What is a major source of salad contamination that can be treated by immersion in boiling water for thirty seconds?

The major source of salad contamination that can be treated effectively by immersion in boiling water for thirty seconds is often associated with celery. This vegetable can harbor pathogens like E. coli or Salmonella, which may originate from soil, water, or exposure during handling.

Immersing celery in boiling water can kill many of these harmful microorganisms while preserving the texture and flavor of the vegetable. This method, known as blanching, is effective because the high temperature can quickly reduce the microbial load without cooking the celery thoroughly.

While other vegetables like spinach, romaine lettuce, and cucumber can also present safety concerns, they may require different handling or washing procedures to ensure they are safe to eat. For example, romaine lettuce has been linked to several recalls due to E. coli outbreaks and usually requires thorough washing rather than blanching. Spinach may also be contaminated but is often better cleaned by washing rather than boiling, as it can wilt and lose nutritional value in boiling water. Cucumbers are less commonly associated with serious contamination issues compared to celery, making them a lower priority for this specific treatment method.