EFFECT OF BONING, ELECTRICAL STIMULATION AND MEDICATED DIET ON THE MICROBIOLOGICAL QUALITY OF LAMB CUTS

Abstract

ABSTRACTSeventy‐three lambs were divided into four treatment groups and fed for 3 months either (1) control diet, (2) control plus 25 ppm of a tertiary amine (N,N‐dimethyldodecanamine), (3) control plus 50 ppm of the amine, or (4) control plus 25 ppm chlortetracycline (CTC). The lambs were slaughtered at the end of the feeding trial. Half of the 146 sides were electrically stimulated (ES). Subsequently, half of the ES and half the nonstimulated sides were hot‐boned and the other halves were cold‐boned at 6 days postmortem. At 6 days postmortem, all racks were vacuum packaged and held at 3°C until 35 days postmortem. Cold‐ and hot‐boned carcasses were processed into lamb chops and packaged in oxygen‐permeable wrap and kept under retail market conditions (5°C and 12 hr of lighting/day). Surface swabs were taken from lamb chops initially and after 3 days of retail storage and from lamb racks at 35 days postmortem. The following statistically significant (P < 0.05) results were obtained. Standard plate counts (SPCs) and psychrotrophic plate counts (PPCs) were consistently higher for hot‐boned lamb chops initially and after 3 days of storage compared with the cold‐boned lamb chops initially and after 3 days of storage. The situation was reversed for the lamb racks after 35 days of storage: hot‐boned racks had lower counts than the cold‐boned racks. PPCs from lamb chops from lambs fed CTC‐supplemented diets were lower than PPCs from lamb chops from lambs fed unsupplemented (control) diets after 3 days of storage. Electrical stimulation exerted no significant effect on surface bacterial numbers.