Comparison of protein in vitro digestibility under adult and elderly conditions: The case study of wheat, pea, rice, and whey proteins

Unveiling the slow digestion and peptide profiles of polymerised whey gel via heat and TGase crosslinking: An in vitro/vivo perspective

Polymerised whey is widely used in dairy products and can affect digestibility when its high-molecular-weight aggregates and gel structure are modified. This study investigated the digestibility, peptide profiles and satiety of modified whey protein isolate (MWPI) pre-heated with transglutaminase. Results showed that 43.06 % of MWPI was digested during the 4-h in vitro digestion, indicating a slow digestion rate. Compared with whey protein isolate (WPI), MWPI yielded 103 peptides with higher abundance following in vitro digestion, including 17 angiotensin-converting enzyme inhibitors and 1 dipeptidyl peptidase-4 inhibitor. Visual analytics indicated differential peptides located at distinct α-helix and β-sheet of β-lactoglobulin, α-lactalbumin and bovine serum albumin. MWPI gavage extended stomach retention time, decreased intestinal propulsion rate from 75.60 % (WPI group) to 33.72 % in 30 min and enhanced satiety within 120 min compared with WPI. Overall, whey polymerisation modulates protein-enzyme interactions, releasing different peptides and enhancing satiety.

Improved skeletal muscle mass and strength through Protamex-mediated hydrolysis of perilla seed cake: Elevated rosmarinic acid levels as a contributing factor

Perilla seed cake (PSC) is a byproduct of oil extraction from perilla seeds. It is rich in proteins and bioactive compounds. PSC was enzymatically hydrolyzed to form PSC hydrolysate (PSCH) to enhance the absorption of PSC, and their effects on muscle health in mice were compared. High performance liquid chromatography-tandem mass spectrometry analysis revealed that PSC contains several polyphenols, including rosmarinic acid (RA), caffeic acid, apigenin, and luteolin. The hydrolysate showed 1.44- and 7.04-fold increases in RA and caffeic acid contents, respectively, compared to those of PSC. The intake of PSC, PSCH, and RA significantly improved muscle mass and exercise performance in mice by upregulating protein synthesis, myogenic differentiation, oxidative muscle fiber formation, fatty acid oxidation, and mitochondrial biogenesis; however, PSCH had better promoting effects than PSC. In conclusion, PSCH improves muscle health through its bioactive compounds (particularly RA), indicating the potential of PSCH and RA in functional foods.

Comparison of in vitro digestive characteristics of proteins from different sources in simulated elderly gastrointestinal conditions

This study aimed to evaluate the impact of in vitro digestive characteristics of five different protein sources (fish, crab, beef, chicken, and soy) in adults and elderly individuals. Simulated gastrointestinal tract degradation in the elderly significantly reduced the digestibility of all proteins. The Elderly model had difficulties digesting any protein that had a firm structure or was prone to aggregation. Of the five protein types, soy protein was the least easily digested. Ultraviolet spectroscopy and SDS-PAGE analysis revealed that beef and crab proteins contain myoglobin and hemocyanin, respectively, making their structure firm. Simultaneously, alkali-soluble proteins in meat were more likely to be digested by the elderly than salt-soluble proteins. The alkali-soluble protein percentage in fish protein was the highest, including the best in vitro digestion characteristics in the elderly population. This study provides novel and significant recommendations for the elderly's daily intake of various protein sources.

Protein digestibility and techno-functional performance of milk-alternative prototypes based on combinations of lentil and cereal protein

Lentil protein isolate was combined with proteins from oat, rice, brewer's spent grain (BSGP) and wheat to achieve plant-based milk alternatives (PBMA) with improved protein quality and functionality. Due to the complementary amino acid (AA) profile of pulse protein which is high in lysine, and cereal protein which is high in sulphur amino acids, their combination at an optimised ratio resulted in a protein blend with a significantly improved indispensable amino acid score (IAAS) compared to the single ingredients. All protein combinations with lentil except for wheat resulted in a full IAAS for adults. The in vitro protein digestibility was assessed using the static INFOGEST digestion model to calculate the proxy in vitro DIAAS (PIVDIAAS) of the emulsions. Techno-functional properties such as particle size, rheological behaviour and physical stability were investigated. The PIVDIAAS of the combined protein emulsions was found to be 0.72, 0.78, 0.83, 0.98 for lentil + wheat, lentil + oat, lentil + BSGP and lentil + rice emulsions, respectively, compared to 0.48, 0.25, 0.5, 0.67 and 0.81 determined for the emulsions based on lentil, wheat, oat, BSGP and rice alone, respectively. The emulsions based on the combination of lentil and cereal protein also showed improved physical stability regarding sedimentation and creaming, and a higher whiteness index of the emulsions. It could be shown that the combination of lentil and cereal protein is a promising strategy to achieve PBMAs with improved protein quality and techno-functionality.

Enhancing lipid digestion and absorption rate: The role of whey protein isolate short fibrils in emulsions

Lipid serve as a crucial energy source during prolonged endurance exercise, and whey protein isolate (WPI) is commonly applied in food emulsions to modulate lipid digestibility. Herein, we prepared WPI short fibrils, <400 nm in length, to stabilize emulsion and increase lipid digestion and absorption rates. Specifically, a 2 % (w/v) WPI solution was adjusted to pH 2 and heated at 90 °C for 6 h to produce long fibrils, followed by 168 h of shear force treatment to obtain short fibrils. Compared to native WPI and long fibrils, short fibrils exhibited smaller molecular weight and higher surface hydrophobicity. Both short and long fibrils showed no cytotoxic effects on BRL and HEK-293 cells. Emulsions stabilized by short fibrils displayed excellent emulsifying capacity and stability, along with favorable dispersion during in vitro digestion. Importantly, the short fibrils emulsion improved in vitro digestion rate of lipids and promoted the rapid lipid absorption in vivo. These findings suggest that modifying protein fibrils around oil droplets can modulate lipid digestibility, with short fibrils offering potential to improve lipid absorption in functional foods tailored for personalized nutrition in extreme endurance exercise.

Effect of high pressure homogenization on in vitro digestibility and colon fermentability of pea protein-rich bread designed for elderly consumers

Enrichment of staple foods with proteins can be a solution to tackle protein-energy malnutrition in the elderly. For instance, bread can be enriched with pea proteins that are cheap, sustainable and easily digestible. Non-conventional technologies, such as high pressure homogenization (HPH), can improve the digestibility of plant proteins. To characterize the health functionality of pea-enriched bread, a functional bread tailored to elderly consumers was developed by substituting 5% wheat flour with untreated or HPH-treated pea protein concentrate. Protein digestibility and colon fermentability were assessed by mimicking elderly in vitro gastrointestinal and gut microbiota conditions and compared with adult conditions. Bread reformulation with pea proteins affected physical and chemical properties and produced an increase in hardness, which is one of the key features for the acceptability of bread by the elderly. The highest hardness value was observed for pea protein bread, followed by HPH-treated pea protein bread and wheat bread. In vitro protein digestibility and fermentability were affected by reformulation and by physiological digestive conditions, with lower digestibility under elderly conditions compared to adult ones. The obtained results may contribute to a better understanding of food digestibility under different gastrointestinal conditions and its dependence on physiological and formulation factors, and ultimately would help to design age-tailored foods.

Impact of age on the digestion of cream cheese formulated with opposite caseins to whey proteins ratios: An in vitro study

Ageing leads to changes in the functionality of the digestive tract but the effect of age on digestion and absorption of nutrients remains unclear. The objective of this study was to investigate in vitro the digestion of two high-protein dairy products similar to cream cheese (24 % w/w proteins, 20 % w/w lipids) with opposite casein to whey protein ratios, 80:20 (WP-20), and 20:80 (WP-80). The new static digestion model adapted to the general older adult population (≥65 y.) proposed by INFOGEST was used, as well as the standard version of the protocol. Kinetics of proteolysis and lipolysis were compared between both models for each product, in the gastric and intestinal phases of digestion. In both cream cheeses, the degree of protein hydrolysis (DH-P) was significantly lower for older adults than for young adults at the end of the gastric phase (-19 % for WP-20, and -44 % for WP-80), and at the end of the intestinal phase (-16 % for WP-20, and -20 % for WP-80). The degree of lipid hydrolysis (DH-L) was also significantly lower for older adults than for young adults at the end of the digestion for WP-20 (-30 %), but interestingly it was not the case for WP-80 (similar DH-L were measured). Free fatty acids were also released faster from WP-80 than from WP-20 in both digestion conditions: after 5 min of intestinal digestion DH-L was already ≈32 % for WP-80 against 14 % for WP-20. This was attributed to the opposite casein to whey protein ratios, leading to the formation of different gel structures resulting in different patterns of deconstruction in the gastrointestinal tract. This study highlights the fact that it is essential to carefully consider the composition, structure, and digestibility of foods to develop products adapted to the specific needs of the older adult population.

Microencapsulation of flaxseed oil in pea protein-gum arabic complex coacervates delays lipid digestion in liquid yoghurt

Flaxseed oil coacervates were produced by complex coacervation using soluble pea protein and gum arabic as shell materials, followed by either spray or electrostatic spray drying and their incorporation to yoghurt. Three yoghurt formulations were prepared: yoghurt with spray-dried microcapsules (Y-SD); with electrospray-dried microcapsules (Y-ES); with the encapsulation ingredients added in free form (Y). The standardised semi-dynamicin vitrodigestion method (INFOGEST) was employed to study the food digestion. The structure was analysed by confocal laser scanning microscopy and particle size distribution. Protein and lipid digestion were monitored by cumulated protein/free NH2 release and cumulated free fatty acids release, respectively. Stable microcapsules were observed during gastric digestion, but there was no significant difference in protein release/hydrolysis among samples until 55 min of gastric digestion. Formulation Y showed less protein release after 74 min (40.46 %) due to the free SPP being available and positively charged at pH 2-4, resulting in interactions with other constituents of the yoghurt, which delayed its release/hydrolysis. The total release of protein and free NH2 by the end of intestinal digestions ranged between 46.56-61.15 % and 0.83-1.57 µmol/g protein, respectively. A higher release of free fatty acids from formulation Y occurred at the end of intestinal digestion, implying that coacervates promoted the delayed release of encapsulated oil. In summary, incorporating protein-polysaccharides-based coacervates in yoghurt enabled the delay of the digestion of encapsulated lipids but accelerated the digestion of protein, suggesting a promising approach for various food applications.

Effects of molecular structure and charge state on the foaming and emulsifying properties of Spirulina protein isolates

Microalgae protein holds great potential for various applications in the food industry. However, the current knowledge regarding microalgae protein remains limited, with little information available on its functional properties. Furthermore, the relationship between its molecular structure and functional properties is not well defined, which limits its application in food processing. This study aims to addresses these gaps though an analysis of the emulsibility and foamability of various soluble protein isolates from two species of Spirulina (Arthospira platensis and Spirulina platensis), and the functional properties of Spirulina protein isolates in relation to its molecular structure and charge state. Results revealed that the degree of cross-linking and aggregation or folding and curling of protein tertiary structures was higher in the highly soluble Spirulina protein isolates (AP50% and SP50%) than in the low-solubility isolates (AP30% and SP30%). The foaming capacity (FC) of AP50% and SP50% was found to be lower than that of AP30% and SP30%. Spirulina protein isolates can stably adsorb at the air-water interface for at least 20 min and possessed good interfacial activity. A high pH value was found to promote cross-linking of protein particles at the oil-water interface, thereby reinforcing the internal network structure of emulsions and increasing viscosity. These findings provide preliminary insights for potential applications of Spirulina protein isolates in food production, especially towards quality improvement.

Acid-active proteases to optimize dietary protein digestibility: a step towards sustainable nutrition

Introduction

Historically, prioritizing abundant food production often resulted in overlooking nutrient quality and bioavailability, however, environmental concerns have now propelled sustainable nutrition and health efficacy to the forefront of global attention. In fact, increasing demand for protein is the major challenge facing the food system in the 21st century with an estimation that 70% more food is needed by 2050. This shift has spurred interest in plant-based proteins for their sustainability and health benefits, but most alternative sources of protein are poorly digestible. There are two approaches to solve digestibility: improve the digestibility of food proteins or improve the digestive capacity of consumers. Enhancing nutrient digestibility and bioavailability across diverse protein sources is crucial, with proteases presenting a promising avenue. Research, inspired by the proteases of human breast milk, has demonstrated that exogenous microbial proteases can activate within the human digestive tract and substantially increase the digestion of targeted proteins that are otherwise difficult to fully digest.

Methods

Here, we introduce the use of an acid-active family of bacterial proteases (S53) to improve the digestibility and nutritional quality of a variety of protein sources, evaluated using the INFOGEST 2.0 protocol.

Results

Results from in vitro digestibility indicate that the most effective protease in the S53 family substantially improves the digestibility of an array of animal and plant-derived proteins-soy, pea, chickpea, rice, casein, and whey. On average, this protease elevated protein digestibility by 115% during the gastric phase and by 15% in the intestinal phase, based on the degree of hydrolysis.

Discussion

The widespread adoption of these proteases has the potential to enhance nutritional value and contribute to food security and sustainability. This approach would complement ongoing efforts to improve proteins in the food supply, increase the quality of more sustainable protein sources and aid in the nourishment of patients with clinically compromised, fragile intestines and individuals like older adults and high-performance athletes who have elevated protein needs.

From static to semi-dynamic in vitro digestion conditions relevant for the older population: starch and protein digestion of cooked lentils

In the context of adequately feeding the rising older population, lentils have an important potential as sources of (plant-based) protein as well as slowly digestible bio-encapsulated starch and fibre. This study evaluated in vitro digestion of protein and starch in lentils under conditions representing the gastrointestinal tract of older adults. Both static and semi-dynamic simulations were applied to analyze the effect of specific gastrointestinal conditions (healthy versus older adult) on macronutrient digestion patterns. Gastric proteolysis was strongly dependent on applied gastric pH (gradient), leading to a lower extent of protein hydrolysis for simulations relevant for older adults. Fewer and smaller (lower degree of polymerization, DP) bioaccessible peptides were formed during gastric proteolysis under older adult compared to healthy adult conditions. These differences, developed during the in vitro gastric phase, were compensated during small intestinal digestion, yielding similar final proteolysis levels regardless of the applied simulation conditions. In contrast, in the presence of saliva, amylolysis was generally accelerated under older adult conditions. Moreover, the current work highlighted the importance of considering saliva (or salivary amylase) incorporation in simulations where the applied gastric pH (gradient) allows salivary amylase activity. Under both healthy and older adult conditions, in vitro starch hydrolysis bio-encapsulated in cotyledon cells of cooked lentils was attenuated, compared to a white bread reference.

Comparative study of the effects of ultrasound-assisted alkaline extraction on black soldier fly (Hermetia illucens) larvae protein: Nutritional, structural, and functional properties

In this study, we developed an ultrasound-assisted alkaline method for extracting black soldier fly larvae protein (BSFLP). The effects of ultrasound-assisted extraction on the nutritional value, structural characteristics, and techno-functional properties of BSFLP were compared with those using the conventional hot alkali method. The results showed that ultrasound-assisted extraction significantly increased the extraction ratio of BSFLP from 55.40% to 80.37%, but reduced the purity from 84.19% to 80.75%. The BSFLP extracted by ultrasound-assisted extraction met the amino acid requirements for humans proposed by the Food and Agriculture Organization in 2013, and ultrasound-assisted extraction did not alter the limiting amino acids of the BSFLP. The ultrasound-assisted extraction increased the in vitro protein digestibility from 82.97% to 99.79%. Moreover, ultrasound-assisted extraction obtained BSFLP with a more ordered secondary structure and more loosely porous surface morphology, without breaking the peptide bonds. By contrast, the conventional hot alkaline method hydrolyzed BSFLP into smaller fragments. The effect of ultrasound-assisted extraction on the structure of BSFLP improved the solubility and emulsion capacity of BSFLP, but reduced its foaming properties. In conclusion, the results of this study suggest that ultrasound-assisted alkaline extraction could be a suitable method for extracting BSFLP and improving its nutritional value, and structural and functional properties. The findings obtained in this study could promote the wider application of BSFLP in food industry.

Organic acids in bread-making affecting gluten structure and digestibility

Although wheat gluten has remarkable technological properties, it can induce adverse immune reactions in susceptible individuals, such as wheat allergy and celiac disease. Technological processing and some additives on bread formulation can modify gluten physicochemical structure, but the knowledge about the impacts on the digestibility and immunogenicity of gluten is limited. The present study aimed to study the effect of adding organic acids (acetic or ascorbic) on dough rheological properties and bread technological characteristics. In addition, breads were subjected to in vitro digestion and the digesta were analyzed by confocal microscopy, SDS-PAGE and ELISA immunoassay. Acetic acid resulted in a decrease in dough development time up to 44 % and a reduction in stability up to 20 %. Ascorbic acid, present in vinegar, on the other hand, increased elastic modulus (G') and resistance to extension of dough. After the in vitro digestion, SDS-PAGE indicated that protein degradation started in the gastric phase, with the generation of low molecular weight peptides. Accordingly, ELISA immunoassay suggested a great reduction in immunogenic gliadin content from oral to gastric phase. At the end of the intestinal phase, samples with ascorbic acid did not differ from the control, while vinegar addition indicated a reduction in gluten immunogenicity with a reduction of about 44 % in immunogenic gliadin content compared to the control. Results show a window of opportunity in the modulation of wheat bread formulation with reduced allergenicity, while maintaining the technofunctional properties.

Influence of food oral processing, bolus characteristics, and digestive conditions on the protein digestibility of turkey cold meat and fresh cheese

During mastication, foods are progressively transformed to achieve swallowable boluses and their characteristics are crucial for the subsequent digestion events. The main goal of this work was to evaluate the impact of food oral processing, bolus properties, and different digestive conditions on the protein digestibility of turkey cold meat and fresh cheese. In vivo normal and deficient masticated food boluses were prepared by a young volunteer. Besides, three digestion models were used to simulate the different physiological conditions frequently observed in adults and the elderly, presenting good or poor oral health: i) Normal Masticated-Normal Digested model; ii) Deficient Masticated-Normal Digested model; and iii) Deficient Masticated-Elderly Digested model. The oral processing behaviour (number of chews, chewing time, chewing rate, and saliva uptake), bolus particle size, textural and viscoelastic properties of boluses, and protein digestibility of samples were determined. Results showed that deficient masticated boluses exhibited lower amounts of saliva uptake and greater particle sizes, hardness, stiffness, and rigidity, notably in deficient masticated turkey cold meat boluses. Moreover, the worst digestive scenario (Deficient Masticated-Elderly Digested model) negatively impacted on the proteolysis extend of samples, especially for total soluble proteins and soluble peptides contents. The current study demonstrates that the oral processing behaviour and degree of food fragmentation impacted on the granulometric, texture, and viscoelastic properties of both food boluses, whereas the worst digestive scenario commonly observed in the elderly reduced the proteolysis extend of the products evaluated.

In vitro digestion of two protein-rich dairy products in the ageing gastrointestinal tract

It is still unclear if changes in protein digestibility and absorption kinetics in old age may affect the anabolic effect of high-protein foods. The objective of this study was to investigate the digestion of two high-protein (10% w/w) dairy products in vitro: a fermented dairy product formulated with a ratio of whey proteins to caseins of 80 to 20% (WBD) and a Skyr containing mainly caseins. The new static in vitro digestion model adapted to the general older adult population (≥65 years) proposed by the INFOGEST international consortium was implemented to investigate the digestion of these products and compared with the standard version of the protocol. Kinetics of proteolysis was compared between both models for each product, in the gastric and intestinal phases of digestion. Protein hydrolysis was studied by the OPA method, SDS-PAGE, and LC-MS/MS, and amino acids were quantified by HPLC. Protein hydrolysis by pepsin was slower with the older adult model than with the young adult model, and consequently, in spite of a longer gastric phase duration, the degree of proteolysis (DH) at the end of the gastric phase was lower. Two different scenarios were observed depending on the type of dairy product studied: -10 and -40% DH for Skyr and WBD, respectively. In the intestinal phase, lower concentrations of free leucine were observed in older adult conditions (approx. -10%), but no significant differences in proteolysis were observed overall between the models. Therefore, the digestion conditions used influenced significantly the rate and extent of proteolysis in the gastric phase but not in the intestinal phase.

The impacts and mechanisms of dietary proteins on glucose homeostasis and food intake: a pivotal role of gut hormones

Glucose and energy metabolism disorders are the main reasons induced type 2 diabetes (T2D) and obesity. Besides providing energy, dietary nutrients could regulate glucose homeostasis and food intake via intestinal nutrient sensing induced gut hormone secretion. However, reviews regarding intestinal protein sensing are very limited, and no accurate information is available on their underlying mechanisms. Through intestinal protein sensing, dietary proteins regulate glucose homeostasis and food intake by secreting gut hormones, such as glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), peptide YY (PYY) and glucose-dependent insulinotropic polypeptide (GIP). After activating the sensory receptors, such as calcium-sensing receptor (CaSR), peptide transporter-1 (PepT1), and taste 1 receptors (T1Rs), protein digests induced Ca2+ influx and thus triggered gut hormone release. Additionally, research models used to study intestinal protein sensing have been emphasized, especially several innovative models with excellent physiological relevance, such as co-culture cell models, intestinal organoids, and gut-on-a-chips. Lastly, protein-based dietary strategies that stimulate gut hormone secretion and inhibit gut hormone degradation are proposed for regulating glucose homeostasis and food intake.

An In Vitro Comparison of the Digestibility and Gastrointestinal Fate of Scallops and Plant-Based Scallop Analogs

Concerns exist regarding the negative environmental impact and health risks associated with ocean fishing and aquaculture, such as stock depletion, pollution, biodiversity loss, and toxin presence. To address these concerns, plant-based seafood analogs are being developed. Our previous study successfully created plant-based scallop analogs using pea proteins and citrus pectin, resembling real scallops in appearance and texture. This study focuses on comparing the digestive fate of these analogs to real scallops, as it can impact their nutritional properties. Using an in vitro digestion model (INFOGEST), we simulated oral, gastric, and small intestinal conditions. The analysis revealed differences in the microstructure, physicochemical properties, and protein digestibility between the plant-based scallops and real scallops. The particle size and charge followed the following similar trends for both types of scallops: the particle size decreased from the mouth to the stomach to the small intestine; the particles were negative in the mouth, positive in the stomach, and negative in the small intestine. The protein digestibility of the plant-based scallops was considerably lower than that of real scallops. For instance, around 18.8% and 61.4% of protein was digested in the stomach and small intestine phases for the real scallop (80.2% total digestion), whereas around 8.7% and 47.7% of the protein was digested for the plant-based scallop (56.4% total digestion). The lower digestibility of the plant-based scallops may have been due to differences in the protein structure, the presence of dietary fibers (pectin), or antinutritional factors in the plant proteins. These findings are crucial for developing more sustainable next-generation plant-based seafood analogs.

Adult and elderly in vitro digestibility patterns of proteins and carbohydrates as affected by different commercial bread types

Carbohydrate and protein digestibility were assessed in different commercial bread types, i.e., soft, durum, and whole wheat, by applying in vitro digestion protocols mimicking adult or elderly physiological conditions. Protein digestibility was measured after the gastric and intestinal phases by the o-phthalaldehyde spectrophotometric assay (OPA). Carbohydrate digestibility was assessed by determining the incremental area under glucose curve during the intestinal phase of digestion to estimate the glycaemic index (GI_e). Finally, the correlation between protein and carbohydrate digestibility was computed. Bread proteins presented a high gastric resistance, with a digestibility < 10% in all cases while after the intestinal phase, protein digestibility increased, ranging from 40 to 70%. Protein digestibility was affected both by formulation, with whole wheat bread presenting the lowest values, and by physiological conditions, with restrained digestibility under elderly conditions compared to adult ones. The GI_e decreased in the order durum > soft > whole, under both adult (119, 101, and 82, respectively) and elderly (107, 93, and 65, respectively) conditions. The extent of differences under different physiological settings varied depending on the bread type, without significant changes for soft wheat bread (ΔGI_e = 8), whereas elderly conditions significantly reduced GI_e both for durum (ΔGI_e = 12) and whole (ΔGI_e = 17) wheat bread. An almost strong positive correlation between protein digestibility and GI_e was observed (p = 0.69), indicating that concomitantly addressing sarcopenia and type 2 diabetes can only be pursued by a compromise solution or more desirably requires identifying technological strategies to maximize protein digestibility while restraining the glycaemic response.

Nutritional Evaluation of Milk-, Plant-, and Insect-Based Protein Materials by Protein Digestibility Using the INFOGEST Digestion Method

The INFOGEST method is a valuable tool for understanding and monitoring food digestion as an alternative to in vivo assays. However, few studies have compared animal and alternative protein sources in terms of protein quality using the INFOGEST method. This study aimed to evaluate the protein quality of milk-, plant-, and insect-based protein materials by in vitro protein digestibility and in vitro digestible indispensable amino acid score (DIAAS), following the INFOGEST method. Milk-based protein materials had the highest protein digestibility (86.1-90.8%), followed by soy (85.1%) and wheat (82.3%). These materials had significantly higher protein digestibility compared with zein (65.1%), cricket (63.6%), and mealworm (69.5%). Additionally, the mean values of in vitro DIAAS of milk-based protein materials (105.0-137.5) were higher than those of plant- and insect-based protein materials (1.9-91.0). Milk-based protein materials have higher protein quality than plant- and insect-based protein materials by the nutritional evaluation following the INFOGEST digestion method.