Background

The use of metabolomics is a relatively new technology that can be applied to beef sensory and especially to the complexity of flavor. The term metabolomics is simply defined as ‘the study of as many small metabolites as possible’. More specifically, metabolites are indicators of meat and muscle metabolism and can be used to describe the general condition of tissue. Many of these metabolites serve as precursors to flavor and aroma compounds that make up the taste of beef. It is hypothesized that this technology can be used to predict and describe beef flavor. Metabolites have already proven their worth in cholesterol and glucose as canaries for heart disease and diabetes, respectively. Metabolites are effectively the end of very complex interactions occurring inside the cell (in the genome) and those occurring outside the cell or organism (in the environment). In other words, metabolomics allows researchers to obtain a highly sensitive and more complete description of the phenotype. Recent advances in analytical chemistry and metabolite data analysis techniques are making metabolomics much more common in mainstream research.

The objectives of this study were to 1) predict flavor potential using metabolomics, with a novel HPLC‐QTOF technology, in raw and cooked meat differing in quality grade, aging, and degree‐of‐doneness; and 2) determine metabolomic predictors, namely sugars and amino acids, for Maillard reaction development potential of positive beef flavor.

Methodology

Loin muscles were removed from 18 USDA Select and 18 USDA Upper 2/3 Choice, cut in half, and each loin half was assigned to either a 10‐d or 20‐d aging time. After aging, the steaks were cooked on a 400°F flat‐top grill to an internal temperature of either 145°F (medium rare), 160°F (medium), or 176°F (medium well) and served to either a trained descriptive sensory panel or to one of 93 consumers. After cooking and serving, the remaining meat was powdered and analyzed for volatile aroma compounds using a gas chromatograph/mass spectrometry and metabolites using high‐ performance liquid chromatography/mass spectrometry.

Findings

The condition of beef top loin steaks, including postmortem aging time, USDA quality grade, and degree of doneness have a significant impact on trained sensory and consumer acceptance scores. It appears that all three of these criteria are important for the proper development of beefy flavor. USDA Choice steaks have a more intense beef flavor identity, brown, roasted, fat‐like, salty, sweet, sour, umami, buttery, and overall sweet flavors and were juicier and more tender compared to USDA Select steaks. Steaks cooked to 176°F had more intense beef identity, brown, roasted, and umami flavors than steaks cooked to a lower degree of doneness. Steaks cooked to either 145°F or 160°F had more intense bloody, metallic, and sour flavors and are juicier, more tender, and had less connective tissue than steaks cooked to a higher degree of doneness. Both metabolites and volatile aroma compounds show strong relationships to sensory and successfully cluster with aging, quality grade and degree of doneness indicating their usefulness in describing flavor attributes. The HPLC analysis of raw strip loins indicated that 14 compounds were identified that were shared across all four QG x aging combinations. This included 11 protein fragments, 2 fats, and 1 complex. Additionally, there were 2 protein fragments and 1 sugar that were significantly (P < 0.05) upregulated in the Choice, 20‐d‐aged strip loins. Metabolites in raw meat are significantly affected by USDA Quality Grade, aging time, and degree of doneness. Metabolomics can be used to predict and describe beef top loin sensory traits and is one more step in our understanding of the very complex characteristic of beef flavor.

Implications

Beef flavor is an extraordinarily complex sense that the human body has to interpret using not only the tongue but also the nose. Proper selection of criteria to predict beef flavor is important to ensure consumer acceptability. Upper 2/3 Choice steaks aged 20 days can be cooked to any degree of doneness and have similar consumer acceptance, indicating that there is an extra level of ‘insurance’ that the steak will eat well under those conditions regardless of how the steak is cooked. Additionally, if Select steaks are aged 20 days and cooked to 145°F, they will have similar consumer acceptance to Upper 2/3 Choice. Measurement of volatile aroma compounds and metabolomic technology can be applied to increase understanding of the complexity of flavor and determine a future roadmap to ensure that beef maintains its place as center of the plate when flavor is the most important criteria.