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Nutritional composition of lamb retail cuts from the carcases of extensively finished lambs
Meat Science 154 (2019) 126–132
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Nutritional composition of lamb retail cuts from the carcases of extensively finished lambs
T
⁎
Stephanie M. Fowlera,b, , Stephen Morrisc, David L. Hopkinsa,b a
Cooperative Research Centre for Sheep Innovation, Armidale, NSW 2350, Australia Centre for Red Meat and Sheep Development, NSW Department of Primary Industries, Cowra, NSW 2794, Australia c NSW Department of Primary Industries, Wollongbar Primary Industries Institute, Wollongbar, NSW 2477, Australia b
A R T I C LE I N FO
A B S T R A C T
Keywords: Grass fed Human health Fatty acid composition Mineral composition
Despite the value of key nutritional components of lamb to human health, a large scale literature review recently highlighted the lack of nutritional information for value added lamb retail cuts which suit modern consumers. Consequently, the nutritional composition including proximate analysis, fatty acid and mineral composition of 5 lamb retail cuts from 25 commercially produced extensively finished lambs was investigated. Overall, this research indicated that there was variation in nutritional components between these cuts, particularly for nutritional traits which are important for human health including zinc, iron, total fat and protein as well as fatty acids including EPA, DHA, total saturated fatty acids and total polyunsaturated fatty acids. However the reasons for these differences are poorly understood. Therefore, further research is required to ensure that nutritional information provided to consumers for these cuts at retail is accurate.
1. Introduction Aligning meat products with the preferences of modern consumers continues to be a challenge for lamb producers and processors, as consumers are becoming increasingly conscious of the impact of their food choices on their health. As a result, the consumption of red meat in Australia, particularly lamb, has been declining, in part due to heath guidelines that recommend avoiding saturated fatty acids (National Health and Medical Research Council, 2013). However, red meat is also an important source of protein, vitamins and minerals which are essential for human health (Font-i-Furnols & Guerrero, 2014) and high fat low carbohydrate diets are becoming increasingly common to address a number of health concerns (Cunnane, 2004). Consequently, the role of meat in human diets varies depending on the individual. For example, growing children, the elderly and pregnant women may have higher requirements for key nutritional components such as iron, zinc or protein, while others following a high fat low carbohydrate diet may seek fattier cuts of meat. Despite the crucial role of nutritional components, such as iron for human health (Abbaspour, Hurrell, & Kelishadi, 2014) and the need to identify nutritional qualities of foods (Lang & Heasman, 2004), a recent large scale literature review conducted on lamb highlighted that there is a paucity of nutritional data currently available for retail cuts (Hopkins, Holman, Fowler, & Hoban, 2015). This is particularly ⁎
relevant for value-added cuts developed to address the changing consumer preferences to smaller, more convenient, retail cuts rather than larger traditional cuts (Hopkins, 1995) and better utilise larger lamb carcases (Fowler et al., 2017). Genetics, sex, age, and management of animals including feed regime are known to vary nutritional composition of lamb cuts (Bas & Morand-Fehr, 2000; Hopkins et al., 2014; Pannier, Gardner, Pearce, et al., 2014a), thus it may not accurate to report generic nutritive composition values for a range of different cuts at retail to promote value added cuts to consumers. Therefore, the aim of this research was to examine the nutritional composition of key components of lamb, including protein, fat, fatty acid composition, energy and minerals; with a particular focus on value added cuts which were identified as having no nutrition data available, such as selected leg and forequarter cuts. 2. Materials and methods 2.1. Samples Samples from extensively finished lamb carcases were collected from 4 lots of animals over 4 consecutive months (August, September, October, November) from a commercial abattoir, to represent grass fed lambs typically processed in Australia with carcase weights ranging from 19.5–25.2 kgs. Carcases sampled were verified as consuming only
Corresponding author. E-mail address: [email protected] (S.M. Fowler).
https://doi.org/10.1016/j.meatsci.2019.04.016 Received 7 January 2019; Received in revised form 17 April 2019; Accepted 19 April 2019 Available online 22 April 2019 0309-1740/ Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved.
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pasture, including mixed pastures of rye grass, clover and phalaris, from weaning until slaughter when lambs were processed using standard commercial procedures. It must be stressed that in order to obtain data which reflects the variability of nutritional composition of commercially produced grass fed spring lamb in Australia, samples were of unknown background (diet excepted), age and sex that were sampled at a commercial abattoir. At 24 h post mortem, the knuckle (HAM 5072), topside (HAM 5073), eye of shoulder (HAM 5151), eye of short loin (loin; HAM 5150) (Anonymous, 2005) and compact shoulder roast (CSR) were removed from 20 carcases (5 carcases per sampling each month from August to November) selected to represent a range in fat depth (5–16 mm) and carcase weights (19.5–25.8 kg). The CSR is created from a square cut shoulder (HAM 4992), which has the four rib rack removed before being cut between the humerus and the scapular producing a triangular shoulder cut with an average cut weight of 1.0 kg for carcases between 16 and 39 kg with an average GR tissue depth of 19 mm (Sheep CRC, 2016). Once collected, the samples were diced, mixed and frozen before being held frozen at −20 °C until further processing. Cuts were not trimmed beyond the commercial cut specifications or dissected prior to sampling to reflect the commercial cuts commonly sold within Australia. Prior to further processing, all samples were freeze dried, mixed and ground before 200 g of each sample was separated for further nutritive composition testing including energy, protein, total fat, fatty acids and minerals including zinc (Zn), iron (Fe), potassium (K) and selenium (Se).
Analytical Science, Victoria, AUS). The oven temperature was set to 150 °C and held for 30 s; increased at 10 °C per min to 180 °C; increased at 1.5 °C per min to 220 °C; and then increased at 30 °C per min up to 260 °C where this temperature was maintained for 5 min so as to result in a total run time of 36.5 min. FID temperature was 280 °C with gas flow rates of hydrogen at 35 mL per min, instrument air at 350 mL per min, and nitrogen make-up gas at 30 mL per min. Sample FAME peaks were identified by comparing their retention times with those of the internal standard and quantified using Agilent Chemistation (Version B.01.03). The peaks for some branched-chain FA were identified by comparison to published data (Or-Rashid, Fisher, Karrow, Al Zahal, & McBride, 2010). Major fatty acid group composition was calculated from the relevant individual fatty acids and all fatty acids were reported as mg/100 g fresh muscle or g/100 g fresh muscle to enable comparisons between retail cuts to be completed with relevance to human nutritional requirements.
2.2. Nutritional composition analysis
2.3. Statistical analysis
2.2.1. Proximate composition Energy was analysed using a bomb calorimeter method where 1 g of sample is compacted into a pellet and combusted in an oxygen atmosphere in a closed vessel surrounded by water (The University of Sydney, 2015). Total protein content was determined using a LECO analysis method (Leco FP628 Nitrogen analyser, Leco Corp., UK) and total fat content was determined using a soxhlet method (AOAC, 1992). Results are reported on a fresh muscle basis to facilitate a comparison relevant to human nutritional requirements and guidelines.
Variation in each trait was described by a linear model including fixed effects of muscle and random effects associated with kill date. The models then delivered the predicted mean values in each muscle with standard errors. Pairwise comparisons between the muscles were conducted by comparing the mean difference in the trait with an estimate of least significant difference calculated at the 5% critical value. The statistical analysis was conducted in the R environment (R Core Team, 2015) with particular use of the emmeans package (Lenth, Love, & Herve, 2017).
2.2.2. Fatty acid composition Fatty acid analysis was completed using a one-step extraction based on the method of Lepage and Roy (1986). Methylation was completed using 2 mL of methanol/toluene mixture (4:1 v/v) containing C13:0 (4 μg/mL) and C19:0 (4 μg/mL) as internal standards, 200 μL of acetyl chloride and 5 mL of a 6% potassium carbonate solution. Once extracted, fatty acids were identified from FAME using an Agilent 6890 N gas chromatograph (GC) equipped with a SGE BPX70 analytical column. A fused carbon-silica column, coated with cyanopropylphenyl (BPX70, 30 m × 0.25 mm i.d. and 0.25 μm film thickness, SGE Analytical Science, Victoria, AUS) was used to spear FAME. Helium was used as the carrier gas, with a total flow rate of 12.4 mL per min, a split ratio of 10:1, and a column flow of 0.9 mL per min. The inlet pressure was 107.8 kPa, its temperature was 250 °C, and injection volume was 3.0 μL into a focused inlet liner (4 mm i.d., no. 092002, SGE
3. Results
2.2.3. Mineral composition Selected mineral contents (Zn, Fe and K) were determined using a microwave digestion and inductively coupled plasma-optical emission spectroscopy (ICP-OES) detection method, while Se content was determined using microwave digestion and a inductively coupled plasma mass spectrometry (ICP-MS detection method (Carrilho, Gonzalez, Nogueira, Cruz, & Nóbrega, 2002). All results are reported on a mg/ 100 g fresh muscle basis to enable comparisons to be made with relevance to human nutritional requirements and guidelines.
3.1. Proximate composition As highlighted by Table 1, the loin had the highest protein content (22.9 g/100 g) but the lowest fat (4.5 g/100 g) and energy (702 kJ/ 100 g) content. Conversely, the compact shoulder had the highest fat and energy contents (13.3 g/100 g and 933 kJ/100 g, respectively) but the lowest protein levels (18.2 g/100 g). 3.2. Fatty acid composition Fatty acid composition varied significantly between muscles which is reflected in the differences between cuts for the total amount of saturated and monounsaturated fatty acids (Table 2). Notably, the loin
Table 1 Least square means and standard errors for protein, fat and energy measured from the compact shoulder roast, eye of shoulder, knuckle, loin and topside sampled from carcases of lambs produced in extensive systems. Trait
Compact shoulder roast
Eye of shoulder
Loin
Knuckle
Topside
S. E. M.
Protein (g/100 g) Fat (g/100 g) Energy (kJ/100 g)
18.2a 13.3c 933c
17.1a 15.3d 988d
22.9c 4.5a 702a
20.5b 6.8b 740ab
22.5c 6.6b 766b
0.5 1.0 36.1
Different letters within rows indicate significance between means (P < .05). All units are per 100 g fresh muscle. 127
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Table 2 Least square means and standard errors of individual fatty acids (mg/100 g muscle) and total group fatty acids (g/100 g muscle) measured from the compact shoulder roast, eye of shoulder, knuckle, loin and topside sampled from carcases of lambs produced in extensive systems.
SFA (mg/100 g)
MUFA (mg/100 g)
PUFA (mg/100 g)
Totals (g/100 g)
Fatty acid
Compact shoulder roast
Eye of shoulder
Loin
Knuckle
Topside
S. E. M.
C10:0 C12:0 C14:0 isoC15:0 anteiso-C15:0 C15:0 C16:0 isoC17:0 anteiso-C17:0 C17:0 C18:0 C20:0 C22:0 C23:0 C24:0 C14:1n-5 C16:1n-7 C16:1n-7t C17:1n-7 C18:1n-9 C18:1n-7 C18:1n-9t C18:1n-7t C20:1n-9 C22:1n-9 C24:1n-9 C18:2n-6 C18:3n-6 C20:2n-6 C20:3n-6 C20:4n-6 C22:4n-6 C22:5n-6 C18:3n-3 C18:4n-3 C20:3n-3 C20:4n-3 C20:5n-3 C22:5n-3 C22:6n-3 C18:2n-6t Cis 9 t11CLA Trans 10c12CLA SFA MUFA PUFA Omega-3 (mg/100 g) Omega-6 (mg/100 g) Omega-6: Omega 3 EPA + DHA (mg/100 g) PUFA: SFA
56.0b 67.1b 701.8c 26.1c 38.4c 91.9c 2859.7c 2.6b 94.2c 162.5c 2095.2b 11.8c 2.7b 2.6a 2.7bc 23.1c 232.1c 34.3c 23.7b 3665.7c 67.7c 191.4b 593.2b 8.3b 1.1bc 1.6ab 209.8bc 7.7b 5.6b 6.5a 38.4a 2.4a 0.5a 179.7b 3.4b 2.9b 3.1b 23.7ab 37.5b 13.2b 117.7b 85.3c 23.6c 6.2c 4.8c 0.7b 245.8b 497.4b 2.2b 36.9ab 0.1a
62.2b 77.8b 795.1c 29.7c 43.7c 101.6c 3258.9c 3.0b 107.4c 188.2d 2574.4c 16.0d 3.6c 2.6a 3.0c 23.2c 251.0c 40.8c 26.3b 4230.9d 74.9c 177.5b 614.5b 9.1b 1.2c 1.9b 238.8c 8.2b 6.1b 6.0a 34.2a 2.4a 0.4a 179.7b 4.3b 3.2b 3.0ab 20.6a 37.0b 11.4ab 135.9b 88.8c 28.5c 7.3d 5.5c 0.8b 259.3b 549.4b 2.2b 32.0a 0.1a
33.3a 13.5a 153.2a 5.5a 8.3a 18.2a 922.6a 1.0a 24.9a 41.8a 657.8a 3.5a 1.6a 1.9a 1.9a 5.2a 71.2a 9.5a 16.3a 1347.4a 31.4a 18.0a 158.6a 2.7a 0.8a 1.3a 140.5a 3.0a 1.8a 5.3a 44.1ab 2.1a 0.3a 75.2a 1.2a 1.5a 2.3a 28.1bc 28.2a 9.8a 28.3a 22.5a 6.9a 1.9a 1.6a 0.4a 146.2a 254.7a 1.8a 37.9ab 0.2b
33.5a 27.0a 293.8b 10.4b 16.7b 38.0b 1381.7b 1.6a 43.8b 274.4b 970.7a 5.3b 1.9a 1.8a 2.2ab 11.3b 126.0b 19.1b 17.9a 2075.4b 43.1b 30.2a 264.7a 3.7a 0.8ab 1.5a 172.6ab 4.3a 2.7a 5.5a 43.1ab 2.3a 0.4a 100.1a 1.8a 1.8a 2.4ab 25.8abc 31.9ab 11.6ab 49.7a 40.8b 12.8b 2.9b 2.6b 0.5a 175.3a 334.2a 2.0a 37.4ab 0.2b
35.0a 26.5a 284.6b 10.1b 15.6b 36.3b 1360.2b 1.4a 41.2b 237.6b 974.0a 5.3b 1.9a 1.9a 2.2ab 10.2b 116.0b 17.7ab 18.9a 1966.4b 43.3b 30.2a 268.9a 4.3a 0.9b 1.4a 170.9ab 4.3a 2.8a 6.1a 50.0b 2.4a 0.4a 98.2a 1.7a 1.7a 2.7ab 31.2c 34.0ab 12.1ab 48.3a 40.2b 11.8ab 2.9b 2.5b 0.5a 181.8a 337.2a 1.9a 43.3b 0.2b
3.2 5.3 60.1 2.5 3.9 7.9 215.4 0.3 8.1 11.8 169.5 1.0 0.2 0.4 0.2 2.2 18.2 4.5 2.2 270.0 3.7 55.7 70.4 1.6 0.1 0.1 12.1 0.8 0.7 0.4 5.3 0.3 0.1 19.2 0.5 0.2 0.3 2.6 2.5 1.3 14.3 11.7 3.5 0.5 0.4 0.1 23.3 14.8 0.1 3.9 0.011
Different letters within the same row denote significant difference between means (P < .05).
fatty acid content (146.2 mg/100 g), however it also had the lowest content of omega-6 fatty acids (197.0 mg/100 g). This difference in PUFA between muscles is emulated in both omega-3 and omega-6 fatty acids and consequently the omega-6:omega-3 ratio does not differ between the loin (1.8), topside (1.9) and knuckle (2.0), while it is slightly greater for the compact shoulder roast (2.2) and eye of shoulder (2.2). However, not all individual omega-6 fatty acids followed this trend as the greatest content of C20:4 n-6 was found in the topside (50.0 mg/ 100 g) yet this was not significantly different from the content found in the loin (44.1 mg/100 g) and knuckle (43.1 mg/100 g). EPA and DHA did not significantly differ between the loin (37.9 mg/ 100 g), knuckle (37.4 mg/100 g), compact shoulder roast (36.9 mg/ 100 g) and the eye of shoulder (32.0 mg/100 g) while the topside had a significantly greater content (43.3 mg/100 g). While the conjugated linoleic acid (CLA) content was lower in the loin (29.4 mg/100 g), and greater in the cuts from the shoulder, it did not significantly differ
had lowest concentrations (1.9 g/100 g and 1.6 g/100 g for SFA and MUFA, respectively) while the eye of shoulder had the highest concentration of SFA with 7.3 g/100 g and MUFA with 5.5 g/100 g. This is mainly due to differences in fatty acids including C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C18:1n-7 and C18:1n-9t and C18:1n-7t. There was less variation in total PUFA between cuts, as the content of the loin (0.4 g/100 g), knuckle (0.5 g/100 g) and topside (0.5 g/ 100 g) were not significantly different, although they were significantly less than the content of the compact shoulder roast and eye of shoulder (0.7 g/100 g and 0.8 g/100 g, respectively). Thus, the ratio of PUFA to SFA did not differ between the loin, topside and knuckle with ratios of 0.2, 0.2 and 0.2 respectively, while the ratio was lower for both the eye of shoulder (0.1) and the compact shoulder roast (0.1). The eye of shoulder had the highest Omega-6 fatty acid content (549.4 mg/100 g) yet it also had the highest content of Omega-3 fatty acids (259.3 mg/100 g). Similarly, the loin had the lowest omega-3 128
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such as the loin. Inclusion of intermuscular fat may also be the result of differences between studies as Williams et al. (2007) dissected samples into several components including separable lean, separable external and internal fat and waste/bone/heavy connective tissue which may better reflect the edible portion for some consumers. Yet, current food labelling requirements under the Food Standards Code requires nutritional content claims to be made on foods such as meat as sold (Anon, 2017) and as sampled in the current study. Thus, the contribution of intermuscular fat to the edible portion needs to be considered as some consumers may remove this fat prior to consumption which will lower the fat content of the meat consumed, resulting in a similar fat content to that found by Williams et al. (2007). However, other consumers may not remove this fat, which will result in a fat content which is similar to that of the current study. Thus, to ensure accurate nutritional values are reported at retail, further research to address the paucity of data needs to be completed on the edible portion of each cut, which varies with cut and market. As the fat content of leg and forequarter cuts have previously been shown to vary based on diet (Kitessa et al., 2010), the nutritional quality of the pastures over the sampling period would have varied. Many pastures used for lamb production and finishing in the temperate areas of Australia is reliant on rainfall, therefore pastures have their highest nutritional quality throughout spring which continually declines until the autumn-break rains occurs (Burnett et al., 2012). Consequently, the pasture quality would have declined over the sampling period which is reflected by the standard errors reported. Thus, it is critical that further research is completed to assess the fat content of these cuts over a longer time period and throughout weather events including drought and periods of above average rainfall to ensure nutritional composition of cuts reported at retail account for changes in pasture quality.
Table 3 Least square means and standard errors of minerals measured from the compact shoulder roast, eye of shoulder, knuckle, loin and topside sampled from carcases of lambs produced in extensive systems. Mineral (mg/ 100 g muscle)
Compact shoulder roast
Eye of shoulder
Loin
Knuckle
Topside
S. E. M.
Iron Phosphorus Potassium Selenium Sodium Zinc
1.3a 171.6b 316.8b 15.2a 58.0c 4.2c
1.4a 155.4a 288.9a 14.4a 54.7bc 4.5c
2.12c 221.3d 411.0d 18.6b 51.0a 2.9a
1.8b 202.9c 369.9c 18.5b 62.3d 4.9d
2.2c 231.9d 390.6 cd 17.8b 53.6ab 3.5b
0.1 7.6 12.3 2.8 2.3 0.2
Different letters within the same row denote significance between means (P < .05). All weights are on a fresh muscle basis.
between cuts from the same location on the carcase as the knuckle and topside (leg cuts) had 53.6 mg/100 g and 52 mg/100 g respectively while the compact shoulder roast and eye of shoulder (shoulder cuts) had 108.9 mg/100 g and 117.3 mg/100 g, respectively. 3.3. Mineral composition Iron was significantly higher in the loin (2.1 mg/100 g) and the topside (2.2 mg/100 g), yet the zinc concentration was lowest in the loin (2.9 mg/100 g) and significantly higher in all other cuts, with the knuckle containing the highest concentration (4.9 mg/100 g; Table 3). The CSR and eye of shoulder had consistently lower content of most minerals including, phosphorus, potassium, selenium and sodium, while the loin contained the highest concentration of phosphorus and potassium (Table 3). 4. Discussion
4.2. Fatty acid composition
4.1. Proximate composition
Differences between the main fatty acid groups between muscles agree with the results of Fowler et al. (2015) and Angood et al. (2008) that show as the total fat increased, the concentrations of MUFA and SFA increased, yet there was a lesser effect on the PUFAs. This is evident in the current study as the loin which contained the lowest fat content also contained the lowest concentrations of SFA and MUFA. In contrast, the compact shoulder roast yielded the highest fat content and contained the highest content of SFA and MUFA. Yet the PUFA content did not vary between the loin, knuckle and topside. Consequently, there was a significant difference in the ratio of saturated to polyunsaturated fatty acids between cuts which were derived from the shoulder compared to those from the leg and the loin. While many studies have considered the impact of intensive and extensive production systems and supplementation on the fatty acid composition of the loin (Atti & Mahouachi, 2009; Bessa, Lourenço, Portugal, & Santos-Silva, 2008; Kitessa et al., 2009; Ponnampalam et al., 2014; Ponnampalam, Burnett, Norng, Warner, & Jacobs, 2012), there is an absence of research assessing the variability between individual fatty acids between different cuts from the same carcase. A review by Bas and Morand-Fehr (2000) highlights the variation in fatty acid composition which occurs between fat depots of lambs, showing that SFAs including C14:0, C16:0 and C18:0 as well as MUFAs including C16:1 and C18:1 varied between fat depots and intramuscular fat. Therefore, it is plausible part of the variation in fatty acids may be attributed to differences in the composition of intermuscular fat included in shoulder cuts and intramuscular fat included in cuts such as the knuckle, topside and loin. Thus, length of feeding may have a bigger impact on the fatty acid composition of shoulder lamb cuts (Bessa et al., 2008) as it is probable the fatty acid composition of cuts which contain adipose tissue and intermuscular fat of such cuts can be altered by increasing fat levels associated with longer feeding periods (Borys, Borys,
The protein and energy content found in this study are consistent with figures previously reported for lamb cuts in Australia (Ponnampalam, Giri, Pethick, & Hopkins, 2014; Williams, Droulez, Levy, & Stobaus, 2007) and South Africa (Hoffman, Muller, Cloete, & Schmidt, 2003). It is plausible that change in diet, both quality and feeding intensity, is able to describe some of the variation in protein content between cuts given that lambs sampled later in the growing season may have been on a slower growth rate altering protein accretion and turnover (Millward, 2005), as the temperate pastures commonly used to finish lambs in southern Australia decline in quality and herbage over spring and summer until autumn-break rainfall (Burnett, Seymour, Norng, Jacobs, & Ponnampalam, 2012). Yet all muscles do not respond to diet at a constant rate, as the rates of protein accretion and degradation vary between muscles when dietary protein is limited (Chang & Wei, 2005) a result of fibre types, given that protein turnover varies with muscle fibre type (Therkildsen & Oksbjerg, 2009). Furthermore, muscle architecture including the number of muscle fibres and the proportion of connective tissue differs between muscles of the fore and hindquarter included in the cuts (Aalhus, Robertson, & Ye, 2009), which may also contribute to the difference in protein of cuts measured. The fat content of the shoulder cuts was greater than figures previously reported for Australian lamb as many studies have reported figures of approximately 4.5% (Fowler, Ponnampalam, Schmidt, Wynn, & Hopkins, 2015; Pannier, Pethick, Geesink, et al., 2014c; Pannier, Pethick, Boyce, et al., 2014b; Williams et al., 2007). This is considered to be the result of the anatomy of the cuts as shoulder cuts, such as the compact shoulder roast, include several muscles and therefore include contributions of intermuscular fat content which is not included in cuts 129
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highlights the difference in zinc levels between US quality grades and the country of origin suggesting that the level of minerals such as zinc found in the soil and therefore plants grazed by the lambs effects the muscle deposition. Thus, the significance of month in determining the content of minerals may reflect the abattoir sourcing lambs from different regions as seasonal conditions and rainfall change the quality of pastures. Therefore, lambs reach slaughter weights at various times depending on the local conditions. Iron levels in retail cuts from grass fed lambs significantly differed between cuts with the topside and loin containing nearly twice the iron levels of the shoulder cuts, compact shoulder roast and eye of shoulder. This disagrees with the findings of Lin et al. (1988) that no significant difference in iron levels was evident in retail cuts from either US or New Zealand lamb carcases. Other studies which have been completed on the loin demonstrate that the average iron levels for Australian lamb loin are approximately 2 mg/100 g meat (Mortimer et al., 2014; Pannier et al., 2010; Pannier, Gardner, Pearce, et al., 2014a; Williams et al., 2007). Although it is similar to iron levels in lamb carcases from the US (Lin et al., 1988), this level is higher than those reported for lamb carcases from South Africa (Hoffman et al., 2003) and New Zealand (Lin et al., 1988). Overall, these studies highlight that variation in iron levels of the loin between carcases is due to oxidative fibre type, age, geographic location, year, sex, genetics, breed, birth type, kill group, carcase weight, C site fat depth and intramuscular fat (Hoffman et al., 2003; Lin et al., 1988; Mortimer et al., 2014; Pannier et al., 2010; Pannier, Gardner, Pearce, et al., 2014a). Consequently, as with zinc levels, the most plausible explanation for differences between retail cuts from the same lamb carcases is likely to be differences in oxidative muscle fibre types due to variation in vascularity, anatomical location and function which results in red oxidative muscle fibre types also containing more iron as well as zinc (Lin et al., 1988; Pannier, Gardner, Pearce, et al., 2014a). However, it is unclear how the higher levels of fat in the shoulder cuts affect the iron content, as Pannier, Gardner, Pearce, et al. (2014a) demonstrate that increasing intramuscular fat is associated with decreasing levels of myoglobin and ICDH, therefore decreasing iron content. Given the paucity of research which has been completed on the differences between mineral levels of lamb cuts it is difficult to determine whether the causes of inter-animal variation also create intra-animal variation in mineral composition.
Oprzadek, & Przegalinska-Goraczkowska, 2011). This is particularly relevant for the increases found in C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C18:1n-7 and C18:1n-9t and C18:1n-7t as they are mainly present in triglycerides which increase with increasing fatness (Enser et al., 1998; te Pas, Everts, & Haagsman, 2004). Enser et al. (1998) are in agreeance indicating total identified fatty acids significantly differed between the m. triceps brachii, m. longissimus thoracis et lumborum, and m. gluetobiceps of carcases from grass fed lambs due to only some of the fatty acids; C18:0, C16:0, C18:1n-7, C18:2n-6, C18:3n-6 and C18:3n-3, C20:4n-6, C20:4n3, C20:5n3, C22:5n3 and C22:6n-3. This was the result of muscle fibre type as the content of phospholipids is highest in the red oxidative muscle fibres (Enser et al., 1998). However, as no muscle fibre typing was conducted it is difficult to determine whether this is the cause of the differences observed in the current study. Thus, research is required to determine the impact of muscle fibre types on the nutritive value of lamb cuts given that leg and shoulder cuts are expected to vary in muscle fibre type (te Pas et al., 2004) and genetic selection can alter the fibre types of muscles (Kelman, Pannier, Pethick, & Gardner, 2014). Furthermore, this highlights the need to determine the nutritional information for specific cuts rather than portions of the carcase such as the forequarter, rack and leg to ensure accuracy of figures reported. 4.3. Mineral composition While research has been conducted on the mineral composition of Australian lamb, it has focused on the loin (Mortimer et al., 2014; Pannier et al., 2010; Pearce et al., 2009), consequently little research has been conducted on other cuts, including those from the leg and forequarter. The concentration of zinc was significantly higher in the leg and forequarter cuts, with some cuts such as knuckle containing nearly double the zinc content of the loin. This agrees with the findings of Lin et al. (1988) that significant differences in the mineral composition occurred between retail cuts with the greatest zinc levels in the blade chop and foreshank and the lowest levels in the loin. Similarly, the levels of zinc found in the current study for the loin are similar to the average levels of approximately 2 mg/100 g of meat previously reported (Hoffman et al., 2003; Mortimer et al., 2014; Pannier et al., 2010; Pannier, Gardner, Pearce, et al., 2014a). Thus, it is hypothesised that the differences in zinc content are due to differences in muscle fibre type as a difference in the mineral levels of red and white muscle fibres has been associated with differences in vascularity, function and anatomical location with more red muscle fibre types containing more zinc (Lin et al., 1988; Pannier, Gardner, Pearce, et al., 2014a; Pearce et al., 2009). Pannier, Gardner, Pearce, et al. (2014a) suggested that these differences may be due to a higher content of myoglobin, increased vascularisation and more mitochondria which are all associated with increased oxidative capacity, as both myoglobin and isocitrate dehyrdogenase (ICDH) had a positive association with zinc content. This resulted in an increase of 0.30 mg/100 g of zinc across the 2–12.5 mg/100 g range in myoglobin levels and a 0.30 mg/100 g increase in the level of zinc across the 2–9 μmol range of ICDH. However, these findings describe differences between mineral contents of lamb loin from different carcases with varying genetic backgrounds and selection for lean growth has been shown to increase the proportion of glycolytic type IIX muscle fibres (Greenwood, Harden, & Hopkins, 2007; Pannier, Gardner, Pearce, et al., 2014a). Therefore, further research is required to determine the influence of muscle fibre type on the variation of mineral composition of lamb cuts from the same carcase. Pannier, Gardner, Pearce, et al. (2014a) highlighted the effect of production location as zinc content was influenced by site and year with lambs from Trangie containing 0.54 mg/100 g more than lambs from Rutherglen and lambs slaughtered in 2008 had a higher concentration of zinc. Similarly, the study conducted by Lin et al. (1988)
4.4. Relevance to human nutrition While this study reports significant differences between retail lamb cuts for most nutritional composition traits, differences between what is significant in terms of results do not always correlate with what is significant in terms of human health as changes to the nutritional values of meat within a recommended serve of meat can be low (Lin et al., 1988). Thus, it is important to consider the implications of the results found in this study with the current nutritional guidelines. As outlined by Food Standards Australia New Zealand (2012), nutritional claims cannot be made about PUFA without giving consideration to the total FA composition. Subsequently, to be claimed as a high source of PUFA, the total of SFA and trans fatty acid can comprise no > 28% of the total fatty acid content of the food and the food must contain 40% of the total fatty acid as PUFA (Food Standards Australia New Zealand, 2012). As the percentage of PUFA is relatively low in lamb retail cuts, the current study indicates that none of the lamb cuts measured meet the requirements for a dietary claim of being high in PUFA. Similarly, claims about the Omega-3 fatty acid content of a food also take into consideration the total fatty acid content as the food must contain no more that 28% of its total fatty acid content as SFA or trans FA or the food must not contain over 5 g of total SFA and trans fatty acids. Furthermore, the food must contain at least 200 mg of αLinolenic acid (ALA) per serving or 30 mg total EPA and DHA per serving to be considered a source while to be considered a good source of 130
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5. Conclusion
Omega-3 FA, the food must contain at least 60 mg of EPA and DHA per serving (Food Standards Australia New Zealand, 2012). Based on the data from this study, the knuckle, topside and loin all meet the nutritional requirements to be called a source of Omega-3 FA as they contain under 5 g/100 g of SFA and over 30 mg/100 g of EPA and DHA and consequently meet the nutritional guidelines per standard serve which consists of 135 g. Although the shoulder cuts also contain over 30 mg/ 100 g of EPA and DHA, their SFA content prohibits the claim being made about the eye of shoulder and compact shoulder roast. For claims that a food is a source of minerals, the food must contain at least 10% of the RDI per serve, while for claims that the food is a good source of minerals it must contain at least 25% of the RDI (Food Standards Australia New Zealand, 2012). Given that the RDI for iron is 8 mg/day for men and older women, to be a source for men and older women (National Health and Medical Research Council, 2006), 0.8 mg/ 100 g is required, while to be a good source 2 mg/100 g is required. However, for younger women, the RDI is 18 mg/day and this goes up to 27 mg/day for pregnant women. Thus, 1.8 g/100 g and 2.7 mg/100 g are required to be a source of iron while 4.5 mg/100 g and 6.75 mg/ 100 g are required to be a good source of iron for young women and pregnant women, respectively. Consequently, all retail lamb cuts measured can be deemed a good source of iron for men and older women and a source for young women, while the eye of shoulder and knuckle can be considered a good source for younger women. Similarly, for claims that a food is a source of zinc, the food needs to contain 10% of the RDI of 14 mg/day for men, 8 mg/day for women and 11 mg/day for pregnant women (National Health and Medical Research Council, 2006; Food Standards Australia New Zealand, 2012). This equates to zinc contents of 1.4 mg/100 g for men, 0.8 mg/100 g for women and 1.1 mg/100 g for pregnant women. However, to be labelled as a good source of zinc, there must be 25% of the RDI available which equates to 3.5 mg/100 g for men, 2 mg/100 g for women and 2.75 mg/ 100 g for pregnant women. Consequently, all cuts could be considered as a good source of zinc for women and pregnant women, while the loin can be considered a source of zinc for men, all of the other retail cuts measured can be considered a good source of zinc for men. A comparison of the findings in the current study compared to those which have been given by Foods Standards Australia (Food Standards Australia New Zealand, 2010), suggests that the current nutritional tables needs to be updated with new cuts. This is particularly important for the development of new cuts as this study demonstrated that leg cuts are good sources of minerals and Omega-3 FA. However nutrition information is only available on the loin chop, easy carve shoulder and easy carve leg (Food Standards Australia New Zealand, 2010) which vary from the boned out value added cuts sampled in the current study. For example, the NUTTAB reference for the zinc content of an easy carve leg is 3.6 mg/100 g (Food Standards Australia New Zealand, 2010), while this study indicates that the value for the knuckle is 4.9 mg/100 g. Similarly, the information varies for the loin as the NUTTAB data suggests that a fully trimmed loin chop has 7.1 g/100 g fat whilst this study indicates it is only 4.5 g/100 g. While based on a serving of meat as per current nutritional guidelines, the figures reported in the current study do not consider the retention of these nutrients during cooking as they were measured on the raw product, yet a majority of domestic consumers cook lamb prior to consumption. As the retention of nutrients has been shown to vary with cut, fat content, surface area of the cut, animal age and cooking method of South African mutton and lamb (van Heerden & Strydom, 2017), further research is required to determine the impact of recommended cooking methods on the nutritional composition of these cuts to ensure that the nutritional claims are relevant per serve, as eaten. However, the nutritional values found in the current study indicate that there is potential to use such nutritional data to market cuts to specific groups, such as pregnant women and the elderly, who have greater requirements for protein and minerals such as iron and zinc.
Overall, this study indicated that there is variation between retail cuts for the nutritional composition of lamb retail cuts. However, given the paucity of research which has been conducted on retail cuts from the forequarter and leg, it is difficult to determine the reasons behind some of these differences as many studies have focused on the difference between loins. This study also demonstrated that there is an ability to promote the knuckle, topside and loin from grass fed animals as a good source of Omega-3 FA as well as most of the leg and forequarter cuts sampled as a good source of iron and zinc for most men and women. However, there is still a need to conduct further research to determine the impact of factors including season, feeding length, breed, genetics, muscle fibre type, age and gender on the nutritional composition of these cuts to ensure that nutritional claims are accurate over time. Acknowledgements The authors would like to thank Cassius Coombs, Matt Kerr (NSW DPI), Jordan Hoban (NSW DPI) and Graham Gardner (Murdoch University) for their assistance in collecting and analysing the samples. Furthermore, the authors would like to thank the Sheep CRC for funding the research. References Aalhus, J., Robertson, W. M., & Ye, J. (2009). Muscle fiber characteristics and their relationship to meat quality. In M. Du, & R. Mccormick (Eds.). Applied muscle biology and meat science. United States of America: Taylor and Francis. Abbaspour, N., Hurrell, R., & Kelishadi, R. (2014). Review on iron and its importance for human health. Journal of Research in Medical Sciences: The Official Journal of Isfahan University of Medical Sciences, 19, 164–174. Angood, K. M., Wood, J. D., Nute, G. R., Whittington, F. M., Hughes, S. I., & Sheard, P. R. (2008). A comparison of organic and conventionally-produced lamb purchased from three major UK supermarkets: Price, eating quality and fatty acid composition. Meat Science, 78, 176–184. Anon (2017). In HEALTH (Ed.). Australia New Zealand food standards code standard 1.2.7 – Nutrition, health and related claims. Anonymous (2005). Handbook of Australian meat. Brisbane, Australia: AUS-MEAT Limited. AOAC (1992). AOAC official method 991.36 fat (crude) in meat and meat products. 289. Atti, N., & Mahouachi, M. (2009). Effects of feeding system and nitrogen source on lamb growth, meat characteristics and fatty acid composition. Meat Science, 81, 344–348. Bas, P., & Morand-Fehr, P. (2000). Effect of nutritional factors on fatty acid composition of lamb fat deposits. Livestock Production Science, 64, 61–79. Bessa, R. J. B., Lourenço, M., Portugal, P. V., & Santos-Silva, J. (2008). Effects of previous diet and duration of soybean oil supplementation on light lambs carcass composition, meat quality and fatty acid composition. Meat Science, 80, 1100–1105. Borys, B., Borys, A., Oprzadek, J., & Przegalinska-Goraczkowska, M. (2011). Effect of sex and fattening intensity on health-promoting value of lamb meat. Animal Science Papers and Reports, 29. Burnett, V. F., Seymour, G. R., Norng, S., Jacobs, J. L., & Ponnampalam, E. N. (2012). Lamb growth performance and carcass weight from rotationally grazed perennial pasture systems compared with annual pasture systems with supplements. Animal Production Science, 52, 248–254. Carrilho, E. N. V. M., Gonzalez, M. H., Nogueira, A. R. A., Cruz, G. M., & Nóbrega, J. A. (2002). Microwave-assisted acid decomposition of animal- and plant-derived samples for element analysis. Journal of Agricultural and Food Chemistry, 50, 4164–4168. Chang, Y.-M., & Wei, H.-W. (2005). The effects of dietary lysine deficiency on muscle protein turnover in Postweanling pigs. Asian-Australasian Journal of Animal Sciences, 18, 1326–1335. Cunnane, S. C. (2004). Metabolic and health implications of moderate ketosis and the ketogenic diet. Prostaglandins, Leukotrienes and Essential Fatty Acids, 70, 233–234. Enser, M., Hallett, K. G., Hewett, B., Fursey, G. A. J., Wood, J. D., & Harrington, G. (1998). Fatty acid content and composition of UK beef and lamb muscle in relation to production system and implications for human nutrition. Meat Science, 49, 329–341. Font-i-Furnols, M., & Guerrero, L. (2014). Consumer preference, behavior and perception about meat and meat products: An overview. Meat Science, 98, 361–371. Food Standards Australia New Zealand (2010). Nutritient tables for use in Australia (NUTTAB). Food Standards Australia New Zealand (2012). Nutrition information user guide. Fowler, S. M., Hoban, J. M., van de Ven, R., Gardner, G., Pethick, D. W., & Hopkins, D. L. (2017). The effect of lamb carcase weight and GR depth on the production of valueadded cuts – A short communication. Meat Science, 131, 139–141. Fowler, S. M., Ponnampalam, E. N., Schmidt, H., Wynn, P., & Hopkins, D. L. (2015). Prediction of intramuscular fat content and major fatty acid groups of lamb M.
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Nutritional composition of lamb retail cuts from the carcases of extensively finished lambs
T
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Stephanie M. Fowlera,b, , Stephen Morrisc, David L. Hopkinsa,b a
Cooperative Research Centre for Sheep Innovation, Armidale, NSW 2350, Australia Centre for Red Meat and Sheep Development, NSW Department of Primary Industries, Cowra, NSW 2794, Australia c NSW Department of Primary Industries, Wollongbar Primary Industries Institute, Wollongbar, NSW 2477, Australia b
A R T I C LE I N FO
A B S T R A C T
Keywords: Grass fed Human health Fatty acid composition Mineral composition
Despite the value of key nutritional components of lamb to human health, a large scale literature review recently highlighted the lack of nutritional information for value added lamb retail cuts which suit modern consumers. Consequently, the nutritional composition including proximate analysis, fatty acid and mineral composition of 5 lamb retail cuts from 25 commercially produced extensively finished lambs was investigated. Overall, this research indicated that there was variation in nutritional components between these cuts, particularly for nutritional traits which are important for human health including zinc, iron, total fat and protein as well as fatty acids including EPA, DHA, total saturated fatty acids and total polyunsaturated fatty acids. However the reasons for these differences are poorly understood. Therefore, further research is required to ensure that nutritional information provided to consumers for these cuts at retail is accurate.
1. Introduction Aligning meat products with the preferences of modern consumers continues to be a challenge for lamb producers and processors, as consumers are becoming increasingly conscious of the impact of their food choices on their health. As a result, the consumption of red meat in Australia, particularly lamb, has been declining, in part due to heath guidelines that recommend avoiding saturated fatty acids (National Health and Medical Research Council, 2013). However, red meat is also an important source of protein, vitamins and minerals which are essential for human health (Font-i-Furnols & Guerrero, 2014) and high fat low carbohydrate diets are becoming increasingly common to address a number of health concerns (Cunnane, 2004). Consequently, the role of meat in human diets varies depending on the individual. For example, growing children, the elderly and pregnant women may have higher requirements for key nutritional components such as iron, zinc or protein, while others following a high fat low carbohydrate diet may seek fattier cuts of meat. Despite the crucial role of nutritional components, such as iron for human health (Abbaspour, Hurrell, & Kelishadi, 2014) and the need to identify nutritional qualities of foods (Lang & Heasman, 2004), a recent large scale literature review conducted on lamb highlighted that there is a paucity of nutritional data currently available for retail cuts (Hopkins, Holman, Fowler, & Hoban, 2015). This is particularly ⁎
relevant for value-added cuts developed to address the changing consumer preferences to smaller, more convenient, retail cuts rather than larger traditional cuts (Hopkins, 1995) and better utilise larger lamb carcases (Fowler et al., 2017). Genetics, sex, age, and management of animals including feed regime are known to vary nutritional composition of lamb cuts (Bas & Morand-Fehr, 2000; Hopkins et al., 2014; Pannier, Gardner, Pearce, et al., 2014a), thus it may not accurate to report generic nutritive composition values for a range of different cuts at retail to promote value added cuts to consumers. Therefore, the aim of this research was to examine the nutritional composition of key components of lamb, including protein, fat, fatty acid composition, energy and minerals; with a particular focus on value added cuts which were identified as having no nutrition data available, such as selected leg and forequarter cuts. 2. Materials and methods 2.1. Samples Samples from extensively finished lamb carcases were collected from 4 lots of animals over 4 consecutive months (August, September, October, November) from a commercial abattoir, to represent grass fed lambs typically processed in Australia with carcase weights ranging from 19.5–25.2 kgs. Carcases sampled were verified as consuming only
Corresponding author. E-mail address: [email protected] (S.M. Fowler).
https://doi.org/10.1016/j.meatsci.2019.04.016 Received 7 January 2019; Received in revised form 17 April 2019; Accepted 19 April 2019 Available online 22 April 2019 0309-1740/ Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved.
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pasture, including mixed pastures of rye grass, clover and phalaris, from weaning until slaughter when lambs were processed using standard commercial procedures. It must be stressed that in order to obtain data which reflects the variability of nutritional composition of commercially produced grass fed spring lamb in Australia, samples were of unknown background (diet excepted), age and sex that were sampled at a commercial abattoir. At 24 h post mortem, the knuckle (HAM 5072), topside (HAM 5073), eye of shoulder (HAM 5151), eye of short loin (loin; HAM 5150) (Anonymous, 2005) and compact shoulder roast (CSR) were removed from 20 carcases (5 carcases per sampling each month from August to November) selected to represent a range in fat depth (5–16 mm) and carcase weights (19.5–25.8 kg). The CSR is created from a square cut shoulder (HAM 4992), which has the four rib rack removed before being cut between the humerus and the scapular producing a triangular shoulder cut with an average cut weight of 1.0 kg for carcases between 16 and 39 kg with an average GR tissue depth of 19 mm (Sheep CRC, 2016). Once collected, the samples were diced, mixed and frozen before being held frozen at −20 °C until further processing. Cuts were not trimmed beyond the commercial cut specifications or dissected prior to sampling to reflect the commercial cuts commonly sold within Australia. Prior to further processing, all samples were freeze dried, mixed and ground before 200 g of each sample was separated for further nutritive composition testing including energy, protein, total fat, fatty acids and minerals including zinc (Zn), iron (Fe), potassium (K) and selenium (Se).
Analytical Science, Victoria, AUS). The oven temperature was set to 150 °C and held for 30 s; increased at 10 °C per min to 180 °C; increased at 1.5 °C per min to 220 °C; and then increased at 30 °C per min up to 260 °C where this temperature was maintained for 5 min so as to result in a total run time of 36.5 min. FID temperature was 280 °C with gas flow rates of hydrogen at 35 mL per min, instrument air at 350 mL per min, and nitrogen make-up gas at 30 mL per min. Sample FAME peaks were identified by comparing their retention times with those of the internal standard and quantified using Agilent Chemistation (Version B.01.03). The peaks for some branched-chain FA were identified by comparison to published data (Or-Rashid, Fisher, Karrow, Al Zahal, & McBride, 2010). Major fatty acid group composition was calculated from the relevant individual fatty acids and all fatty acids were reported as mg/100 g fresh muscle or g/100 g fresh muscle to enable comparisons between retail cuts to be completed with relevance to human nutritional requirements.
2.2. Nutritional composition analysis
2.3. Statistical analysis
2.2.1. Proximate composition Energy was analysed using a bomb calorimeter method where 1 g of sample is compacted into a pellet and combusted in an oxygen atmosphere in a closed vessel surrounded by water (The University of Sydney, 2015). Total protein content was determined using a LECO analysis method (Leco FP628 Nitrogen analyser, Leco Corp., UK) and total fat content was determined using a soxhlet method (AOAC, 1992). Results are reported on a fresh muscle basis to facilitate a comparison relevant to human nutritional requirements and guidelines.
Variation in each trait was described by a linear model including fixed effects of muscle and random effects associated with kill date. The models then delivered the predicted mean values in each muscle with standard errors. Pairwise comparisons between the muscles were conducted by comparing the mean difference in the trait with an estimate of least significant difference calculated at the 5% critical value. The statistical analysis was conducted in the R environment (R Core Team, 2015) with particular use of the emmeans package (Lenth, Love, & Herve, 2017).
2.2.2. Fatty acid composition Fatty acid analysis was completed using a one-step extraction based on the method of Lepage and Roy (1986). Methylation was completed using 2 mL of methanol/toluene mixture (4:1 v/v) containing C13:0 (4 μg/mL) and C19:0 (4 μg/mL) as internal standards, 200 μL of acetyl chloride and 5 mL of a 6% potassium carbonate solution. Once extracted, fatty acids were identified from FAME using an Agilent 6890 N gas chromatograph (GC) equipped with a SGE BPX70 analytical column. A fused carbon-silica column, coated with cyanopropylphenyl (BPX70, 30 m × 0.25 mm i.d. and 0.25 μm film thickness, SGE Analytical Science, Victoria, AUS) was used to spear FAME. Helium was used as the carrier gas, with a total flow rate of 12.4 mL per min, a split ratio of 10:1, and a column flow of 0.9 mL per min. The inlet pressure was 107.8 kPa, its temperature was 250 °C, and injection volume was 3.0 μL into a focused inlet liner (4 mm i.d., no. 092002, SGE
3. Results
2.2.3. Mineral composition Selected mineral contents (Zn, Fe and K) were determined using a microwave digestion and inductively coupled plasma-optical emission spectroscopy (ICP-OES) detection method, while Se content was determined using microwave digestion and a inductively coupled plasma mass spectrometry (ICP-MS detection method (Carrilho, Gonzalez, Nogueira, Cruz, & Nóbrega, 2002). All results are reported on a mg/ 100 g fresh muscle basis to enable comparisons to be made with relevance to human nutritional requirements and guidelines.
3.1. Proximate composition As highlighted by Table 1, the loin had the highest protein content (22.9 g/100 g) but the lowest fat (4.5 g/100 g) and energy (702 kJ/ 100 g) content. Conversely, the compact shoulder had the highest fat and energy contents (13.3 g/100 g and 933 kJ/100 g, respectively) but the lowest protein levels (18.2 g/100 g). 3.2. Fatty acid composition Fatty acid composition varied significantly between muscles which is reflected in the differences between cuts for the total amount of saturated and monounsaturated fatty acids (Table 2). Notably, the loin
Table 1 Least square means and standard errors for protein, fat and energy measured from the compact shoulder roast, eye of shoulder, knuckle, loin and topside sampled from carcases of lambs produced in extensive systems. Trait
Compact shoulder roast
Eye of shoulder
Loin
Knuckle
Topside
S. E. M.
Protein (g/100 g) Fat (g/100 g) Energy (kJ/100 g)
18.2a 13.3c 933c
17.1a 15.3d 988d
22.9c 4.5a 702a
20.5b 6.8b 740ab
22.5c 6.6b 766b
0.5 1.0 36.1
Different letters within rows indicate significance between means (P < .05). All units are per 100 g fresh muscle. 127
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Table 2 Least square means and standard errors of individual fatty acids (mg/100 g muscle) and total group fatty acids (g/100 g muscle) measured from the compact shoulder roast, eye of shoulder, knuckle, loin and topside sampled from carcases of lambs produced in extensive systems.
SFA (mg/100 g)
MUFA (mg/100 g)
PUFA (mg/100 g)
Totals (g/100 g)
Fatty acid
Compact shoulder roast
Eye of shoulder
Loin
Knuckle
Topside
S. E. M.
C10:0 C12:0 C14:0 isoC15:0 anteiso-C15:0 C15:0 C16:0 isoC17:0 anteiso-C17:0 C17:0 C18:0 C20:0 C22:0 C23:0 C24:0 C14:1n-5 C16:1n-7 C16:1n-7t C17:1n-7 C18:1n-9 C18:1n-7 C18:1n-9t C18:1n-7t C20:1n-9 C22:1n-9 C24:1n-9 C18:2n-6 C18:3n-6 C20:2n-6 C20:3n-6 C20:4n-6 C22:4n-6 C22:5n-6 C18:3n-3 C18:4n-3 C20:3n-3 C20:4n-3 C20:5n-3 C22:5n-3 C22:6n-3 C18:2n-6t Cis 9 t11CLA Trans 10c12CLA SFA MUFA PUFA Omega-3 (mg/100 g) Omega-6 (mg/100 g) Omega-6: Omega 3 EPA + DHA (mg/100 g) PUFA: SFA
56.0b 67.1b 701.8c 26.1c 38.4c 91.9c 2859.7c 2.6b 94.2c 162.5c 2095.2b 11.8c 2.7b 2.6a 2.7bc 23.1c 232.1c 34.3c 23.7b 3665.7c 67.7c 191.4b 593.2b 8.3b 1.1bc 1.6ab 209.8bc 7.7b 5.6b 6.5a 38.4a 2.4a 0.5a 179.7b 3.4b 2.9b 3.1b 23.7ab 37.5b 13.2b 117.7b 85.3c 23.6c 6.2c 4.8c 0.7b 245.8b 497.4b 2.2b 36.9ab 0.1a
62.2b 77.8b 795.1c 29.7c 43.7c 101.6c 3258.9c 3.0b 107.4c 188.2d 2574.4c 16.0d 3.6c 2.6a 3.0c 23.2c 251.0c 40.8c 26.3b 4230.9d 74.9c 177.5b 614.5b 9.1b 1.2c 1.9b 238.8c 8.2b 6.1b 6.0a 34.2a 2.4a 0.4a 179.7b 4.3b 3.2b 3.0ab 20.6a 37.0b 11.4ab 135.9b 88.8c 28.5c 7.3d 5.5c 0.8b 259.3b 549.4b 2.2b 32.0a 0.1a
33.3a 13.5a 153.2a 5.5a 8.3a 18.2a 922.6a 1.0a 24.9a 41.8a 657.8a 3.5a 1.6a 1.9a 1.9a 5.2a 71.2a 9.5a 16.3a 1347.4a 31.4a 18.0a 158.6a 2.7a 0.8a 1.3a 140.5a 3.0a 1.8a 5.3a 44.1ab 2.1a 0.3a 75.2a 1.2a 1.5a 2.3a 28.1bc 28.2a 9.8a 28.3a 22.5a 6.9a 1.9a 1.6a 0.4a 146.2a 254.7a 1.8a 37.9ab 0.2b
33.5a 27.0a 293.8b 10.4b 16.7b 38.0b 1381.7b 1.6a 43.8b 274.4b 970.7a 5.3b 1.9a 1.8a 2.2ab 11.3b 126.0b 19.1b 17.9a 2075.4b 43.1b 30.2a 264.7a 3.7a 0.8ab 1.5a 172.6ab 4.3a 2.7a 5.5a 43.1ab 2.3a 0.4a 100.1a 1.8a 1.8a 2.4ab 25.8abc 31.9ab 11.6ab 49.7a 40.8b 12.8b 2.9b 2.6b 0.5a 175.3a 334.2a 2.0a 37.4ab 0.2b
35.0a 26.5a 284.6b 10.1b 15.6b 36.3b 1360.2b 1.4a 41.2b 237.6b 974.0a 5.3b 1.9a 1.9a 2.2ab 10.2b 116.0b 17.7ab 18.9a 1966.4b 43.3b 30.2a 268.9a 4.3a 0.9b 1.4a 170.9ab 4.3a 2.8a 6.1a 50.0b 2.4a 0.4a 98.2a 1.7a 1.7a 2.7ab 31.2c 34.0ab 12.1ab 48.3a 40.2b 11.8ab 2.9b 2.5b 0.5a 181.8a 337.2a 1.9a 43.3b 0.2b
3.2 5.3 60.1 2.5 3.9 7.9 215.4 0.3 8.1 11.8 169.5 1.0 0.2 0.4 0.2 2.2 18.2 4.5 2.2 270.0 3.7 55.7 70.4 1.6 0.1 0.1 12.1 0.8 0.7 0.4 5.3 0.3 0.1 19.2 0.5 0.2 0.3 2.6 2.5 1.3 14.3 11.7 3.5 0.5 0.4 0.1 23.3 14.8 0.1 3.9 0.011
Different letters within the same row denote significant difference between means (P < .05).
fatty acid content (146.2 mg/100 g), however it also had the lowest content of omega-6 fatty acids (197.0 mg/100 g). This difference in PUFA between muscles is emulated in both omega-3 and omega-6 fatty acids and consequently the omega-6:omega-3 ratio does not differ between the loin (1.8), topside (1.9) and knuckle (2.0), while it is slightly greater for the compact shoulder roast (2.2) and eye of shoulder (2.2). However, not all individual omega-6 fatty acids followed this trend as the greatest content of C20:4 n-6 was found in the topside (50.0 mg/ 100 g) yet this was not significantly different from the content found in the loin (44.1 mg/100 g) and knuckle (43.1 mg/100 g). EPA and DHA did not significantly differ between the loin (37.9 mg/ 100 g), knuckle (37.4 mg/100 g), compact shoulder roast (36.9 mg/ 100 g) and the eye of shoulder (32.0 mg/100 g) while the topside had a significantly greater content (43.3 mg/100 g). While the conjugated linoleic acid (CLA) content was lower in the loin (29.4 mg/100 g), and greater in the cuts from the shoulder, it did not significantly differ
had lowest concentrations (1.9 g/100 g and 1.6 g/100 g for SFA and MUFA, respectively) while the eye of shoulder had the highest concentration of SFA with 7.3 g/100 g and MUFA with 5.5 g/100 g. This is mainly due to differences in fatty acids including C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C18:1n-7 and C18:1n-9t and C18:1n-7t. There was less variation in total PUFA between cuts, as the content of the loin (0.4 g/100 g), knuckle (0.5 g/100 g) and topside (0.5 g/ 100 g) were not significantly different, although they were significantly less than the content of the compact shoulder roast and eye of shoulder (0.7 g/100 g and 0.8 g/100 g, respectively). Thus, the ratio of PUFA to SFA did not differ between the loin, topside and knuckle with ratios of 0.2, 0.2 and 0.2 respectively, while the ratio was lower for both the eye of shoulder (0.1) and the compact shoulder roast (0.1). The eye of shoulder had the highest Omega-6 fatty acid content (549.4 mg/100 g) yet it also had the highest content of Omega-3 fatty acids (259.3 mg/100 g). Similarly, the loin had the lowest omega-3 128
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such as the loin. Inclusion of intermuscular fat may also be the result of differences between studies as Williams et al. (2007) dissected samples into several components including separable lean, separable external and internal fat and waste/bone/heavy connective tissue which may better reflect the edible portion for some consumers. Yet, current food labelling requirements under the Food Standards Code requires nutritional content claims to be made on foods such as meat as sold (Anon, 2017) and as sampled in the current study. Thus, the contribution of intermuscular fat to the edible portion needs to be considered as some consumers may remove this fat prior to consumption which will lower the fat content of the meat consumed, resulting in a similar fat content to that found by Williams et al. (2007). However, other consumers may not remove this fat, which will result in a fat content which is similar to that of the current study. Thus, to ensure accurate nutritional values are reported at retail, further research to address the paucity of data needs to be completed on the edible portion of each cut, which varies with cut and market. As the fat content of leg and forequarter cuts have previously been shown to vary based on diet (Kitessa et al., 2010), the nutritional quality of the pastures over the sampling period would have varied. Many pastures used for lamb production and finishing in the temperate areas of Australia is reliant on rainfall, therefore pastures have their highest nutritional quality throughout spring which continually declines until the autumn-break rains occurs (Burnett et al., 2012). Consequently, the pasture quality would have declined over the sampling period which is reflected by the standard errors reported. Thus, it is critical that further research is completed to assess the fat content of these cuts over a longer time period and throughout weather events including drought and periods of above average rainfall to ensure nutritional composition of cuts reported at retail account for changes in pasture quality.
Table 3 Least square means and standard errors of minerals measured from the compact shoulder roast, eye of shoulder, knuckle, loin and topside sampled from carcases of lambs produced in extensive systems. Mineral (mg/ 100 g muscle)
Compact shoulder roast
Eye of shoulder
Loin
Knuckle
Topside
S. E. M.
Iron Phosphorus Potassium Selenium Sodium Zinc
1.3a 171.6b 316.8b 15.2a 58.0c 4.2c
1.4a 155.4a 288.9a 14.4a 54.7bc 4.5c
2.12c 221.3d 411.0d 18.6b 51.0a 2.9a
1.8b 202.9c 369.9c 18.5b 62.3d 4.9d
2.2c 231.9d 390.6 cd 17.8b 53.6ab 3.5b
0.1 7.6 12.3 2.8 2.3 0.2
Different letters within the same row denote significance between means (P < .05). All weights are on a fresh muscle basis.
between cuts from the same location on the carcase as the knuckle and topside (leg cuts) had 53.6 mg/100 g and 52 mg/100 g respectively while the compact shoulder roast and eye of shoulder (shoulder cuts) had 108.9 mg/100 g and 117.3 mg/100 g, respectively. 3.3. Mineral composition Iron was significantly higher in the loin (2.1 mg/100 g) and the topside (2.2 mg/100 g), yet the zinc concentration was lowest in the loin (2.9 mg/100 g) and significantly higher in all other cuts, with the knuckle containing the highest concentration (4.9 mg/100 g; Table 3). The CSR and eye of shoulder had consistently lower content of most minerals including, phosphorus, potassium, selenium and sodium, while the loin contained the highest concentration of phosphorus and potassium (Table 3). 4. Discussion
4.2. Fatty acid composition
4.1. Proximate composition
Differences between the main fatty acid groups between muscles agree with the results of Fowler et al. (2015) and Angood et al. (2008) that show as the total fat increased, the concentrations of MUFA and SFA increased, yet there was a lesser effect on the PUFAs. This is evident in the current study as the loin which contained the lowest fat content also contained the lowest concentrations of SFA and MUFA. In contrast, the compact shoulder roast yielded the highest fat content and contained the highest content of SFA and MUFA. Yet the PUFA content did not vary between the loin, knuckle and topside. Consequently, there was a significant difference in the ratio of saturated to polyunsaturated fatty acids between cuts which were derived from the shoulder compared to those from the leg and the loin. While many studies have considered the impact of intensive and extensive production systems and supplementation on the fatty acid composition of the loin (Atti & Mahouachi, 2009; Bessa, Lourenço, Portugal, & Santos-Silva, 2008; Kitessa et al., 2009; Ponnampalam et al., 2014; Ponnampalam, Burnett, Norng, Warner, & Jacobs, 2012), there is an absence of research assessing the variability between individual fatty acids between different cuts from the same carcase. A review by Bas and Morand-Fehr (2000) highlights the variation in fatty acid composition which occurs between fat depots of lambs, showing that SFAs including C14:0, C16:0 and C18:0 as well as MUFAs including C16:1 and C18:1 varied between fat depots and intramuscular fat. Therefore, it is plausible part of the variation in fatty acids may be attributed to differences in the composition of intermuscular fat included in shoulder cuts and intramuscular fat included in cuts such as the knuckle, topside and loin. Thus, length of feeding may have a bigger impact on the fatty acid composition of shoulder lamb cuts (Bessa et al., 2008) as it is probable the fatty acid composition of cuts which contain adipose tissue and intermuscular fat of such cuts can be altered by increasing fat levels associated with longer feeding periods (Borys, Borys,
The protein and energy content found in this study are consistent with figures previously reported for lamb cuts in Australia (Ponnampalam, Giri, Pethick, & Hopkins, 2014; Williams, Droulez, Levy, & Stobaus, 2007) and South Africa (Hoffman, Muller, Cloete, & Schmidt, 2003). It is plausible that change in diet, both quality and feeding intensity, is able to describe some of the variation in protein content between cuts given that lambs sampled later in the growing season may have been on a slower growth rate altering protein accretion and turnover (Millward, 2005), as the temperate pastures commonly used to finish lambs in southern Australia decline in quality and herbage over spring and summer until autumn-break rainfall (Burnett, Seymour, Norng, Jacobs, & Ponnampalam, 2012). Yet all muscles do not respond to diet at a constant rate, as the rates of protein accretion and degradation vary between muscles when dietary protein is limited (Chang & Wei, 2005) a result of fibre types, given that protein turnover varies with muscle fibre type (Therkildsen & Oksbjerg, 2009). Furthermore, muscle architecture including the number of muscle fibres and the proportion of connective tissue differs between muscles of the fore and hindquarter included in the cuts (Aalhus, Robertson, & Ye, 2009), which may also contribute to the difference in protein of cuts measured. The fat content of the shoulder cuts was greater than figures previously reported for Australian lamb as many studies have reported figures of approximately 4.5% (Fowler, Ponnampalam, Schmidt, Wynn, & Hopkins, 2015; Pannier, Pethick, Geesink, et al., 2014c; Pannier, Pethick, Boyce, et al., 2014b; Williams et al., 2007). This is considered to be the result of the anatomy of the cuts as shoulder cuts, such as the compact shoulder roast, include several muscles and therefore include contributions of intermuscular fat content which is not included in cuts 129
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highlights the difference in zinc levels between US quality grades and the country of origin suggesting that the level of minerals such as zinc found in the soil and therefore plants grazed by the lambs effects the muscle deposition. Thus, the significance of month in determining the content of minerals may reflect the abattoir sourcing lambs from different regions as seasonal conditions and rainfall change the quality of pastures. Therefore, lambs reach slaughter weights at various times depending on the local conditions. Iron levels in retail cuts from grass fed lambs significantly differed between cuts with the topside and loin containing nearly twice the iron levels of the shoulder cuts, compact shoulder roast and eye of shoulder. This disagrees with the findings of Lin et al. (1988) that no significant difference in iron levels was evident in retail cuts from either US or New Zealand lamb carcases. Other studies which have been completed on the loin demonstrate that the average iron levels for Australian lamb loin are approximately 2 mg/100 g meat (Mortimer et al., 2014; Pannier et al., 2010; Pannier, Gardner, Pearce, et al., 2014a; Williams et al., 2007). Although it is similar to iron levels in lamb carcases from the US (Lin et al., 1988), this level is higher than those reported for lamb carcases from South Africa (Hoffman et al., 2003) and New Zealand (Lin et al., 1988). Overall, these studies highlight that variation in iron levels of the loin between carcases is due to oxidative fibre type, age, geographic location, year, sex, genetics, breed, birth type, kill group, carcase weight, C site fat depth and intramuscular fat (Hoffman et al., 2003; Lin et al., 1988; Mortimer et al., 2014; Pannier et al., 2010; Pannier, Gardner, Pearce, et al., 2014a). Consequently, as with zinc levels, the most plausible explanation for differences between retail cuts from the same lamb carcases is likely to be differences in oxidative muscle fibre types due to variation in vascularity, anatomical location and function which results in red oxidative muscle fibre types also containing more iron as well as zinc (Lin et al., 1988; Pannier, Gardner, Pearce, et al., 2014a). However, it is unclear how the higher levels of fat in the shoulder cuts affect the iron content, as Pannier, Gardner, Pearce, et al. (2014a) demonstrate that increasing intramuscular fat is associated with decreasing levels of myoglobin and ICDH, therefore decreasing iron content. Given the paucity of research which has been completed on the differences between mineral levels of lamb cuts it is difficult to determine whether the causes of inter-animal variation also create intra-animal variation in mineral composition.
Oprzadek, & Przegalinska-Goraczkowska, 2011). This is particularly relevant for the increases found in C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C18:1n-7 and C18:1n-9t and C18:1n-7t as they are mainly present in triglycerides which increase with increasing fatness (Enser et al., 1998; te Pas, Everts, & Haagsman, 2004). Enser et al. (1998) are in agreeance indicating total identified fatty acids significantly differed between the m. triceps brachii, m. longissimus thoracis et lumborum, and m. gluetobiceps of carcases from grass fed lambs due to only some of the fatty acids; C18:0, C16:0, C18:1n-7, C18:2n-6, C18:3n-6 and C18:3n-3, C20:4n-6, C20:4n3, C20:5n3, C22:5n3 and C22:6n-3. This was the result of muscle fibre type as the content of phospholipids is highest in the red oxidative muscle fibres (Enser et al., 1998). However, as no muscle fibre typing was conducted it is difficult to determine whether this is the cause of the differences observed in the current study. Thus, research is required to determine the impact of muscle fibre types on the nutritive value of lamb cuts given that leg and shoulder cuts are expected to vary in muscle fibre type (te Pas et al., 2004) and genetic selection can alter the fibre types of muscles (Kelman, Pannier, Pethick, & Gardner, 2014). Furthermore, this highlights the need to determine the nutritional information for specific cuts rather than portions of the carcase such as the forequarter, rack and leg to ensure accuracy of figures reported. 4.3. Mineral composition While research has been conducted on the mineral composition of Australian lamb, it has focused on the loin (Mortimer et al., 2014; Pannier et al., 2010; Pearce et al., 2009), consequently little research has been conducted on other cuts, including those from the leg and forequarter. The concentration of zinc was significantly higher in the leg and forequarter cuts, with some cuts such as knuckle containing nearly double the zinc content of the loin. This agrees with the findings of Lin et al. (1988) that significant differences in the mineral composition occurred between retail cuts with the greatest zinc levels in the blade chop and foreshank and the lowest levels in the loin. Similarly, the levels of zinc found in the current study for the loin are similar to the average levels of approximately 2 mg/100 g of meat previously reported (Hoffman et al., 2003; Mortimer et al., 2014; Pannier et al., 2010; Pannier, Gardner, Pearce, et al., 2014a). Thus, it is hypothesised that the differences in zinc content are due to differences in muscle fibre type as a difference in the mineral levels of red and white muscle fibres has been associated with differences in vascularity, function and anatomical location with more red muscle fibre types containing more zinc (Lin et al., 1988; Pannier, Gardner, Pearce, et al., 2014a; Pearce et al., 2009). Pannier, Gardner, Pearce, et al. (2014a) suggested that these differences may be due to a higher content of myoglobin, increased vascularisation and more mitochondria which are all associated with increased oxidative capacity, as both myoglobin and isocitrate dehyrdogenase (ICDH) had a positive association with zinc content. This resulted in an increase of 0.30 mg/100 g of zinc across the 2–12.5 mg/100 g range in myoglobin levels and a 0.30 mg/100 g increase in the level of zinc across the 2–9 μmol range of ICDH. However, these findings describe differences between mineral contents of lamb loin from different carcases with varying genetic backgrounds and selection for lean growth has been shown to increase the proportion of glycolytic type IIX muscle fibres (Greenwood, Harden, & Hopkins, 2007; Pannier, Gardner, Pearce, et al., 2014a). Therefore, further research is required to determine the influence of muscle fibre type on the variation of mineral composition of lamb cuts from the same carcase. Pannier, Gardner, Pearce, et al. (2014a) highlighted the effect of production location as zinc content was influenced by site and year with lambs from Trangie containing 0.54 mg/100 g more than lambs from Rutherglen and lambs slaughtered in 2008 had a higher concentration of zinc. Similarly, the study conducted by Lin et al. (1988)
4.4. Relevance to human nutrition While this study reports significant differences between retail lamb cuts for most nutritional composition traits, differences between what is significant in terms of results do not always correlate with what is significant in terms of human health as changes to the nutritional values of meat within a recommended serve of meat can be low (Lin et al., 1988). Thus, it is important to consider the implications of the results found in this study with the current nutritional guidelines. As outlined by Food Standards Australia New Zealand (2012), nutritional claims cannot be made about PUFA without giving consideration to the total FA composition. Subsequently, to be claimed as a high source of PUFA, the total of SFA and trans fatty acid can comprise no > 28% of the total fatty acid content of the food and the food must contain 40% of the total fatty acid as PUFA (Food Standards Australia New Zealand, 2012). As the percentage of PUFA is relatively low in lamb retail cuts, the current study indicates that none of the lamb cuts measured meet the requirements for a dietary claim of being high in PUFA. Similarly, claims about the Omega-3 fatty acid content of a food also take into consideration the total fatty acid content as the food must contain no more that 28% of its total fatty acid content as SFA or trans FA or the food must not contain over 5 g of total SFA and trans fatty acids. Furthermore, the food must contain at least 200 mg of αLinolenic acid (ALA) per serving or 30 mg total EPA and DHA per serving to be considered a source while to be considered a good source of 130
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5. Conclusion
Omega-3 FA, the food must contain at least 60 mg of EPA and DHA per serving (Food Standards Australia New Zealand, 2012). Based on the data from this study, the knuckle, topside and loin all meet the nutritional requirements to be called a source of Omega-3 FA as they contain under 5 g/100 g of SFA and over 30 mg/100 g of EPA and DHA and consequently meet the nutritional guidelines per standard serve which consists of 135 g. Although the shoulder cuts also contain over 30 mg/ 100 g of EPA and DHA, their SFA content prohibits the claim being made about the eye of shoulder and compact shoulder roast. For claims that a food is a source of minerals, the food must contain at least 10% of the RDI per serve, while for claims that the food is a good source of minerals it must contain at least 25% of the RDI (Food Standards Australia New Zealand, 2012). Given that the RDI for iron is 8 mg/day for men and older women, to be a source for men and older women (National Health and Medical Research Council, 2006), 0.8 mg/ 100 g is required, while to be a good source 2 mg/100 g is required. However, for younger women, the RDI is 18 mg/day and this goes up to 27 mg/day for pregnant women. Thus, 1.8 g/100 g and 2.7 mg/100 g are required to be a source of iron while 4.5 mg/100 g and 6.75 mg/ 100 g are required to be a good source of iron for young women and pregnant women, respectively. Consequently, all retail lamb cuts measured can be deemed a good source of iron for men and older women and a source for young women, while the eye of shoulder and knuckle can be considered a good source for younger women. Similarly, for claims that a food is a source of zinc, the food needs to contain 10% of the RDI of 14 mg/day for men, 8 mg/day for women and 11 mg/day for pregnant women (National Health and Medical Research Council, 2006; Food Standards Australia New Zealand, 2012). This equates to zinc contents of 1.4 mg/100 g for men, 0.8 mg/100 g for women and 1.1 mg/100 g for pregnant women. However, to be labelled as a good source of zinc, there must be 25% of the RDI available which equates to 3.5 mg/100 g for men, 2 mg/100 g for women and 2.75 mg/ 100 g for pregnant women. Consequently, all cuts could be considered as a good source of zinc for women and pregnant women, while the loin can be considered a source of zinc for men, all of the other retail cuts measured can be considered a good source of zinc for men. A comparison of the findings in the current study compared to those which have been given by Foods Standards Australia (Food Standards Australia New Zealand, 2010), suggests that the current nutritional tables needs to be updated with new cuts. This is particularly important for the development of new cuts as this study demonstrated that leg cuts are good sources of minerals and Omega-3 FA. However nutrition information is only available on the loin chop, easy carve shoulder and easy carve leg (Food Standards Australia New Zealand, 2010) which vary from the boned out value added cuts sampled in the current study. For example, the NUTTAB reference for the zinc content of an easy carve leg is 3.6 mg/100 g (Food Standards Australia New Zealand, 2010), while this study indicates that the value for the knuckle is 4.9 mg/100 g. Similarly, the information varies for the loin as the NUTTAB data suggests that a fully trimmed loin chop has 7.1 g/100 g fat whilst this study indicates it is only 4.5 g/100 g. While based on a serving of meat as per current nutritional guidelines, the figures reported in the current study do not consider the retention of these nutrients during cooking as they were measured on the raw product, yet a majority of domestic consumers cook lamb prior to consumption. As the retention of nutrients has been shown to vary with cut, fat content, surface area of the cut, animal age and cooking method of South African mutton and lamb (van Heerden & Strydom, 2017), further research is required to determine the impact of recommended cooking methods on the nutritional composition of these cuts to ensure that the nutritional claims are relevant per serve, as eaten. However, the nutritional values found in the current study indicate that there is potential to use such nutritional data to market cuts to specific groups, such as pregnant women and the elderly, who have greater requirements for protein and minerals such as iron and zinc.
Overall, this study indicated that there is variation between retail cuts for the nutritional composition of lamb retail cuts. However, given the paucity of research which has been conducted on retail cuts from the forequarter and leg, it is difficult to determine the reasons behind some of these differences as many studies have focused on the difference between loins. This study also demonstrated that there is an ability to promote the knuckle, topside and loin from grass fed animals as a good source of Omega-3 FA as well as most of the leg and forequarter cuts sampled as a good source of iron and zinc for most men and women. However, there is still a need to conduct further research to determine the impact of factors including season, feeding length, breed, genetics, muscle fibre type, age and gender on the nutritional composition of these cuts to ensure that nutritional claims are accurate over time. Acknowledgements The authors would like to thank Cassius Coombs, Matt Kerr (NSW DPI), Jordan Hoban (NSW DPI) and Graham Gardner (Murdoch University) for their assistance in collecting and analysing the samples. Furthermore, the authors would like to thank the Sheep CRC for funding the research. References Aalhus, J., Robertson, W. M., & Ye, J. (2009). Muscle fiber characteristics and their relationship to meat quality. In M. Du, & R. Mccormick (Eds.). Applied muscle biology and meat science. United States of America: Taylor and Francis. Abbaspour, N., Hurrell, R., & Kelishadi, R. (2014). Review on iron and its importance for human health. Journal of Research in Medical Sciences: The Official Journal of Isfahan University of Medical Sciences, 19, 164–174. Angood, K. M., Wood, J. D., Nute, G. R., Whittington, F. M., Hughes, S. I., & Sheard, P. R. (2008). A comparison of organic and conventionally-produced lamb purchased from three major UK supermarkets: Price, eating quality and fatty acid composition. Meat Science, 78, 176–184. Anon (2017). In HEALTH (Ed.). Australia New Zealand food standards code standard 1.2.7 – Nutrition, health and related claims. Anonymous (2005). Handbook of Australian meat. Brisbane, Australia: AUS-MEAT Limited. AOAC (1992). AOAC official method 991.36 fat (crude) in meat and meat products. 289. Atti, N., & Mahouachi, M. (2009). Effects of feeding system and nitrogen source on lamb growth, meat characteristics and fatty acid composition. Meat Science, 81, 344–348. Bas, P., & Morand-Fehr, P. (2000). Effect of nutritional factors on fatty acid composition of lamb fat deposits. Livestock Production Science, 64, 61–79. Bessa, R. J. B., Lourenço, M., Portugal, P. V., & Santos-Silva, J. (2008). Effects of previous diet and duration of soybean oil supplementation on light lambs carcass composition, meat quality and fatty acid composition. Meat Science, 80, 1100–1105. Borys, B., Borys, A., Oprzadek, J., & Przegalinska-Goraczkowska, M. (2011). Effect of sex and fattening intensity on health-promoting value of lamb meat. Animal Science Papers and Reports, 29. Burnett, V. F., Seymour, G. R., Norng, S., Jacobs, J. L., & Ponnampalam, E. N. (2012). Lamb growth performance and carcass weight from rotationally grazed perennial pasture systems compared with annual pasture systems with supplements. Animal Production Science, 52, 248–254. Carrilho, E. N. V. M., Gonzalez, M. H., Nogueira, A. R. A., Cruz, G. M., & Nóbrega, J. A. (2002). Microwave-assisted acid decomposition of animal- and plant-derived samples for element analysis. Journal of Agricultural and Food Chemistry, 50, 4164–4168. Chang, Y.-M., & Wei, H.-W. (2005). The effects of dietary lysine deficiency on muscle protein turnover in Postweanling pigs. Asian-Australasian Journal of Animal Sciences, 18, 1326–1335. Cunnane, S. C. (2004). Metabolic and health implications of moderate ketosis and the ketogenic diet. Prostaglandins, Leukotrienes and Essential Fatty Acids, 70, 233–234. Enser, M., Hallett, K. G., Hewett, B., Fursey, G. A. J., Wood, J. D., & Harrington, G. (1998). Fatty acid content and composition of UK beef and lamb muscle in relation to production system and implications for human nutrition. Meat Science, 49, 329–341. Font-i-Furnols, M., & Guerrero, L. (2014). Consumer preference, behavior and perception about meat and meat products: An overview. Meat Science, 98, 361–371. Food Standards Australia New Zealand (2010). Nutritient tables for use in Australia (NUTTAB). Food Standards Australia New Zealand (2012). Nutrition information user guide. Fowler, S. M., Hoban, J. M., van de Ven, R., Gardner, G., Pethick, D. W., & Hopkins, D. L. (2017). The effect of lamb carcase weight and GR depth on the production of valueadded cuts – A short communication. Meat Science, 131, 139–141. Fowler, S. M., Ponnampalam, E. N., Schmidt, H., Wynn, P., & Hopkins, D. L. (2015). Prediction of intramuscular fat content and major fatty acid groups of lamb M.
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