Optical and Electronic Methods of Measuring pH and Other Predictors of Meat Quality in Pork Carcasses

Abstract

An optical method was developed for measuring the pH of pork. Small (.5 g) meat samples were compressed against Nitrazine (phenaphthazine) paper. The optical absorbance of Nitrazine paper measured at 600 nm with fiber optics was correlated with meat pH measured with a glass pH electrode (r=.89, P<.005). Fiber optics were also used to examine postmortem changes in the absorbance of semimembranosus muscles in intact sides of pork. On each carcass, the apparatus was kept at a constant location and measurements were made continuously with a microcomputer. At about 50 min postmortem, the absorbance at 700 nm was higher than at 24 h (.57 ± .07 vs .44 ± .09, P<.005). In some (8/15) carcasses, a transient increase in absorbance was superimposed on this decline. The peak value was 104.6 ± 5.9% of the absorbance at 50 min and it occurred at 180 ± 103 min postmortem. The electrical capacitance of the semimembranosus declined (P<.01) postmortem from 5.27 ± 1.01 nF at about 50 min to 3.70 ± .51 nF at 24 h. Longitudinal correlations of absorbance at 700 nm with capacitance were extremely irregular and ranged from .84 to -.79. The sporadic occurrence of transient postmortem increases in optical absorbance may complicate attempts to predict the ultimate paleness of pork from opto-electronic measurements made on hot carcasses. Copyright © 1985. American Society of Animal Science. Copyright 1985 by American Society of Animal Science.