Purpose: Develop science based heating instructions for microwave heating of chicken nuggets and validate the instructions using microbial challenge study.
Methods: Two household microwave ovens of low (700 W) and high (1,350 W) power were used. Temperature profiles were obtained by placing frozen chicken nuggets (4, 6 or 8) at two different positions (edge or center) and heated. Temperature profiles (24) were obtained for each combination of pieces, location and oven, and times to reach 70, 72.2 and 73.8°C were determined. Heating times were selected based on 90, 95 and 99% confidence intervals (CI) and chi-square value. Chicken nuggets were inoculated in the center with a five-strain Salmonella spp. cocktail (ca. 7.22 log CFU/g) and heated for the calculated times. Salmonella populations were determined by plating and enrichment methods subsequent to heating and after standing time (2 min).
Results: Salmonella spp. reductions of 6.56 log CFU/g were observed in chicken nuggets (4 pieces, center) heated for 86 s (99% CI; target temperature, 73.8°C) in the low power oven. Longer times (187 s) resulted in 7.22 log CFU/g Salmonella spp. reductions when chicken nuggets were in groups of eight. Use of higher wattage microwave oven resulted in similar Salmonella spp. reductions with chicken nuggets at the center, even with shorter heating times. Incorporation of standing time after heating eliminated Salmonella spp. regardless of the power of the oven, location and the number of chicken nuggets.
Significance: Position, number of nuggets and the power of microwave oven affected Salmonella spp. destruction. Standing times resulted in the elimination of Salmonella spp. as temperature equilibration may be achieved throughout the product.