SmartStretch™ technology. III. The impact of medium voltage stimulation and SmartStretch™ technology on sheep topside (m. semimembranosus) meat quality traits under commercial processing conditions.

This study evaluated the interaction between medium voltage electrical stimulation, SmartStretch™ stretching and ageing treatments on key meat quality traits of hot boned sheep m. semimembranosus. Medium voltage stimulation reduced initial pH (P<0.001), but did not impact on other meat quality traits. There was a significant interaction between stretch treatment and ageing (P<0.001) for shear force such that samples which were both stretched and aged were the most tender. Sarcomere length was significantly (P<0.001) increased by SmartStretch™ treatment. Control (no stretching) resulted in greater (P<0.05) cooking loss, but there was significantly less purge loss (P<0.05). The ratio 630/580 nm and a* colour values at 0 and 5 days decreased at a significantly (P<0.05) slower rate when SmartStretch™ was applied. Overall medium voltage stimulation did not inhibit the effectiveness of the SmartStretch™ treatment. The SmartStretch™ treatment provided significant improvement in tenderness and the potential to increase meat display time.

Evaluation of the Hennessy Grading Probe for use in lamb carcases.

An evaluation of the Hennessy Grading Probe (HGP) was undertaken using 557 lamb carcases for the measurement of subcutaneous fat depth (Fat C) and muscle depth (EMD; m. longissimus thoracis et lumborum (LL)) between the 12th/13th ribs. All carcases were probed on the moving chain at up to 10 carcases per min and data analysis was constrained to 320 carcases which were probed at the target site (over the greatest depth of the LL at the midpoint between the 12th and 13th ribs). Analysis of the data revealed wide variability between HGP and equivalent carcase measures, but probe type (versions GP4 and GP7) had minimal impact on the usefulness of the HGP. The HGP as used in the study does not appear to be a viable option for the Australian sheep processing industry.

SmartStretch™ technology: V. the impact of SmartStretch™ technology on beef topsides (m. semimembranosus) meat quality traits under commercial processing conditions.

This study evaluated the effect of SmartStretch™ technology and ageing on meat quality traits of hot-boned beef m. semimembranosus from cull cows. The technology uses a flexible rubber sleeve surrounded by inflatable bladders that are housed within an airtight chamber. The sleeve is expanded allowing the meat to be inserted. Air is then pumped into the inflatable bladders causing the meat to be compressed by force and ejected into packaging. No significant treatment effect (P>0.05) on shear force was found although ageing did significantly reduce shear force (P<0.001). There was a significantly greater (P<0.05) cook loss at 14 days, but less (P<0.05) thaw loss and purge with 0 day cook loss unaffected (P>0.05). Sarcomere length examined by both laser diffraction and a filar micrometre method was significantly increased (P<0.05) following the treatment although a proportion of individual myofibrils appeared to have short and long sarcomeres.

SmartStretch™ technology. I. Improving the tenderness of sheep topsides (m. semimembranosus) using a meat stretching device.

This study evaluated the effect of stretching hot-boned sheep topsides using a pre-production prototype device (SmartStretch™). To test this effect, 40 sheep from 3 consignments were assessed. Left and right topsides were collected pre-rigour and randomly allocated to one of four treatments; 0 days ageing+SmartStretch™, 0 days ageing+no stretch, 5 days ageing+SmartStretch™ and 5 days ageing+no stretch. Meat from the 0 days aged+no stretch treatment was the least tender and the 5 days ageing+SmartStretch™ treatment resulted in the most tender meat. The m. semimembranosus from topsides stretched using the SmartStretch™ prototype device had a lower cooking loss percentage (P<0.001) and longer sarcomeres (P<0.001) than non-stretched m. semimembranosus. There was no effect of SmartStretch™ on myofibrillar degradation measured using particle size analysis (PSA), but there was an ageing effect (P<0.001). The tenderness of stretched m. semimembranosus showed significant improvement over non-stretched m. semimembranosus.

SmartStretch™ technology. II. Improving the tenderness of leg meat from sheep using a meat stretching device.

This study evaluated the effect of stretching hot-boned sheep hindlegs from 40 sheep carcases, classified as mutton, using a prototype device (SmartStretch™). Left and right legs were collected pre-rigor and randomly allocated to one of four treatments; 0days ageing+SmartStretch™, 0days ageing+no stretch, 5days ageing+SmartStretch™ and 5days ageing+no stretch. There was a significant interaction between stretch treatment and ageing (P<0.05) for shear force of the m. biceps femoris such that stretched and aged samples were the most tender. By contrast stretched m. semimembranosus (SM) had a significantly (P<0.05) lower shear force only at 0days of ageing. Stretching produced longer sarcomeres (P<0.001) for both the SM and m. semitendinosus muscles. Myofibrillar degradation indicated by particle size analysis or histology was not affected by stretching, but there was an ageing effect (P<0.001). SmartStretch™ provided significant improvements in tenderness of the individual muscles.

Explaining the variation in the shear force of lamb meat using sarcomere length, the rate of rigor onset and pH.

The temperature when the pH=6.0 (temp@pH6) impacts on the tenderness and eating quality of sheep meat. Due to the expense, sarcomere length is not routinely measured as a variable to explain variation in shear force, but whether measures such as temp@pH6 are as useful a parameter needs to be established. Measures of rigor onset in 261 carcases, including the temp@pH6, were evaluated in this study for their ability to explain some of the variation in shear force. The results show that for 1 day aged product combinations of the temp@pH6, the pH at 18 °C and the pH at 24 h provided a larger reduction (almost double) in total shear force variation than sarcomere length alone, with pH at 24 h being the single best measure. For 5 day aged product, pH at 18 °C was the single best measure. Inclusion of sarcomere length did represent some improvement, but the marginal increase would not be cost effective.

The effect of a kiwi fruit based solution on meat traits in beef m. semimembranosus (topside).

The effectiveness of a kiwi fruit based solution for improving the tenderness of beef m. semimembranosus and the effect on colour stability was studied. Three treatments were applied; (1) injection with the solution, (2) injection with water and (3) no injection. All samples were packaged using a SmartShape™ prototype and aged for 1 or 14 days. There was a significant effect (P<0.001) of the kiwi fruit solution on shear force, with no difference between samples injected with water and those not injected. For compression of the samples no fixed effects were significant (P>0.05). Samples not injected (control) were the darkest (lowest L* values) with no difference between samples injected with water and those injected with kiwi fruit solution. Injected samples had lower a* (redness) values than non-injected samples. In general the samples not injected had higher ratio (630/580 nm) values indicating less formation of metmyoglobin.

The impact of new generation pre-dressing medium-voltage electrical stimulation on tenderness and colour stability in lamb meat.

Previous work identified that a large number of domestic lamb carcases processed in Australia do not meet the recommended pH/temperature window during chilling. New medium voltage electrical stimulation technology has been developed to alleviate this problem. This study used an optimised setting (800mA with a pulse width 0.5ms) to evaluate the effects on meat quality with a focus on tenderness and meat colour. In total 40 (electrically stimulated) and 40 (non electrically stimulated) lambs from 11 lots killed over 2 days were evaluated. There was a significant difference (P<0.05) between stimulation treatments for initial pH, rate of pH decline and the predicted temperature at pH 6.0. There was also a large difference in the number of carcases that met the recommended window (pH of 6.0, between 18 and 25°C), with an average 67.5% of stimulated carcases and 25% of unstimulated carcases meeting or falling just above the recommended window. The stimulation treatment had no significant (P>0.05) effect on sarcomere length or myofibrillar fragmentation index (MFI) of the m. longissimus (LL). After 1day of ageing LL samples from stimulated carcases had a significantly lower (P<0.05) shear force than non stimulated samples, but there was no difference between stimulation treatments after 5 days ageing. However, ageing period did have a significant effect (P<0.001) on both MFI and shear force, such that 5days aged product had higher MFI and lower shear force values. There were minimal effects of stimulation on colour stability.

Eating quality of commercially processed hot boned sheep meat.

The aim of this work was to establish consumer perceptions of the eating quality of commercially processed hot boned sheep meat. The eating quality scores for tenderness, flavour, juiciness, and overall liking of grilled m. longissimus thoracis et lumborum (LL) were derived from untrained consumers. The animals used in this experiment were sourced from three different properties and were of various ages, breed, and sex, and had been on various quality pastures. All carcases were subjected to immobilisation, spinal discharge and high voltage electrical stimulation and boned within 2h of slaughter. All LL samples were frozen after boning according to the system applied at the abattoir and samples kept for consumer assessment and measurement of meat quality. The results showed, on average carcases entered rigor at high temperatures with a pH of 5.95 at 29.3°C. With an average sarcomere length of 1.68µm, some shortening was evident and there was a significant difference between lots in sarcomere length (P<0.05). A large percentage (82%) of samples had a pH greater than 5.8 at the time of freezing. All samples taken for shear force analysis exceeded a recommended threshold for acceptable table meat of 49N and there was no significant difference between lots (P>0.05). Only 13.5% of the samples met the 'good everyday' requirement following sensory assessment and there were significant differences between lots for eating quality traits (P<0.05). This work clearly shows that the application of effective electrical stimulation is not sufficient to ensure that hot boned sheep meat will be suitable as a table meat. These findings highlight the need for the inclusion of other intervention techniques.