calorie emulsion-based functional food products.

a b s t r a c tMedium methoxylated pectin (52% mol/mol, MMP) was isolated from banana passion fruit (Passiflora tripartita var. mollisima) by hot acidic extraction. The impact of MMP on lipid digestion was compared to that of commercial citrus pectins with high (71% mol/mol, HMP) and low (30% mol/mol, LMP) methoxylation degree. A static in vitro digestion model was used to elucidate the impact of pectin properties (methoxylation degree and molecular weight) on the gastrointestinal fate of emulsified lipids. A 2.0% (w/ w) corn oil-in-water emulsion stabilized with 0.2% (w/w) Tween 80 was prepared, mixed with 1.8% (w/w) pectin samples, and then subjected to the static in vitro digestion model (37 C): initial (pH 7.0); oral (pH 6.8, 10 min, mucin); gastric (pH 2.5, 120 min, pepsin); and intestinal (pH 7.0, 120 min, bile salts, and pancreatic lipase) phases. The impact of the three pectin samples on surface particle charge (z-potential), particle size distribution of lipid droplets, microstructure, rheology, and lipid digestion (free fatty acids (FFAs) released) was determined. The rate and extent of lipid digestion decreased with increasing simultaneously both the molecular weight and pectin methoxylation, with the FFAs released after 120 min of intestinal digestion being 47, 70, and 91% (w/w) for HMP, MMP, and LMP, respectively. These results have important implications for understanding the influence of pectin on lipid digestion. The control of lipid digestibility within the gastrointestinal tract might be important for the designing and development of novel functional foods to control bioactive release or to modulate satiety.

An in vitro gastrointestinal model consisting of oral, gastric, and intestinal phases was used to elucidate the impact of pectin on the digestion of emulsified lipids. Pectin reduced the extent of lipid digestion, which was attributed to its binding interactions with specific gastrointestinal components. The interaction of pectin with bile salts, lipase, CaCl2, and NaCl was therefore investigated by turbidity, microstructure, electrophoresis, and isothermal titration calorimetry (ITC) at pH 7.0 and 37 °C. ITC showed that the interaction of pectin was endothermic with bile salts, but exothermic with CaCl2, NaCl, and lipase. Electrophoresis, microstructure, and turbidity measurements showed that anionic pectin formed electrostatic complexes with calcium ions, which may have decreased lipid digestion due to increased lipid flocculation or microgel formation because this would reduce the surface area of lipid exposed to the lipase. This research provides valuable insights into the physicochemical and molecular mechanisms of the interaction of pectin with gastrointestinal components that may affect the rate and extent of lipid digestion.

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BACKGROUNDPotato frying quality is a complex trait influenced by sugar content in tubers. Good frying quality requires low content of reducing sugars to avoid the formation of dark pigments. Solanum tuberosum Group Phureja is a valuable genetic resource for breeding and for genetic studies. The sugar content after harvest was analyzed in a germplasm collection of Group Phureja to contribute to the understanding of the natural variation of this trait.RESULTSSucrose, glucose and fructose genotypic mean values ranged from 6.39 to 29.48 g kg−1 tuber dry weight (DW), from 0.46 to 28.04 g kg−1 tuber DW and from 0.29 to 27.23 g kg−1 tuber DW, respectively. Glucose/fructose and sucrose/reducing sugars ratios ranged from 1.01 to 6.67 mol mol−1 and from 0.15 to 7.78 mol mol−1, respectively. Five clusters of genotypes were recognized, three of them with few genotypes and extreme phenotypic values.CONCLUSIONSugar content showed a wide variation, representing the available variability useful for potato breeding. The results provide a quantitative approach to analyze the frying quality trait and are consistent with frying color. The analyzed germplasm presents extreme phenotypes, which will contribute to the understanding of the genetic basis of this trait. © 2016 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.