Background 

Beef flavor is a palatability attribute that greatly impacts the beef eating experience, and has been identified as being important to consumers. Beef flavor is perceived by the senses in response to flavor compounds which develop during the cooking process. The development of cooked beef flavor is driven by chemical reactions that occur during cooking between various precursor molecules present in raw beef. For example, compounds resulting from the Maillard reaction, which is initiated between amino acids and reducing sugars, have been shown to influence cooked beef flavor. Additional flavor contributions have been shown to be made through the degradation of nucleotides which participate in the Maillard reaction. The fat, or lipid portion of the meat product also contributes to flavor compounds formed during the cooking process. These initial reactions often result in a series of further reactions which have the opportunity to produce a variety of flavor compounds. Identification of cooked beef flavor compounds allows understanding of the role of precursor molecules and the route or routes by which they transform into cooked beef flavor compounds. Enhanced understanding of the mechanisms which directly influence desirable beef flavor is imperative in order to manage and maintain consistently flavorful beef. 

It was the objective of this study to broaden the understanding of chemical mechanisms which influence beef flavor. The generation of such data will be useful in the formation of future techniques and strategies to predict beef flavor.

Methodology 

Raw and cooked beef Strip Loin Steaks and ground Strip Loins generated from previous checkoff funded research were utilized for the determination of precursor chemical compounds which may influence beef flavor. The Strip Loin subprimals and ground beef samples were selected to represent a variety of USDA Quality Grades, aging methods, production/feeding strategies and genetic type (Table 1.) The samples selected represent many options found in the retail and foodservice sectors of the industry. The raw and cooked samples were frozen in liquid nitrogen, homogenized and stored for later evaluation of fatty acid composition, amino acid content (total and free), nucleotide composition and the presence of reducing sugars.

Fatty Acid Composition: Fatty acids from neutral and polar lipid fractions were quantified using gas chromatography with a flame ionization detector following fractionation and derivatization to fatty acid methyl esters in the presence of an internal standard (Linoelaidate).    

Amino Acid Content: (Free and Total): Free amino acids were determined by the EZfaast™ amino acid derivatization technique (Phenomenex, Torrance, CA). Total amino acids were evaluated using hydrolysates of homogenized samples using the EZfaast™ technique (Phenomenex). An internal standard (Norvaline) was added to all samples to allow for quantification.  

Nucleotide Composition: Nucleotide composition of raw and cooked samples was determined using reversed-phase high-performance liquid chromatography with an Ultraviolet detector. An internal standard (purine) and internal standards were used for identification and quantification.    

Reducing Sugar Content: Sugars were determined by silylation and GC-MS analysis.

Statistical Analysis: Comparisons of precursor compounds were made among raw (strip steaks and ground strip loins) and cooked (strip steaks and ground patties from strip loins) samples obtained from previous studies.

Findings  

The overall purpose of this project was to determine compounds present in raw and cooked beef which may be related to flavor/aroma compounds previously found to be associated with desirable beef flavor. Furthermore, the presence, absence and disappearance of these compounds in raw and cooked products will yield useful information regarding each compound’s status during the cooking process and how it relates to the formation of a palatable beef product. This project was part of a larger checkoff funded study, which was one of the first of its kind to evaluate biochemical components (precursor compounds), volatile aroma compounds and actual consumer evaluation of a targeted group of products with the overarching goal to model the pathway responsible for the development of a consistently palatable beef eating experience.  

Implications  

The precursor compound composition for each sample will be added to the existing body of information regarding samples consumed in the previous studies. The data generated in the current project, along with those previously generated, will be utilized to develop a model to predict desirable beef flavors to help deliver a positive, consistent eating experience to consumers.