Technical note: development and validation of a method using ultra performance liquid chromatography coupled with tandem mass spectrometry for determination of vitamin B12 concentrations in milk and dairy products

Vitamin B12 in Foods, Food Supplements, and Medicines-A Review of Its Role and Properties with a Focus on Its Stability

Vitamin B₁₂, also known as the anti-pernicious anemia factor, is an essential micronutrient totally dependent on dietary sources that is commonly integrated with food supplements. Four vitamin B₁₂ forms-cyanocobalamin, hydroxocobalamin, 5'-deoxyadenosylcobalamin, and methylcobalamin-are currently used for supplementation and, here, we provide an overview of their biochemical role, bioavailability, and efficacy in different dosage forms. Since the effective quantity of vitamin B₁₂ depends on the stability of the different forms, we further provide a review of their main reactivity and stability under exposure to various environmental factors (e.g., temperature, pH, light) and the presence of some typical interacting compounds (oxidants, reductants, and other water-soluble vitamins). Further, we explore how the manufacturing process and storage affect B₁₂ stability in foods, food supplements, and medicines and provide a summary of the data published to date on the content-related quality of vitamin B₁₂ products on the market. We also provide an overview of the approaches toward their stabilization, including minimization of the destabilizing factors, addition of proper stabilizers, or application of some (innovative) technological processes that could be implemented and contribute to the production of high-quality vitamin B₁₂ products.

Analysis of Cobalamin (Vit B12) in Ripened Cheese by Ultra-High-Performance Liquid Chromatography Coupled with Mass Spectrometry

The analysis of natural cobalamins in dairy products still represents an analytical challenge. The matrix’s complexity, low concentration level, light sensitivity, and binding to proteins are just some of the aspects that make their quantification a difficult goal to achieve. Vitamin B12 plays a fundamental role in human nutrition, and its intake is closely linked to a diet that includes the consumption of food of animal origin. In the current literature, few studies have been carried out on the quantitation of cobalamin in ripened cheeses. A sensitive, selective, and robust ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) method was developed, validated, and applied on ripened cheeses from different species (cow, sheep, and goat) purchased from local Italian markets, highlighting species-dependent differences in vitamin B12 concentrations. The vitamin B12 extraction procedure was performed by converting all cobalamins to the cyanocobalamin form. Furthermore, solid-phase extraction was used for matrix clean-up and analyte preconcentration. The proposed method showed good performance in terms of linearity, sensitivity, reproducibility, and repeatability. The mean vitamin B12 content ranged from <LOQ to 38.9 ng/g. Sheep cheese showed the highest concentrations of vitamin B12, with a mean content of 29.0 ng/g.

Determination of Vitamin B12 in Milk and Dairy Products by Isotope-Dilution Liquid Chromatography Tandem Mass Spectrometry

An isotope-dilution liquid chromatography tandem mass spectrometry method was established for the determination of vitamin B12 in milk and dairy products. The samples were spiked with stable isotope-labeled vitamin B12 and digested by pepsin and amylase. The various forms of cobalamin were transformed to cyanocobalamin by potassium cyanide after they were released from the enzymatically digested samples. Cyanocobalamin was extracted and purified by an immunoaffinity SPE cartridge and then measured in multiple reaction monitoring mode (MRM). The linear correlation coefficient (R2) of this method was greater than 0.999 in the range of 2–100 ng/mL. The detection limit and the quantification limit were 0.5 μg/kg and 1.0 μg/kg, respectively. The spiked recoveries ranged from 92.0% to 99.4% at the three spiked levels with the relative standard deviation (RSD) between 1.89% and 4.51%. The measured results of NIST SRM1849a and NIST SRM1869a by the current method are all within the reference value range. The Z value was 0.8 during participating in the FAPAS proficiency test using the developed method in 2021. The method is simple, rapid, accurate, and sensitive, and it is suitable for the determination of vitamin B12 in different types of milk and dairy products such as whey powder, whole milk powder, pure milk, fermented milk, infant formula, and prescription food for special medical purposes.

Determination of cobalamin and related compounds in foods

The microbiological assay of total cobalamin (vitamin B₁₂) by Lactobacillus delbrueckii subsp. lactis ATCC7830 is now used worldwide in food analysis because of its high sensitivity, low running cost, and no expensive instruments. It has been recently reported that some foods contain a substantial number of inactive corrinoid compounds, some of which are active in this bacterium. These results indicate that the microbiological method must be replaced with high-performance liquid chromatography or liquid chromatography/electrospray ionization-tandem mass spectrometry as there can specifically determine biologically active cobalamin. Nowadays, powerful tools, such as immunoaffinity columns, purify cobalamin simply and specifically. In this chapter, we summarized the determination methods of cobalamin and related compounds in foods. Various inactive corrinoids found in foods were also characterized.

Development of a simple and sensitive HPLC-DAD method for quantification of vitamin B12 fortified in infant food

To prevent infants from vitamin B12 deficiency, infant food is designed based on cow's milk or cereal with the fortification of vitamin B12. A method for quantitative determination of vitamin B12 in infant food was developed with hydrophilic high performance liquid chromatography (HPLC) coupled with a diode array detector (DAD). The sensitivity of the detector was enhanced by implementing a 60 mm high-sensitivity LightPipe flow cell, and the limit of detection (LOD) and limit of quantification (LOQ) were improved as low as 0.006 μg 100 g^-1 and 0.02 μg 100 g^-1 respectively. The effect of sample extraction and enrichment, chromatography separation parameters on the analyte, were studied in detail and optimized. Under these conditions, the method performed a good linear analytical range of 0.3-50 μg L^-1, and a good repeatability with % RSD below 2.8% and recovery of 90.2-96.5% (n = 6). To the best of our knowledge, for the first time, 60 mm high-sensitivity LightPipe flow cell was included in the HPLC-DAD method for determination of the trace amount of vitamin B12 in infant food. The proposed method was further validated by analysis of FAPAS QC samples (T21120 and T21118), and it was specific and precise for the intended use.

Development of Stable Isotope Dilution Assays for the Analysis of Natural Forms of Vitamin B12 in Meat

The first multiple stable isotope dilution assay method was developed for the simultaneous determination of four cobalamins, namely, hydroxocobalamin (OHCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), and cyanocobalamin (CNCbl), in their native forms. The sample preparation was optimized with enzyme treatment and immunoaffinity purification. The analysis was performed by LC-MS/MS using respective ¹⁵N-labeled cobalamins as internal standards. Method validation resulted in limits of detection ranging from 0.19 to 0.58 ng/g and limits of quantification ranging from 0.68 to 1.73 ng/g. Recoveries at three levels were between 82 and 121%. Intra-day and inter-day precisions were below 6% and 11% RSD, respectively. The analysis of a reference material resulted in a variance of <1% from the certified value. The newly developed method demonstrated excellent sensitivity, recovery, accuracy, and reproducibility and was further applied to quantitate the four cobalamins in various meats.

Production of Four 15N-Labelled Cobalamins via Biosynthesis Using Propionibacterium freudenreichii

Cobalamins (vitamin B12) are required by humans for their essential roles as enzyme cofactors in diverse metabolic processes. The four most common cobalamin vitamers are hydroxocobalamin (OHCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), and cyanocobalamin (CNCbl). Humans are not able to synthesise cobalamins de novo and thus must acquire them from external sources. Therefore, a reliable and robust analytical method to determine the cobalamins in dietary sources is highly required. For such a purpose, stable isotope dilution assays (SIDAs) with LC-MS/MS are most suited due to their superior sensitivity, specificity, and ability to compensate for matrix effects and analyte loss during sample work-up. However, a critical bottleneck for developing a SIDA method for cobalamins is the availability of stable isotope-labelled internal standards. In the present study, we harnessed the potential of Propionibacterium (P.) freudenreichii for the biosynthesis of ¹⁵N-labelled cobalamins. First, we developed a chemically defined medium (CDM) containing ammonium sulphate as a single nitrogen source except three essential vitamins that supported long-term stable growth of P. freudenreichii throughout continuous transfers. The CDM was further optimised for cobalamin production under different incubation schemes. With the optimised CDM and incubation scheme, fully ¹⁵N-labelled cobalamins were obtained in P. freudenreichii with a final yield of 312 ± 29 μg/L and 635 ± 102 μg/L, respectively, for [¹⁵N]-OHCbl and [¹⁵N]-AdoCbl. Additionally, an optimised incubation process under anaerobic conditions was successfully employed to produce specifically labelled [¹⁵N, ¹⁴N₂]-cobalamins, with a yield of 96 ± 18 μg/L and 990 ± 210 μg/L, respectively, for [¹⁵N, ¹⁴N₂]-OHCbl and [¹⁵N, ¹⁴N₂]-AdoCbl. The labelled substances were isolated and purified by solid phase extraction and semi-preparative HPLC. Chemical modifications were carried out to produce [¹⁵N]-CNCbl and [¹⁵N]-MeCbl. Eventually, ¹⁵N-labelled compounds were obtained for the four cobalamin vitamers in high chromatographic and isotopic purity with desired ¹⁵N-enrichment and labelling patterns, which are perfectly suited for future use in SIDAs or other applications that require isotopologues.

Development of Pretreatment Method for Analysis of Vitamin B12 in Cereal Infant Formula using Immunoaffinity Chromatography and High-Performance Liquid Chromatography

Vitamin B₁₂ deficiency may lead to serious health issues in both infants and adults. A simple analytical method involving sample pretreatment with enzyme, followed by cyanide addition under acidic conditions; separation on an immunoaffinity column; and high-performance liquid chromatography (HPLC) was developed for the rapid detection and quantitation of vitamin B₁₂ in powdered milk. Detection limit and powdered milk recovery were determined by quantitative analysis. The limits of detection and quantitation were 2.71 and 8.21 μg/L, respectively. Relative standard deviations of the intra-day and inter-day precisions varied in the ranges of 0.98%–5.31% and 2.16%–3.90%, respectively. Recovery of the analysis varied in the range of 83.41%–106.57%, suggesting that the values were acceptable. Additionally, vitamin B₁₂ content and recovery in SRM 1849a were 54.10 μg/kg and 112.24%, respectively. Our results suggested that the analytical method, including the sample pretreatment step, was valid. This analytical method can be implemented in many laboratory-scale experiments that seek to save time and labor. Therefore, this study shows that immunoaffinity–HPLC/ultraviolet is an acceptable technique for constructing a reliable database on vitamin B₁₂ in powdered milk containing starch as well as protein and/or fat in high amounts.

Systemic risk factors correlated with hyperhomocysteinemia for specific MTHFR C677T genotypes and sex in the Chinese population

Background

Methyltetrahydrofolate reductase (MTHFR) is a main regulatory enzyme in homocysteine (Hcy) metabolism. A common C677T mutation in the MTHFR gene results in decreased enzyme activity, which contributes to hyperhomocysteinemia (HHcy). Previous studies have shown that HHcy was correlated with various systemic diseases, such as cardiovascular disease, stroke, cancer, renal failure and so on. However, we hypothesized that HHcy in different genotype and sex groups may have different risk factors, which would lead to various pathologic states. Therefore, the aim of this study was to explore systemic information that are correlated with HHcy for specific MTHFR C677T genotypes and sex, which might be useful for predicting and preventing systemic diseases.

Methods

This cross-sectional study was performed through November 2017 to July 2019. A total of 4,534 adults aged 20–75 y were selected for this study. All the participants underwent a physical examination, blood tests and MTHFRC677T genotyping. Multivariable linear regression was performed to explore the risk factors for HHcy for each sex and genotype.

Results

The average of Hcy level is higher in the TT genotype than CC and CT genotypes (P=0.000). Multiple linear regression analysis identified the common protective factors (folate and Vit B12) and risk factor (Cr) for HHcy. Besides that, each group has its specific risk factors—female-CT (age, SBP, and Hb), female-TT (SBP and AST); male-CC (age, AST and Hb), male-CT (age and AST) and male-TT (SBP, AST, and Hb).

Conclusions

HHcy was associated with different risk factors for each specific sex and genotype. These risk factors might be useful for predicting and preventing systemic diseases.

Short communication: Influence of intramuscular injection of vitamin B12 in early-lactation dairy cows on Mozzarella cheese quality and vitamin B12 stability

The current study explored the effect of intramuscular injection of vitamin B₁₂ (VB₁₂) in early-lactation dairy cows on subsequent low-moisture part-skim Mozzarella cheese quality and VB₁₂ levels during cheese processing and storage. Twenty-four peripartum dairy cows were blocked based on parity and milk yield and randomly assigned into 2 treatments: basal diet (CON) and basal diet with an intramuscular injection of 10 mg of VB₁₂ per cow per week (VB₁₂). Raw milk was collected to determine VB₁₂ content and then used to make low-moisture part-skim Mozzarella cheese 8 wk after injection. The VB₁₂ content of raw milk and cheese was determined using ultra-performance liquid chromatography coupled with tandem mass spectrometry. We found that VB₁₂ content was significantly increased in milk (15.43 vs. 3.30 ng/mL) and fresh cheese (3.72 ng/g vs. undetectable) from the VB₁₂ group compared with the CON group. However, approximately 70% of VB₁₂ was lost in the whey during cheese making, and no VB₁₂ was detectable in either cheese treatment after 8 wk of storage. Furthermore, no significant differences were observed in fat and protein contents in the cheese between the 2 groups. For cheese color, the b* value increased and the a* value decreased slightly in fresh VB₁₂ cheese. Functional properties of stretchability, flowability, and meltability of VB₁₂ cheese were initially comparable to that of CON cheese, but higher flowability and meltability was observed in VB₁₂ cheese after 8 wk of storage. In summary, intramuscular injection of VB₁₂ in early-lactation dairy cows increases the content of VB₁₂ in milk and fresh cheese with no adverse effect on cheese quality, but substantial VB₁₂ is lost during cheesemaking and declines rapidly during storage.

Determination of vitamin B12 in four edible insect species by immunoaffinity and ultra-high performance liquid chromatography

Insects are rich in major nutrients, such as protein and fat. Recently, minor nutrients like vitamins have become the subjects of interest in insects. Hence, this study reports on the development and validation of a method for the determination of vitamin B₁₂ in mealworm (Tenebrio molitor larvae), cricket (Gryllus assimilis), grasshopper (Locusta migratoria) and cockroach (Shelfordella lateralis), using an ultra-high performance liquid chromatography approach with preliminary immunoaffinity chromatography sample preparation. The method was validated regarding linearity, specificity, accuracy and precision, as well as limits of detection/quantification, and was found to be satisfactory for the desired application. Found levels of vitamin B₁₂ were 1.08 µg/100 g for mealworm, 2.88 µg/100 g for cricket, 0.84 µg/100 g for grasshopper, and 13.2 µg/100 g dry weight for cockroach, representing the first validated report on the content of vitamin B₁₂ in edible insects. Observed interferences are likely caused by the presence of pseudovitamin B₁₂.

Novel protein-lipid composite nanoparticles with an inner aqueous compartment as delivery systems of hydrophilic nutraceutical compounds

Food protein and lipid based nanoparticles have attracted recent interest as a means of delivering nutraceuticals. Nanoparticle encapsulation of nutraceuticals faces challenges to overcome for it to be readily applied in the food industry, such as low encapsulation efficiency for hydrophilic compounds and poor stability once in the gastrointestinal tract. This research introduces a new protein-lipid composite nanoparticle with a three-layered structure (a barley protein layer, α-tocopherol layer and phospholipid layer) and an inner aqueous compartment to load hydrophilic nutraceuticals. This delivery system showed efficient encapsulation of vitamin B12 (69%) and controlled release behavior in simulated gastrointestinal media. An in vitro cell evaluation demonstrated that nanoparticles could internalize into Caco-2 cells via energy-dependent endocytosis and significantly increase the uptake and transport efficiency of vitamin B12 in this model. In vivo, the developed vitamin B12 loaded nanoparticle showed increased serum vitamin B12 levels upon oral administration and reduced the methylmalonic acid level more efficiently than the free form in rats. A 14-day in vivo toxicity study showed no evidence of toxicity in rats implying the safety of the developed nanoparticles in long term use. Overall, the results of this study show the great potential of the developed nanoparticles in increasing the absorption of vitamin B12 upon oral administration.

Vitamin B12 determination in milk, whey and different by-products of ricotta cheese production by ultra performance liquid chromatography coupled with tandem mass spectrometry

Vitamin B12 (cobalamin) is a metal complex composed of a central cobalt ion bonded to six ligands. It is essential for major biological functions such as protein, fat and carbohydrate metabolism, the maintenance of the central nervous system, and the formation of red blood cells. Since mammals cannot synthesize cobalamin, dietary intake represents the only natural source for humans. Dairy products can provide significant levels of cobalamin; moreover, the European Food Safety Authority (EFSA) panel has set the recommended intake at 4 μg/day for adults. Vitamin B12 content was determined in milk and several matrices related to the process of transformation of the residual whey from Parmigiano Reggiano cheese-making to obtain ricotta cheese. In addition, vitamin B12 degradation during ricotta cheese shelf-life was studied. The analyses were performed using an ultra performance liquid chromatography-tandem mass spectrometry method. Results show that vitamin B12 amount in ricotta from dairy and experimental cheese-making brings respectively 1/8 to 1/4 of the adequate intake in adults established by EFSA. In addition, shelf-life experiment shows that cobalamine is fairly rapidly degraded in ricotta: light effect seems to be significant, even if the light exposure is short. The use of photoprotective packaging material increases B12 shelf-life in the early stage of storage.

Determination of Vitamin B12 in Dairy Products by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

Vitamin B₁₂ is a water-soluble molecule composed of a tetrapyrrolic complex with a cobalt atom at its centre. It is an essential regulatory element, synthesized only by bacteria; for this reason it is present only in food of animal origin and the daily requirement for humans is about 1 to 2 mg. Since milk and dairy products provide a significant dietary cobalamin intake, an ultra performance liquid chromatographytandem mass spectrometry method was applied to samples collected at different stages along the process of cheese making in order to evaluate the distribution of this molecule. In particular, samples of milk, rennet, whey, ricotta cheese, curd, mozzarella cheese and caciotta cheese were analysed. Results showed a level of vitamin B₁₂ about 10 times higher in whey and ricotta cheese with respect to the milk they are derived from. These data would confirm the tendency of cobalamine to concentrate in the proteic fractions along the cheese production process.