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Effect of calcium chloride, zinc chloride, and water infusion on metmyoglobin reducing activity and fresh lamb color

A. E. D. Bekhit^*,1, M. A. Ilian^*, J. D. Morton^*, L. Vanhanan^*, J. R. Sedcole and R. Bickerstaffe^*

^* Molecular Biotechnology Group, Agriculture and Life Sciences Division; and and Applied Computing, Mathematics, and Statistics Group, Applied Management and Computing Division, Lincoln University, Canterbury, New Zealand

¹ Correspondence: P.O. Box 84 (phone: 64 (03) 325 3838, ext. 8427; fax: 64 (03) 325 3851; e-mail: bekhita2{at}lincoln.ac.nz).

Calcium chloride (CaCl₂), zinc chloride (ZnCl₂), or water infusions were used to investigate the biochemical factors that affect fresh lamb color, and to examine the role of metmyoglobin-reducing activity in regulating this important quality attribute. Immediately after exsanguination, lamb carcasses (n = 6 per treatment) were infused (10% of BW) with 0.3 M CaCl₂, 0.05 M ZnCl₂, or water via a catheter inserted into the left carotid artery. The right LM was excised at 24-h postmortem and divided into two halves. The caudal portion was cut into 2.5-cm-thick chops and displayed for 6 d under 1,076 lx of white fluorescent lighting at 2°C, whereas the cranial half was vacuum-packaged and stored at 2°C for 3 wk before retail display. Objective color measurements and samples for biochemical analysis were taken at 0, 1, 3, and 6 d of display. In infused carcasses, pH decline was more rapid (P < 0.05) than in untreated controls, and it was greatest for CaCl₂-infused carcasses. Calcium chloride-infused carcasses had lower (P < 0.01) NAD and higher (P < 0.001) NADPH concentrations than water- and ZnCl₂-infused or untreated control carcasses. The negative effects of calcium infusion on fresh lamb color, higher (P < 0.01) metmyoglobin accumulation rate, and lower (P < 0.01) L*, a*, and b* color measurements could be explained by the lower amounts of unbound water (P < 0.01), shorter sarcomere length (P < 0.01), lower NAD concentrations (P < 0.01), and higher lipid peroxidation (P < 0.01). Zinc and water-infusions produced less (P < 0.01) lipid oxidation and improved the color and color stability of fresh lamb (P < 0.001). Rate of lipid oxidation in LM chops was greater (P < 0.01) after 3 wk of vacuum-packaged storage than 24-h postmortem. Metmyoglobin-reducing activities (sarcoplasmic and myofibrillar) were decreased in response to infusion treatments (P < 0.001), and ZnCl₂ infusion resulted in the lowest metmyoglobin-reducing activities (P < 0.001). A significant association between the myofibrillar metmyoglobin-reducing activity and lipid peroxidation was observed, but metmyoglobin-reducing activities were not associated with any improvement in lamb color. Strategies to increase the antioxidant levels in lamb are very important to improve lamb quality, especially during vacuum-packaging storage.

Key Words: Calcium Chloride • Color • Infusion • Lamb • Metmyoglobin-Reducing Activity