The aim of this study was to evaluate meat quality of first-farrowing sows differing in regard to the rate of post-mortem glycolytic and protein changes. Normal quality meat (RFN) (n=48) was compared with meat characterised by slower glycolytic changes (RFN-s) (n=9). The evaluation of meat quality comprised measurements of the pH value, IMP/ATP ratio, electrical conductivity, proximate composition of meat, its selected physico-chemical properties and changes of proteins in centrifugal drip (2-DE and in association with Western-blotting and MALDI-TOF MS). The results showed that different acidification rate of meat modified its physico-chemical properties. The tenderness of RFN-s meat was lower than the RFN one. Mass spectrometry measurements indicate a possible association of creatine kinase with slower pH decline. Lower acidification led to a smaller thermal drip but deteriorated tenderness of meat from heavy pigs.