Effect of preslaughter fasting on the characteristics of pig livers

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Abstract
Summary: Seventy‐seven pigs of about 60 kg liveweight were killed in two experiments, which examined the influence of food deprivation preslaughter on the chemical composition, physical characteristics and eating quality of liver. In the first experiment pigs were fasted for 0, 24 or 48 hr before slaughter. Livers from fasted animals were lighter in weight (P < 0.001) and contained proportionally slightly more water (P < 0.001), fat (P < 0.001) and protein (P < 0.001) but very much less glycogen (P < 0.001) and less lactate (P < 0.001). They had higher pH values (P < 0.001) both just after slaughter and during storage at 2°C for up to 72 hr. They were darker in colour initially (P < 0.05) and after chilling for 72 hr (P < 0.01) partly due to the higher (P < 0.05) concentrations of haem pigments. The second experiment examined how these differences influenced eating quality. It included a control group killed 2 hr after food withdrawal and groups fasted for 12, 24 and 48 hr. After frying, livers from pigs fasted longer were found to be darker in appearance (P < 0.001), less tender (P < 0.001), less juicy (P < 0.001) and, overall, less acceptable (P < 0.001). Livers from pigs fasted longer also lost less weight during cooking (P < 0.05) and were tougher (P < 0.05) based on instrumental measurements. Livers from half of the pigs in each fasting group were stored at 2°C prior to assessment of eating quality; the remaining livers were frozen at −20°C. Freezing had small deleterious effects on the texture (P < 0.01) and juiciness (P < 0.05) of livers but did not influence mean overall acceptability.