Storage Stability of Vacuum-packaged Dry-aged Beef during Refrigeration at 4°C

Use of sustainable packaging materials for fresh beef vacuum packaging application and product assessment using physicochemical means

Packaging material should guarantee the longest possible shelf life of food and help to maintain its quality. The aim of the study was to assess the physicochemical changes taking place during 28-day ageing of beef steaks packed in two types of multilayer films containing biodegradable polymers - polylactic acid (NAT/PLA) and Mater-Bi® (NAT/MBI). The control group consisted of steaks packed in synthetic polyamide/polyethylene (PA/PE) film. The samples stored in NAT/PLA had significantly lower purge loss than the control samples and the lowest expressible water amount after 14 and 21 days. Following blooming, the most favourable colour was shown in steaks stored in NAT/MBI, with the highest values for the L*, a* and C* parameters and the R630/580 ratio, a high proportion of oxymyoglobin, and the lowest share of metmyoglobin. All steaks, regardless of the type of packaging material, had acceptable tenderness and were stable in terms of lipid oxidation.

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.

Preliminary data on the microbial profile of dry and wet aged bovine meat obtained from different breeds in Sardinia

This study aimed to evaluate the influence of dry and wet aging on microbial profile and physicochemical characteristics of bovine loins obtained from four animals of two different breeds, namely two Friesian cull cows and two Sardo-Bruna bovines. During dry and wet aging aerobic colony count, Enterobacteriaceae, mesophilic lactic acid bacteria, Pseudomonas, molds and yeasts, Salmonella enterica, Listeria monocytogenes and Yersinia enterocolitica, pH and water activity (a_w) were determined in meat samples collected from the internal part of the loins. Moreover, the microbial profile was determined with sponge samples taken from the surface of the meat cuts. Samples obtained from Friesian cows were analyzed starting from the first day of the aging period and after 7, 14, and 21 days. Samples obtained from the Sardo Bruna bovines were also analyzed after 28 and 35 days. Wet aging allowed better control of Pseudomonas spp. during storage that showed statistically lower levels (P>0.05) in wet-aged meats with respect to dry-aged meats during aging and particularly at the end of the period (P>0.01) in both cattle breeds. At the end of the experiment (21 days), aerobic colony count and Pseudomonas in Fresian cows' dry-aged meats showed mean levels >8 log, while lactic acid bacteria mean counts >7 log were detected in wet-aged meats of both cattle breeds. In meats submitted to dry aging, pH was significantly higher (P<0.01) with respect to wet-aged meats at all analysis times and in both cattle breeds. A_w showed a stable trend during both dry and wet aging without significant differences. These preliminary results highlight the critical importance of the strict application of good hygiene practices during all stages of production of these particular cuts of meat intended for aging.

Microbiological Changes during Long-Storage of Beef Meat under Different Temperature and Vacuum-Packaging Conditions

We evaluated a combination of two temperatures and two packaging materials for long-term storage of vacuum-packaged (VP) beef striploins. Microbial populations and microbiome composition were monitored during refrigerated storage (120 days between 0-1.5 °C) and refrigerated-then-frozen storage (28 days between 0-1.5 °C then 92 days at -20 °C) under low-O₂ permeability VP and high-O₂ permeability VP with an antimicrobial (VPAM). Pseudomonas (PSE) and Enterobacteriaceae (EB) counts in VPAM samples were significantly higher (p < 0.05) than in VP samples at 28, 45, 90, and 120 days of storage. Microbiome data showed that bacteria of the genera Serratia and Brochothrix were more abundant in VPAM samples at 120 days, while lactic acid bacteria (LAB) dominated in VP samples. Frozen temperatures inhibited microbial growth and maintained a relatively stable microbiome. Refrigerated and frozen VPAM samples showed the greatest difference in the predicted metabolic functions at the end of storage driven by the microbiome composition, dominated by PSE and LAB, respectively. Although no signs of visible meat deterioration were observed in any sample, this study suggests that VP meat refrigerated and then frozen achieved better microbiological indicators at the end of the storage period.

Microbiological safety of aged meat

The impact of dry-ageing of beef and wet-ageing of beef, pork and lamb on microbiological hazards and spoilage bacteria was examined and current practices are described. As 'standard fresh' and wet-aged meat use similar processes these were differentiated based on duration. In addition to a description of the different stages, data were collated on key parameters (time, temperature, pH and aw) using a literature survey and questionnaires. The microbiological hazards that may be present in all aged meats included Shiga toxin-producing Escherichia coli (STEC), Salmonella spp., Staphylococcus aureus, Listeria monocytogenes, enterotoxigenic Yersinia spp., Campylobacter spp. and Clostridium spp. Moulds, such as Aspergillus spp. and Penicillium spp., may produce mycotoxins when conditions are favourable but may be prevented by ensuring a meat surface temperature of -0.5 to 3.0°C, with a relative humidity (RH) of 75-85% and an airflow of 0.2-0.5 m/s for up to 35 days. The main meat spoilage bacteria include Pseudomonas spp., Lactobacillus spp. Enterococcus spp., Weissella spp., Brochothrix spp., Leuconostoc spp., Lactobacillus spp., Shewanella spp. and Clostridium spp. Under current practices, the ageing of meat may have an impact on the load of microbiological hazards and spoilage bacteria as compared to standard fresh meat preparation. Ageing under defined and controlled conditions can achieve the same or lower loads of microbiological hazards and spoilage bacteria than the variable log10 increases predicted during standard fresh meat preparation. An approach was used to establish the conditions of time and temperature that would achieve similar or lower levels of L. monocytogenes and Yersinia enterocolitica (pork only) and lactic acid bacteria (representing spoilage bacteria) as compared to standard fresh meat. Finally, additional control activities were identified that would further assure the microbial safety of dry-aged beef, based on recommended best practice and the outputs of the equivalence assessment.

A comprehensive review of drying meat products and the associated effects and changes

Preserving fresh food, such as meat, is significant in the effort of combating global food scarcity. Meat drying is a common way of preserving meat with a rich history in many cultures around the globe. In modern days, dried meat has become a well enjoyed food product in the market because of its long shelf-life, taste and health benefits. This review aims to compile information on how the types of meat, ingredients and the used drying technologies influence the characteristics of dried meat in physicochemical, microbial, biochemical and safety features along with technological future prospects in the dried meat industry. The quality of dried meat can be influenced by a variety of factors, including its production conditions and the major biochemical changes that occur throughout the drying process, which are also discussed in this review. Additionally, the sensory attributes of dried meat are also reviewed, whereby the texture of meat and the preference of the market are emphasized. There are other aspects and concerning issues that are suggested for future studies. It is well-known that reducing the water content in meat helps in preventing microbial growth, which in turn prevents the presence of harmful substances in meat. However, drying the meat can change the characteristics of the meat itself, making consumers concerned on whether dried meat is safe to be consumed on a regular basis. It is important to consider the role of microbial enzymes and microbes in the preservation of their flavor when discussing dried meats and dried meat products. The sensory, microbiological, and safety elements of dried meat are also affected by these distinctive changes, which revolve around customer preferences and health concerns, particularly how drying is efficient in eliminating/reducing hazardous bacteria from the fish. Interestingly, some studies have concentrated on increasing the efficiency of dried meat production to produce a safer range of dried meat products with less effort and time. This review compiled important information from all available online research databases. This review may help the food sector in improving the efficiency and safety of meat drying, reducing food waste, while maintaining the quality and nutritional content of dried meat.

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.

Metabolic, proteomic and microbial changes postmortem and during beef aging

The purpose of this review is to provide an overview of the current knowledge about proteomic and metabolic changes in beef, the microbiological alteration postmortem and during aging, and observe the influence on beef quality parameters, such as tenderness, taste and flavor. This review will also focus on the different aging types (wet- and dry-aging), the aging or postmortem time of beef and their effect on the proteome and metabolome of beef. The Ca2+ homeostasis and adenosine 5'-triphosphate breakdown are the main reactions in the pre-rigor phase. After rigor mortis, the enzymatic degradation of connective tissues and breakdown of energy metabolism dominate molecular changes in beef. Important metabolic processes leading to the formation of saccharides, nucleotides, organic acids (e.g. lactic acid), creatine and fatty acids are considered in this context as possible flavor precursors or formers of beef flavor and taste. Flavor precursors are substrates for lipid oxidation, Strecker degradation and Maillard reaction during cooking or roasting. The findings presented should serve as a basis for a better understanding of beef aging and its molecular effects and are intended to contribute to meeting the challenges of improving beef quality.

Changes in Physico-Chemical and Storage Properties of Dry-Aged Beef Loin Using Electric Field Refrigeration System

The aim of this study is to establish the dry aging period of beef loin in an electric field refrigeration system. Beef loins (Korea quality grade 2) were dry aged at 0, −1, and −2 °C temperature in an electric field refrigeration system (air velocity, 5 ± 2 m/s) and aging stopped as the value of TPC reached 7 log CFU/g. Samples were examined by aging yield, trimming yield, pH, color, water holding capacity (WHC), cooking yield, shear force, total plate count (TPC), 2-thiobarbituric acid reactive substances (TBARS), and volatile basic nitrogen (VBN). The results for aging yield, trimming yield, redness, yellowness, and chroma decreased with increasing the dry aging period. Contrariwise, those for pH, lightness, hue angle, WHC, and cooking yield increased with the dry aging period. In shear force, the lowest value occurred at four weeks at all temperatures. The results for TPC, TBARS, and VBN increased with aging period, and VBN at 6 weeks at 0 °C and 9 weeks at −1 °C exceed the standard value (20 mg/100 g), while dry aging temperature had an effect on physico-chemical and storage properties by lower temperatures showed slower progress. Therefore, dry aging on an electric field refrigerate system can be used until 4 weeks at 0 °C, 8 weeks at −1 °C, and 10 weeks at −2 °C. However, considering physico-chemical properties, 4 weeks at every temperature is suitable for manufacturing soft dry-aged beef loin.

Effect of temperature abuse on quality and metabolites of frozen/thawed beef loins

The objective of this study was to examine the effect of temperature abuse prior to cold storage on changes in quality and metabolites of frozen/thawed beef loin. The aerobic packaged samples were assigned to three groups: refrigeration (4°C) (CR); freezing (–18°C for 6 d) and thawing (20±1°C for 1 d), followed by refrigeration (4°C) (FT); temperature abuse (20°C for 6 h) prior to freezing (–18°C for 6 d) and thawing (20±1°C for 1 d), followed by refrigeration (4°C) (AFT). FT and AFT resulted in higher volatile basic nitrogen (VBN) values than CR (p<0.05), and these values rapidly increased in the final 15 d. Cooking loss decreased significantly with an increase in the storage period (p<0.05). In addition, cooking loss was lower in the FT and AFT groups than in the CR owing to water loss after storage (p<0.05). A scanning electron microscope (SEM) revealed that frozen/thawed beef samples were influenced by temperature abuse in the structure of the fiber at 15 d. Metabolomic analysis showed differences among CR, FT, and AFT from partial least square discriminant analysis (PLS-DA) based on proton nuclear magnetic resonance (¹H NMR) profiling. The treatments differed slightly, with higher FT than AFT values in several metabolites (phenylalanine, isoleucine, valine, betaine, and tyrosine). Overall, temperature abuse prior to freezing and during thawing of beef loin resulted in accelerated quality changes.

Exploring the microbiological quality and safety of dry-aged beef: A cross-sectional study of loin surfaces during ripening and dry-aged beef steaks from commercial meat companies in Belgium

A cross-sectional survey was undertaken in Belgian beef producing companies to study the current practices and the microbiological load of dry-aged loins (during production) and trimmed steaks (final product). In each company, the temperature and relative humidity of the ripening chamber were measured, and two loins (each in a different stage of the ripening process) were sampled. From the surface of each loin, a lean meat and adipose tissue sample was analysed separately, and different groups of bacteria, yeasts and moulds were enumerated. The average relative humidity in the ripening chambers was 72 ± 13% and the temperature ranged between 0.0 °C and 5.9 °C. During the drying process, most of the lean meat and adipose tissue samples showed high numbers of total psychrotrophic aerobic bacteria, Pseudomonas spp., psychrotrophic lactic acid bacteria, and yeasts, but the variation between loins was high. The microbiological load on freshly cut dry-aged steaks was generally lower than on loin surfaces, but both psychrotrophic aerobic and anaerobic bacteria were present inside several steaks. The water activity inside dry-aged beef steaks was high (a_w ≥ 0.98), which could allow growth of psychrotrophic pathogens, though more in-depth studies are necessary to determine potential growth during the storage of (trimmed) steaks or even inside loins during the dry-aging process.

Effect of Ilex x meserveae Aqueous Extract on the Quality of Dry-Aged Beef

The effect of meat marinating with aqueous extract of Ilex meserveae dried leaves on dry-aged beef quality was investigated. Shear force, TBARS value, color parameters, fatty acid profile, and sensory properties were evaluated in beef cuts dry-aged for 21 days. The use of Ilex meserveae dried leaves as marinade at 0.5, 1.0, and 2.0% $\text{w}/\text{v}$ did not affect the shear force and color parameters of dry-aged beef. The marinating of beef cuts with Ilex meserveae resulted in efficient prevention of lipid oxidation without impairing sensory acceptability. Aqueous extract Ilex meserveae can be applied as a natural ingredient in meat marinade to prevent peroxidation.

Effect of Different Aging Methods on the Formation of Aroma Volatiles in Beef Strip Loins

This study investigated the effects of different aging methods on the changes in the concentrations of aroma volatiles of beef. One half (n = 15) of the beef strip loins were dry-aged, and the other half were wet-aged, and both aging processes continued for 28 days. The aroma volatiles from dry- and wet-aged samples were analyzed at seven-day intervals (n = 3 for each aging period). As the aging period increased, dry-aged beef showed higher concentrations of volatile compounds than those in wet-aged beef (p < 0.05). Most changes in the concentrations of aroma volatiles of dry-aged beef were associated with propanal, 2-methylbutanal, 2-methylpropanal, 1-butanamine, trimethylamine, 2-methyl-2-propanethiol, and ethyl propanoate, which were mainly produced by lipid oxidation and/or microbial activity (e.g., proteolysis and lipolysis) during the dry aging period. Therefore, we suggest that the differences in aroma between dry- and wet-aged beef could result from increased lipid oxidation and microbial activity in dry-aged beef possibly owing to its ambient exposure to oxygen.

The effects of time and relative humidity on dry-aged beef: Traditional versus special bag

The objective of this study was to evaluate the effects of relative humidity (RH) and different dry aging methods on the quality of beef. Sixteen loins, from eight carcasses, were used in this experiment. Each pair of loin was cut into eight sections with equal size, which were evenly assigned to eight treatments, by the combination of two dry aging methods (traditional and highly moisture-permeable special bag), two relative humidity (65 and 85% RH) and two aging times (21 and 42 days). At 85% RH, neither special bag nor the traditional dry aging methods were viable, since samples presented high microbiological counts, mucus and bad odor. At 65% RH, Enterobacteriaceae and lactic acid bacteria were not detected in any treatment. The highest aerobic plate count and psychrotrophic count were observed in the samples of the traditional dry-aged process whereas the special bag showed the greatest mold and yeast count. Regarding dry aging in special bag, there was a reduction in the weight loss (P < 0.05) and no change in the physical-chemical characteristics (P > 0.05) compared to traditional dry aging. The values of pH, moisture and Warner-Bratzler shear force were not affected (P > 0.05) by aging method and relative humidity. Thus, the results indicate that high RH should be avoided for both dry aging methods. Furthermore, the special bag dry aging can be considered an alternative to produce dry-aged beef, as it reduces weight losses even at conditions of lower relative humidity.

Quality characteristics of the enhanced beef using winter mushroom juice

This study investigated the quality properties of enhanced beef, manufactured by injecting the beef with a brine containing winter mushroom juice powder (WMJP). The enhanced beef was manufactured by injecting the eye of round with brine (15% by green weight). Four treatments consisted of control (no injection of brine) and three enhanced beef, EBS (brine containing 5 g sodium chloride per kg beef), EBW 0.2 (brine containing 5 g sodium chloride and 2 g WMJP per kg beef), and EBW 0.5 (brine containing 5 g sodium chloride and 5 g WMJP per kg beef), were tested. The effect of enhancement or WMJP on the quality properties of beef was evaluated during storage at 4°C for 1, 5, and 10 days. Total aerobic bacteria counts between the control and the enhanced beef, and among EBS, EBW 0.2, and EBW 0.5 were not significantly different after any storage period (p > 0.05). The pH of beef was not different between the control and the enhanced beef, and among enhanced beef at 1 and 5 days of storage (p > 0.05). However, it was higher in the enhanced beef than control, and EBW 0.2 and EBW 0.5 had higher pH than EBS after 10 days of storage (p < 0.05). The enhanced beef showed a high total loss at all storage days (p < 0.05). There were no differences in total loss among enhanced beef after any storage period (p > 0.05). The enhanced beef had no consistent differences in L*, a*, and b* values with control during storage, however, EBW 0.5 showed high color stability. The hardness of the enhanced beef was significantly lower than that of the control after 10 days of storage, although the values were lower at all storage stages. EBS 0.5 had the lowest thiobarbituric acid reactive substance (TBARS) value among cooked beef of all treatments at all storage days. The enhanced beef received higher scores in all sensory properties than control, and no negative effect of WMJP was found in the sensory quality of the enhanced beef. The use of winter mushroom juice can result in quality improvement in enhanced beef.