Microbiological, rheological and physical-chemical characteristics of bovine meat subjected to a prolonged ageing period

Microbiological safety of dry-aged meat: a critical review of data gaps and research needs to define process hygiene and safety criteria

Dry-aged meat is gaining popularity among food business operators and private consumers. The process is carried out in aerobic conditions by hanging beef carcasses or placing subprimal or primal cuts in a dedicated cabinet for several weeks or even months while controlling the environment through the management of process parameters such as temperature, relative humidity, and airflow. In this review, we present a critical evaluation of the literature to evaluate tools to manage the process to guarantee food safety and identify critical control points, as well as good hygiene and manufacturing practices. In controlled aging conditions, only Listeria monocytogenes and Yersinia enterocolitica can multiply, while a reduction in the number of Salmonella spp. and Escherichia coli O157:H7 is generally reported. Enterobacteriaceae usually decrease on the surface of the meat during maturation; thus, for the purpose of the hygiene evaluation of the production process, a count no higher than that of unmatured meat is expected. Besides, various studies report that the total bacterial count and the spoilage microorganisms significantly increase on the surface of the meat, up to 5-6 Log10 CFU/g in the absence of visible spoilage. Bacteria of the Pseudomonas genus tend to progressively replace other microorganisms during maturation; thus, the total mesophilic or psychrophilic bacterial load is not a good indicator of process hygiene for matured meat. Critical parameters for the control of the process are temperature, relative humidity, and ventilation, which should be monitored during the process. For this reason, equipment designed and certified for dry-aging must be used, and the manufacturer must validate the process. Food business operators must apply general good manufacturing practices (GMP) and good hygiene practices (GHP) for meat processing and some GMP and GHP specific for dry-aging. Several research needs were identified, among them the evolution of the populations of L. monocytogenes and Y. enterocolitica and the microbiology of the inner parts of the dry-aged meat.

Optimal conditions for beef tenderization through radiofrequency heating with cold air

High-temperature (15-37°C) aging can shorten the tenderizing time of beef; however, the use of constant temperature heating can lead to microbial spoilage. This study tested radiofrequency (RF) tenderization (RF-T) to find the appropriate conditions for the aging-like effect of beef without microbial spoilage. After subjecting beef to 22 h RF-T with four different cooling temperatures (15, 5, -10, and -20°C), the proliferated aerobic bacteria on the surface showed a concentration of 6-6.2 log CFU/g at -10 and -20°C, lower than 7-7.5 log CFU/g at 15 and 5°C. When beef was treated with 25 W/kg RF heating power for 48 h RF-T, the estimated reduction rate of the sliced shear force (SSF) and the increase rate of glutamic acid based on the weight before RF-T were 22.6% and 1.51-fold, which were greater than 19.6% and 1.37-fold with 20 W/kg, and 11.0% and 1.11-fold with 15 W/kg. The optimal specific RF heating power was calculated as 30 W/kg from the results' extrapolation. When processed for 48 h under optimal conditions (30 W/kg specific RF heating power, -20°C cooling air), the tenderization rate and the increased rates of free amino acids based on the weight before RF-T of beef reached over 20% and 1.5-fold with 5.22 log CFU/g aerobic bacteria, which was lesser than the Korean regulation value of 6.7 log CFU/g (5 × 106  CFU/g). Therefore, RF-T could be proposed as a promising high-temperature tenderization method with lowered risk of microbial spoilage. PRACTICAL APPLICATION: We showed that lowering the chamber temperature during RF-T was effective in surface drying and inhibiting aerobic bacteria. RF-T for 24-48 h with 30 W/kg specific RF heating power had an aging-like effect given tenderization and increase in FAAs. Moreover, by providing the matching circuit and impedance during RF-T, this method could be industrially reproducible.

Potential use of garlic products in ruminant feeding: A review

The addition of antibiotics as growth promoters to ruminant feed can result in bacterial resistance and antibiotic residues in ruminant products. Correspondingly, there is serious public concern regarding the presence of antibiotic residue in ruminant products and the consequent threat to human health. As a result, the addition of plants and their products to ruminant feeds, as an alternative to antibiotics, has received much attention recently. Garlic and its products are rich in organosulphur compounds, which have a variety of biological activities and have been widely used as natural additives in animal production. This review presents recent knowledge on the addition of garlic products (powder, skin, oil, leaf and extracts) to the diets of ruminants. In this paper, garlic products are evaluated with respect to their chemical composition, bioactive compounds, and their impacts on the rumen ecosystem, antioxidant status, immune response, parasitic infection, growth performance and product quality of ruminants. This review provides valuable guidance and a theoretical basis for the development of garlic products as green, highly efficient and safe additives, with the aims of promoting ruminant growth and health, reducing methane emissions and improving ruminant product quality. Garlic extracts have the potential to control parasite infections by decreasing the faecal egg count. Garlic powder, oil and allicin are able to reduce the methane emissions of ruminants. Organosulphur compounds such as allicin, which is present in garlic products, have the potential to inhibit membrane lipid synthesis of the archaeal community, thus influencing the population of methanogenic archaea and resulting in a reduction in methane emissions. Some garlic products are also able to increase the average daily gain (garlic skin, water extract, and leaf) and the feed conversion ratio (garlic skin and leaf) of ruminants. Garlic stalk silage fed to sheep has the potential to improve the nutritional value of mutton by increasing the concentrations of linoleic and linolenic acids and essential amino acids. Sheep fed a diet containing garlic powder or oil are able to produce milk with higher concentrations of the conjugated linoleic acids and n-3 fatty acids, which has health benefits for consumers, due to the widely recognized positive impact of n-3 polyunsaturated fatty acids and conjugated linoleic acids on human heart health, improving platelet aggregation, vasodilation and thrombotic tendency. Overall, garlic products have the potential to enhance growth performance and product quality and reduce parasite infections, as well as methane emissions of ruminants.

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.

Effects of in-the-bag dry-ageing on meat quality, palatability and volatile compounds of low-value beef cuts

This study evaluated the effects of in-the-bag dry-ageing (BDA) (21 and 42 d) on meat quality, palatability, and volatile compounds of clod heart, brisket, and flat iron cuts from steers. In all cuts, BDA increased moisture losses (P < 0.05), but this did not reduce the juiciness of 21 d BDA versus wet-aged (WA) steaks. In clod heart, BDA increased overall tenderness at 21 d compared to 21 d WA (P < 0.01). Regardless of ageing period, BDA of clod heart increased beef flavour and salty taste and decreased sour-dairy and stale/cardboard flavours and concentrations of volatile compounds derived from lipid oxidation compared to WA (P < 0.05). In brisket, BDA increased salty taste and fatty aroma and reduced bloody/serumy flavour, whereas decreased beef and buttery flavours and intensified some unpleasant aromas/flavours (P < 0.05) for both ageing periods. The BDA of flat iron increased several undesirable aromas/flavours and decreased sweet taste and beef and buttery flavours (P < 0.05), regardless of ageing period. Overall, BDA for 42 d decreased meat quality and palatability and increased concentrations of volatile compounds from lipid oxidation, especially in flat iron cuts. Value could be recovered by customizing BDA periods by cut.

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.

Evolution of Sensory Properties of Beef during Long Dry Ageing

Ageing is an essential step in obtaining meat with satisfactory sensory properties. Dry-ageing, although being a niche practice, is increasingly being developed to enhance the taste experience of meat consumers. In this work, we studied the kinetics of the evolution of muscle properties with increasing ageing time, in order to propose an optimal duration, allowing a compromise between quality and meat weight loss reduction. Our study was performed on 32 samples from 8 animals for which the Longissimus thoracis sensory properties were analysed at different stages of ageing (7, 16, 35 and 60-days post-slaughter). This work showed an increase in the dry matter content of meat with increasing ageing duration, concomitant with a slight increase in pH. Although the luminance of the meat is stabilized after 14-days, the red and yellow indices decrease until 35-days of ageing. Iron content also decreases with ageing duration. Finally, the kinetic evolution of muscle rheological properties indicates that the toughness decreases at least up to 35-days on raw meat. Cooking seems to homogenise the tenderness of the samples, no difference was noticed between the different ageing durations when meat was cooked. These first experimental data need to be confirmed with different animal types.

Effect of Muscle Fibre Type on the Fatty Acids Profile and Lipid Oxidation of Dry-Cured Venison SM (semimembranosus) Muscle

The aim of the study was to describe the effect of fibre type on the fatty acid profile and lipid oxidation observed in dry-cured ham produced from individual semimembranosus venison (roe-deer, fallow deer, deer and wild boar) muscles. The results indicated that wild boar meat was characterised by the highest percentage of IA fibres and it contained the higher percentage of MUFA, but a low of PUFA and SFA, and was characterised by a(n-6)/(n-3) ratio lower than in the case of deer meat and greater susceptibility to oxidative changes. The highest percentage of SFA, and the lowest of MUFA and PUFA, was recorded in fallow deer meat, which was also characterised by the highest percentage of white fibres. The curing and drying processes increased the percentage share of SFA and the susceptibility of muscle lipids to oxidation, decreased the percentage of PUFA, and caused insignificant changes in the (n-6)/(n-3) ratio of fatty acids. The products were also characterised by a low amount of fat.

Effect of Packaging Type and Aging on the Meat Quality Characteristics of Water Buffalo Bulls

Simple Summary

The water buffalo is found worldwide, but mainly in Asian countries, i.e., India, Pakistan, and China. Buffalo meat can be a viable option to fulfill the future protein demands of the world’s population. Presently, very little information is available regarding buffalo meat quality attributes under different packaging types. Therefore, this study was designed to evaluate the effect of packaging type and aging time on the meat quality characteristics (instrumental color, WBSF, cooking loss, thiobarbituric acid reactive substances (TBARS), and total volatile basic nitrogen (TVB-N) of longissimus lumborum steaks. The results showed that vacuum packaging and aging were the most effective in decreasing the WBSF values of buffalo meat.

Abstract

The present study determined the effect of the packaging type and aging time on the meat quality of water buffalo (Bubalus bubalis) bulls. A total of n = 36 longissimus lumborum (LL) muscles from n = 18 buffalo bulls were obtained. Half LL muscles were packed in modified atmosphere packaging (Hi-O₂ MAP), vacuum packaging (VP), and oxygen-permeable packaging (OP) on day 1, while the other half were aged for 7 days. Meat instrumental color, cooking loss, Warner–Bratzler shear force (WBSF), thiobarbituric acid reactive substances (TBARS), and total volatile basic nitrogen (TVB-N) of the LL steaks were analyzed, both on unaged and aged buffalo meat. Color CIE L* and C* values on all display days and a* on the first 4 days of the simulated retail display under Hi-O₂ MAP packaging were significantly higher than those of the VP and OP. WBSF and TBARS values were also higher under Hi-O₂ MAP as compared to the other packaging. Steaks under OP exhibited lower cooking loss but higher TVB-N values than the MAP and VP. The 7-day-aged buffalo meat indicated higher instrumental color (L*, a* and C*), cooking loss, and lower WBSF values than fresh meat. This study concluded that Hi-O₂ MAP improved the color; however, it negatively influenced the buffalo meat’s WBSF and TBAR values. Furthermore, VP and aging were the most effective in decreasing the WBSF values of buffalo meat.

Effects of Different Levels of Inclusion of Apulo-Calabrese Pig Meat on Microbiological, Physicochemical and Rheological Parameters of Salami during Ripening

This study focused on the characterization of salami produced with meat from different pig breeds. The aim consisted in evaluating the added value of the inclusion of Apulo-Calabrese meat in the production of salami, which was characterized by production until the end of maturation (1, 30, 60, and 120 days). The experimental design involved three types of salami, two of which were produced by partial inclusion of 50 and 75% of the Italian breed pork meat (S50 and S75, respectively). Physicochemical (pH, a_w, fatty acid analysis, and malondialdehyde concentration), rheological parameters (texture analyses and color measurement), and bacterial biodiversity were evaluated. Results showed that the partial inclusion of Apulo-Calabrese meat influences the fatty acid profile of final products, which were characterized by a higher percentage of monounsaturated fatty acids compared to traditional salami; however, due to the high content of unsaturated fatty acids, S50 and S75 showed higher values of secondary lipid oxidation up to the 120th day. The linoleic and palmitic acid content significantly affected hardness and brightness. Overall, the ripening process was able to control the microbiological profile and the S50 formulation appeared as a suitable choice that could satisfy consumers for nutritional expectations and sensory profiles.

The effect of aging on beef taste, aroma and texture, and the role of microorganisms: a review

The present review summarizes the advantages and disadvantages of three different aging methods (traditional dry aging, wet aging in vacuum shrink pack and dry aging in a highly moisture-permeable bag), discusses the effects of aging on beef which focus on the formation of taste-active compounds and aroma-active compounds and texture changes, and speculates the role of microbes. All these three aging methods can improve the aroma, flavor and texture of beef to varying degrees. It is concluded that the improvement in the taste during aging may be attributed to the following three aspects: First, the release of reducing sugars from the transition of glycogen and ATP; Second, the formation of free amino acids (FAAs) and peptides through proteolysis; Third, IMP, GMP, inosine and hypoxanthine which are produced by the degradation of nucleotides. The improvement of aroma is related to the volatile aroma-active components, which are produced by the thermal oxidation/degradation of fatty acids and the Maillard reaction between amino acids and reducing sugars during aging. And the change of texture is mainly owing to the degradation of cytoskeletal myofibrin and collagen with intramural connective tissue in meat by the endogenous proteolysis system. The role of microorganism in aging will be the main direction of further research.

Evaluation of Probiotic Characteristics of Newly Isolated Lactic Acid Bacteria from Dry-Aged Hanwoo Beef

Dry aging is a traditional method that improves meat quality, and diverse microbial communities are changed during the process. Lactic acid bacteria (LAB) are widely present in fermented foods and has many beneficial effects, such as immune enhancement and maintenance of intestinal homeostasis. In this study, we conducted metagenomic analysis to evaluate the changes in the microbial composition of dry-aged beef. We found that lactic acid bacterial strains were abundant in dry-aged beef including Lactobacillus sakei and Enterococcus faecalis. We investigated their abilities in acid and bile tolerance, adhesion to the host, antibiotic resistance, and antimicrobial activity as potential probiotics, confirming that L. sakei and E. faecalis strains had remarkable capability as probiotics. The isolates from dry-aged beef showed at least 70% survival under acidic conditions in addition to an increase in the survival level under bile conditions. Antibiotic susceptibility and antibacterial activity assays further verified their effectiveness in inhibiting all pathogenic bacteria tested, and most of them had low resistance to antibiotics. Finally, we used the Caenorhabditis elegans model to confirm their life extension and influence on host resistance. In the model system, 12D26 and 20D48 strains had great abilities to extend the nematode lifespan and to improve host resistance, respectively. These results suggest the potential use of newly isolated LAB strains from dry-aged beef as probiotic candidates for production of fermented meat.

Effect of Feeding Barley, Corn, and a Barley/Corn Blend on Beef Composition and End-Product Palatability

This study evaluated the relationship among palatability attributes, volatile compounds, and fatty acid (FA) profiles in meat from barley, corn, and blended (50:50, barley and corn) grain-fed steers. Multiple correspondence analysis with three dimensions (Dim) explained 62.2% of the total variability among samples. The Dim 1 and 2 (53.3%) separated pure from blended grain-fed beef samples. Blended grain beef was linked to a number of volatiles including (E,E)-2,4-decadienal, hexanal, 1-octen-3-ol, and 2,3-octanedione. In addition, blended grain-fed beef was linked to fat-like and rancid flavors, stale-cardboard, metallic, cruciferous, and fat-like aroma descriptors, and negative categories for flavor intensity (FI), off-flavor, and tenderness. A possible combination of linoleic and linolenic acids in the blended diet, lower rumen pH, and incomplete biohydrogenation of blended grain-fed polyunsaturates could have increased (p ≤ 0.05) long-chain n-6 fatty acids (LCFA) in blended grain-fed beef, leading to more accumulation of FA oxidation products in the blended than in barley and corn grain-fed meat samples. The Dim 3 (8.9%) allowed corn separation from barley grain beef. Barley grain-fed beef was mainly linked to alkanes and beef positive FI, whereas corn grain-fed beef was associated with pyrazines, in addition to aldehydes related to n-6 LCFA oxidation.

Effect of beetroot (Beta vulgaris) extract on Black Angus burgers shelf life

Beef burgers are meat preparations with easy perishability. To ensure a longer shelflife, the Regulation EU 1129/11 allows the use of some additives. However, healthconscious consumers prefer products which do not contain synthetic substances. Aim of the present study was to evaluate the effect of Red Beetroot (Beta vulgaris) integration on Black Angus made burgers shelf life. Red beet was prepared as powder and added to meat mixture as the same or in water solution. The study was split into 2 trials to assess the extract activity also in burgers vacuum-packaged stored. Burgers were analysed (up to 9 days at 4°C) in terms of sensory properties, microbiological profile, pH, a^w and lipid oxidation (TBARS). At the end of storage, treated samples showed the highest values of redness and the lowest content of malondialdehyde, probably due to antioxidant properties of red beet towards myoglobin and lipid oxidation processes. Moreover, results highlighted that Red Beetroot activities were dose-dependent and intensified if dissolved in water. The a^w values did not appear to be conditioned by extract integrations, unlike the pH that was lower in treated samples than control ones. Microbiological analyses identified beetroot as a potential antimicrobial substance, especially in high concentration. In conclusion, Beta vulgaris extract could be proposed as natural compound exploitable in beef burgers to preserve qualities and extend their shelf-life.

The dry aged beef paradox: Why dry aging is sometimes not better than wet aging

An increasing consumer demand for a higher quality and eating experience has led to a revisit to the dry aging process. Therefore, research also focuses on the effects of different dry aging methods and aims to improve the dry aging process. However, an optimal process cannot be defined and, unfortunately, most of the dry aging results only hold true for the individual experiment. If one repeats a dry aging process in a different facility, the result might differ. The same dry aging process in two different ripening chambers does not inevitably contribute to equal tenderness and flavor. Since this is still not been understood well, this review presents results of the most relevant dry aging studies by illustrating different process parameters and cuts. Some conclusions which may be useful to explain the paradox are derived from the literature in order to understand the crucial factors and commonalities in the dry aging process.

Effects of Feeding and Maturation System on Qualitative Characteristics of Buffalo Meat (Bubalus bubalis)

We aimed to evaluate the effects of post dry ageing (PDA) period on meat colour and rheological characteristics in 16 buffalo bulls fed two different diets: with (FRS) or without (CTL) rye grass. Animals were randomly divided into two feeding groups and slaughtered at 540 ± 4.7 and 533 ± 7.0 kg of live body weight, respectively, for the CTL and FRS group. After five days post-mortem ageing (T0), Semitendinosus muscle (ST) and Longissimus muscle (LD) underwent a prolonged maturation process in a controlled meat chamber for 30 days (ST) and until 60 days (LD). After 30 days (T1), significant changes (p < 0.01) in meat colour (ΔE) in both muscles of the FRS group was recorded, while no significant change was observed in CTL group. The FRS diet had a positive effect on textural properties of ST muscle compared to CTL diet, as well as hardness, chewiness and gumminess. All qualitative characteristics improved in the first period of PDA but, whereas LD showed to keep improving, extending the post-ageing period by further 30 days, the ST becomes un-processable at 60 days. In conclusion, a combined used of fresh feeding and PDA period could enhance both tenderness and colour in animal fed FSR.