Bioaccessibility of B vitamins in faba bean extrudates: Influence of protein ingredients and added ascorbic acid in high-moisture extrusion

High-moisture extrusion (HME) is utilised to produce textured vegetable protein products from legume protein ingredients. However, information on the nutritional quality of these legume-based extrudates is scarce. This study aimed to investigate the retention and bioaccessibility of thiamin, riboflavin, niacin, and folate in faba bean extrudates produced using HME. The influence of different protein ingredients and ascorbic acid added to the feed water on B vitamin bioaccessibility was examined using a static in vitro digestion model. Additionally, the visual appearance, colour, mechanical properties, and protein solubility of the extrudates were assessed. The retention of B vitamins was high during the HME of different ingredients, irrespective of the feed water composition. The bioaccessibility of thiamin, riboflavin, and niacin was consistently around 100%. For folate, the bioaccessibility was 34-41% in the ingredients and 44-58% in the extrudates, thus indicating improved bioaccessibility due to HME. The ingredient type and the added ascorbic acid did not influence bioaccessibility, although the extrudates exhibited differences in visual appearance, colour, mechanical properties, and protein solubility. This study provided novel insights into the B vitamin bioaccessibility in HME-produced extrudates. Regardless of the macrostructures formed during HME, thiamin, riboflavin, and niacin were well released from all faba bean matrices, and they were stable under digestion conditions. The instability of folate vitamers during digestion impaired their bioaccessibility; however, HME was beneficial for folate bioaccessibility. Overall, a typical portion (100 g) of extrudates can be regarded as a promising source of B vitamins.