"This study demonstrates that the novel vacuum-packaging bag can increase yields and decrease yeast counts, and could provide business management efficiencies without affecting the quality of dry-aged beef," the researchers stated in a report. "Given consumers' preference for this uniquely flavored product and its greater value per pound, it is clear why many top-end processors practice dry aging. For those who wish to dry age beef, our research suggests that the novel method of dry aging increases the economic feasibility."
The study was produced by researchers at the Kansas State University. The researchers compared the traditional dry-aging method for beef with a novel technique of dry aging in a highly moisture-permeable vacuum bag.
Paired beef strip loins were cut into four sections and were dry aged unpackaged or packaged in the novel bag for 14 or 21 days.
"Cooking loss, tenderness, juiciness, and all flavor attributes were similar for the aging methods," the researchers stated. "Beef dry aged in the bag had less weight loss during aging, less trim loss after 21 days, and lower yeast counts after either aging time, compared with beef dry aged unpackaged."
The method of dry aging beef in a vacuum bag can also increase yields, decrease microbial contamination, and provide processors greater flexibility of facility use, all of which would positively impact processors' profits, the researchers found.
Currently processors use either of two basic methods to age beef.. Beef meant for retail and most food service outlets are aged in highly moisture-impermeable, vacuum-package bags, a process known as wet aging.
A unique, highend segment of the industry still ages unpackaged cuts in coolers tightly controlled for temperature, humidity, airflow and air quality. The process is termed dry aging, and creates a highly prized product with superior aged flavor that is sold at a premium, compared with wet-aged beef.
Dry-aged beef experiences considerable surface drying and discoloration during the process. These areas must be trimmed before steak cutting and cooking. As a consequence, the yields associated with dry aging are lower than wet aging, resulting in an economic loss to the processor.
Consumers have been found to have a definite preference for dry-aged beef, and willingly pay for the perceived improvement in quality and eating experience, the researchers stated.
The researchers used technology that allowed for the development of vacuum-package bags that allow the efficient transfer of water vapor from the cut surface of meat, thus making it feasible to dry-age beef in a vacuum package.
"The aging format has the potential to decrease surface desiccation and crusting, and permit dry aging of cuts in multi-use coolers, rather than having coolers dedicated solely to dry aging," the researchers stated.
Six pairs of certified Angus Beef strip loins were obtained two days after death. Each pair of loins was divided into four total sections, and one of four treatments was assigned to each section within a loin pair.
They were subjected to traditional dry aging or dry aging for 14 or 21 days in an experimental bag with a high water-vapor transmission rate of 8000 grams of water ever 24 hours at 100°F, with 50 per cent relative humidity.
Loins were aged unpackaged on racks as in the traditional method or vacuum packaged in a bag in a 37ºF cooler with 87 per cent relative humidity.
Total aerobic bacteria, lactic acid bacteria, and yeast counts were determined before and after aging. Loin sections were weighed before and after aging and after trimming aged meat.
Loin sections were then cut into one-inch-thick steaks for sensory analysis and cooking-loss measurement. Six panelists rated steaks cooked to a medium degree of doneness for eight sensory attributes on a 15-point scale.
"Traditional and in-the-bag dry aging yielded similar results for tenderness, juiciness, and other measured flavor attributes," the researchers found. "All samples were of acceptable tenderness, juiciness, and flavor."
The aging method also significantly impacted loin section yield. After 14 days of aging, weight and trim losses were similar between loins aged traditionally and in the bag. However after 21 days traditionally aged loins had greater weight loss and trim loss.
Further, dry aging for 21 days in the bag did not increase trim loss, compared with dry aging 14 days, but traditional dry aging did lead to greater trim loss at 21 days than at 14 days. Cooking loss was similar among treatments.
"Overall, dry aging for 21 days in the bag will increase yields, decreasing the primary cost associated with dry aging," they concluded.
Dry aging in the bag decreased yeast counts after both aging periods. Counts of lactic acid bacteria decreased from 14 to 21 days of aging, possibly due to surface desiccation that occurred during aging, which reduced the amount of available water for microbial growth, they stated.
No differences existed among treatments for total plate counts. The dry aging technique using novel vacuum packaging was found to effectively decrease potential yeast load and be similar to traditional dry aging for total plate counts and lactic acid bacteria.