CHARACTERIZATION OF DRY-AGED MEAT FLAVOR PRECURSORS AND LIBERATION MECHANISM THROUGH A METABOLOMICS APPROACH
Creators: name: Setyabrata, Derico
Publisher: name: Purdue University Graduate School
Year: 2021
Subjects: Food sciences not elsewhere classified
Animal production not elsewhere classified

description: Within the last decade, the popularity and interest in dry-aging have constantly increased among both consumers and producers. Dry-aging is a natural value-adding process where meat is exposed to a controlled refrigerated environment without any protective barrier during the aging process. This process leads to the development of unique flavors in the final meat product. Although the prevalence of this process is increasing, there are inconsistent reports regarding the impacts of dry-aging on meat sensory attributes, especially on the flavor aspect. Given that flavor generation is dependent on the composition and availability of flavor precursors, the presence or absence of these precursors may contribute to the inconsistency observed. Thus the main objective of the research described here was to characterize the flavor precursors in dry-aged meat and elucidate potential factors or mechanisms favoring to their production. To achieve this objective, metabolomics analysis was conducted in conjunction with various chemical analyses (free amino acids, fatty acids, sugar content and volatile analysis), microbiome profiling and meat quality analysis (tenderness, water holding capacity, color stability, oxidative stability, microbial attributes and sensory analysis) to identify the essential flavor precursors and their production process. In addition, similar analyses were conducted using multiple meat sources (grass-fed beef loins, cull cow beef loins and pork loins) aged by wet-aging (WA), conventional dry-aging (DA), dry-aging in bag (DWA) and UV-light dry-aging (UDA) to elucidate the impact of the different aging treatments on meat quality, sensory attributes and flavor precursor availability. Regardless of the meat source, the results demonstrated that dry-aging altered the meat flavor precursor compositions, primarily by increasing the presence of protein-derived precursors (e.g., free amino acids and dipeptides), especially glutamine and glutamate compounds. Additionally, nucleotide and carbohydrate-derived compounds such as adenosine and reducing sugars were greatly increased after the dry-aging process. While the fatty acid profile was minimally affected, metabolomics analysis revealed a decrease in sterol and terpenoid lipids following dry-aging, which could potentially reduce off-flavors development in the meat. Other compounds such as vitamin B and vitamin C were also detected in the dry-aged product, which potentially could contribute to the flavor development. Analysis of the liberation mechanisms demonstrated that dehydration played a role in increasing the concentration of the flavor precursors in the dry-aged product, potentially promoting greater (e.g., Maillard reaction) during cooking. Furthermore, microorganisms might be responsible for further increasing the availability of flavor precursors in dry-aged meat, especially free amino acids, along with the dehydration process. Microbiome profiling found that <i>Pseudomonas</i> spp. are the most prominent bacterial species in microbial communities found on dry-aged meat which could affect the precursor release in dry-aged meat. Metabolomics analysis also indicated increased glutathione metabolism during dry-aging, which could lead to the liberation of glutamine-related compounds. The analysis also identified other compounds such as porphyrin rings (iron-related) and shikimic acid (bacterial metabolism), providing further examples of how metabolomics can identify dry-aged flavor precursors and reveal other potential mechanisms related to flavor development mechanisms. These outcomes demonstrate that dry-aging alters meat flavor precursor composition, mainly by increasing the availability of protein-, nucleotide- and carbohydrate-derived compounds. Such results indicate that the Maillard reaction is likely be the main mechanism in flavor generation in dry-aged meat. The current results provided more insights into the dry-aging flavor development, especially highlighting important flavor precursor such as glutamate and glutamine containing products, likely to contribute to the dry-aged flavor. Future study to identify the impact of different microorganism (especially mold and yeast) on dry-aging flavor development would be of interest. Additionally, impact of different cooking process should also be studies to maximize the dry-aged flavor potential from the product.