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Effect of intramuscular fat on beef eating quality, flavour generation and flavour release
Meat Standards Australia (MSA) graded beef striploins (n=42) from grass-fed and grain–finished Angus and grass-fed Wagyu, covering a range of nominal marbling levels from low, medium to high, were obtained from Northwest Tasmania in December 2012. The lowest fat beef samples were the AngusGrass (5.2% low, 7.8% medium and 9.9 % high), followed by the AngusGrain (10.2% low, 13.7% medium and 14.9% high fat) and the WagyuGrass (7.8% low, 10.9 % medium and 17.5% high). The concentration of omega-3 fatty acids and conjugated linoleic acid in the intramuscular fat was higher in grass-fed beef compared to grain-fed, in agreement with the literature. Standardised 25 mm steaks were cut and frozen for later sensory evaluation and flavour analysis.
A trained panel (n=10) was used to develop an appropriate grilled beef vocabulary to measure sensory attributes across the samples. More than 30 consensus attributes were applied to assess beef odour, flavour, taste and texture attributes. Most sensory attributes were directly correlated to the level of marbling (MSA-MB) regardless of the breed or feed type. As a whole, the overall flavour intensity, beef flavour, caramel odour, grassy flavour, oily mouthcoating and sweetness positively increased with marbling. As the level of marbling decreased, acidity, astringency, hay/grainy and liver flavours became more apparent. More subtle flavour and texture differences were elucidated when breed and feed comparisons were made.
Analysis of headspace volatiles by gas chromatography-mass spectrometry indicated that the concentration of most volatile compounds increased with marbling, especially the alkylpyrazines. These compounds are strongly associated with grilled beef flavour. Further analysis of the samples showed that highly marbled beef had unique temporal (time-related) flavour release properties. Key odour-active volatiles were released more rapidly in the mouth at higher levels of marbling leading to more intensely perceived flavour. Similarly, the in-mouth rate of release of non-volatile taste compounds (free amino acids and organic acids) during eating was more rapid in higher marbled samples. Different ratios of sweet and bitter amino acids in the grilled beef corresponded to different taste properties.
Overall, beef with high marbling scores > 500 MSA-MB, or a fat content of > 7.5% fat, fed on either grass or grain have quite similar flavour properties. Only the samples with the lowest fat content (< 5%), i.e. the AngusGrass low fat, were characterised by higher acidic, metallic and lingering aftertaste attributes. Taken as a whole, the data clearly demonstrate the essential role of intramuscular fat in generating beef flavour and on controlling flavour release as well as improving texture attributes.
This page was last updated on 21/06/2017
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