# Fatty Acid Composition and Volatile Profile of _M. longissimus thoracic_ from Commercial Lambs
## 1 Introduction  
Red meat is an important source of protein, fatty acids and vitamins, which are essential for human health [1]. Dietary fat from meat plays an important role in health maintenance and disease prevention, delivers nutrients such as vitamins A, D, E, carotenoids [2], long-chain omega-3 polyunsaturated fatty acids (LC-n-3-PUFA) and conjugated linoleic acid (CLA), the latter of which is almost exclusively sourced from red meat and dairy products [3]. A high n-3 fatty acids intake diet has been reported to decrease the risk of coronary heart disease [4], while a lack of n-3 fatty acids intake in childhood is linked to behavioural and learning disorders such as attention deficit hyperactivity disorder [5]. Conversely, a high intake of saturated fatty acids (SFA) and _trans_-fatty acids adversely affects glucose metabolism and insulin resistance, which have been associated with Type II diabetes and other health concerns such as cardiovascular disease [6]. The U.S. Department of Agriculture and Human Health Services [7] has verified that the cholesterol-raising fatty acids include SFA from C12:0 to C16:0, which are commonly found in meat from ruminant animals [8]. An increasing awareness by consumers on how food influences their health [9] poses challenges for lamb producers and processors, where consumers look for food items with a higher concentration of n-3 fatty acids and lower amounts of SFA. In Australia and New Zealand, food containing over 22 and 44 mg per 100 g serve of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) may be considered as a'source' and a 'good source' of them [10], while over 40 and 80 mg per 100 g serve of EPA plus DHA are needed for a food to be considered as a'source' and a 'good source' of them in the European Union [11]. Understanding the effect of diverse forage production systems on lamb fatty acid composition, in particular n-3 fatty acids, would provide an opportunity to differentiate lamb products for discerning markets. Production systems can vary depending on animal characteristics including breed, sex and age at slaughter, and management factors such as animal diet, which are all factors that have been noted to contribute to variations in the fatty acid composition of meat [8]. For instance, the fatty acid profile of lamb becomes more saturated as the animal becomes older [12]. Female lambs have a tendency to deposit more fat and provide more saturated fatty acid profile than male lambs at a given weight [13;14]. Thus, there is potential for the diversity in lamb production systems between countries and between farms within countries to contribute to differences in the fatty acid composition of meat. Forage-based animal diets enhance the proportion of n-3-PUFA in meat, and often enrich meat with antioxidants compared to the meat from animals fed concentrate-based diets [15]. However, there is limited information regarding the fatty acid composition of meat from lambs finished in different grazing systems. In turn, the oxidation derivatives of PUFA contribute to the pastoral flavour in meat from ruminant animals [16]. Lipid oxidation in meat occurs in phases, where the primary phase involves the removal of hydrogen from a methylene group, which forms a radical that can be rearranged, and the secondary phase involves the decomposition of hydroperoxides and leads to the formation of volatile compounds, including some aldehydes, alcohols and ketones [17]. Although many volatile compounds responsible for meat flavour arise from heat-induced reactions during cooking, secondary oxidation compounds present in the raw meat may remain after cooking and adversely or positively affect flavour perception [18]. The broad range of forage-based commercial production systems utilised in New Zealand suggests that there is potential for variation in fatty acid and volatile profiles in lamb meat.