Comprehensive Reviews in Food Science and Food Safety
) examines the content of, and the effects of processing on, folates in vegetables and fruits. It is well established that folates are beneficial in the prevention of neural tube defects and cardiovascular and neurodegenerative diseases.
Unfortunately, most vegetables and fruits containing folates are consumed after processing, which involves a degree of folate loss. It is important to know the percentage of folate losses during processing and, moreover, the mechanisms underlying those losses. The authors present the current knowledge on folate losses from fruit and vegetables. As they demonstrate, the amount of folate loss depends on the nature of the respective fruit or vegetable and the respective treatment. For example, steaming involves almost no folate losses in contrast to boiling. Two main mechanisms are involved in folate losses: leaching into the surrounding liquid and oxidation during heat treatment.
The researchers found that, overall, folates are higher in vegetables than in fruits. Among fruits, muskmelon, strawberries, and kiwi present higher folate amounts, while peach, watermelon, and apple contain low folate amounts. Pulses, and especially chickpeas, beans, lentils, and peas, present high folate contents, but these values correspond to their raw, dry form. Once the pulses are soaked and cooked in water, the folate content decreases due to dilution. High amounts of folate have also been reported for the “fresh” vegetables from the Fabaceae family, with an average of 52 μg/100 g in green beans and 44 μg/100 g for green peas. Vegetables with high folate contents are spinach, turnip, and cabbage. They also discovered that there can be a large variability in folate content even in the same class of vegetables.