Effects of fasting prior to slaughter on technological and sensory properties of the loin muscle (M. longissimus dorsi) of pigs

The aim of this study was to investigate the effect of pre-slaughter fasting time, sex and feeding regime on water-holding capacity (WHC), colour and sensory properties and their relationship with pH in M. longissimusdorsi (LD) in pigs. 270 pigs of the commercial Norwegian crossbreed Noroc (Norwegian Landrace × Yorkshire sow and Norwegian Landrace × Duroc boar) were used involving two sexes (gilts and castrates), two feeding regimes (restricted and ad libitum) and four fasting treatments: (F4) 4 h fasting (control), (F175) 17.5 h fasting on the farm, (FO175) 17.5 h fasting overnight at the abattoir, and (FO265) 26.5 h fasting overnight at the abattoir. Additionally, the pigs experienced two abattoir lairage times as fasting treatments F4 and F175 had a lairage time of 1.5 h, while fasting treatments FO175 and FO265 had a lairage time of 23.0 h. A short fasting time of 4 h led to a delayed decline in pH post-mortem and a lower ultimate pH (pHu) in the LD compared with a fasting time of 26.5 h which resulted in a rapid pH decline early post-mortem and a high pHu. Prolonged fasting reduced drip loss, resulted in a darker colour and tended to improve tenderness of the LD. Castrates showed lower drip loss, higher lightness and improved tenderness and juiciness compared with gilts, while ad libitum feeding improved tenderness compared to restricted feeding. There are obvious negative relationships between pHu and drip loss, lightness and tenderness of LD.