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[Display omitted] • Commercial protein isolates generally show limited functional properties. • High pressure homogenization, pH and temperature may improve protein functionalities. • Similar protein (micro)structure not necessarily exhibits similar functionality. • Increasing pressure intensities enhanced protein solubility and digestion kinetics. • Temperature and pH-shifting slightly improved solubility and digestibility. In this work, dispersions were prepared with commercial pea protein isolate (PPI) and subjected to different (i) high pressure homogenization (HPH) intensities (0 – 200 MPa) (room temperature, pH 7) or (ii) environmental conditions (60 °C, pH 7 or pH 12) to generate dispersions with distinct protein molecular and microstructural characteristics, impacting protein solubility. Besides, protein digestion was analyzed following the static INFOGEST in vitro digestion protocol. Generally, increasing pressure of the homogenization treatment was linked with decreasing particle sizes and enhanced protein digestion. More specifically, the dispersion that did not undergo HPH (0 MPa) as well as the dispersion treated at 60 °C, pH 7, had highly similar microstructures, consisting of large irregular particles (10 – 500 µm) with shell-like structures, and exhibited low solubility (around 15 % and 28 %, respectively), which resulted in limited proteolysis (35 % and 42 %, respectively). In contrast, the dispersion subjected to HPH at 100 MPa and the dispersion treated at 60 °C, pH 12 also had similar microstructures with small and homogeneous particles (<1 µm), and exhibited relatively good solubility (54 % and 31 %, respectively), which led to enhanced protein digestion levels (87 % and 74 %, respectively). This study highlights the potential of food processing on macronutrient (micro)structure and further gastrointestinal stability and functionality. [ABSTRACT FROM AUTHOR]

Studying the impact of the protein accessibility level on macronutrient digestion kinetics is highly relevant since it can be utilised to achieve specific digestive responses. In this work, plant-based shakes containing protein with two distinct levels of accessibility were designed. On the one hand, free, non-entrapped protein was added, being pea protein isolate (PPI) dispersions further stabilized by high pressure homogenisation (HPH). On the other hand, individual cotyledon pea cell (IPC) suspensions were considered as source of naturally entrapped protein. The two structural protein organisations were blended. The ratio of protein derived from PPI and IPC was modified as part of this work, yet, the total protein content was kept constant at 6%. The results showed that increasing the IPC content (5% versus 15%) significantly decreased protein as well as starch digestion kinetics. For instance, protein extent decreased from 75% to 68%, and starch extent decreased from 63% to 47%. Moreover, shakes having greater protein digestibility presented also greater starch digestibility which highlights the important role of the protein matrix in modulating starch digestion as part of pulse cells. Finally, introducing individual pea cells in the shakes retarded lipolysis kinetics. This study showed that altering (the ratio of) protein accessibility level in plant-based shakes is a manner to modulate macronutrient digestion kinetics. This is a promising strategy to target specific digestion functionalities. [Display omitted] • Cellular protein as part of pea cells affected amylolysis, proteolysis, and lipolysis. • Ratio free/entrapped protein affected macronutrient digestion kinetics. • Overall proteolysis kinetics depend on the amount of 'entrapped' protein. • Greater protein digestibility goes hand in hand with greater starch digestibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Impact of processing conditions was studied on plant-based shakes. • Processing affected microstructure, and lipid and protein digestion kinetics. • High pressure homogenisation improved protein solubility in plant-based shakes. • The presence and size of protein aggregates affected lipid digestion kinetics. • Oil droplet size did not influence protein digestion kinetics. In this work, plant-based shakes were prepared (5% oil, 6% protein, 1% lecithin, 88% water) (w/w) using two processing techniques (i) only mixing versus (ii) mixing followed by high pressure homogenisation, as well as two processing sequences (i) adding all ingredients together versus (ii) stepwise addition of ingredients. Shakes only mixed consisted of large, irregular particles (1–100 µm). Eventually, this resulted in a relatively low lipid and protein digestion extent after 2 h of gastric pre-digestion (9% and < 1%, respectively). In contrast, shakes that were subjected to high pressure homogenisation displayed small, homogeneous particles (<10 µm). Besides, lipids and proteins were digested to a high extent in the stomach (40% and 10%, respectively). The small intestinal digestion kinetics indicated a significant impact of proteins on lipid digestion kinetics but no significant effect of lipids on protein digestion kinetics. The results highlighted the relevance of food processing on macronutrient (micro)structure and further gastrointestinal functionality. [ABSTRACT FROM AUTHOR]

We studied the effect of evolving from static in vitro digestion conditions towards the gradual addition of essential digestive compounds for lipid digestion. Two oil-in-water emulsions were considered: a low (5% w/w) and high (20% w/w) triolein-based emulsion with identical surfactant-to-oil ratio (0.2). Emulsions were subjected to in vitro static digestion conditions or gradual gastric lipase addition, gradual pancreatic lipase addition, and/or gradual bile salt addition. For these three latter cases, similar amounts of gastric/pancreatic lipase and/or bile salts were provided as in the static case, however divided over 4 doses added during the first 30 min of each digestive phase. For the low-lipid emulsion, gradually adding lipases and bile salts did not significantly affect lipolysis kinetics. This can be related to the sufficient amounts of digestive compounds present even in the smallest initial dose. For the high-lipid emulsion, the gradual addition of bile salts significantly reduced the lipolysis rate. Bile salts are essential to remove lipid digestion products from the interface and thus allow the continuation of the lipid digestion process at the interface. Oppositely, the lipolysis extent after 2 h of small intestinal phase was not significantly influenced by the digestion approach. This is again explained by the simple nature of the emulsions studied and the excess of lipase even in the smallest initial dose. Overall, this work showed that evolving towards more (semi-)dynamic digestion conditions can impact (lipid) digestion kinetics, even for relatively simple food compositions, and is of interest to obtain more physiological relevant digestion kinetics. [Display omitted] • Lipid digestion of simple emulsions was simulated in a stepwise manner • Oil concentration impacts the extent of lipid digestion • Emulsion stability plays a key role in the lipid digestion process • The amount of bile salts influences the lipolysis rate • Semi-dynamic digestion conditions can impact (lipid) digestion kinetics [ABSTRACT FROM AUTHOR]

In the past decades, the great interest in food digestion research led to a wide array of in vitro digestion (IVD) methods. Each of these methods have the potential of providing specific valuable scientific insights in digestion mechanisms and the rational structural design of foods. This review paper outlines important transitions in recent IVD research and formulates important considerations relevant for the set-up of future in vitro experiments, especially in the context of rational food digestion design. Important transitions are discussed, including the importance of kinetic experiments for macronutrient digestion, the relevance of the transition towards more complex (semi)-dynamic digestion conditions, the shift from single nutrients in simplified systems towards real foods and meals, and the emerging trend to adapt methods to mimic the gastrointestinal (GI) tract of specific populations. Notwithstanding the recent shift towards more complex IVD methods, the possibilities and advantages of more simple digestion methods should not be overlooked for mechanistic understanding or for sample screening purposes. Since the information retrieved from a simulation experiment depends on the applied conditions, the appropriate in vitro protocol should be chosen depending on the research question. In this context, the harmonization of digestion methods such as the standardized INFOGEST protocols can play a notable role in food digestion research and the development of tailored foods for all different strata of the population. • Strategic choices to design relevant in vitro digestion experiments are outlined. • Selected IVD method affects generated data and the learning outcomes. • IVD research evolves from static to semi-dynamic and dynamic approaches. • Kinetic approaches reveal nutrient hydrolysis patterns. • Research focus shifts from simple systems to real foods and specific populations. [ABSTRACT FROM AUTHOR]

• SEC delivers in-depth insight into proteolysis patterns complementary to OPA. • Bioaccesible protein release reached a plateau during the small intestinal phase. • Proteolysis in the insoluble (inaccessible) fraction proceeded throughout digestion. • Pulse microstructure dictated protein hydrolysis and solubilization kinetics. • M w evolution in insoluble fraction depended on pulse type and microstructure. Cellular pulse ingredients are increasingly being studied but little knowledge on their proteolysis patterns upon digestion is available. This study investigated a size exclusion chromatography (SEC) approach to study in vitro protein digestion in chickpea and lentil powders, providing novel insights into proteolysis kinetics and the evolution of molecular weight distributions in the (solubilized) supernatant and (non-solubilized) pellet fractions. For the quantification of proteolysis, SEC-based analysis was compared to the commonly used OPA (o -phthaldialdehyde) approach and nitrogen solubilized upon digestion, leading to highly correlated proteolysis kinetics. Generally, all approaches confirmed that microstructure dictated proteolysis kinetics. However, SEC analysis delivered an additional level of molecular insight. For the first time, SEC revealed that while bioaccessible fractions reached a plateau in the small intestinal phase (around 45–60 min), proteolysis continued in the pellet, forming smaller but mostly insoluble peptides. SEC elutograms showed pulse-specific proteolysis patterns, unidentified using other current state-of-the-art methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Semi-dynamic models allow to mimic certain physiological relevant digestion factors. • A multireactor system was introduced to simulate semi-dynamic digestion conditions. • The "MuReDi" system allows to produce repeatable data for two distinct food types. • Digestion kinetics alter when changing from static to semi-dynamic conditions. • Semi-dynamic digestion should give more physiologically relevant digestion kinetics. In this work, a multireactor system to study digestion (MuReDi) kinetics is introduced. For this, a custom-made automated system with four independent syringe pumps (BioXplorer 100, H.E.L Group) was acquired. This system consists of multiple, small-scale reactors allowing to study digestion as a function of time and thus to determine digestion kinetics. The different digestion conditions used in the oral, gastric, and small intestinal phase were based on the digestion protocols published by the INFOGEST consortium. We showed that the minimum working volume of a reactor is 30 mL. Besides, repeatability of the digestion kinetics was shown for two food systems: a liquid Ensure® Plus Vanilla drink, and a solid, cooked lentil sample. When comparing static digestion kinetics with semi-dynamic ones, a significantly different digestion pattern was observed. In the static case, a relatively fast hydrolysis rate was observed until a clear plateau was reached. Oppositely, for the semi-dynamic case, a delayed start of the hydrolysis process was noticed. In the gastric phase, this was explained by the decreasing pH and the large pH dependency of pepsin activity. In the small intestine, the lag phase was relatively shorter, yet clearly present. Here we related it to the gradual enzyme (and bile salt) secretion that had to diffuse towards the substrate before hydrolysis could start. Generally, this work showed that the MuReDi system could be used to perform a semi-dynamic digestion approach which largely impacted the overall digestion kinetics. This is important to consider in future in vitro food digestion simulation work to come closer to physiologically relevant digestion kinetics. [ABSTRACT FROM AUTHOR]