Investigation of factors impacting on the attributes of Australian alpaca meat and methods to improve quality

Abstract

For the continued expansion of the predominantly pasture based alpaca industry in Australia, diversification towards meat production is required. Traditionally, alpacas have been produced for their high quality fibre and categorized as a cottage industry within Australia. However, the industry has undergone significant growth over the past 15 – 20 years and now hosts the second largest alpaca herd outside of South America, with more than 200,000 animals. This growth is expected to increase, with the national herd reaching one million over the next 6 – 10 years. For the alpaca industry to achieve this growth, the development of products that utilize the whole animal are required. Hence, a market for alpaca meat is being developed within Australia for the industry to obtain commercial sustainability. However, for this transition to occur information is required on alpaca meat characteristics associated with yield, quality and consumer perception as well as processing technologies at slaughter. This requires an in-depth biochemical analysis and interpretation which will benefit the producer, processor and consumer. To achieve this, the aims of this thesis were: 1. establish the optimal slaughter age and gender for producing meat from alpacas under Australian production systems; 2. document the variation in retail cuts within alpaca carcasses; 3. determine the effect of electrical stimulation (ES) and tenderstretching (TS) on alpaca meat and its impact on meat quality (MQ) for potential application by processors; 4. determine the effect of ageing on alpaca meat; and 5. determine the effect of feeding grain supplementation prior to slaughter and its effects on MQ. To achieve these aims, two major experiments were carried out on-farm (located on the South Coast of NSW) with animals processed and sampled at a camelid certified, mixed species abattoir with samples analysed at various institutions across Australia (NSW DPI (Cowra, Wagga Wagga and Armidale), The University of Sydney, The University of New England, The University of New South Wales, Murdoch University). The first experiment provides the basis for chapters two, three and four of this thesis and was designed to help determine the optimal balance between saleable meat yield, meat quality and nutritive value of alpaca meat across three age groups (18, 24 and 36 month old alpacas) and two genders (females and castrated males). In addition, the processing technique electrical stimulation (ES) was applied to one side of each carcass to determine its effect on alpaca carcass and meat quality. Experiment two provides the basis for chapters five and six of this thesis and comprised a feeding study phase prior to slaughter, to observe the effects of mixed grain supplementation compared to pasture only production. An overlying processing treatment of tenderstretching (TS) was applied to one half of each carcass at processing to determine its impact on meat quality. This body of work contains the first study to investigate carcass traits and saleable meat yield (SMY) of alpaca carcasses across three ages (18, 24, and 36 months) and two genders (castrated males and females). After a full carcass breakdown, it was determined that alpacas produce longer, leaner carcasses with larger eye muscle areas (EMA) than sheep. Average alpaca carcass characteristics for cold carcass weight, length, and eye muscle area (EMA) were 27 kg (range 15 – 41), 77 cm (range 67 – 88 cm), and 32.4 cm2 (range 17 – 46 cm2) respectively. When 18 month animals were compared to other species such as sheep it was determined that alpacas produce longer (14 cm longer than lamb and 8 cm longer than mutton; Wynn & Thwaites, 1981), carcasses with larger EMA (19 cm2) than sheep (Wynn & Thwaites, 1981). In addition, male carcasses were found to have higher percentages of SMY and lower values of trim, when compared to female carcasses. These combinations of traits lead to male carcasses having a more desirable SMY, indicating their suitability for meat production. In addition, it was determined that electrical stimulation (ES) had a positive impact on alpaca meat quality, by reducing the incidence of cold induced shortening, particularly in the m. longissimus thoracis et lumborum (LL) muscle, as determined by the longer sarcomere lengths (ES = 1.81 vs no-ES = 1.67 µm) in the LL and improved tenderness by reducing shear force (SF) values by 22 N in the LL (5 day aged ES = 61.1 vs 5 day aged no-ES = 83 N), and by 5.8 N (ES = 46 vs no-ES= 46 N) in the m. semimembranosus (SM). Further improvements in SF were observed in the LL when it was aged an additional 5 days (total 10 days aging) with SF values decreasing to 54.5 N in ES product and 61.1 N in no-ES product. The improvement in tenderness as a result of ES and aging the LL for 10 days was confirmed by a sensory analysis with participants rating ES alpaca samples higher in overall eating quality, tenderness, juiciness and flavour, than non-stimulated product. This shows that the use of ES should be implemented into processing practices to increase consumer eating quality. Improvements in meat tenderness were also observed in TS alpaca carcasses. Tenderness was improved by 9 N in the SM muscle (TS = 36 vs no-TS 45 N), but tenderness was reduced in the LL (TS = 74 vs no-TS = 69 vs. no-TS = 69 N) and tenderloin (TS = 42 vs no-TS 44 N) muscles. In other species the application of TS has resulted in improved SF results in the LL, but this was not the case in this study where large variation in response to TS was observed across this muscle. Regardless, extending the length of aging the LL from 10 to 21 days had a positive effect on tenderness with an additional 5 N improvement in SF in both TS (69 N) and non-TS (63 N) product. Overall, this indicates that both ES and TS processing techniques are effective at improving meat tenderness in different regions of the carcass, and that aging alpaca meat is beneficial for improving meat tenderness. Alpaca meat has its own species specific colour parameters between lamb and beef, with lower b* values. It also has favourable characteristics under retail display with minimal browning occurring, resulting in meat colour ratio (spectrophotometric colour ratio (630/550) used as an indicator of brownness) levels staying above acceptability thresholds for longer than other species. This is an important finding as consumer purchasing decisions at the retail level have been shown to be heavily influenced by product colour with increased rates of browning during display leading to discounted product and reduced product shelf life. On closer investigation, it was determined through fibre typing methods, that the m. longissimus thoracis et lumborum (LL) is a predominantly glycolytic muscle, comprised of 76 % type IIX fibres. This finding assists in the understanding of meat colour parameters and biochemical changes (including glycolytic capacity driving pH) occurring in the muscle prior to the onset of rigor mortis and the transformation into meat. Muscle fibre characteristics also have an association with intra muscular fat (IMF) content, with glycolytic type muscles typically having less IMF content then oxidative muscles. This was confirmed with alpaca meat having less than 1 % IMF. This contributed to alpaca meat being categorized as a lean and nutritious dietary protein source containing a good source of omega 3’s and beneficial zinc levels. From the nutrition feeding study it was determined that mixed grain supplementation had minimal impact upon carcass and meat quality traits with low levels of IMF and favourable levels of PUFA maintained despite nutritional treatment (mixed grain supplementation and/or pasture-only). This is desirable for industry as it provides the increased flexibility in supplementing animals without increasing variation in product quality. Overall, it can be concluded that 22- 24 month old castrated male alpacas provide optimal meat production and quality as they combine the highest degree of balance between SMY and MQ. This information is beneficial for producers as it provides a target age for slaughter. Furthermore, alpaca meat was found to be a nutritious dietary protein source with favourable nutrient and meat quality attributes (including colour), with overall tenderness enhanced and consistency improved with 10 day wet aging. Although the feeding of grain supplementation had minimal effect on MQ, this could be favourable for product consistency as it suggests it can be used during periods when pasture is limited. In addition, it is advised that ES and TS be applied to carcasses during processing to minimize the effects of CIS and improve eating quality of alpaca meat. As such future investigations into the joint application of ES and TS is warranted to determine if there is an additive effect resulting in whole carcass improvement through reducing the risk of muscle shortening, given that ES significantly improves LL tenderness and TS improves the hindquarter. It is thought that this approach may also help further improve alpaca product consistency and meat quality. This thesis provides information that can be readily applied at both the producer and processor level to improve alpaca meat consistency and tenderness within Australia.