We thank Mr Tay Kian Tiong for his feedback on time-stamping guidelines for cooked food ("Standard 'consume by' guidelines hitting expiry date?"; last Monday).

The National Environment Agency (NEA) would like to share what the time-stamp is intended to convey.

Food-borne pathogenic bacteria multiply quickly between 5 deg C and 60 deg C. If a cooked food item is contaminated with such bacteria, for example as a result of cross-contamination, keeping that contaminated food item at such ambient temperatures for about four hours could result in the bacteria multiplying to reach sufficient levels that could cause food poisoning when the food item is consumed.

Cooked food stalls in foodcourts, coffee shops and hawker centres generally prepare smaller portions of food and serve it within a shorter timeframe or upon order. Some also have a final cooking step, such as blanching or frying, before the food is served.

The risk of cooked food being kept for prolonged periods at such ambient temperatures is thus lower.

As part of our inspection regime, our inspectors do remind operators not to prepare too much food in advance, in view of such concerns.

In contrast, catering operations involve advance preparation of large quantities of food for consumption at a later time.

Every catered meal thus carries an inherent risk, as the food is not consumed immediately after it is prepared.

Good food and hygiene practices are thus imperative.

The NEA has made it mandatory for caterers to adopt a Food Safety Management System, to ensure such good practices are observed.

To reduce the risk even further, caterers are required to time-stamp the meals to inform consumers of the recommended "consume by" time, which is set at four hours from the time a cooked dish is placed at the temperature danger zone of between 5 deg C and 60 deg C.

In most cases, if there had not been any contamination initially, the food may be safe to eat even after the recommended "consume by" time.

Consumers should thus exercise judgment should they decide to consume food past the stated "consume by" time.

There are also other practical ways to reduce food wastage, such as refraining from over-ordering, and downsizing the portions of each dish if there are a variety of dishes served.

Consumers can download an online handy guide (Love Your Food - A Handy Guide To Reducing Food Wastage and Saving Money), available at www.cgs.sg/FWRguide, which provides a wide range of useful tips on how to reduce food wastage at home and when eating out.

Adeline Leong (Ms)

Director, Food and Environmental Hygiene Department

National Environment Agency