Study of potential alternatives to human digestive enzymes and prediction of digestibility and bioaccessibility of starch containing meals
[eng] This PhD thesis investigates the adaptation of two in vitro digestion methods for glycaemic index prediction and also outlines the effect of the macronutrients on the digestion of two starch sources. Potential alternatives to the main digestive human enzymes (α-amylase, pepsin, trypsin, lipase...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2023 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/688818 |
| Acceso en línea: | http://hdl.handle.net/10803/688818 |
| Access Level: | acceso abierto |
| Palabra clave: | in vitro digestion Carbohydrates Digestive enzymes Diabetis mellitus α-amylase 61 663/664 |
| Sumario: | [eng] This PhD thesis investigates the adaptation of two in vitro digestion methods for glycaemic index prediction and also outlines the effect of the macronutrients on the digestion of two starch sources. Potential alternatives to the main digestive human enzymes (α-amylase, pepsin, trypsin, lipase), which are expensive or not commercially available, have been studied based on their pH and temperature profiles to build a strong in vivo–in vitro correlation. This is important, as commonly used enzyme activity methods are often performed at non-physiological conditions such as 20°C, in the absence of digestive electrolytes and without considering the pH variations that occur during digestion. Therefore, the effect of digestive electrolytes on enzyme activity was also studied. Moreover, the storage stability of enzymatic solutions was studied and the maximum storage time at constant enzyme activity was defined. The alternative sources found in this study mimic the pH profile of the human enzymes at 37°C. The results demonstrated that, for the alternative sources, the effect of the temperature on the activity was similar to that of the human enzyme. In the presence of digestive electrolytes, the results revealed that each enzyme reacts differently. While α-amylase increased its activity in the presence of electrolytes, trypsin activity decreased and for lipase and pepsin no change in activity was found. Furthermore, enzymatic solutions can be used in in vitro digestion methods for a long period when stored at specific conditions (temperature, solvent). The digestion of carbohydrates and the effect of other macronutrients (protein and fat) was studied by determining the amount of glucose released from the different sources. The released glucose represents glucose available for intestinal absorption and in vivo, these glucose levels would impact blood glucose levels, thus being of special interest for products intended for patients with diabetes. The digestion of three foods (rice, potato, cocoa cream) was studied with two in vitro digestion methods (static and dynamic). With the aim of demonstrating that the selected in vitro digestion methods could provide reliable results, the measured glycaemic index (GI) was compared with reported values. The obtained results showed that the in vitro GI measured with both methods was slightly lower than the reported values. However, the reported GI for those meals was reached for most of the meals by applying a correction factor (with the exception of the cacao cream) when the dynamic digestion method was performed. To identify the digestion pattern of different carbohydrate sources, the digestion of two commercial starch sources (starch from rice and starch from potato) was studied with both methods (static and dynamic), the degree of hydrolysis (DH) and GI being measured. Then, the effect of the other macronutrients on the starch digestion was studied by adding protein (egg whites from chicken) or fat (olive oil or butter) to the starch. In general, clinical nutrition products for enteral route include the three macronutrients, thus, the digestion of meals that contains starch, protein and fat was also studied. The main differences obtained in the digestion of the different meals were due to their disintegration and solubilisation profiles, which would affect the time needed for the meal to be reached by the enzymes and subsequent enzymatic starch hydrolysis. Finally, the obtained results (DH and GI) with both in vitro digestion methods were compared, leading to the conclusion that there were no differences between the DH and GI obtained with the adapted static or adapted dynamic digestion methods. |
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