Microstructure and physical changes in the Mexican cooked lamb meat barbacoa made with chilled and frozen meat

Changes in basic composition and in vitro digestive characteristics of pork induced by frozen storage

Introduction

Frozen pork can reduce the quality of the meat and alter the digestibility and bioavailability of meat proteins in the human body. In this study, we investigated the changes in the basic composition during frozen storage and their effects on the structural properties of digestion products after protein digestion.

Methods

The impacts of frozen storage at different temperatures (-8, -18, -25, and -40°C) and for different times (1, 3, 6, 9, and 12 months) on the basic components and in vitro digestive characteristics of pork were evaluated.

Results

The moisture, crude fat, and protein contents decreased with extended storage and increased temperature, whereas muscle juice loss increased (p < 0.05). During in vitro digestion of samples frozen at -8°C for 12 months, trichloroacetic acid (TCA)-soluble peptides were decreased by 25.46% and 14.37% in the gastric and small intestinal phases, respectively, compared with fresh samples. Confocal laser scanning microscope (CLSM) showed that samples stored at -8°C had the largest particle size after digestion. Disruption of protein structure was confirmed by the decrease in α-helix, β-turn, and fluorescence intensity (all p < 0.05) and the increase in β-sheet, random coil, and maximum fluorescence wavelength of the digestion products of samples frozen at -8°C (all p < 0.05).

Discussion

Therefore, long-term high-temperature frozen storage brought about a significant decline in basic components of muscle and acceleration of loss of protein structural integrity after digestion.

Protective effects and molecular mechanisms of Litopenaeus vannamei treated with l-arginine/l-lysine against myofibrillar proteins oxidation and quality degradation during freeze-thaw cycles

The storage and processing of Litopenaeus vannamei are often challenged by the freeze-thaw (F-T) cycle phenomenon. This study delved into the influence of pretreatment with l-arginine (Arg) and l-lysine (Lys) on the myofibrillar proteins oxidation and quality of shrimp subjected to F-T cycles. Arg and Lys pretreatment notably improved water-holding capacity (WHC), textural integrity as well as the myofibrillar structure of the shrimps. A lesser reduction in the amounts of immobile and bound water was found in the amino acid-treated groups, and the oxidation of lipids and proteins were both decelerated. Molecular simulation results indicated that Arg and Lys could form hydrogen and salt-bridge bonds with myosin, enhancing the stability of Litopenaeus vannamei. The study concludes that Arg and Lys are effective in alleviating the adverse effects of F-T cycles on the quality of Litopenaeus vannamei, and provides a new solution for the quality maintenance during storage and processing.

Integrating multiple microstructure and water distribution visual analysis to reveal the moisture release and quality deterioration of precooked beef during freezing-thawing-reheating processes

Prepared dishes are becoming an increasingly important part of diets, while most studies focus on the flavor. In this study, the moisture loss induced by structure changes of precooked beef during freezing-thawing-reheating process was investigated. The myowater trapped and released by 'myenteric channels' and 'water reservoir' were observed by integrated multiple microstructure and water distribution visual analysis. X-ray results showed an increase in total porosity and the close porosity transfer to open porosity during freezing-thawing-reheating. The weight loss of frozen-reheated (FR) and frozen-thawed-reheated (FTR) samples was 6.34% and 7.69%, respectively. Although freezing-thawing did not significantly affect the moisture loss, magnetic resonance image (MRI) showed that the 'free water' temporarily existed in interfibrous spaces after thawing and leaked out during reheating. Directly reheating avoided the myowater redistribution and muscle extension mediated, which reduced moisture loss. These results provide a reference for quality control of prepared dishes during the industrial supply chain.

Changes in meat quality, metabolites and microorganisms of mutton during cold chain storage

During the cold chain storage process, changes in metabolites and microorganisms are highly likely to lead to changes in meat quality. To elucidate the changes in the composition of metabolites and microbiota during cold chain storage of mutton, this study utilized untargeted metabolome and 5R 16S rRNA sequencing analyses to investigate the changes in the longissimus dorsi under different cold chain temperatures (4 °C and -20 °C). With the extension of cold chain storage time, the meat color darkened and the content of C18:2n-6, C20:3n-6, and C23:0 were significantly increased in mutton. In this study, nine metabolites, including 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine, alanylphenylala-nine, indole-3-acrylic acid and the others, were significantly altered during cold chain storage. The abundance of the dominant microorganisms, including Brachymonas, Aeromonas, Corynebacterium and Steroidobacter, was significantly altered. Furthermore, a high correlation was observed between the different metabolites and microorganisms. These findings provide an in-depth understanding of the effects of different cold chain storage temperatures and times on the quality of mutton.

Effects of Flammulina velutipes polysaccharide with ice recrystallization inhibition activity on the quality of beef patties during freeze-thaw cycles: An emphasis on water status and distribution

The antifreeze activity of Flammulina velutipes polysaccharide (FVP) autoclave-extracted with dilute alkaline and effects of FVP on moisture status, size of ice crystals, physical and chemical characteristics of beef patties during repeated freeze-thaw (F-T) cycles were investigated. Results showed that FVP exhibited ice recrystallization inhibition activity and was able to alter the onset freezing/melting temperature of beef patties. 0.01% FVP significantly alleviated (P < 0.05) the decrement in water holding capacity by inhibiting water migration, restraining the mobility of water, and reducing the size of ice crystals of beef patties during the repeated F-T cycles. In addition, FVP could effectively inhibited oxidation reaction and protein aggregation of beef patties with significant decreases in TBARS value, protein turbidity, contents of total sulfhydryl and carbonyl of myofibrillar protein, and an increase in protein solubility during the repeated cycles. These results suggest FVP could be developed to be a promising cryoprotectant in frozen patties.

Effect of multiple freeze-thaw cycles on water migration, protein conformation and quality attributes of beef longissimus dorsi muscle by real-time low field nuclear magnetic resonance and Raman spectroscopy

Repeated freezing and thawing (F-T) happens during long-term storage and transportation due to the temperature variation, causing quality deterioration of beef products and influencing consumer acceptance. This study was aimed to investigate the relationship between quality attributes, protein structural changes and water real-time migration of beef with different F-T cycles. The results showed that multiply F-T cycles damaged the muscle microstructure and protein structure tended to denature and unfold, led lower population of water reabsorbed, thus triggering the decrease of water capacity, especially a decrease of T₂₁ and A₂₁ of completely thawed beef samples, finally affected the quality, such as tenderness, color and lipid oxidation of beef muscle. Beef should not be abused by F-T cycles >3 times, the quality extremely degraded when subjected to 5 or more F-T cycles, and real-time LF-NMR provided a new aspect to help us control the thawing process of beef.

Comparison of the immersion chilling and freezing and traditional air freezing on the quality of beef during storage

Compared to traditional air freezing, immersion chilling and freezing shows an improvement in the freezing effect on meat quality, but it is not known whether this advantage persists over longer storage periods. Therefore, the objective of the current study was to compare the effects of immersion chilling and freezing (ICF) and traditional air freezing (TAF) on the physical and chemical indexes in beef longissimus muscle during a storage period of 150 days. In the current study, the longissimus muscle from Luxi cattle (aged 20-24 months) was analyzed, with samples independently frozen by ICF and TAF. After the core temperature was frozen to below -18 degrees by the two chilling methods, samples were transferred to a -18 degrees cold room for further storage. During the storage period, physical and chemical indexes, mainly including color and texture qualities, total volatile base nitrogen (TVB-N) and peroxide value (POV) were measured and comparatively analyzed at several fixed time points. A higher freezing rate was observed in ICF (5.124 cm/h) than in TAF (0.194 cm/h), and better microstructure was observed in ICF treatment. Besides, peak force values and total energy values were significantly lower in the TAF group than in the ICF group during the first 45 days of freezing storage time (p < .05). ICF also showed better color quality due to higher L* values than TAF samples during the first 75 days of frozen storage (p < .05). In addition, the thawing loss (after 75 days of storage), total volatile base nitrogen, and peroxide value (in the 30 to 75 days of storage period) were lower in the ICF than in the TAF group. In conclusion, the immersion chilling and freezing is more conducive to the quality of beef during storage at -18 degrees compared to traditional air freezing.

Sheep meat consumers in Mexico: Understanding their perceptions, habits, preferences and market segments

Sheep meat is an essential element within the multicultural mosaic of Mexican agri-food traditions. A total of 332 consumers were surveyed face-to-face in restaurants specializing in selling traditional sheep meat products. Our results showed that consumers could be segmented based on their perceptions, habits, and preferences towards sheep meat. For consumers, sheep meat is perceived as food with unique sensory attributes, coming from healthier animals than other species and traditional characters. Their willingness to pay extra is subject to the guarantee that the meat is safe, free of hormones and antibiotics, and to a lesser extent, certified organic. The multivariate analysis suggested three clusters or consumer profiles named passive, wholehearted, and deep-rooted, which explained the associations among attitudes, some demographic variables, and consumption frequency. The nascent national sheep meat industry needs to consider these concerns in developing marketing and trust strategies to attract, maintain, and build loyalty among Mexican consumers.

Crystallization Behavior and Quality of Frozen Meat

Preservation of meat through freezing entails the use of low temperatures to extend a product’s shelf-life, mainly by reducing the rate of microbial spoilage and deterioration reactions. Characteristics of meat that are important to be preserve include tenderness, water holding capacity, color, and flavor. In general, freezing improves meat tenderness, but negatively impacts other quality attributes. The extent to which these attributes are affected depends on the ice crystalline size and distribution, which itself is governed by freezing rate and storage temperature and duration. Although novel technology has made it possible to mitigate the negative effects of freezing, the complex nature of muscle tissue makes it difficult to accurately and consistently predict outcome of meat quality following freezing. This review provides an overview of the current understanding of energy and heat transfer during freezing and its effect on meat quality. Furthermore, the review provides an overview of the current novel technologies utilized to improve the freezing process.

Effects of the dietary inclusion of babassu oil or buriti oil on lamb performance, meat quality and fatty acid composition

The effects of adding babassu oil (BAO) or buriti oil (BUO) to lamb diets, on performance, carcass characteristics, meat quality and fatty acid (FA) composition were evaluated. Feeding BAO reduced (P = .02) dry matter intake, kidney fat and dressing percentage, but did not change energy intake and performance. Meat pH, color, protein content and sensorial evaluation were not affected by diet. However, BUO increased (P = .02) intramuscular and subcutaneous fat contents, but decreased shear force. BAO increased (P < .05) trans-monounsaturated FA, total biohydrogenation intermediates (BHI) and the t10:t11 ratio, in meat and subcutaneous fat, but decreased total FA and cis-monounsaturated FA, did not change SFA, and increased (P = .04) PUFA in meat. BUO supplementation promoted the highest (P < .05) SFA and total FA content in subcutaneous fat but did not change PUFA. BAO can be used as an alternative energy source for growing lambs, but does not improve the meat FA composition.

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.

Edible quality of soft-boiled chicken processing with chilled carcass was better than that of hot-fresh carcass

Soft-boiled chicken is widely popular with its flavor and texture. In a traditional view, the edible quality of soft-boiled chicken producing with hot-fresh carcass (without any chilled procedure after evisceration) was better than that of chilled carcass. Hot-fresh groups with 1, 2, or 4 hr and chilled groups with 24, 48, or 60 hr were used to clarify the view in this study. The results indicated that no significant difference in hardness, springiness, cohesiveness of texture profiles and b* value of skin color was observed between each group, although the highest L* value was obtained in hot-fresh 4 hr group. Higher contents of succinic acid were found in chilled groups when compared to that of hot-fresh groups, but there was no difference in lactic acid and pH values. Lower contents of adenosine 5'-monophosphate (AMP), guanosine 5'-monophosphate (GMP), inosine and hypoxanthine, and higher inosine-5'-monophosphate (IMP) (especially for hot-fresh 1 hr) were observed in hot-fresh groups. In addition, although no difference in umami amino acids and bitter amino acid was observed between each tested group, higher amounts of Asp, Met, Ile, Leu, Tyr, and Arg were observed in chilled groups, especially for chilled 60 hr. The finding indicated that the traditional view was lack of scientific evidence, and chilled carcass was suitable for soft-boiled chicken, substituting for the hot-fresh carcass.

Effect of Storage Temperatures on the Moisture Migration and Microstructure of Beef

The effects of freezing temperature on the microstructure and moisture migration of beef were investigated, aiming to provide the potential theoretical basis for the beef storage. Drip loss, surface hydrophobicity, and secondary structure of myofibrillar proteins, ice crystal, and micro- and ultrastructure of meat were analyzed at 4°C, −1°C, −6°C, −9°C, −12°C, and −18°C, respectively. Results indicated that the drip loss and surface hydrophobicity of samples stored at −12°C were significantly lower than that stored at 4°C and −1°C (p<0.05) and no significant difference with −18°C (p>0.05). Result from Fourier transform infrared spectroscopy suggested that protein denaturation occurred after storage. There was an increase in α-helices and decline in random coil at lower temperature (−12°C and −18°C). It was indicated that the samples stored at −12°C and −18°C could effectively restrain the denaturation of protein and maintain the stability of secondary structure. The analysis of the ice crystal and micro- and ultrastructure of the muscle indicated that the structure of samples stored at −12°C and −18°C had more integrity and was complete than that stored at 4°C and −1°C. The spaces (water “reservoir” and “channel”) where was the origination of drip were small. Furthermore, the results of low-field nuclear magnetic resonance and 1H magnetic relaxation image showed that the freezing at −12°C could inhibit the migration of immobilized water to free water.

Qualitative and quantitative assessment of DNA quality of frozen beef based on DNA yield, gel electrophoresis and PCR amplification and their correlations to beef quality

Freezing is a practical method for meat preservation but the quality of frozen meat can deteriorate with storage time. This research investigated the effect of frozen storage time (up to 66 months) on changes in DNA yield, purity and integrity in beef, and further analyzed the correlation between beef quality (moisture content, protein content, TVB-N value and pH value) and DNA quality in an attempt to establish a reliable, high-throughput method for meat quality control. Results showed that frozen storage time influenced the yield and integrity of DNA significantly (p < 0.05). The DNA yield decreased as frozen storage time increased due to DNA degradation. The half-life (t_1/2 = ln2/0.015) was calculated as 46 months. The DNA quality degraded dramatically with the increased storage time based on gel electrophoresis results. Polymerase chain reaction (PCR) products from both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) were observed in all frozen beef samples. Using real-time PCR for quantitative assessment of DNA and meat quality revealed that correlations could be established successfully with mathematical models to evaluate frozen beef quality.