David Pethick

The USA and China are Australia’ s strongest sheep meat export markets , however insights into consumer perceptions of Australian sheep meat are limited . IMF and shear force are good indicators of eating quality for Australian consumers however the relationship for American and Chinese consumers is unknown. Eating quality scores (tenderness, juiciness, liking of flavour, and overall liking) were obtained from American, Australian, and Chinese consumers for Longissimus lumborum and semimembranosus muscles collected from Australian sheep (n=328). Shear force was negatively associated with all sensory traits, consistent for all countries. Whereas, increasing IMF levels had a positive impact on all eating quality scores for all countries, however the most significant change was observed for Australian consumers indicating their higher sensitivity towards IMF differences.

This study tested the palatability of lamb meat derived from pasture versus grain finishing systems. The loin and topside muscles from 105 lambs were collected. Sensory scores were generated using untrained consumers who tasted 5 day aged grilled steaks, scoring tenderness, juiciness, flavour and overall liking. Consumer scores did not differ in female lambs fed grain or pasture diets. However in wether lambs palatability scores for overall liking, tenderness and juiciness were higher for those on grain compared to those on pasture. Correcting for intramuscular fat accounted for most of these differences. These results confirm that Australian consumers do prefer grain-fed lamb meat, but only in wether lambs.

Genetic parameters were estimated for 5 sensory (overall liking, tenderness, juiciness, flavour and liking of odour) and 2 objective eating quality (EQ) traits (intramuscular fat, IMF, and shear force, SF), measured on loin and topside meat cuts (except IMF) produced by progeny from the Information Nucleus of the CRC for Sheep Industry Innovation. Heritabilities for sensory traits were low to moderate for loin and moderate to high for topside cuts. Loin IMF was highly heritable while SF was moderately heritable in both cuts. Genetic correlations among the sensory EQ traits were all positive and high (0.72-1.00). Genetic correlations between loin IMF and sensory traits were moderately positive and lowly positive for loin and topside respectively. SF had stronger, negative correlations with sensory EQ traits in the topside than in the loin. Overall liking may be improved more so through selection on IMF in the loin and SF in the topside.

An economic value for sheep meat eating quality was derived using consumer taste panel sensory trait scores and willingness to pay data. Improving eating quality by one score generated a price premium to commercial producers of $0.15/kg relative to a carcass price of $4.50/kg. Eating quality was included in a breeding objective with growth and lean meat yield. Under selection index scenarios modelled, simultaneous improvement of all traits was only possible with genomic testing of male selection candidates due to antagonistic correlations involving yield, eating quality, intramuscular fat, and shear force. Economic gain could be increased by up to 20% compared to current industry selection indexes.

Brown discolouration of lamb meat on retail display reduces consumer appeal, limiting the shelflife and value of the product. The rate of change in colour from red to brown, known as colour stability, is increased in short aged meat with high intramuscular fat (IMF) content (Calnan et al 2014). Therefore genotypic selection for IMF to improve sensory appeal may reduce lamb meat colour stability. Extended aging of lamb meat also reduces colour stability of lamb meat (Jose et al, 2008), a concern for chilled meat shipped for 35 - 70 days to distant markets. High intramuscular vitamin E (a-tocopherol) concentration, achieved by dietary supplementation, slows the loss of redness in lamb aged 5 - I 0 days (Jose et al, 2008). Given that colour stability worsens with aging, the impact of a-tocopherol may be greater in long-aged and high IMF meat. We hypothesised that high muscle a-tocopherol concentration in lambs will retain redness during display of the longissimus, particularly in long-aged and high IMF meat.

Current iron (Fe) levels in fresh pork are below requirements to claim for a source of Fe (Anonymous, 2013). Dietary studies to increase muscle Fe in pork have generally failed, although an increase in muscle redness, associated with increased haem Fe, was observed (Apple et.al 2007). Under normal feeding conditions about 10% of dietary Fe is absorbed, however this value increases markedly under Fe deficiency (West and Oates 2008). This study tested the hypothesis that feeding lower levels of dietary Fe (depletion) followed by feeding higher levels of dietary Fe (repletion) to pigs will increase muscle Fe levels.