Safe and shelf-stable natural casing using hurdle technology

Safe and shelf-stable natural casing were prepared using a combination of hurdles viz. reduced water activity, packaging and gamma irradiation. Washed lamb intestines were treated with common salt to reduce water activity to 0.80 ± 0.02, packed in polyethylene bags and subjected to gamma-irradiation (5 and 10 kGy). Control non-irradiated samples had high total viable counts (106 CFU/g), aerobic spores (103 CFU/g), spores of sulphite reducing clostridia (103 CFU/g), potentially pathogenic bacteria such as staphylococci (104 CFU/g) and coliforms (102 CFU/g). Treatment with gamma radiation resulted in a dose dependent reduction in counts of these microbes. A dose of 5 kGy was sufficient to reduce total viable counts by three log cycles; spore counts by two log cycles and completely eliminate staphylococci and coliforms. Samples subjected to a 10 kGy dose were devoid of any viable microbes. The reduced water activity of the product prevented growth of the microbes in natural casings during storage at room temperature. Sausages prepared using hurdle processed natural casing were examined for sensory and textural properties. It was observed that product acceptability and mechanical strength was not affected by radiation processing. Our studies indicated that shelf-stable and safe natural casing could be prepared using a combination of hurdles.