Background

In addition to juiciness and tenderness, flavor is a key component of overall palatability and consumer acceptability in regard to overall liking and purchasing decisions. When tenderness is held constant, flavor becomes the most important factor for consumers when making meat purchasing decisions. Numerous research studies have previously been conducted on a variety of cuts and muscles within the beef carcass, quality grades, production systems, etc. However, there is still an abundant amount of knowledge in regard to the overall chemistry involved in the development of beef flavor via the Maillard reaction that remains unknown. Lipid breakdown products and water-soluble compounds (free sugars, amino acids, peptides, etc.) are the main contributors to the overall development of meat flavor. These compounds, which are present in the raw product, contribute to the overall development of beef flavor via chemical reactions, which occur during the cooking process. The initial steps of the Maillard reaction involve reactions between amino acids and reducing sugars. Furthermore, thermal application presented during the cooking process leads to a series of reactions involving amino acids, reducing sugars, phospholipids and triglycerides. Through the continued identification and quantification of these compounds in both raw and cooked beef, with varying levels of marbling, cooking methods and degrees of doneness, researchers can begin building upon the current knowledge of overall beef flavor acceptability.  

Consumers have continued to express the importance of beef flavor during consumption and buying habits. Understanding the mechanisms influencing and driving beef flavor is important in applying current beef flavor knowledge in providing consistent flavorful beef. Correlating this database of precursor compound knowledge with consumer insight into overall acceptability of various cuts of beef, cooking methods and marbling levels was the main objective of this study. This information will also be compiled with current beef flavor knowledge in order to develop innovative technologies for providing consistent flavorful beef. 

Methodology 

A variety of raw and cooked beef cuts including Bottom Round Roasts, Tenderloins and Top Sirloin Butt Steaks generated from previous research were utilized for determination of precursor compounds known to influence the acceptability of beef flavor. These cuts represented a variety of USDA Quality Grades, cooking methods and cooking temperature end-points. Samples of varying USDA Quality Grades, muscles, wet-aging periods and flavor enhancement strategies were also utilized for proximate composition, precursor compound research and sensory evaluation. All raw and cooked samples were frozen in liquid nitrogen, homogenized and stored for later evaluation of various precursor compounds and proximate composition.  

Consumer Sensory Evaluation: 108 consumers rated six samples varying in quality grade, muscle and wet-aging periods. Samples were rated for liking of flavor and overall liking on a 100-mm continuous line scale, as well as rated for their acceptability (yes or no) for these specific traits. In addition, consumers also ranked the quality of each sample as unsatisfactory, good everyday quality, better than everyday quality or premium quality.  

Proximate Composition: Evaluation of moisture, ash and protein content as components of the proximate composition of raw and cooked samples varying in quality grade, muscles, wet-aging periods and addition of flavor enhancers was performed. A modified chloroform-methanol procedure was utilized to determine total fat content in each sample.  

Lipid oxidation by-products: Thiobarbituric acid reactive substances analysis was employed. Sample absorbance was read in duplicate and each raw and cooked sample were analyzed in duplicate.  

Volatile Compound Analysis: Volatile compounds were collected from the headspace of cooked ground beef patties using a carboxen polydimethylsiloxane solid phase microextraction (SPME) fiber. The SPME fiber was then injected onto the gas chromatography-mass spectrometry (GC-MS) for separation and detection of these volatile compounds. Compounds were identified and quantified using an internal standard (1,2-dichlorobenzene) and authentic standards. 

Fatty Acid Composition: Lipid was extracted and fatty acids were separated into neutral and polar lipid fractions to be derivatizatized to fatty acid methyl esters for quantification using gas chromatography with a flame ionization detector. A mix of fatty acid methyl esters was used to identify fatty acids, while linoeliadate acid methyl ester served as the internal standard for quantification.   

Amino Acid Content (Free and Total): Free amino acid and hydrolysates of homogenized samples for total amino acid evaluation were generated, separated and identified using the EZ-Faast amin acid derivatiziation technique. Quantification of free and total amino acids was conducted via the addition of an authentic internal standard (Norvaline).  

Reducing Sugar Content: Reducing sugars were silyated for analysis on the GC-MS. Samples were identified and quantified using authentic standards as well as an internal standard (Rhamnose).  

Statistical Analysis: Comparisons of proximate composition, precursor compounds, lipid oxidation by-products and sensory evaluation were conducted among raw and cooked samples obtained from previous beef flavor research studies as well as from procurement at commercial processing facilities (ground muscle and flavor enhancement studies). 

Findings 

The measurement of beef flavor precursors in samples obtained from collaborating universities will provide invaluable insight into consumer preferences for a variety of beef cuts prepared using multiple cooking endpoints and degrees of doneness. These data indicate extended wet aging of certain beef cuts can promote oxidation and decrease consumer acceptability. Moreover, sugar esters can be incorporated into to meat models to further understand the drivers of beef flavor and potentially improve beef flavor. 

Implications 

The precursor compound composition of samples from previous work will add to consumer panel insights into overall acceptability of beef flavor in regard to cooking methods, degree of doneness and varying marbling scores. Other data generated from the current study will add to the current database of beef flavor data and assist in further development of a prediction model for pleasing beef flavor.