Accelerated stability testing subjects a perishable product to stressful conditions to estimate the shelf life in ordinary circumstances. In this testing, companies encourage the product to fail in a short period of time in harsh environments, and use this to estimate what might happen in normal conditions. This eliminates the need to keep products in storage for stability testing for months or years, waiting for them to fail, an approach that would not be practical. Once companies determine a reasonable stability range, they can label future runs of that product with appropriate expiration dates.
Product storage recommendations can specify temperature, humidity, and pH. In stability testing, companies need to keep a sample of the product in the right conditions and monitor it to determine when it fails. Technicians can also perform a second accelerated test to estimate when the product will fail and prepare a reasonable extrapolation of shelf life so the product can be released for sale. The accelerated test speeds the breakdown process with heat, improper humidity, and imbalanced pH.
Controlled conditions are critical for accelerated stability testing. Technicians carefully monitor all environmental factors while they test the product and repeat the testing until it begins to break down. This can be used to evaluate pharmaceuticals and food, both of which come with perishability concerns. In the case of drugs, expired medications might not be effective and could make people sick, while old food might undergo chemical changes or be colonized by organisms that may spoil it and cause illness.
Materials testing firms can evaluate products for shelf life, and companies can also perform their own testing. Regulatory agencies typically have guidelines for accelerated stability testing to make sure it is standardized and safe. Inspectors can request copies of the test records in connection with applications to sell and label products. They may review the documentation to confirm that testing was conducted appropriately and can request a retest is they have concerns.
One concern with this testing is that important physical and chemical changes can take place during accelerated stability testing that wouldn’t happen in normal conditions. For example, if eggs are subjected to high heat, the proteins denature and the eggs enter a cooked state. No matter how long eggs sit in a fridge in recommended storage conditions, they will not cook. Thus, the degree of usefulness from the testing is a subject of debate, because it may be difficult to accurately map results from accelerated stability testing onto normal storage conditions.