Understanding protein digestion in infants and the elderly: Current in vitro digestion models.

The last decades have witnessed a surge of interest in the fate of dietary proteins during gastrointestinal (GI) digestion. Although several in vitro digestion models are available as alternatives to clinical experiments, most of them focus on the digestive conditions of healthy young adults. This study investigates the static/dynamic models used to simulate digestion in infants and the elderly and considers the related in vivo conditions. The in vitro digestive protocols targeting these two groups are summarized, and the challenges associated with the further development of in vitro digestion models are discussed. Static models rely on several factors (e.g., enzyme concentration, pH, reaction time, and rotation speed) to differentiate digestive conditions depending on age. Dynamic models can more accurately simulate the complex digestion process and allow the inclusion of further parameters (sequential secretion of digestive fluids, gradual changes in pH, peristaltic mixing, GI emptying, and the inoculation of luminal microbiota). In the case of infants, age or growth stage clarification and the differentiation of digestive protocols between full-term and preterm infants are required, whereas protocols dealing with various health statuses are required in the case of the elderly, as this group is prone to oral cavity and GI function deterioration.

Synergistic bactericidal effect of clove oil and encapsulated atmospheric pressure plasma against Escherichia coli O157:H7 and Staphylococcus aureus and its mechanism of action.

We investigated the bactericidal effect of clove oil and encapsulated atmospheric pressure plasma (EAP), individually or in combination, against Escherichia coli O157:H7 and Staphylococcus aureus. The bactericidal effect of the combined treatment was also investigated in inoculated beef jerky. For both pathogens, clove oil and EAP single treatments resulted in less than 3.0-log reductions, whereas the combined treatment resulted in more than 7.5-log reductions. The disc-diffusion assay and gas chromatography-mass spectrometry showed no changes in both the clear zone diameter and chemical composition of clove oil before and after the EAP treatment. Significant changes in cell membrane permeability and cell morphology resulting from the combined treatment of clove oil and EAP were evidenced by increased in UV absorption of cell supernatants, increased cell staining with propidium iodide, and changes in cell structure revealed by transmission electron microscopy. The synergistic bactericidal effects of clove oil and EAP against both pathogens were also observed in inoculated beef jerky, but the treatments were less effective against S. aureus, presumably due to thicker peptidoglycan layer. Experiments also demonstrated that the synergistic bactericidal effects between clove oil and EAP are due to clove oil increasing the susceptibility of the bacteria to subsequent EAP treatment, and does not involve alteration of the antibacterial activity of clove oil by EAP.

Quality of reduced-fat meat emulsion: effect of pre-emulsified duck skin and hydrocolloids.

This study explored the impact of reduced-fat meat emulsion with pre-emulsified duck skin and hydrocolloids on physicochemical properties such as cooking loss, emulsion stability, apparent viscosity, protein solubility, and texture profile analysis. Six different reduced-fat meat emulsions were produced: control (pork back fat), T1 (duck skin, DS), T2 (pre-emulsified with duck skin, PDS), T3 (PDS + 2% carrageenan), T4 (PDS + 2% alginate), T5 (PDS + 2% pectin), and T6 (PDS + 2% guar gum). Moisture content, protein content, yellowness, and apparent viscosity of reduced-fat emulsion with PDS and hydrocolloids were all higher (P < 0.05) than control. Cooking loss and emulsion stability of T4 and T6 were lower (P < 0.05) than the control values. Cooking loss and total fluid separation were greatest (P < 0.05) for T5. Fat content of reduced-fat emulsion with PDS was lower (P < 0.05) than that of the control. Meat emulsion comprising PDS with alginate resulted in superior physicochemical properties compared to the other reduced-fat meat emulsion.

Status of meat alternatives and their potential role in the future meat market - A review.

Plant-based meat analogues, edible insects, and cultured meat are promising major meat alternatives that can be used as protein sources in the future. It is also believed that the importance of meat alternatives will continue to increase because of concerns on limited sustainability of the traditional meat production system. The meat alternatives are expected to have different roles based on their different benefits and limitations. Plant-based meat analogues and edible insects can replace traditional meat as a good protein source from the perspective of nutritional value. Furthermore, plant-based meat can be made available to a wide range of consumers (e.g., as vegetarian or halal food products). However, despite ongoing technical developments, their palatability, including appearance, flavor, and texture, is still different from the consumers' standard established from livestock-based traditional meat. Meanwhile, cultured meat is the only method to produce actual animal muscle-based meat; therefore, the final product is more meat-like compared to other meat analogues. However, technical difficulties, especially in mass production and cost, remain before it can be commercialized. Nevertheless, these meat alternatives can be a part of our future protein sources while maintaining a complementary relationship with traditional meat.

Comparison of reducing sugar content, sensory traits, and fatty acids and volatile compound profiles of the longissimus thoracis among Korean cattle, Holsteins, and Angus steers.

OBJECTIVE: This study was performed to compare fat content, reducing sugar contents, sensory traits, and fatty acid (FA) and volatile compound profiles in longissimus thoracis (LT) among Korean cattle (KC), Holstein (HO), and Angus (AN) steers. METHODS: Twelve LT samples (about 500 g each) of KC with an average age of 31±0.42 months, an average carcass weight of 431±12.5 kg, and a quality grade (QG) of 1+ were obtained from the joint livestock products market. Twelve LT samples of HO cattle with an average age of 24±0.54 months, an average carcass weight of 402±7.81 kg, and a QG of 2 were also obtained from the same market. Twelve LT samples of AN steers with an average age of about 20 months and a QG of choice were purchased from a beef delivery company. After slaughter, samples were kept at 4°C for 42 days and prepared for immediate analysis or stored at appropriate conditions. The chemical composition, color, pH, shear force, collagen content, reducing sugars, sensory evaluation, FA composition, and volatile compound content for each LT sample were analyzed. RESULTS: The LT of KC had the highest (p<0.05) fat content, the highest reducing sugar content, and the highest scores in the sensory evaluation (flavor, tenderness, juiciness, and overall acceptance). All the sensory traits were positively correlated (p<0.001) with intramuscular fat and reducing sugar content. Several FAs and volatile compound profiles varied among the breeds. KC LT had the highest (p<0.05) concentrations of acetaldehyde, 3-methyl butanal, and 3-hydroxy-2-butanone, and these volatile compounds were positively correlated (p<0.05) with all the sensory traits. CONCLUSION: Variations in fat content and reducing sugar contents and FA and volatile compound profiles may contribute to differences in the sensory quality of LT among breeds.

Enhancement of antioxidant effects of naringin after atmospheric pressure dielectric barrier discharge plasma treatment.

Naringin is the natural chief bitter flavonoid found in Citrus species. Herein, bitter naringin was treated with atmospheric pressure plasma to afford two new converted flavonoids, narinplasmins A (2) and B (3), along with the known compound, 2R-naringin. The structures of the two new naringin derivatives were elucidated on the basis of spectroscopic methods. The antioxidant activity of all isolates was evaluated based on 1,1-diphenyl-2-picrylhydrazyl and peroxynitrite (ONOO(-)) scavenging assays. The new flavanone glycoside 2 containing a methoxyalkyl group exhibited significantly improved antioxidant properties in these assays relative to the parent naringin.

Flexible thin-layer dielectric barrier discharge plasma treatment of pork butt and beef loin: effects on pathogen inactivation and meat-quality attributes.

The effects of a flexible thin-layer dielectric barrier discharge (DBD) plasma system using a sealed package on microbial inactivation and quality attributes of fresh pork and beef were tested. Following a 10-min treatment, the microbial-load reductions of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium were 2.04, 2.54, and 2.68 Log CFU/g in pork-butt samples and 1.90, 2.57, and 2.58 Log CFU/g in beef-loin samples, respectively. Colorimetric analysis showed that DBD-plasma treatment did not significantly affect L* values (lightness) of pork and beef samples, but lowered a* values (redness) significantly after 5- and 7.5-min exposures. The plasma treatment significantly influenced lipid oxidation only after a 10-min exposure. The texture of both types of meat was unaffected by plasma treatment. All sensory parameters of treated and non-treated samples were comparable except for taste, which was negatively influenced by the plasma treatment (P < 0.05). This thin-layer DBD-plasma system can be applied to inactivate foodborne pathogens. The observed minor deterioration of meat quality might be prevented by the use of hurdle technology.

Evaluation of pathogen inactivation on sliced cheese induced by encapsulated atmospheric pressure dielectric barrier discharge plasma.

Pathogen inactivation induced by atmospheric pressure dielectric barrier discharge (DBD) (250 W, 15 kHz, air discharge) produced in a rectangular plastic container and the effect of post-treatment storage time on inactivation were evaluated using agar plates and cheese slices. When agar plates were treated with plasma, populations of Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes showed 3.57, 6.69, and 6.53 decimal reductions at 60 s, 45 s, and 7 min, respectively. When the pathogens tested were inoculated on cheese slices, 2.67, 3.10, and 1.65 decimal reductions were achieved at the same respective treatment times. The post-treatment storage duration following plasma treatment potently affected further reduction in pathogen populations. Therefore, the newly developed encapsulated DBD-plasma system for use in a container can be applied to improve the safety of sliced cheese, and increasing post-treatment storage time can greatly enhance the system's pathogen-inactivation efficiency.

Taste-active compound levels in Korean native chicken meat: The effects of bird age and the cooking process.

The effects of bird age and the cooking process on the levels of several taste-active compounds, including inosine 5'-monophosphate (IMP), glutamic acid, cysteine, reducing sugars, as well as oleic, linoleic, arachidonic, and docosahexaenoic acids (DHA), in the breast and leg meats from a certified meat-type commercial Korean native chicken (KNC) strain (Woorimatdag) were investigated. KNC cocks were raised under similar standard conditions at a commercial chicken farm, and breast and leg meats from birds of various ages (10, 11, 12, 13, and 14 wk; 10 birds/age group) were obtained. After raw and cooked meat samples were prepared, they were analyzed for the aforementioned taste-active compounds. Compared to the leg meat, KNC breast meat had higher levels of IMP, arachidonic acid, and DHA, but lower levels of the other taste-active compounds (P < 0.05). KNC meat lost significant amounts of all the taste-active compounds, excluding oleic and linoleic acids, during the cooking process (P < 0.05). However, bird age only had a minor effect on the levels of these taste-active compounds. The results of this study provide useful information regarding the levels of taste-active compounds in KNC meat from birds of different ages, and their fate during the cooking process. This information could be useful for selection and breeding programs, and for popularizing native chicken meat.

Proximate Composition, and l-Carnitine and Betaine Contents in Meat from Korean Indigenous Chicken.

This study investigated the proximate composition and l-carnitine and betaine content of meats from 5 lines of Korean indigenous chicken (KIC) for developing highly nutritious meat breeds with health benefits from the bioactive compounds such as l-carnitine and betaine in meat. In addition, the relevance of gender (male and female) and meat type (breast and thigh meat) was examined. A total of 595 F1 progeny (black [B], grey-brown [G], red-brown [R], white [W], and yellow-brown [Y]) from 70 full-sib families were used. The moisture, protein, fat, and ash contents of the meats were significantly affected by line, gender, and meat type (p<0.05). The males in line G and females in line B showed the highest protein and the lowest fat content of the meats. l-carnitine and betaine content showed effects of meat type, line, and gender (p<0.05). The highest l-carnitine content was found in breast and thigh meats from line Y in both genders. The breast meat from line G and the thigh meat from line R had the highest betaine content in males. The female breast and thigh meats showed the highest betaine content in line R. These data could be valuable for establishing selection strategies for developing highly nutritious chicken meat breeds in Korea.

Effect of atmospheric pressure plasma jet on the foodborne pathogens attached to commercial food containers.

Bacterial biofilms are associated with numerous infections and problems in the health care and food industries. The aim of this study was to evaluate the bactericidal effect of an atmospheric pressure plasma (APP) jet on Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium biofilm formation on collagen casing (CC), polypropylene (PP) and polyethylene terephthalate (PET), which are widely used food container materials. The samples were treated separately with the APP jet at a 50-W input power for 5 and 10 min, and nitrogen (6 l per minute) gas combined with oxygen (10 standard cubic centimeters per minute) was used to produce the APP. The APP jet reduced the number of bacterial cells in a time-dependent manner. All pathogens attached to CC, PP, and PET were reduced by 3-4 log CFU/cm(2) by the 10-min APP treatment. The developed APP jet was effectively reduced biofilms on CC, PP, and PET.

Evaluation of the treatment of both sides of raw chicken breasts with an atmospheric pressure plasma jet for the inactivation of Escherichia coli.

Atmospheric pressure plasma (APP) is an emerging nonthermal microbial inactivation technique. In this study, agar and raw chicken breast were inoculated with Escherichia coli and treated with an APP jet based on cold arc plasma. The aim of this study was to investigate the optimum conditions for the plasma treatment of an APP jet in order to maximize the efficiency of E. coli inactivation. The combination of N2+O2 (10 standard cubic centimeters per minute) and a longer treatment time (10 min) resulted in the highest inactivation of E. coli on agar plates with an optimum treatment distance of 20 mm. The samples in dry and wet conditions showed similar reductions in E. coli count when one side of the samples was treated at a given treatment time. Treating both sides-2.5 min on each side-resulted in a higher growth inhibition of E. coli than treatment of a single side only for 5 min. However, there was no significant difference between one-side treated samples (10 min) and both-sides treated samples (5+5 min). When the concentration of E. coli in the chicken breast sample was 10(4) colony-forming units (CFU)/g, the reduction rate of the E. coli was the highest, followed by 10(5), 10(6), and 10(7) CFU/g; however, no difference was found between 10(3) and 10(4) CFU/g. In conclusion, various treatment conditions may affect the inactivation efficiency of E. coli. In the present study, the optimum condition was determined as the treatment distance of 20 mm and longer treatment time (10 min) with the addition of oxygen to the nitrogen gas flow. Furthermore, the cell concentration of sample was an important parameter for the efficacy of the inactivation process.

Synergistic Effects of Electron-beam Irradiation and Leek Extract on the Quality of Pork Jerky during Ambient Storage.

To investigate the synergistic effect(s) of electron-beam (EB) irradiation and leek (Allium tuberosum Rottler) extract on the quality of pork jerky during ambient storage, we irradiated prepared pork jerky samples (control and samples with 0.5% and 1.0% leek extract) with EB technology at doses of 0, 1, 2, and 4 kGy, stored them for 2 months at 25°C, and analyzed them. Water activity was 0.73 to 0.77 in non-irradiated samples, and no significant difference in the water activity was observed between the samples treated with leek and the control. The total aerobic bacterial count was significantly decreased with an increase in the irradiation dose and leek extract addition when compared to that of the control (4.54±0.05 log CFU/g). Further, the Hunter color values (L*, a*, and b*) were found to be significantly decreased following leek extract addition and EB irradiation. However, the color values, especially the a* value of the irradiated samples significantly increased during storage. Notably, increasing the EB irradiation dose enhanced the peroxide value. Sensory evaluation revealed that irradiation decreased flavor and overall acceptability. Our findings suggest the use of EB irradiation in combination with leek extract to improve the microbiological safety of pork jerky. However, in order to meet market requirements, novel methods to enhance the sensory quality of pork jerky are warranted.

Comparison of quality traits of meat from korean native chickens and broilers used in two different traditional korean cuisines.

With the aim of investigating the differences in the quality traits between Korean native chicken (Hanhyup, KNC) and broilers commonly used in two different traditional Korean cuisines, the chemical composition and sensory properties of breast and thigh meat from the two chicken strains were assessed. KNC for baeksuk (chicken meat braised in soup with various Oriental medicinal plants; KNL), KNC for samgyetang (similar to baeksuk but young chickens and ginseng are used; KNS), broiler for baeksuk (BL), and broiler for samgyetang (BS) were used as treatments in this study. KNL and KNS contained higher protein but lower fat content than BL and BS. The L* values of breast and thigh meat, but not the a* values, were significantly different between KNS and BS, whereas significant differences in both values were observed between KNL and BL. Compared to the other three types of chickens, KNS contained the highest total and insoluble collagen content, and KNL and BL showed higher inosine-5'-monophosphate content in their meat. Overall, KNL and KNS contributed darker, less tender meat with higher protein and less fat content together with more n-3 fatty acids, as opposed to their counterparts used for the same cuisines. Based on the results of the sensory analysis, even though there are some differences in physiochemical traits, different chicken sources do not differ in overall sensory quality. This information can help consumers to understand better the meat available for their preferred traditional cuisines.

Characteristics of pork emulsion gel manufactured with hot-boned pork and winter mushroom powder without phosphate.

This study investigated the physicochemical characteristics of pork emulsion gels manufactured from hot-boned (HB) pork and winter mushroom powder in the absence of phosphate. It was found that compared to cold-boned (CB) pork, HB pork had a higher pH and exhibited a higher myofibrillar protein solubility with a lower actomyosin content (P < 0.05). Four types of pork gels were prepared, namely CB pork without phosphate, CB pork with phosphate (CBP), HB pork without phosphate, and HB pork with winter mushroom powder but without phosphate (HBW). The total exuded fluid was comparable for the CBP and HBW gels on all storage days. In addition, the HB and HBW gels had similar springiness and cohesiveness properties to the CBP gel (P > 0.05). These results indicate that the quality of pork gels manufactured in the absence of phosphate can be improved by the use of HB pork and with the incorporation of winter mushroom powder.

Improvement of structural, physicochemical, and rheological properties of porcine myofibrillar proteins by high-intensity ultrasound treatment for application as Pickering stabilizers.

This study aimed to evaluate the potential of time-dependent (0, 15, 30, 60, 120 min) treatment of porcine-derived myofibrillar proteins (MPs) with high-intensity ultrasound (HIU) for utilizing them as a Pickering stabilizer and decipher the underlying mechanism by which HIU treatment increases the emulsification and dispersion stability of MPs. To accomplish this, we analyzed the structural, physicochemical, and rheological properties of the HIU-treated MPs. Myosin heavy chain and actin were observed to be denatured, and the particle size of MPs decreased from 3,342.7 nm for the control group to 153.9 nm for 120 min HIU-treated MPs. Fourier-transformed infrared spectroscopy and circular dichroism spectroscopy confirmed that as the HIU treatment time increased, α-helical content increased, and ß-sheet decreased, indicating that the protein secondary/tertiary structure was modified. In addition, the turbidity, apparent viscosity, and viscoelastic properties of the HIU-treated MP solution were decreased compared to the control, while the surface hydrophobicity was significantly increased. Analyses of the emulsification properties of the Pickering emulsions prepared using time-dependent HIU-treated MPs revealed that the emulsion activity index and emulsion stability index of HIU-treated MP were improved. Confocal laser scanning microscopy images indicated that small spherical droplets adsorbed with MPs were formed by HIU treatment and that dispersion stabilities were improved because the Turbiscan stability index of the HIU-treated group was lower than that of the control group. These findings could be used as supporting data for the utilizing porcine-derived MPs, which have been treated with HIU for appropriate time periods, as Pickering stabilizers.

Higher Protein Digestibility of Chicken Thigh than Breast Muscle in an In Vitro Elderly Digestion Model.

This study investigated the protein digestibility of chicken breast and thigh in an in vitro digestion model to determine the better protein sources for the elderly in terms of bioavailability. For this purpose, the biochemical traits of raw muscles and the structural properties of myofibrillar proteins were monitored. The thigh had higher pH, 10% trichloroacetic acid-soluble α-amino groups, and protein carbonyl content than the breast (p<0.05). In the proximate composition, the thigh had higher crude fat and lower crude protein content than the breast (p<0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrillar proteins showed noticeable differences in the band intensities of tropomyosin α-chain and myosin light chain-3 between the thigh and breast. The intrinsic tryptophan fluorescence intensity of myosin was lower in the thigh than in the breast (p<0.05). Moreover, circular dichroism spectroscopy of myosin revealed that the thigh had higher α-helical and lower ß-sheet structures than the breast (p<0.05). The cooked muscles were then chopped and digested in the elderly digestion model. The thigh had more α-amino groups than the breast after both gastric and gastrointestinal digestion (p<0.05). SDS-PAGE analysis of the gastric digesta showed that more bands remained in the digesta of the breast than that of the thigh. The content of proteins less than 3 kDa in the gastrointestinal digesta was also higher in the thigh than in the breast (p<0.05). These results reveal that chicken thigh with higher in vitro protein digestibility is a more appropriate protein source for the elderly than chicken breast.

Differences in pork myosin solubility and structure with various chloride salts and their property of pork gel.

The solubility and structure of myosin and the properties of pork gel with NaCl, KCl, CaCl2, and MgCl2 were investigated. Myofibrillar proteins (MPs) with phosphate were more solubilized with NaCl than with KCl (p < 0.05). CaCl2 and MgCl2 showed lower MP solubilities than those of NaCl and KCl (p < 0.05). The α-helix content of myosin was lower in KCl, CaCl2, and MgCl2 than in NaCl (p < 0.05). The pH of pork batter decreased in the order of KCl, NaCl, MgCl2, and CaCl2 (p < 0.05). The cooking yield of the pork gel manufactured with monovalent salts was higher than that of the pork gel manufactured with divalent salts (p < 0.05). The pork gel manufactured with KCl and MgCl2 showed lower hardness than that of the pork gel manufactured with NaCl. The solubility and structure of myosin were different with the different chloride salts and those led the different quality properties of pork gel. Therefore, the results of this study can be helpful for understanding the quality properties of low-slat meat products manufactured by replacing sodium chloride with different chloride salts.

Peptides inhibiting angiotensin-I-converting enzyme: Isolation from flavourzyme hydrolysate of Protaetia brevitarsis larva protein and identification.

Many angiotensin-I-converting enzyme (ACE) inhibitory peptides are used to prevent and manage hypertension. In this study, ACE inhibitory peptides were isolated from an insect protein that is attracting attention for it potential antihypertensive activity. Protaetia brevitarsis larva protein was enzymatically hydrolyzed by Flavourzyme®, and the hydrolysate was shown to inhibit ACE. Subsequent fractionation, using ultrafiltration and gel permeation chromatography followed by liquid chromatography-tandem mass spectrometry analysis, identified four previously unknown peptides with significant ACE inhibition characteristics (Ser-Tyr, Pro-Phe, Tyr-Pro-Tyr, and Trp-Ile). The highest inhibition activity observed for Trp-Ile. These peptides stimulated production of NO in human umbilical vein endothelial cells and, based on molecular docking analysis, exerted their inhibitory effects via hydrogen bonding with the ACE receptor active site. Thus, the identified peptides can be considered as promising candidates for ACE inhibition and have potential to be used as functional food ingredients.

Effects of combined treatments of electron-beam irradiation and addition of leek (Allium tuberosum) extract on reduction of pathogens in pork jerky.

This study investigated the combined effect of electron-beam irradiation and addition of leek (Allium tuberosum R.) extract on pork jerky inoculated with selected foodborne pathogens. Prepared pork jerky samples (control and samples with 1.0% leek extract) were inoculated with pathogens and subsequently irradiated at 0, 0.5, 1, 2, 3, and 4 kGy doses. In comparison with the control, samples with 1.0% leek extract showed significant reduction in the numbers of Escherichia coli, Listeria monocytogenes, and Salmonella Typhimurium. No viable counts were detected for Salmonella Typhimurium in both control and leek-extract samples, and for E. coli and L. monocytogenes in the leek-extract sample exposed to 3 kGy irradiation dose. The D(10) values for E. coli, L. monocytogenes, and Salmonella Typhimurium observed in the irradiated samples with leek extract were 0.39, 0.34, and 0.32 kGy, while the D(10) values in those without leek extract were 0.65, 0.65, and 0.39 kGy, respectively. Therefore, our results clearly showed that irradiation combined with leek extract was effective in reducing pathogens, suggesting that a low dose of irradiation combined with the addition of a natural antimicrobial agent can enhance the microbial safety and shelf-life of pork jerky.