Tryptophan depletion and formation of alpha-aminoadipic and gamma-glutamic semialdehydes in porcine burger patties with added phenolic-rich fruit extracts

Effects of curcumin and sodium bicarbonate on the structure and gel properties of oxidation-induced beef myofibrillar proteins

This study examined the effects of sodium bicarbonate (SC), curcumin (CC), and their combination (CC + SC) on the structural and gel properties of bovine myofibrillar proteins (MPs) under oxidative conditions. The results demonstrated that the addition of CC and SC significantly reduced carbonyl formation associated with protein oxidation (P < 0.05), with the combination of CC + SC showing the strongest inhibitory effect. The incorporation of SC induced a structural transition in MPs from α-helix to β-sheet, which led to an increase in gel strength and the ability to bind water molecules (P < 0.05). In contrast, the addition of CC alone did not significantly affect these properties. Scanning electron microscopy further revealed a denser microstructure in oxidized MP gels treated with SC and CC + SC. Therefore, the combination of CC and SC not only inhibits MP oxidation but also improves gel quality.

Ultrasound improves the digestibility of oxidized silver carp (Hypophthalmichthys molitrix) myofibrillar protein: Changes from structure to peptide release

The objective of this study was to investigate the effect of ultrasound on the digestibility of oxidized silver carp myofibrillar protein (MP). The MP solutions were oxidized with a hydroxyl radical generating system, and subsequently subjected to 100 W, 150 W, 200 W ultrasound treatment, respectively. The results showed that ultrasound effectively recovered the reduction in the digestibility of oxidized MP, especially the 150 W ultrasound achieved the best effect. The 150 W ultrasound reduced the particle size and turbidity of oxidized MP by 26.71 % and 35.49 %, respectively. The analysis of sulfhydryl, disulfide bonds, intrinsic fluorescence, and surface hydrophobicity suggested that ultrasound caused the breakage of disulfide bonds, which promoted the depolymerization oxidized MP. The morphology observed by atomic force microscope further evidenced that ultrasound reduced the degree of oxidized MP aggregation. The results of peptidomics showed that ultrasound treatment largely increased the peptide release of oxidized MP during the gastrointestinal digestion, especially the peptide containing lysine and arginine. Take together, ultrasound promoted the break of disulfide bond, which led to the depolymerization of oxidized MP and thus improved the digestibility of oxidized MP.

Recent Advances, Challenges, and Functional Applications of Natural Phenolic Compounds in the Meat Products Industry

Natural phenolic compounds (NPCs) have been proven to effectively extend the storage time of meat products in recent years. To promote the discovery of more NPCs and their applications, this review examines recent progress in the classification, antioxidant, and antibacterial mechanisms of NPCs used in meat products. These compounds are found in both edible and inedible parts of plants, including fruits, vegetables, and trees. The recycling of agricultural by-products aligns with green agricultural trends and serves as a guideline for developing new sources of natural additives. Studies on the application of NPCs in various livestock and poultry products, either directly mixed into the matrix or indirectly contacted by preparation into bioactive films and packaging materials, has highlighted the great potential of NPCs. The pro-oxidative effects of NPCs on proteins and their interactions with biological macromolecules, such as proteins, provide new ideas for in-depth research on antioxidant and antibacterial mechanisms.

The pro-oxidant action of high-oxygen MAP on beef patties can be counterbalanced by antioxidant compounds from common hawthorn and rose hips

The objective of this research was to evaluate the effectiveness of antioxidant-rich extracts from rose hip (Rosa canina L.; RC) and hawthorn (Crataegus monogyna Jacq.; CM) at minimizing the oxidative damage to proteins and lipids in beef patties subjected to a high‑oxygen (HiOx-MAP) and vacuum (Vacuum) packaging atmosphere. The extracts of RC and CM were characterized by quantifying bioactive compounds, namely, phenolic compounds, tocopherols and vitamin C. Both fruits had high concentrations of bioactive compounds, with RC having the highest total phenolic and vitamin C content. Yet, CM was the most efficient in protecting beef patties against protein carbonylation, reducing, as a result, the instrumental toughness in cooked beef patties. The use of CM and RC extracts in beef patties significantly improved consumer purchase intention in HiOx-MAP packaging systems. The use of CM and RC extracts or their combination in future research would be an effective antioxidant means to decrease the pro-oxidative effects caused by HiOx-MAP in red meat.

Effect of Capsaicin and Dihydrocapsaicin in Capsicum on Myofibrillar Protein in Duck Meat

Spice and its extracts have gained widespread utilization as natural and eco-friendly additives, imparting enhancements in flavor, color, and antioxidative attributes to meat-based products. This work aims to study the effect mechanism of capsaicin (CA) and dihydrocapsaicin (DI) in capsicum (chili pepper) on the structure and function of myofibrillar proteins (MPs) in duck meat during thermal treatment. The results showed that at a CA-DI to MP ratio of 1:500 (g/g) following a 12 min heat treatment, the carbonyl content of MPs in duck meat decreased by 48.30%, and the sulfhydryl content increased by 53.42%. When the concentration was 1:500 (CA-DI, g/g) after 24 min of heat treatment, the •OH and DPPH radical scavenging rates were highest at 59.5% and 94.0%, respectively. And the initial denaturation temperature of MPs was the highest at 96.62 °C, and the thermal absorption was lowest at 200.24 J g-1. At the parameter, the smallest particle size and size distribution range of MP were 190 nm (9.51%). Furthermore, the interplay between CA-DI and MPs contributed to a reduction in the protein particle size and intrinsic fluorescence. In summary, the combination of CA-DI and MPs played a crucial role in inducing protein unfolding and disintegration.

Mechanistic Insights into Myofibrillar Protein Oxidation by Fenton Chemistry Regulated by Gallic Acid

Gallic acid (GA, 3,4,5-trihydroxybenzoic acid) is a widely used natural food additive of interest to food chemistry researchers, especially regarding its effects on myofibrillar protein (MP) oxidation. However, existing studies regarding MP oxidation by GA-combined with Fenton reagents are inconsistent, and the detailed mechanisms have not been fully elucidated. This work validated hydroxyl radical (HO·) as the primary oxidant for MP carbonylation; in addition, it revealed three functions of GA in the Fenton oxidation of MP. By coordination with Fe(III), GA reduces Fe(III) to generate Fe(II), which is the critical reagent for HO· generation; meanwhile, the coordination improves the availability and reactivity of Fe(III) under weakly acidic and near-neutral pH, i.e., pH 4-6. Second, the intermediates formed during GA oxidation, including semiquinone and quinone, promoted Fenton reactivity by accelerating Fe catalytic cycling. Finally, GA can scavenge HO· radicals, thus exhibiting a certain degree of antioxidant property. All three functions contribute to MP oxidation as observed in GA-containing meat.

In vitro digestion of a mixed gel of pork muscle and resistant starch: Salt-soluble protein perspective

The in vitro digestion of a mixed gel (MS) of pork muscle and resistant starch (RS) was investigated and the role of the salt-soluble protein (SSP) in the function promotion of the mixed gel was clarified. The results showed that the mixed muscle gel (MS) and the addition of RS to muscle gel (M + S) presented an improved protein digestion, as indicated by a reduced particle size of the hydrolysates, more degradation of proteins with large molecular weight and more generation of free amino acids compared with the RS-free muscle gel (M). Meanwhile, the hydrolysates of the M + S and MS showed intensified DPPH radical scavenging activities. Specifically, the MS exerted preferable properties in protein digestion and antioxidant activity. Similar digestion characteristics were noticed in mixed SSP gels.The current study revealed that the reinforced functionality of the mixed muscle gel was associated with the binding relationships between SSP and RS during cooking.

The effects of blanching on composition and modification of proteins in navy beans (Phaseolus vulgaris)

Blanching is an important process in the preparation of navy beans (Phaseolus vulgaris L.) for canning. We here explore the effect of blanching which can profoundly affect protein composition and introduce protein-primary-level modifications. Amino acid analysis showed significantly decreased protein abundance (58.5%) in blanched beans compared to raw beans. Proteomic analyses revealed a decrease in high molecular weight isoforms of the major storage globulin proteins phaseolin (mean fold-change -3.7) and legumin (mean fold-change -2.5) and concomitant increase in their low molecular weight isoforms (mean fold-change 6.4 and 8.3, respectively). Blanched beans also had decreased abundance of lipoxygenase (mean fold-change -13.1), an enzyme responsible for product spoilage during storage. Increased lysinoalanine (up to 47%) and highly modified protein fragments were found in the processing waters, indicating heat- induced modifications. Correlating these molecular level changes thus provides a basis for evaluating how processing parameters can be modified to increase protein food quality.

Effectiveness of Sprayed Bioactive Fruit Extracts in Counteracting Protein Oxidation in Lamb Cutlets Subjected to a High-Oxygen MAP

High-oxygen packaging atmosphere (High-Ox-MAP) promotes meat protein oxidation and leads to texture deterioration. This study was conceived to assess the extent to which sprayed fruit extracts could inhibit the oxidative damage to proteins in lamb cutlets subjected to High-Ox-MAP (10 days/4 °C) and subsequent roasting (10 min/180 °C). Extracts from oaknut (Quercus ilex subsp. ballota; QI), rose hips (Rosa canina L.; RC), common hawthorn (Crataegus monogyna Jacq.; CM) and strawberry tree (Arbutus unedo L.; AU) were characterized for bioactive compounds (phenolic subclasses, tocopherols and ascorbic acid) and in vitro bioactivities. While the four fruits showed relevant antioxidant potential, CM had the highest phenolics and tocopherol content and that was reflected in efficient antiradical activity. The in vitro activity of this fruit to inhibit meat protein oxidation was, however, lower than that displayed by the other fruits. Taking the results altogether, CM was also found to be most efficient in protecting lamb cutlets from lipid oxidation. All fruits were able to inhibit thiols oxidation except RC, which seemed to reduce protein thiols. Among fruits, QI was the most efficient in protecting lamb cutlets against protein carbonylation as a plausible involvement of ellagitannins. The inhibition of protein oxidation by QI was reflected in significantly lower instrumental hardness in cooked lamb cutlets. Spraying lamb cutlets with extracts from QI, RC and CM improved consumers' purchase intention after chilled storage. This antioxidant strategy seems to be a feasible and efficient solution to the pro-oxidative effects caused by High-Ox-MAP in red meat.

Effect of soaking conditions on the formation of lipid derived free radicals in soymilk

Lipid derived free radical in soymilks were studied by combining 5,5-dimethyl-pyrroline-l-oxide (DMPO) spin trap, chloroform-methanol extraction and electron spin resonance (ESR) spectroscopy. Five lipid derived free radical adducts: DMPO-X, DMPO-L, DMPO-R, DMPO-LOO, and DMPO-RO were presented in soymilks. The total amounts of spins increased as the soaking temperature increased from 4 °C to 50 °C and the soaking pH increased from 3 to 9 and in paralleled with the diffusion of soybean exudates to soaking water. Prolonged soaking of soybean at 50 °C resulted in a higher signal intensity of DMPO-R than that of DMPO-LOO. Soybean lipoxygenases (LOXs) were responsible for the formation of lipid derived free radicals in soymilks. Soybean exudates affected the total amounts of lipid radicals in linoleic acid (LA) - LOX model system. The relative signal intensities of DMPO-R and DMPO-LOO were depended on the contents of soybean exudates in the system.

Influence of hydrothermal treatment on the structural and digestive changes of actomyosin

BACKGROUND

Heat treatment induces both structural and digestive change of meat protein. However, little has been revealed regarding the associations between structural changes and digested peptides of myofibrillar proteins. This work investigated the effects of heat treatment on the structures and in vitro digestibility of actomyosin, and the peptidomics of the digests were analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

Heat treatment resulted in unfolding and aggregation behavior of actomyosin according to the results of surface hydrophobicity and particle size. Formation of disulfide bonds and increase in carbonyl groups that occurred during heat treatment of actomyosin indicated the oxidation of specific residues. Unfolding behavior could elevate digestibility of actomyosin by exposing residues, based on the identification of peptides in digests of actomyosin using LC-MS/MS. However, the disulfide bond proved to reduce the action of digestive proteases, since the peptides number (increased from 56 to 86 in sample heated at 70 °C for 30 min) and peptides intensity in digests largely increased after the addition of dithiothreitol (DTT). Heating at higher temperature (100 °C) induced severer aggregation and oxidation, which resulted in lower digestibility of actomyosin than that heated at 70 °C by burying or damaging partial cleavage sites for digestive proteases.

CONCLUSIONS

This work highlights the huge influence of heat treatment on the multi-scale structures of myofibrillar proteins, which largely changed the peptides composition in protein digests. © 2019 Society of Chemical Industry.

Physicochemical and microbiological changes during the refrigerated storage of lamb loins sous-vide cooked at different combinations of time and temperature

This study aimed to determine the influence of cooking temperature (either 60 ℃ or 80 ℃) and time (6 h or 24 h) on the physicochemical (weight loss, moisture content, instrumental color, instrumental texture, lipid and protein oxidation) and microbiological changes underwent by sous-vide cooked lamb loins during refrigerated storage for 30 days. There was a slight trend to decreasing weight losses in some of the cooking treatments, but only in samples cooked at 60 ℃ for 6 h it was paralleled with an increase in moisture content. The only noteworthy oxidative change was a marked decrease in conjugated dienes after two weeks of storage in samples cooked at 80 ℃ for 24 h. Neither instrumental texture nor color showed noticeable variations during the storage. Microbial population remained quite low during the whole refrigerated storage. Overall, most of the studied parameters showed only scarce changes throughout 30 days of refrigerated storage that most likely would not influence the quality of sous-vide cooked loin lambs.

Effect of cooking on meat proteins: mapping hydrothermal protein modification as a potential indicator of bioavailability

Thermal treatment of meat proteins induces a range of observable and molecular-level changes. In order to understand and track these heat-induced modifications at the amino acid level, various analytical techniques were used. Changes were observed both in the soluble and in the insoluble fractions after hydrothermal treatment of minced beef samples. Redox proteomics clearly indicated increasing oxidative modification of proteins with increased heat exposure. Collagens in the soluble fraction and myosin in the insoluble fraction were found to be highly susceptible to such modifications. Maillard reaction products in the insoluble and pyrrolidone formation in the soluble fraction steadily increased with increased heat exposure. Fluorescence studies indicated a rapid increase in fluorescence with heat, suggesting the formation of advanced glycation end products. Overall these results provide a deeper understanding of the effect of cooking on meat proteins and the possible relationship to processing conditions in meat-derived food.

Oxidative and nitrosative stress induced in myofibrillar proteins by a hydroxyl-radical-generating system: impact of nitrite and ascorbate

Understanding the chemistry behind the redox properties of nitrite and ascorbate is essential to identify the impact of curing agents on food quality and optimize the formulation of cured meat products. This study was designed to gain insight into the interactions between curing agents and myofibrillar proteins (MPs) during in vitro oxidation by a hydroxyl-radical-generating system. MPs (4 mg/mL) were oxidized for 4 days at 37 °C under constant stirring with 25 μM iron(III) and 2.5 mM hydrogen peroxide. Dependent upon the addition of nitrite (0, 75, and 150 mg/L) and ascorbate (0, 250, and 500 mg/L), nine different reaction units were prepared in triplicate (n = 3) according to a total factorial design. Upon completion of the oxidation assay, samples were analyzed for the concentration of tryptophan (TRP), α-aminoadipic semialdehyde (AAS), Schiff bases (SBs), and 3-nitrotyrosine (3NT). Ascorbate at 250 mg/L significantly inhibited the depletion of TRP (∼20% inhibition) and the formation of AAS and SBs (>90% inhibition) in MP suspensions. Nitrite, alone, had a negligible effect on protein oxidation but induced the formation of a specific marker of nitrosative stress, namely, 3NT. Ascorbate was also efficient at inhibiting the formation of 3NT by a dose-dependent anti-nitrosative effect and enabled the antioxidant action of nitrite.

Carbonylation of myofibrillar proteins through the maillard pathway: effect of reducing sugars and reaction temperature

Carbonylation is recognized as one of the most remarkable chemical modifications in oxidized proteins and is generally ascribed to the direct attack of free radicals to basic amino acid residues. The purpose of this work was to investigate the formation of specific carbonyls, α-aminoadipic and γ-glutamic semialdehydes (AAS and GGS, respectively), in myofibrillar proteins (MP) through a Maillard-type pathway in the presence of reducing sugars. The present study confirmed the concurrent formation of protein carbonyls and advanced glycation end-products (AGEs) during incubation (80 °C/48 h) of MP (4 mg/mL) in the presence of reducing sugars (0.5 M). Copper irons (10 μM) were found to promote the formation of protein carbonyls, and a specific inhibitor of the Maillard reaction (0.02 M pyridoxamine) blocked the carbonylation process which emphasize the occurrence of a Maillard-type pathway. The Maillard-mediated carbonylation occurred in a range of reducing sugars (0.02-0.5 M) and reaction temperatures (4-110 °C) compatible with food systems. Upcoming studies on this topic may contribute further to shed light on the complex interactions between protein oxidation and the Maillard reaction and the impact of the protein damage on food quality and human health.

Avocado, sunflower and olive oils as replacers of pork back-fat in burger patties: effect on lipid composition, oxidative stability and quality traits

The present study investigates the effects of avocado, sunflower and olive oils used as back-fat replacers, on the fatty acid composition, oxidative stability, volatiles profile and color and texture properties of cooked pork patties. The vegetable oils modified the fatty acid profiles of the patties by lowering the percentages of SFA (from 36.96% to ~25.30%) and reducing the atherogenic index (from 0.41 to ~0.24). Vegetable oils had higher amounts of antioxidant compounds such as tocopherols (10.8-53.9 mg/100 g) than back-fat (5.9 mg/100 g). Consistently, patties manufactured with the oils had significantly lower amounts of lipid and protein oxidation products than control patties. Avocado oil contributed with specific aroma-active terpenes to patties and had a significant impact on particular color and texture parameters. The results from this study highlight the technological applications of the vegetable oils as food ingredients in the design of healthier meat commodities.

Fluorescent HPLC for the detection of specific protein oxidation carbonyls - α-aminoadipic and γ-glutamic semialdehydes - in meat systems

Precise methodologies for the routine analysis of particular protein carbonyls are required in order to progress in this topic of increasing interest. The present paper originally describes the application of an improved method for the detection of α-aminoadipic and γ-glutamic semialdehydes in a meat system by using a derivatization procedure with p-amino-benzoic acid (ABA) followed by fluorescent high-performance liquid chromatography (HPLC). The method development comprises i) the description of a simple HPLC program which allows the efficient separation of the ABA and the key standard compounds and ii) the optimization of the procedure for the preparation of a meat sample in order to maximize the fluorescent signal for both protein carbonyls. Furthermore, the suitability of this method is evaluated by applying the technique to porcine burger patties. The present procedure enables an accurate and relatively fast analysis of both semialdehydes in meat samples in which they could play an interesting role as reliable indicators of protein oxidation.

Protein carbonylation and water-holding capacity of pork subjected to frozen storage: effect of muscle type, premincing, and packaging

The present work aimed to study the relationship between protein carbonylation and the loss of water-holding capacity (WHC) occurring during frozen storage of porcine muscles. Pork samples corresponding to two different muscle types, glycolytic M. longissimus dorsi (LD) and oxidative M. psoas major (PM), and subjected to two different premincing, minced (MINCED) and intact pork pieces (INTACT), and packaging, vacuum packaged (VACUUM) and packed in oxygen-permeable bags (OXYGEN), procedures were frozen (-18 °C/12 weeks) and analyzed at sampling times upon thawing (weeks 1, 4, 8, and 12) for the relative amount of specific protein carbonyls, α-aminoadipic and γ-glutamic semialdehydes (AAS and GGS, respectively), and their ability to hold water using two different techniques. The formation of protein carbonyls occurred concomitantly with the loss of WHC, and both phenomena were found to be more intense in LD muscles and in MINCED and OXYGEN pork samples. The loss in WHC was from ca. 10 to 30% in 12 weeks, depending on the method of determination. Plausible mechanisms by which protein carbonylation may decrease the WHC of pork samples are thoroughly discussed in the present paper. Besides the likely impact of protein carbonylation in the water-myofibrillar protein relationships, the implication of AAS and GGS in further reactions including plausible cross-linking would explain the decrease of these semialdehydes by the end of frozen storage and would reinforce their liability in the loss of WHC of porcine muscles. The exact nature of these reactions, however, should be investigated in further studies.

Avocado by-products as inhibitors of color deterioration and lipid and protein oxidation in raw porcine patties subjected to chilled storage

Processing of avocados generates an important amount of by-products such as peels and seeds that are rich in bioactive substances with proven radical suppressing activities. The objective of this study was to evaluate the effectiveness of peel and seed extracts from two avocado varieties-'Hass' and 'Fuerte'-as inhibitors of lipid and protein oxidation and color deterioration of raw porcine patties during chilled storage (4 °C/15 days). Avocado extracts significantly (p<0.05) reduced the loss of redness and the increase of lightness during storage of porcine patties. 'Fuerte' extracts were more efficient at inhibiting discoloration of chilled patties than 'Hass' extracts. Patties treated with avocado extracts had significantly lower amounts of TBA-RS than control ones throughout the storage. 'Hass' avocado extracts significantly inhibited the formation of protein carbonyls in chilled patties at day 15. The present results highlight the potential usage of extracts from avocado by-products as ingredients for the production of muscle foods with enhanced quality traits.

Effect of phenolic compounds on the formation of alpha-aminoadipic and gamma-glutamic semialdehydes from myofibrillar proteins oxidized by copper, iron, and myoglobin

The effect of selected phenolic compounds, namely, gallic acid, chlorogenic acid, genistein, catechin, cyanidin-3-glucoside and rutin, on the formation of specific protein carbonyls, alpha-aminoadipic and gamma-glutamic semialdehydes (AAS and GGS, respectively), from oxidized myofibrillar proteins, was studied in the present article. Suspensions containing myofibrillar proteins (20 mg/mL) and the aforementioned phenolic compounds (1 mM) were oxidized (37 degrees C for 20 days) in the presence of copper acetate, iron (FeCl(3)), or myoglobin (10 microM) in combination with 1 mM H(2)O(2) and analyzed for AAS and GGS using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). Suspensions with added alpha-tocopherol (1 mM) and a control group (with no phenolic compound) were also considered. In the presence of copper, the alpha-tocopherol and most phenolic compounds significantly inhibited the formation of AAS and GGS. In iron- and myoglobin-oxidized suspensions, however, some of those phenolic compounds (i.e., chlorogenic acid and genistein) promoted the formation of the semialdehydes. Besides the influence of the oxidation promoters, the overall effect of plant phenolics on protein oxidation is likely affected by the chemical structure of the phenolics and the result of the interactions between these compounds and myofibrillar proteins. Plausible mechanisms for the antioxidant and pro-oxidant effects of plant phenolics on myofibrillar proteins are proposed in the present article. This study highlights the complexity of redox reactions between plant phenolics and oxidizing myofibrillar proteins.