The association between total volatile basic nitrogen (TVB-N) concentration and other biomarkers of quality and spoilage for vacuum packaged beef.

Beef longissimus lumborum muscles (24) were each portioned into 6 steaks, and these were held at ~0.5 °C for up to 14 weeks. Total volatile basic nitrogen (TVB-N) data was compared against other measures of quality and freshness: total viable microbial count (TVC), ultimate pH, drip loss, purge, moisture content, cook loss, shear force, particle size, vitamin E, intramuscular fat content (IMF) and colour parameters. There was an association between TVB-N and colour parameters; and between TVB-N and several parameters for microbial load, tenderness and moisture. IMF and vitamin E were not correlated to TVB-N. TVB-N of 5.1 mg/100 g (95% confidence intervals: 4.6-5.5 mg/100 g) was estimated as equivalent to a TVC of log 7 cfu/g. When beef samples were categorised as either spoilt or fresh using this TVC recommendation, TVB-N was correct in 77.9% of its assignments. Additional investigation is necessary to confirm this result against a larger sample population with a broader range of TVB-N values.

Post-mortem pH decline in lamb semitendinosus muscle and its relationship to the pH decline parameters of the longissimus lumborum muscle: A pilot study.

This study compared longissimus lumborum (LL) and semitendinosus (ST) muscles, in 48 lamb carcasses, to determine their pH decline parameters and achievement of ideal pH criteria (hitting the window). These include the pH at temperature 18 °C (pH@18) and temperature at pH 6 (temp@pH6). No practical difference were found between muscles for pH@18 or the temp@pH6, although there were differences between the experimental carcasses evaluated. Indeed, for all but three carcasses, there were insignificant differences between the LL and ST in terms of their pH@18. This outcome suggests that the lower value and more accessible ST muscle can be measured to determine lamb carcass pH decline parameters, instead of the LL. Because of the scale of this study, additional investigation is advised prior to any adoption.

Point of purchase fatty acid profile, oxidative status and quality of vacuum-packaged grass fed Australian beef held chilled for up to 12 weeks.

We investigated the fatty acid (FA) composition, oxidative biomarkers and quality traits of chilled beef. Specifically, striploin portions were held in vacuo and chilled (~ 1.5 °C) for up to 12 weeks, and analysed dependent on their assigned chilled storage period (0, 2, 5, 8, 10 and 12 weeks). There were no practical effects observed on beef FA composition as a result of chilled storage - including several polyunsaturated FA (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Intramuscular fat content was found to have a covariate effect, but only for saturated FA and monounsaturated FA. Vitamin E and thiobarbituric acid reactive substances were unchanged. Furthermore, improvements to shear force and particle size were evident at 2 weeks and thereafter, no further variation was evident. These findings suggest that beef produced to be healthier based on the EPA, DHA and PUFA content will remain so, for up to 12 weeks. Likewise, beef quality will be preserved across this same period.

The identification of dark cutting beef carcasses in Australia, using Nix Pro Color Sensor™ colour measures, and their relationship to bolar blade, striploin and topside quality traits.

Within 24 h post-mortem, loin surfaces of Australian beef carcasses (n = 436) were evaluated using the Nix Pro Color Sensor™ (NIX). The potential for colorimetrics (L*, a*, b*, hue and chroma) to discriminate between dark cutting (DC) and non-dark cutting (nDC) carcasses was compared. For this purpose, a chroma threshold of 30.5 delivered maximum total sensitivity and specificity. The bolar blade, striploin and topside from a selection of DC and nDC carcasses were also removed, aged for 14 d and tested for shear force, drip loss, cooking loss, ultimate pH, colour change over 3 d display (ΔE), and sarcomere length. Association between chroma values and these quality traits were investigated by linear models. The hypothesis of zero slope was rejected (P < 0.05) for pH on striploin and topside, but the models had poor predictive ability (R2 = 0.23). The NIX was found to be a viable grading tool, with limited capacity to provide additional insights into beef quality.

Effect of homogenisation speed and centrifugation on particle size analysis of beef and the relationship with shear force.

This study aimed to investigate the effect of homogenisation speed and centrifugation on particle size (PS) evaluation, and examine its relationship with shear force. Beef Longissimus lumborum (LL) muscle portions were randomly assigned to different ageing periods (0, 3 or 5 weeks), and tested for PS and shear force. The PS analysis was conducted at different homogenisation speeds (11,000, 16,000 and 19,000 rpm) with and without a centrifugation step prior to measurement. Samples homogenised at 11,000 rpm and not centrifuged gave PS results significantly different at each ageing time as did samples homogenised at 19,000 rpm and centrifuged. Overall samples homogenised at 11,000 rpm produced the lowest coefficient of variation for PS results. There was a significant correlation between PS and shear force across the different homogeniser speeds and centrifugation statuses. It is concluded that best practice when measuring PS in beef includes a homogeniser speed of 11,000 rpm with no centrifugation prior to measurement.

Effect of long term chilled (up to 5 weeks) then frozen (up to 12 months) storage at two different sub-zero holding temperatures on beef: 3. Protein structure degradation and a marker of protein oxidation.

Different chilled (~0.1 °C for up to 5 weeks) then frozen storage (up to 12 months) combinations and two frozen storage holding temperatures (-12 °C and -18 °C) effects on beef M. longissimus lumborum (LL) protein structure degradation and a marker of protein oxidation were tested. Particle size (PS) analysis and protein solubility results found storage combination effects on protein degradation to be significant (P < 0.05), although the influence of frozen holding temperatures was negligible. LL carbonyl, and nitrate and nitrite content responses were variable and yet broadly reflected an increased incidence of protein oxidation across increasing chilled storage and ensuing frozen storage periods - this aspect meriting future exploration. Total myoglobin content and the estimated myoglobin redox fractions (metmyoglobin, deoxymyoglobin, and oxymyoglobin) were also subject to storage treatment. These findings demonstrate the capacity for beef storage selection (chilled-then-frozen) to manage compositional protein changes and its implications on sensory quality traits across comparative 'long term' durations.

Effects of chilled-then-frozen storage (up to 52weeks) on an indicator of protein oxidation and indices of protein degradation in lamb M. longissimus lumborum.

This study investigated the protein oxidation properties of lamb following chilled-then-frozen storage. Experimental (n=360) M. longissimus lumborum (LL) were randomly sampled from the boning room of a commercial Australian abattoir, at 24h post mortem, and assigned to five chilled storage periods (0, 2, 4, 6 and 8weeks) and six subsequent frozen storage periods (0, 4, 8, 12, 24 and 52weeks). Upon completion of each storage treatment combination, corresponding LL were sub-sectioned and analysed for carbonyl content, protein solubility, nitrate/nitrite content, particle size analysis and estimated myoglobin fractions. The association between these protein measures and shear force was also explored. During chilled storage, particle size and sarcoplasmic protein solubility decreased which indicated protein degradation, while frozen storage only affected myoglobin oxidation. Tenderness was best explained by decreased particle size, decreased deoxymyoglobin and increased oxymyoglobin. No carbonyl effects were observed. It can be concluded that, according to these analyses, that in chilled-then-frozen lamb carbonyl formation was negligible.

Effect of long term chilled (up to 5weeks) then frozen (up to 12months) storage at two different sub-zero holding temperatures on beef: 1. Meat quality and microbial loads.

Beef loins (LL) stored under different chilled-then-frozen storage combinations (up to 5 and 52weeks, respectively) and two frozen holding temperatures were evaluated for microbial load and meat quality parameters. We found holding temperature effects to be negligible, which suggest -12°C could deliver comparable quality LL to -18°C across these same storage periods. Meat quality parameters varied significantly, but when compared to existing consumer thresholds these may not be perceptible, colour being the exception which proved unacceptable, earlier into retail display when either chilled and subsequent frozen storage periods were increased. There was insufficient detection of key spoilage microbes to allow for statistical analysis, potentially due to the hygienic and commercially representative LL source, although variation in water activity, glycogen content, pH and other moisture parameters conducive to microbial proliferation were influenced by chilled-then-frozen storage. These outcomes could be applied to defining storage thresholds that assure beef quality within export networks, leveraging market access, and improving product management.

Differential response to an algae supplement high in DHA mediated by maternal periconceptional diet: intergenerational effects of n-6 fatty acids.

Algae high in docosahexaenoic acid (DHA) may provide a source of long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) for inclusion in the diet of lambs to improve the LCn-3PUFA status of meat. The effect of background LCn-3PUFA status on the metabolism of high DHA algae is, however, unknown. The aim of the current study was to determine whether the response to a high in DHA algae supplement fed to lambs for six weeks prior to slaughter was mediated by a maternal periconceptional diet. Forty Poll Dorset × Border Leicester × Merino weaner lambs were allocated to receive either a ration based on oat grain, lupin grain, and chopped lucerne (control) or the control ration with DHA-Gold™ algae included at 1.92 % DM (Algae) based on whether the dams of lambs had previously been fed a diet high in n-3 or n-6 around conception. LCn-3PUFA concentration was determined in plasma and red blood cells (RBC) prior to and following feeding. The concentrations of EPA and DHA in the plasma and RBC of lambs receiving the control ration were significantly (p < 0.001) lower when lambs received the ration for 14 days compared with pre-feeding concentrations. The concentrations of EPA and DHA were also significantly (p < 0.001) higher when lambs consumed the Algae ration compared with the control ration for 42 days. The increase in EPA and DHA was, however, significantly (p < 0.05) lower if lamb dams had previously been fed a diet high in n-6 at conception. Assessing the previous nutrition and n-3 status of lambs may allow producers to more accurately predict the likely response to supplements high in LCn-3PUFA, particularly, DHA.