Factors affecting flavor of dry-aged beef and mechanism for the flavor development

Abstract

Aging improves tenderness, flavor, and juiciness of meat, especially beef. There are two commercial types of aging, dry and wet (vacuum). In recent years, dry-aged beef has obtained consumers interest from market due to its intense beefy/roasted flavor when compared to wet-aged one. However, the origin for the specific flavor of dry-aged beef and factors affecting its flavor are still unknown. Therefore, the objectives of this study were i) to investigate the factors affecting flavor of dry-aged beef, ii) to elucidate the mechanism for flavor development of dry-aged beef, and iii) to suggest optimal conditions for the application of dry aging process. The experiments were consisted of three different sections as follows:<br/> <br/> Experiment I.<br/> Role of moisture evaporation in the taste attributes of dry- and wet-aged beef determined by chemical and electronic tongue analyses<br/> The role of moisture evaporation in the taste attributes of dry- and wet-aged beef was determined. A total of 30 sirloins (longissimus lumborum) were dry or wet aged for 28 days and analyzed for taste-active compounds (FAAs, IMP, and RS), moisture content, pH, and trimethylamine content, and an electronic tongue. The higher FAAs and RS and lower IMP contents were found in dry-aged beef, while a relatively higher taste of saltiness, sourness, and umami was detected than those in wet-aged one. Although moisture content was highly correlated with FAAs and RS in dry-aged beef (r2=-0.9 and -0.9, respectively), its amount was not proportionally decreased with the change in taste compounds. Meanwhile, dry-aged beef had approximately 2-3 folds higher trimethylamine content at day 28 (P<0.05), when compared to that in wet-aged one. Considering both moisture and trimethylamine contents in this study, the taste of dry-aged beef was mainly generated by the further proteolysis and IMP degradation with the growth of microorganisms on the crust and partially by the concentration effect on taste-active compounds from moisture evaporation.<br/> <br/> Experiment II.<br/> Effect of air flow velocity on microbial composition and sensory property in dry-aged beef<br/> Twenty one beef rumps (middle gluteal) were dry aged for 28 days with different air flow velocities of 0, 2.5, and 5 m/s (Dry 0, Dry 2.5 and Dry 5, respectively) and the analyses of microbial composition, moisture content, pH, shear force, and flavor compounds (IMP, RS, FAAs, and FFAs) were conducted. The mold and yeast were not detected until day 14. However, the mold, Pilaira anomala, was dominated in Dry 0 at day 28, whereas Dry 2.5 and Dry 5 had the higher compositions of Debaryomyces hansenii when compared to that of Dry 0. The more Pseudomonas and Enterobacterium were found in Dry 0, while those in Dry 2.5 and Dry 5 had the higher compositions of Lactobacillus and Flavobacterium. The different compositions of P. anomala and D. hansenii may affect sensory property of dry-aged beef as most of the significant changes in physicochemical traits and flavor compounds were occurred between days 14 and 28, after the mold/yeast were observed on the crust.<br/> <br/> Experiment III. <br/> Role of P. anomala and D. hansenii in sensory property of dry-aged beef and their application for dry aging process<br/> Two different experiments were designed in this study i) to determine the role of P. anomala and D. hansenii in sensory property of dry-aged beef and ii) to suggest their optimal conditions for the application of dry aging process. In the experiment i, a total of 24 beef sirloins (longissimus lumborum) were obtained and P. anomala or D. hansenii was inoculated onto each 12 sirloins. Then, all samples were dry aged for 28 days and analyzed for microbial growth, pH, shear force, ultrastructure, and flavor compounds (IMP, RS, FAAs, and FFAs). The inoculation of P. anomala and D. hansenii could influence sensory property of dry-aged beef as P. anomala had more impact on tenderness and lipolysis by its high proteolytic and lipolytic activity, whereas D. hansenii resulted in the higher amount of FAAs at day 28 (P<0.05). Also, both P. anomala and D. hansenii could be grown on the crust of dry-aged beef with a reliable numbers (6-8 log CFU/g), suggesting that their possible application for dry-aged beef. In the experiment ii, a total of 36 beef sirloins (longissimus lumborum) were obtained and each 12 sirloins inoculated with the combination of P. anomala and D. hansenii at the ratio of 1:1 or 4:1 (P1D1 or P4D1, respectively) and dry aged for 21 days. The analyses of shear force umami intensity, FAAs, and FFAs were conducted to select the test samples from each treatment, which had the best sensory property. The test samples were obtained from 15, 15, and 10 days for none-inoculated, P1D1, and P4D1 groups, respectively, for the preference and descriptive sensory analyses. As a result, there was no significant difference found in all sensory parameters tested (dry-aged aroma, flavor, tenderness, and overall acceptability). Therefore, it can be suggested that the combination of P. anomala and D. hansenii at the ratio of 4:1 can accelerate dry aging process at least 5 days without adverse effect on its sensory property.<br/> <br/> Keyword: Dry-aged beef, Flavor, Moisture evaporation, Pilaira anomala, Debaryomyces hansenii<br/>