Developing premium Irish beef through dry aging and novel processing technologies

Mary Ann Kent

Irish beef is well-known around the world and is synonymous with being high quality, flavoursome and nutritious, thanks to our pasture-based farming systems. Considering this high-value raw material, industry is increasingly seeking opportunities to further enhance the eating quality and consumer acceptance of Irish beef. Extensive research has been carried out on this area at the Teagasc Food Research Centre in Ashtown, Dublin, where a particular area of interest in recent years has been on dry aging. In this regard, Teagasc led an international joint effort (INIA-Uruguay, IRTA-Spain, AgResearch-New Zealand and Teagasc-Ireland) to develop smart dry-aging processes focused on pasture-based production systems. This recently completed project brought together international expertise in animal production, customisation of dry-aging process, advanced -omics approaches and application of innovating processing technologies. This project demonstrated that, i) -omics tools, such as proteomics and metabolomics, are essential to understand the biochemical changes taking place during aging and its impact on aroma and flavour precursors, ii) showed how grass-fed beef is an excellent raw material for high-quality dry aged meat and iii) established the basis of future research on advanced processing technologies aiming to make this process more sustainable and economically feasible.

What is dry aging?

Dry aging involves storing beef (carcasses, primal or subprimal cuts) without packaging (or using water permeable packaging materials) under controlled conditions (typically 0 – 4 °C and 75 – 85% relative humidity) for between 14 to 35 days. This is opposed to the conventional method of aging (i.e. wet aging), whereby primals are vacuum packed prior to maturation. Dry aged beef is sold at a premium price as it produces a first-class flavoured product; however, dry aging reduces saleable yield (compared to wet aging) and promotes crust formation, which needs to be trimmed prior to sale. The time required for dry aging and related reduction in yield makes dry aged beef a more expensive product when compared to wet aged beef.

What happens in the meat throughout dry aging?

1. Water migration and evaporation

Water loss is the key macroscopic event that occurs during dry aging, due to water migration from the core to the surface, and subsequent loss from the surface of the muscle via evaporation. This water loss favours the concentration of flavour and aroma related molecules, developed during the maturation process. Research carried out at Ashtown has found that the rate of moisture loss is influenced by the shape and size of muscle (geometry) being aged. It was found that thinner cuts, such as slices (0.5 cm thick) and steaks (2.54 cm thick) lost moisture faster than sections (24 cm thick). In all cases, moisture content decreased exponentially over time until an equilibrium was reached (final weight). The final weight loss at equilibrium for each muscle geometry studied, differed. For example, slices were ~68% of initial weight after 22 days, steaks were ~58% of initial weight after 48 days, and sections were ~33% of initial weight after 48 days of dry aging. Prediction models developed based on this work, means that processors can now better estimate how long it will take to reach a target moisture content and thus control the dry aging process, helping to balance meat quality and yield reductions.

Subsequent research at Teagasc explored water loss at a deeper level by examining the moisture content and water activity of internal and external locations within section of muscle before and after dry aging. To establish a baseline prior to dry aging, a 5 cm thick section was examined across internal and external locations. Water activity across the section was uniform, and moisture content varied minimally within the section (<2%; ~ 72-74%) indicating no strong internal gradients were present. However, following 48 days of dry aging, a pronounced gradient had developed across the diameter of the dry-aged piece.  Internal regions retained high moisture (~69%), in-between regions contained ~59%, whereas external regions were much drier (~36%), confirming that water had migrated outward. This migration, however, was limited by matrix properties and the formation of crust on the surface, restricting the evaporation rate. Water populations (i.e. how the water molecules interact with the meat matrix: free water, trapped water or bond water) were also investigated. The most mobile fractions—free and entrapped water—decreased significantly in the internal regions of the meat over time, while the proportion of more tightly bound water increased. This indicates that the more mobile water moved outward first and was removed during evaporation at the surface, leaving behind water that is more strongly associated with muscle structures. This phenomenon was more evident in thinner geometries, such as slices and steaks.

2. Proteolysis and oxidation

Lipid and protein oxidation are the key biochemical drivers for the development of the characteristic flavour of dry aged beef. During dry aging, proteolysis also occurs as enzymes such as calpains and cathepsins break down muscle proteins over time, contributing to the tenderisation of beef, while also releasing free amino acids and peptides that act as flavour and aroma precursors. The combination of these two processes produces a premium, tender beef product with enhanced flavour and aroma. Studies carried out in Teagasc, Ashtown have also shown that at a molecular level (using a proteomics approach), the inner and outer regions of dry aged meat evolve differently over time due to differences in oxygen exposure, microbial activity and dehydration. The outer surface showed greater antibacterial activity, protein folding and metabolic pathways associated with dehydration and oxygen exposure, while the inner region had more abundant proteins linked to muscle structure and tissue organisation. Proteomic analysis also showed that beef aged using dry- or wet-aging, and animals finished on either grass-based or concentrates-based diets had differential proteomics profiles (Figure 1), and thus, potential differences in organoleptic features.