The temperature in the autoclave process is a critical factor that influences the quality and safety of low-acidity foods packaged in hermetically sealed containers. The food industry constantly faces the challenge of balancing quality and safety. While high temperatures over extended periods effectively reduce bacterial presence and ensure food safety, they can negatively impact organoleptic qualities such as taste, color, texture, and other properties.
The food industry generally sacrifices some quality to enhance safety and extend product shelf life. At the same time, autoclave suppliers are dedicated to developing technologies that optimize food quality without compromising safety.
A uniform distribution of heat within the autoclave chamber is crucial to eliminate any risk of "cold spots" or minimize the duration at the "slowest heating point." Understanding these concepts is essential, as they are often subjects of debate. A cold spot refers to any area in the autoclave where the sterilization temperature is not reached within the time specified in the recipe. It is also considered a cold spot if the temperature is reached too late, requiring an unacceptable extension of the scheduled time, which can lead to overcooking or destruction of some or all food products in the batch.
The slowest heating point affects the overall quality of the food product, though not to the extent that it requires excessively extending the scheduled process time. Cold spots and slow heating points are usually located in the spaces between containers. The location of these points can vary according to the size and shape of the packaging, making it necessary to obtain heat distribution maps for each packaging format.
Autoclave manufactures prioritize technologies that ensure rapid and uniform heating, eliminating cold spots and minimizing slow heating zones to achieve the best thermal uniformity in the batch. The time from the start of heating until all points reach the sterilization temperature is known as the Come-Up Time (CUT).
Once all points reach the autoclave temperature, the next challenge is to maintain them within a minimal range of variation. High-quality autoclaves keep all points within +/- 0.5 ºC (+/- 0.9 ºF). A temperature drop below the validated setpoint in the recipe is considered a deviation that must be managed according to established quality control protocols.
The autoclave's control setpoint should be set 0.5 ºC above the minimum sterilization temperature determined during recipe validation to prevent regular control fluctuations from causing a process deviation (e.g., 121.5 ºC when the minimum sterilization temperature is 121.0 ºC).
Heat distribution testing in the autoclave and recipe validation are typically conducted by Thermal Process Authorities accredited by the FDA or other food safety organizations. Their expertise is essential to achieve the optimal balance between safety and quality.