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Protein gelation is an important phenomenon in processed meats. The present study investigated the structure-activity relationship of six phenolic compounds, that is, gallic acid (GA), chlorogenic acid (CA), propyl gallate (PG), quercetin (QT), catechin (CC), and (-)-epigallocatechin-3-gallate (EGCG) in a myofibrillar protein (MP) gelling system under controlled oxidative conditions. All phenolics induced unfolding and promoted cross-linking of MP via sulfhydryl or amine groups. At an equal molar concentration, EGCG boosted the elastic MP gel network more than other phenolics except PG. However, all three monophenols (GA, CA, and PG) and the diphenol QT increased the MP gel strength more than CC (diphenol) and EGCG (triphenol). The flavanol structure appeared to interfere with the protein gel structure development. All phenolics retarded lipid oxidation in MP-emulsion composite gels during refrigerated storage with the least polar phenolic compounds, PG and QT, showing the greatest efficacy.

The impact of preheating and phenolic treatment on the adsorption behavior at the air–water interface and subsequent foaming properties of whey proteins isolate (WPI) was investigated. Native WPI (NWPI) and heat-unfolded (80 °C for 9 min) WPI (HWPI) were interacted with gallic acid (GA) or epigallocatechin gallate (EGCG) at pH 7.0. Phenolic treatment slightly increased the unordered secondary structure and significantly decreased the surface hydrophobicity of proteins whereas the effect of EGCG was more remarkable. The protein–phenolic binding was further confirmed by isothermal titration calorimetry. NWPI and HWPI (10 mg/mL) were able to adsorb at the air–water interface to form an elastic film and the adsorption process was dominated by protein unfolding and rearrangement at the interface. Preheating significantly improved the dynamic surface pressure (π) and depressed the dilatational elasticity (Ed) of whey proteins adsorbed at the air–water interface. The heat-induced protein aggregation led to an enhanced foam stability. GA and EGCG induced different patterns of time-dependent π evolution, which were closely related to the phenolic concentration. Both phenolics suppressed the Ed of protein film via weakening protein interactions at the interface. However, foaming properties were significantly enhanced at all phenolic concentrations except for the 240 μmol/g EGCG-treated HWPI, which was corroborated by the foam image.

The dose-dependent effects of (-)-epigallocatechin-3-gallate (EGCG; at 0, 50, 100, 200, 500, and 1000 mg/L) on the physical, chemical, and oxidative stability of porcine myofibrillar protein (MP)-soybean oil emulsion systems were investigated. The results showed EGCG at all levels effectively suppressed lipid oxidation in MP emulsion composite gels during the entire chill storage (at 4 °C for 0, 3, or 7 days). The incorporation of EGCG at higher concentrations (>100 mg/L) promoted the loss of sulfhydryls, reduction of surface hydrophobicity, and aggregation and cross-linking of MP. As a result, high concentrations of EGCG (500 and 1000 mg/L) hampered emulsification and gel formation of MP. However, EGCG at lower concentrations (50-200 mg/L) improved the oxidative stability of meat emulsions without jeopardizing the textural stability.

In this study, the structural, interfacial, and emulsifying properties of high-intensity ultrasound (HUS)-treated pea protein isolate (PPIUS) were investigated. HUS at 50% amplitude and 57–60 W·cm−2 for 5 min markedly improved protein solubility (by 132%), surface hydrophobicity (by 173%), and reduced particle size (by 52%). These physicochemical changes in PPIUS led to more rapid protein adsorption at the oil–water interface, improved emulsifying activity (by 18–27%) and capacity (by 11%), and enhanced emulsion physical stability. The multilayer nature, albeit less elastic, of the interfacial membrane formed by PPIUS when compared to control protein (PPIC), based on dilatational testing, contributed to the above results. Moreover, PPIUS-stabilized emulsions exhibited a tendency of being less susceptible to lipid oxidation during storage. Thus, structure-modifying HUS may be a valuable processing technology for the manufacture of pea protein-based emulsion foods.

α-Galactosidase (α-GAL) dietary supplement is used to alleviate flatulence discomfort caused by raffinose family oligosaccharides (RFOs), but reported efficacy varies among consumers. This study investigated the hypothesis that factors such as stomach acid, gastrointestinal (GI) enzymes (pepsin and pancreatin), and food proteins could affect the activity of α-GAL against RFOs. Strong acidic conditions (pH

The dose-dependent effects of gallic acid (GA; at 0, 6, 30, and 150 μmol/g protein) on chemical changes and gelling properties of oxidatively stressed porcine myofibrillar protein (MP) and in vitro digestibility of the gels were investigated. The incorporation of GA suppressed lipid oxidation and protein carbonyl formation but promoted the loss of thiol and amine groups, destabilization of the tertiary structure, aggregation, and cross-linking. The gelling potential (storage modulus) of MP was increased by nearly 50% with 6 and 30 μmol/g of GA, corresponding to enhanced protein unfolding and aggregation and formation of disulfide-dominant covalent bonds. However, GA at 150 μmol/g induced macroscopic aggregations and insolubility of MP, resulting in poorly structured gels. Despite the oxidative changes, MP gels did not show reduced susceptibility to digestive enzymes in vitro.

UNLABELLED In muscle food processing, where oxidation is inevitable, phosphates are usually added to improve water binding. This present study attempted to investigate the interactive roles of protein oxidation and pyrophosphate (PP) during thermal gelation of myosin. Myosin isolated from pork muscle was solubilized in 0.5 M NaCl at pH 6.2 then oxidatively stressed with an iron-redox cycling system that produces hydroxyl radicals with or without 1 mM PP and 2 mM MgCl2 at 4 °C for 12 or 24 h then heated to 50 °C at 1.3 °C/min. Protein conformational stability was measured by differential scanning calorimetry, and covalent cross-linking was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis following chymotrypsin digestion. The binding of PP to myosin suppressed disulfide bond formation in myosin subfragments 1 and 2 and partially inhibited oxidation-initiated cross-linking of heavy meromyosin during myosin gelation with a lesser effect on light meromyosin. In the presence of PP, myosin exhibited less loss of conformational integrity upon oxidation than myosin without PP. Rheological analysis from 20 to 75 °C indicated up to 32% decreases (P < 0.05) in elastic modulus (G') of myosin gels due to oxidation. However, the presence of 1 mM PP, which also lowered the gelling capacity of myosin, inhibited the oxidation-induced G' by nearly half (P < 0.05). These results suggest that the protection of myosin head from oxidative modification by PP can be a significant factor for the minimization of gelling property losses during cooking of comminuted meats. PRACTICAL APPLICATION The association of myosin S1 subfragment possibly S2 as well with pyrophosphate prevents extensive myosin head–head cross-linking. This alleviates the negative impact of oxidation on the gel formation of myosin, an expected main form of myofibrillar protein due to pyrophosphate-induced actomyosin dissociation. Likewise, oxidative S1–S1 association inhibits the binding of pyrophosphate thereby reducing its gel-weakening effect. The mutual constraining roles of oxidation and pyrophosphate can be a significant factor for the minimization of gelling property losses during the manufacture of comminuted meat products.

Recent nutrigenomic studies have shown that animal nutrition can have a major influence on tissue gene expression. Dietary antioxidant supplements can enhance the quality of meat through modification of tissue metabolic processes. This study investigated the influence of dietary antioxidants and quality of oil on the oxidative and enzymatic properties of chicken broiler breast meat stored in an oxygen-enriched package (HiOx: 80% O2/20% CO2) in comparison with air-permeable polyvinylchloride (PVC) or skin packaging systems during retail display at 2 to 4°C for up to 21 d. Broilers were fed either a diet with a low-oxidized (peroxide value 23 mEq of O2/kg) or high-oxidized (peroxide value 121 mEq of O2/kg) oil, supplemented with or without an algae-based Se yeast and organic mineral antioxidant pack for 42 d. Lipid and protein oxidation and tissue enzymatic activity were analyzed. In all packaging systems, lipid oxidation (TBA reactive substances) was inhibited by up to 32.5% (P < 0.05) with an antioxidant-supplemented diet when compared with diets without antioxidants, particularly in the HiOx and PVC systems. Protein sulfhydryls were significantly protected by antioxidant diets (e.g., by 14.6 and 17.8% for low-and high-oxidized dietary groups, respectively, in PVC d 7 samples). Glutathione peroxidase, catalase, and superoxide dismutase activities were significantly higher (P < 0.05) in antioxidant-supplemented diets compared with the basal diet, regardless of oil quality. Also, serum carbonyls were lower in broilers fed a low-oxidized antioxidant-supplemented treatment. The results demonstrate that dietary antioxidants can minimize the oxidative instability of proteins and lipids, and the protection may be linked to improved cellular antioxidant enzymatic activity.

This study investigated the efficacy of licorice extract (LE) to curtail lipid oxidation and protect sensory attributes of ground pork during refrigerated and frozen storage. Pork patties (20% fat) were formulated with 0%, 0.02%, 0.05%, and 0.1% (meat basis) LE or rosemary extract (RE) as comparison or 0.01% (fat basis) BHA with 0 or 1.5% NaCl. Raw and precooked (75 °C) patties were packaged in polyvinylchloride overwrapped trays and stored at 2 °C up to 7 and 14 d, respectively, or at –20 °C up to 6 mo. Lipid oxidation (thiobarbituric acid-reactive substances [TBARS]) and sensory attributes of stored patty samples were evaluated, radical scavenging activity of the LE was measured, and the active phenolic compounds were identified. Cooking yield (

The influence of dietary antioxidants and quality of oil on the oxidative and physico-chemical properties of chicken broiler breast and thigh meat stored was studied in either an oxygen-enriched (HiOx: 80% O2/20% CO2) or an air-permeable polyvinylchloride (PVC) packaging system during retail display at 2-4°C for up to 14 and 7 d, respectively. Broilers were fed on a diet with either a low-oxidised (peroxide value (POV) 23 meq O2/kg) or a high-oxidised (POV 121 meq O2/kg) oil, supplemented with or without an algae/selenium-based antioxidant with organic minerals, for 42 d. Lipid and protein oxidation, myofibrillar protein profile and purge loss were analysed. In both packaging systems, lipid oxidation (thiobarbituric acid-reactive substances [TBARS]) was inhibited by up to 65% and 57% in chicken breast and thigh, respectively, with an antioxidant-supplemented diet compared to those without. In both breast and thigh samples, protein sulfhydryls and water-holding capacity (purge loss) were better protected by the antioxidant dietary treatment, regardless of oil quality. Thigh muscles had up to sevenfold greater TBARS formation and more myosin heavy chain losses compared to breast samples. Antioxidant supplementation was more protective against lipid oxidation and water-holding capacity in the group fed on high-oxidised oil compared to those fed on low-oxidised oil. The results suggest that dietary antioxidants can minimise the negative impact of oxidised oil on broiler meat quality, and this protection was more pronounced for thigh than breast muscle, indicating inherent variations between muscle fibre types.

This study investigated the influence of an oxygen-enriched modified atmosphere packaging (HiOx: 80% O2/20% CO2) in comparison with air-permeable polyvinylchloride (PVC) wrapping and partial vacuum (VP: 60%) packaging on the ability of myofibrils to imbibe water during retail display of fresh ground pork at 2 to 4 °C. Both HiOx and PVC muscles after 4 d showed maximum myofibril swelling and A-band dissolution when isolated myofibrils were subjected to a graded series of salt solutions (0.20.4 M NaCl with 10-mM sodium pyrophosphate, pH 6.2), while VP samples exhibited no remarkable change. Protein carbonyl content increased substantially from day 0 to 4 in all muscle samples. For HiOx, muscle hydration capacity increased linearly (P < 0.05) during storage up to 14 d, corresponding to protein carbonyl production. No significant changes in hydration properties were noted in VP muscle samples, which also maintained lower levels of protein oxidation, during storage up to 21 d. These results indicated that packaging in modified atmosphere with high levels of oxygen could result in increased protein oxidation but enhanced hydration capacity of fresh meat. Practical Application: Packaging of fresh meat, including ground pork, under an oxygen-enriched atmosphere condition is widely used in the industry to preserve red color of meat. Results from the present study indicate that high oxygen packaging has a discordant effect on fresh ground pork: it enhances hydration but decreases water-binding, and this seems to be caused by increased swelling of muscle fibers due to mild protein oxidation. Hence, it is advisable to employ a water-binding agent in this type of packaging system so as to retain the moisture in stored fresh pork products while maintaining the color stability.

1. The impact of dietary antioxidants and degree of oil oxidation on textural attributes of chicken broiler breast meat stored in oxygen-enriched, air-permeable polyvinylchloride and skin packaging systems during retail display at 2-4°C for up to 21 d was assessed. 2. Broilers were fed on diets either with a low-oxidised oil (peroxide 23 mEq O2/kg) or with a high-oxidised oil (peroxide 121 mEq O2/kg), with or without an algae-based antioxidant and organic mineral antioxidant supplement for 42 d. 3. Fatty acids and radical scavenging activities of the diets were estimated. Meat colour, pH, myofibrillar protein profile and textural traits were measured. 4. Diets with high-oxidised oil reduced stearic, linoleic and linolenic acid content compared to low-oxidised oil samples, regardless of antioxidant supplementation. Meat colour and pH varied among dietary treatments throughout storage. Meat samples from the antioxidant dietary group, irrespective of oil oxidation level, had lower amounts of purge and cooking losses compared to the unsupplemented diets. For all packaging systems, meat shear force was significantly higher for broilers fed on high-oxidised diets. 5. The results demonstrate that dietary antioxidant supplementation can minimise the negative impact of oxidised oil on the quality of broiler meat packaged in different atmospheric environments.

Ten mature female dogs (19.0 ± 0.4 kg) were used in a replicated 5 × 5 Latin Square experiment to determine the feeding value of maize gluten meal (MGM) in a complete food fed to dogs. All foods contained 100 g poultry meal/kg and graded levels of MGM (4–320 g/kg dry matter) resulting in foods that were 100, 150, 200, 250 and 300 g/kg crude protein (CP). Daily dry matter (DM) intake averaged 307 ± 7 g/d. An increase in MGM resulted in an increase in faecal moisture from 516 to 575 g/kg (linear; P

Eight adult female dogs (18.2±0.4 kg) were used in an experiment to determine the feeding value of soyabean meal (SBM) in a complete food fed to dogs. All foods contained graded concentrations of SBM (151–461 g/kg dry matter (DM)) resulting in foods that were 100, 150, 200 and 250 g/kg crude protein (CP). Daily dry matter intake averaged 296±10 g per day. An increase in SBM resulted in a decrease in fecal moisture from 389 to 265 g/kg (linear; P

Eight mature female dogs (18.0 +/- 0.2 kg) were used in a replicated 4 x 4 Latin square experiment to determine the feeding value of low-ash poultry meal (PM) in a complete food fed to dogs. All foods contained graded concentrations of PM (10.4 to 32.5% DM), resulting in foods that were 10, 15, 20, and 25% CP. Daily DMI averaged 284 +/- 14 g/d. An increase in PM resulted in an increase in fecal moisture from 44.7 to 55.1% (linear; P 0.05). Large intestinal CP digestibility increased from 21.6 to 37.1% (linear; P < 0.05) with increasing PM. Total-tract CP digestibility increased from 81.0 to 86.6% (linear; P < 0.01) as PM increased. Arginine had the highest overall digestibility ranging from 88.5 to 91.3%, whereas cysteine had the lowest digestibility, ranging from 67.1 to 71.4%. These data indicate that PM is a highly digestible protein source for canine foods with inclusions of 10.4 to 32.5% of DM.

This study investigated the efficacy of licorice extract (LE) to curtail lipid oxidation and protect sensory attributes of ground pork during refrigerated and frozen storage. Pork patties (20% fat) were formulated with 0%, 0.02%, 0.05%, and 0.1% (meat basis) LE or rosemary extract (RE) as comparison or 0.01% (fat basis) BHA with 0 or 1.5% NaCl. Raw and precooked (75 °C) patties were packaged in polyvinylchloride overwrapped trays and stored at 2 °C up to 7 and 14 d, respectively, or at -20 °C up to 6 mo. Lipid oxidation (thiobarbituric acid-reactive substances [TBARS]) and sensory attributes of stored patty samples were evaluated, radical scavenging activity of the LE was measured, and the active phenolic compounds were identified. Cooking yield (85%) was similar among antioxidant treatments, and lipid oxidation was minimal in refrigerated or frozen raw samples. However, TBARS values in refrigerated precooked control patties (0.22 mg/kg) rose to 9.3 to 9.4 mg/kg after 14 d, compared to 3.4 to 4.4 and 4.4 to 6.9 mg/kg in patties treated with 0.1% LE and RE, respectively. In frozen precooked samples, TBARS (0.22 mg/kg) increased to 1.3 mg/kg (P0.05) in control patties after 6 mo and had no significant change in patties treated with 0.1% LE or 0.01% butylated hydroxyanisol. Sensory panel evaluation confirmed strong inhibition of rancidity production by LE, corroborating its remarkable antiradical activity due to the presence of multiple phenolics. The results indicate that licorice has great potential as a natural antioxidative additive to extend the shelf-life of precooked pork.