Which of the following requires a variance from the Regulatory Authority?

Using food additives for preservation requires a variance from the Regulatory Authority because it involves altering the standard food preparation and safety practices dictated by food safety regulations. Variances are granted when a food establishment seeks to implement methods that are different from the conventional practices, particularly when those methods can potentially impact food safety.

When a food additive is used for preservation, it is essential to ensure that its use complies with specific safety standards as defined by regulatory agencies. This is because food additives can affect the chemical composition of food products, potentially leading to unforeseen health risks if not properly managed. Additionally, the agency may need to assess the specific additive's safety and effectiveness for the intended use, requiring documentation and possibly further testing.

The other choices involve practices that may not necessarily require a variance because they relate to standard operational procedures that do not inherently alter the food safety regulations significantly or don't require special permissions to deviate from established guidelines. For instance, cooking food without a thermometer is discouraged for food safety reasons but does not require a variance; rather, it is simply considered a practice that may lead to unsafe food handling.