Food safety expert explains the difference between best before and best before dates

What is the difference between use by best before the expiry date, use by dates are stricter than other date markings, as they can refer to the safety of the food, particularly for infant formula or fresh produce like meat, fish and poultry, a Singapore Institute of Technology associate professor said.

As they tend to turn bad, spoil or become rancid faster than other types of food, these items should be consumed as much as possible, said Dr Siti Noorbaiyah Abdul Malek, an expert in food safety and quality.

Best before dates, on the other hand, indicate how long food will last before it starts to lose its quality.

A packet of biscuits may be found soft or crisp after the indicated 'best before' date, but they can still be edible, according to Dr Siti.

She added that the food was properly stored, under the right temperature and environment.

The Singapore Food Manufacturers' Association said that a best before date is akin to a recommendation based on the manufacturer's experience. After the date, the food could still be edible, but might have lost its texture or flavour.

Expire by and use by date marks can be taken as hard deadlines after which a product might be contaminated, said the IT director Ang Khim Whee, who also sits in Enterprise Singapore's Food Standards Committee and the National Codex Committee.

How do manufacturers determine the dates?

Through lab tests, experts said. According to Mr Ang, the lab will test five different parameters, including the total plate count and escherichia coli E. coli bacteria.

The total plate count is a measure of the bacteria count of the product over time, said Mr Ang. A small sample of the product is diluted, then placed in a petri dish and tested.

Siti said manufacturers could conduct shelf-life studies on products through a real-time or accelerated approach. For real-time testing, manufacturers keep food at the storage conditions specified on their label and evaluate the food intermittently to see how it has deteriorated over the course of the study.

She said that when the extent of deterioration has compromised the quality of the food, they can indicate the shelf life of the food.

In the accelerated approach, manufacturers keep food at elevated temperatures to speed up deterioration.

Once they determine that the quality of the food has been compromised, they can extrapolate shelf life based on certain mathematical models that can be used to predict results. Food manufacturers usually choose best before dates conservatively well before the time when food would spoil and become inedible, Dr Siti said.