In situ interaction of pea peptides and bile salts under in vitro digestion: Potential impact on lipolysis.

The present work evaluated how a native pea protein isolate (PPI) affects the key roles carried out by bile salts (BS) in lipid digestion by means of the in vitro static INFOGEST protocol. Two gastric residence times were evaluated (10 and 60 min), and then the peptides obtained (GPPP) were mixed with BS at physiological concentration in simulated intestinal fluid to understand how they interact with BS both at the bulk and at the interface. Both GPPP give rise to a film with a predominant viscous character that does not constitute a barrier to the penetration of BS, but interact with BS in the bulk duodenal fluid. When the peptides flushing from the stomach after the different gastric residence times undergo duodenal digestion, it was found that for the longer gastric residence time the percentage of soluble fraction in the duodenal phase, that perform synergistically with BS micelles, was twice that of the lower residence time, leading to an increase in the solubilization of oleic acid. These results finally lead to a greater extent of lipolysis of olive oil emulsions. This work demonstrates the usefulness of in vitro models as a starting point to study the influence of gastric residence time of pea protein on its interaction with BS, affecting lipolysis. Pea proteins were shown to be effective emulsifiers that synergistically perform with BS improving the release and bioaccessibility of bioactive lipids as olive oil.

Solubilization of lipolysis products in mixed micelles is enhanced in presence of bile salts and Tween 80 as revealed by a model study (oleic acid) and emulsified chia-oil.

In the last few decades, there has been a growing interest in understanding the mechanisms involved in lipid digestion with the purpose of developing strategies to control this complex physiological process. Bile salts (BS) are natural bio-surfactants that play crucial functions in this process and may represent a key strategy to modulate the lipolysis. One of the main functions is the removal of lipolysis products present at the interface of lipid droplets by solubilizing them in BS micelles, thus avoiding the reaction inhibition. However, there are few studies that analyzed the effects that could have the emulsion components on the solubilization capacity of BS micelles. Thus, the main purpose of the present work was to evaluate the impact of a typical food emulsifier (Tween 80) on the fatty acid (FA) solubilization capacity of BS micelles by using a method recently developed, involving a combination of turbidity and dynamic light scattering (DLS) determinations. As FA solubilization into BS micelles may strongly affect the kinetics of lipolysis, the lipolysis of T80-stabilized oil-in-water (O/W) emulsions was also studied. The results showed that a higher concentration of the emulsifier in the duodenal medium causes the lipolysis rate to be maximum for a longer time. The mechanism involved could be the contribution of T80 to increase the solubilization of FA (and possibly other products of the lipolysis) in the duodenal medium, consequently affecting the potential bioavailability of fatty acids.

A new methodology to assess the solubility of fatty acids: Impact of food emulsifiers.

In food formulations, lipids are normally incorporated as emulsions stabilized by different types of emulsifiers. The emulsifiers can affect fatty acid (FA) solubilization as they can interact with FA. The main purpose of the present work is the development of a methodology to evaluate the FA solubilization in an aqueous medium in the absence and presence of exogenous emulsifiers. To this end, a combination of turbidimetry, oiling off and dynamic light scattering (DLS) was used. The FA solubility, as well as its supramolecular assemblies, were determined by analyzing the changes in the turbidity profile and the corresponding size of particles obtained by DLS. Oleic acid (OA) was used as a model FA and a simulated intestinal fluid (SIF) as the aqueous phase. Emulsifiers of low (Tween 80) and high (protein and polysaccharide) molecular weight were tested. Tween 80 was the only emulsifier that improved OA solubilization, whereas the macromolecules only affected the supramolecular structure that OA adopted, being the structure of these assemblies governed by the emulsifier nature.

Studies on the interactions between bile salts and food emulsifiers under in vitro duodenal digestion conditions to evaluate their bile salt binding potential.

During the last decade a special interest has been focused on studying the relationship between the composition and structure of emulsions and the extent of lipolysis, driven by the necessity of modulate lipid digestion to decrease or delay fats absorption or increase healthy fat nutrients bioavailability. Because bile salts (BS) play a crucial role in lipids metabolism, understanding how typical food emulsifiers affect the structures of BS under duodenal conditions, can aid to further understand how to control lipids digestion. In the present work the BS-binding capacity of three emulsifiers (Lecithin, Tween 80 and ß-lactoglobulin) was studied under duodenal conditions. The combination of several techniques (DLS, TEM, ζ-potential and conductivity) allowed the characterization of molecular assemblies resulting from the interactions, as modulated by the relative amounts of BS and emulsifiers in solution.

Comparative interfacial in vitro digestion of protein and polysaccharide oil/water films.

The behaviour of proteins (ß-lactoglobulin (ßlg) and soy protein isolate (SPI)) and a surface active polysaccharide (hydroxypropylmethylcellulose, HPMC) o/w interfacial films under simulated gastrointestinal conditions using the interfacial tensiometer Octopus were compared and related to the performance of the emulsions (using the same emulsifiers) under in vitro digestion. The evolution of interfacial tension (γ) was used to investigate the effect of gastrointestinal fluids on o/w interfacial films. Clear differences were observed among these emulsifiers. During the gastric phase, HPMC showed the lowest change in γ values as compared to protein films. The most important changes occurred during the intestinal stage where it was observed an important decrease of γ associated with the rapid penetration of BS, followed by a lower rate of decrease attributable to the accumulation of FFA at the interface. In the last stage, the subphase was exchanged by buffer alone, to remove the reversibly adsorbed digestion products. SPI formed the most resistant interface to the remotion of digestion products, followed by HPMC and finally by ßlg. The results agree with the degree of lipolysis reported for the emulsions stabilized by these emulsifiers, which suggest that lipid digestion could be modulated by the ability of emulsifiers to prevent the BS activity (to adsorb at the O/W interface or remove the inhibitory digestion products from the interface). Thus, emulsifiers-BS interactions appears as a key factor in controlling the lipolysis.