The harmonized INFOGEST in vitro digestion method: From knowledge to action

Recent progress in the preparation of bioactive peptides using simulated gastrointestinal digestion processes

Bioactive peptides (BAPs) represent a unique class of peptides known for their extensive physiological functions and their role in enhancing human health. In recent decades, owing to their notable biological attributes such as antioxidant, antihypertensive, antidiabetic, and anti-inflammatory activities, BAPs have received considerable attention. Simulated gastrointestinal digestion (SGD) is a technique designed to mimic physiological conditions by adjusting factors such as digestive enzymes and their concentrations, pH levels, digestion duration, and salt content. Initially established for analyzing the gastrointestinal processing of foods or their constituents, SGD has recently become a preferred method for generating BAPs. The BAPs produced via SGD often exhibit superior biological activity and stability compared with those of BAPs prepared via other methods. This review offers a comprehensive examination of the recent advancements in BAP production from foods via SGD, addressing the challenges of the method and outlining prospective directions for further investigation.

Digested casein phosphopeptides impact intestinal calcium transport in vitro

Calcium is the most abundant mineral in the human body and is involved in critical physiological and cellular processes. It is essential for the development, maintenance, and integrity of bone tissue throughout life. Identifying new natural food-grade chelating agents to improve calcium uptake is of increasing interest. Casein phosphopeptides (CPPs), highly phosphorylated peptides obtained after enzymatic hydrolysis of caseins, represent promising calcium-chelating candidates. The aim of this study was to investigate, using cell culture models, the ability of a digested milk matrix enriched in CPPs to regulate calcium transport through the intestinal barrier and elucidate the involved mechanisms. To this end, a CPP-preparation underwent in vitro static digestion and was subsequently incubated with an intestinal barrier model to monitor calcium uptake and transport. Our results demonstrated that the digested CPP preparation enhanced the trans-epithelial calcium transport via paracellular pathways and that CPPs, identified by peptidomics, crossed the intestinal barrier in the same time.

Nanosilver-based materials as feed additives: Evaluation of their transformations along in vitro gastrointestinal digestion in pigs and chickens by using an ICP-MS based analytical platform

The use of a new nanomaterial in the feed chain requires a risk assessment that involves in vitro gastrointestinal digestions to predict its degradation and oral exposure to nanoparticles. In this study, a nanosilver-based material was incorporated into pig and chicken feed as a growth-promoting additive and subjected to the corresponding in vitro gastrointestinal digestions. An inductively coupled plasma mass spectroscopy (ICP-MS) analytical platform was used to obtain information about the silver released in the different digestion phases. It included conventional ICP-MS for total silver determination, but also single particle ICP-MS and coupling to hydrodynamic chromatography for detection of dissolved and particulate silver. The bioaccessible fraction in the intestinal phase accounted for 8-13% of the total silver, mainly in the form of dissolved Ag(I) species, with less than 0.1% as silver-containing particles. Despite the additive behaving differently in pig and chicken digestions, the feed matrix played a relevant role in the fate of the silver.

Real-time tracking of the adsorption of bovine serum albumin on lipid layer and its effect on lipolysis by optical interferometry

The model proteins bovine serum albumin (BSA) and lipid layer were used to study the effect of proteins on lipolysis. A lipid layer with an interference effect was constructed by loading the triolein into the silica colloidal crystal (SCC) film. The ordered porous layer interferometry (OPLI) system was used to track the changes in lipid layer mass caused by lipase hydrolysis to achieve real-time lipolysis detection. The real-time tracking of the adsorption of BSA on the lipid layer by converting the migration of interference fringes caused by the change of the lipid layer into the optical thickness change (ΔOT). The effect of BSA on the early and late stages of lipolysis was studied, and lipases containing 5 mg/mL BSA degraded the lipid layer 3.4 times faster than lipases containing 0.1 mg/mL BSA in the later stages. This study deepens the understanding of protein-lipid interactions in complex digestive environments.

A2 milk: Bioaccessibility of essential minerals and the release of amino groups under static in vitro digestion conditions

Alternative milk products such as A2 milk are gaining popular stand within consumer market, for their healthy profile and expected greater digestibility characteristics. However, total mineral content and its bioaccessible profile have lacked in studies through the years, even more because of their relevance in public health. The present study aimed to evaluate the mineral profile of commercial A2 bovine milk (AT) and estimate the bioaccessibility of calcium, phosphorus and magnesium using the INFOGEST protocol. Non-A2 samples (NAT) were evaluated for comparison purpose. The determination of Ca, Mg, Na and K was performed by FAAS and total P was quantified by colorimetric method. Total protein content was determined by Kjeldahl method. Free amino acids were quantified by OPA method along the in vitro digestion stages. Total content of Ca, Na and P exhibited equivalent results between samples, although A2 milk showed elevated levels of total Mg and K in the analyzed batches. AT showed protein content equivalent to NAT. In addition, levels of free NH2 were observed 2 times higher in AT, during the first hour of pancreatic phase in the intestinal digestion. Bioaccessibility of Ca showed equivalent percentages for AT (12-42 %) and NAT (10-39 %). The observed low values were possibly derived from interferences with saturated fatty acids and standardized electrolytes during digestion. Similar amounts of bioaccessible Mg were found for all milk samples (35-97 %), while A2 samples evidenced percentages of bioaccessible P exceeding 60 % across the three batches. Despite the health benefits associated to A2 milk, the study did not evidence clear distinction from non-A2 milk in terms of enhanced essential mineral solubility in digestive tract simulation, considering the association of greater digestibility expected for A2 milk.

Current advances for in vitro protein digestibility

Protein is an essential macronutrient in our diet, source of nitrogen and essential amino acids, but the biological utilization of dietary protein depends on its digestibility and the absorption of amino acids and peptides in the gastrointestinal tract. The methods to define the amount and the quality of protein to meet human nutritional needs, such as the Digestible Indispensable Amino Acid Score (DIAAS), require the use of animal models or human studies. These in vivo methods are the reference in protein quality evaluation, but they are expensive and long-lasting procedures with significant ethical restrictions. Therefore, the development of rapid, reproducible and in vitro digestion methods validated with in vivo data is an old demand. This review describes the challenges of the in vitro digestion methods in the evaluation of the protein nutritional quality. In addition to the technical difficulties to simulate the complex and adaptable processes of digestion and absorption, these methods are affected by similar limitations as the in vivo procedures, i.e., analytical techniques to accurately determine bioavailable amino acids and the contribution of the endogenous nitrogen. The in vitro methods used for the evaluation of protein digestibility, with special attention on those showing comparative data, are revised, emphasizing their pros and cons. The internationally harmonized digestion protocol proposed by the INFOGEST network is being adapted to evaluate protein and amino acid digestibility. The inter-laboratory reproducibility of this protocol was demonstrated for dairy products. The in vivo/in vitro comparability results obtained to date with this protocol for several plant and animal sources are promising, but it requires an extensive validation with a wider range of foods and substrates with known in vivo digestibility. These in vitro methods will probably not be applicable to all foods, and therefore, it is important to identify their limitations, not to elude their use, but to apply them within the limits, by using the appropriate standards and references, and always as a complementary tool to in vivo tests to reduce their number.

In vitro protein digestibility to replace in vivo digestibility for purposes of nutrient content claim substantiation in North America's context

The reliance by North American regulatory authorities on in vivo rodent bioassays-Protein Correct-Amino Acid Score (PDCAAS) in the U.S. and Protein Efficiency Ratio (PER) in Canada-to measure the protein quality for protein content claim substantiation represents a major barrier for innovation in the development and marketing of protein foods. Although FAO in 2013 proposed a new method (Digestible Indispensable Amino Acid Score, DIAAS), it is still not used for protein content claim substantiation in any jurisdiction. Together with public health efforts to increase the consumption of plant-based foods, removing hurdles is key to incentivizing the food industry to measure protein digestibility in making food formulation decisions as well as in claiming protein content on product labels. To address this issue, a pathway has been proposed to position alternative methods for in vitro protein digestibility in collaborative studies to generate the data necessary for method approval by a certifying body. The latter is critical to the potential recognition of these methods by both Health Canada and the US FDA. The purpose of this article is to briefly summarize the state-of-the-art in the field, to inform the research community of next steps, and to describe the path engaging collaborative laboratories in a proficiency test as the first step in moving forward toward acceptance of in vitro digestibility methods. Throughout, a consultative and iterative process will be utilized to ensure the program goals are met. Success will be achieved when the proposed path results in the acceptance of an in vitro methods for protein digestibility used for PDCAAS determinations, which will enable increased protein analyses and improved nutrition labeling of protein foods.

In Vitro Digestion of Polyphenolic Compounds and the Antioxidant Activity of Acorn Flour and Pasta Enriched with Acorn Flour

Acorn flour is a rich source of nutrients and is beneficial to human health due to, among other things, its low glycemic index and polyphenol content. In order to obtain more accurate data on the levels and activities of the substances tested after ingestion and digestion, it may be beneficial to use a simulated in vitro digestion method. Therefore, the objective of the present study was to elucidate the content of polyphenols, individual phenolic acids, flavonoids and antiradical properties of acorn flour and pasta enriched with acorn flour before and after simulated in vitro gastrointestinal digestion. The results indicate that the total polyphenol content (TPC), flavonoid content and radical scavenging activity exhibited an increasing trend following the initial digestion stage and a decreasing trend following the second stage. Nevertheless, the levels of phenolic acids demonstrated an increase in both digestion phases. The digestion processes of polyphenols in acorn flour differ significantly from those in pasta. In the case of pasta, total polyphenols, phenolic acids and flavonoids, as well as free radical scavenging properties, demonstrated a decreasing trend following each digestion stage.

Globe Artichoke (Cynara scolymus L.) By-Products in Food Applications: Functional and Biological Properties

Globe artichoke (Cynara cardunculus var. scolymus L.) is widely cultivated in the Mediterranean area and Italy is one of the largest producers. A great issue is represented by its high amount of by-product, mainly consisting of external bracts and stems, but also of residual leaves, stalks, roots, and seeds. Artichoke by-products are rich in nutrients (carbohydrates and proteins) and bioactive compounds (polyphenols and terpenes) and represent potential ingredients for foodstuffs, functional foods, and food supplements, due to their functional and biological properties. In fact, artichoke by-products' components exhibit many beneficial effects, such as dyspeptic, prebiotic, antioxidant, anti-inflammatory, antiglycative, antimicrobial, anticarcinogenic, and hypolipidemic properties. Therefore, they can be considered potential food ingredients useful in reducing the risk of developing metabolic and age-related disorders. This work summarizes the economic and environmental impact of the recovery and valorization of artichoke by-products, focusing on rheological, physical, and biological properties of the different components present in each by-product and their different food applications.

Encapsulation of short-chain bioactive peptides (BAPs) for gastrointestinal delivery: a review

The majority of known peptides with high bioactivity (BAPs) such as antihypertensive, antidiabetic, antioxidant, hypocholesterolemic, anti-inflammatory and antimicrobial actions, are short-chain sequences of less than ten amino acids. These short-chain BAPs of varying natural and synthetic origin must be bioaccessible to be capable of being adsorbed systemically upon oral administration to show their full range of bioactivity. However, in general, in vitro and in vivo studies have shown that gastrointestinal digestion reduces BAPs bioactivity unless they are protected from degradation by encapsulation. This review gives a critical analysis of short-chain BAP encapsulation and performance with regard to the oral delivery route. In particular, it focuses on short-chain BAPs with antihypertensive and antidiabetic activity and encapsulation methods via nanoparticles and microparticles. Also addressed are the different wall materials used to form these particles and their associated payloads and release kinetics, along with the current challenges and a perspective of the future applications of these systems.

Assessing the impact of insect protein sources on intestinal health and disease: insights from human ex vivo and rat in vivo models

The exploration of edible insects, specifically Alphitobius diaperinus and Tenebrio molitor, as sustainable sources of protein for human consumption is an emerging field. However, research into their effects on intestinal health, especially in relation to inflammation and permeability, remains limited. Using ex vivo and in vivo models of intestinal health and disease, in this study we assess the impact of the above insects on intestinal function by focusing on inflammation, barrier dysfunction and morphological changes. Initially, human intestinal explants were exposed to in vitro-digested extracts of these insects, almond and beef. Immune secretome analysis showed that the inflammatory response to insect-treated samples was comparatively lower than it was for samples exposed to almond and beef. Animal studies using yellow mealworm (Tenebrio molitor) and buffalo (Alphitobius diaperinus) flours were then used to evaluate their safety in healthy rats and LPS-induced intestinal dysfunction rats. Chronic administration of these insect-derived flours showed no adverse effects on behavior, metabolism, intestinal morphology or immune response (such as inflammation or allergy markers) in healthy Wistar rats. Notably, in rats subjected to proinflammatory LPS-induced intestinal dysfunction, T. molitor consumption did not exacerbate symptoms, nor did it increase allergic responses. These findings validate the safety of these edible insects under healthy conditions, demonstrate their innocuity in a model of intestinal dysfunction, and underscore their promise as sustainable and nutritionally valuable dietary protein sources.

The A1/A2 β-casein genotype of cows, but not their horn status, influences peptide generation during simulated digestion of milk

The effect of the horn status of cows on their milk composition and quality is a controversial research topic. In this study, 128 milk samples from 64 horned and 64 disbudded Brown Swiss and Original Braunvieh cows were collected from alpine farms where both horned and disbudded cows were grazing on mountain pastures. The samples were analyzed for their detailed composition and protein digestion in a simulated in vitro digestion (INFOGEST). To exclude probable influences on digestion, the β-casein genotype with its variants A1 and A2 was also included in the study. The effects of horn status and β-casein genotype were investigated in linear mixed models, which included additional influencing random factors such as Original Braunvieh blood proportion, stage of lactation, and farm. Horn status did not have any effect on milk composition or digestion. In contrast, milk from A1A1 cows showed a different protein digestion than milk of A1A2 and A2A2 cows in the gastric phase, including smaller amounts of β-casomorphin(BCM)21-associated peptides and larger amounts of BCM11-associated peptides. Abundances of BCM7 did not differ between β-casein genotypes. At the end of the intestinal phase, the digested milk of A1A1 and A2A2 b-casein genotypes did not differ.

The role of food structure in gastric-emptying rate, absorption and metabolism

The high levels of non-communicable diseases such as CVD and type 2 diabetes mellitus are linked to obesity and poor diet. This continuing emphasis on health in relation to food is proving a powerful driver for the development of cheap but palatable and more functional foods. However, the efficacy of such foods is often hard to prove in human subjects. Thus, a suite of tools has been developed including in silico and in vitro simulations and animal models. Although animal models offer physiologically relevant platforms for research, their use for experimentation is problematic for consumers. Thus, in vitro methods such as Infogest protocols have been developed to provide digestion endpoints or even an indication of the kinetics of digestion. These protocols have been validated for a range of food systems but they still miss the final absorption step. This review discusses the use of such in vitro models and what further steps need to be included to make the bioaccessibility determination more relevant to bioavailability and human health.

Influence of Dietary Fibre and Protein Fractions on the Trace Element Bioaccessibility of Turnip Tops (Brassica rapa) Growing under Mediterranean Conditions

The objective of this work was to study the influence of three dietary fibre fractions (pectin, gum arabic and cellulose) and three protein fractions (casein, lactalbumin and soy) on the trace element bioaccessibility (Fe, Mn, Ni, Se and Zn) of turnip tops (B. rapa subsp. Rapa) growing under Mediterranean conditions. Then, it aimed to promote the use of this vegetable not only for direct fresh consumption but also as a main ingredient in the development of food mixtures. The results showed that soluble fibre fractions, such as pectin and gum arabic, can enhance the bioaccessibility of trace elements, such as Fe, Mn, Se and Zn. This effect was not proved for cellulose (an insoluble fibre fraction), in which, at best, no bioaccessibility effect was observed. Regarding the protein fractions, with the exception of Se, caseins and lactalbumin had a neutral effect on improving the trace element bioaccessibility. This did not hold true for soy protein, in which a considerable improvement in the bioaccessibility of Fe, Mn, Se and Zn was determined.

Beyond the Bowl: Understanding Amino Acid Requirements and Digestibility to Improve Protein Quality Metrics for Dog and Cat Foods

The determination of amino acid (AA) requirements for mammals has traditionally been done through nitrogen (N) balance studies, but this technique underestimates AA requirements in adult animals. There has been a shift toward researchers using the indicator amino acid oxidation (IAAO) technique for the determination of AA requirements in humans, and recently in dogs. However, the determination of AA requirements specific to adult dogs and cats at maintenance is lacking and the current requirements outlined by the National Research Council are based on a dearth of data and are likely underreporting the requirements of indispensable AA (IAA) for the population. To ensure the physiological requirements of our cats and dogs are met, we need methods to accurately and precisely measure digestibility. In vivo methods, such as ileal cannulation, are most commonly used, however, due to ethical considerations, we are moving away from animal models and toward in vitro methods. Harmonized static digestion models have the potential to replace in vivo methods but work needs to be done to have these methods more accurately represent the gastrointestinal tract (GIT) of cats and dogs. The Digestible IAA Score (DIAAS) is one metric that can help define protein quality for individual ingredients or mixed diets that uses AA SID estimates and ideally those can be replaced with in vitro AA digestibility estimates. Finally, we need accurate and reliable laboratory AA analyses to measure the AA present in complete diets, especially those used to quantify methionine (Met) and cysteine (Cys), both often limiting AAs in cat and dog diets. Together, this will guide accurate feed formulation for our companion animals to satisfy requirements while avoiding over-supplying protein, which inevitably contributes to excess N excretion, affecting both the environment and feed sustainability.

Wild and Micropropagated Artemisia eriantha Infusions: In Vitro Digestion Effects on Phenolic Pattern and Antioxidant Activity

This study investigated the in vitro simulated gastrointestinal digestion (GID) effects on wild and micropropagated Apennines Genepì infusions. Wild and micropropagated infusions were compared for their antioxidant activity, phenolic contents, and polyphenolic profiles before and after GID. Before digestion, the wild infusions had higher amounts of phenolic compounds and antioxidant activity than the micropropagated ones. Instead, after digestion, the differences in the total phenolic content (TPC) and antioxidant activity between wild and micropropagated infusions were less pronounced. The changes in the TPC and phenolic profiles revealed the presence of several chemical transformations and rearrangements that resulted in compounds with different reactivity and antioxidant potential. Without enzyme actions, the wild infusion digest undergoes higher modifications than those obtained from the micropropagated ones. The current study offers the first concrete proof of the impact of GID on the polyphenolic chemicals present in infusions of wild and micropropagated Apennines Genepì and their antioxidant properties. Our findings are essential for future in-depth analyses of Apennine Genepì infusions and their potential impacts on human health.

Bioaccessibility data of potentially toxic elements in complementary foods for infants: A review

The introduction of complementary foods (CFs) is a critical step in an infant's transition to solid foods, providing essential nutrients beyond breast milk. However, CFs may contain potentially toxic elements (PTEs), such as arsenic and cadmium that pose health risks to infants. In this context, understanding the bioaccessibility of PTEs is vital as it determines the fraction of a contaminant released from the food matrix and available for absorption in the gastrointestinal tract. Efforts have been made to standardize the assessment methodology for bioaccessibility, ensuring consistent and reliable data. Moreover, regulatory agencies have established guidelines for PTEs levels in food. However, important gaps still exist, which motivates many research opportunities on this topic.

Formation and In Vitro Simulated Digestion Study of Gelatinized Korean Pine Seed Oil Encapsulated with Calcified Wax

Natural waxes have demonstrated exceptional potential as oil gels for saturated and trans fatty acids, but their application has been limited by issues such as temperature sensitivity, lack of stability and durability, and compatibility. In this study, three types of wax (Beeswax (BW), Rice bran wax (RBW), and Carnauba wax (CW)) were combined with calcium hydroxide to produce calcified wax. The calcified Korean pine seed oil gel obtained by heating and stirring with Korean pine seed oil is responsive to temperature and has environmental adaptability. The effects of critical gel concentration, temperature regulation, texture properties, microstructure, oil-holding capacity, and FT-IR on the quality parameters of oil gel were investigated. Additionally, an in vitro digestion model was developed to comprehend the decomposition rate of fat during gel structure digestion and transportation. The results demonstrated a close correlation between the critical gelation concentration and calcium ion content. Furthermore, after calcification, the hardness followed the order BW > CW > RBW. Moreover, there was an approximate 10 °C increase in wax melting point. Conversely, BW:Ca exhibited the lowest oil leakage. The microstructures revealed that the oil gels formed post-wax calcification exhibited similar fractal dimension (Db) values (<7 μm), and the intermolecular forces were characterized by van der Waals forces, which were consistent with those observed in the non-calcified group. In conjunction with the vitro digestion simulation, our findings demonstrated that RBW and CW oil gels gradually released 20%, 35%, and 35% of free fatty acids (FFA) within the initial 30 min of intestinal digestion. Importantly, the FFA release rate was significantly attenuated, thereby providing a foundation for developing wax-based gel processed foods that facilitate gentle energy release benefits for healthy weight management.

Application of small angle scattering (SAS) in structural characterisation of casein and casein-based products during digestion

In recent years, small and ultra-small angle scattering techniques, collectively known as small angle scattering (SAS) have been used to study various food structures during the digestion process. These techniques play an important role in structural characterisation due to the non-destructive nature (especially when using neutrons), various in situ capabilities and a large length scale (of 1 nm to ∼20 μm) they cover. The application of these techniques in the structural characterisation of dairy products has expanded significantly in recent years. Casein, a major dairy protein, forms the basis of a wide range of gel structures at different length scales. These gel structures have been extensively researched utilising scattering techniques to obtain structural information at the nano and micron scale that complements electron and confocal microscopy. Especially, neutrons have provided opportunity to study these gels in their natural environment by using various in situ options. One such example is understanding changes in casein gel structures during digestion in the gastrointestinal tract, which is essential for designing personalised food structures for a wide range of food-related diseases and improve health outcomes. In this review, we present an overview of casein gels investigated using small angle and ultra-small angle scattering techniques. We also reviewed their digestion using newly built setups recently employed in various research. To gain a greater understanding of micro and nano-scale structural changes during digestion, such as the effect of digestive juices and mechanical breakdown on structure, new setups for semi-solid food materials are needed to be optimised.

Insights into the in vitro digestibility of pork myofibrillar protein with different ionic polysaccharides from the perspective of gel characteristics

In this work, the simulated gastrointestinal digestion of myofibrillar protein gels (MPGs) with anionic xanthan (XMP) and sodium alginate (SMP)/cationic chitosan (CSMP)/neutral curdlan (CMP) and konjac (KMP) was investigated to develop muscle-gelled foods with good qualities before and after eating. The results indicated that the neutral CMP and KMP groups had higher gel strength and protein digestibility than the CSMP group. Xanthan and sodium alginate facilitated myosin degradation in gastrointestinal digestion because of the weak wraps between protein and anionic polysaccharides, gaining plentiful peptides (1790 and 1692 respectively) with molecular weights below 2000 Da. Chitosan and neutral curdlan could improve the strength of MP gel but inhibited proteolysis and resulted in low contents of released amino acids via the strong cross-linked network blocking trypsin contact. This work provides a theoretical basis for developing low-fat meat products with good qualities and digestion behaviors by simply controlling the ionic types of polysaccharides.

Mineral Bioaccessibility and Antioxidant Capacity of Protein Hydrolysates from Salmon (Salmo salar) and Mackerel (Scomber scombrus) Backbones and Heads

Information on the bioaccessibility of minerals is essential to consider a food ingredient as a potential mineral fortifier. In this study, the mineral bioaccessibility of protein hydrolysates from salmon (Salmo salar) and mackerel (Scomber scombrus) backbones and heads was evaluated. For this purpose, the hydrolysates were submitted to simulated gastrointestinal digestion (INFOGEST method), and the mineral content was analyzed before and after the digestive process. Ca, Mg, P, Fe, Zn, and Se were then determined using an inductively coupled plasma spectrometer mass detector (ICP-MS). The highest bioaccessibility of minerals was found in salmon and mackerel head hydrolysates for Fe (≥100%), followed by Se in salmon backbone hydrolysates (95%). The antioxidant capacity of all protein hydrolysate samples, which was measured by Trolox Equivalent Antioxidant Capacity (TEAC), increased (10-46%) after in vitro digestion. The heavy metals As, Hg, Cd, and Pb were determined (ICP-MS) in the raw hydrolysates to confirm the harmlessness of these products. Except for Cd in mackerel hydrolysates, all toxic elements were below the legislation levels for fish commodities. These results suggest the possibility of using protein hydrolysates from salmon and mackerel backbones and heads for food mineral fortification, as well as the need to verify their safety.

In vitro digestion models for the design of safe and nutritious foods

Responsible development of future foods requires in depth understanding of food digestion in the human body based on robust research models, ranging from in vitro models to randomized controlled human trials. This chapter overviews fundamental aspects of food digestion, namely bioaccessibility and bioavailability, and models mirroring gastric, intestinal, and colonic conditions. Second, the chapter demonstrates the potential of in vitro digestion models to help screen adverse effects of food additives, such as Titanium dioxide or carrageenan, or underpin the determinants of macro- and micronutrient digestion in different strata of the population, for example digestion of emulsions. Such efforts support rationalized design of functional foods, such as infant formulae, cheese, cereals and biscuits which are validated in vivo or in randomized controlled trials.

Bioaccessibility of glucosinolates, isothiocyanates and inorganic micronutrients in cruciferous vegetables through INFOGEST static in vitro digestion model

Green tissues and seeds from cruciferous vegetables growing in conventional and ecological conditions (Brassica carinata; Brassica rapa; Eruca vesicaria and Sinapis alba) were analyzed to determine their contents of glucosinolates, isotihiocyanates (ITCs) and inorganic micronutrients (Ca, Cr, Cu, Fe, Mn, Ni, Se and Zn), and the bioaccessibility of these compounds. Regarding total contents and bioaccessibility values of these compounds, no clear difference was found between the organic and conventional systems. Glucosinolates bioaccessibility present in green tissues were high, with values around 60-78%. In additon, it was quantified in bioaccessible fraction ITCs concentrations such as Allyl - ITC; 3 - Buten - 1 - yl - ITC and 4 - Penten - 1 - yl - ITC. Trace elements bioaccessibility in green tissues was also high for Ca (2.26-7.66 mg/g), Cu (0.60-2.78 µg/g), Se (9.93-74.71 µg/Kg) and Zn (12.98-20.15 µg/g). By contrast, the bioaccessibility of glucosinolates and trace elements in cruciferous seeds was extremely low. With the exception of Cu, these bioaccessibility percentages did not exceed 1% in most cases.

Efficient in vitro digestion of lipids and proteins in bovine milk fat globule membrane ingredient (MFGMi) and whey-casein infant formula with added MFGMi

The relative immaturity of the infant digestive system has the potential to affect the bioavailability of dietary lipids, proteins, and their digested products. We performed a lipidomic analysis of a commercial bovine milk fat globule membrane ingredient (MFGMi) and determined the profile of lipids and proteins in the bioaccessible fraction after in vitro digestion of both the ingredient and whey-casein-based infant formula without and with MFGMi. Test materials were digested using a static 2-phase in vitro model, with conditions simulating those in the infant gut. The extent of digestion and the bioaccessibility of various classes of neutral and polar lipids were monitored by measuring a wide targeted lipid profile using direct infusion-mass spectrometry. Digestion of abundant proteins in the ingredient and whey-casein infant formula containing the ingredient was determined by denaturing PAGE with imaging of Coomassie Brilliant Blue stained bands. Cholesterol esters, diacylglycerides, triacylglycerides, phosphatidylcholines, and phosphatidylethanolamines in MFGMi were hydrolyzed readily during in vitro digestion, which resulted in marked increases in the amounts of free fatty acids and lyso-phospholipids in the bioaccessible fraction. In contrast, sphingomyelins, ceramides, and gangliosides were largely resistant to simulated digestion. Proteins in MFGMi and the infant formulas also were hydrolyzed efficiently. The results suggest that neutral lipids, cholesterol esters, phospholipids, and proteins in MFGMi are digested efficiently during conditions that simulate the prandial lumen of the stomach and small intestine of infants. Also, supplementation of whey-casein-based infant formula with MFGMi did not appear to alter the profiles of lipids and proteins in the bioaccessible fraction after digestion.

Administration of Alphitobius diaperinus or Tenebrio molitor before meals transiently increases food intake through enterohormone regulation in female rats

BACKGROUND

It has been previously shown that acutely administered insect Alphitobius diaperinus protein increases food intake in rats and modifies the ex vivo enterohormone secretory profile differently than beef or almond proteins. In this study, we aimed to evaluate whether these effects could be maintained for a longer period and determine the underlying mechanisms.

RESULTS

We administered two different insect species to rats for 26 days and measured food intake at different time points. Both insect species increased food intake in the first week, but the effect was later lost. Glucagon-like peptide 1 (GLP-1) and ghrelin were measured in plasma and ex vivo, and no chronic effects on their secretion or desensitization were found. Nevertheless, digested A. diaperinus acutely modified GLP-1 and ghrelin secretion ex vivo.

CONCLUSION

Our results suggest that increases in food intake could be explained by a local ghrelin reduction acting in the small intestine. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Structure and IgE Cross-Reactivity among Cashew, Pistachio, Walnut, and Peanut Vicilin-Buried Peptides

Peanut and tree-nut allergies are frequently comorbid for reasons not completely understood. Vicilin-buried peptides (VBPs) are an emerging family of food allergens whose conserved structural fold could mediate peanut/tree-nut co-allergy. Peptide microarrays were used to identify immunoglobulin E (IgE) epitopes from the N-terminus of the vicilin allergens Ara h 1, Ana o 1, Jug r 2, and Pis v 3 using serum from three patient diagnosis groups: monoallergic to either peanuts or cashew/pistachio, or dual allergic. IgE binding peptides were highly prevalent in the VBP domains AH1.1, AO1.1, JR2.1, and PV3.1, but not in AO1.2, JR2.2, JR2.3, and PV3.2 nor the unstructured regions. The IgE profiles did not correlate with diagnosis group. The structure of the VBPs from cashew and pistachio was solved using solution-NMR. Comparisons of structural features suggest that the VBP scaffold from peanuts and tree-nuts can support cross-reactivity. This may help understand comorbidity and cross-reactivity despite a distant evolutionary origin.

Acrylamide bioaccessibility in potato and veggie chips. Impact of in vitro colonic fermentation on the non-bioaccessible fraction

Potato-based products contribute largely to the daily intake of acrylamide. In addition to potato crisps, the European Commission has included veggie crisps in the list of foods that should be monitored for their acrylamide content. In the present study, acrylamide content in potato and veggie chips (sweet potato, beetroot and carrot) and their bioaccessibility after in vitro digestion was assessed. The non-bioaccessible fraction was also submitted to in vitro fermentation under colonic conditions. Faecal samples from volunteers of three age groups (children, adolescents and adults) were used to evaluate the microbiota effect on the acrylamide availability. Sweet potato chips exhibited the highest acrylamide content (2342 µg/kg), followed by carrot (1279 µg/kg), beetroot (947 µg/kg) and potato chips (524 µg/kg). After in vitro digestion, acrylamide bioaccessibility was significantly lower in veggie chips (59.7-60.4 %) than in potato chips (71.7 %). Potato and sweet potato chips showed the significantly lowest acrylamide content in the non-bioaccessible fraction (22.8 and 24.1 %, respectively) as compared with beetroot chips (28.4 %). After the fermentation step, acrylamide percentage in the soluble fraction of veggie chips ranged from 43.03 to 71.89 %, the highest values being observed in sweet potato chips fermented with microbiota from children. This fact would involve that the acrylamide was released from the non-bioaccessible fractions by the microbiota. These findings point out that the levels of potentially absorbable acrylamide after the complete gastrointestinal process could be modulated by both the food matrix composition and the microbiota. These factors should be further considered for a more precise risk assessment of dietary acrylamide in humans.

Calcium bioaccessibility increased during gastrointestinal digestion of α-lactalbumin and β-lactoglobulin

Calcium bioaccessibility depends on the amount of soluble calcium under intestinal digestion. The changes in calcium during in vitro static digestion of α-lactalbumin and β-lactoglobulin in presence of calcium chloride (0 mM, 20 mM and 50 mM) were followed by combining electrochemical determination of free calcium with the determination of soluble calcium by inductively coupled plasma optical emission spectroscopy. α-Lactalbumin and, more evident, β-lactoglobulin were found to increase calcium bioaccessibility with increasing intestinal digestion time by around 5% and 10%, respectively, due to the complex binding of calcium to peptides formed from protein hydrolysis by gastrointestinal enzymes. In vitro digested samples of β-lactoglobulin in presence of CaCl₂ had nearly twice as much complex bound calcium as α-lactalbumin samples. The calcium bioaccessibility decreased significantly with the increasing concentration of added calcium chloride, although the amount of calcium chloride had little effect on the extension of digestion of α-lactalbumin and β-lactoglobulin. Simulated digestion fluids were found to have a negative effect on calcium bioaccessibility, especially the presence of hydrogen phosphate, and the amount of precipitated calcium increased significantly with increasing amount of added calcium chloride. Based on analysis and visualization by sequences of the peptides formed during digestion of α-lactalbumin and β-lactoglobulin, it was observed that peptides containing aspartic acid and glutamic acid acting as calcium chelators, may prevent precipitation of calcium in the intestines and increase calcium bioaccessibility. These results provide knowledge for the design of new dairy based functional foods to prevent calcium deficiency.

Analytical and functional approaches to assess the immunogenicity of gluten proteins

Gluten proteins are the causative agents of celiac disease (CD), a lifelong and worldwide spread food intolerance, characterized by an autoimmune enteropathy. Gluten is a complex mixture of high homologous water-insoluble proteins, characterized by a high content of glutamine and proline amino acids that confers a marked resistance to degradation by gastrointestinal proteases. As a consequence of that, large peptides are released in the gut lumen with the potential to activate inflammatory T cells, in CD predisposed individuals. To date, several strategies aimed to detoxify gluten proteins or to develop immunomodulatory drugs to recover immune tolerance to gluten are under investigation. This review overviews the state of art of both analytical and functional methods currently used to assess the immunogenicity potential of gluten proteins from different cereal sources, including native raw seed flours and complex food products, as well as drug-treated samples. The analytical design to assess the content and profile of gluten immunogenic peptides, described herein, is based on the oral-gastro-intestinal digestion (INFOGEST model) followed by extensive characterization of residual gluten peptides by proteomic and immunochemical analyses. These approaches include liquid chromatography-high-resolution mass spectrometry (LC-MS/MS) and R5/G12 competitive ELISA. Functional studies to assess the immune stimulatory capabilities of digested gluten peptides are based on gut mucosa T cells or peripheral blood cells obtained from CD volunteers after a short oral gluten challenge.

Nutritional composition and minerals bioaccessibility of commercial fruit flours

Commercial fruit flours were evaluated concerning: (i) the nutritional composition (proximate composition, total phenolic content, and minerals content), (ii) their contribution to estimated mineral daily intake, (iii) the bioaccessibility of essential minerals using the in vitro INFOGEST digestion method and (iv) the influence of their chemical composition on minerals bioaccessibility. The 20 samples analysed presented high variability concerning the content of dietary fibre (7.5 to 69.7 g/100 g), carbohydrates (4.1 to 74.9 g/100 g), protein (2.9 to 12.9 g/100 g), ash (1.0 to 7.0 g/100 g), lipids (1.0 to 8.1 g/100 g) and total phenolic content (2.9 to 41.0 mg GAE/g. The mineral content of fruit flours provides a great contribution to the daily mineral requirements (especially Mg, Fe, Mn and Cu) with a daily intake of 30 g and very low contribution to the daily requirements of Na (0–3%). Low bioaccessibility was observed for Ca (18.0%) and Fe (28.9%), while Mg was the most bioaccessible mineral (81.5%). Though, the bioaccessible fraction of Mg showed negative correlation with total dietary fibre content (r = − 0.77) and lipids (r = − 0.46).

Effect of the simulated digestion process on the chlorogenic acid trapping activity against methylglyoxal

Chlorogenic acids are hydroxycinnamic derivatives widespread in food or food by-products, known for their antioxidant effects and ability to interfere with the formation of advanced glycation end products (AGEs). AGEs are potential glycotoxins involved in age-related disorders, such as diabetes, cardiovascular diseases, and neurological disorders. The ability of chlorogenic acids to inhibit AGE formation under physiological conditions needs further investigation other than the in vitro assays. Therefore, in this study, the capacity of 5-caffeoylquinic acid (5-CQA) to effectively trap methylglyoxal (MGO), an AGE precursor compound also present in daily consumed food, was investigated by evaluating 5-CQA and MGO metabolic fate when subjected to digestion. Two different in vitro digestion approaches (static based on the Infogest protocol and dynamic based on a novel millifluidic gastrointestinal model) were set up and the samples collected at different steps of the static and dynamic processes were analyzed by a validated RP-HPLC-DAD method. The obtained results indicated that the gastrointestinal process strongly affected the 5-CQA capacity to trap MGO and its resulting antiglycation activity. Therefore, preliminary investigation using advanced in vitro tests, particularly dynamic approaches, should always be performed to predict the effect of the digestion process on the potential bioactives present in food, food by-products, or plant extracts.

Simulated gastric fluid assay for estimating the digestibility of newly expressed proteins in GE crops: Missteps in development and interpretation

Digestive stability of a food protein in simulated gastric fluid (SGF) continues to be considered a risk factor for allergy, even though the current science does not support this belief. Methodological shortcomings of the adaption of the SGF assay for use with purified proteins has been cited as a reason to discount results that do not conform to this belief. Missteps in conducting and interpreting the results of SGF assays are reviewed here. However, these methodological shortcomings do not invalidate the conclusion that allergenic proteins are not systematically more stable to digestion than non-allergens. The growing evidence for the dual allergen exposure hypothesis, whereby sensitization to food allergens is primarily caused by dermal and inhalation exposure to food dust, and tolerization against food allergy is primarily induced by gut exposure in food, likely explains why the digestive stability of a protein is not a risk factor for allergenicity.

Health Beneficial Bioactivities of Faba Bean Gastrointestinal (In Vitro) Digestate in Comparison to Soybean and Pea

Faba beans are a promising emerging plant-based protein source to be used as a quality alternative to peas and soy. In this study, the potential health beneficial activities of three Canadian faba bean varieties (Fabelle, Malik and Snowbird) were investigated after in vitro gastrointestinal digestion and compared to two commonly used legumes (peas and soy). The results revealed that the faba beans had a higher antioxidant activity than peas when assessed with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays, except for the Fabelle variety. In the oxygen radical absorbance capacity (ORAC) and the iron chelating assays, the faba beans had a lower antioxidant activity than soy. Interestingly, Fabelle and Snowbird showed a higher antioxidant effect than the peas and soy at the cellular level. The antihypertensive properties of Fabelle and Malik varieties were significantly higher than peas but lower than soy. The in vitro antidiabetic activity was higher for soy, but no differences were found at the cellular level. The faba bean peptides were further fractionated and sequenced by mass spectrometry. Eleven peptides with in silico predicted bioactivities were successfully identified in the faba bean digestate and support validating the health-promoting properties of peptides. The results demonstrate the bioactive potential of faba beans as a health-promoting food ingredient against non-communicable diseases.

Effects of Marine Bioactive Compounds on Gut Ecology Based on In Vitro Digestion and Colonic Fermentation Models

Digestion and the absorption of food compounds are necessary steps before nutrients can exert a role in human health. The absorption and utilization of nutrients in the diet is an extremely complex dynamic process. Accurately grasping the digestion and absorption mechanisms of different nutrients or bioactive compounds can provide a better understanding regarding the relationship between health and nutrition. Several in vitro models for simulating human gastrointestinal digestion and colonic fermentation have been established to obtain more accurate data for further understanding of the metabolism of dietary components. Marine media is rich in a wide variety of nutrients that are essential for humans and is gaining increased attention as a research topic. This review summarizes some of the most explored in vitro digestion and colonic fermentation models. It also summarizes the research progress on the digestion and absorption of nutrients and bioactive compounds from marine substrates when subjected to these in vitro models. Additionally, an overview of the changes imparted by the digestion process on these bioactive compounds is provided, in order to support those marine resources that can be utilized for developing new healthy foods.

Sterol bioaccessibility in a plant sterol-enriched beverage using the INFOGEST digestion method: Influence of gastric lipase, bile salts and cholesterol esterase

This study evaluates the influence of increasing bile salts and the addition of key enzymes of the lipidic metabolism in the INFOGEST digestion method on sterol bioaccessibility from a plant sterol (PS)-enriched beverage. The assayed modifications were increasing concentration of bovine bile salts (10 vs. 17.5 mM), and addition of gastric lipase (GL) (60U/mL), cholesterol esterase (CE) (0.075 or 2U/mL) or both. Compared to the original method (10 mM bile salts without enzymes), the assayed conditions significantly reduced bioaccessibility of individual (from 11.3 to 19.7 to 5.1-16.6%) and total PS (13.7 to 6.9-8.0%), and cholesterol (52.8 to 20.9-26.1%), except only when CE is added not allowing cholesterol quantification. The bioaccessibility achieved when lipolytic enzymes were tested was similar for all sterols. For a more physiological approach to in vivo conditions, incorporation of bile salts (10 mM), GL (60U/mL) and CE (0.075U/mL) to the INFOGEST method is proposed, although it increases the cost compared to the established method.

New Alternatives to Milk From Pulses: Chickpea and Lupin Beverages With Improved Digestibility and Potential Bioactivities for Human Health

There is a strong demand for plant-based milk substitutes, often low in protein content (&lt;1.5% w/v). Protein-rich pulse seeds and the right processing technologies make it possible to make relevant choices. The major objective of this study was to assess the impact of processing on the nutritional characteristics of beverages with a high impact on health, in particular on digestibility and specific bioactivities. The results suggest that pulse beverages are as high in protein content (3.24% w/v for chickpea and 4.05% w/v for lupin) as cow’s milk. The anti-nutrient level characteristics of pulses have been considerably reduced by strategic processing. However, when present in small quantities, some of these anti-nutritional factors may have health benefits. Controlling processing conditions play a crucial role in this fine balance as a tool to take advantage of their health benefits. There is evidence of protein hydrolysis by in vitro digestion and limited bioaccessibility of minerals. In addition to being highly digestible, lupin and chickpea beverages have anti-inflammatory and anti-carcinogenic potential evaluated through the inhibition of metalloproteinase MMP-9.

In Vitro Protein Digestion of Cooked Spent Commercial Laying Hen and Commercial Broilers Breast Meat

Chicken meat from spent laying hens (SHs) has been considered as nutritive as the meat of commercial broilers (CBs) based on chemical composition. High insoluble collagen in SH meat might reduce protein digestibility and bio-accessibility compared to CB meat. This study aimed at comparing the in vitro protein digestibility of CB and SH cooked breast meat. In the first part, CB samples were digested using two static in vitro digestion methods and collected at different digestion points for determining the degree of hydrolysis (DH). The method providing a greater DH value was chosen for comparing protein digestibility between CB and SH samples. The activities of used enzymes during in vitro digestion were evaluated based on bicinchoninic acid assay 2,4,6-trinitrobenzenesulfonic acid colorimetric method, gas chromatography-mass spectrometry, and sodium dodecyl sulfate-polyacrylamide electrophoresis. Particle size distribution of solid content collected from hydrolysate was also determined. The results showed that after digestion, CB showed 1−3 mg/mL protein concentration lower, while 7−13% DH and 50−96 µmoL/g protein-free NH2 groups higher when compared to those of SH. Based on sodium dodecyl sulfate-polyacrylamide electrophoresis, CB samples exhibited greater intensity of band at MW < 15 kDa than that of SH. Regarding particle size in terms of volume weighted mean (D[4,3]), at the end of the oral phase, the end of the gastric phase, and the beginning of the intestinal phase, D[4,3] of the SH samples were 133.17 ± 2.16, 46.52 ± 2.20, and 112.96 ± 3.63 µm, respectively, which were greater than those of CB (53.28 ± 1.23, 35.59 ± 1.19, and 51.68 ± 1.25 µm). However, at the end of the intestinal phase, D[4,3] of SH and CB, which were 17.19 ± 1.69 and 17.52 ± 2.46 µm, respectively, did not significantly differ from each other. The findings suggested a greater in vitro protein digestibility of cooked CB breast meats than that of SH ones.

Studying semi-dynamic digestion kinetics of food: Establishing a computer-controlled multireactor approach

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.