Dry-aging: Bridging the gap between art and science

By Brad Kim, Department of Animal Sciences, Purdue University, West Lafayette, IN, and Phil Bass, Department of Animal Sciences, University of Idaho, Moscow, ID

Adding value to beef has been an objective for many years. Beef can be a highly variable product resulting from the beginning genetics to how it was raised. Further, meat scientists have been able to better understand fresh beef quality and value over the years and have been able to identify practices for optimizing beef regularly. However, there has been a continued push in the culinary profession to enhance the value and palatability of beef through what might be considered old-world practices. Up until very recently, dry-aging of beef has been very much an art, yet there has been a tremendous focus as of late in the meat sciences to better understand what is happening during that process and how can value be further added via the time-honored tradition of dry-aging.

Dry-aging meat is defined as holding meat, often subprimals, at refrigerated temperatures (> 28℉ and < 40℉) without a covered packaging material for an allotted period of time to allow for evaporation of moisture and to concentrate flavors while the natural enzymes in the meat enhance tenderness¹. The result of this process is a stronger beef flavor often characterized by notes of oak, earthiness, beefy/brothy, nutty, brown-roasted and at times hints of aged cheese. These flavors can be highly sought after by high-end restaurant establishments as well as patrons of artisan butcher shops. Because of the evaporative moisture loss incurred (upwards of 13 to 19%), as well as the trimming loss involved to obtain the edible portion, the costs of production are often noticeably higher than traditional wet-aging means of aging to recover the loss and obtain some profit margin. One study reported that about a 19% mark-up would be required for dry-aging to produce similar net value and margin as wet-aging². In this regard, dry-aging is more for a high-value niche market, who may be willing to pay premium prices for the dry-aged beef. Yet, purveyors of dry-aged beef continue to see growth in the category and view the process as adding value to the meat which certain end customers seem to be willing to pay.

Conventionally, dry-aging has been performed in whole carcass hanging, although subprimal dry-aging is a more common form of aging practiced by local niche/gourmet markets and high-end restaurants. During carcass hanging in the cooler, the carcass decreases in weight by a total of 4 to 6 % from the original hot carcass weight for 14 days of aging and additional trim loss (about 7% for 21 days of aging). Furthermore, the additional costs associated with the cooler operation for maintaining the controlled environment and large size of cooler space required for the extended carcass aging periods will increase the final product cost. Given that dry-aging of the entire carcass is mostly practiced in the small local meat processors, there remains a need to re-evaluate the efficacy of carcass hanging for an extended period of time. In this regard, stepwise dry/wet-aging has been suggested as a modified dry-aging method by a research group from Purdue University, where the carcass is dry-aged first and then separated beef sub-primals are continued with wet-aging in vacuum packaging (Fig. 1)³. In the study, a consumer sensory panel found no significant differences in eating quality attributes, such as tenderness, juiciness, flavor, and overall acceptance, between dry-aged and stepwise-aged (carcass dry-aging for 10 days then further wet-aging for seven days) beef loins. They concluded that stepwise-aging could be a readily applicable processing strategy, which could increase the saleable yield of dry-aged meat and lower the energy/operating costs of the process compared to conventional carcass dry-aging without compromising any of the positive impacts of dry-aging on eating quality attributes³.

Dry-aging has been practiced for decades as a traditional butchery process, but interestingly, the optimal dry-aging regimens (such as temperature, humidity, air velocity, and aging periods) to ensure high-quality palatability attributeshave not been determined. A recent study compared various dry-aging factors and their subsequent impact on meat quality attributes of beef loins⁴, concluding that dry-aging can be further capitalized through identifying optimal dry-aging conditions to improve meat quality attributes consistently (Fig.2). Furthermore, researchers from Purdue University determined that dry-aging in a controlled condition could improve the eating quality attributes of even low marbled loins from grass-fed beef cattle⁵ as well as beef loins from cull cow carcasses⁶.

These results suggest that dry-aging could be further optimized through identifying the best dry-aging regimes to provide premium quality beef products to consumers in a consistent manner. Moreover, optimized dry-aging can also be used as a natural value-adding process to enhance the overall value of a variety of meat cuts, including some inferior and/or underutilized fresh beef.

Research is currently being conducted to better understand the players in dry-aged beef. Studies looking at the species of molds and bacteria growing on the outside of dry-aged beef, in particular, are underway to try to learn how the microbial community on the meat interacts with the overall eating experience by the end-user. Pilot study research conducted by Professor Bass at the University of Idaho has shown some notable species of microbes on dry-aged beef that have the potential to increase flavor factors as well as tenderness. The world of dry-aging is yet another great way to enjoy protein-packed, nutritious, and palatable beef.

Figure 1. Trait comparisons of dry-aging, wet-aging, and stepwise dry/wet-aging. Adapted from Kim et al. (2018).Figure 2. (A) Schematic illustration of a highly controlled (temperature, humidity, and air-flow) dry-ageing cabinet; (B) a representative photo of dry-aging of beef loins in the cabinet; (C) Dry-aged beef loins at 3 weeks; (D) Retail trimming processed by a certified butcher; (E) Dry-aged beef loin section after trimming; (F) Steak cuts from wet-aged (vacuum) and dry-aged loins. Adapted from Kim et al. (2016).

Acknowledgments

This work was supported in part by Agriculture and Food Research Initiative Grant 2017-67017-26475 from the USDA National Institute of Food and Agriculture.

References

1. Kim, Y. H. B., Ma, D., Setyabrata, D., Farouk, M. M., Lonergan, S. M., Huff-Lonergan, E., & Hunt, M. C. (2018). Understanding postmortem biochemical processes and post-harvest aging factors to develop novel smart-aging strategies. Meat Science, 144, 74-90. doi: https://doi.org/10.1016/j.meatsci.2018.04.031
2. Smith, R., Nicholson, K., Nicholson, J., Harris, K., Miller, R., Griffin, D., & Savell, J. (2008). Dry versus wet aging of beef: Retail cutting yields and consumer palatability evaluations of steaks from US Choice and US Select short loins. Meat Science, 79(4), 631-639.
3. Kim, Y. H. B., Meyers, B., Kim, H.-W., Liceaga, A. M., & Lemenager, R. P. (2017). Effects of stepwise dry/wet-aging and freezing on meat quality of beef loins. Meat Science, 123, 57-63. doi: 10.1016/j.meatsci.2016.09.002
4. Kim, Y. H. B., Kemp, R., & Samuelsson, L. M. (2016). Effects of dry-aging on meat quality attributes and metabolite profiles of beef loins. Meat Science, 111, 168-176. doi: http://dx.doi.org/10.1016/j.meatsci.2015.09.008
5. Berger, J., Kim, Y.H.B., Legako, J. F., Martini, S., Lee, J., Ebner, P.E., & Zuelly, S.M.S. (2018). Dry-aging improves meat quality attributes of grass-fed beef loins. Meat Science, 145, 285-291.
6. Setyabrata, D., Xue, S., Cramer, T., Vierck, K., Legako, J.F., Kim, Y.H.B. Impacts of various dry-aging methods on meat quality and palatability attributes of beef loins from cull cow. Meat and Muscle Biology, 3(2), 45-45.