The correct answer is Microbial activity. Sulphur dioxide (SO2) and sulphites are traditionally used as antioxidant and preservative in fruit and vegetable products, dried fruits. The main advantage is the combination of antioxidative activity with its ability to inhibit polyphenol oxidase, which is catalysing browning of food products. Furthermore, sulphur dioxide acts as food preservative preventing microbial growth. However, SO2 and sulphites strongly reduce vitamin B1 uptake. Reduced uptake of this vitamin can lead to several health problems such as chronic headache and disturbance of the memory.