Electrical stimulation and wet ageing effects on the carcass and meat quality of Australian rangeland goats.

Medium voltage electrical stimulation and wet ageing periods effects on the carcasses and meat quality of Australian rangeland goats were investigated. 64 rangeland goats were slaughtered as 2 equal consignments, wherein half were exposed to post-dressing electrical stimulation (300 V, 500 ms pulse width, 45 s) and half were not (control). Carcass and pH decline parameters and glycogen concentration were recorded. At 24 h post-mortem, fresh colour was measured and longissimus lumborum muscles (LL) removed. Within carcass, paired LL were halved and allocated to each of 4 ageing periods (1, 2, 4, or 21 d). There were no significant effects from electric stimulation on LL pH at 18 °C, LL temperature at pH 6, LL pH at 24 h post-mortem, semitendinosus pH at 24 h post-mortem, and LL glycogen concentration. There were no significant interactions between stimulation and ageing period on cooking loss, particle size, purge loss, sarcomere length, shear force, and ultimate pH. Independent to stimulation, shear force, particle size, and cooking values declined as ageing period increased. Purge loss was highest after 21 d of ageing. Colour stability was unaffected by ageing, although all CIE colour coordinates varied across the 74 h total retail display period. There were negative linear relationships found between LL glycogen concentrations and LL temperature at pH 6, ultimate pH, and sarcomere length. These findings suggest there to be little benefit to post-dressing electrical stimulation of rangeland goat carcasses, when applied independent to or in combination with ageing.

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.

Effects of sex, sire and in-bag dry-ageing on the physicochemical and microbial properties, colour and fatty acids stability of lamb.

Forty legs from twenty lamb of different sexes and sires (colour stable and labile) were aged using in-bag dry- (BD) and wet-ageing (W) for 21 days. BD resulted in significantly lower moisture content, cook loss, colour (L*, a*, b* and chroma) and % polyunsaturated fatty acids (FAs), higher levels of microbial growth and saturated FAs compared to W. Similar NADH content was observed regardless of sex, sire and ageing. Samples from ram and labile sire had significantly higher pH and saturated FAs and reduced monounsaturated FAs composition compared to those from ewe and stable sire. Lamb from labile sire had significantly higher fat melting point than the stable. Thus, the superior stability of stabile sire was observed only in ram and was not impaired by BD. The sex × sire interaction on oxidative stability demonstrated potential to tailor the quality of dry-aged lamb through altering sex and sire of animals.

The effect of wet ageing duration (up to 14 weeks) on the quality and shelf-life of grass and grain-fed beef.

The quality, colour, and shelf-life of wet aged grass and grain-fed beef were compared. Striploins (n = 24) were each divided into 6 portions and were assigned to different ageing periods (0, 3, 5, 8, 11, or 14 weeks). Analysis demonstrated that declines in shear force and particle size occurred within the first 3 weeks of ageing. Extended ageing resulted in increases in beef purge and pH; and decreases in total moisture, drip, and cooking loss. The initial grass-fed beef drip (3.1%) and particle sizes (201.0 µm) were higher than for grain-fed beef (1.8% and 145.2 µm, respectively). Total viable counts were > 7 cfu/g after 5 weeks of ageing. Total volatile basic nitrogen was < 15 mg/100 g, even after 14 weeks of ageing. Product line by ageing period interactions affected vitamin E and colour parameters. In conclusion, wet aged beef maintains 'acceptable' microbial loads for 5-8 weeks, irrespective of product line and without any deterioration in its quality.

Influence of Wet Ageing on Beef Quality Traits.

Fresh samples of Longissimus thoracis of Charolais (n = 12), Romagnola (n = 15), Limousine (n = 77), and crossbreed (n = 62) animals were evaluated with different storage periods (0, 4, 9, and 14 days). Proximate analysis (i.e., pH, humidity, color, free water content, and physical parameters) was performed for each sample. The data obtained were evaluated with a mixed model, setting 5 fixed effects (breed, storage time, animals age, EUROP conformation, number of animal transports) and the animal as random. The results demonstrated that meat quality was affected mainly by the wet ageing period and that the visual and tactile parameters were also found to be susceptible to the storage time. The conservation entailed a decrease in meat humidity and an increase in L* and b* traits; it also led to a decrease in the hardness of the sample, in turn affecting the other texture profile analysis parameters considered. Fixed effects affected in different ways the traits analyzed i.e., pH and humidity changed with breed, as well as with EUROP classification, animals' age for some TPA parameters, and the number of animal transports for both visual and tactile parameters. Wet ageing influenced the meat quality, often improving it, confirming how important further research would be to identify precise storage times in relation to the parameters studied.

Wet bone-in ageing and effect on beef quality technological parameters.

This study aimed to evaluate the effect of wet ageing on chemical-physical characteristics of sirloin and bone-in rib eye steaks obtained from 18 months old young bulls and 27 months old heifers. A positive beef tenderization effect of wet ageing was observed with lower values constantly detected in the rib-eye samples and significantly lower shear force values showed in heifer steaks if compared to bulls. The pH values detected both in pre- and post-ageing samples fell in the normal range for meats. The water holding capacity of sirloin samples increased with ageing while in rib eye steaks, no significant differences were detected among samples taken before and after ageing. Meat ageing resulted in a decrease of cooking loss, while meat colour parameters were not influenced by ageing and fell within the normal range. An evident improvement of the sensorial quality of bone-in wet aged beef, especially in tenderness, was achieved.

Effects of different ageing methods on colour, yield, oxidation and sensory qualities of Australian beef loins consumed in Australia and Japan.

This study investigated the effect of three ageing methods (dry, wet and stepwise wet-then-dry) and ageing time on pH, colour, yield, lipid and protein oxidation and eating quality of beef loins using Meat Standards Australia (MSA) sensory protocols with 900 and 540 consumers in Australia and Japan, respectively. Australian beef loins (Longissimus thoracis et lumborum) at four days post mortem were subjected to wet ageing (boneless; for 7, 21, 35 or 56 days), dry ageing (bone-in; for 35 or 56 days) or a wet-then-dry ageing method (bone-in; 21 days wet ageing followed by 35 days dry ageing). The pH was higher in dry aged than wet aged beef loins (P < .001). Instrumental measurement of surface colour of trimmed dry and wet aged steaks showed significant differences in a*, b* and hue angle. Weight loss was higher in dry aged primals (P < .001), however, total water content was similar among the two ageing methods (P = .934). Retail yield did not differ between 35 and 56 days dry aged primals. Lipid (TBARS) and protein (total carbonyl content) oxidation between the dry and wet aged samples differed depending on the ageing time. When comparing the wet-then-dry and 56 days dry aged samples, only pH and retail yield differed. Australian and Japanese consumers rated dry aged steaks significantly higher (P < .001) than the wet aged counterparts for tenderness, juiciness, flavour, overall liking and weighted palatability scores. The wet-then-dry steaks were also rated higher than the 56 days wet aged steaks for flavour, overall liking and palatability within the Japanese sensory panels. The Japanese consumers also consistently rated all MSA sensory attributes lower (P < .001) than the Australian consumers. The results from this study show dry ageing provides a value adding opportunity for the meat industry in both domestic and export markets.

Influence of ageing on longissimus lumborum quality from Holstein-Friesian young bulls fed different diets.

The aim of the study was to investigate the effect of ageing (9 and 14 days) on beef obtained from Polish Holstein-Friesian bulls (n = 24) fed different dietary treatments containing the addition of herbal preparations (treatments: control, one and two herbal preparations). Between the 9th and 14th day of ageing, moisture and expressible water contents, Warner-Bratzler Shear Force (WBSF) and intensity of untypical taste significantly decreased, whereas redness, yellowness, chroma, intensity of meat aroma and tenderness increased. Interactions between ageing and dietary treatment on pH, expressible water, cooking loss and WBSF were noted. Using two herbal preparations in a dietary treatment enabled to obtain 9-days aged beef with similar tenderness as compared with 14-days aged beef from the control treatment. Therefore, it is possible to decrease the ageing time of beef by using a well-designed dietary treatment.

Effects of electrospun chitosan wrapping for dry-ageing of beef, as studied by microbiological, physicochemical and low-field nuclear magnetic resonance analysis.

The effects of using electrospun chitosan fibres as a wrapping material for dry-ageing beef was studied and compared to traditional dry-ageing and wet-ageing of beef for up to 21 days. The chitosan treatment showed improved results in terms of yield, reduction of microbial counts, yeasts and moulds, and lighter appearance compared to traditional dry-ageing. Weight and trimming losses were minimal in the wet-ageing beef. However, significant growth of lactic acid bacteria was observed in this group. Transverse relaxation times indicated a lower degree of muscle denaturation during ageing in the chitosan dry-ageing beef compared to the traditional dry-ageing meat. A principal component analysis furthermore indicated that 60.6% of the variation between samples and ageing treatments could be described by differences in the water content and distribution in the muscle. The study showed that electrospun chitosan fibre mats have potential as a wrapping material for improved quality during dry-ageing of beef.