In vitro digestion behavior of complex formulations for clinical nutrition applications based on model systems

Abstract

[eng] In vitro digestion methods simulating digestion processes are widely used to study the gastro-intestinal behavior of food or pharmaceuticals. In vitro digestion methods typically include the oral, gastric, and small intestinal phases, and occasionally the large intestinal phase. These methods try to mimic physiological conditions in vivo, taking into account the presence of digestive enzymes and their concentrations, pH, digestion time, and temperature, among other factors. In vitro digestion methods have been used to address such diverse scientific questions as the digestibility and bio-accessibility of pharmaceuticals, mycotoxins, and macronutrients such as proteins, carbohydrates, and lipids. Bio-accessibility provides an indication for the maximum of bioavailability via the oral route and is an important parameter. In this master’s thesis two different methods were studied: 1) Static digestion method: Static in vitro digestion models use sequential exposure to simulate digestion in different compartments (mouth, stomach, and intestine). During each step, the substrate is incubated for a specific time with the appropriate simulated digestive fluids. The pH is generally maintained at a fixed value by using a pH-stat or a buffer. 2) Dynamic digestion method: Dynamic in vitro digestion models reproduce the gradual transit of ingested compounds through the gastrointestinal tract more. The system reproduces the temperature, pH changes, gastric emptying, addition of simulated fluids and dialysis of digestion end products. To carry out this thesis three different carbohydrate sources were selected, Maltodextrin DE 11 – 16, Tapioca Dextrin and Modified starch, and all of them are starch derivatives. To carry out different studies like the study of digestibility, bio-accessibility, volume effect, matrix effect, etc. the static and dynamic digestion methods were used. The obtained results show that Maltodextrin DE 11 – 16 liberates more amount of glucose than Tapioca Dextrin and Modified starch and the results also show the dependency between length chain and digestibility. The comparison of the static and dynamic digestion method show that there are no big differences between the recovery obtained from each method. The obtained results of the study of volume effect suggest that is possible use smaller volumes with static digestion method, which is important to save resources. And the results obtained with the study of matrix effect indicate that the matrixes used do not affect the digestibility of Tapioca Dextrin and the pre-treatment of the meal favors the release of glucose. The objectives of this thesis are the following: 1) Study of digestibility and bio-accessibility of three different carbohydrate sources: this is of interest because with this study the amount of released glucose from the different sources (in a time-dependent manner) can be obtained. The released glucose represents available glucose for intestinal absorption. In vivo, this glucose levels would impact on the blood glucose levels and is of special interest for products intended for patients with diabetes.2) Study matrix effect: clinical nutrition products for enteral root are rarely including only polysaccharides, but also contain macro- and micronutrients. In those complex mixtures it is most likely that matrix could affect digestibility of the contained polysaccharides. For this reason, the effect of different matrixes was also studied. 3) Comparison between two different digestion methods: this part of the thesis should reveal advantages and drawbacks of each method, and, those results should serve as the basis of decision for the application of each system in future. 4) Study volume effect: this part of the study is focused on the used static digestion method and intents to determine the impact of the used reaction volume and to explore the potential to save resources.