Abstract:
Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 RELATIONSHIP BETWEEN COLOUR AND pH IN LAMB LOINS D. J. MENZIES and D.L. HOPKINS NSW Agriculture, PO Box 242, Cowra, N.S.W. 2794 An association between meat colour and pH has been documented for beef (MacDougall et al. 1972) but little information is available for lamb. MacDougall et al. (1972) demonstrated a relationship between both subjective and objective measurements of colour and the pH of bull beef. The present study details the relationship between the pH of lamb loins and an objective measure of their meat colour. Eighty-seven cryptorchid lambs from a range of genotypes (Texel x Merino, Texel x Border Leicester x Merino, Poll Dorset x Merino, Poll Dorset x Border Leicester x Merino, Border Leicester x Merino, Merino x Merino) were utilised for this study. The lambs had a fasted liveweight greater than 44 kg and were trucked to a local abattoir and slaughtered under commercial conditions. After slaughter, hot carcass weight (HCW) and the GR measurement were taken. Carcasses were chilled for approximately 24 hours at 5' C before pH and meat colour measurements were made at the 12th/l3th rib on M. Longissimus thoracis et Zumborum (LL) muscle. Meat colour was measured using a Minolta CR-300 model chromameter set on the L*, a* and b* system (where L* = relative lightness, a * = relative redness and b * = relative yellowness) after the meat was allowed to bloom for 30 mins. The chroma value (a*2 + b*2)' was determined and used as a dependent variable along with the L*, a* and b* values. A Jenco 6009 pH meter fitted with a spear electrode and temperature compensation was used to measure the muscle pH. The independent variables analysed were pH, HCW, GR, fat depth at the C site (Fat C), age at slaughter and genotype. Both linear and quadratic models were tested by regression. Hot carcass weights ranged from 19.2 to 35.4 kg with a mean (+ SD) of 26.4 + 3.49 kg. GR ranged from 8 to 25 mm with a mean of 15.7 & 3.56 mm. The mean pH was 5.57 + 0.13 with a range of 5.34 to 6.11. Of the variables analysed genotype, age at slaughter, Fat C, GR and HCW all had no effect on the relationship between pH and the colour measurements. pH was significantly related to (P c 0.001) L*, a*, b* and chroma values (Table 1). There was no quadratic effect with pH displaying a negative linear correlation with all dependent variables. Table 1. Relationship between colour parameters and pH (R2; RSD) . HOPKINS, D-L., HOLST, P.J., HALL, D.G. and ATKINSON, W.R. (1995) Amt. J. Exp. Agric. 35: 693-7. MACDOUGALL, D.B. and RHODES, D.N. (1972). J. Sci. Fd Agric. 23: 637-47. 353