Influence of meat exudates on the quality characteristics of fresh and freeze-thawed pork

Effect of constant-current pulsed electric field thawing on proteins and water-holding capacity of frozen porcine longissimus muscle

This study explored the effect of constant-current pulsed electric field thawing (CC-T) on the proteins and water-holding capacity of pork. Fresh meat (FM), and frozen meat after constant-voltage thawing (CV-T), air thawing (AT) and water immersion thawing (WT) were considered as controls. The results indicated that CC-T had a higher thawing rate than conventional thawing during ice-crystal melting stage (-5 to -1 °C). It also showed a lower water migration and thawing loss, maintaining pH and shear force closer to FM. Meanwhile, CC-T decreased myoglobin oxidation, resulting in a favorable surface color. The results of protein solubility, differential scanning calorimetry, total sulfhydryl, carbonyl and surface hydrophobicity demonstrated that CC-T reduced myofibrillar protein oxidative denaturation by suppressing the formation of disulfide and carbonyl bonds, thus enhancing solubility and thermal stability. Additionally, microstructural observation found that CC-T maintained a relatively intact muscle fiber structure by reducing muscle damage and myosin filament denaturation.

A non-destructive predictive model for estimating the freshness/spoilage of packaged chicken meat using changes in drip metabolites

This study investigates the possibility of utilizing drip as a non-destructive method for assessing the freshness and spoilage of chicken meat. The quality parameters [pH, volatile base nitrogen (VBN), and total aerobic bacterial counts (TAB)] of chicken meat were evaluated over a 13-day storage period in vacuum packaging at 4 °C. Simultaneously, the metabolites in the chicken meat and its drip were measured by nuclear magnetic resonance. Correlation (Pearson's and Spearman's rank) and pathway analyses were conducted to select the metabolites for model training. Binary logistic regression (model 1 and model 2) and multiple linear regression models (model 3-1 and model 3-2) were trained using selected metabolites, and their performance was evaluated using receiver operating characteristic (ROC) curves. As a result, the chicken meat was spoiled after 7 days of storage, exceeding 20 mg/100 g VBN and 5.7 log CFU/g TAB. The correlation analysis identified one organic acid, eight free amino acids, and five nucleic acids as highly correlated with chicken meat and its drip during storage. Pathway analysis revealed tyrosine and purine metabolism as metabolic pathways highly correlated with spoilage. Based on these findings, specific metabolites were selected for model training: ATP, glutamine, hypoxanthine, IMP, tyrosine, and tyramine. To predict the freshness and spoilage of chicken meat, model 1, trained using tyramine, ATP, tyrosine, and IMP from chicken meat, achieved a 99.9 % accuracy and had an ROC value of 0.884 when validated using drip metabolites. This model 1 was improved by training with tyramine and IMP from both chicken meat and its drip (model 2), which increased the ROC value for drip metabolites from 0.884 to 0.997. Finally, selected two metabolites (tyramine and IMP) can predict TAB and VBN quantitatively through models 3-1 and 3-2, respectively. Therefore, the model developed using metabolic changes in drip demonstrated the capability to non-destructively predict the freshness and spoilage of chicken meat at 4 °C. To make generic predictions, it is necessary to expand the model's applicability to various conditions, such as different temperatures, and validate its performance across multiple chicken batches.

Dietary Crude Protein and Lysine Levels Affect Meat Quality and Myofiber Characteristic of Slow-Growing Chicken

This study aimed to investigate the effects of dietary crude protein (CP) and lysine levels on growth performance, slaughter performance, meat quality, and myofiber characteristics of slow-growing chicken. A 3 × 3 factorial experiment was arranged, and the chickens were fed with 3 levels of dietary CP (16.0%, 17.0%, 18.0%) and 3 levels of dietary lysine (0.69%, 0.84%, 0.99%). A total of 540 8-week-old Beijing-You Chicken (BYC) female growing chickens were randomly allocated to 9 groups, 5 replicates per group, and 12 chickens per replicate. The birds were randomly allocated to one of the 9 experimental diets. Growth performance, slaughter performance, meat quality, and myofiber characteristics were determined at 16 weeks of age. The results showed that dietary CP level and the interaction of dietary CP and lysine levels affected average feed intake (AFI) (p < 0.05). The AFI in the 16.0% CP and 17.0% CP groups was higher than in the 18.0% CP group (p < 0.05). Dietary CP levels significantly affected body weight gain (BWG) (p < 0.05) at 9 to 16 weeks. The 18.0% CP group had the highest BWG (93.99 g). Dietary CP levels affected the percentage of leg muscle yield, and the percentage of leg muscle yield of the 16.0% CP group was significantly lower than that in the other two groups (p < 0.05). Dietary CP and lysine levels alone and their interactions did not affect pH24h, drip loss, and cooking loss of breast muscle (p > 0.05). The shear force of the 18.0% CP group (29.55 N) was higher than that in the other two groups (p < 0.01). Dietary CP level affected myofiber characteristic (p < 0.01), with the lowest myofiber density (846.35 p·mm-2) and the largest myofiber diameter (30.92 μm) at 18.0% CP level. Dietary lysine level affected myofiber diameter, endomysium thickness, perimysium thickness (p < 0.01), with the largest myofiber diameter (29.29 μm) obtained at 0.84% lysine level, the largest endomysium thickness (4.58 μm) at 0.69% lysine level, and the largest perimysium thickness (9.26 μm) at 0.99% lysine level. Myofiber density was negatively correlated with myofiber diameter and endomysium thickness (R = -0.883, R = -0.523, p < 0.01); perimysium thickness had a significant negative correlation with shear force (R = -0.682, p < 0.05). Therefore, reducing dietary CP level and adding appropriate lysine can reduce myofiber diameter and increase perimysium thickness, reducing shear force and improving meat tenderness. A high lysine level (0.99%) in the low-CP (16.0%) diet can improve meat tenderness by regulating the myofiber characteristic without affecting production performance.

Assessing Individual Muscle Characteristics to Enhance Frozen-Thawed Meat Quality

This study assessed previous research aimed at mitigating the adverse effects of freeze-thawing on meat quality. Specifically, it focuses on assessing the physicochemical alterations in meat resulting from freezing, freeze-thawing, or technologies to minimize these alterations. Recent studies have focused on conventional freeze-thaw technology applicable across various livestock species and muscle types. However, recent research has indicated the necessity for developing freeze-thaw technology considering the unique characteristics of individual muscles. In this review, we summarize previous studies that have compared alterations in the physicochemical properties of primary muscles owing to freezing or freeze-thawing. Despite the introduction of various technologies to significantly reduce the adverse effects on meat quality resulting from freeze-thawing, it is essential to consider the unique characteristics (proximate composition, pH, and muscle fiber characteristics) of individual muscles or cuts to develop enhanced the freeze-thaw processing technology.

Spray-chilling system in the initial cooling process of swine half carcasses

This research was carried out with the objective of evaluating the effects of using a chilling water sprinkler system during the cooling process of swine carcasses on the quantitative and qualitative parameters of carcass and meat. A total of 220 swine carcasses were divided in a completely randomized experiment and two treatments: (1) CONTROL, no water spraying; (2) SPRAY, with water spraying during cooling. Surface and internal temperature of carcasses throughout the cooling process, initial and final pH, and microbiological analyses of carcass surface were evaluated. Samples of the Longissimus lumborum (LL) were collected for analysis of color, cooking loss (CL), shear force (SF), and drip loss (DL). Data were submitted to analysis of variance through the SAS MIXED procedure adopting the most adequate model with treatments as fixed effects and pertinent random effects for each data set. The use of spray-chilling in the initial cooling process accelerates the surface and internal temperature decrease of swine carcasses, which may be a viable technological resource in swine industry.

Degradation and evaluation of myofibril proteins induced by endogenous protease in aquatic products during storage: a review

Myofibril proteins degradation constitutes an important factor in quality deterioration, procedural activation or inhibition of endogenous protease potential regulates autolytic proteolysis-induced softening of post mortem fish muscle. Based on the brief introduction of myofibril proteins degradation in fish skeletal muscle, a detailed description of the main myofibril degradation properties and the distinct role played by endogenous proteases were proposed, which reflects the limitations and challenges of the current research on myofibril hydrolysis mechanisms based on the varied surrounding conditions. In addition, the latest researches on the evaluation method of myofibril proteins degradation were comprehensively reviewed. The potential use of label-free proteomics combined with bioinformatics was also emphasized and has become an important means to in-depth understand protein degradation mechanism.

Effect of freezing raw meat on the physicochemical characteristics of beef jerky

The effect of freezing raw meat on the quality characteristics of beef jerky was evaluated in the present study. Jerky was made using different types of raw beef (fresh, frozen, and frozen-thawed) with different curing times (6 h and 12 h). Frozen-thawed beef had a lower moisture content than fresh or frozen beef due to higher exudate loss (P < 0.05). Jerky made using frozen and frozen-thawed beef showed lower drying yield and higher shear force than jerky prepared using fresh beef (P < 0.05). Freezing raw beef decreased the fat content and increased the redness, yellowness, chroma, and hue values of jerky (P < 0.05). The microstructure of beef jerky was showed to increase the deformation and contraction of muscle fibers due to freezing. Longer curing times increased the moisture content of jerky made using frozen meat (P < 0.05). Jerky made using frozen or frozen-thawed meat was tough due to excessive fat and moisture loss.

Using 2D qNMR analysis to distinguish between frozen and frozen/thawed chicken meat and evaluate freshness

We identified key metabolites reflecting microbial spoilage and differentiated unfrozen meat from frozen/thawed (FT) using 2D qNMR analysis. Unfrozen and FT chicken breasts were prepared, individually aerobically packaged, and stored for 16 days at 2 °C. Only volatile basic nitrogen (VBN) was significantly changed after 6 log CFU/g of total aerobic bacteria (p < 0.05). Extended storage resulted in an increase in organic acids, free amino acids, biogenic amines, and hypoxanthine and a decrease in N,N-dimethylglycine, inosine 5'-monophosphate, and proline. Acetic acid demonstrated the highest correlation with VBN (r = 0.97). Unfrozen and FT breast meat can be differentiated by uniform concentration of carnosine, β-alanine, and histidine levels, consistent changes in nucleotides by storage time, and changes in microbial metabolism patterns that are reflected by some free amino acids. Thus, NMR-based metabolomics can be used to evaluate chicken breast meat freshness and distinguish between unfrozen and FT meat.

Desmin as molecular chaperone for myofibrillar degradation during freeze-thaw cycles

This study investigated the relationship of secondary protein structures with textural attributes of chicken breast subjected to 6 freeze (-20 °C) thaw (4 °C for 12 h) cycles. 2DE identified 78 distinct protein spots. Moreover, WB indicated a remarkable increase in the degree of desmin degradation during multiple freeze-thaw (MFT). In addition, the TEM micrographs revealed that MFT remarkably increased the spacing between the muscle fibers, especially from cycles 3 to 5, slightly decreased H-zone, but a remarkable shrinkage of Z-lines, as well as degradation of myofibril structures (Z-line, I-bands, and M-lines). DSC showed shifts in first and second endothermic transition peaks during the 3rd and 5th cycles. Viscoelastic graphs revealed a cycle-dependent decrease in gel-forming ability (G') during MFT. Finally, the MFT chicken breast samples exhibited significantly decreased shear force in a cycle-dependent manner. This study highlighted the critical role of desmin in regulating myofibrillar degradation through various routes and mechanisms.

Prevalence of gross lesions and handling practices in pigs and their association with pork quality, Kiambu, Kenya

Pre-slaughter handling of pigs has been documented to affect the quality of meat though no studies have investigated this relationship in the Kenyan context. This study aimed to determine the prevalence of gross lesions and practices related to sub-optimal welfare in pigs presented for slaughter while analyzing the relationship between occurrence of these lesions and meat quality. A cross-sectional study was conducted at a medium scale, non-integrated pig abattoir supplying to the Nairobi market, with a capacity to slaughter approximately 40 pigs a day. Data on welfare-associated lesions and handling practices were obtained from 529 pig carcasses and traders respectively. 387 pork samples were collected, and their quality evaluated by measuring their pH, meat color and drip loss. These three parameters were used to classify pork into four recognized categories namely: Red, Firm, Non-exudative (RFN), Pale Soft Exudative (PSE), Dark Firm Dry (DFD) and Red Soft Exudative (RSE). Almost all pigs were inefficiently stunned as evidenced by the presence of consciousness post-stunning. The majority of pigs (82.97%) having one or more welfare-associated gross lesions. Other animal welfare malpractices observed were high loading density and inadequate rest periods between transport and slaughter. A quarter of the pork samples were of sub-optimal quality including: RSE (11.36%), PSE (2.58%) and DFD (2.58%). Multinomial logistic regression revealed that pork originating from pigs transported at a high loading density had increased odds of being classified as DFD (OR 13.41, 95% CI 2.59–69.46). The findings indicate the need to educate stakeholders in the pork value chains on improved pig handling before and during slaughter to enhance pig welfare pre-slaughter and pork quality post-slaughter. Animal welfare legislation enforcement and implementation was observed to be insufficient. There is a need to educate key stakeholders on its importance of being put into practice both from economic and welfare perspectives.

Modification of the vacuum-steam thawing method of meat by using the initial stage of sublimation dehydration

Vacuum-steam thawing is one of the methods used for defrosting food, realized in the atmosphere of water vapour under the conditions of reduced pressure. The water vapour formed in vacuum with the temperature of 20 °C fills the defrosting chamber and condenses on the surface of the defrosted product. The condensated steam has the role of thermal energy carried enabling product thawing. The study presents a modification of this method, introducing an additional stage of sublimation-dehydration vacuum steam thawing (SRVST). The study was carried out for different variants of initial sublimation degree (in the range from 0 to 15%) of a slice of pork loin (m. longissimus lumborum) assessing the final effect of the process of vacuum-steam thawing. Thawing kinetics was determined with the SRVST method, degree of sample defrosting and level of their rehydration. Based on the results it was demonstrated that the use of 12% sublimation dehydration of a meat sample enables its complete defrosting (reaching the temperature not exceeding the cryoscopic temperature).

Effects of pulsed electric field-assisted thawing on the characteristics and quality of Pekin duck meat

We determined the effect of pulsed electric field (PEF)-assisted thawing on the texture and muscle tissue of Pekin duck meat. The results indicated that 1-4 kV/cm of PEF shortened the thawing time by 20%-50%. Furthermore, 1-3 kV/cm of PEF-assisted thawing reduced the effect of thawing on meat quality, decreased thawing loss by 28% and protein loss by 19%, and maintained meat quality similar to that of fresh meat. Using low-field nuclear magnetic resonance, we confirmed that PEF stabilized the water retention capacity of muscle tissues during thawing. Microstructure and secondary structure analyses revealed that PEF accelerated the melting of ice crystals, reducing the damage caused by ice crystals by 70% and maintaining the stability of the α-helix and β-sheet. These results revealed the potential of PEF-assisted methods for use in thawing meat.

Recovery of emulsifying and gelling protein from waste chicken exudate by using a sustainable pH-shifting treatment

The inevitably generated chicken exudate was usually unconsciously discarded, leading to protein waste and environmental pollution. The study is performed to reveal the loss and constitute of different sourced exudate (purge exudate/defrozen exudate, PE/DE), investigate the efficiency of various pH-shifting strategies (Method I: NaOH-HCl, Method II: Ca(OH)₂-Critric acid, and Method III: Ca(OH)₂-Glucono δ-lactone) in recovering selected exudate, and evaluate the functionality of these recovered protein isolates. Accordingly, PE and DE shared greatly similar (P > 0.05) lipid and ash content. Despite sarcoplasmic protein, there are a small amount of functional myofibrillar protein in the exudate samples. During extraction, Method III had higher recovery yield (85.5%) than other two groups, but the isolates contained higher level of moisture. The protein isolates treated with Method II exhibited highest emulsion ability, while the Method III treated group obtained best gelation properties. Overall, pH-shifting could recover functional protein from chicken exudate for industrial application.

Physicochemical properties of reduced-salt cured pork loin as affected by different freezing temperature and storage periods

Objective

The objective of this study was to evaluate functional properties of reduced-salt pork meat products made of pre-rigor pork loin treated by different freezing temperatures (−30°C and −70°C) during storage.

Methods

Pre-rigor cured pork loin with 1.0% added salt was compared to post-rigor muscle added with 1.5% salt for pH, color (L*, a*, b*), cooking loss (CL), expressible moisture, warner-Bratzler shear value, thiobarbituric acid reactive substances (TBARS), and volatile basic nitrogen (VBN).

Results

Pre-rigor cured pork loins had higher pH and temperature than post-rigor ones as raw meat (p<0.05). pH values were higher for pre-rigor pork loins than those of post-rigor pork loins (p<0.05). Color values did not different among treatments (p>0.05). No color differences were observed during storage period after cooking (p>0.05). The CL (%) of pre-rigor cured pork loins was the lowest when frozen at −70°C. The TBARS and VBN increased from 8 weeks of storage (p<0.05), but no further changed thereafter (p>0.05). Pre-rigor cured pork loins added with 1.0% salt showed similar characteristics to post-rigor pork loins added with 1.5% salt.

Conclusion

Cured pork loins could be produced using pre-rigor muscle added with 1/3 of the original salt level (1.5%) and could be stored for up to 4 wks of frozen storage, regardless of a frozen temperature of −30°C or −70°C without detrimental effects.

Frozen/thawed meat quality associated with muscle fiber characteristics of porcine longissimus thoracis et lumborum, psoas major, semimembranosus, and semitendinosus muscles

To evaluate the relationship between muscle fiber characteristics and the quality of frozen/thawed pork meat, four different muscles, M. longissimus thoracis et lumborum (LTL), M. psoas major (PM), M. semimembranosus (SM), and M. semitendinosus (ST), were analyzed from twenty carcasses. Meat color values (lightness, redness, yellowness, chroma, and hue) changed due to freezing/thawing in LTL, which showed larger IIAX, IIX, and IIXB fibers than found in SM (P < 0.05). SM and ST showed a significant decrease in purge loss and an increase in shear force caused by freezing/thawing (P < 0.05). Compared with LTL, SM contains more type IIXB muscle fibers and ST had larger muscle fibers I and IIA (P < 0.05). PM was the most stable of all muscles, since only its yellowness and chroma were affected by freezing/thawing (P < 0.05). These results suggest that pork muscle fiber characteristics of individual cuts must be considered to avoid quality deterioration during frozen storage.

Gestational nutrient restriction under extensive grazing conditions: Effects on muscle characteristics and meat quality in heavy lambs

We evaluated maternal undernutrition effects induced by a lower natural pasture allowance (gestation days 30-143) on histological-biochemical and meat traits in muscles Semitendinosus, cranial Gluteobiceps and Supraspinatus from 200-day old male and female lambs. Maternal undernutrition increased oxidative and reduced glycolytic fibers in all muscles (P ≤ 0.01). Maternal undernutrition reduced the diameter of glycolytic fibers in the cranial Gluteobiceps of exclusively female lambs (P = 0.05) and reduced the diameter of oxidative fibers in the Supraspinatus of exclusively male lambs (P = 0.02). Maternal undernutrition increased lipid content in the Supraspinatus of females (P = 0.001), reduced lactate content (P = 0.03) and WB shear force (P = 0.02) in the Semitendinosus of females, and increased cooking losses in the Semitendinosus of males (P = 0.0069). In conclusion, gestational nutrient restriction induced fetal programming effects on muscle characteristics of lambs. Moreover, our study demonstrates that maternal undernutrition influences muscle and meat characteristics in a sex and muscle-dependent way.

Utilizing Pork Exudate Metabolomics to Reveal the Impact of Aging on Meat Quality

This study was performed to assess the changes in meat quality and metabolome profiles of meat exudate during postmortem aging. At 24 h postmortem, longissimus lumborum muscles were collected from 10 pork carcasses, cut into three sections, and randomly assigned to three aging period groups (2, 9, and 16 d). Meat quality and chemical analyses, along with the metabolomics of meat exudates using ultra-high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer (UHPLC-QTOF-MS) platform, were conducted. Results indicated a declined (p < 0.05) display color stability, and increased (p < 0.05) purge loss, meat tenderness, and lipid oxidation as aging extended. The principal component analysis and hierarchical clustering analysis exhibited distinct clusters of the exudate metabolome of each aging treatment. A total of 39 significantly changed features were tentatively identified via matching them to METLIN database according to their MS/MS information. Some of those features are associated with adenosine triphosphate metabolism (creatine and hypoxanthine), antioxidation (oxidized glutathione and carnosine), and proteolysis (dipeptides and tripeptides). The findings provide valuable information that reflects the meat quality’s attributes and could be used as a source of potential biomarkers for predicting aging times and meat quality changes.

Effect of Freeze-Thaw Cycles on the Oxidation of Protein and Fat and Its Relationship with the Formation of Heterocyclic Aromatic Amines and Advanced Glycation End Products in Raw Meat

The aim of this research was to investigate the effect of the number of freeze–thaw cycles (0, 1, 3, 5, and 7) on porcine longissimus protein and lipid oxidation, as well as changes in heterocyclic aromatic amines (HAAs) and advanced glycation end products (AGEs) and their precursors. We analyzed the relationship among HAAs, AGEs, oxidation, and precursors and found the following results after seven freeze–thaw cycles. The HAAs, Norharman and Harman, were 20.33% and 16.67% higher, respectively. The AGEs, Nε-carboxyethyllysine (CEL) and Nε-carboxymethyllysine (CML), were 11.81% and 14.02% higher, respectively. Glucose, creatine, and creatinine were reduced by 33.92%, 5.93%, and 1.12%, respectively after seven freeze–thaw cycles. Norharman was significantly correlated with thiobarbituric acid reactive substances (TBARS; r² = 0.910) and glucose (r² = −0.914). Harman was significantly correlated to TBARS (r² = 0.951), carbonyl (r² = 0.990), and glucose (r² = −0.920). CEL was correlated to TBARS (r² = 0.992) and carbonyl (r² = 0.933). These changes suggest that oxidation and the Maillard reaction during freeze–thaw cycles promote HAA and AGE production in raw pork.

Non-destructive Near Infrared Spectroscopy for the labelling of frozen Iberian pork loins

Iberian pigs fed on acorns and pasture were slaughtered from January until March of 2018 and 2019. The meat from those Iberian pigs is a seasonal food that only can be found fresh, at the marketplace, during a limit period of the year. Selling frozen-thawed meat is a legal practice, but consumers must be informed about it on the product label. However, to declare as fresh meat, meat previously frozen, is one of the most frequent meat frauds. The present study compares the performance of two rather different Near Infrared Spectroscopy instruments, based on Fourier Transform and Linear Variable Filter technologies, for the in-situ detection of fresh and frozen-thawed acorns-fed Iberian pig loins using Partial Least Discriminant Analysis (PLS-DA). The performance of the models developed for both instruments offered a very high discriminant ability. Furthermore, the models showed consistent results and interpretation when were evaluated with several scalars and graphical methods.

Pork Loin Chop Quality and Muscle Fiber Characteristics as Affected by the Direction of Cut

In this study, the relationship between muscle fiber characteristics and meat quality of pork loin chops prepared using different directions of cut (vertical to the muscle length, M-Vertical; vertical or parallel to the muscle fiber orientation, F-Vertical or F-Parallel) was evaluated under different storage conditions (fresh, cold storage/aged, and freeze–thawed). Among the three groups, F-parallel displayed considerably larger size of muscle fibers, regardless of their type. This group also displayed an increase in discoloration in aged chops and a decrease in purge loss and tenderness than in other cut groups (p < 0.05). Freeze–thawing accelerated deterioration of meat quality, especially water-holding capacity and tenderness in all groups (p < 0.05), but was most prominent in F-Parallel. Therefore, to avoid excessive deterioration of fresh, aged, or frozen/thawed pork loin chops, it is important to consider the direction in which the chop is cut with respect to the muscle fiber orientation.

Quality Traits of Dry-Cured Loins from Iberian Pigs Reared in Montanera System as Affected by Pre-Freezing Cure

Iberian dry-cured loins from pigs fattened in Montanera are usually subjected to seasonal production, which could be overcome through freezing the loin before the curing process. Hence, three homogeneous batches (n = 15 per batch) were established to evaluate the effect of different pre-freezing cure (−20 ± 2 °C) times (three and six months) of raw material on main quality characteristics of dry-cured loins in comparison to those elaborated from unfrozen meat. All samples were subjected to similar seasoning and same curing length to obtain dry-cured loins. Results showed a decrease in lightness, redness, chrome and hue values, polyunsaturated fatty acids (PUFA), higher oxidative phenomena, and changes in rheological properties in fresh loins on account on freezing (p ≤ 0.05). Some quality parameters of dry-cured loins were affected by freezing, weight loss, and hardness being higher as well as salt content being lower. PUFA and Warner–Braztler Shear Force (p ≤ 0.05) also showed higher values in dry-cured loins from frozen meat than those elaborated from unfrozen counterparts.

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.

Physicochemical and Biochemical Properties of Ground Pork Formulated with Addition of Prunus cerasus (cv Montmorency) Extract and Subjected to Freezing Storage

Broad research interest is observed over last decade, toward searching for a new natural antioxidants, which could be applied in food industry. Especially attractive seems to be those rich in polyphenols, such as cherry. Thus, presented study determine the effect of cherry extract (equivalent of 20 mg and 40 mg GAE kg−1) on physicochemical properties of ground pork frozen for 80 days. Samples were analyzed for color, color change, color attractiveness, myoglobin oxidation, fat oxidation, fatty acids profile, cooking loss, texture profile. The positive effect of cherry extract was observed for fat oxidation but cooking loss was higher in samples with extract addition. Color, color change, color attractiveness, myoglobin oxidation or fatty acids profile did not differ between groups.

Process optimization and kinetics of deep fat frying conditions of sausage processed from goat meat using response surface methodology

This study investigated the effects and optimization of cooking time (30, 45, 60 min), frying temperature (150, 170, 190°C) and time (3, 6, 9 min) on the quality (moisture content, moisture loss, fat and protein content, color), textural, and sensory characteristics of deep fat fried goat meat sausage by response surface methodology (RSM) using a three-level Box-Behnken design. The kinetic of moisture loss and fat absorption were also determined using first-order equation. The goat meat was precooked and fried using a 2.5-L electric deep fryer with a temperature control of ± 10°C. The results showed that all the quality, textural, and sensory characteristics of goat meat sausage investigated were significantly influenced (p < .05) by the frying conditions. The effective moisture diffusivity ranged from 1.22 × 10-8 to 2.84 × 10-8 m2/s and 2.43 × 10-9 to 1.22 × 10-8m2/s for the moisture loss and fat absorption, respectively. Activation energies estimated were 71.04 to 77.76 KJ/mol and 65.82 to 67.2 KJ/mol, respectively. The frying kinetics obeyed the first-order rate constant, and the temperature dependency of moisture loss was higher compared to fat absorption of the fried goat meat sausage in all the samples. The optimal conditions for the deep fat frying of goat meat sausage were achieved using cooking time of 45 min fat frying temperature of 150°C and time of 9 min with (R 2 > 0.9) and were the most preferred sausage sample and accepted by the sensory panelists. This study has shown that the optimal frying conditions observed could be a viable alternative for the commercialization of quality goat meat sausages and other fried meat products in the food industry.

Measuring citrate synthase activity as an enzymatic approach to the differentiation of chilled and frozen/thawed meat

Citrate synthase belongs between mitochondrial enzymes which are released from the meat tissue after cell membrane damage caused by ice crystal formation. The presence of this enzyme can indicate a previous freezing process. In this study, we determined citrate synthase activity for chilled and frozen/thawed meats (chicken, pork, beef, and salmon). As an additional factor, we examined a potential connection between microbial spoilage and increased enzyme activity. UV spectrophotometry was used for the evaluation of the citrate synthase activity. The effect of microbial spoilage on the enzyme activity was established through microbial analysis, which was carried out for two weeks for chilled and five months for frozen/thawed meats. The citrate synthase activity in the frozen/thawed samples was significantly higher than in the chilled samples. Dependence of microbial contamination and the increased activity of the citrate synthase was not observed. Our results suggest that there could be designed specific limits of citrate synthase activity for the resolution of chilled and frozen/thawed meats.

Investigation on Texture Changes and Classification between Cold-Fresh and Freeze-Thawed Tan Mutton

To study the texture, microstructural changes, and classification of cold-fresh (C-F), freeze-thawed once (F-T0), and freeze-thawed twice Tan mutton (F-Tt), the aforementioned three types of Tan mutton were subjected to near-infrared hyperspectrum scanning, scanning electron microscopy, and TPA testing. The original spectrum of Tan mutton was obtained at a wavelength range of 900∼1,700 nm after hyperspectrum scanning; a spectrum fragment ranging from 918 nm to 1,008 nm was intercepted, and the remaining original spectrum was used as a studied spectrum (“full spectrum” hereafter). The full spectrum was pretreated by SNV (standard normal variate), MSC (multiple scattering correction), and SNV + MSC and then extracted feature wavelengths by SPA (successive projections algorithm) and CARS (competitive adaptive reweighted sampling) algorithm, and 25 feature wavelengths were obtained. By combining these feature wavelengths with classified variables, the SNV + MSC−CARS−PLS-DA (partial least squares-discriminate analysis, PLS-DA) and SNV + MSC−SPA−PLS-DA models for classification of C-F and F-T Tan mutton were established. In contrast, SNV + MSC−CARS−PLS-DA yielded the highest classification rate of 98% and 100% for calibration set and validation set, respectively. The results indicated that the texture and surface microstructure of F-T Tan mutton deteriorated, and more worsely with F-T time. SNV+MSC-CARS-PLS-DA could be well used to classify C-F, F-T0, and F-Tt Tan mutton.