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Dietary antinutritional factors have been reported to adversely affect the digestibility of protein, bioavailability of amino acids and protein quality of foods. Published data on these negative effects of major dietary antinutritional factors are summarized in this manuscript. Digestibility and the quality of mixed diets in developing countries are considerably lower than of those in developed regions. For example, the digestibility of protein in traditional diets from developing countries such as India, Guatemala and Brazil is considerably lower compared to that of protein in typical North American diets (54–78 versus 88–94 %). Poor digestibility of protein in the diets of developing countries, which are based on less refined cereals and grain legumes as major sources of protein, is due to the presence of less digestible protein fractions, high levels of insoluble fibre, and/or high concentrations of antinutritional factors present endogenously or formed during processing. Examples of naturally occurring antinutritional factors include glucosinolates in mustard and canola protein products, trypsin inhibitors and haemagglutinins in legumes, tannins in legumes and cereals, gossypol in cottonseed protein products, and uricogenic nucleobases in yeast protein products. Heat/alkaline treatments of protein products may yield Maillard reaction compounds, oxidized forms of sulphur amino acids, D-amino acids and lysinoalanine (LAL, an unnatural nephrotoxic amino acid derivative). Among common food and feed protein products, soyabeans are the most concentrated source of trypsin inhibitors. The presence of high levels of dietary trypsin inhibitors from soyabeans, kidney beans or other grain legumes have been reported to cause substantial reductions in protein and amino acid digestibility (up to 50 %) and protein quality (up to 100 %) in rats and/or pigs. Similarly, the presence of high levels of tannins in sorghum and other cereals, fababean and other grain legumes can cause significant reductions (up to 23 %) in protein and amino acid digestibility in rats, poultry, and pigs. Normally encountered levels of phytates in cereals and legumes can reduce protein and amino acid digestibility by up to 10 %. D-amino acids and LAL formed during alkaline/heat treatment of lactalbumin, casein, soya protein or wheat protein are poorly digestible (less than 40 %), and their presence can reduce protein digestibility by up to 28 % in rats and pigs, and can cause a drastic reduction (100 %) in protein quality, as measured by rat growth methods. The adverse effects of antinutritional factors on protein digestibility and protein quality have been reported to be more pronounced in elderly rats (20-months old) compared to young (5-weeks old) rats, suggesting the use of old rats as a model for assessing the protein digestibility of products intended for the elderly.

In 1989 the Joint FAO/WHO Expert Consultation on Protein Quality Evaluation recommended the use of the Protein Digestibility Corrected Amino Acid Score (PDCAAS) method for evaluating protein quality. In calculating PDCAAS, the limiting amino acid score (i.e., ratio of first limiting amino acid in a gram of target food to that in a reference protein or requirement) is multiplied by protein digestibility. The PDCAAS method has now been in use for 20 years. Research emerging during this time has provided useful data on various aspects of protein quality evaluation that has made a review of the current methods used in assessing protein quality necessary. This paper provides an overview of the use of the PDCAAS method as compared to other methods and addresses some of the key challenges that remain in regards to protein quality evaluation. Furthermore, specific factors influencing protein quality including the effects of processing conditions and preparation methods are presented. Protein quality evaluation methods and recommended protein intakes currently used in different countries vis-à-vis the WHO/FAO/UNU standards are further provided. As foods are frequently consumed in complement with other foods, the significance of the PDCAAS of single protein sources may not be evident, thus, protein quality of some key food groups and challenges surrounding the calculation of the amino acid score for dietary protein mixtures are further discussed. As results from new research emerge, recommendations may need to be updated or revised to maintain relevance of methods used in calculating protein quality.

In this review, the terminology that is used to describe the bioavailability and ileal digestibility of AA in pig feed ingredients is defined. Aspects of the methodology to establish bioavailability and ileal digestibility values also are discussed, and recommendations about the use of these values are provided. Two main factors can contribute to differences between bioavailability and ileal digestibility of AA. First, some AA, such as Lys, may be absorbed in chemical complexes that preclude their use for metabolism. Second, fermentation in the upper gut may result in a net loss or gain of AA to the animal. In addition, dietary effects on the efficiency of using bioavailable AA intake for tissue growth or milk production should be considered and may be attributed to endogenous AA losses in the hindgut and the metabolic costs associated with endogenous gut protein synthesis and losses. Ileal digestibility values may be expressed as apparent ileal digestibility (AID), standardized ileal digestibility (SID), or true ileal digestibility (TID). These terms are used to specify how ileal endogenous AA losses are reflected in digestibility values. Ileal endogenous AA losses may be separated into basal losses, which are not influenced by feed ingredient composition, and specific losses, which are induced by feed ingredient characteristics such as levels and types of fiber and antinutritional factors. Values for AID are established when total ileal outflow of AA (i.e., the sum of endogenous losses and nondigested dietary AA) is related to dietary AA intake. A concern with the use of AID values is that these are not additive in mixtures of feed ingredients. This concern may be overcome by correcting AID values for defined basal endogenous losses of AA, which yields SID values. Furthermore, if the AID values are corrected for basal and specific endogenous losses, then values for TID are calculated. However, reliable procedures to routinely measure specific endogenous losses are not yet available. It is recommended that basal ileal endogenous losses of AA should be measured in digestibility experiments using a defined protein-free diet and that these losses are reported with observed AID and SID values. It is suggested that SID values should be used for feed formulation, at least until more information on TID values becomes available.

This research aims aim to obtain a combination of BMR mutant sorghum ( Sorghum bicolor L. Moench ) and Mirasolia diversifolia in vitro based on crude fiber digestibility, crude fat digestibility, nitrogen-free extract digestibility in ruminant rations. This study employed a Completely Randomized Design experimental framework, involving the application of four treatments, each replicated four times. The treatment consisted of A (80% BMR mutant sorghum + 20% M. diversifolia ), B (70% BMR mutant sorghum + 30% M. diversifolia ), C (60% BMR mutant sorghum + 40% M. diversifolia) , D (50% BMR mutant sorghum + 50% M. diversifolia ). The study explored various variables, including the digestibility of crude fiber, crude fat, and nitrogen-free extracts. The analysis revealed a remarkably significant impact (p < 0.01) of the treatment on the digestibility of crude fiber, crude fat, and nitrogen-free extracts. The conclusions that can be drawn from this research suggest that the combination of BMR mutant sorghum and M. diversifolia in vitro was the best in treatment C, with 60% use of BMR mutant sorghum and 40% the use of M. diversifolia with a crude fiber digestibility value of 55.84%, a crude fat digestibility value of 58.47% and a digestibility value of extract material without nitrogen of 57.68%.

Background: The study aimed to determine the apparent total tract digestibility coefficients (ATTDC) of nutrients, the apparent metabolizable energy (AME and AMEn) and the amino acid (AA) apparent ileal digestibility coefficients (AIDC)of a partially defatted (BSFp) and a highly defatted (BSFh) black soldier fly larvae meal. The experimental diets were: a basal diet and two diets prepared by substituting 250 g/kg (w/w) of the basal diet with BSFp or BSFh, respectively.Results: Significant differences were found between BSFp and BSFh meals for ATTDC of the nutrients: BSFp resulted more digestible than BSFh, except for ATTDC of CP which did not differed between meals, while a statistical trend was observed for ATTDC of DM and EE. The AME and AMEn values were significantly (P < 0.05) different between the two BSF meals, with higher levels for BSFp (16.25 and 14.87 MJ/kg DM, respectively). The AIDC of the AA in BSFp ranged from 0.44 to 0.92, while in BSFh they ranged from 0.45 to 0.99. No significant differences were observed for the AA digestibility (0.77 and 0.80 for BSFp and BSFh, respectively), except for glutamic acid, proline and serine that were more digestible in the BSFh meal (P < 0.05).Conclusions: Defatted BSF meals can be considered as an excellent source of AME and digestible AA for broilers with a better efficient nutrient digestion. These considerations suggested the effective utilization of defatted BSF larvae meal in poultry feed formulation.

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.

Protein digestibility is currently a hot research topic and is of big interest to the food industry. Different scoring methods have been developed to describe protein quality. Cereal protein scores are typically low due to a suboptimal amino acid profile and low protein digestibility. Protein digestibility is a result of both external and internal factors. Examples of external factors are physical inaccessibility due to entrapment in e.g., intact cell structures and the presence of antinutritional factors. The main internal factors are the amino acid sequence of the proteins and protein folding and crosslinking. Processing of food is generally designed to increase the overall digestibility through affecting these external and internal factors. However, with proteins, processing may eventually also lead to a decrease in digestibility. In this review, protein digestion and digestibility are discussed with emphasis on the proteins of (pseudo)cereals.

Abstract Three experiments were conducted to test the hypothesis that the standardized ileal digestibility (SID) of amino acids (AA), concentrations of digestible energy (DE) and metabolizable energy (ME), and the standardized total tract digestibility (STTD) of P in a new source of fermented soybean meal (Fermex 200) are greater than in conventional soybean meal (SBM-CV). In experiment 1, 9 barrows (initial body weight: 9.17 ± 1.03 kg) were surgically fitted with a T-cannula in the distal ileum and allotted to a triplicated 3 × 3 Latin square design. A nitrogen-free diet and 2 diets that contained cornstarch and SBM-CV or Fermex 200 as the sole source of crude protein (CP), and AA were formulated. Results indicated that there were no difference between SBM-CV and Fermex 200 for SID of CP and AA. In experiment 2, 24 growing pigs (initial body weight: 14.19 ± 1.18 kg) were housed individually in metabolism crates. Pigs were allotted to a corn-based diet or 2 diets that contained corn and SBM-CV or corn and Fermex 200. Feces and urine samples were collected using the marker-to-marker approach with 5-d adaptation and 4-d collection periods. Results indicated that the concentration of DE and ME in Fermex 200 were not different from DE and ME in SBM-CV. In experiment 3, 40 barrows (initial body weight: 11.01 ± 1.38 kg) were allotted to 1 of 4 diets with 10 replicate pigs per diet. Four diets were formulated to contain Fermex 200 or SBM-CV and either 0 or 1,000 units/kg of microbial phytase. Pigs were housed individually in metabolism crates. Fecal samples were collected as explained for experiment 2. Results indicated that the STTD of P in Fermex 200 was greater (P < 0.01) than in SBM-CV, but the addition of microbial phytase to the diets increased the ATTD and STTD of P in SBM-CV, but not in Fermex 200 (interaction; P < 0.01). In conclusion, the SID of AA and concentrations of DE and ME in Fermex 200 were not different from values determined for SBM-CV, but the STTD of P was greater in Fermex 200 than in SBM-CV if microbial phytase was not added to the diet.

Despite being low in crude protein, on a fresh weight basis, given their overall contribution to the North American diet, potatoes contribute approximately 2%–4% of the population's protein intake. However, the quality of the protein remains ill‐defined. To that end, Russet potatoes were secured and subjected to various cooking conditions (raw [control], boiled, baked, microwaved, and fried [3, 6, and 9 min]) to determine the impact of cooking method on protein quality, as determined by amino acid score (AAS) and indices of in vivo true fecal protein digestibility (TFPD%; rodent bioassay) and in vitro protein digestibility (pH‐drop, pH‐Stat, and simulated gastrointestinal digestion both static and dynamic). The AAS of raw Russet potatoes was 0.67 ± 0.01, with histidine being the limiting AA. Frying led to a significant reduction in the AAS, however, other cooking methods yielded similar results to the raw control. The TFPD% of raw potato was low (40.5% ± 3.9%) and was significantly enhanced to over 80% with all cooking methods. Similar patterns were observed with all in vitro measures, however, all methods yielded higher values for the raw control samples. Final protein digestibility‐corrected AAS (PDCAAS; product of AAS and TFPD%) values ranged from 0.27 (raw) to a high of 0.57 (boiled), with cooked values being comparable to other plant‐based protein sources, including grains, and some nuts and pulses. In vitro PDCAAS values followed similar trends. This study defined the protein quality of cooked Russet potatoes and provides data for use in defining the quality of total protein consumed in the North American diet. The protein digestibility‐corrected amino acid score (PDCAAS) of Russet potatoes subjected to various cooking methods ranged between 0.27 (raw) and a high of 0.57 (boiled), with cooked values being comparable to other plant‐based protein sources, including grains, and some nuts and pulses. In vitro PDCAAS values followed similar trends. This study defined the protein quality of cooked Russet potatoes and provides data for use in defining the quality of total protein consumed in the North American diet.

Green leafy vegetables (GLV) are known for their cardiovascular health benefits. However, the effects of their serving size on delaying carbohydrate and lipid digestion remain unclear. This study investigated the impact of varying MyPlate-recommended GLV serving sizes on the digestibility of carbohydrates and lipids and antioxidant activity during in vitro gastrointestinal digestion. Eight GLV including Asteraceae (cos, green oak, red oak, loose-leaf) and Brassicaceae (cabbage, cauliflower, broccoli, Chinese cabbage) vegetables were incorporated into mixed meals at 0.5, 1.0, and 1.5 times the MyPlate recommendation. The results showed that the total phenolic content (TPC) ranged from 5.77 to 9.46 mg GAE/g extract. Nitrate accumulation exhibited a higher content in Asteraceae (590.90-1155.04 mg NO 3 -NE/g extract) than in Brassicaceae families (244.96–726.20 mg NO 3 -NE/g extract). Incorporating ≥ 1 serving of all GLV significantly decreased rapidly and slowly digestible starch fractions, while undigestible starch significantly increased, resulting in delaying glucose release. Antioxidant activity was significantly enhanced with ≥ 1 serving and free fatty acid concentrations decreased with higher vegetable servings. Post-digestion nitrate concentrations ranged from 127.3 to 188.5 µg NO 3 -N/mL, positively correlating with GLV serving size. These effects were dose-dependent and varied across species. These findings suggest that incorporating GLV at or above the MyPlate recommendation may have protective effects on cardiovascular health.