Effects of dietary fat sources on the intramuscular and subcutaneous adipose tissue fatty acid composition, and consumer acceptability of lamb.

BACKGROUND: Lamb diets can alter the fatty acid (FA) profile of muscle and adipose tissue, which may affect the sensory quality and consumer acceptability of the meat. In this study, lambs received one of four pre-slaughter diets: a barley / maize / soya-based concentrate (C), supplemented with a saturated fat source (Megalac®) (SAT), or supplemented with protected linseed oil (PLO); or a by-product (citrus pulp / distillers' grain / soya-based) diet (BPR). Intramuscular FAs and adipose tissue branched-chain FAs were measured and consumer evaluation (hedonic liking and attribute intensity) was undertaken with cooked lamb. RESULTS: Compared to the other diets, the BPR diet resulted in a higher muscle concentration and a greater proportion of C18:2n-6, and greater proportions of conjugated linoleic acid (c9,t11-C18:2) and n-6 polyunsaturated FAs (PUFA), whereas the PLO diet resulted in higher muscle proportions of C18:0 and saturated FAs, higher concentrations of C18:3n-3 and n-3 PUFA, and a lower n-6 to n-3 ratio. The consumer acceptability of lamb was not affected by the pre-slaughter diets. CONCLUSION: Changes in the FA profile of lamb muscle and adipose tissue through the inclusion of sources of saturated fat, protected linseed oil, or by-products in the pre-slaughter diet did not result in consumer detection of significant effects on the acceptability of the cooked meat. © 2020 Society of Chemical Industry.

Temperature variation effects on the determination of acidity constants through the internal standard-capillary electrophoresis method.

The internal standard (IS) CE (IS-CE) method is an interesting alternative to other methods for the determination of acidity constants of compounds. Although some of the advantages of this method have been already reported, the method has not been tested yet as regards to temperature effects. This has been the aim of this work, where it is demonstrated that the method can be applied successfully for the determination of pK(a) s at different temperatures, if the acidity constant of the IS at the desired temperature is known. The fact of obtaining the acidity constants at different temperatures allows the calculation of some thermodynamic quantities, such as the molar standard enthalpy and the molar standard entropy in a fast way. It is also demonstrated that if the IS and the test compound have similar standard enthalpy increment, the IS compensates uncontrolled possible temperature fluctuations (e.g., due to Joule heat) inside the capillary obtaining reliable acidity constant values at the desired temperature.

Effect of dietary pomegranate by-product on lamb flavour.

This study evaluated the effect of the dietary inclusion of whole pomegranate by-product (WPB) on lamb flavour. Seventeen Comisana male lambs (body weight 14.82 kg ± 2 kg) were assigned to 2 treatments. During 36-day feeding trial, the control group (n = 8) received a conventional concentrate diet; the other group (n = 9) received a concentrate diet containing 200 g/kg (dry matter) of WPB, replacing part of barley and corn. After slaughter, fatty acids were determined in raw meat, while volatile organic compounds, SMart nose, and sensory traits were analysed in cooked meat. The concentrations of total polyunsaturated fatty acids, vaccenic and rumenic acid were higher in WPB meat. Most of volatile compounds that arise from lipid degradation (i.e., aldehydes, alcohols, ketones, and hydrocarbons) were found at higher concentrations in the WPB meat than in the control, except for 2-pentanone that was greater in control meat. Although SMart nose clearly discriminated between dietary treatments, consumer panel did not detect differences in meat flavour.

Validation of a Rapid Microwave-Assisted Extraction Method and GC-FID Quantification of Total Branched Chain Fatty Acids in Lamb Subcutaneous Adipose Tissue.

A rapid microwave-assisted extraction and derivatization of three branched chain fatty acids (BCFA): 4-methyloctanoic acid (MOA), 4-ethyloctanoic acid (EOA) and 4-methylnonanoic acid (MNA) from subcutaneous adipose tissue (SAT) of lamb was developed and validated. Linearity was excellent (R2 > 0.99), and the limits of detection and quantification (µg/mL) were between 0.03 to 0.05 and 0.04 to 0.06, respectively. The relative response factors were 0.9416, 1.2840, and 1.0370 determined with high precision (RSD: 5.8%, 6.7%, and 5.9%) for MOA, EOA, and MNA, respectively. The accuracy, recoveries and matrix effect were 92.5% to 108.3%, 103.1% to 103.8%, and 89.3% to 101.9%, respectively. Analysis of 24 SAT samples can be done in under 4 hr. The levels of total BCFA in SAT of lambs were in good agreement with levels found in literature using more time-consuming method. PRACTICAL APPLICATION: Microwave-assisted preparation and quantification of branched chain fatty acids (BCFA) in lamb subcutaneous adipose tissue (SAT) was developed and validated. This method requires the use of less toxic chemicals and a relatively higher number of samples can be analyzed in a short period of time in comparison to established methods of fatty acid analysis. The validated method met the internationally accepted standards, and the BCFA levels in lamb SAT were consistent with published values; consequently, the method can be used for future analyses.

Effect of finishing diet and duration on the sensory quality and volatile profile of lamb meat.

Animal production factors can affect the sensory quality of lamb meat. The study investigated the effect of diet composition and duration of consumption on the proximate analysis, volatile profile and sensory quality of lamb meat. Ninety-nine male Texel × Scottish Blackface lambs were raised at pasture for 10 months before being assigned in groups of 11 to one of the following treatments: 100% Silage (S) for 36 (S36), 54 (S54) or 72 (S72) days; 50% Silage - 50% Concentrate (SC) for 36 (SC36), 54 (SC54) or 72 (SC72) days; 100% Concentrate (C) for 36 (C36) or 54 (C54) or 72 (C72) days. A trained sensory panel found Intensity of Lamb Aroma, Dry Aftertaste and Astringent Aftertaste to be higher in meat from lambs on the concentrate diet. Discriminant analysis showed that the volatile profile enabled discrimination of lamb based on dietary treatment but the volatile differences were insufficient to impact highly on sensory quality. Muscle from animals in the S54 group had higher Manure/Faecal Aroma and Woolly Aroma than the SC54 and C54 groups, possibly related to higher levels of indole and skatole. Further research is required to establish if these small differences would influence consumer acceptability.

Volatile Profile of Grilled Lamb as Affected by Castration and Age at Slaughter in Two Breeds.

The aim of this study was to assess the effect of castration and slaughter age on the volatile profile of cooked meat from Scottish Blackface (SB) and Texel × Scottish Blackface (T × SB) lambs. M. longissimus thoracis et lumborum was sampled at slaughter and subjected to volatile analysis by SPME-GC-MS. Rams had higher relative proportions, expressed as relative abundance (RA), in lipid oxidation products while castrates had higher RA in pyrazines and benzenoid compounds. There was no consistent age effect on the RA of volatiles, although rams in November and January had a different volatile profile to castrates. There were higher proportions of free branched-chain fatty acids in muscle from SB compared to T × SB lambs. Overall, the results showed that production factors affected the volatile profile of cooked lamb meat which may explain differences in lamb flavor. PRACTICAL APPLICATION: Lamb meat has a characteristic flavor which, according to the evidence to date, may be influenced by farm production factors like gender or slaughter age. Our results showed variations in the proportions of some flavor compounds in cooked lamb between rams and castrated lambs while an increase in slaughter age did not have a consistent effect on proportions of compounds.

Fatty acids and oxidative stability of meat from lambs fed carob-containing diets.

Male Comisana lambs were individually stalled and, for 56 days, were fed concentrates with 60% barley (n = 8 lambs), or concentrates in which barley was partially replaced by 24% or 35% carob pulp (n = 9 lambs in each group). The intramuscular fatty acids were analyzed and the color stability, lipid and protein oxidation were measured in fresh meat overwrapped with polyvinyl chloride film at 0, 3 or 6 days of storage at 4 °C in the dark. Carob pulp increased the concentration of polyunsaturated fatty acids (PUFA) in muscle, including the rumenic acid (P < 0.01), and reduced the saturated fatty acids (P < 0.01) and the n-6/n-3 PUFA ratio (P = 0.01). The meat did not undergo extensive oxidative deterioration and the diet did not affect the oxidative stability parameters. Therefore, carob in lamb diet could increase PUFA in muscle without compromising meat oxidative stability.

Dietary citrus pulp improves protein stability in lamb meat stored under aerobic conditions.

The antioxidant effects of dried citrus pulp on proteins in lamb meat, when used as a replacement of concentrate in the feed, was studied using meat from 26 male Comisana lambs. The lambs of age 90 days had been grouped randomly to receive one of the three dietary treatments: (1) commercial concentrate with 60% barley (Control, n=8), (2) concentrate with 35% barley and 24% citrus pulp (Cp24, n=9), or (3) concentrate with 23% barley and 35% citrus pulp (Cp35, n=9). Slices from the longissimus thoracis et lomborum muscle were packed aerobically and stored for up to 6days at 4°C in the dark. The citrus pulp groups, Cp24 and Cp35, significantly decreased protein radicals and carbonyls, and preserved more thiols within six days of storage compared to the Control group. The citrus pulp groups significantly slowed down the rate of protein oxidation, indicating that dietary citrus pulp reduced oxidative changes in meat proteins.