Microwaving frankfurters cuts Listeria risk – Study
The research, carried out by Colorado State University, also raised concerns that labelling on the majority of frankfurters failed to indicate vital information such as cooking time and power settings - despite the fact that the sausages are known have the potential to carry the deadly bug.
Microwaves and hotdogs
The investigation focussed on the effects of microwaving on ready-to-eat meats such as frankfurters in “enhancing the microbial safety of such foods”.
Food cooked or reheated in microwaves can have hot and cold spots because of the possibility of uneven heat distribution. This can raise concerns about the survival of pathogens after microwaving, said the report. Allowing the products to stand for two minutes following reheating helped reduce hot and cold spots and improve protection from pathogens.
The study evaluated a range of differing time and power combinations of microwave reheating after the frankfurters had been stored in a domestic refrigerator for between zero and seven days.
Greatest reductions in L.monocytogenes occurred when frankfurters were cooked for 75 seconds at a setting of 1100 W. But the efficacy of this treatment depended on the levels of pathogen contamination in the hotdogs. This concentration was linked to the product’s packaging conditions and length of storage. Longer microwaving time is needed for products that have supported growth to higher than 3.7 log CFU/cm2, the team found.
The group also concluded that those frankfurters formulated with antimicrobials that limit the development of pathogens during storage showed a fall in Listeria counts after exposure to microwaves for 60-75 seconds irrespective of packaging conditions or length of storage time.
Better reheating instructions
The researchers alsohighlighted that “appropriate reheating recommendations for these products is critical” – particularly for high-risk groups such as the elderly.
But the study noted out that “most commercial brands of frankfurters do not provide instructions or guidelines for reheating on their labels- even though it is known that frankfurters may potentially be contaminated with L.monocytogenes”.
Instructions that do not indicate the power level and a reheating time may be inadequate – especially when “the product is formulated without lactate/diacetate due to the potential of this type of product to support growth of the pathogen in high numbers”, said the research.
It recommended that reheating instructions must be specifically designed for individual products and consider variations such as the maximum outputs for differing microwaves, the amount and age of the product to be reheated as well as the presence of antimicrobial compounds in the frankfurters.
‘Microwave Oven Heating for Inactivation of Listeria Monocytogenes on Frankfurters before Consumption”, by Patricia A Kendall et al appears in the Journal of Food Science, Sept 2009.
