Potato chips are common snacks, so deliciously crispy that you cannot stop eating them. But are you aware that antioxidants are in their ingredient list? Besides, when people crave for food, some would go for preserved fruits, such as dried salted plums and preserved pomelo. Why do they have a rather long shelf life? In fact, preservatives and antioxidants are often added to pre-packaged food products in their processing by food manufacturers to prolong their shelf life and prevent spoilage.
What are preservatives and antioxidants?
They are food additives often used in the food processing industry.
Preservative: inhibits deterioration of food (including fermentation and acidification) caused by microorganisms to prolong its shelf life. In fact, people started to use saltpeter (naturally decompose to form sodium nitrate) to preserve meat over a thousand years ago. For common food like ham and sausage, it is susceptible to contamination by Clostridium botulinum and may lead to food poisoning, if potassium nitrate (as preservative and colour retention agent) is not added and not subject to adequate heat treatment. The correct use of preservatives in suitable amounts is actually essential to enhancing food safety.
Antioxidant: prevents or retards the deterioration of food caused by oxidation to prolong its shelf life and preserve its quality. Antioxidants, such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), are usually added to snacks, like potato chips and nuts, to protect them from deleterious effects of oxidation and rancidity. The addition of antioxidants in food helps to keep its flavours stable within its “expiry date”.
The enacted “Standards for Use of Preservatives and Antioxidants in Food” of Macao defined 39 types of preservatives and antioxidants that are permitted for use in food, which include sorbic acid, potassium nitrate and nisin, etc.
Regulation on use of preservatives and antioxidants in food in Macao
To reinforce the control of food safety in Macao, the Administrative Regulation No. 7/2019 “Standards for Use of Preservatives and Antioxidants in Food” has been enacted, which expressly defines the principles of the use of preservatives and antioxidants, the types of preservatives and antioxidants permitted in food, and the maximum levels of use of certain preservatives and antioxidants in 16 food categories, including dairy products, fruits and vegetables, beverages, and ready-to-eat snacks. These stipulations meet the regulatory needs for Macao’s food safety and the market so as to safeguard the health of Macao residents.
How are preservatives and antioxidants linked to health?
The preservatives and antioxidants that are lawfully permitted for use, as stipulated by the food safety standards of Macao, are food-grade food additives that have been assessed to be safe for food use. The public need not be worried over their presence in food since normal consumption of pre-packaged food products is unlikely to have adverse effects on health. Eating a diverse and balanced diet, including more fresh food products in meals, is the best way to prevent excess intake of a single food item which may lead to nutritional imbalance.
What should be noted by the food industry with regard to the use of preservatives and antioxidants?
As prescribed by the food safety standards, the use of preservatives or antioxidants has to follow the good manufacturing practices, including: The amount of preservatives or antioxidants added to food during the production process should be limited to the minimum possible dose required to achieve the desired effect. As for the presence of preservatives or antioxidants in food resulted from the transfer of these additives into food through their ingredients or packaging materials, it is necessary to keep their amounts transferred to food as minimum as possible to prevent consumption of them in excessive amounts and posing risk to consumers.
The purity and quality of food additives added to food by food manufacturers have to be of food grade quality.
As prescribed by the food safety standards, “When a mix of several preservatives or antioxidants is added to the same food, the sum of the amount of each preservative or antioxidant used in comparative to its maximum use level, by proportion, shall not exceed 1”. What does it mean?
Though preservatives and antioxidants are rather similar in functions and purposes, they are not mutually replaceable or substitutable. In this connection, the food industry often adds a mix of several preservatives or antioxidants into the same food. To safeguard public health, when a mix of several preservatives or antioxidants is used, the sum of the amount of each preservative or antioxidant used in comparative to its maximum use level, by proportion, should not exceed 1.
Example: A food manufacturer uses sorbic acid and benzoic acid in the production of a kind of dried mangoes. The table below uses the actual quantity used to calculate whether the amounts of sorbic acid and benzoic acid used have exceeded their permissible maximum use levels.
Preservatives or antioxidants
Maximum use level(s)
Actual quantity used
Proportion of amount use
Sum of proportions of mixed use
As indicated in the above table, the sum of the proportions of sorbic acid and benzoic acid when used together is greater than 1. Hence, it is necessary to adjust their actual quantity used to ensure the total quantity of these acids in the product remains within the safety range.