Browsing by Author "Nieminen, Faisa"

Niacin is a water-soluble B-group vitamin, and it is a general name for nicotinic acid (NA) and nicotinamide (NAM). It is present in foods as available or bound niacin, which is not absorbable. Currently, the main sources of niacin in Finnish diets are meat and dairy products and with the recommendations to shift towards more plant-based diets, a question is raised if legumes would make potential protein-rich sources of niacin. Therefore, this thesis aimed to investigate legume ingredients as potential protein-rich sources of available niacin. Available niacin was studied from legume ingredients, extrudates, and seeds as a sum of NA and NAM. Stability of available niacin in high moisture extrusion was investigated and the influence of germination on available niacin was studied. Additionally, the propotions of bound niacin in legume flours and seeds were investigated. Available niacin was extracted with mild acid hydrolysis from legume ingredients, extrudates, and seeds. To study bound niacin, total niacin was extracted with acid-alkaline hydrolysis from legume flours and seeds. Ultra-high performance liquid chromatography and fluorescence detection (UHPLC-FLD) with post-column derivatisation were used for the quantification of NA and NAM. Oligosaccharides were analysed using high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) to monitor the germination process. This thesis found that legume ingredients were good sources of available niacin, except for protein isolates. Furthermore, available niacin remained stable in high moisture extrusion and available niacin contents were higher when protein concentrates were favoured as ingredients, rather than protein isolates. Generally, legumes contained more NAM than NA. Germination increased available niacin in faba bean seeds by 30–40%, and oligosaccharide contents decreased. The results of this thesis assumed that legumes contain 20–60% of their niacin in bound forms. However, future research is needed to study bound niacin and niacin bioavailability in legumes, for instance, with a more sensitive and selective tandem-mass spectrometry (LC-MS/MS).