Fat content has a significant impact on protein oxidation occurred during frozen storage of beef patties

Effect mechanism of capsaicin and dihydrocapsaicin in chili on the oxidative stability of myoglobin in duck meat

BACKGROUND

Myoglobin (Mb) in duck meat is commonly over-oxidized when heated at high temperatures, which may worsen the color of the meat. Enhancing the oxidative stability of Mb is essential for improving the color of duck meat. Capsaicin and dihydrocapsaicin (CA-DI) in chili exhibit antioxidant properties. This study investigated the effects of CA-DI on the structure and oxidative damage of Mb by fluorescence spectroscopy, differential scanning calorimetry analysis and particle size in duck meat during heat treatment.

RESULTS

When the ratio of CA-DI to Mb was 10:1 g kg-1 and heat-treated for 36 min, oxymyoglobin significantly increased, and metmyoglobin significantly decreased compared with the control group (P < 0.05). In parallel, the carbonyl content of Mb in the CA-DI group decreased by 43.40 ± 0.10%, the sulfhydryl content increased by 188 ± 0.21%, and the free radical scavenging activity of Mb was significantly enhanced (P < 0.05). Moreover, the addition of CA-DI resulted in a significant decrease in the particle size of the Mb surface (P < 0.05). When the ratio of CA-DI to Mb was 10:1 g kg-1, CA-DI enhanced the thermal stability and significantly increased the thermal denaturation temperature of Mb. The molecular docking results indicated that hydrophobic interactions and hydrogen bonds were involved in the binding of CA-DI to Mb.

CONCLUSION

CA-DI could combine with Mb and improve the oxidation stability of Mb in duck meat. This suggested that CA-DI could be a potential natural antioxidant that improves the color of meat products. © 2024 Society of Chemical Industry.

Inhibitory effects of chitosan grafted chlorogenic acid on antioxidase activity, and lipid and protein oxidation of sea bass (Lateolabrax japonicus) fillets stored at 4 °C

BACKGROUND

Sea bass (Lateolabrax japonicus), a marine fish, is prone to spoilage due to its high nutritional value. Preservatives are commonly used for storage for the production of fish fillets. In this work, chitosan (CS) was grafted onto chlorogenic acid (CA) to obtain a new preservative, chitosan grafted chlorogenic acid (CS-g-CA), which could enhance the biochemical properties of chitosan and obtain better antibacterial and antibacterial properties. This study therefore investigated the inhibitory effects of CS-g-CA on antioxidant enzyme activity, and lipid and protein oxidation of sea bass fillets stored at 4 °C.

RESULTS

Compared with the control group on day 9, the activity of 63% catalase (CAT), 78% superoxide diamidase (SOD), 73% glutathione peroxide enzyme (GSH-Px) and 60% DPPH scavenging activity was retained by CS-g-CA treatment. Changes in thiobarbituric acid (TBA) and conjugated diene (CD) values were delayed by CS-g-CA treatment. The use of CS-g-CA retards protein oxidation by inhibiting the formation of free amino acid and carbonyl groups, and maintaining a higher sulfhydryl content. Regarding myofibril degradation, CS-g-CA could maintain protein secondary structure by increasing the ratio of α-helices.

CONCLUSIONS

Chitosan-grafted chlorogenic acid could protect the activity of antioxidant enzymes and inhibit lipid oxidation by slowing down the production of lipid oxidation products. It also delayed protein oxidation by inhibiting oxidation product generation and stabilizing protein structure. It could therefore be used as a promising preservative for seafood. © 2022 Society of Chemical Industry.

Effect of Pre-Emulsion of Pea-Grass Carp Co-Precipitation Dual Protein on the Gel Quality of Fish Sausage

Currently, the processing method of introducing plant protein into meat products has attracted great attention. However, the direct addition of plant protein often leads to a decline in meat product quality. This paper aims to provide an efficient method for incorporating plant protein into fish sausage. Pea protein isolate (PPI), grass carp protein isolate (CPI) and pea-grass carp coprecipitated dual protein (Co) were derived from pea and grass carp by an isoelectric solubilisation/precipitation method. At the same time, the blended dual protein (BL) was obtained by blending PPI with CPI, and the plant and animal protein content of Co and BL was both controlled to be the same. The four proteins were combined with soybean oil and water to form a three-phase pre-emulsification system of protein-oil-water, which was added to grass carp meat as a replacement for animal fat to prepare fish sausage. The gelation properties of the four fish sausages and those without protein were analysed. The results showed that the gel quality of PPI fish sausage is poor, while the overall quality of Co fish sausage as a whole was significantly superior to that of PPI and BL, which was equivalent to CPI fish sausage. The sensory score of the Co fish sausage was slightly lower than that of CPI, but it had significantly higher water-holding capacity and hardness (p < 0.05). The Co fish sausage showed the synergistic effect of heterologous proteins, while BL had some antagonistic effects. This study shows that Co pre-emulsion is an effective strategy to introduce plant protein, so it has a good application prospect in the meat industry.

Active Packaging for the Extended Shelf-Life of Meat: Perspectives from Consumption Habits, Market Requirements and Packaging Practices in China and New Zealand

Active packaging (AP) has been developed to improve the safety, quality and integrity of food, and minimise food waste, while its application in meat is scarce. This review aims to describe meat production and consumption culture in China and New Zealand to provide the context for packaging innovation requirements, focusing on the emerging opportunities for AP to be used for the improvement of the shelf-life of pre-rigor, aged, and frozen-thawed meat products. Sustainable polymers utilised in the manufacturing of AP, manufacturing techniques, the release mechanisms of actives, and legal and regulatory constraints are also discussed. Diverse market compositions and consumption cultures in China and New Zealand require different packaging solutions to extend the shelf-life of meat. AP containing antimicrobials, moisture regulating agents, and antioxidants may be used for pre-rigor, dry- and wet-aged products and in improving the quality and shelf-life of frozen-thawed meat. Further innovations using sustainably produced polymers for AP, along with incorporating active compounds of multiple functions for effectively improving meat quality and shelf-life are necessary. Challenges remain to resolve issues with scaling the technology to commercially relevant volumes as well as complying with the rigorous legal and regulatory constraints in various countries.

Comparison of Superchilling and Supercooling on Extending the Fresh Quality of Beef Loin

This study compared the effects of superchilling and supercooling preservations for 15 days on the freshness and quality characteristics of beef loin. Beef freshness was evaluated by total aerobic count (TAC), total volatile basic nitrogen (TVB-N), and thiobarbituric acid reactive substances (TBARS), and instrumental color, drip loss, cooking loss, and texture profile analysis (TPA) were determined as quality parameters. All assays were compared with fresh control and normal chilling conditions (4 °C). The mean preservation temperatures of superchilling and supercooling were −3.9 °C and −2.1 °C, respectively. The freshness parameters indicated that both superchilling and supercooling extended the freshness of beef loin for 15 days, while chilled beef could not maintain the standard of freshness conditions. For quality parameters, there was no difference between the control and supercooling treatments, whereas superchilling exhibited higher drip loss and toughness compared to the control (p < 0.05). Therefore, this study demonstrated that supercooling was the best preservation technique to extend the freshness and quality of beef loin, but superchilling was not suitable to guarantee the quality of beef.

Effects of nitrite concentrations on the quality and protein oxidation of salted meat

The objective of this study was to investigate the effects of different concentrations of sodium nitrite on the quality and protein oxidation of salted meat during 21 days of curing. The salted meat was treated with sodium nitrite at 50, 100, and 150 mg/kg for curing, and salted meat without sodium nitrite was used as a control. The results showed that in salted meat added with sodium nitrite, the carbonyl group, disulfide bond, dityrosine, surface hydrophobicity, and the transformation rate from α-helix to β-sheet were all significantly reduced, whereas the sulfhydryl group content of myofibrillar proteins was significantly increased compared to the control. Meanwhile, the total volatile basic nitrogen and aerobic plate content were significantly decreased, while both the pH and a* value were significantly increased with an increase in nitrite concentration compared to the control group. Importantly, this phenomenon was also observed in salted meat treated with low doses of sodium nitrite (50 mg/kg). In conclusion, the quality of salted beef can be improved by adding low-dose sodium nitrite to inhibit protein oxidation during the curing process. PRACTICAL APPLICATION: A low dose of sodium nitrite inhibited the rate of α-helix to β-sheet transformation of myofibrillar proteins in salted meat, reducing the exposure of hydrophobic groups and decreasing the production of protein oxidation products and TVB-N to improve the quality of salted meat. These results provided a theoretical basis and technical guidance for the application of low-dose sodium nitrite in meat processing enterprises.

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.

Changes in nitrosohemachrome lead to the discoloration of spiced beef during storage

The discoloration of spiced beef during storage is a severe problem that limits the shelf life of products. This study explored the associations between discoloration and pH, water, lipid oxidation, and protein oxidation. Electron paramagnetic resonance and UV-Vis spectroscopy illustrated that the pigment of spiced beef was a pentacoordinate mononitrosylheme compound and its conjugated structure changed during storage. The low-field NMR and magnetic resonance imaging results showed that the mobility of water increased, and the water content decreased with the extension of storage time. Multivariate analysis showed that color attributes were negatively correlated with oxidation. The oxidation of nitrosohemachrome was the primary reason for the lightness (L*) and redness (a*) decline in spiced beef. In addition, water loss exerted a promotion function in the oxidation process. This study provides valuable information on maintaining the quality of spiced beef during storage.

Recent development in evaluation methods, influencing factors and control measures for freeze denaturation of food protein

Frozen storage is most widely adopted preservation method to maintain food freshness and nutritional attributes. However, at low temperature, food is prone to chemical changes such as protein denaturation and lipid oxidation. In this review, we discussed the reasons and influencing factors that cause protein denaturation during freezing, such as freezing rate, freezing temperature, freezing method, etc. From the previous literatures, it was found that frozen storage is commonly used to prevent freeze induced protein denaturation by adding cryoprotectants to food. Some widely used cryoprotectants (for example, sucrose and sorbitol) have been reported with higher sweetness and weaker cryoprotective abilities. Therefore, this article comprehensively discusses the new cryopreservation methods and providing comparative study to the conventional frozen storage. Meanwhile, this article sheds light on the freeze induced alterations, such as change in functional and gelling properties. In addition, this article could be helpful for the prolonged frozen storage of food with minimum quality related changes. Meanwhile, it could also improve the commercial values and consumer satisfaction of frozen food as well.

Improvement strategies for quality defects and oxidation of pale, soft and exudative (PSE)-like chicken meat: effects of domestic cooking and core temperature

In practice, this study will help to better elucidate the relationship between oxidation profile and meat quality, and provide consumers with recommendations for consuming PSE-like meat.

Effect of Multiple Freeze-Thaw Cycles on Lipid Degradation and Lipid Oxidation of Grass Carp Surimi Containing Different Amounts of Pork Back Fat

Fresh grass carp was used to produce surimi samples that were supplemented with 50 g/kg, 100 g/kg, or 150 g/kg pork back fat. The lipid composition, lipase activity, lipid oxidation index, and lipoxygenase activity of samples subjected to repeated freeze-thaw process were determined to assess the effects of the added fat on lipolysis and lipid oxidation of grass carp surimi. Freeze-thaw treatment increased free fatty acid content, mainly due to the decomposition of phospholipids and some neutral lipids by lipase. With repeated freeze-thaw treatment, the levels of free fatty acids and phospholipids were correlated with the lipid oxidation indexes and lipoxygenase activity, indicating that lipid degradation can promote lipid oxidation. In the same freeze-thaw cycle, surimi products with high fat content are more vulnerable to oxidative damage, neutral lipids are the main source of free fatty acids in the early stage of freeze-thaw, and phospholipids are the main source of free fatty acids in the late stage.

Low-Field NMR Analysis of Chicken Patties Prepared with Woody Breast Meat and Implications to Meat Quality

The scope of this paper was to investigate the effects of water distribution differences on the quality and feasibility of chicken patties supplemented with woody breast (WB). Chicken patties, containing differing amounts of WB (0%, 25%, 50%, 75%, 100%) were analyzed using low-field NMR. Quality differences between chicken patties were further evaluated by combining lipid and protein properties, fry loss (FL), color (L*, a*, b*), texture (hardness, springiness, chewiness, cohesiveness, resilience), microstructure, and sensory characteristics. The results expressed that both lipid and protein oxidation increased and immobilized water in chicken patties can be converted to free water more easily with increasing levels of WB. Additionally, the free water ratio decreased, water freedom increased, and the bound water ratio increased (p < 0.05). Fry loss, color, texture (hardness, springiness, chewiness), microstructure, and sensory (character, organization, taste) characteristics deteriorated significantly when the WB inclusion level exceeded 25%. Particularly, characteristics of texture (chewiness and character) and sensory (character and organization) decreased significantly as WB inclusion increased past 25% (p < 0.01). Furthermore, fry loss, texture, and overall microstructure partially confirmed the moisture variation of chicken patties as the potential cause of the abnormal quality. Although the experimental data expressed that mixing to 35% WB inclusion was feasible, the practical and economic impact recommends inclusion levels to not exceed 30%.

Freezing of meat and aquatic food: Underlying mechanisms and implications on protein oxidation

Over the recent decades,protein oxidation in muscle foods has gained increasing research interests as it is known that protein oxidation can affect eating quality and nutritional value of meat and aquatic products. Protein oxidation occurs during freezing/thawing and frozen storage of muscle foods, leading to irreversible physicochemical changes and impaired quality traits. Controlling oxidative damage to muscle foods during such technological processes requires a deeper understanding of the mechanisms of freezing-induced protein oxidation. This review focus on key physicochemical factors in freezing/thawing and frozen storage of muscle foods, such as formation of ice crystals, freeze concentrating and macromolecular crowding effect, instability of proteins at the ice-water interface, freezer burn, lipid oxidation, and so on. Possible relationships between these physicochemical factors and protein oxidation are thoroughly discussed. In addition, the occurrence of protein oxidation, the impact on eating quality and nutrition, and controlling methods are also briefly reviewed. This review will shed light on the complicated mechanism of protein oxidation in frozen muscle foods.

The dose-dependent effects of polyphenols and malondialdehyde on the emulsifying and gel properties of myofibrillar protein-mulberry polyphenol complex

The effects of mulberry polyphenols and malondialdehyde (MDA) on the emulsifying and gel properties of myofibrillar protein (MP) were studied. Emulsibility and gel properties of MP were compared in range of mulberry polyphenol/MDA concentrations by particle size, Zeta potential, antioxidant capacity, gel strength, water-holding capacity (WHC), rheological properties and microstructure. Mulberry polyphenols enhanced the inoxidizability of MP emulsion but decreased its emulsifying property. MDA at intermediate concentrations (5-20 mM) improved the elasticity, strength, and WHC of polyphenols-modified MP emulsion gel, while at high concentration (40 mM) it destroyed the emulsion gel, resulting in "oil leakage". Polyphenol is not conducive to the gelation but weaken the oxidative damage of MDA to protein. The gel structure of MP emulsion collapsed after high dose of polyphenols or MDA treated. Thus, to maintain uniform textural and antioxidant activity of meat product, both polyphenols addition and oxidation intensity should be controlled simultaneously.

Antioxidant activity of purslane extract and its inhibitory effect on the lipid and protein oxidation of rabbit meat patties during chilled storage

BACKGROUND

Currently, synthetic antioxidants have been widely used to retard lipid and protein oxidation in the meat industry. However, consumers have concerns about these synthetic antioxidants because of their potential toxicological effects. Accordingly, natural antioxidants can be used as a result of their health safety compared to synthetic antioxidants. The present research aimed to assess the protective effects of purslane (Portulaca oleracea L.) extract (PE) against lipid and protein oxidation under chilled storage for 12 days. Rabbit meat patties were divided into five experimental groups: control (without extract), butylated hydroxytoluene BHT (with 0.02% BHT, w/w) and the different concentrations of PE (0.1%, 0.3% and 0.5%, w/w) added to rabbit meat patty labeled as 0.1% PE, 0.3% PE and 0.5% PE groups, respectively. 1,1-Diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, lipid oxidation and protein oxidation were determined, and kinetic models were employed.

RESULTS

PE showed the strongest DPPH and ABTS radical scavenging activity, and the half maximal inhibitory concentrations (i.e. IC₅₀ ) of DPPH and ABTS radicals were 5.112 ± 0.384 and 12.607 ± 2.130 μg mL^-1 , respectively. Samples that were treated with PE showed low lipid and protein oxidation. Furthermore, the results of kinetic models indicated that PE could reduce the rates of lipid and protein oxidation.

CONCLUSION

PE showed a preservative effect with respect exerting a protective effect against lipid and protein oxidation under chilled storage conditions. Our findings demonstrate the strong potential of PE as a natural antioxidant in meat and meat products. © 2020 Society of Chemical Industry.

Changes in the thermal stability and structure of myofibrillar protein from quick-frozen pork patties with different fat addition under freeze-thaw cycles

Changes in thermal stability and structure of myofibrillar protein from pork patties with different fat addition (0%, 5%, 10%, 15% and 20%) under freeze-thaw (F-T) cycles were discussed. The results showed that the total sulfhydryl, reactive sulfhydryl, free amino group, α-helix and β-sheet contents, fluorescence intensity (FI), and protein thermal stability (T_max, ∆H_total) of samples with the same fat content were significantly decreased, while the β-turn and random-coil content and the maximum fluorescence emission wavelength (λ_max) were significantly increased with increasing F-T cycles (P < 0.05). These changes in samples with 20% fat at the 5th F-T cycle were obvious and were verified by the decreases in ∆H_total (26.1%), reactive sulfhydryl (16.1%), and FI (16.8%) compared with the patties without fat. Therefore, repeated F-T cycles could decline the thermal stability of protein, destroy the protein structure of patty, and the changes were positively correlated with fat content of patty.

Air frying combined with grape seed extract inhibits Nε-carboxymethyllysine and Nε-carboxyethyllysine by controlling oxidation and glycosylation

Advanced glycation end products (AGE), compounds formed in meat at the advanced stage of Maillard reaction, are easily exposed to thermal processing. Improving cooking condition and adding antioxidants are 2 common ways for AGE reduction. The present work compared the inhibition of grape seed extract (GSE) on levels of free and protein-bound N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) in chicken breast under deep-frying and air-frying conditions. Efficiency of 5 concentrations of GSE (0.0, 0.2, 0.5, 0.8, and 1.0 g/kg) in retarding oxidation, glyoxal (GO), methylglyoxal (MGO), lysine (Lys), Maillard reaction degree (A₂₉₄, A₄₂₀), and Shiff's base were tested. Results showed that 0.5 g/kg GSE before heating significantly (P < 0.05) reduced AGE in fried breast chicken, whereas excessive supplementation of GSE (0.8 and 1 g/kg) was reverse. Air frying was found significantly (P < 0.05) better than deep frying to reduce the precursor substances (GO, MGO, and Lys) of AGE. In conclusion, GSE-derived polyphenols exhibited different inhibitory effects on oxidation and glycosylation at different concentrations. We found that 0.5 g/kg of GSE combined with air frying was the best recommendation for inhibiting CML and CEL.

Oxidative stability, proteolysis, and in vitro digestibility of fresh and long-term frozen stored in-bag dry-aged lean beef

Effect of air velocities, stepwise in-bag ageing and ageing time on the oxidative stability, proteolysis and digestibility of fresh and long-term frozen-stored dry-aged lean beef were studied. Increased air velocities and stepwise ageing regime had no effect (P > 0.05) on dry-aged beef lipid and protein oxidative stabilities and proteolysis pattern compared to control straight-dry-ageing. TBARS, protein carbonyl and free amino acids (FAAs) increased (P > 0.05) with ageing time. In-bag dry-ageing of beef improved its lipids and protein oxidative stability during long-term frozen storage compared to unaged beef. Improvement in beef protein digestibility was observed through increased release of FAAs and appearance of small protein fragments from SDS-PAGE in dry-aged samples compared to the unaged. The high lipid and protein oxidative stability of long-term frozen lean beef produced using stepwise in-bag ageing process suggest potential for the process to be used for producing dry-aged meat for export.

A comprehensive insight into the effects of microbial spoilage, myoglobin autoxidation, lipid oxidation, and protein oxidation on the discoloration of rabbit meat during retail display

The effects of the retail display temperature (8 °C, 3 °C and - 1 °C) on the discoloration of the Longissimus thoracis et lumborum of rabbits and the associations among such effects with microbial spoilage, myoglobin autoxidation, lipid oxidation, and protein oxidation were investigated. The total aerobic count, total volatile basic nitrogen content, metmyoglobin content, protein carbonyl content, and contents of thiobarbituric acid-reactive substances steadily increased during retail display. Moreover, the lightness and redness of the rabbit meat significantly (P < 0.05) declined over time, whereas the yellowness increased considerably (P < 0.05) with prolonged retail time. Canonical correlation analysis suggested that microbial spoilage, myoglobin autoxidation, lipid oxidation, and protein oxidation jointly affected rabbit meat color. Linear mixed models further revealed that microbial spoilage, myoglobin autoxidation, lipid oxidation and protein oxidation positively affected yellowness, and they inversely impacted lightness and redness.

Effect of freeze-thaw cycles on the quality of quick-frozen pork patty with different fat content by consumer assessment and instrument-based detection

The change in quality of quick-frozen patties containing different amounts of added fat (0%, 5%, 10%, 15%, and 20%) under different freeze-thaw (F-T) cycles (a F-T cycle was performed by freezing at -18 °C and thawing at 4 °C) was evaluated. The results showed that the a*-values of samples were significantly decreased, while L*-values, b*-values, thawing loss, and cooking loss were notably increased after 3 F-T cycles. Low-field nuclear magnetic resonance (LF-NMR) results showed that the water mobility of patties was enhanced. Textural properties (hardness, springiness, cohesiveness, and chewiness) of patties were significantly decreased after 5 F-T cycles (P < 0.05). Lipid and protein oxidation were aggravated with increasing fat content and number of F-T cycles, as confirmed by the increase in lipid peroxides, TBARS, and carbonyl content. Therefore, the results from instrument-based detection and consumer scores indicated that repeated F-T cycles accelerated the quality deterioration of quick-frozen pork patties, and rendered them unacceptable after 3 F-T cycles.

Interrelationship between myoglobin oxidation and lipid oxidation during the processing of Cantonese sausage with d-sodium erythorbate

BACKGROUND

Pork is used as raw material to produce Cantonese sausage, and 0.5 or 1 g kg^-1 of d-sodium erythorbate is added to the pork meat. In this study the myoglobin oxidation rate, relative metmyoglobin content, heme iron content, redness, pH, free radical content and thiobarbituric acid reactive substance (TBARS) value were measured at different processing times and different content of d-sodium erythorbate.

RESULTS

It was found that d-sodium erythorbate significantly reduced the free radical content and myoglobin and lipid oxidation rates and increased heme iron levels. When d-sodium erythorbate was added to the sausage, the absorption peak of myoglobin porphyrin shifted left, migrating from 414 to 405 nm. At 72 h, with an increase in the d-sodium erythorbate content, a significant negative correlation was identified between heme iron and the degree of redness (P < 0.01).

CONCLUSION

During sausage processing, there are strong correlations among TBARS values, free radical content, metmyoglobin levels, heme iron levels, a* and pH at the same d-sodium erythorbate level. At the same processing time, adding d-sodium erythorbate can slow the rate of myoglobin and lipid oxidation and prevent the discoloration of sausage. © 2019 Society of Chemical Industry.

Effect of grape seed extract combined with modified atmosphere packaging on the quality of roast chicken

The purpose of this study was to screen out the appropriate concentration of grape seed extract solution and study the effects of grape seed extract combined with modified atmosphere packaging on the physical and chemical properties of roasted chicken during storage at 4°C. Samples were stored in 3 different packages: A (air packaging), M (modified atmosphere packaging, CO₂/N₂ = 40%/60%), and P (0.5% grape seed extract solution treatment combined with modified atmosphere packaging, CO₂/N₂ = 40%/60%). Microbiological analysis, pH, headspace composition, color, and lipid oxidation of roasted chicken were measured. The results showed that 0.5% is the suitable concentration of grape seed extract preservative for the storage of modified atmosphere packaged roast chicken. Compared with normal packaging (A) and single modified atmosphere packaging (M), 0.5% grape seed extract solution combined with modified atmosphere packaging (P) could effectively reduce the growth rate of total aerobic bacteria, Pseudomonas spp., mold, and yeast in roast chicken during low-temperature storage, reduce the lipid oxidation rate in roast chicken, and maintain the color stability of the product. This result could help the roast poultry processing industry to find more efficient ways to store and sell products.

Protein oxidation and in vitro digestibility of heat-treated fermented sausages: How do they change with the effect of lipid formulation during processing?

In the present work, it was aimed to evaluate the oxidative stress indicators and in vitro digestibility during the processing of heat-treated Turkish sausages (sucuk) manufactured using different lipid formulations. The utilization of olive oil in sausage formulations had considerable impacts on proximate composition, pH, and water activity. The increased olive oil content increased primary lipid oxidation products, whereas it decreased the secondary ones. The use of olive oil increased the total carbonyl content, while it decreased the α-aminoadipic semialdehyde concentration. In general, pepsin, trypsin, and α-chymotrypsin activities of the treatments were similar to each other. The heat treatment during the processing significantly increased most of the oxidation markers. Though strong correlations were recorded between specific oxidation markers, no relationship was detected between oxidation parameters and in vitro digestibility. The results indicated that the lipid formulation and processing operations had significant impact on chemical and functional properties of heat-treated fermented sausages, within the complex interrelationships between oxidation mechanisms. PRACTICAL APPLICATIONS: The present work pointed out the changes and correlations between specific oxidation markers and in vitro digestibility of heat-treated fermented sausages during the production procedure. Oxidation reactions that occur in both proteins and lipids could have drastic impact on overall quality; for this reason, it is of great importance to provide the data for lightening these impacts regarding the product types and production applications. Since heat-treated muscle foods are widely manufactured to meet industrial needs, the data obtained from this research would contribute to understand the effects of formulation and processing operations in the formation of oxidation products and change in digestibility, thereby to pioneer further research on this topic.

Effects of malondialdehyde as a byproduct of lipid oxidation on protein oxidation in rabbit meat

The effects of malondialdehyde (MDA) as a byproduct of lipid oxidation on myoglobin and myofibrillar proteins (MP) oxidations in muscle homogenates containing components native to rabbit muscle were investigated. For myoglobin, MDA could lead to increase in metmyoglobin percentage. For MP, MDA could promote protein carbonylation and loss of tryptophan fluorescence. In addition, MDA could affect reactive oxygen species (ROS)-generating system by promoting the formation of hypervalent myoglobin species and release of non-heme iron. The result of MDA-MP adducts fluorescence intensity indicated that ROS-generating systems may be the main reason for protein carbonylation at the later of incubation treatment. SDS-PAGE analysis revealed that the ability of ROS-generating systems to facilitate protein oxidation was enhanced with MDA, which was responsible for the formation of protein cross-linking throughout incubation treatment. Taken together, the ability of MDA on promoting the oxidation of MP in rabbit muscle homogenates may be relied on both adduct reactions and the influence on ROS-generating system.

Effect of long term chilled (up to 5 weeks) then frozen (up to 12 months) storage at two different sub-zero holding temperatures on beef: 3. Protein structure degradation and a marker of protein oxidation

Different chilled (~0.1 °C for up to 5 weeks) then frozen storage (up to 12 months) combinations and two frozen storage holding temperatures (-12 °C and -18 °C) effects on beef M. longissimus lumborum (LL) protein structure degradation and a marker of protein oxidation were tested. Particle size (PS) analysis and protein solubility results found storage combination effects on protein degradation to be significant (P < 0.05), although the influence of frozen holding temperatures was negligible. LL carbonyl, and nitrate and nitrite content responses were variable and yet broadly reflected an increased incidence of protein oxidation across increasing chilled storage and ensuing frozen storage periods - this aspect meriting future exploration. Total myoglobin content and the estimated myoglobin redox fractions (metmyoglobin, deoxymyoglobin, and oxymyoglobin) were also subject to storage treatment. These findings demonstrate the capacity for beef storage selection (chilled-then-frozen) to manage compositional protein changes and its implications on sensory quality traits across comparative 'long term' durations.