Electrical impedance correlations to pork quality

Abstract Text:

The objective of this study was to identify the relationships between electrical impedance values and pork quality characteristics of boneless loin chops. Sections of boneless loins were collected weekly from 2 separate pork processing plants (20 samples from plant A and 10 samples from plant B over 6 weeks), vacuum packaged, and sent to North Dakota State University for analysis. Samples were cut into 2.54-cm slices and allowed to bloom for 10 min before subjective color and marbling (NPB, 2010) were evaluated. Instrumental color was evaluated using a Minolta Colorimeter (CR-410, 50 mm diameter orifice, 2° observer; Minolta Company, Ramsey, NJ) using both C and D₆₅ illuminants. The pH was recorded using a Hach H160 meter (Loveland, CO). Electrical impedance measurements were taken using an EFRESH Analyzer (CellMet Rx Corporation, Harrisville, MI) that sent a sinusoidal wave form of 425µA ± 25µA at 50kHz through probes into the sample. Drip loss and cook loss characteristics were also measured by weighing the samples before and after being stored at 4°C for 24 h or being cooked to 65°C respectively.  After being cooked, samples were evaluated for Warner-Bratzler Shear Force (WBSF; G-R Manufacturing, Manhattan, KS). Residual correlations were estimated using PROC CORR in SAS (SAS Institute, Inc., Cary, NC). Resistance was significantly correlated (P<0.05) with C illuminant L* (r=-0.19) and a* (r=0.18) and D₆₅ illuminant L* (r=-0.19) and a* (r=0.15). Reactance was significantly correlated (P<0.05) with subjective color score (r=0.23), C illuminant L* (r=-0.29) and b* (r=-0.28), D₆₅ illuminant L* (r=-0.29) and b* (r=-0.30), and WBSF (r=0.23). Impedance was significantly correlated (P<0.05) with C illuminant L* (r=-0.20) and a* (r=0.15) and D₆₅ illuminant L*(r=-0.20). Impedance also tended to be correlated (0.05<P<0.10) with subjective marbling score (r=0.14) and D₆₅ illuminant a* (r=0.13) and b* (r=-0.13). Phase angle was significantly correlated (P<0.05) with pH (r=0.25), C illuminant L* (r=-0.36) and b* (r=-0.35), subjective color score (r=0.25), WBSF (r=0.28), and D₆₅ illuminant L* (r=-0.35) and b* (r=-0.37). In summary, electrical impedance measurements on individual pork loin chops are a poor indicator of pork quality because they are weakly correlated with pork quality measurements.

Keywords: electrical impedance, pork quality, pork