1. Why are preservatives and antioxidants added to food?
Preservatives are added to food so as to prevent or slow down the growth of micro-organism, such as moulds, yeasts and bacteria in food. Preservatives can inhibit, retard or arrest the process of fermentation, acidification or other deterioration of food.
Antioxidants are added to food so as to protect food from turning rancid or changing colour. Antioxidants can delay, retard or prevent food from deterioration due to oxidation .
2. What are the commonly used preservatives and what kinds of foods usually contain them?
Sulphur dioxide, sorbic acid and benzoic acid are examples of some commonly used preservatives. Sulphur dioxide is usually added to dried fruit, pickled vegetables and sausages to inhibit the growth of yeasts and bacteria and to preserve the colour of some fruits such as apricots and raisins . Sorbic acid can be found in cheese and wine in order to retard the growth of moulds while soft drinks and ketchup may contain benzoic acid for inhibiting the growth of yeasts and moulds.
3. How can I know if preservative or antioxidant is added to food?
According to the Food and Drugs (Composition and Labelling) Regulations, the functional class and the names or numbers in the International Numbering System for Food Additives (INS) of the preservative or antioxidant can be found in the ingredient list of most prepackaged food. Sometimes, the prefix "E" or "e" may be added.
For instance, if sulphur dioxide is added to the food as a preservative, it has to be labelled in the ingredient list as either
- Preservative (sulphur dioxide) or
- Preservative (220) or
- Preservative (E220) or
- Preservative (e220)
To check the INS number of some of the permitted preservatives and antioxidants in Hong Kong, you may visit the following link: http://www.cfs.gov.hk/english/whatsnew/whatsnew_fstr/files/ins_list_num_order.pdf
4. How are preservatives and antioxidants regulated in Hong Kong?
In Hong Kong, most food safety related rules and regulations are contained in Part V of the Public Health and Municipal Services Ordinance, Cap. 132. The Ordinance stipulates that all food on sale must be wholesome, unadulterated and fit for human consumption. There is also a set of subsidiary legislation which spells out the standards for specific food products or substances allowed in food. The control on the use of preservatives and antioxidants in food is governed by the Preservatives in Food Regulation, Cap. 132BD, which stipulate that any food being imported, manufactured for sale, or sold should only contain permitted preservatives or antioxidants and in the proportion that does not exceed the maximum permitted levels. Details of the legislation are available at the website www.elegislation.gov.hk.
5. Is it safe to consume food containing preservatives and antioxidants?
At the permitted level of use and under normal level of consumption, food containing preservatives and antioxidants would not lead to health problems. However, people with allergic conditions, such as asthma patients, may experience hypersensitive reaction to certain preservatives such as sulphur dioxide in food. Such consumers should read the ingredient list to see whether those preservatives or anti-oxidants that they are allergic to are used in the food.
6. What can consumers do in order to prevent consumption of excessive preservatives and antioxidants from food?
They should
- maintain a balanced diet in order to avoid excessive exposure to any particular preservative or antioxidant from a small range of food;
- purchase food from reliable shops; and
- read the label carefully on prepackaged foods to identify products containing preservatives or antioxidants especially among people with allergic conditions.
7. What can the food trade do to ensure preservatives and antioxidants being used are safe for human consumption?
They should
- comply with the Preservatives in Food Regulation (including the types and maximum permitted level of preservatives present in food);
- adhere to the Good Manufacturing Practice in a way that only the minimum amount and suitable type is added to food to achieve the desired technological effect; and
- source foods and ingredients from reliable sources.
8. What can I do if I want to know more about Preservatives in Food Regulation?
You may visit the following link to know more about the Regulation
http://www.cfs.gov.hk/english/whatsnew/whatsnew_fstr/files/User_Guideline_e.pdf
9. How is Sulphur dioxide regulated in Hong Kong when it is used as a preservative in pre-packaged food? 
When Sulphur dioxide is used as a preservative in pre-packaged food in Hong Kong, there are legal requirements governing its level and the label of the pre-packaged food.
Under Schedule 1 to the Preservatives in Food Regulation (Cap. 132BD), specific preservatives/antioxidants not exceeding the maximum permitted level are allowed to be used as food additives in the corresponding foods in Hong Kong.
Under Schedule 3 to the Food and Drugs (Composition and Labelling) Regulations (Cap. 132W), a food additive (preservative/antioxidant, etc.) constituting one of the ingredients of a food shall be listed by its functional class and its specific name or its identification number under the International Numbering System for Food Additives adopted by the Codex Alimentarius Commission. If sulphur dioxide is added to a prepackaged food as a preservative, even though the level used does not exceed the statutory maximum permitted level, the description of either “preservative (sulphur dioxide)”, “preservative (E220)” or “preservative (220)” shall be specified in the list of ingredients on the food label of the product concerned. Also, if the food contains sulphite (sulphur dioxide) in a concentration of 10 parts per million or more, the name and functional class of the sulphite shall be specified in the list of ingredients.