Further research on vitamin K is necessary as growing evidence of vitamin K's importance in human health beyond blood coagulation and bone health is emerging. We present a cost-effective LC-ESI-MS/MS method for quantification of phylloquinone (PK), and menaquinones (MK) 4-10 in food using deuterium labelled (d7) compounds (d7-PK, d7-MK-4, d7-MK-7 and d7-MK-9) as internal standards. The validation of the method included assessment of matrix effect, limit of quantification (LOQ), precision, and trueness. The LC-ESI-MS/MS method runtime is 9 min. The method was compared to a validated LC-FLD method (CEN 14148), for quantification of vitamin K in broccoli, cheese, natto, liver, and microalgae. LOQs of the LC-ESI-MS/MS method were ≤4 µg/100 g food. The intra- and inter-assay precision was <15% for PK, MK-4, MK-7 and MK-9; <20% for MK-5, MK-8, and MK-10, and ≤25% for MK-6. No significant differences between the quantified content by the LC-ESI-MS/MS and LC-FLD methods were observed.

With the aim to upcycle fish side-streams, enzymatic hydrolysis is often applied to produce protein hydrolysates with bioactive properties or just as a protein source for food and feed. However, the production of hydrolysates generates a side-stream. For underutilized fish and fish backbone this side-stream will contain fish bones and make it rich in minerals. The aim of this study was to assess the relative bioaccessibility (using the standardized in vitro model INFOGEST 2.0) of minerals in a dietary supplement compared to bone powder generated after enzymatic hydrolysis of three different fish side-streams: undersized whole hake, cod and salmon backbones consisting of insoluble protein and bones. Differences in the bioaccessibility of protein between the powders were also investigated. The enzyme hydrolysis was carried out using different enzymes and hydrolysis conditions for the different fish side-streams. The content and bioaccessibility of protein and the minerals phosphorus (P), calcium (Ca), potassium (K) and magnesium (Mg) were measured to evaluate the potential of the powder as an ingredient in, e.g., dietary supplements. The bone powders contained bioaccessible proteins and minerals. Thus, new side-streams generated from enzymatic hydrolysis can have possible applications in the food sector due to bioaccessible proteins and minerals.

Vitamin K describes a group of fat-soluble vitamers namely phylloquinone and menaquinones. The growing evidence for vitamin K's role beyond blood coagulation, and the possible differences between the vitamers are emerging. Knowledge of the content of menaquinones in different food matrixes and the potential differences in bioaccessibility between the vitamin K vitamers and food matrixes are limited. In this study, the bioaccessibility was assessed using the INFOGEST 2.0 static in vitro digestion model optimised by including a Danish standard meal. The presence of the standard meal was crucial to obtaining a robust and stable digestion model. The bioaccessibility of the Danish standard meal, water, vitamin K standards, vitamin K supplements, broccoli, spinach, natto, pasteurised whole egg and canola oil was assessed by three replications. The bioaccessibility was in the range 30%–102%. The lowest bioaccessibility was observed in broccoli while the highest bioaccessibility was found in egg and canola oil. No competition in the bioaccessibility between vitamin K vitamers and vitamin D was observed.

Vitamin K is a fat-soluble group of vitamers consisting of phylloquinone (PK) and menaquinones (MKs). To date, only a daily reference intake for PK is set; however, in the last decade, research studying the correlation between MKs intake and improvement of health in regards to cardiovascular diseases, bone metabolism, and chronic kidney disease has been conducted. MKs are synthesised by bacteria in the fermentation process of foods, e.g., cheeses. The content and bioaccessibility of vitamin K vitamers (PK, MK-4, MK-5, MK-6, MK-7, MK-8, MK-9, and MK-10) were assessed in eight different cheese products differing in ripening time, starter culture, fat content, and water content. The bioaccessibility was assessed using the static in vitro digestion model INFOGEST 2.0. Variation of the vitamin K content (<0.5 μg/100 g–32 μg/100 g) and of the vitamin K bioaccessibility (6.4–80%) was observed. A longer ripening time did not necessarily result in an increase of MKs. These results indicate that the vitamin K content and bioaccessibility differs significantly between different cheese products, and the ripening time, starter culture, fat content, and water content cannot explain this difference.