Microwave Processing to Destroy Salmonellae in Corn-Soy-Milk Blends and Effect on Product Quality

Enriched corn-soy-milk (CSM) blends were inoculated with Salmonella senftenberg and packed in 50-lb (22.7 kg) bags. The inoculated product and CSM bags containing natural salmonellae contamination were heated from 21° to 56.7°C through 82.2°C in 3.9 – 10 min, respectively, using a 60 Kw (2450 MHz) continuous microwave tunnel, and then palletized with and without 4-cm spacers between rows. Spacer palletized bags cooled to 43°C after 9.7 hr with moving air and after 23.3 hr without moving air, but 60 hr was required with no spacers. Initial most probable numbers (MPN) of 4 × 10² cells/g for S. senftenberg were reduced 10²-fold to 10⁵-fold after processing at 56.7° through 82.2°C, respectively. Nutritional damage occurred at process temperatures of 77.8° and 82.2°C. At 61.1° and 67.2°C, MPN were reduced 2 × 10³-fold with no significant change in rheology, moisture, color, vitamins A and B₁, available lysine, and protein efficiency ratios.