Degradation kinetics of folate (5-methyltetrahydrofolate) in navy beans under various processing conditions

The 5-methyltetrahydrofolate (5MTHF) is the predominate folate form that exists in navy beans and possesses health benefit to human beings. Understanding the degradation kinetics of 5MTHF during navy bean processing would provide useful information that characterizes the influence of processing conditions in order to minimize folate degradation and to maintain overall products quality during the beans’ production. The bio-specific procedures were used for sample preparation and purification, and HPLC techniques were subsequently used for identification and quantitative analysis of 5MTHF in the different treated bean samples. Losses of 5MTHF have been observed in all processed navy beans. Experimental results showed that the soaking time and the seed-to-water ratio were the two most critical factors that affected the stability of 5MTHF during the soaking process. The longer soaking times with larger amounts of soaking water caused higher degradation of 5MTHF. Cooking time and cooking media also played a key role in the degradation of 5MTHF in beans. Pressurized cooking showed the highest reduction of 5MTHF among all the treated bean samples. The treatment causes greater folate loss mainly through the promotion of water penetration and high diffusion, leading to more folate being released from the bean matrix, and accelerating the oxidation and decomposition of folates during cooking.