Practical evaluation of method of porker meat classification based on criteria pH ] and R

Examinations covered 1176 porkers of Polish Landrace breed. The fresh meat quality was evaluated on the basis of several physicochemical characteristics, determined in the muscle tissue of m. longissimus dorsi, 45 min and 24 h after slaughter. Polymorphism of blood proteins Phi, Po2 and Pgd, determined by genes linked to halothane-sensitivity locus Hal, was tested electrophoreticaly. The frequency of occurence of Phi-Po2-Pgd (BSA) and Phi-Po2-Pgd (BSB) haplotypes in respective classes of porkers whose meat was classified as PSE, partly PSE, normal and DFD, confirmed that the most useful method of classification of meat in Polish Landrace breed is method based on the following limit values of pH, and R,: PSE (pH, <6.0; R,S= 1.09), partly PSE (pH, <6.0; R, < 1.09) normal (pH, 3= 6.0; R, < 1.09), DFD (pH, 3= 6.0; R, 3= 1.09). The diagnostics value of pH, and R, used for fresh meat quality evaluation was determined on the basis of coefficient of canonical correlation C R . The correctness of method of meat quality evaluation was verified on the basis of quality of ham prepared using m. semimembranosus (I group-100 pigs) and m. semimembranosus, m. quadriceps femoris, m. biceps femoris ( I I group-104 pigs). The verification of correctness of the method used confirmed that parameters pH, and R, determined in m. longissimus dorsi at 45 min post mortem allow to prognose the quality of ham conserved.


INTRODUCTION
Many methods have been presented in distinguishing meat with PSE and DFD.Despite the long-term investigation on the methods of meat classification, no criterion or criteria have been found allowing explicit and quick deter-mination of faulty meat resulting from genetic and physiological traits of an animal, related to a reaction of an organism to stressing factors.
In many countries pigs are selected on the basis of the halothane test which enables elimination of individuals with genetically conditioned defect of tissue membranes (homozygotes of Hal" allele determining susceptibility to halothane).Since, as it has been explicity found (Archibald and Imlah, 1985), meat revealing PSE and DFD is most often identified in halothane-susceptible individuals, the elimination of Hal" allele from a population is accompanied by a decrease in the frequency of occurence of faulty meat (Archibald and Imlah, 1985;Vogeli et al., 1984Vogeli et al., , 1985)).Hal" gene is linked with Phi, Po2 and Pgd genes controlling polymorphism of phosphohexose isomerase of blood erythrocytes postalbumin-2 in blood serum, 6-phosphogluconate dehydrogenase.
This study was aimed at evaluating the criteria pH, and R, used for porcine classification as well as its verification on the basis of physicochemical characteristics of fresh meat and quality of conserved ham.

MATERIAL AND METHODS
The studies were performed on the material comprising of 1176 porkers of Polish Landrace breed.The characteristics of meat quality were measured in m. longissimus dorsi at the last rib by the following methods: -pH, value was measured at 45 min and pH 24 at 24 h post mortem in muscle homogenate (10 g of muscle was homogenized with 10 ml of distilled water), -the nucleotide ratio IMP/ATP was measured according to Honikel and Fisher (1977): R, at 45 min and R 24 at 24 h after slaughter, -water-holding capacity (HWC) was determined according to Grau and Hamm (1952), -drip loss was tested by the method of Prange et al. (1977), -the colour lightness was measured at 24 h after slaughter, -activity of LDH and CPK was measured according to routine methods.The limit values of pH, and R, for differentiation between normal, PSE, partly PSE and DFD meat have been applied as follows: according to Honikel and Fischer (1977) in modification by Kocwin-Podsiadla et al. (1988).
The muscle m.semimembranosus was used for preparation ham of group I (100 pigs) and muscles, m. semimembranosus, m. biceps femoris and m. quadriceps femoris for preparation of hams of group II (104 pigs).These two groups of ham were made to check the possibility of prognosis of conserved ham quality on the basis of evaluation of m. longissimus dorsi characteristics.
The quality of ham of both groups, I and II, was evaluated on the basis of organoleptic parameters as follows: consistence, slice compactness (0-5 points) and gelatine content.The diagnostic value of pH, and R, criteria for fresh meat quality evaluation was determined on the basis of canonical correlation coefficient C R .This analysis was performed on two groups of porkers: group 1-148 pigs, and group 11-261 pigs (according to Harris, 1975;Krzysko and Ratajczyk, 1978).
Polymorphism of Phi, Po2 and Pgd blood proteins, determined by genes linked to halothane-sensitivity gene Hal", was tested according to Gahne and Juneja (1985).In each class of fresh meat, selected on the basis of the above discribed methods, the analysis of Phi-Po2-Pgd haplotypes (the appropriate system of alleles in relation to these loci) distribution was performed.
The frequency of occurence of Phi-Po2-Pgd haplotypes within meat classes was expressed as a per cent ratio.The significance of strenght association between occurence of different Phi-Po2-Pgd haplotypes and meat quality was evaluated on the basis of coefficient of linkage disequilibrum D, calculated according to Vogeli and Schworer (1982).

RESULTS AND DISCUSSION
The tested pigs were divided into four groups: normal, PSE, partly PSE and DFD, on the basis of assessment of their meat quality.1.The associacion between AFB, ASB and ASA haplotypes and meat quality has not been analysed because of their low frequency in all groups of pigs (below 5%).The relationship between each of AFA, BFA, BFB, BSA, BSB haplotypes and meat quality is shown in Table 2.A significant positive association has been observed between normal meat and haplotypes AFA and BFA (Table 2 A and B, respectively) as well as between PSE meat and both haplotypes BSA and BSB (Table 2 D and E,respectively).
A positive association between DFD meat and BSA haplotypes also proved significant (Table 2 D), but the value of k = 3.79 indicated that coefficient D = 0.0325 has not been significantly different from zero (P>0.05).Highly significant association between occurence of faulty meat (PSE and DFD) and Phi B Po2 s Pgd A (BSA) and Phi B Po2 s Pgd B (BSB) haplotypes linked to halothane gene Hal" confirmed the correctness of limit value of criteria pH, and R, used for meat quality evaluation in this study.
Earlier studies of Andresen (1987) also showed the significant association between occurence of faulty meat and both alleles Phi B and H a linked to Hal locus.Haplotypes BSA and BSB used in this study for verification of criteria pH, and R, were shown to occur with significantly higher frequency within group of halothane-sensitive pigs as compare to halothane-resistant animals (Gahne and Juneja, 1985;Nielsen et al., 1985;Kuryl et al., 1992).Canonical analysis of significance of pH,, R,, pH 24 and R 24 criteria for meat quality evaluation showed that pH, and R, were most useful as compared to both traits pH 24 and R 24 (Table 3).The comparison of complex coefficients of correlation (R c 2 ) showed that traits pH, and R, were a slightly more useful for meat quality diagnosis as compared to both criteria pH, and pH 24 (Table 4 and 5).
The verification of correctness of the used method for meat quality evaluation was also performed on the basis of quality of meat product (hams) (Table 6).Low (1.56 points) and simultaneously 2.24 fold lower value of parameters of ham quality, evaluated for product prepared using faulty muscles, as compare to quality of ham formed using normal meat (3.88 points), confirmed the correctness of criteria pH, and R,.They can be considered as criteria for porcine quality classification.The presented results (Table 6) showed that the values of pH, and R, determined in m. longissimus dor si at 45 min post mortem allow to prognose the quality of ham produced using m.semimembranosus, m. biceps femoris and m. quadriceps femoris.
Phi-Po2-Pgd haplotypes have been defined for 352 individuals -triple homozygous or heterozygous in