Cooked Chicken Breast Research Articles

Unraveling the impact of thermal modulation in heating and cooling dies on the fibrous structure of high-moisture meat alternatives

We aimed to create high-moisture plant-based meat alternatives (HPMAs) that closely mimic the fibrous structure found in conventional meat. To achieve this goal, we focused on the impact of modulating the heating and cooling die temperatures during the extrusion process on the structural properties of HPMAs. The optimal temperatures for the heating and cooling dies were determined to be 160 and 50 °C, respectively, following a comprehensive analysis of various quality characteristics. These included assessments of cutting strength, texturization degree, moisture content, and microstructure. Analyzing the correlation coefficients between heating and cooling die temperatures and the quality characteristics of HPMAs revealed that modulating the cooling die temperature has a greater impact on quality characteristics than modulating the heating die temperature. The quality characteristics of HPMAs were also compared with those of boiled and sous-vide cooked chicken breasts. The optimal HPMA exhibited the most similar fibrous macro- and micro-structure to sous-vide cooked chicken breast. Consequently, our study highlights the importance of modulating the heating die and cooling die temperatures, among various process parameters of high-moisture extrusion cooking, which is crucial for producing HPMAs closely resembling conventional meat.

Effects of gelatin coating on the preservative and sensory qualities of cooked chicken breast

Effects of gelatin coating on the preservative and sensory qualities of cooked chicken breast

High moisture extrusion of pea protein isolate to mimic chicken texture: Instrumental and sensory insights

High moisture extrusion processing (HMEP) is gaining attention in the plant-based food industry to obtain meat-like textures from different vegetal protein sources. The aim of this study was to evaluate the impact of extrusion process parameters (water feeding rate, barrel temperature and screw speed) on the texture and moisture content of high moisture extrudates (HME) from pea protein isolate using response surface methodology. Sensory textural profile of selected HME was compared with those of cooked chicken breast and a commercial extruded meat analogue sample. Extrusion process parameters had a significant effect on the characteristics of the final product. Barrel temperatures between 145 °C and 165 °C and a water feed rate between 53% and 57% produced HME with an instrumental texture similar to cooked chicken breast, 165 °C and 55% water feed being the conditions that produced the HME with the highest meat-like appearance and sensory fibrousness.

Estimating In Vitro Protein Digestion and Protein Digestibility Corrected Amino Acid Score of Chicken Breasts Affected by White Striping and Wooden Breast Abnormalities.

An understanding regarding impacts of growth-related myopathies, i.e., white striping (WS) and wooden breast (WB), on the quality of dietary protein from cooked chicken breast is still limited. This study aimed at comparing protein content and in vitro protein digestion and estimating the in vitro protein digestibility corrected amino acid score (PDCAAS) of cooked chicken meat exhibiting different abnormality levels (i.e., normal, WS, and WS + WB). The results show that the WS + WB samples exhibited lower protein content, greater cooking loss, and greater lipid oxidation than those of normal samples (p < 0.05). No differences in protein carbonyls or the myofibril fragmentation index were found (p ≥ 0.05). Cooked samples were hydrolyzed in vitro using digestive enzyme mixtures that subsequently mimicked the enzymatic reactions in oral, gastric, and intestinal routes. The WS + WB samples exhibited greater values of free NH2 and degree of hydrolysis than the others at all digestion phases (p < 0.05), suggesting a greater proteolytic susceptibility. The in vitro PDCAAS of the WS + WB samples was greater than that of the other samples for pre-school children, school children, and adults (p < 0.05). Overall, the findings suggest that the cooked chicken breast with the WS + WB condition might provide greater protein digestibility and availability than WS and normal chicken breasts.

Impact of Wooden Breast myopathy on in vitro protein digestibility, metabolomic profile, and cell cytotoxicity of cooked chicken breast meat

This study investigated the impacts of Wooden Breast (WB) abnormality on in vitro protein digestibility and cytotoxicity of cooked chicken breast meat. Chicken breasts without (non-WB, n = 6) or with severe WB condition (WB, n = 6) were cooked and subjected to static in vitro protein digestion. The results showed no significant differences in free-NH2, degree of hydrolysis and distribution of peptide molecular weight between non-WB and WB samples at late intestinal digestion (P5), suggesting no adverse effects of WB on protein digestibility. Based on peptidomic analysis, P5 fraction of WB showed greater content of peptides with oxidative modification than that of non-WB. Untargeted metabolomics did not find any metabolites with potential toxicity either in non-WB and WB. Hydrolyzed non-WB and WB (1.56 to 100 µg/mL) did not affect viability of Caco-2 and Vero cells but addition of WB samples reduced Caco-2 cell viability compared with non-WB.

Effect of different inclusion levels of defatted Hermetia illucens larvae meal on fillet quality of gilthead sea bream (Sparus aurata)

Abstract In recent years, insect meal has attracted increasing interest as an innovative protein source to replace fish meal in feed formulation due to its valuable nutritional profile. This research aimed to compare the effects of different dietary inclusion levels (5, 10, and 15%) of Hermetia illucens (HI) larvae meal on Sparus aurata (initial weight: 98.6 ± 0.6 g) sensorial, technological, and nutritional fillets quality. Fish were fed experimental diets over 113 days. Results showed that the inclusion of defatted HI larvae meal did not induce off-flavours in gilthead sea bream fillets. No significant differences were found in appearance, mouthfeels, and texture, while a difference emerged in the trait ‘cooked chicken breast’ for odour and flavour characteristics. Moreover, fillets’ quality traits and proximate composition analyses performed did not show significant differences between the treatments. The fillets’ fatty acid content showed that higher inclusion of HI meal leads to higher saturated fatty acids content, while no significant difference in polyunsaturated fatty acids was observed among treatments. Results have a positive implication as dietary HI did not negatively affect the fatty acids composition or quality of sea bream fillets.

Modeling the Temperature Effect on the Growth of Uropathogenic Escherichia coli in Sous-Vide Chicken Breast.

Uropathogenic Escherichia coli (UPEC) is known to cause 65-75% of human urinary tract infection (UTI) cases. Poultry meat is a reservoir of UPEC, which is suspected to cause foodborne UTIs. In the present study, we aimed to determine the growth potential of UPEC in ready-to-eat chicken breasts prepared by sous-vide processing. Four reference strains isolated from the urine of UTI patients (Bioresource Collection and Research Center [BCRC] 10,675, 15,480, 15,483, and 17,383) were tested by polymerase chain reaction assay for related genes to identify their phylogenetic type and UPEC specificity. A cocktail of these UPEC strains was inoculated into sous-vide cooked chicken breast at 103-4 colony-forming unit (CFU)/g and stored at 4°C, 10°C, 15°C, 20°C, 30°C, and 40°C. Changes in the populations of UPEC during storage were analyzed by a one-step kinetic analysis method using the U.S. Department of Agriculture [USDA] Integrated Pathogen Modeling Program-Global Fit [IPMP-Global Fit]. The results showed that the combination of the no lag phase primary model and the Huang square-root secondary model fitted well with the growth curves to obtain the appropriate kinetic parameters. This combination for predicting UPEC growth kinetics was further validated using it to study additional growth curves at 25°C and 37°C, which showed that the root mean square error, bias factor, and accuracy factor were 0.49-0.59 (log CFU/g), 0.941-0.984, and 1.056-1.063, respectively. In conclusion, the models developed in this study are acceptable and can be used to predict the growth of UPEC in sous-vide chicken breast.

Transcriptome Analysis of Protocatechualdehyde against Listeria monocytogenes and Its Effect on Chicken Quality Characteristics.

The development of natural antimicrobial agents offers new strategies for food preservation due to the health hazards associated with the spoilage of meat products caused by microbial contamination. In this paper, the inhibitory mechanism of protocatechualdehyde (PCA) on Listeria monocytogenes was described, and its effect on the preservation of cooked chicken breast was evaluated. The results showed that the minimal inhibitory concentration (MIC) of PCA on L. monocytogenes was 0.625 mg/mL. Secondly, PCA destroyed the integrity of the L. monocytogenes cell membrane, which was manifested as a decrease in membrane hyperpolarization, intracellular ATP level, and intracellular pH value. Field emission gun scanning electron microscopy (FEG-SEM) observed a cell membrane rupture. Transcriptome analysis showed that PCA may inhibit cell growth by affecting amino acid, nucleotide metabolism, energy metabolism, and the cell membrane of L. monocytogenes. Additionally, it was discovered that PCA enhanced the color and texture of cooked chicken breast meat while decreasing the level of thiobarbituric acid active substance (TBARS). In conclusion, PCA as a natural antibacterial agent has a certain reference value in extending the shelf life of cooked chicken breast.

Physicochemical Properties of Chicken Breast and Thigh as Affected by Sous-Vide Cooking Conditions

Sous-vide is a cooking method used to improve the tenderness and juiciness of chicken breast. However, the comparative changes in meat quality attributes of sous-vide cooked chicken breast and thigh muscles are not fully understood. The objective of this study was to investigate the effects of sous-vide cooking conditions, based on collagen denaturation temperature of intramuscular connective tissue, on the physicochemical properties of chicken breasts and thighs. Chicken breast and thigh were cooked at four sous-vide cooking conditions (55 °C for 3/6 h and 65 °C for 3/6 h) and conventional cooking at 75 °C (core temperature of 71 °C) as control. No significant differences in pH and lightness were found between the sous-vide cooking conditions. Moisture content, cooking loss, protein solubility, shear force, myofibrillar fragmentation index, and lipid oxidation were affected by sous-vide cooking conditions (p &lt; 0.05). The decreased shear force and total collagen content of 65 °C sous-vide cooking treatment might be associated with collagen denaturation (p &lt; 0.05). Sous-vide cooking at 55 °C could decrease cooking loss, with higher moisture than sous-vide cooking at 65 °C (p &lt; 0.05). These tendencies on water-holding capacity and shear force at the two different temperatures were similarly observed for both chicken breast and thigh. Therefore, this study indicates that chicken breast and thigh are similarly affected by the sous-vide cooking conditions and suggests that a novel strategy to apply together two temperature ranges based on the thermal denaturation of intramuscular connective tissue would be required.

Formation of advanced glycation end products of chicken breast meat induced by freeze–thaw cycles and subsequent cooking

The impacts of freeze–thaw (F–T) cycles and cooking on the basic composition, protein and lipid oxidation, and advanced glycation end products (AGEs) of chicken breasts were studied. During F–T cycles, the moisture and protein contents of raw and cooked chicken breasts decreased, and protein and lipid oxidation occurred, increasing carbonyl and TBARS contents. Meanwhile, the contents of methylglyoxal, glyoxal, and hydroxymethylfurfural in raw meat increased by 2.27, 2.27, and 5 times, respectively, whereas glyoxal and hydroxymethylfurfural contents increased by 2.73 and 3 times, respectively, after cooking as F–T cycles increased. The formation of carboxymethyl lysine, pentosidine, and fluorescent AGEs in cooked samples was confirmed using an ELISA kit and fluorescent intensity. The study also revealed that AGEs contents of chicken meat were negatively correlated with moisture contents and positively correlated with carbonyl and TBARS levels. Therefore, F–T cycles and subsequent cooking promoted AGEs formation in cooked meat.

A multi-centre peptidomics investigation of food digesta: current state of the art in mass spectrometry analysis and data visualisation

Mass spectrometry has become the technique of choice for the assessment of a high variety of molecules in complex food matrices. It is best suited for monitoring the evolution of digestive processes in vivo and in vitro. However, considering the variety of equipment available in different laboratories and the diversity of sample preparation methods, instrumental settings for data acquisition, statistical evaluations, and interpretations of results, it is difficult to predict a priori the ideal parameters for optimal results. The present work addressed this uncertainty by executing an inter-laboratory study with samples collected during in vitro digestion and presenting an overview of the state-of-the-art mass spectrometry applications and analytical capabilities available for studying food digestion. Three representative high-protein foods – skim milk powder (SMP), cooked chicken breast and tofu – were digested according to the static INFOGEST protocol with sample collection at five different time points during gastric and intestinal digestion. Ten laboratories analysed all digesta with their in-house equipment and applying theirconventional workflow.The compiled results demonstrate in general, that soy proteins had a slower gastric digestion and the presence of longer peptide sequences in the intestinal phase compared to SMP or chicken proteins, suggesting a higher resistance to the digestion of soy proteins. Differences in results among the various laboratories were attributed more to the peptide selection criteria than to the individual analytical platforms. Overall, the combination of mass spectrometry techniques with suitable methodological and statistical approaches is adequate for contributing to the characterisation of the recently defined digestome.

Chicken meat quality raised in an integrated organic production system

This work aimed to evaluate and compare the meat quality of chicken raised by traditional confinement (CR) and integrated (FR) conditions. Eighty chickens (40 for each group) were slaughtered, and parts yield, chemical composition, and meat quality parameters were measured. There was no significant difference in parts yield. Protein content in the breast of the CR group was significantly (P &amp;lt; 0.05) higher than that of the FR group. The ash content of chicken thighs in the FR group was significantly higher than in the CR group. The cooked chicken breast from the FR group was significantly more tender than that from the CR group. The TBARS values of&amp;nbsp;breast and thigh meats on the sixth day after grinding&amp;nbsp;did not differ between CR and FR groups. However, the chickens raised in the FR had better appearance (color), fatty acids composition, and tenderness perspective than those in the CR system. All these results indicated that the plant-animal integrated system is a good alternative to the traditional confinement production system that can enhance farm diversity, land use efficiency, and sustainability of farm agriculture.

Effect of Thermal Treatments on Selected Minerals and Water Soluble Vitamins of Chicken Breast Meat

The study was conducted to ascertain the effect of thermal treatments on selected minerals (Ca, K, Mg, Na, P, Fe and Zn) and water soluble vitamins (B1, B2, B3, B6, B9, B12 and C) contents of chicken breast meat. Industrial skinless chicken breast meat samples were purchased, transported to Bioprocess laboratory in cool conditions, frozen and sliced into dimensions and thawed. The samples were cooked by air frying (AF), baking (BK), deep fat frying (DF) and grilling (GR) at 170, 180 and 1900C for 0, 4, 8 and 12 min for minerals and 0, 8 and 16 min for vitamins. Thereafter, cooked and raw samples were wet acid digested overnight and 5 h digested on a block digester on slowly increased temperature to 1200C, cooled and deionized. The mineral elements were analysed by Optima 4300DV inductivity coupled plasma optical emission spectrometry (ICP-OES) and inductivity coupled plasma mass spectrometry (ICP-MS). These mineral elements were extrapolated through a calibration curve between intensity and concentration, while the vitamins were ascertained by measurement of absorbance of filtrates of the samples dissolved in their respective solvents in the Spectrophotometer against their blank samples at different wavelengths. The results showed that cooking methods decreased significantly (p &lt; 0.05) the mineral elements with an exception of Zn cooked by grilling (GR) that increased by 19.92% and Mg that increased in the cooking methods. The ascending percentage reduction of minerals in cooked chicken breast were Zn, P, K, Fe, Na and Ca. Samples cooked by DF had significantly (p &lt; 0.05) higher percentage reduction of 45.06% in Ca, 27.74% in Na and 18.85% in Zn and higher percentage increases of 14.96% in Mg contents than other methods. Also samples cooked by DF had higher percentage reductions of 55.10%, 37.93%, 37.11%, 34.44% and 30.99% in vitamins B1, C, B2, B9 and B6 Whereas higher percentage reductions of 41.67% and 37.84 % in vitamins B12 and B3 occurred in baking (Bk) and grilling (GR) treated samples. Cooking at 1900C had higher percent reduction in the Ca, Na, Fe, K, P and Zn as well as B1, B12, B2, C, B3, B9 and B6. Cooking methods, temperatures and times decreased significantly (p &lt; 0.05) vitamins and minerals contents of chicken breast meat with an exception of Mg. Samples cooked at 1700C for 4 min and 1700C for 8 min had lower losses of minerals and vitamins compared to similar samples cooked at 1800C and 1900C. The AF cooking method had the least percent reduction of 22.50% than other cooking methods BK (26.88%), DF (36.04%) and GR (30.69%) in vitamin contents.

Sous-vide cooking as a practical strategy to improve quality attributes and shelf stability of reduced-salt chicken breast ham

The objective of this study was to evaluate the general quality attributes and shelf stability of reduced-salt and sous-vide cooked chicken breast hams during 4 weeks of refrigerated storage (4°C). Four treatment groups of chicken breast ham were prepared using a 2 (salt level, 1.5% NaCl (regular) and 0.75% (reduced))×2 (cooking method, conventional and sous-vide) factorial arrangement. Based on each chicken breast weight, 20% NaCl solution was injected. Conventional cooking was done at 80°C until the core temperature reached 71°C, whereas sous-vide cooking was conducted at 60°C for 2 h. Sous-vide cooking could decrease cooking loss and shear force of reduced-salt chicken breast ham (P < 0.05). As a result, sensory scores for juiciness and tenderness of reduced-salt and sous-vide cooked chicken breast ham were similar to those of regular-salt and conventionally cooked chicken breast hams (P > 0.05). No adverse impacts on lipid oxidation and microbial safety were found in reduced-salt and sous-vide cooked chicken breast ham during 4 wk of refrigerated storage. Therefore, this study suggests that sous-vide cooking could be a practical thermal process for improving the water-holding capacity and texture of chicken breast ham without adverse impacts on shelf stability. Further studies on the combined application of sous-vide cooking with salt replacers would be warranted to improve the sensorial acceptance of saltiness of sous-vide cooked low-salt meat products.

Effect of Cooking on Physicochemical and Microstructural Properties of Chicken Breast Meat

The effect of cooking on pH, juiciness, instrumental colour and microstructural properties of chicken breast meat was investigated. Industrial skinless chicken breast meat samples were purchased, frozen and sliced into dimensions , thawed and cooked by air frying (AF), baking (BK), deep fat frying (DF) and grilling (GR) at 170, 180 and 1900C for 0, 4, 8, 12 and 16 min. The pH value of the cooked samples increased from 6.05 to 6.25. Cooking methods, temperatures and times each resulted to increase in pH. The results of objective sensory instrumental analyses showed that cooking decreased significantly (p &lt; 0.05) juiciness of cooked chicken breast meat. Samples cooked by BK had the highest juiciness value of 24.91%, while DF cooked samples had the least value of 13.89%.The instrumental analyses increased L*, a*, b* values and browning index. The temperature and time of cooking showed similar effects on juiciness and instrumental colour. Short cooking time (8 min) and 1700C resulted in higher juiciness and best appetizing appearance to the consumers. The microstructure studies showed that raw chicken breast meat had an intact muscle fibres and bundles, but cooking caused disintegration of muscle fibres, perimysial – collagen shrinkage and it resulted to drier samples with big cracks/ voids and big surface damages, particularly in AF, BK and GR cooked products at 1900C for 8 min.

Application of antimicrobial packaging based on modified calcium carbonate and EOs for RTE meat products

Highly porous modified calcium carbonate (MCC) powder has been successfully integrated into packaging material as a coating and the coated packaging films were loaded with 5, 10 or 30 wt % thyme and rosemary essential oil (EO). Resulting MCC labels were applied as labels and showed antimicrobial activities against L. innocua in in vitro test. After 6 days MCC labels with 10 and 30 wt % thyme EO showed significant reductions in in vitro tests (2.9 and > 8.5 log CFU/filter). When MCC labels with rosemary EO were used, only 30 wt % loading showed a significant reduction (1.6 log CFU/filter). Subsequently, the antimicrobial activity of MCC labels with 30 wt % EOs against L. innocua on ready to eat meat product were studied under normal atmosphere and modified atmosphere (MA). Use of MCC labels with 30 wt % thyme EO loading combined with MA packaging showed a significant microbial reduction of 1.2 log CFU/g on cooked ham after 21 days (compared to untreated MCC labels packaged under MA). On the other hand, use of MCC labels loaded with 30 wt % rosemary EO (with MA) showed significant reductions of L. innocua on sliced cooked chicken breast (2.6 log CFU/g) as well as cooked ham (1.3 log CFU/g).

Carcass and meat quality of broiler chickens reared on herb residues

This study was conducted to determine the effects of herb residues on carcass and meat quality in broilers. A total of 160 chicks were divided into four groups, each with four replicates of 10 chicks; the chicks were provided ad libitum access to a control diet or the same diet supplemented with Zingiber cassumunar, Kaempferia galangal, or Curcuma aromatica residues at 0.3% feed. At 42 days of age, 20 chicks from each group were slaughtered, and the carcass and meat quality were determined. All exper-imental groups demonstrated lower abdominal fat weight, and the K. galangal group had a significantly higher total visceral organ weight than that of the control group (P&lt;0.05). The experimental groups demonstrated improved color of the breast muscle, breast fillet muscle, skin, and abdominal fat (P&lt;0.05). The shear force value of the breast muscle increased in the K. galangal group, whereas that of the thigh muscle increased in all experimental groups (P&lt; 0.05). The highest overall acceptability of raw and cooked chicken breast meat was produced by 0.3% C. aromatica residue supplementation (P&lt;0.05). These finding suggest that the inclusion of 0.3% C. aromatica residue in the diets resulted in improved overall acceptability of breast meat without negatively affecting dressing percentage.

Indirect and mixed‐mode solar drying and its effect on physicochemical properties of raw and cooked chicken breast meat

Chicken meat is the most consumed worldwide protein but, unfortunately, is very perishable. This study analyzes two solar drying methods: mixed-mode solar drying (MM-SD) and indirect-mode solar drying (IM-SD). Moreover, it examines its influence on drying kinetics and physicochemical properties of cooked and raw chicken breast meat. In addition, water effective diffusivity D eff $$ \left({D}_{\mathrm{eff}}\right) $$ modeling was studied. The MM-SD reaches equilibrium moisture faster than the IM-SD. In both technologies, drying kinetics show a predominantly period of decreasing drying rate, suggesting that diffusion was the primary physical mechanism governing moisture transport in chicken breast meat. The D eff $$ {D}_{\mathrm{eff}} $$ is slightly higher with cooked chicken than with raw chicken for both technologies. In addition, the cooked meat samples observed a high color difference in cooked chicken breast meat and higher fats and protein content values. According to the results, we could conclude that solar drying of chicken meat is feasible for obtaining quality products. Novelty impact statement Both low-cost solar technologies analyzed can provide dry chicken of adequate quality, preserving this valuable food for its nutritional properties and low cost. In addition, thin-bed and effective diffusivity modeling offer essential information for larger-scale production, helping sustainable development objectives. The cooked samples presented a minor difference in color and showed a higher percentage of protein and fat at the end of the process.

Structural characteristics of high-moisture extrudates with oil-in-water emulsions

There is an increasing demand to produce high-quality plant-based meat analogs rich in tenderness and juiciness, presenting a significant challenge in creating oil-containing fibrous structures. A novel oil addition approach was developed by adding oil-in-water (O/W) emulsion during high-moisture extrusion processing. The current study investigated the effect of oil content using O/W emulsion on high-moisture extrudates prepared from soy protein isolate (SPI) and wheat gluten (WG) (SPI-WG). The oil content in fibrous SPI-WG extrudate could be up to 8.0% using O/W emulsion, whereas only 4.0% was possible by direct oil addition. O/W emulsion addition significantly decreased the extrusion response parameters of die pressure and specific mechanical energy. Confocal laser scanning microscopy indicated that oil was distributed to small droplets (0.5–15.0 μm) within the protein matrix in SPI-WG extrudates. Oil-free SPI-WG extrudate presented a close-meshed protein network. In contrast, higher oil contents led to more porous structures in SPI-WG extrudates with 3.0–8.0% oil. O/W emulsion addition reduced the rubber-like texture and rheological properties of SPI-WG extrudates, which improved the textural attributes (e.g., chewiness), making them similar to those of cooked chicken breast. In addition, the mobility of water and oil protons increased with increasing oil contents in SPI-WG extrudates, indicating the water and oil binding properties were reduced. Overall, this study demonstrated the potential of using O/W emulsions to promote fibrous structures of high-moisture extrudates.

Effects of oxidation and precursors (lysine, glyoxal and Schiff base) on the formation of Nε-carboxymethyl-lysine in aged, stored and thermally treated chicken meat

Advanced glycation end products (AGEs) might pose health risks, and processing and storage could accelerate the generation of AGEs in meat. However, limited few reports indicated the changes of AGEs contents in meat during storage. In this study, the aim is to investigate the oxidation and precursors and their roles in the formation of Nε-carboxymethyl-lysine (CML) in raw and cooked chicken meat after post-mortem ageing and storage. As post-mortem ageing and storage time increased, the CML content in cooked chicken breast significantly increased from 1.81 mg/kg to 2.00 mg/kg during 0−6 h, and then decreased from 2.00 mg/kg to 1.80 mg/kg during 6 h−1 day, finally increased again during 1−7 days, while the CML contents of raw and cooked leg significantly and continuously increased from 1.78 mg/kg to 2.08 mg/kg. Furthermore, CML was extremely positively correlated with fat oxidation (R2 = 0.793, P < 0.01), protein oxidation (R2 = 0.917, P < 0.01) and glyoxal (R2 = 0.678, P < 0.05), and was negatively correlated with lysine (R2 = 0.536, P < 0.05). No significant correlation was observed between the Schiff base and CML.