Arkansas - Agricultural Communication Services - University of ...

AAES Research Series 488
chloride solution followed by 10% (wt:vol) trisodium phosphate
solution (Rhone Poulenc, Cranbury, NJ)(CT) and 4) an
untreated control (C). All antimicrobial treatments were prepared
in deionized water with the exception of acetic acid,
which was commercially prepared.
For antimicrobial application, beef trimmings were
placed into a Lyco meat tumbler (Model 4Q, Lyco Inc.,
Janesville, WI) with 400 ml of the first antimicrobial treatment
(either 5% acetic acid, 200 ppm chlorine dioxide or
0.5% cetylpyridinium chloride), aerobically tumbled for 3
minutes (16 rpm), then removed from the tumbler and placed
into a clean tumbler with 400 ml of the second antimicrobial
treatment (either 0.5% cetylpyridinium chloride or 10%
trisodium phosphate), and tumbled again for another 3 minutes
(16 rpm) aerobically.
Upon completion of the antimicrobial application
phase, beef trimmings were removed from the tumbler and
ground twice using a Hobart grinder (Model 310, Hobart Inc.,
Troy, OH) with a 3.2 mm plate. The ground beef was divided
into 1 lb samples and packaged on styrofoam trays with
absorbent diapers. The trays were overwrapped with
polyvinyl chloride film with an oxygen transmission rate of
1400 cc/m 2 /24 h/1 atm (Borden Inc., Dallas, TX) and stored
under simulated retail display conditions (39.2°F; deluxe
warm white fluorescent lighting, 1630 lx, Phillips Inc.,
Somerset, NJ). Fat content was standardized to 10% and validated
using a Hobart Fat Analyzer (Model F101, Hobart Inc.
Troy, OH). Ground beef pH was determined immediately
after grinding for each treatment and was 5.72 for C, 4.71 for
AC, 5.70 for CC and 6.91 for CT. For this, 0.06 oz of ground
beef was homogenized in 18 ml of distilled water and evaluated
using an Orion Model 420A pH meter with a ROSS electrode
(Model 8165BN, Orion Research, Inc., Beverly, MA).
Instrumental color. On days 0, 1, 2, 3 and 7 of simulated
retail display, instrumental color was also measured using
a HunterLab MiniScan XE Spectrocolorimeter, Model 4500L
(Hunter Associates Laboratory Inc., Reston, WV). Samples
were read using illuminant A/10° observer and evaluated for
CIE (L*, a* and b*) color values. In addition, reflectance
measurements were taken in the visible spectrum from 580
nm to 630 nm. The reflectance ratio of 630 nm/580 nm was
calculated and used to estimate the oxymyoglobin proportion
of the myoglobin pigment (Strange et al., 1974). Prior to use,
the Spectrocolorimeter was standardized using white tile,
black tile, and working standards. Eight measurements were
taken of each sample and averaged for statistical analysis.
Statistical analysis. The experiment was replicated
three times. The randomized complete block factorial experiment
was analyzed using the GLM procedure of SAS (SAS
Inst. Inc., Cary, NC). Treatments were blocked by replicate
then analyzed for the main effects of antimicrobial treatment
combination, day of display and appropriate interactions. For
variables involved in interactions, interaction means were
generated, separated using the PDIFF option of GLM, and
plotted. Least-squares means for all other variables were generated
and separated using the PDIFF option of GLM.
Results and Discussion
Effect of antimicrobial treatment combinations on
instrumental color. The effect of multiple antimicrobial interventions
on the CIE L* and b* values of ground beef are presented
in Table 1. Ground beef from the AC and CT treatments
were (P < 0.05) darker (L*) and less (P < 0.05) yellow
(b*) in color than ground beef from the C and CC treatments.
However, ground beef from the CC treatment was (P < 0.05)
lighter (L*) in color but similar (P > 0.05) in yellowness to C.
Effect of duration of display on instrumental color. As
expected, ground beef color changed with increasing duration
of display (Table 2). Across 7 days of display, ground beef
became (P < 0.05) lighter (L*) and less (P < 0.05) yellow (b*)
in color.
Effects of antimicrobial treatment combinations and
duration of display on instrumental color characteristics.
Figure 1 illustrates the day of display by antimicrobial treatment
interaction effects on instrumental color characteristics.
Ground beef from the AC treatment was less (P < 0.05) red
(a*) in color (Fig. 1, panel A) throughout display and had less
(P < 0.05) oxymyoglobin (630 nm/580 nm; Fig. 1, panel B)
through 3 days of display compared with C. However,
ground beef from the CC treatment was less (P < 0.05) red
(a*) in color initially (day 0), but similar (P > 0.05) in redness
on days 1 through 3 of display compared to C (Fig. 2, panel
A). Likewise, CC ground beef had slightly less (P < 0.05)
oxymyoglobin (630 nm/580 nm) on days 0, 2 and 7 of display
yet was not different (P > 0.05) in oxymyoglobin content on
days 1 and 3 of display when compared to C (Fig. 2, panel B).
Results from this study partially support those of Unda et al.
(1989) and Bell et al. (1986) who found that both acetic acid
and chlorine dioxide, when used as single antimicrobial interventions,
caused negative color effects on beef tissues.
However, the impact on ground beef redness (a*) and
oxymyoglobin content (630 nm/580 nm) due to chlorine
dioxide treatment in this study was minimal.
Ground beef from the CT treatment was less (P < 0.05)
red (a*) on day 0 of display, but similar (P > 0.05) in redness
on days 1 through 3 of display compared with C (Fig. 2, panel
A). However, by day 7 of display, ground beef from the CT
treatment maintained a redder (P < 0.05) color (a*) than
ground beef from the C treatment. Consequently, ground beef
from the CT treatment was not different (P > 0.05) in
oxymyoglobin content (630 nm/580 nm; Fig. 2, panel B) until
day 7 of display, when CT maintained a higher (P < 0.05)
oxymyoglobin content than C. Therefore, in addition to
reducing E. coli, Salmonella typhimurium, coliforms and aerobic
bacteria in ground beef (Pohlman et al., 2001), CT treatment
of beef trimmings before grinding also maintained a
higher level of the oxymyoglobin pigment, which resulted in
prolonged redness of color.
Figure 2, panel C shows the day of display by antimicrobial
treatment interaction effect on the hue angle of ground
beef. Ground beef from the AC treatment maintained a larger
(P < 0.05) hue angle than C through display. Since hue angle
is a mathematical computation using CIE a* and b* values,
165