Multi-criteria assessment of pea protein quality in rats: a comparison between casein, gluten and pea protein alone or supplemented with methionine

Effects of gastric bypass on the digestibility and postprandial metabolic fate of 15N dietary protein in rats

Roux-en-Y Gastric Bypass may be associated with an alteration of protein bioavailability in relation to intestinal remodeling. Our study aimed to test this hypothesis by Roux-en-Y Gastric Bypass. Diet-induced obese rats underwent Roux-en-Y Gastric Bypass surgery (RYGB rats) while a Sham-operated control group was used. All rats received a 15N-labeled protein meal 1 or 3 months after surgery and were euthanized 6h later. Protein digestibility, 15N recovered in organs and urea pool, fractional protein synthesis rate, and intestinal morphometry were assessed. Protein digestibility was similar in all groups (94.2±0.3%). The small intestine was hypertrophied in RYGB rats 1 month after surgery, weighing 9.1±0.2g vs. 7.0±0.3g in Sham rats (P = 0.003). Villus height and crypt depth were increased in the alimentary limb and ileum of RYGB rats. However, Roux-en-Y Gastric Bypass had no impact on the fractional synthesis rate. In the gastrointestinal tract, 15N retention only differed in the ileal mucosa and was higher in RYGB rats at 1 month (0.48±0.2% vs. 0.3±0.09%, P = 0.03). 15N recovery from the liver, muscle, and skin was lower in RYGB rats at 1 month. 15N recovery from urinary and plasma urea was higher in RYGB rats at both times, resulting in increased total deamination (13.2±0.9% vs. 10.1±0.5%, P<0.01). This study showed that Roux-en-Y Gastric Bypass did not affect protein digestibility. Dietary nitrogen sequestration was transitorily and moderately diminished in several organs. This was associated with a sustained elevation of postprandial deamination after Roux-en-Y Gastric Bypass, whose mechanisms merit further studies.

Minimal processed infant formula vs. conventional shows comparable protein quality and increased postprandial plasma amino acid kinetics in rats

During industrial processing, heat treatments applied to infant formulas may affect protein digestion. Recently, innovative processing routes have been developed to produce minimally heat-processed infant formula. Our objective was to compare the in vivo protein digestion kinetics and protein quality of a minimally processed (T−) and a heat-treated (T+++) infant formula. Sixty-eight male Wistar rats (21 d) were fed with either a diet containing 40 % T− (n 30) or T+++ (n 30), or a milk protein control diet (n 8) during 2 weeks. T− and T+++ rats were then sequentially euthanised 0, 1, 2, 3 or 6 h (n 6/time point) after ingestion of a meal containing their experimental diet. Control rats were euthanised 6 h after ingestion of a protein-free meal to determine nitrogen and amino acid endogenous losses. Nitrogen and amino acid true caecal digestibility was high for both T− and T+++ diets (> 90 %), but a tendency towards higher nitrogen digestibility was observed for the T− diet (96·6 ± 3·1 %) compared with the T+++ diet (91·9 ± 5·4 %, P = 0·0891). This slightly increased digestibility led to a greater increase in total amino acid concentration in plasma after ingestion of the T− diet (P = 0·0010). Comparable protein quality between the two infant formulas was found with a digestible indispensable amino acid score of 0·8. In conclusion, this study showed that minimal processing routes to produce native infant formula do not modify protein quality but tend to enhance its true nitrogen digestibility and increase postprandial plasma amino acid kinetics in rats.

Structure and functionality of whey protein, pea protein, and mixed whey and pea proteins treated by pH shift or high-intensity ultrasound

Three modifications (pH shift, ultrasound, combined pH shift and ultrasound) induced alterations in pure whey protein isolate (WPI), pea protein isolate (PPI), and mixed whey and pea protein (WPI-PPI) were investigated. The processing effect was related to the protein type and technique used. Solubility of WPI remained unchanged by various treatments. Particle size was enlarged by pH shift while reduced by ultrasound and combined approach. All methods exposed more surface hydrophobic groups on WPI, while pH shift and joint processing was detrimental to its emulsifying activity. The PPI and mixture exhibited similar responses toward the modifications. Solubility of PPI and the blend enhanced in the sequence of pH shift and ultrasound > ultrasound > pH shift. Individual approach expanded while co-handling diminished the particle diameter. Treatments also caused more disclosure of hydrophobic regions in PPI and WPI-PPI and emulsifying activity was ameliorated in the order of pH shift and ultrasound > ultrasound > pH shift.

Mixed whey and pea protein based cold-set emulsion gels induced by calcium chloride: Fabrication and characterization

The cold-set gels of oil-in-water emulsions stabilized by mixtures of whey protein isolate (WPI) and pea protein isolate (PPI) with mass ratios of 10:0, 7:3, 5:5, 3:7, and 0:10 were investigated to evaluate the possibility of pea protein to replace milk protein. Particle size and surface charge of emulsions increased and decreased with raised PPI content, respectively. The redness and yellowness of emulsion gels were strengthened with elevated pea protein percentage and independent of calcium concentration applied. Considerable differences in water holding capacity were observed between samples with different mixed proteins and high percentage of pea protein gave better water retaining ability. Gradual decreases in hardness and chewiness of emulsion gels were observed at three calcium levels with the increased PPI proportion. FT-IR spectra indicated no new covalent bonds were generated between samples with different whey and pea protein mass ratios. As PPI concentration elevated, the network structure of emulsion gels gradually became loose and disordered. The established cold-set calcium-induced whey/pea protein composite gels may have the potential to be utilized as a new material to encapsulate and deliver environment sensitive bio-active substances.

Evaluating Brewers' Spent Grain Protein Isolate Postprandial Amino Acid Uptake Kinetics: A Randomized, Cross-Over, Double-Blind Controlled Study

Valorization and utilization of brewers' spent grain (BSG) are of great interest in terms of reducing food waste and promoting more sustainable food systems. In this study, we aimed to evaluate the nutritional value of upcycled barley/rice proteins (BRP) extracted from BSG and compare this with pea proteins (PP). A randomized, cross-over, double-blind controlled trial was conducted with twelve participants (age: 24 ± 2.8 years, BMI: 23.3 ± 3.0 kg/m²). During three separate visits with a one-week washout period between visits, participants received 20 g BRP, PP, or the benchmark protein whey (WP). Blood-free amino acids (AA) were measured to determine postprandial AA uptake kinetics. The estimated total AA (TAA) uptake of BRP was 69% when compared to WP and 87% when compared to PP. The time to reach the maximum values was similar between the three protein sources. When comparing individual essential AA responses between BRP and PP, we observed higher responses in methionine and tryptophane and lower responses in lysine, histidine, and isoleucine for BRP compared to PP. This study demonstrates that BRP exhibits comparable postprandial TAA uptake profiles to PP. The findings highlight the complementarity of BRP and PP, which may offer the potential for blending approaches to optimize protein quality for overall health.

Differential effects of milk proteins on amino acid digestibility, post-prandial nitrogen utilization and intestinal peptide profiles in rats

OBJECTIVE

The aim of this study was to analyze the protein digestibility and postprandial metabolism in rats of milk protein matrices obtained by different industrial processes.

MATERIAL AND METHODS

The study was conducted on Wistar rats that consumed a meal containing different ¹⁵N-labeled milk proteins. Four milk matrices were tested: native micellar caseins (C1), caseins low in calcium (C2 low Ca²⁺), a matrix containing a ratio 63:37 of caseins and whey proteins (CW2) and whey proteins alone (W). Blood and urine were collected during the postprandial period and rats were euthanized 6 h after meal intake to collect digestive contents and organs.

RESULTS

Orocaecal digestibility values of amino acids ranged between 96.0 ± 0.2% and 96.6 ± 0.4% for C1-, C2 low Ca²⁺- and W-matrices, while this value was significantly lower for CW2 matrix (92.4 ± 0.5%). More dietary nitrogen was sequestered in the splanchnic area (intestinal mucosa and liver) as well as in plasma proteins after ingestion of W matrix, especially compared to the C1- and C2 low Ca²⁺-matrices. Peptidomic analysis showed that more milk protein-derived peptides were identified in the caecum of rats after the ingestion of the matrices containing caseins compared to W matrix.

CONCLUSION

We found that demineralization of micellar caseins did not modify its digestibility and postprandial metabolism. The low digestibility of the modified casein-to-whey ratio matrix may be ascribed to a lower accessibility of the protein to digestive enzymes due to changes in the protein structure, while the higher nitrogen splanchnic retention after ingestion of whey was probably due to the fast assimilation of its protein content. Finally, our results showed that industrial processes that modify the structure and/or composition of milk proteins influence protein digestion and utilization.

Compared with Milk Protein, a Wheat and Pea Protein Blend Reduces High-Fat, High-Sucrose Induced Metabolic Dysregulations while Similarly Supporting Tissue Protein Anabolism in Rats

BACKGROUND

Plant proteins (PPs) have been associated with better cardiovascular health than animal proteins (APs) in epidemiological studies. However, the underlying metabolic mechanisms remain mostly unknown.

OBJECTIVES

Using a combination of cutting-edge isotopic methods, we aimed to better characterize the differences in protein and energy metabolisms induced by dietary protein sources (PP compared with AP) in a prudent or western dietary context.

METHODS

Male Wistar rats (n = 44, 8 wk old) were fed for 4.5 mo with isoproteic diets differing in their protein isolate sources, either AP (100% milk) or PP (50%:50% pea: wheat) and being normal (NFS) or high (HFS) in sucrose (6% or 15% kcal) and saturated fat (7% or 20% kcal), respectively. We measured body weight and composition, hepatic enzyme activities and lipid content, and plasma metabolites. In the intestine, liver, adipose tissues, and skeletal muscles, we concomitantly assessed the extent of amino acid (AA) trafficking using a ¹⁵N natural abundance method, the rates of macronutrient routing to dispensable AA using a ¹³C natural abundance method, and the metabolic fluxes of protein synthesis (PS) and de novo lipogenesis using a ²H labeling method. Data were analyzed using ANOVA and Mixed models.

RESULTS

At the whole-body level, PP limited HFS-induced insulin resistance (-27% in HOMA-IR between HFS groups, P < 0.05). In the liver, PP induced lower lipid content (-17%, P < 0.01) and de novo lipogenesis (-24%, P < 0.05). In the different tissues studied, PP induced higher AA transamination accompanied by higher routings of dietary carbohydrates and lipids toward dispensable AA synthesis by glycolysis and β-oxidation, resulting in similar tissue PS and protein mass.

CONCLUSIONS

In growing rats, compared with AP, a balanced blend of PP similarly supports protein anabolism while better limiting whole-body and tissue metabolic dysregulations through mechanisms related to their less optimal AA profile for direct channeling to PS.

Microalgae protein digestibility: How to crack open the black box?

Microalgae are booming as a sustainable protein source for human nutrition and animal feed. Nevertheless, certain strains were reported to have robust cell walls limiting protein digestibility. There are several disruption approaches to break down the cell integrity and increase digestive enzyme accessibility. This review's intent is to discuss the digestibility of microalgae proteins in intact cells and after their disruption. In intact single cells, the extent of protein digestibility is chiefly related to cell wall structural properties (differing among strains) as well as digestion method and when added to food or feed protein digestibility changes depending on the matrix's composition. The degree of effectiveness of the disruption method varies among studies, and it is complicated to compare them due to variabilities in digestibility models, strains, disruption method/conditions and their consequent impact on the microalgae cell structure. More exhaustive studies are still required to fill knowledge gaps on the structure of microalgal cell walls and to find efficient and cost-effective disruption technologies to increase proteins availability without hindering their quality.

Caecal digestibility as an approximation of ileal protein digestibility evaluation in rats

The rat model can be used to assess ileal protein digestibility rapidly and in first intention, but no standardised method exists. Our objective was to compare methods to assess protein digestibility, depending on collection site (ileum/caecum) and use of a non-absorbable marker. A meal containing either casein, gluten or pea protein and chromium oxide as non-absorbable marker was given to male Wistar rats and the entire digestive content was collected 6 h later. Total chromium recovery was incomplete and variable, depending on protein source. We observed no significant difference in digestibility between the methods for any of the protein sources tested. Although none of the methods tested is optimal, our results suggest that caecal digestibility can be used as a proxy of ileal digestibility in rats without using a non-absorbable marker. This simple method makes it possible to evaluate protein digestibility of new alternative protein sources for human consumption.

Moderate adiposity levels counteract protein metabolism modifications associated with aging in rats

PURPOSE

Physiological parameters such as adiposity and age are likely to influence protein digestion and utilization. The aim of this study was to evaluate the combined effects of age and adiposity on casein protein and amino acid true digestibility and its postprandial utilization in rats.

METHODS

Four groups were included (n = 7/8): 2 months/normal adiposity, 2 months/high adiposity, 11 months/normal adiposity and 11 months/high adiposity. Rats were given a calibrated meal containing ¹⁵N-labeled casein (Ingredia, Arras, France) and were euthanized 6 h later. Digestive contents were collected to assess protein and amino acid digestibilities. ¹⁵N enrichments were measured in plasma and urine to determine total body deamination. Fractional protein synthesis rate (FSR) was determined in different organs using a flooding dose of ¹³C valine.

RESULTS

Nitrogen and amino acid true digestibility of casein was around 95-96% depending on the group and was increased by 1% in high adiposity rats (P = 0.04). Higher adiposity levels counteracted the increase in total body deamination (P = 0.03) that was associated with older age. Significant effects of age (P = 0.006) and adiposity (P = 0.002) were observed in the muscle FSR, with age decreasing it and adiposity increasing it.

CONCLUSION

This study revealed that a higher level of adiposity resulted in a slight increase in protein and individual amino acid true digestibility values and seemed to compensate for the metabolic postprandial protein alterations observed at older age.

Using the dual isotope method to assess cecal amino acid absorption of goat whey protein in rats, a pilot study

Measurement of ileal amino acids (AA) bioavailability is recommended to evaluate protein quality. A dual isotope tracer method, based on plasma isotopic enrichment ratios, has been proposed to determine true digestibility in humans. In a pilot study, we aimed to evaluate whether this method could be implemented in rats to determine AA bioavailability based on isotopic enrichment ratios measured in cecal digesta or plasma samples. Goat milk proteins were intrinsically labeled with ¹⁵N and ²H. Wistar rats were fed a meal containing the doubly labeled goat whey proteins and a tracer dose of ¹³C-spirulina. Blood samples were collected 0, 1 h and 3 h after meal ingestion from the tail vein. The rats were euthanized 4 h (n = 6) or 6 h (n = 6) after meal to collect plasma and intestinal contents. True orocecal protein digestibility and AA bioavailability were assessed by means of ¹⁵N and ²H enrichment in cecum content and compared with absorption indexes determined at the plasma or cecum level using isotopic ratios. Plasma kinetics of isotopic enrichment could not be completed due to the limited quantity of plasma obtained with sequential blood collection. However, the absorption indexes determined from cecal ¹⁵N or ²H/¹³C ratios gave coherent values with true orocecal AA bioavailability. This dual isotope approach with measurements of isotopic ratios in digestive content could be an interesting strategy to determine true AA bioavailability in ileal digesta of rats.

Real ileal amino acid digestibility of pea protein compared to casein in healthy humans: a randomized trial

BACKGROUND

It is necessary to propose plant alternatives to animal proteins that are of good nutritional quality. Pea is a good candidate owing to its high protein content and its well-balanced amino acid (AA) profile.

OBJECTIVES

This study aimed to assess the real ileal AA and nitrogen digestibility (RIDAA and RIDN) of pea protein isolate as compared to milk casein in humans. It also aimed to evaluate their nutritional quality through calculation of the digestible indispensable amino acid score (DIAAS) and to determine the net postprandial protein utilization (NPPU).

METHODS

Fifteen healthy volunteers were included in a randomized, single-blinded, 2-arm, parallel-design trial. They were equipped with a naso-ileal tube. They ingested the test meals, which consisted of 9 successive portions of mashed potatoes containing either pea protein or casein, intrinsically labeled with nitrogen 15. Ileal content, plasma, and urine samples were collected regularly over an 8-h postprandial period.

RESULTS

The mean RIDAA values were 93.6% ± 2.9% for pea protein and 96.8% ± 1.0% for casein, with no difference between the sources (P = 0.22). Leucine, valine, lysine, and phenylalanine were significantly less digestible in pea than in casein. The RIDN values were 92.0% ± 2.7% and 94.0% ± 1.7% for pea protein and casein, respectively, and were not different (P = 0.11). The DIAAS was 1.00 for pea protein and 1.45 for casein. The NPPU was 71.6% ± 6.2% and 71.2% ± 4.9% for pea protein and casein, respectively (P = 0.88).

CONCLUSIONS

Although some AAs are less digestible in pea protein than in casein, the real ileal digestibility and the NPPU were not different. The DIAAS of 1.00 obtained for pea protein demonstrated its ability to meet all AA requirements. This study shows the potential of pea isolate as a high-quality protein. This study was registered at clinicaltrials.gov as NCT04072770.

Pea Proteins Have Anabolic Effects Comparable to Milk Proteins on Whole Body Protein Retention and Muscle Protein Metabolism in Old Rats

Plant proteins are attracting rising interest due to their pro-health benefits and environmental sustainability. However, little is known about the nutritional value of pea proteins when consumed by older people. Herein, we evaluated the digestibility and nutritional efficiency of pea proteins compared to casein and whey proteins in old rats. Thirty 20-month-old male Wistar rats were assigned to an isoproteic and isocaloric diet containing either casein (CAS), soluble milk protein (WHEY) or Pisane™ pea protein isolate for 16 weeks. The three proteins had a similar effect on nitrogen balance, true digestibility and net protein utilization in old rats, which means that different protein sources did not alter body composition, tissue weight, skeletal muscle protein synthesis or degradation. Muscle mitochondrial activity, inflammation status and insulin resistance were similar between the three groups. In conclusion, old rats used pea protein with the same efficiency as casein or whey proteins, due to its high digestibility and amino acid composition. Using these plant-based proteins could help older people diversify their protein sources and more easily achieve nutritional intake recommendations.

Safety of mung bean protein as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on mung bean protein as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF, which is the subject of the application, is mung bean protein extracted from seeds of the plant Vigna radiata. The NF is proposed to be used as a food ingredient added to 'protein products, excluding products covered in category 1.8'. The target population is the general population. The maximum estimated intake of the NF is 758 and 260 mg/kg body weight (bw) per day in children and adults, respectively. The major constituents of this NF are protein (~85%), fat (3-4%) and moisture (3-5.5%). The NF is rich in protein which is well digestible and provides sufficient amounts of most essential amino acids but only limited amounts of sulfur-containing amino acids. The Panel notes that the cumulative exposure to the minerals analysed does not raise concern. The reported values for the levels of antinutritional factors in the NF are comparable to those in other foodstuffs. The Panel considers that taking into account the composition of the NF and the proposed conditions of use, consumption of the NF is not nutritionally disadvantageous. No toxicological studies with the NFs were provided by the applicant; however, the Panel considers that no toxicological studies are required on this NF. This NF has the potential capacity to sensitise individuals and to induce allergic reactions in individuals allergic to soybean, peanuts, lupin and to birch pollen. The Panel considers that the NF, i.e. mung bean protein, is safe at the proposed conditions of use.