Cooking temperature is a key determinant of in vitro meat protein digestion rate: investigation of underlying mechanisms

Animal-derived and plant-derived proteins in diets have different in vitro digestive characteristics and bioaccessibility

Protein is an indispensable nutrient source for the human body. However, the underlying mechanisms for the variations in digestibility and bioaccessibility of proteins from different sources in the food matrix remain unclear. This study aims to investigate the digestive characteristics and bioaccessibility of proteins in diets from different sources. The diet contain pork-derived protein, beef-derived protein, casein, and soy protein were used to assess the physicochemical properties and microstructural changes during simulated in vitro digestion. The results indicated that the characteristics of the digestive system, as reflected by zeta potential, particle size distribution, and apparent viscosity, significantly affected the protein digestibility. It was emphasized that protein secondary structure may be the primary factor contributing to differences in system stability and digestion product, the higher content of α-helix results in the high digestibility of casein, while the tight structure of the β-sheet results in the low digestibility of soy protein. Casein demonstrated the highest digestibility, while pork-derived protein showed relatively high amino acid bioaccessibility. These findings enhance our understanding of protein bioaccessibility and may inform the development of high-protein functional foods.

Investigation of changes in the in vitro digestive properties of mirror carp (Cyprinus carpio L.) during postmortem storage based on protein degradation and oxidation

Dynamic changes in the in vitro digestive properties of postmortem mirror carp (Cyprinus carpio L.) at various intervals (0, 4, 24, 72, 120, and 168 h) under refrigerated conditions (4 °C) were evaluated based on protein degradation and oxidative reactions. Results indicated that protein degradation and oxidation intensified over storage time, as evidenced by increases in total viable counts, β-sheet content, and surface hydrophobicity, alongside decreases in α-helix content and fluorescence intensity (p < 0.05). The myofibril fragmentation index and TCA-soluble peptide levels peaked at 72.90 and 6.91 μmol tyrosine/g, respectively, whereas the total sulfhydryl content dropped to 50.25 μmol/g after 168 h postmortem. In vitro simulated gastrointestinal digestion experiments further demonstrated that aging enhanced protein digestibility. This study elucidates the postmortem dynamic patterns of freshwater fish, providing a theoretical basis for quality regulation.

True ileal amino acid digestibility and digestible amino acid scores (DIAASs) of the cruciferin and napin fractions of rapeseed: Impact of processing

Processes are being developed to exploit proteins from the residue of rapeseed oil extraction. Two main fractions of proteins can be purified: cruciferin and napin. The present work was carried out to characterize the nutritional quality of these fractions, while exploring the effect of the extraction conditions (neutral or acid), and that of the post extraction process (heating 1 h, 120 °C). The true ileal digestibility (TID) of their amino acids (AA) was measured in minipigs, to calculate the digestible indispensable amino acid score (DIAAS). The TID of cruciferin was high (95 %) compared to that of napin (87 %). The extraction process and the heat treatment had no effect on the TID of napin. The DIAAS for adults was 117 % for cruciferin, and 82-89 % for napin (branched-chain AA being the limiting AA). Improving the TID of napin would enable this interesting source of cysteine and lysine to be better exploited in human nutrition.

Protein oxidation and its effect on functional properties of livestock products during the processing and storage: A review

Protein oxidation is a complex chemical process that pervades the entirety of the food domain. It is governed by two primary mechanisms: the direct oxidation by active entities and the indirect oxidation by secondary oxidation byproducts like lipid oxidation, influenced by many factors. The oxidation of proteins in livestock products readily occurs post-processing and storage through techniques such as freezing, cooking, ultrasonication, among others, leading to protein carbonylation and subsequent alterations in structure. Consequently, the purpose of this manuscript is to scrutinize the impacts of conventional processing and storage methodologies on protein oxidation in livestock products, delineating potential mechanisms, action sites, and influential factors implicated in this progression. Additionally, we delve into the ramifications of protein oxidation on the processing attributes of livestock products, while venturing into forthcoming trends and obstacles to set a groundwork for ensuring and regulating the caliber of these commodities.

Thermal processing and in vitro digestion of n-3 pork: Effects on the oxidative and digestive properties of proteins and lipids

This study assessed the oxidation of proteins and lipids, as well as the digestive properties of six different sources of n-3 pork, after treatment with four thermal processing methods (sous vide (SV), steaming (ST), boiling (BO), and frying (FR)) and in vitro digestion. Results showed antioxidant (selenium) was associated with reduced oxidation of n-3 pork during processing and digestion. SV significantly reduced the oxidation of pork proteins and lipids and the loss of polyunsaturated fatty acids (PUFAs) compared with other processing methods. After in vitro digestion, SV caused n-3 pork to exhibit higher protein and lipid digestibility, increasing the bioaccessibility of α-linolenic acid (ALA) (81.04 %), eicosapentaenoic acid (EPA) (78.16 %), and docosahexaenoic acid (DHA) (77.28 %). Therefore, selenium addition was beneficial for improving the oxidative stability of pork, and SV can minimize nutrient losses during the processing and digestion of pork and improve the bioavailability of n-3 PUFAs.

Real-time tracking of the adsorption and degradation behavior of bovine serum albumin, casein, and fibrinogen on the lipid layer by optical interferometry

Different kinds of proteins interact with the digestible lipids in various ways, affecting the adsorption behavior of proteins and digestion. The ordered porous layer interferometry (OPLI) system was constructed by the silica colloidal crystal (SCC) films used to monitor the real-time binding assessment between bovine serum albumin (BSA), casein, fibrinogen, and triolein. The OPLI system reflected the changes in protein mass on the SCC films in real time through the migration of the interference spectrum of the SCC films, which was converted into the changes in optical thickness (ΔOT) that can be monitored. OPLI systematically studied the degradation of proteins by trypsin and found that the lipid layer enhanced the hydrolysis of trypsin to BSA and fibrinogen but weakened the degradation of trypsin to casein. The high OT of the lipid layer (10.45 nm) indicated that trypsin was more likely to adhere to the casein surface on the lipid layer than to hydrolyze casein. In contrast, the reduced OT (-6.40 nm) on the SCC films indicated that trypsin was more inclined to hydrolyze casein than to attach to casein. The OPLI system provided the technical basis for real-time tracking of protein hydrolysis behavior in complex food systems.

Beef- and Pork-Based Dishes from Catering Services: Composition and In Vitro Digestion Effects on Digestibility and Lipid Oxidation

Twelve meat-based dishes (beef/pork) prepared using different cooking methods and ingredients were collected from two catering services. Their nutritional composition and lipid oxidation status was analyzed. Subsequently, the samples underwent an in vitro digestion process to evaluate their digestibility and the effect of digestion on lipid oxidation. The protein content of the dishes ranged from 17% to 34%, with no clear influence from the type of meat or cooking method. Lipid content showed considerable variability (2.5-15.1%), with all dishes exhibiting a high omega-6/omega-3 ratio. In vitro dry matter digestibility ranged from 58% to 86%, protein digestibility from 77% to 93%, and lipid digestibility from 7.3% to 46%. Among all dishes, "roasted pork loin" showed the highest digestibility values. Regarding lipid oxidation, grilled samples exhibited the lowest levels before digestion (less than 0.85 ppm MDA), whereas most of the roasted dishes exceeded 4 ppm MDA. After digestion, all samples-except "stewed veal-a"-suffered an increase in oxidation. Stewed dishes had the smallest increase (less than 60%) and "roasted pork meatballs" exhibited the highest increase (more than 600%). This study enhances the knowledge of the nutritional value of meat-based dishes and the impact of the digestion process.

Decoding the textural deterioration of ready-to-eat shrimp: Insights from dynamic myofibrillar protein changes during thermal sterilization

Previous research has indicated a noticeable decline in the textural properties of ready-to-eat shrimp after thermal sterilization. However, the specific deterioration pattern of these textural properties during thermal sterilization remains unclear. This study investigated the dynamic changes of myofibrillar protein during thermal sterilization and their relationship with the textural properties of ready-to-eat shrimp. The primary textural attributes, including hardness, cohesiveness, chewiness, and responsiveness, initially decreased, followed by an increase and a subsequent decrease during sterilization. With the extension of sterilization time, protein oxidation increased, leading to protein unfolding, cross-linking, and aggregate formation. The content of ordered α-helix decreased by 22.35 %, and the content of random coil increased by 21.5 %, indicating the re-degradation of protein aggregates during the final stage of thermal sterilization. Observations from fluorescence microscopy and atomic force microscopy confirmed significant aggregation and degradation of protein particles during sterilization. Therefore, the aggregation and degradation of myofibrillar protein are the primary factors contributing to the changes in the textural properties of the shrimp during thermal sterilization. These findings provide valuable insights for quality control measures in processing ready-to-eat shrimp.

Effect of different thermal processing methods and thermal core temperatures on the protein structure and in vitro digestive characteristics of beef

This study aimed to investigate the effect of different thermal processing treatments on the protein digestion characteristics of beef. The beef samples were subjected to different cooking methods, namely steaming, boiling, and roasting, and different core temperatures (75 °C, 80 °C, 85 °C, and 90 °C), and were subjected to in vitro gastrointestinal digestion simulation. All the thermal processing treatments increased the protein digestibility; the samples that were steamed at 85 °C (S85), boiled at 80 °C (B80), and roasted at 80 °C (R80) showed the biggest gains. The S85 released more peptide species after gastrointestinal digestion, according to peptididomic studies. These differences were closely related to protein structure. Thermal processing treatments resulted in a higher degree of proteolysis and looser protein conformation, as evidenced by decreased intrinsic fluorescence and electrophoretic band intensity, increased surface hydrophobicity, and the change in protein secondary structure from α-helix to β-sheet and random coil. Based on the results, S85 was identified as the optimal thermal processing treatment for enhancing the digestibility of beef protein. The results provide valuable insights into the nutritional qualities and digestion of heat-processed beef protein.

Digestion of food proteins: the role of pepsin

The nutritive value of a protein is determined not only by its amino acid composition, but also by its digestibility in the gastrointestinal tract. The interaction between proteins and pepsin in the gastric stage is the first step and plays an important role in protein hydrolysis. Moreover, it affects the amino acid release rates and the allergenicity of the proteins. The interaction between pepsin and proteins from different food sources is highly dependent on the protein species, composition, processing treatment, and the presence of other food components. Coagulation of milk proteins under gastric conditions to form a coagulum is a unique behavior that affects gastric emptying and further hydrolysis of proteins. The processing treatment of proteins, either from milk or other sources, may change their structure, interactions with pepsin, and allergenicity. For example, the heat treatment of milk proteins results in the formation of a looser curd in the gastric phase and facilitates protein digestion by pepsin. Heated meat proteins undergo denaturation and conformational changes that enhance the rate of pepsin digestion. This review provides new ideas for the design of food products containing high protein concentrations that optimize nutrition while facilitating low allergenicity for consumers.

Exploring how papaya juice improves meat tenderness and digestive characteristics in Wenchang chickens

Wenchang chicken meat, used as the primary ingredient, was combined with papaya juice in different proportions for pickling and stewing. The objective of this study was to examine the effects of papain in papaya juice on the tenderness, structure and digestive characteristics of chicken meat. Compared with that in the control group, the tenderness of Wenchang chicken meat decreased and the protein solubility increased with the increase in papaya juice concentration. Scanning electron microscopy (SEM) showed that the arrangement between muscle bundles was from dense to sparse and the surface pores of muscle bundles increased. The results showed that adding papaya juice with a 50% dilution concentration provided the best outcomes in terms of tenderness, structure and digestive characteristics of chicken. Papain in papaya juice interacts with chicken protein, further enhancing the tenderness. The addition of papaya can further improve the tenderness and digestibility of chicken meat.

High internal phase emulsion as a fat replacer: Effect on physico-chemical properties, microstructure and protein digestibility of processed meat during reheating

Excessive intake of saturated fatty acids poses health risks, necessitating the development of healthier animal fat substitutes. In this study, high internal phase emulsion (HIPE) stabilized by egg yolk-hydroxypropyl distarch phosphate (EY-HPDSP) complex was used as a fat replacer in processed meat. The effect of fat replacement ratios (0 %, 50 %, 100 %) and reheating core temperature (75 ℃, 85 ℃, 95 ℃) on physico-chemical properties, microstructure and protein digestibility of processed meat was investigated. HIPE addition enhanced the hardness, springiness and L* values, and reduced the cooking loss and TBARs values of the processed meat (P < 0.05). Moreover, the replacement of HIPE significantly increased the protein digestibility and surface hydrophobicity, decreased the free sulfhydryl content and also caused the decreases in the amount of α-helix concomitant with increases in β-sheet, random coil and β-turn contents. When reheated to the core temperatures of 75-85 ℃, the hardness, T22 and A22 and protein digestibility were not significantly affected by 50 % fat substitution. At 95 ℃, the HIPE filled in the matrix underwent destruction that reduced the springiness of fat-reduced meats. This study suggested that HIPE fabricated by EY-HPDSP complex could be a viable fat replacer for processed meat before and reheating.

Influence of NaCl and phosphate on gelation properties of chicken breast myofibrillar protein gels and its application to in vitro digestion model

To investigate the combination effect of sodium chloride and phosphates on chicken breast myofibrillar proteins, MP gels containing various molarity of NaCl (0.15, 0.30 and 0.45 M) and phosphate (0 and 0.05 M) were prepared, their rheological properties were characterized, and applied to an in vitro digestion model. MP mixture containing 0.45 M NaCl and 0.05 M phosphate had the highest viscosity. The gel strength and cooking yield of MP gels was improved by increasing of molarity of NaCl. As NaCl concentration in MP increased, sulfhydryl levels decreased, while disulfide levels increased. As NaCl and phosphate levels increase, MP gels become denser and porosity decreases, which may reduce protein digestibility. In SDS-PAGE, protein bands from MP gels containing low NaCl levels (≤ 0.30 M) degraded more rapidly during in vitro digestion. These results may support the need for the meat industry to develop low-salt meat products with improved digestibility. KEYWORDS: Chicken, Myofibrillar protein, NaCl, Phosphate, Rheological properties, In vitro digestion.

Meat products in human nutrition and health - About hazards and risks

Meat processing has a long history and involves a wide and ever-increasing range of chemical and physical processes, resulting in a heterogeneous food category with a wide variability in nutritional value. Despite the known benefits of meat consumption, observational epidemiological studies have shown associations between consumption of red and processed meat - but not white meat - and several non-communicable diseases, with higher relative risks for processed meat compared to unprocessed red meat. This has led global and regional nutrition and health organisations to recommend reducing consumption of unprocessed red meat and avoiding processed meat. A plethora of potentially implicated hazardous compounds present in meat or formed during processing or gastrointestinal digestion have been reported in the literature. However, our mechanistic understanding of the impact of meat consumption on human health is still very incomplete and is complicated by the simultaneous occurrence of multiple hazards and interactions with other food compounds and host factors. This narrative review briefly discusses hazards, risks and their assessment in the context of dietary guidelines. It is argued that more mechanistic studies of the interactive effects of meat products with other foods and food compounds in different dietary contexts are needed to refine and increase the evidence base for dietary guidelines. Importantly, the great diversity in the composition and degree of processing of processed meats should be better understood in terms of their impact on human health in order to develop a more nuanced approach to dietary guidelines for this food category.

The digestible indispensable amino acid score (DIAAS) in eggs and egg-containing breakfast meals is greater than in toast breads or hash browns served without eggs

The objectives of this experiment were to determine the digestible indispensable amino acid score (DIAAS) for eggs cooked in different forms and in traditional egg-bread or egg-hash brown combinations, and to test the hypothesis that DIAAS in eggs is greater than in breads or potatoes. Nine ileal cannulated gilts (average initial body weight: 51.1 ± 6.0 kg) were allotted to a 9 × 6 Youden square design with nine diets and six 7-day periods. Fried egg, boiled egg, scrambled egg, English muffin, Texas toast, and hash brown were included in the experiment. Six diets each contained one source of protein and three diets were combinations of fried eggs and English muffin, boiled eggs and Texas toast, or scrambled egg and hash brown. A nitrogen-free diet was also used and fed to all pigs in one period. The standardised ileal digestibility (SID) of crude protein (CP) and amino acids (AA) was calculated, and DIAAS was calculated for the individual ingredient and combined meals for children between 6 and 36 months and individuals older than 3 years. For both age groups, all cooked eggs had greater (P < 0.001) DIAAS compared with the other foods, and hash brown had greater (P < 0.001) DIAAS than both breads. All combined meals had DIAAS greater than 75 and there were no differences between measured and predicted DIAAS for the combined meals. In conclusion, eggs have 'excellent' protein quality for individuals older than 6 months and can compensate for the lower protein quality in plant-based foods, and DIAAS obtained from individual ingredients are additive in mixed meals.

Comparative Study on the Postmortem Proteolysis and Shear Force during Aging of Pork and Beef Semitendinosus Muscles

The differences in the proteolytic patterns and shear force of pork and beef during aging were evaluated. Pork and beef semitendinosus muscles were obtained at 24 and 48 h postmortem, respectively, and aged at 4°C for 0 (Day 0), 7 (Day 7), and 14 days (Day 14). Changes in the electrical conductivity were observed in pork on Day 7 and beef on Day 14. The calpain activity increased in pork (p<0.05) after 14 days of aging, whereas that of beef decreased on Day 7 (p<0.05). The cathepsin B activity in pork and beef increased between Day 7 and 14 (p<0.05). The content of α-amino group in the 10% trichloroacetic acid-soluble fraction increased between Day 7 and 14 in pork (p<0.05), but increased steadily in beef throughout aging (p<0.05). The electrophoretogram of the myofibrillar proteins revealed a 30 kDa protein band only in the beef lane on Day 14. The cooked pork had no significant changes in the shear force during aging periods (p>0.05), while the gradual decrease in the shear force with the increasing aging periods was shown in the cooked beef (p<0.05). Circular dichroism analysis of myosin extracts from pork and beef revealed thermal denaturation temperatures of 55°C and 58°C, respectively. This study highlights the different post-mortem proteolytic patterns and thermal denaturation temperatures of myosin in pork and beef semitendinosus muscles, which contribute to distinct changes in the shear force during aging between pork and beef.

Effect of baking on the structure and bioavailability of protein-binding zinc from oyster (Crassoetrea hongkongensis)

To compare the bioavailability of protein-binding zinc, we investigated the impact of baking on the structure of zinc-binding proteins. The results showed that zinc-binding proteins enriched in zinc with relative molecular weights distributed at 6 kDa and 3 kDa. Protein-binding zinc is predisposed to separate from proteins' interiors and converge on proteins' surface after being baked, and its structure tends to be crystalline. Especially -COO, -C-O, and -C-N played vital roles in the sites of zinc-binding proteins. However, baking did not affect protein-binding zinc's bioavailability which was superior to that of ZnSO4 and C12H22O14Zn. They were digested in the intestine, zinc-binding complexes that were easily transported and uptaken by Caco-2 cells, with transport and uptake rates as high as 62.15% and 15.85%. Consequently, baking can alter the conformation of zinc-binding proteins without any impact on protein-binding zinc's bioavailability which is superior to that of ZnSO4 and C12H22O14Zn.

Re-domestication of feral pigs in Martinique: first results of growing-finishing trials to test meat consumption and consumers' perceptions

In Martinique, pig production satisfies less than 20% of demand for pork, with traditional pig farming and wild pig hunting covering only a small proportion. This study has three parts: (i) for the first time, it analyses the performance of domesticated descendants of Creole feral pigs of Martinique based on a 29-day finishing test on two farms (A vs. B) with the same fibre-rich diet on a total of 40 pigs; (ii) it evaluates consumers' tastes based on a sensorial test by an untrained panel of 61 consumers who tasted pork prepared as a fricassee from either farm A or farm B; and (iii) evaluates willingness to pay (WTP) for Creole pork products and of the design of a future niche market. The average daily gain (ADG) of the finishing pigs was higher on farm A than on farm B (256 vs. 100 g/d, P < 0.001) resulting in a higher hot carcass weight on farm A than farm B (41.3 vs. 33.5 kg, P < 0.01), and better hot carcass yield on farm B than farm A (74.0 vs 68.8 %, P < 0.01). In the sensorial test, the consumers gave a higher score to the meat originating from the youngest pigs (Farm B), especially scores for tenderness and juiciness (+0.94 and +0.55 points, P < 0.05 and P=0.10, respectively). The 61 respondents were willing to pay more for processed products (sausage, pâté, ham) than for fresh meat. They considered that Creole pork has a better taste and is of better quality than industrial meats originating from mainstream genotypes. According to the majority of respondents, Creole pork should be rich in intra-muscular fat (100% of respondents) and low in inter-muscular fat (60% of respondents). Based on the survey, the main desirable future for Martinique's Creole pig production correspond to a low-carbon system with feed based on local resources, with on-farm slaughtering and short-distance sales (direct-to-consumer farm gate sale, sale at the butcher's or at the pig cooperative).

Nutritional and physicochemical characteristics of Asiatic hard clam powder prepared by different cook-drying processes: a comparative study

BACKGROUND

Asiatic hard clam (Meretrix meretrix) is an underutilized bivalve resource. This study discusses dried clam powders prepared from this resource to enhance its utilization and improve nutritional security in protein-deficient populations. Dried clam powder was prepared from Asiatic hard clam and the effects of different pre-cooking methods (boil-dried clam powder, BDCP; steam-dried clam powder, SDCP; and microwave-dried clam powder, MDCP) on nutritional (proximate composition, amino acid profiling, mineral profiling, fatty acid profiling) and physicochemical qualities were investigated.

RESULTS

Different pre-cooking methods significantly influenced the characteristics of the clam powder. The MDCP sample showed the highest concentration of amino acids, polyunsaturated fatty acids, Na, K, Ca and Mg content compared to BDCP and SDCP. The boiling process led to a loss of nutritional quality in terms of amino acids and macrominerals. The MDCP displayed the highest solubility in water (30.10%) but its oil and water absorption characteristics were the lowest among all the samples. Boil-cooked clam powder displayed the highest oil binding (2.03 mL g-1 protein) capacity. Boiling and steaming processes resulted in malondialdehyde generation compared to microwaving. Different pre-cooking processes did not influence the colour attributes significantly, but the control sample prepared without pre-cooking (CCP) had a significantly lower L* value (32.34), resulting in a darker product. In vitro digestibility of the clam powder varied in the order MDCP > SDCP > BDCP > CCP.

CONCLUSION

The study demonstrated that nutritionally rich protein powder can be prepared from Asiatic hard clam. Based on the results, microwave pre-cooking is considered the best pre-cooking method to preserve the nutritional qualities of clam powder. © 2024 Society of Chemical Industry.

Effects of heat sterilization on protein physicochemical properties and release of metabolites of braised chicken after in vitro digestion

Heat sterilization enhances the safety and shelf-life of braised chicken, but its impact on protein digestibility and the release of metabolites remains unclear. Here, braised chicken was sterilized at 80 °C (LS), 100 °C (MS), and 121 °C (HS) for 30 min. Protein digestibility was assessed by in vitro digestion, whereas the release of metabolites was analysed by UPLC-QTOF-MS spectroscopy. Results revealed that LS had higher gastrointestinal digestibility (88.86 %) than MS (81.79 %) and HS (78.13 %). Increased carbonyl content, turbidity, particle size, and hydrophobicity, along with decreased sulfhydryl content and solubility, indicated rising protein oxidation aggregation with higher sterilization temperatures, explaining reduced digestibility. 96 metabolites were identified. Compared to the control group, LS exhibited a statistically significant variation in the biosynthesis of unsaturated fatty acids, MS displayed a significant difference in purine metabolism, and HS showed a significant difference in primary bile acid biosynthesis. Thus, LS is a promising sterilization method.

Culinary treatments impact the digestibility and protein quality of edible insects: a case study with Tenebrio molitor and Gryllus assimilis

The escalating global population is anticipated to intensify the demand for high-quality proteins, necessitating the exploration of alternative protein sources. Edible insects are a promising solution, owing to their nutritional richness and sustainability. However, their digestibility and protein quality, particularly after culinary treatment, remains underexplored. In the present study, we investigated the effects of various culinary treatments on the protein digestibility of two insect species, Tenebrio molitor and Gryllus assimilis. Our findings revealed that culinary treatments such as boiling, roasting, drying, and microwave heating significantly influenced the digestibility of both insect species. Notably, drying emerged as the most effective method, leading to a substantial increase in digestibility. Furthermore, we assessed protein quality using the digestible indispensable amino acid score (DIAAS) and found that the choice of the calculation method significantly influenced the evaluation of protein quality. By including the sum of the anhydrous amino acids, we eliminated the potential overestimation of protein content and obtained a more reliable assessment of protein quality. Our results underscore the importance of culinary treatments and calculation methods in determining the suitability of insects as protein sources for human nutrition.

Natural antioxidants (rosemary and parsley) in microwaved ground meat patties: effects of in vitro digestion

BACKGROUND

Minimizing food oxidation remains a challenge in several environments. The addition of rosemary extract (150 mg kg-1) and lyophilized parsley (7.1 g kg-1) at equivalent antioxidant activity (5550 μg Trolox equivalents kg-1) to meat patties was assessed in terms of their effect during microwave cooking and after being subjected to an in vitro digestion process.

RESULTS

Regardless of the use of antioxidants, cooking caused a decrease of the fat content as compared to raw samples, without noticing statistical differences in the fatty acid distribution between raw and cooked samples [44%, 47% and 6.8%, of saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), respectively]. However, the bioaccessible lipid fraction obtained after digestion was less saturated (around 34% SFA) and more unsaturated (35% MUFA +30% PUFA). Cooking caused, in all types of samples, an increased lipid [thiobarbituric acid reactive substances (TBARS)] and protein (carbonyls) oxidation values. The increase of TBARS during in vitro digestion was around 7 mg malondialdehyde (MDA) kg-1 for control and samples with parsley and 4.8 mg MDA kg-1 with rosemary. The addition of parsley, and particularly of rosemary, significantly increased the antioxidant activity (DPPH) of cooked and digested microwaved meat patties.

CONCLUSION

Whereas rosemary was effective in minimizing protein oxidation during cooking and digestion as compared to control samples, parsley could only limit it during digestion. Lipid oxidation was only limited by rosemary during in vitro digestion. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Analytical Methods and Effects of Bioactive Peptides Derived from Animal Products: A Mini-Review

Peptides with bioactive effects are being researched for various purposes. However, there is a lack of overall research on pork-derived peptides. In this study, we reviewed the process of obtaining bioactive peptides, available analytical methods, and the study of bioactive peptides derived from pork. Pepsin and trypsin, two representative protein digestive enzymes in the body, are hydrolyzed by other cofactors to produce peptides. Bicinchoninic acid assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, chromatography, and in vitro digestion simulation systems are utilized to analyze bioactive peptides for protein digestibility and molecular weight distribution. Pork-derived peptides mainly exhibit antioxidant and antihypertensive activities. The antioxidant activity of bioactive peptides increases the accessibility of amino acid residues by disrupting the three-dimensional structure of proteins, affecting free radical scavenging, reactive oxygen species inactivation, and metal ion chelating. In addition, the antihypertensive activity decreases angiotensin II production by inhibiting angiotensin converting enzyme and suppresses blood pressure by blocking the AT1 receptor. Pork-derived bioactive peptides, primarily obtained using papain and pepsin, exhibit significant antioxidant and antihypertensive activities, with most having low molecular weights below 1 kDa. This study may aid in the future development of bioactive peptides and serve as a valuable reference for pork-derived peptides.

Investigating the impact of sous vide cooking on the eating quality of spent buffalo (BUBALUS BUBALIS) meat

This study describes the impact of sous vide cooking at different temperatures and time intervals on the eating quality, specifically tenderness of two muscles, bicep femoris (BF) and semitendinosus (ST) from spent buffalo (Bubalus bubalis). Spent buffalo refers to water buffalo that are no longer considered productive following a sixth lactation cycle. Steaks from each muscle were obtained and cooked at three combinations of time and temperature, namely 55 °C-8H, 65 °C-5H, and 95 °C-45 M, respectively. Warner-Bratzler Shear Force (WBSF), cooking loss, cooking yield, color, water activity (aw), total water content (TWC), total collagen content (TCC), heat soluble collagen (HSC), myofibrillar fragmentation index (MFI), and sensory evaluation were measured. The collagen solubilization results showed that temperature and time interacted (P ≤ 0.05), reducing the toughness of the muscles. The tenderization achieved through sous vide cooking was mainly attributed to the thermal denaturation of proteins at the typically lower temperatures and extended time used, weakening of connective tissue through collagen solubilization, and water retention. More cooking loss (P ≤ 0.05) was observed at high temperature treatment of 95 °C-45 M. Meat color, TWC, MFI, and overall acceptability exhibited differences among treatments (P ≤ 0.05). An extended heat interval at lower temperatures caused initial denaturation of myofibrillar proteins, then solubilization of connective tissue proteins. Cooking treatment 55 °C-8H (P ≤ 0.05) reduced the WBSF in both muscles; however, the ST appeared more tender than BF.

Effects of microwave processing in comparison to sous vide cooking on meat quality, protein structural changes, and in vitro digestibility

This study investigated the effect of industrial microwave (MW) processing, and sous vide (SV) on goat and lamb biceps femoris, where samples were cooked to the same tenderness. The cooked meat quality and ultrastructure were analyzed along with determining the protein surface hydrophobicity, particle size distribution, secondary structure, and protein digestibility. MW-processing resulted in higher cooking loss and more ultrastructural damage than SV and also induced higher myofibrillar protein surface hydrophobicity. Both processes caused a significant increase (p < 0.05) in the β-sheet and an increase in the random coils with a reduction (p < 0.05) in α-helix and β-turns. Both processes led to different protein hydrolysis patterns (observed through SDS-PAGE), but overall free amino N release after digestion was not significantly different among them. The results suggest that MW and SV modify meat protein structure differently, but with the same meat tenderness level, these processes can lead to similar overall protein digestibility.

Influence of overcooking on in vitro digestion and fermentation of ground beef and whole wheat bread

Areas of char or overcooking commonly appear in foods people consume. It has been reported that overcooked food is harmful to human health. However, little research exists on the effect of overcooking on digestible protein and starch content and gut microbial fermentation. This study aimed to reveal the connection between overcooking and the content of digestible protein and starch, as well as its impact on gut microbial fermentation. Digestible protein in the standard cooked ground beef patty was significantly higher than the overcooked samples (p = 0.009). Standard-cooked whole wheat bread also showed a significantly higher digestible protein content compared with overcooked (p = 0.009). A significant difference was also found in digestible starch content between standard cooked and overcooked bread samples (p = 0.02). Overcooking decreased acetate, propionate, iso-butyrate, iso-valerate and ammonia production by the gut microbiota during fermentation of the beef sample, and decreased propionate and ammonia production during fermentation of the bread sample (p < 0.05). Interestingly, overcooking enhanced butyrate production by the microbiota during fermentation of the bread sample (24 h of fermentation, p < 0.001; 48 h of fermentation, p = 0.02), while no significant difference was found between overcooked and standard cooked beef samples (24 h of fermentation, p = 0.15; 48 h of fermentation, p = 0.4). Overcooking resulted in reductions in many Pseudomonadota and favored several Bacillota, especially Ruminococcaceae and Oscillospiraceae, which contain butyrate producers. Overall, overcooking reduced digestible protein, digestible starch, and fermentation of proteins. Unexpectedly, overcooking induced several purportedly favorable effects on the gut microbiota due to the decreased protein fermentation, which, in future studies, should be weighed against the previous reports that overcooking is deleterious to human health.

Fava bean (Vicia faba L.) protein concentrate added to beef burgers improves the bioaccessibility of some free essential amino acids after in vitro oral and gastrointestinal digestion

The influence of partial replacement of animal protein by plant-based ingredients on the protein digestibility of beef burgers was investigated. Beef burgers were supplemented with fava bean protein concentrate (FB) or a mixture of FB and flaxseed flour (FBFS), both processed by extrusion, at different levels: 0 (control), 10, 15, and 20 % (w/w). A pilot sensory analysis was conducted to select the percentage of flour inclusion for further assays: control, 10 % FB, and 10 % FBFS. Protein digestibility, amino acid profile, and protein secondary structure of these burgers after in vitro oral and gastrointestinal digestion were studied. In vitro boluses were prepared with the AM2 masticator, simulating normal mastication, and static in vitro digestion of boluses was performed according to the INFOGEST method. Inclusion of 10 % FB in beef burgers did not alter their flavour or tenderness compared to the control, whereas tenderness and juiciness scored slightly higher for the 10 % FBFS burgers compared to 15 % and 20 % FBFS ones. Poor lipid oxidative stability during storage was observed with 10 % FBFS burgers. Total protein content was significantly higher (p < 0.05) in 10 % FB burgers than in control burgers after in vitro oral digestion. Additionally, 10 % FB burgers presented higher amounts of free essential amino acids like isoleucine, leucine, phenylalanine, and valine at the end of digestion, as well as methionine, tyrosine, and histidine. Partial substitution of meat protein by 10 % FB improves the nutritional profile of beef burgers, without altering their sensory qualities.

Tracing the Bioaccessibility of Per- and Polyfluoroalkyl Substances in Fish during Cooking Treatment

The effect of cooking on the contents of per- and polyfluoroalkyl substances (PFAS) in foods has been widely studied, but whether cooking-induced structural and chemical modifications in foods affect the oral bioaccessibility of PFAS remains largely unknown. In this study, three kinds of fishes with different fat contents were selected, and the bioaccessibility of PFAS during cooking treatment (steaming and frying) was evaluated using in vitro gastrointestinal simulation with gastric lipase addition. The results showed that related to their molecular structures, the bioaccessibility of an individual PFAS varied greatly, ranging from 26.0 to 108.1%. Cooking can reduce the bioaccessibility of PFAS, and steaming is more effective than oil-frying; one of the possible reasons for this result is that the PFAS is trapped in protein aggregates after heat treatment. Fish lipids and cooking oil ingested with meals exert different effects on the bioaccessibility of PFAS, which may be related to the state of the ingested lipid/oil and the degree of unsaturation of fatty acids. Gastric lipase boosted the release of long-chain PFAS during in vitro digestion, indicating that the degree of lipolysis considerably influences the bioaccessibility of hydrophobic PFAS. Estimated weekly PFAS intakes were recalibrated using bioaccessibility data, enabling more accurate and reliable dietary exposure assessments.

Protein digestion and absorption: the influence of food processing

The rates of dietary protein digestion and absorption can be significantly increased or decreased by food processing treatments such as heating, gelling and enzymatic hydrolysis, with subsequent metabolic impacts, e.g. on muscle synthesis and glucose homeostasis.This review examines in vivo evidence that industrial and domestic food processing modify the kinetics of amino acid release and absorption following a protein-rich meal. It focuses on studies that used compositionally-matched test meals processed in different ways.Food processing at extremely high temperature at alkaline pH and/or in the presence of reducing sugars can modify amino acid sidechains, leading to loss of bioavailability. Some protein-rich food ingredients are deliberately aggregated, gelled or hydrolysed during manufacture. Hydrolysis accelerates protein digestion/absorption and increases splanchnic utilisation. Aggregation and gelation may slow or accelerate proteolysis in the gut, depending on the aggregate/gel microstructure.Milk, beef and eggs are heat processed prior to consumption to eliminate pathogens and improve palatability. The temperature and time of heating affect protein digestion and absorption rates, and effects are sometimes non-linear. In light of a dietary transition away from animal proteins, more research is needed on how food processing affects digestion and absorption of non-animal proteins.Food processing modifies the microstructure of protein-rich foods, and thereby alters protein digestion and absorption kinetics in the stomach and small intestine. Exploiting this principle to optimise metabolic outcomes requires more human clinical trials in which amino acid absorption rates are measured and food microstructure is explicitly considered, measured and manipulated.

Behaviour of texture-modified meats using proteolytic enzymes during gastrointestinal digestion simulating elderly alterations

This study aimed to apply different proteolytic enzymes (bromelain, papain, and flavourzyme) to develop texture-modified meats suitable for people with chewing or swallowing problems. The samples were categorised at level 6 (soft and bite-sized food) of the dysphagia diet, characterised in terms of physicochemical and textural parameters, and evaluated for their behaviour during gastrointestinal digestion simulating elderly alterations. In general, the enzyme-treated samples had lower moisture content, weight, and diameter of the piece of meat, and presented colour differences compared to the control samples. Textural analyses did not show significant differences in terms of hardness and cohesiveness for the texture-modified meats, while flavourzyme-treated samples presented less elasticity. Instrumental mastication assay showed the breakdown of samples' structure mainly during the first mastication cycles, with flavourzyme-treated samples presenting slightly higher consistency. The protein digestibility of the meats greatly increased after simulated gastrointestinal digestion, but a decrease in proteolysis for the control and papain-treated samples in the altered gastric model and an increase for flavourzyme-treated samples in the altered both gastric and intestinal model were shown compared to standard conditions. These results allow integrating knowledge to design foods that better meet the requirements of dysphagics or elderly people.

Improvement of Microbial Quality, Physicochemical Properties, Fatty Acids Profile, and Shelf Life of Basa (Pangasius bocourti) Fillets during Chilling Storage Using Pepsin, Rosemary Oil, and Citric Acid

Meat discoloration, lipid oxidation, and undesirable texture are inevitable phenomena in basa fish fillets during storage, which in turn limits their exportation as well as decreases consumer acceptability. In addition, increasing consumers' requirements for high-quality, minimally processed, and ready-to-cook fish fillets with an extended shelf-life is a great challenge, particularly with lifestyle changes. Accordingly, this study aimed to improve the quality, lipid stability, fatty acid profile, and lipid nutritional quality indices (LNQI) of basa fish fillets during chilling storage at 4 °C for 15 days using pepsin enzyme (E, 0.1%), rosemary oil (R, 0.5%), citric acid (CA, 0.5%), and their combination (0.1% E + 0.5% R; 0.1% E + 0.5% CA; and 0.1% E + 0.5% R + 0.5% CA). Our results revealed that all treated samples exhibited a significant increase in protein content, a significant decrease in fat content, and a marked reduction in pH, total volatile base nitrogen (TVBN), thiobarbituric acid (TBA), free fatty acids, and shear force (SF) values in comparison to control ones. Moreover, significant improvements in sensory scores, color stability, fatty acid profile, LNQI, and microbial quality of all treated samples were observed. Such findings were more pronounced in samples treated with a mixture of pepsin, rosemary, and citric acid (TVBN: 2.04 vs. 6.52 mg%; TBA: 0.40 vs. 2.68 mg malonaldehyde/Kg; and SF: 8.58 vs. 19.51 Kgf). Based on the obtained results, there was an extension for the shelf life of all treated basa fish fillet samples, especially in samples treated with a mixture of pepsin, rosemary, and citric acids when compared with the control samples (˃15 days versus 10 days). Additionally, eucalyptol, camphor, isoborneol, and α-pinene are the main components of rosemary, with great antioxidant and antimicrobial activity. In conclusion, the mixture of pepsin, rosemary, and citric acid can be applied easily in the seafood industry and at the household level to provide ready-to-cook fish fillets of high quality with great health benefits.

Structure and in vitro digestion characteristics of skim goat milk protein during processing: effects of fat separation

BACKGROUND

Although nonfat milk has been used worldwide in the industrial dairy process, little is known about the effects of fat separation during the manufacturing process on skim milk's structural and digestive properties. This study investigated the effects of the manufacturing process on the structure and in vitro digestion properties of skim goat milk, particularly emphasizing fat separation.

RESULTS

Changes in the surface charge and hydrophobicity of milk proteins caused by fat separation resulted in oxidation and aggregation in the subsequent homogenization, heat and spray-drying processing, which affected its digestibility. Compared with separation by dish separator (DS), skim milk after tubular centrifugal separation (CS) showed a higher initial and final digestibility. The CS samples also had a lower surface hydrophobicity level and higher free sulfhydryl content, ζ-potential, and average particle size (P < 0.05). Goat milk protein after CS was more readily oxidized and aggregated during the subsequent homogenization and heat treatment, as evidenced by the higher carbonyl content and particle size. Centrifugal separation also converted more β-sheets to α-helices, thus promoting the aggregation of oxidized skim milk protein.

CONCLUSION

The skim milk after CS and DS demonstrated different structural and digestive properties. Skim goat milk products after CS were more susceptible to oxidant-induced protein structural changes, resulting in higher protein digestibility. These findings provide insights into the mechanism involved in the control of gastric digestion of skim milk during manufacturing process. © 2023 Society of Chemical Industry.

The Effect of Heat Treatment on the Digestion and Absorption Properties of Protein in Sea Cucumber Body Wall

This study was designed, for the first time, to investigate the effect of oxidation on the digestion and absorption properties of protein in boiled sea cucumber body wall (BSCBW) via simulated digestion combined with everted-rat-gut-sac models. Boiling heat treatments led to protein oxidation in SCBW, manifested by increases in free radical intensity, thiobarbituric acid reactive substances, carbonyl groups, disulfide bonds, dityrosine bonds, advanced glycation end products, protein hydrophobicity and aggregation, and declines in both free sulfhydryl groups and secondary structure transition from α-helix to β-sheet. Boiling for 2 h caused anti-digestion collagen unfolding, provided the action site for protease and improved protein digestion and absorption levels. On the contrary, excessive oxidative modification of 4 h BSCBW resulted in decreased protein digestion and absorption levels. From the perspective of texture, digestion and absorption properties, boiling for 2 h can obtain sea cucumber products with better edible and digestible properties, which is considered to be a better processing condition.

The influence of protein oxidation on structure, pepsin diffusion, and in vitro gastric digestion of SPI emulsion

The stability behaviors of oxidized SPI emulsions under in vitro gastric conditions and the effects of pepsin diffusion on the proteolysis of emulsions were investigated using a static gastric model and the fluorescence recovery after photobleaching method. Results showed that protein oxidation increased the particle size of droplets and decreased the viscoelasticity of the interfacial layer. Compared to the control group (82.81 m²/s), the pepsin diffusivity decreased to 68.52 m²/s (7LA + LOX group) due to the space hindrance of oil droplets. After gastric digestion, protein hydrolysates were re-absorbed on the oil-water interface and formed a thick layer, thereby decreasing the size of oil droplets and reducing the contents of free amino acids in gastric digesta. The protein oxidation may affect the adsorption of interfacial proteins and alter the distribution of droplets, decreasing pepsin diffusion and ultimately impairing the emulsion gastric digestion. And this should be considered in the design of emulsion as the controllable delivery system.

The impact of age-related digestive disorders on in vitro digestibility of macronutrients and bioaccessibility of minor components of chia seeds

Gastrointestinal (GI) functions deteriorate with age, primarily affecting protein digestion. The consumption of chia seeds may be helpful for the elderly because they offer a vegetable-based source of proteins, healthy lipids, fibre and micronutrients. The impact of common age-related GI deterioration on chia seed digestibility was assessed using in vitro digestion models. The goal was to study the potential of chia seeds as part of the diet of seniors. Deterioration in the oral, gastric and intestinal stages of digestion was cumulatively assessed in three digestion models: E1 (deterioration in oral conditions), E2 (deterioration in oral and gastric conditions) and E3 (deterioration in oral, gastric and intestinal conditions). Less efficient chewing (E1) decreased proteolysis, lipolysis and antioxidant capacity (p < 0.05). In contrast, deterioration in gastric functions seemed to affect only total polyphenolic content. Finally, in the model simulating the greatest deterioration in digestive functions (E3), all measured variables were negatively affected (proteolysis, lipolysis, amino acid release, total phenolic content, antioxidant capacity and calcium). Calcium bioaccessibility fell by 24 % with a decrease in pancreatic enzymes and bile secretion (E3). Age-related reduced digestive function did not affect the ratio of essential to non-essential amino acids in the digested samples in any case. However, under suboptimal GI conditions (E3), amino acids such as valine, leucine and isoleucine, which are important for sarcopenia prevention in the elderly, fell by 39 %, 49 % and 44 %, respectively. These findings might be helpful for further in vitro studies of chia seeds as a possible food ingredient. They may also be useful for the development of more targeted nutrition strategies in the elderly.

Effect of cooking temperature on metal concentrations and speciation in fish muscle and seal liver

Fish and marine mammals constitute a significant part of the country food diet of many Indigenous communities in Canada. These animals sometimes accumulate essential elements as well as elevated levels of toxic metals. We experimentally assessed how changes in cooking temperature (23-99 °C by boiling) modified elemental concentrations in whitefish muscle and grey seal liver (two organs commonly consumed in some northern communities). Wet and dry elemental concentrations changed linearly as a function of temperature, and two patterns were observed: methylmercury, selenium, and rare earth elements tended to remain associated with the food during cooking, whereas alkali, alkaline-earth metals, and arsenic were significantly transferred to cooking juices. Mass balances indicated that speciation of mercury was stable during cooking. Because elements generally behaved similarly as those of their periodic table group or their ecotoxicological classes (A, B, intermediate), we propose that elemental behavior during cooking is partly a function of chemical affinity, and this relationship can be used to predict the behavior of data-poor elements of emerging concern, such as technology-critical elements. Furthermore, the marked increases and decreases in elemental concentrations during cooking (e.g., -14% As and +39% Se in whitefish; -22% Cd and +55% Hg in seal liver, on a wet weight basis) should be considered when assessing risk because current exposure models usually only consider elemental concentrations in raw food.

The red, firm, non-exudative and pale, soft, exudative pork have different in vitro digestive properties of protein

Pale, soft and exudative (PSE) meat has worse edible quality than red, firm and non-exudative (RFN) meat, but their difference in nutritional values is still unclear. In this study, the differences in digestive properties between PSE and RFN pork were explored, and the potential mechanisms were analyzed in terms of protein conformation. The PSE pork showed significantly higher digestibility and smaller particle size compared with RFN pork (P < 0.05) after gastrointestinal digestion. Mechanistically, the lower viscosity was seen in the PSE pork digestion system. The protein structure of PSE pork was disordered with weaker hydrogen bond and ionic bond before and after heating. In addition, the protein (mainly salt-soluble protein) of PSE pork was highly oxidized. The results suggested that higher level of oxidation in PSE pork leads to the destruction of the molecular forces, resulting in the impaired protein conformation and disordered protein structure. The serial changes caused the meat proteins more accessible to digestive enzymes, thus improving the digestibility. The findings provide new insights into the evaluating the quality of PSE meat.

Effect of Thermal Processing on the Conformational and Digestive Properties of Myosin

Heat treatment affects the structural properties of meat proteins, which in turn leads to changes in their sensitivity to digestive enzymes, further affecting the nutritional value of meat and meat products. The mechanism of changes in the structure and digestive properties of myosin under different heating conditions were studied. An increase in heating temperature led to the exposure of internal groups to a polar environment, but to a decrease in the sturdy α-helix structure of myosin (p < 0.05). The results of tryptophan fluorescence verified that the tertiary structure of the protein seemed to be unfolded at 70 °C. Higher protein denaturation after overheating, as proven by the sulfhydryl contents and turbidity, caused irregular aggregate generation. The excessive heating mode of treatment at 100 °C for 30 min caused myosin to exhibit a lower degree of pepsin digestion, which increased the Michaelis constant (Km value) of pepsin during the digestion, but induced the production of new peptides with longer peptide sequences. This study elucidates the effects of cooking temperature on the conformation of myosin and the change in digestibility of pepsin treatment during heating.

Terminal temperature dominates the gel quality of chicken meat paste: An emphasis on multiple heating-cooling regimes

A survey of various heating strategies, including terminal temperature (70 and 90 °C), step heating (with or without holding at 50 °C for 10 min) and step cooling (with or without holding at 50 °C for 10 min), on the gelation properties of chicken meat paste was conducted. Compared to 70 °C, 90 °C heating drastically increased (p < 0.05) cooking loss (CL) from 5% to > 15% since more immobilized water was pushed out as free water. Step cooling could mitigate the high-temperature-induced CL. The impact of heating strategies on the textural properties of chicken meat is much lower than that on CL. For both 70 °C and 90 °C cooked samples, step heating reduced (p < 0.05) their whiteness by increasing the yellowness. The storage modulus (G') increase during cooling is mainly driven by cooling leaded lower mobility. Overall, low-temperature ramping heating produced excellent meat gel with low energy consumption.

The degree of doneness affected molecular changes and protein digestibility of pork

The degree of doneness has been shown to have a great impact on eating quality of meat, however, it is little known whether it affects protein digestibility of meat. In this study, we explored molecular changes and protein digestibility of pork under different degree of doneness. Pork chops were cooked in a 100°C water bath for about 26 min and a gradient decrease in doneness was obtained from outer to inner layers of samples. Compared with the raw samples, the cooked samples' active and total sulfhydryl contents, surface hydrophobicity, and turbidity increased but its solubility decreased. The inner layers with lower doneness contained higher α-helix, and fluorescence intensities of tryptophan and tyrosine residues than the outer layers with higher doneness. The pepsin and pancreatin digestibility of meat proteins in the inner layers were higher than those of the outer layers. Molecular simulation analysis showed that the most abundant protein in pork, i.e., myosin in the outer layers were more stable with an increased number of hydrogen bonds, making it difficult to be digested. These findings provided a new insight into the heterogeneity of meat nutritional quality due to the existence of doneness gradient.

Methods for improving meat protein digestibility in older adults

This review explores the factors that improve meat protein digestibility and applies the findings to the development of home meal replacements with improved protein digestion rates in older adults. Various methods improve the digestion rate of proteins, such as heat, ultrasound, high pressure, or pulse electric field. In addition, probiotics aid in protein digestion by improving the function of digestive organs and secreting enzymes. Plant-derived proteases, such as papain, bromelain, ficin, actinidin, or zingibain, can also improve the protein digestion rate; however, the digestion rate is dependent on the plant enzyme used and protein characteristics. Sous vide processing improves the rate and extent of protein digestibility, but the protein digestion rate decreases with increasing temperature and heating time. Ultrasound, high pressure, or pulsed electric field treatments degrade the protein structure and increase the proteolytic enzyme contact area to improve the protein digestion rate.

Potential implications of oxidative modification on dietary protein nutritional value: A review

During food processing and storage, proteins are sensitive to oxidative modification, changing the structural characteristics and functional properties. Recently, the impact of dietary protein oxidation on body health has drawn increasing attention. However, few reviews summarized and highlighted the impact of oxidative modification on the nutritional value of dietary proteins and related mechanisms. Therefore, this review seeks to give an updated discussion of the effects of oxidative modification on the structural characteristics and nutritional value of dietary proteins, and elucidate the interaction with gut microbiota, intestinal tissues, and organs. Additionally, the specific mechanisms related to pathological conditions are also characterized. Dietary protein oxidation during food processing and storage change protein structure, which further influences the in vitro digestion properties of proteins. In vivo research demonstrates that oxidized dietary proteins threaten body health via complicated pathways and affect the intestinal microenvironment via gut microbiota, metabolites, and intestinal morphology. This review highlights the influence of oxidative modification on the nutritional value of dietary proteins based on organs and the intestinal tract, and illustrates the necessity of appropriate experimental design for comprehensively exploring the health consequences of oxidized dietary proteins.

Available for millions of years but discovered through the last decade: Insects as a source of nutrients and energy in animal diets

The aim of this review is to present and discuss the most recent literature about the processing of insect biomass and its impact on nutritive value, further implementation of meals and fats derived from invertebrates to livestock (poultry and swine), aquaculture (salmonids), and companion animal diets and their impact on growth performance, metabolic response, and gastrointestinal microbiota shifts. Additionally, the most important barriers to obtaining unified products in terms of their nutritive value are considered, i.e., to define insects' nutrient requirements, including various technological groups and further biomass processing (slaughtering, drying, and storage). Due to the current limitation in the insect production process consisting of the lack of infrastructure, there is stress on the relatively small amount of insect products added to the animal diets as a functional feed additive. Currently, only in the case of pet nutrition may insects be considered a full replacement for commonly used environmentally harmful and allergenic products. Simultaneously, the least information has been published on this topic. Thus, more scientific data are needed, particularly when the pet food branch and insect-based diets are rapidly growing.

Raw Eggs To Support Postexercise Recovery in Healthy Young Men: Did Rocky Get It Right or Wrong?

BACKGROUND

Egg protein is ingested during recovery from exercise to facilitate the postexercise increase in muscle protein synthesis rates and, as such, to support the skeletal muscle adaptive response to exercise training. The impact of cooking egg protein on postexercise muscle protein synthesis is unknown.

OBJECTIVES

We sought to compare the impact of ingesting unboiled (raw) compared with boiled eggs during postexercise recovery on postprandial myofibrillar protein synthesis rates.

METHODS

In a parallel design, 45 healthy, resistance-trained young men (age: 24 y; 95% CI: 23, 25 y) were randomly assigned to ingest 5 raw eggs (∼30 g protein), 5 boiled eggs (∼30 g protein), or a control breakfast (∼5 g protein) during recovery from a single session of whole-body resistance-type exercise. Primed continuous l-[ring-13C6]-phenylalanine infusions were applied, with frequent blood sampling. Muscle biopsies were collected immediately after cessation of resistance exercise and at 2 and 5 h into the postexercise recovery period. Primary (myofibrillar protein synthesis rates) and secondary (plasma amino acid concentrations) outcomes were analyzed using repeated-measures (time × group) ANOVA.

RESULTS

Ingestion of eggs significantly increased plasma essential amino acid (EAA) concentrations, with 20% higher peak concentrations following ingestion of boiled compared with raw eggs (time × group: P < 0.001). Myofibrillar protein synthesis rates were significantly increased during the postexercise period when compared with basal, postabsorptive values in all groups (2-4-fold increase: P < 0.001). Postprandial myofibrillar protein synthesis rates were 20% higher after ingesting raw eggs [0.067%/h; 95% CI: 0.056, 0.077%/h; effect size (Cohen d): 0.63], and 18% higher after ingesting boiled eggs (0.065%/h; 95% CI: 0.058, 0.073%/h; effect size: 0.69) when compared with the control breakfast (0.056%/h; 95% CI: 0.048, 0.063%/h), with no significant differences between groups (time × group: P = 0.077).

CONCLUSIONS

The ingestion of raw, as opposed to boiled, eggs attenuates the postprandial rise in circulating EAA concentrations. However, postexercise muscle protein synthesis rates do not differ after ingestion of 5 raw compared with 5 boiled eggs in healthy young men. This trial was registered at the Nederlands Trial Register as NL6506 (www.trialregister.nl).

Physicochemical, functional, and digestive characteristics of tea seed cake protein obtained by ultrafiltration

To make full use of tea seed cake protein (TSCP), this study investigated the physicochemical and functional properties of TSCP, including the TSCP extract and three ultrafiltration fractions TSCP-1 (Mw > 10 kDa), TSCP-2 (3.5 kDa < Mw < 10 kDa), and TSCP-3 (Mw < 3.5 kDa). After ultrafiltration, the content, thermal stability, and surface hydrophobicity of TSCP were increased, and the molecular weight distribution and structure of TSCP showed significant differences. In terms of functionality, each fraction showed its advantages. Specifically, compared with the others, TSCP had better solubility and foaming properties, and TSCP-1 had significantly higher oil absorption capacity, and TSCP-2 had better water absorption capacity and emulsifying properties, and TSCP-3 can flow more easily (p < 0.05). In terms of nutritional value, the content of essential amino acids in all samples was sufficient. The degree of hydrolysis of TSCP was highest (80.98 ± 1.50%), and ultrafiltration decreased digestibility. These results indicated that ultrafiltration effectively improved the structure and functional properties of TSCP, and the obtained fractions can be applied to different scenarios. Practical Application: Tea seed cakes are rich in protein and usually regarded as byproducts during oil processing. Because of its good functional properties, tea seed cake proteins obtained by ultrafiltration have the potential to be used as ingredients for food.

Cooking affects pork proteins in vitro rate of digestion due to different structural and chemical modifications

The effect of thermal processing on the in vitro digestibility of pork proteins was studied. Raw samples were considered the control group, while the thermal treatments included 58, 80, 98 and 160 °C for 72 min, 118 °C for 8 min and 58 °C for 17 h, resembling a range of different cooking procedures. Samples were subsequently subjected to pepsin digestion at pH 3.00 in the gastric phase followed by trypsin and α-chymotrypsin at pH 8.00 in the intestinal phase. Pork cooked at 58 °C for 72 min had a significantly higher pepsin digestibility rate than meat cooked at 80 °C or 160 °C. The trend was similar in the intestinal phase, with samples cooked at 58 °C for 72 min having enhanced digestion rate over other treatments after 120 min of digestion. A PLS model pointed out to an inverse relationship between in vitro proteolysis rate and variables like Maillard reaction compounds or protein structural changes.