Determination of folate contents in some Australian vegetables

The undeconjugated and total folate contents of 22 vegetables commonly available in Australia were assayed with Lactobacillus casei after preliminary digestion with chicken pancreas. The effect of conjugate type and extraction technique on the total folate content of two of the vegetables was also investigated. In two test samples, spinach and Chinese broccoli, deconjugation with chicken pancreas gave slightly higher, but statistically not different (P<0.05), folate values compared to human plasma. Tri-enzyme extraction gave lower folate value compared to single-enzyme extraction, the result was significant (P<0.05) only in Chinese broccoli. Single-enzyme extraction using chicken pancreas was therefore used for extraction of folate in all vegetables. The range of undeconjugated and total folate in vegetables was 27–322 and 68–425 μg total folate/100 g (wet weight), respectively. The average undeconjugated to total folate ratio in 22 vegetables was 0.60, ranging from 0.19 to 0.89. Chinese flowering cabbage contained the highest level of total folate at 425 μg /100 g. Among the rest of the 21 vegetables, four vegetables contained more than 300 μg, five contained 200–300 μg, 10 contained 100–200 μg, and two contained less than 100 μg folate/100 g.