Electrical stimulation and ageing of carcasses from red, fallow and New Zealand wapiti‐type male deer

Abstract

Abstract Farmed male red deer (15 and 26 months), fallow deer (16 months) and New Zealand wapiti‐type deer (26 months) slaughtered in an experimental abattoir were used to determine the influence of processing practices on tenderness and pH. Carcasses were electrically stimulated (low voltage) through the leg or anus immediately after bleeding and compared with non‐stimulated carcasses. Portions of loin and leg from all carcasses were subjected to a range of conditioning and ageing treatments before tenderness assessment was done with a Warner‐Bratzler shear press. Tenderness was measured in some samples after a freeze and slow thaw cycle. Electrical stimulation in all deer types had a highly significant effect in improving tenderness and the effects were most dramatic when carcasses were placed in a chiller 2 h after slaughter. Conditioning and ageing regimes (maximum 96 h post‐slaughter) further improved tenderness, particularly in non‐stimulated carcasses. Processing effects were more marked in loin pieces; these cooled more rapidly than leg. The process of freezing and slow thawing (20 h at 4°C in loins and 24–96 h at 0°C for legs) improved tenderness by 10–40% when compared with unfrozen pieces. There were highly significant reductions in the pH values of legs due to stimulation as measured during the early stages after slaughter. A decline in pH with time post‐slaughter was also evident. The results were consistent with the post‐slaughter pH profile of loins. Electrical stimulation, via either the leg or the anus, gave similar results. An exception was the loin pH measurement from anally stimulated wapiti stags which appeared higher than their leg‐stimulated counterparts. Where data were collected from both sides of leg‐stimulated carcasses, pH values were around 0.13 units lower for the stimulated shackled leg than for the free leg. Leg temperatures rose to over 40°C at 0.5 h post‐slaughter in all deer. Temperatures were generally similar between stimulated and non‐stimulated carcasses for both loin and leg data.