Modern dietary habits have created the need for the design and production of functional foods enriched in bioactive compounds for a healthy lifestyle. However, the fate of many of these bioactive compounds in the human gastrointestinal (GI) tract has not been thoroughly investigated. Thus, in the present study, the bioaccessibility of omega-3 fatty acids was examined. To that end, different foods and supplements underwent simulated digestion following the INFOGEST protocol. The selected samples were foods rich in omega-3 fatty acids both in free and bound form—i.e., dietary fish oil supplements, heat-treated fish, and eggs enriched with omega-3 fatty acids. The oxidation of polyunsaturated fatty acids (PUFAs) was measured at each stage of the digestion process using peroxide value (PV) and TBARS and by quantifying individual omega-3 fatty acids using a gas chromatograph with flame ionization detector (GC-FID). The final bioaccessibility values of omega-3 fatty acids were determined. Changes in the quantity of mono-saturated fatty acids (MUFAs) and saturated fatty acids (SFAs) were recorded as well. The results indicated a profound oxidation of omega-3 fatty acids, giving rise to both primary and secondary oxidation products. Additionally, stomach conditions seemed to exert the most significant effect on the oxidation of PUFAs during digestion, significantly decreasing their bioaccessibility. The oxidation rate of each fatty acid was found to be strongly correlated with its initial concentration. Finally, the oxidation pattern was found to be different for each matrix and emulsified lipids seemed to be better protected than non-emulsified lipids. It is concluded that digestion has a profound negative effect on omega-3 bioaccessibility and therefore there is a need for improved protective mechanisms.

Vitamin D₃ deficiency is a global phenomenon, which can be managed with supplementation and food fortification. However, vitamin D₃ bioaccessibility may depend on factors such as matrix composition and interactions throughout the gastrointestinal (GI) tract. This research focused on the effect of different matrices on vitamin D₃ content during digestion, as well as the effect of pH on its bioaccessibility. The INFOGEST protocol was employed to simulate digestion. Three different types of commercial supplements, two foods naturally rich in vitamin D₃, and three fortified foods were investigated. High-Performance Liquid Chromatography was used to determine the initial vitamin D₃ content in the supplements and foods, as well as after each digestion stage. The results indicate that the foods exhibited higher bioaccessibility indices compared to the supplements and a higher percentage retention at the end of the gastric phase. The pH study revealed a positive correlation between an increased gastric pH and the corresponding content of vitamin D₃. Interestingly, exposing the matrix to a low pH during the gastric phase resulted in an increased intestinal content of D₃. Vitamin D₃ is more bioaccessible from foods than supplements, and its bioaccessibility is susceptible to changes in gastric pH. Fasting conditions (i.e., gastric pH = 1) enhance the vitamin’s bioaccessibility.

Even though the functional food market has rapidly increased in recent years, the links between bioactive-rich formulations and consumers’ health benefit are not fully established, mainly because of insufficient consideration of food matrix effects. This review provides a comprehensive and integrated evaluation of how food matrix properties (structural and physicochemical) affect the bioaccessibility of plant bioactive compounds. Unlike many reviews that focus on a single nutrient approach, we highlight quantitative evidence of how bioaccessibility can be affected by matrix properties, illustrating the interactions between main food components (lipids, proteins, dietary fiber and minerals). This review integrates fragmented information among different areas of food and nutrition sciences, i.e., food structure, gastrointestinal science, mineral chemistry, protein chemistry, providing a holistic framework for Quality by Design (QbD) functional food development. Synergisms and antagonistic behaviors, threshold effects, and concentration-dependent behaviors are analyzed comparatively for the most common plant-derived bioactives, such as polyphenols, carotenoids, curcuminoids and minerals (iron, zinc and calcium). We propose a matrix-informed optimization as a prerequisite for credible health claims and sustainable plant-based nutrition strategies. This can ultimately serve as a foundation for next-generation functional food development based on bioaccessibility, supporting the central argument that functional food development should move from composition-based fortification to bioaccessibility-based matrix engineering.

Vitamin D3 deficiency is a global phenomenon, which can be coped with supplementation and food fortification. However, vitamin D3 bioaccessibility may depend on factors, such as matrix composition and interactions throughout the gastrointestinal tract. This research focused on the effect of different matrices on vitamin D3 content during digestion, and the effect of pH on its bioaccessibility. The INFOGEST protocol was employed to simulate digestion. Three different types of commercial supplements, two foods naturally rich in vitamin D3, and three fortified foods were investigated. High-Performance Liquid Chromatography was used to determine the vitamin D3 initial content in supplements and foods, as well as after each digestion stage. Results indicated that foods exhibited higher bioaccessibility indices compared to supplements, and a higher percentage retention at the end of the gastric phase. The pH study revealed a positive correlation between increased gastric pH and the corresponding content of vitamin D3. Interestingly, exposing the matrix to low pH during the gastric phase resulted in an increased intestinal content of D3. Vitamin D3 is more bioaccessible from foods than supplements, and its bioaccessibility is susceptible to changes in gastric pH. Fasting conditions (i.e. gastric pH=1) enhances vitamin’s bioaccessibility.

Vitamin D3 concentration behavior during intestinal digestion is essential in identifying dependent parameters in order to manufacture carrier matrices with improved bioaccessibility. In this study, gastric lipolysis and vitamin D3 concentration during intestinal in vitro digestion of emulsions (INFOGEST protocol), along with its subsequent bioaccessibility index (BI) were determined for different concentrations of the vitamin. The results were then used to construct a mathematical model to estimate the behavior of different concentrations of the vitamin, using parameter estimation. The governing phenomena used to simulate the digestion were vitamin D3 release from the matrix, lipolysis and micellization. Kinetic modelling of the concentration during intestinal digestion was performed using two approaches, one simplified and one more complex, which tries to identify the physicochemical interactions during intestinal digestion. Our results indicate that vitamin D3 bioaccessibility depends on some extent on the initial concentration present in the matrix (average BI 0.69±0.01, 0.53±0.02, 0.53±0.01, 0.56±0.03, 0.61±0.01 for 10, 25, 50, 75 and 100 μg/ml initial concentration, respectively), while its profile during intestinal digestion is independent of initial concentration level. Concerning the kinetic modelling, the second approach showed better fit in the data (MAPE 12.3±1.7%) and better predictive performance (MAPE 16.9±9.6%). Parameter distribution showed variability in the identifiability of the parameters, which may constitute a limiting factor in predictive accuracy. These results indicate that the model is suitable for predicting vitamin D3 concentration behavior during intestinal digestion, though with some limitations depending on the context of application.