The impact of singlet oxygen on lipid oxidation in foods - Oxidation in Foods and Beverages and Antioxidant Applications - page 63

Fig. 3.3 Reaction products of singlet and triplet oxygen with lipids results in different
breakdown products.
In rapeseed oil, the light-induced promotion of singlet oxidation leads to a
strong increase in the concentration of volatile components such as butenal,
heptenal and several other specific lipid oxidation products (Fig. 3.3). The
headspace analyses of samples subjected to conditions that promote lipid oxidation
by triplet oxygen reveal the presence of a distinctly different set of volatile
oxidation products. Compounds such as hexanal and nonenal appear which
therefore can be considered as markers for triplet oxidation (Van Dyck, 2007).
3.3 Impact of singlet oxygen on quality reduction in foods
Many quality changes in food products are caused by singlet oxidation. Of
course this means that the food product should be packed in a way that contact
with sunlight remains possible. For several food products the flavor change after
storage in sunlight has been known for a long time, but the mechanism behind
this often fast deterioration of food products was only unraveled in the last two
decades. In most cases the molecules that were causing the strange `sunlight'
taste were identified well before the impact of singlet oxygen on the formation
of these compounds was understood.
Probably the two most notorious products sensitive to storage in sunlight are
soybean oil and milk, but also other food products may suffer significant quality
losses when exposed to singlet oxygen.
3.3.1 Vegetable oils
Smouse and Chang (1967) identified that the molecule 2-pentylfuran was
responsible for the `reversion flavor' that appears when soybean oil is stored in
light. Many years later Callison (2001) discovered that a natural photosensitizer
played a role in this process by means of a relatively simple experimental
protocol. Addition of chlorophyll to the oil and subsequent storage in sunlight