Enhancing vitamin B12 in lupin tempeh by in situ fortification

Abstract

Tempeh is a traditional, fungal fermented Indonesian product, usually made from soybeans. Tempeh is known to contain vitamin B12 which is essential for a healthy human diet. Therefore, tempeh is of particular interest for vegan diets since B12 is normally found only in animal derived products. The vitamin B12 in tempeh is associated with the presence of opportunistic pathogens like Klebsiella pneumoniae. Levels of B12 in tempeh do not sustain the recommended daily intake though. In addition, the use of a food-grade bacterium instead of K. pneumoniae is preferred. Lupin can serve as alternative substrate for soybeans due to its similar protein content, resulting in ‘lupin tempeh’. In this study, Propionibacterium freudenreichii, a food-grade, vitamin B12 producing bacterium, was used in co-culture with Rhizopus oryzae to produce B12-enriched lupin tempeh. A significant increase of vitamin B12 content (up to 0.97 μg/100 g) was achieved by fermenting lupin using a mixed starter of R. oryzae and P. freudenreichii. Other parameters, such as texture and volatile organic compounds, were not affected by the bacterial co-inoculation. Therefore, these results are promising for in situ vitamin B12 fortification of lupin tempeh making it a sustainable protein source for a healthy human diet.