Effect of gamma radiation on the quality of bacon

‘Collar’ bacon (4·65% NaCl; 104 mg kg −1 NO 2 : 91 mg kg −1 NO 3 ) was sliced and packaged. Twenty five ‘vac’ packs (average wt. = 76 g) were prepared. Five served as ‘controls’ and 15 were randomly assigned to five irradiation treatments ranging from 1·05 kGy to 17·3 kGy. The source was a mark ‘4’ cobalt 60 ‘Hot Spot’ (Becton-Dickinson) giving a dose rate of 2·1 kGy h −1 at the time of the experiment. After overnight storage (4°C), the bacon was tested bacteriologically and the quality (appearance, odour, colour) was assessed. Results indicated that total bacterial numbers were reduced by c. 5 log cycles after exposure to 17·3 kGy. No lactic acid bacteria survived 6·3 kGy of radiation. In all cases, except for odour, most of the scores were in the excellent category. The odour was described variously as ‘foreign’, ‘unbacon-like’ or ‘metallic’. Two of the treatments (10·5 and 17·3 kGy) exceeded the W.H.O. guideline (≯ 10 kGy) for irradiated food. Further work is required to establish the effect of irradiation on bacon after extended storage, particularly with regard to odour changes.