Yuching Chiang and Tom Ringkob
School of Veterinary Medicine
University of Nevada, Reno

Introduction

Two problems cited by supermarket meat managers, which cause beef retail meat packages to be discounted or discarded, are poor workmanship and discoloration. Poor workmanship which displays too much fat or bone and therefore lowers the perceived value of the retail beef cut can be remedied through better procurement specifications, management and training. However, discoloration of fresh beef can be a much more complex problem also leading to lower sales and therefore negatively affects profitability. Any improvement in sanitation and temperature control usually lowers bacterial count and lengthens retail shelf life. If the retail packaged beef maintains a desirable bright red color for a longer period, more inventory can be displayed which leads to increased sales. The objective of this study was to compare the impact of 2 retail display temperatures and 3 processing procedures on discoloration and shelf life of retail beefsteaks.

Sampling

Vacuum packed (boxed) loin strips were purchased at Scolari’s Food and Drug of Sparks, Nevada which included 12 Packer A Choice, 12 Packer A Select, and 12 Packer B strips. One thick (5 cm) knife cut, four regular (2.5 cm) knife cut, and four regular (2.5 cm) saw cut steaks were cut from each vacuum packaged loin strip at one of 11 Scolari’s supermarkets, on a random basis, in Reno and Sparks, Nevada. Steaks were at the anterior end of the loin (13^th rib section). Degrees of marbling ranged from slight to moderate when compared to USDA color marbling standards.

Each thick (5 cm) loin steak was bisected into 2 thinner steaks using a sterilized butcher knife at the University Meat Lab. The bacterial samples were taken from the "store" bottom and the "fresh" cut (sterilized knife) surfaces by sponging for total plate count. The resulting steaks were repackaged supermarket style in Styrofoam trays with oxygen permeable film overwrap. The two steaks were packaged such that the original displayed "store" surface was visible in one steak and the "fresh" cut surface in the second steak. The 4 store-knife-cut and 4 saw-cut loin steaks were displayed in the original supermarket trays.

From each loin strip, one fresh-cut, one store-face, two store-knife-cut, and two saw-cut steaks were displayed under 33.9 ± 0.5° F and two store-knife cut and two saw-cut steaks were displayed under 40.6 ± 0.5° F. The bacterial samples were taken from the fresh-cut, store-face, and one of store-knife-cut and saw-cut steaks on the "pull" day. For the other store-knife-cut and saw-cut, the bacterial samples were taken on the "discard" day. Steaks were pulled when meat department personnel would notice any discoloration or darkening. Steaks were discarded when meat department personnel would consider the steak no longer salable due to discoloration.

Bacteria Count

The sponge bags, 25ml of sterile Butterfield’s Phosphate Buffer (BP), gloves, and templates were purchased from Biotech Co. for sampling. The sponges were hydrated by adding 25ml of BP buffer and well massaged. The bacterial samples were taken by sponging the steak surfaces followed by bumping each sponge in the sample bag at 8 bumps per second by using the stomacher. The sample was diluted to the necessary rates.

The total aerobic petrifilm plates were purchased from 3M for microbial growth. 1ml of the diluted sample was inoculated to the petrifilm plate and incubated at 35 ± 1° C for 48 ± 3 hours. The numbers of bacteria were calculated as cells per square of steak surface (cells/cm²).

Statistical Analyses

Fig. 5-There was a significant difference in the bacteria count between fresh cut and packer cut (p<0.05) on Day 0 steaks.

Lower temperature helped steaks staying longer as well (p<0.05, Fig. 2). Obviously, lower temperature decreased bacteria growth but the difference was not significant (p>0.05, Fig. 9).