4-methylnonanoic Acid Research Articles

Update to RIFM fragrance ingredient safety assessment, 4-methylnonanoic acid, CAS Registry Number 45019-28-1

Update to RIFM fragrance ingredient safety assessment, 4-methylnonanoic acid, CAS Registry Number 45019-28-1

Effects of Allium mongolicum Regel ethanol extract on three flavor-related rumen branched-chain fatty acids, rumen fermentation and rumen bacteria in lambs.

The objective of this study was to evaluate the effect of Allium mongolicum Regel ethanol extract (AME) on the concentration of three branched-chain fatty acids (BCFAs) related to flavor, fermentation parameters and the bacteria and their correlations in the rumen of lambs. A total of thirty 3-month-old male, Small-tailed Han sheep (33.60 ± 1.23 kg) were randomly distributed into 2 groups as follows: control group (CON) was fed a basal diet and AME group was fed a basal diet supplemented with 2.8 g⋅lamb–1⋅d–1 A. mongolicum Regel ethanol extract. AME supplementation decreased (P = 0.022) 4-methyloctanoic acid (MOA) content and tended to lower (P = 0.055) 4-methylnonanoic acid (MNA) content in the rumen. Compared to CON group, the ruminal concentrations of valerate and isovalerate were higher (P = 0.046 and P = 0.024, respectively), and propionate was lower (P = 0.020) in the AME group. At the phylum level, the AME group had a lower abundance of Bacteroidetes (P = 0.014) and a higher abundance of Firmicutes (P = 0.020) than the CON group. At the genus level, the relative abundances of Prevotella (P = 0.001), Christensenellaceae_R-7_group (P = 0.003), Succiniclasticum (P = 0.004), and Selenomonas (P = 0.001) were significantly lower in the AME group than in the CON group, while the relative abundances of Ruminococcus (P < 0.001), Quinella (P = 0.013), and Lachnospiraceae_XPB1014_group (P = 0.001) were significantly higher. The relative abundances of Prevotella (P = 0.029, R = 0.685; P = 0.009, R = 0.770), Christensenellaceae_R-7_group (P = 0.019, R = 0.721; P = 0.029, R = 0.685), and Succiniclasticum (P = 0.002, R = 0.842; P = 0.001, R = 0.879) was positively correlated with MOA and MNA levels, and the relative abundance of Lachnospiraceae_XPB1014_group (P = 0.033, R = −0.673) was negatively correlated with MOA. The relative abundance of Christensenellaceae_R-7_group (P = 0.014, R = −0.744) and Prevotellaceae_UCG-003 (P = 0.023, R = −0.706) correlated negatively with the EOA content. In conclusion, these findings suggest that the AME affected the concentration of BCFAs, fermentation parameters and the rumen bacteria in the rumen of lambs.

Transcriptome analysis reveals candidate genes of the synthesis of branched-chain fatty acids related to mutton flavor in the lamb liver using Allium mongolicum Regel extract.

The objective of this study was to identify candidate genes via which Allium mongolicum Regel ethanol extract (AME) affects the synthesis of branched-chain fatty acids (BCFAs) related to mutton flavor by transcriptome analysis in the lamb liver. Thirty male Small-tailed Han sheep (3 mo old; 33.6 ± 1.2 kg) were randomly divided into two groups and fed for 75 d with a basal diet containing no AME (CON, control group) or 2.8 g·lamb−1·d−1 AME (AME group). Twelve sheep, CON (n = 6) and AME (n = 6), were selected for slaughter at the end of the trial period, and liver samples were subsequently collected. There was no difference in 4-ethyloctanoic acid content among treatments. The 4-methyloctanoic acid and 4-methylnonanoic acid levels were significantly lower in the AME group than in the CON group (P < 0.05). Furthermore, 461 differentially expressed genes (DEGs) were identified between the CON and AME groups, of which 182 were upregulated and 279 were downregulated in the AME group. The DEGs were enriched in three pathways, namely, glutathione metabolism, ECM–receptor interaction, and steroid hormone biosynthesis, as determined by the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Finally, CYP2B6, ACOT12, THEM4, ACSF2, LPIN1, and ADCY4 were identified as candidate genes that might be involved in regulating the BCFAs synthesis in the sheep liver.

Comparison and analysis on sheep meat quality and flavor under pasture-based fattening contrast to intensive pasture-based feeding system

ObjectiveThe objective of this study was to investigate the effect of 4-month intensive feeding on the meat quality, fatty acid profile, flavor, and growth performance of grazing Hulunbuir sheep (HBS).MethodsThe HBS were selected 4-months after birth in a pasture rearing system as the experimental animals (n = 44, female, average body weight 23.8±2.2 kg) then divided equally into pasture-based grazing fattening (PAS) and concentrate-included intensive fattening (CON) groups for another 4-month finishing. When finished fattening, all animals were slaughtered to collect musculus longissimus dorsi subcutaneous adipose tissue and to investigate the influences on meat quality, fatty acid profile, flavor and growth performance.ResultsThe results showed lambs in CON group got significantly higher live weight, hot carcass weight, and dressing percentage. The CON group had significantly higher value of redness (a*), lightness (L*) and water holding capacity (p<0.05), significantly lower value of Warner-Bratzler shear force than the PAS group (p<0.05). The subcutaneous fat from CON group lambs demonstrated a significantly higher content of C18:1 and C18:2 (p<0.05), but lower C14:0 and C16:0, indicating an increased degree of unsaturated fatty acid. The content of 4-methyloctanoic acid, 4-ethyloctanoic acid and 4-methylnonanoic acid had increased 2 to 4 times, representing a more intense odor in the CON group. However, the values were still lower than most sheep breeds reported, indicating the indoor feeding system could not fundamentally deteriorate the excellent meat characteristic of HBS.ConclusionIt was evident that lambs in CON group exhibited a better meat production performance, improved in meat color, texture and healthier fatty acid profile through pasture-weaned concentrate included intensive fattening system, which offers a good alternative regimen for lamb finishing and has a wide prospection in the HBS meat industry.

Effects of silage to concentrate ratio and duration of feeding on the fatty acid composition of ovine muscle and adipose tissue

Context Dietary strategies may influence the fatty acid composition of sheep meat and ultimately its nutritional and sensory quality. Aim This study investigated the effects of silage to concentrate ratio and feeding duration on the concentration of intramuscular fatty acids and branched chain fatty acid in subcutaneous adipose tissue of lambs. Methods Pasture fed lambs were assigned in groups of 11 to one of nine dietary treatments consisting of silage to cereal concentrate at ratios (dry matter basis) of 100:0 (silage), 50:50 (silage:concentrate) or 0:100 (concentrate) for three feeding durations (36, 54 or 72 days) pre-slaughter. A 10th group of 11 lambs remained at pasture until slaughter. Fatty acid methyl esters were prepared using a microwave-assisted method and quantified by gas chromatography with flame ionisation detection. Results The concentration of n-3 polyunsaturated fatty acids (PUFA) and proportions of C18:3n-3 and C18:2 cis-9 trans-11 decreased for mixed feed and/or concentrate treatments, but not for silage, from 36 to 72 days. The C18:2n-6 and n-6 PUFA concentrations increased for mixed feed and concentrate, but not for silage, from 36 to 72 days. The animals that remained at pasture had lower C18:2n-6 and n-6 PUFA than those receiving mixed feed for 72 days, concentrate for 54 days and concentrate for 72 days, but higher C18:3n-3, C18:2 cis-9 trans-11 and n-3 PUFA concentrations than the indoor finishing groups. The n-6/n-3 PUFA ratio was lower in pastured lambs compared to the other groups. 4-Methyloctanoic acid and 4-ethyloctanoic acid were higher in concentrate and mixed feed treatments than in silage while 4-methylnonanoic acid increased with increase in concentrate level in the diet. Conclusion The ratio of silage to concentrate in the diet and duration of feeding pre-slaughter influence the fatty acid composition of muscle and subcutaneous adipose tissue of lambs. Implications The results are important for lamb producers in understanding the nutritional and sensory implications of altering lamb diets.

Effect of dietary supplementation with Allium mongolicum Regel extracts on growth performance, carcass characteristics, and the fat color and flavor-related branched-chain fatty acids concentration in ram lambs.

ObjectiveThis study aimed to investigate the effect of dietary supplementation with Allium mongolicum Regel extracts on the growth performance, carcass characteristics, fat color, and concentrations of three branched-chain fatty acids related to flavor in ram lambs.MethodsSixty 3-month-old, male, small-tailed Han sheep were selected and randomly allocated into four groups in a randomized block design. Four feeding treatments were used: i) a basal diet without supplementation as the control group (CK); ii) the basal diet supplemented with 10 g/lamb/d Allium mongolicum Regel powder as the AMR group; iii) the basal diet supplemented with 3.4 g/lamb/d Allium mongolicum Regel water extract as the AWE group; and iv) the basal diet supplemented with 2.8 g/lamb/d Allium mongolicum Regel ethanol extract as the AFE group.ResultsThe results demonstrated that the dry matter intake was lower for the AFE group than that in other groups (p = 0.001). The feed conversion ratio was greater for the AFE than that in other groups (p = 0.039). Dietary supplementation with Allium mongolicum Regel powder and its extracts decreased the concentrations of 4-methyloctanoic acid (MOA) (p<0.001), 4-ethyloctanoic acid (EOA) (p<0.001), and 4-methylnonanoic acid (MNA) (p = 0.044) in perirenal adipose tissue compared to those observed in the CK lambs. Dietary supplementation with Allium mongolicum Regel powder and its extracts decreased the concentrations of MOA (p<0.001) and EOA (p<0.001) in dorsal subcutaneous adipose tissue compared to those in the CK lambs. The concentrations of MOA (p<0.001) and EOA (p = 0.002) in omental adipose tissue were significantly affected by treatment, although there was a tendency for lower MNA (p = 0.062) in AMR, AWE, and AFE lambs than that in CK lambs.ConclusionThis study demonstrated that Allium mongolicum Regel and its extracts could significantly promote feed efficiency, although dry matter intake decreased and could decrease the MOA and EOA concentrations related to characteristic flavor and odor of body fat in lambs, except for tail adipose tissue.

Characterization of Four Alkyl-branched Fatty Acids as Methyl, Ethyl, Propyl, and Butyl Esters Using Gas Chromatography-Quadrupole Time of Flight Mass Spectrometry.

Branched fatty chain fatty acids (BCFAs) are associated with the "mutton flavor" found with the aroma resulting from cooked older sheep meat with three BCFAs, 4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4-methylnonanoic (MNA) acids as the main compounds responsible for "mutton flavor". Usually, BCFA analysis is done by gas chromatography (GC) with the use of quadrupole mass spectrometry (qMS) becoming predominant. 2-Butyloctanoic acid (2BO) has been used in this facility using as an internal standard to determine BCFA content in sheep fat. In this present work, GC-qMS, along with GC-quadrupole-time of flight MS (GC-QTOF-MS), have been deployed to characterize alkyl esters (as methyl, ethyl, propyl, and butyl) for MOA, EOA, MNA, and 2BO. This work presents, for the first time, the mass spectral characterization of 2BO for these alkyl esters using GC-qMS and GC-QTOF-MS.

Influence of dietary cardoon meal on volatile compounds and flavour in lamb meat

Cardoon meal is a by-product retained after oil extraction from the seeds of cultivated Cynara cardunculus var. altilis that has been proposed as a valuable resource for animal feeding. The study aimed to assess the influence of its dietary inclusion on volatile profile and flavour of meat and kidney fat from lambs. Fifteen Sarda × Comisana male lambs were randomly divided in two groups and fed for 75 days with a concentrate-based diet containing 15% cardoon meal (CMD, n = 7) or dehydrated alfalfa (CON, n = 8). Cardoon meal inclusion reduced the “barnyard/animal” odour perceived by a trained panel in kidney fat, which could be associated with the aromatic compound p-cresol (4-methylphenol), detected only in CON diet. Considering the other aroma volatiles regarded as the main contributors for the characteristic lamb flavour, both diets were characterized by moderate to low levels of 4-methyloctanoic acid, skatole and indole while 4-methylnonanoic acid and 4-ethyloctanoic acid were not detected.

Factors affecting levels of volatile 4-alkyl branched-chain fatty acids in sheep milk from 2 contrasting farming systems in New Zealand

Knowledge of factors influencing the levels of 4-alkyl branched-chain fatty acid (vBCFA), and consequently the "sheepy flavor" intensity of New Zealand sheep milk, is currently limited. In this study, we investigated the effects of 2 contrasting farming systems (fully housed/mid-lactation or pasture-grazed/late lactation) on the levels of vBCFA in sheep milk on a commercial farm in the North Island of New Zealand. Fully housed/mid-lactation ewes were housed 24 h/d and fed a total mixed ration. Pasture-grazed/late-lactation ewes were grazed 24 h/d and offered approximately 40% supplements because of poor pasture growth resulting from dry and hot climatic conditions. Any effects of genetics, age, lactation stage, feed composition, lambing date, or the environment in the housing barn or outdoors were confounded. The results obtained in this study were descriptive rather than definitive, because of the limitations of the experimental design. Levels of 4-methyloctanoic acid and 4-methylnonanoic acid in milk from fully housed/mid-lactation ewes increased during the trial period, but remained low in milk from pasture-grazed/late-lactation ewes. Levels of 4-ethyloctanoic acid in milk from the 2 groups of ewes were comparable throughout the trial. Increases in levels of 4-methyloctanoic acid and 4-methylnonanoic acid in sheep milk were associated with lactation stage and the proportion of lucerne silage fed to ewes. The level of free-form 4-ethyloctanoic acid was positively correlated with the proportion of soy meal in the diet and negatively correlated with the proportion of barley. Milk from fully housed/mid-lactation ewes had a higher flavor values than milk from pasture-grazed/late-lactation ewes because of its higher total amounts of vBCFA.

Heptadecanoic acid as an indicator of BCFA content in sheep fat

Branched chain fatty acids (BCFAs) are associated with ‘mutton flavour’ found in cooked sheep meat aroma. Three BCFAs, 4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4-methylnonanoic (MNA) acids, have been implicated as the main compounds responsible for ‘mutton flavour’. Animal age can also contribute to increasing BCFA concentration. Heptadecanoic acid (C17:0 FA) also increases with animal age in sheep. Using published data, a linear association has been found to exist between C17:0 FA with MOA and MNA in sheep fat, with C17:0 FA increasing proportionally with these two compounds. No association was found between C17:0 FA and EOA. As C17:0 FA is present in sheep fat in relatively higher proportions compared to BCFAs, it has potential to be used as a proxy for MOA and MOA as well as ‘mutton 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.

Effects of castration and slaughter age on the fatty acid composition of ovine muscle and adipose tissue from two breeds

Fatty acids (g/100 g total fatty acids) in M. longissimus thoracis et lumborum (LTL) and total branched chain fatty acids (μg/g fat) in subcutaneous adipose tissue (SAT) of rams and castrates from Scottish Blackface (SB) or Texel × Scottish Blackface (T × SB) lambs, slaughtered at mean ages of 196, 242, 293, 344 or 385 days were determined. Lambs were fed pasture prior to a 36-day finishing period on a barley/maize-based concentrate ration. The intramuscular fat content (IMF; %) was higher (P < 0.001) in castrates than in rams and in SB compared to T × SB lambs (P < 0.001). The proportions of c9-C18:1 and total monounsaturated fatty acids (MUFA) were higher (P < 0.001) in LTL of castrates than rams. The proportions of C18:2n-6 and total n-6 polyunsaturated fatty acids (PUFA) were lower (P = 0.001) in LTL of castrates compared to rams related to differences in IMF content. The proportions of C14:0, C16:0, c9-C18:1 and total MUFA were higher (P < 0.05), while the proportions of C18:2n-6, C20:4n-6, C20:5n-3, total PUFA, n-6 and n-3 PUFA were lower (P < 0.05), in SB than in T × SB lambs, which was related to differences in IMF content. There was a higher (P < 0.001) proportion of conjugated linoleic acid (CLA) c9,t11-C18:2 in LTL from SB compared to T × SB. The effects of slaughter age on the proportions of fatty acids in LTL did not show a clear trend. The concentration of 4-methylnonanoic acid was higher (P = 0.002) in SAT of rams than castrates, particularly in older lambs. Despite the differences in the muscle fatty acid composition due to gender, slaughter age or breed of lambs, the ratio of n-6/n-3 PUFA (≤3.11) was within the dietary recommendation of <4.0 for human health.

Temperature-dependent Henry's Law constants of 4-alkyl branched-chain fatty acids and 3-methylindole in an oil-air matrix and analysis of volatiles in lamb fat using selected ion flow tube mass spectrometry.

4-Alkyl branched-chain fatty acids and 3-methylindole are characteristic flavor compounds associated with sheep meat. Determining their partitioning behavior between the gas and condensed phase and ultimately developing a correlation between the compound's headspace concentration and sensory descriptive grouping are important for high-throughput characterization and grading classification. The headspace concentrations of 3-methylindole, 4-methyloctanoic acid, 4-ethyl-octanoic acid, and 4-methylnonanoic acid above corn-oil-based standard solutions and lamb fat samples were measured using selected ion flow tube-mass spectrometry (SIFT-MS). The standard solutions were equilibrated at 80, 100, 110 and 125°C while the fat samples were equilibrated at 125°C. Statistical evaluation, linear and polynomial regression analyses were performed to establish the compound-specific and temperature-dependent Henry's Law constants, enthalpy (ΔH) and entropy (ΔS) of phase changes. The Henry's Law constants (kHcp ) were calculated from the regression analysis with a high degree of confidence (p<0.05) and linearity (r2 >0.99). The kHcp increased with increase in equilibrium temperature. The empirical calculation of ΔH and ΔS at different temperatures confirmed the temperature-dependence of the Henry's Law constants. The headspace concentrations of the lamb-flavor compounds were determined above actual lamb fat samples and the corresponding condensed-phase concentrations were successfully derived. The temperature-dependent Henry's Law constants, ΔH, and ΔS of phase changes for 3-methylindole, 4-methyloctanoic acid, 4-ethyloctanoic acid, and 4-methylnonanoic acid in an air-oil matrix were empirically derived. The effectiveness of SIFT-MS for the direct, real-time, and rapid determination of key flavor compounds in lamb fat samples was established.

Gas-phase chemical ionization of 4-alkyl branched-chain carboxylic acids and 3-methylindole using H3 O+ , NO+ , and O2+ ions.

4-Methyloctanoic acid, 4-ethyloctanoic acid, 4-methylnonanoic acid, and 3-methylindole are primary contributors to the distinctive aroma and flavor of lamb meat. The reactions of H3 O+ , NO+ , and O2+ with these compounds, and identification of the product ions and their distribution, are fundamental to their characterization and rapid, real-time trace analysis using selected ion flow tube mass spectrometry (SIFT-MS). The chemical ionization of pure standards of 4-ethyloctanoic acid, 4-methyloctanoic acid, 4-ethylnonanoic acid, and 3-methylindole was carried out using the H3 O+ , NO+ , and O2+ reagent ions of a V200™ SIFT mass spectrometer. Kinetic data were calculated using the Langevin collision rate with parameterized trajectory equations. Identification of product ions, distribution, and interferences was performed by further evaluation of the pertinent ion-molecule reaction mechanisms, careful spectral analyses, and molecular mass-molecular structure pairing. The collisional capture rate constants of the reaction of the precursor ions H3 O+ , NO+ , and O2+ , their extended hydrates and the analytes, which were assumed to occur at or near the collisional rate, were all of the order of 10-9 cm3 molecule s-1 - typical for bimolecular ion-molecule reactions. Positive identification of the primary and secondary product ions, fragmented ionic species, and potential ion conflicts and interferences, from each reagent ion channel, was determined for each compound. We have established the ion chemistry involved in the ionization of the 4-alkyl branched-chain fatty acids and 3-methylindole using the precursor ions, H3 O+ , NO+ , and O2+ in SIFT-MS. The ion-molecular chemistry and the associated kinetics serve as a fundamental basis for the accurate characterization of these compounds by SIFT-MS.

Enantioseparation and optical rotation of flavor-relevant 4-alkyl-branched fatty acids

Short chain 4-alkyl-branched fatty acids are character impact compounds of the flavor of sheep and goat milk and meat. Due to their methyl or ethyl branches these volatile fatty acids are chiral, and both enantiomers are characterized by different aroma intensities. Recently, it was found that 4-methyloctanoic acid (4-Me-8:0), 4-ethyloctanoic acid (4-Et-8:0), and 4-methylnonanoic acid (4-Me-9:0) are enantiopure in goat and sheep samples, if present. Here we generated enantiopure or enantioenriched standards from racemates by means of (R)-selective esterification with lipase B and verified that 4-Me-8:0, 4-Et-8:0 and 4-Me-9:0 were (R)-enantiopure in these tissues. Determination of the optical rotation and [α]D value was carried out to show that (R)-4-Et-8:0 is dextrorotary and to verify the literature values of (R)-4-methyl-branched fatty acids. The elution order of free acids and the methyl and ethyl esters of 4-Me-8:0, 4-Et-8:0, 4-Me-9:0 and 4-methylhexanoic acid (4-Me-6:0) enantiomers was investigated on different chiral columns as well as the (−)-menthyl ester by indirect enantiomer separation on an ionic liquid phase. Different chiral recognition processes were suggested for free acid and esters of 4-Me-8:0 and 4-Me-9:0 on the one hand (decisive: 4-alkyl branch) compared to 4-Me-6:0 on the other hand (decisive: branch on antepenultimate carbon).

Concentration of three branched-chain fatty acids in adipose tissue does not affect meat sensory traits in crossbred and purebred German &amp;quot;Merinolandschaf&amp;quot; lambs

Abstract. Intense sheep odour and flavour in lamb is often associated with lower consumer acceptance. Branched-chain fatty acids (BCFAs) are suggested as possible reasons. Therefore, muscle and subcutaneous adipose tissue samples of 98 lamb chops were analysed for three BCFAs (4-methyloctanoic, 4-ethyloctanoic and 4-methylnonanoic fatty acid). Samples were derived from a previous study, in which lambs were raised and fattened under intensive conditions and tested for sensory quality. BCFA contents of fat extracts from muscle tissue were very low and quantification was not possible. In subcutaneous adipose tissue different concentrations of BCFA and differences between crosses were detected. The sex of lambs had a significant influence. The BCFA correlations were significant, while correlations between BCFA of adipose tissue and sensory traits were not significant. Therefore, it seems likely that BCFA concentrations were too low and/or other substances are involved in causing the lamb flavour detected through sensory analysis.

Physicochemical and sensory characteristics of fermented sheepmeat sausage.

The aim of the study was to compare the physicochemical and sensory characteristics of fermented, cured sausages made from equivalent muscle groups of beef, pork, and sheepmeat. The last has no commercial examples and represents an unexploited opportunity. Using seven replicates of shoulder meat and subcutaneous fat, sausages were made with 64%, 29%, 4%, 2%, 0.2%, and 0.01% of lean meat, fat, NaCl, glucose, sodium pyrophosphate, and lactic culture, respectively. Following anaerobic fermentation (96 h, 30°C), there were no significant differences between the species in mean texture (hardness, springiness, adhesiveness, cohesiveness) and pH, and only minor differences were seen in color. However, although not consumer tested, it is argued that consumers would be able to pick a texture difference due to different fat melting point ranges, highest for sheepmeat. This work was followed by a sensory experiment to find out if characteristic sheepmeat flavors could be suppressed to appeal to unhabituated consumers. To simulate a very strongly characteristic sheepmeat, beef sausage mixtures (above) were spiked, or not, with 4-methyloctanoic, 4-methylnonanoic acid, and skatole (5.0, 0.35, and 0.08 mg kg−1, respectively). Sodium nitrite (at 0.1 g kg−1) and a garlic/rosemary flavor were variably added to create a 23 factorial design. In a randomized design, 60 consumers found that spiked sheepmeat flavors caused an overall significant decrease in mean liking on a 1–9 scale (5.83 vs. 5.35,P = 0.003), but this was completely negated by the garlic/rosemary addition (5.18 vs. 6.00,P < 0.001). Nitrite had no effect on liking (5.61 vs. 5.58,P = 0.82), although nitrite might be included in commercial examples to minimize fat oxidation and suppress growth of clostridia. Thus, sheepmeat flavors could be suppressed to appeal to unhabituated consumers. Commercial examples could thus be made for these consumers, but the mandatory use of the name “mutton” in some markets would adversely affect prospects.

Direct determination of flavor relevant and further branched-chain fatty acids from sheep subcutaneous adipose tissue by gas chromatography with mass spectrometry

4-Methyloctanoic acid, 4-ethyloctanoic acid and 4-methylnonanoic acid are key-flavor compounds of sheep and goat. Yet, the low amounts of these volatile branched-chain fatty acids (vBCFAs) in the fat of the ruminants hampered their determination on a routine basis. In this work we developed a gas chromatography/mass spectrometry selected ion monitoring (GC/MS-SIM) method for the direct determination of the vBCFAs as methyl esters, which were obtained after transesterification of subcutaneous adipose tissue of sheep. The excellent sensitivity of the GC/MS-SIM method (limit of quantification, LOQ, 3.6–4.8μg/g; limit of detection, LOD, 1.1–1.4μg/g for 4-Me-8:0, 4-Et-8:0 and 4-Me-9:0) enabled us to determine the three vBCFAs without an enrichment step. Subcutaneous adipose sheep tissue of three different breeds contained 23–88μg/g 4-methyloctanoic acid, 13–26μg/g 4-ethyloctanoic acid and ∼2.9–18μg/g 4-methylnonanoic acid. Since all fatty acids were present in the FAME fraction, the samples could be screened for further branched-chain FAMEs. After elimination of unsaturated fatty acids by hydrogenation (the presence of some unsaturated fatty acids could be verified by this measure), additional measurements in SIM and full scan modes of methyl esters and picolinyl esters enabled the determination of further 97 saturated fatty acids in the samples with eight to 20 carbons. The method is suited for routine analysis and may be useful to investigate the reasons for the abundance/absence of 4-methyloctanoic acid, 4-ethyloctanoic acid and 4-methylnonanoic acid and further branched-chain fatty acids in sheep and goat.

Effect of branched-chain fatty acids, 3-methylindole and 4-methylphenol on consumer sensory scores of grilled lamb meat

Tenderness, flavour, overall liking and odour are important components of sheepmeat eating quality. Consumer assessment of these attributes has been made for carcasses from the Information Nucleus Flock (INF) of the Cooperative Research Centre for Sheep Industry Innovation. The concentrations of three branched chain fatty acids, 4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4-methylnonanoic acids (compounds related to ‘mutton flavour’ in cooked sheepmeat) and 3-methylindole and 4-methylphenol (compounds related to ‘pastoral’ flavour) were determined for 178 fat samples taken from INF carcasses. Statistical modelling revealed that both MOA and EOA impacted on the ‘Like Smell’ consumer sensory score of the cooked meat product (P<0.05), with increasing concentration causing lower consumer acceptance of the product. None of the compounds though had an effect on the liking of flavour. Obviously, reducing the effect of MOA and EOA on the odour of grilled lamb will improve consumer acceptance of the cooked product but other factors affecting the eating quality also need to be considered.

A novel method for determination and quantification of 4-methyloctanoic and 4-methylnonanoic acids in mutton by hollow fiber supported liquid membrane extraction coupled with gas chromatography

4-methyloctanoic acid (MOA) and 4-methylnonanoic acid (MNA) are the main compounds responsible for “sweaty” odor of mutton. A novel method for their determination has been developed and validated. Hollow fiber supported liquid membrane (HF-SLM) was applied to selectively extract MOA and MNA prior to gas chromatography (GC) analysis. For HF-SLM, the donor outside the fiber was the acidified supernatant (pH 4) from aqueous mutton slurry. Liquid membrane was 5% tri-n-octylphoshphine oxide in di-n-hexyl ether and 0.3M NaOH aqueous solution filled in the lumen of the fiber was used as the acceptor. The extraction last for 4h. After acidification with HCl, the acceptor was directly analyzed by GC. Importantly, HF-SLM provided high enrichment factors for MOA (133) and MNA (116). The method developed had low detection limits of 0.0007–0.0015mg/kg, good linearity (R2>0.9956), reasonable recovery (88.54–122.13%), satisfactory intra-assay (7.83–9.73%) and inter-assay (15.68–16.14%) precision.