From mothers and grandmothers we have acquired a lot of knowledge about cooking. One of the traditional wisdom is that spinach should not be reheated. No one really knows why, but you stick to the recommendation, because a true core must be tuned. Or not?
Nitrate content in spinach
Spinach is one of the vegetables that accumulate abundant nitrate from the soil during the growth phase. Nitrate is bacterially converted to nitrite over time and then to toxic nitrosamines. Nitrate itself is not harmful to human health. Only after conversion to nitrite can it endanger human health.
Conversion of nitrate into nitrite
The conversion of nitrate into nitrite is carried out by bacteria, for example during prolonged storage of food at room temperature. On the other hand, if the prepared spinach is stored in the refrigerator, bacterial growth is largely contained and thus the formation of nitrite. So the recommendation in the days of our grandmothers had their meaning, because at that time there were still no refrigerators in many households.
Why is nitrite dangerous?
Nitrite can affect our health in two ways:
- Nitrite can be used to form carcinogenic nitrosamines in conjunction with protein degradation products (called secondary amines), which are naturally found in many foods and are also produced during digestion.
- High doses of nitrite can inhibit the transport of oxygen in the blood of infants and cause "methaemoglobinaemia" with cyanosis.
Tips for handling spinach
- Consume spinach as fresh as possible and remove the stems and very large leaf ribs when brushing fresh spinach leaves.
- Thorough washing or blanching can reduce the nitrate content since nitrate is water soluble.
- Avoid long warm-up times.
- After the first preparation, allow the vegetables to cool quickly so that nitrite does not form as much as possible. It is best to pour the spinach into a clean container and put it in the fridge for max. 1 day. Then you can reheat the vegetables without hesitation.
- Infants and toddlers should not eat warmed up spinach.
- The recommendations apply equally to all nitrate-rich vegetables, such as Swiss chard, kale, beetroot, lettuce or rocket.