Understanding the effects of animal age on Australian sheepmeat eating quality for a cuts-based, quality grading model.

Claire Payne

Eating quality is a key profitability driver in the red meat industry influencing consumer satisfaction, purchase repeatability, and willingness to pay. To achieve this the Meat Standards Australia (MSA) cuts-based quality grading system was developed to ensure consistent eating quality underpinned by consumer ratings of sensory traits tenderness, juiciness, liking of flavour, and overall liking. The sheepmeat grading model is commercialised for lamb only as the impact of animal age on a range of cuts and cooking methods in sheepmeat is not well defined. Animal age is a crucial component to eating quality, and as such is incorporated into current price signals at market. Animal age has a negative relationship with tenderness, due to changes in collagen, and flavour, attributed to changes in fatty acids. This thesis explored the impact of animal age, and age-related factors, in sheepmeat on consumer sensory traits across multiple cuts and cooking methods using MSA protocols, to expand the development of the cuts-based MSA sheepmeat quality grading model. The first experiment compared sensory responses from 1,355 untrained consumers for new season (n =120) and old season lambs (n=120) across 8 different cuts, cooked either by grilling (loin, topside, outside, knuckle and rump) or roasting (leg, shoulder, rack). There was no difference in eating quality scores between the two age classes for the loin, leg, shoulder and rack. This was also true for the topside and outside cuts minus a few exceptions. Two cuts did show an age class effect, the knuckle and rump, where old season lambs scored lower than new season lambs. The role of fatty acid composition in age related impacts on eating quality was investigated. Animal age did influence fatty acid composition however this did not effect eating quality. Intramuscular fat % (IMF%) was highly correlated with fatty acids and any effects on eating quality were attributed to IMF% rather than fatty acids. The second experiment further explored the impact of animal age on eating quality comparing lamb (n = 10) and mutton (n = 110) consumer sensory scores and quality grade allocations. Cuts tested included the loin, outside, knuckle and rump, which were grilled, and the rack cutlet and shoulder which were roasted. The topside cut was both grilled and roasted. Age class effects varied between cuts with mutton rating lower than lamb in the roast rack cutlet and roast shoulder. However, mutton rated the same as lamb for the grilled topside, grilled knuckle, and roast topside. Despite mutton scoring lower than lamb in some cuts, all cuts except the grill topside had over 75% of samples rated as 3-star MSA quality grade or higher. Linear discriminate analyses were used to determine quality thresholds, and accuracy of MSA predicted quality grades compared to actual consumer assigned grades. Threshold values for each MSA quality grade in mutton were the same as previously reported in lamb, and the percentage of correctly assigned mutton samples into grades using predicted scores was also similar to the values presented in lamb. This demonstrates that both consumers and the MSA predicted quality scores were able to differentiate between quality grades for mutton just as well as lamb. This shows that mutton could be added to the current lamb MSA prediction model. An accurate measure of age and/or maturity would enhance the MSA eating quality prediction model. The final experiment assessed if Dual Energy Xray Absorptiometry (DEXA) technology could predict changes in bone minerals associated with age, and if changing bone minerals associated with eating quality. DEXA is a commercialised technology for measurement of carcase lean %, fat % and bone % in sheepmeat. DEXA was a positive predictor of phosphorus and calcium concentration, but only when DEXA lean % was included in the model. Calcium and phosphorus were significant positive predictors of overall liking scores, but this effect became insignificant when DEXA lean % was included, suggesting that lean % was the driver of eating quality, rather than maturity. Overall, results showed that the impact of animal age on eating quality is primarily influenced by cut and yet, even lower quality cuts of older animals still have high consumer acceptance rates. This work demonstrates the opportunity to maximise sheepmeat value by expanding the MSA cuts-based quality grading model across all sheep age classifications.

Understanding the effects of animal age on Australian sheepmeat eating quality for a cuts-based, quality grading model.

Files and links (1)

Abstract

Details

UN Sustainable Development Goals (SDGs)

Metrics