A mixed mushroom control material to facilitate inter-laboratory harmonization of mushroom composition analyses

Quantitation of total vitamin D2 and D4 in UV-exposed mushrooms using HPLC with UV detection after novel two-step solid phase extraction

A robust method for quantitation of total vitamin D2 and D4 in mushrooms by high performance liquid chromatography with UV detection (HPLC-UV) was developed to analyze mushrooms exposed to UV light. A two-step solid phase extraction (SPE) (silica, carbon black) removed chromatographic interferences typically resolved only with mass spectrometric detection (LC-MS) and allowed quantitation of all vitamin D and pre-D analytes. The vitamin and pre-vitamin forms of D2, D4 and D3 (internal standard), as well as other photoisomers and sterols were resolved. Results for six types of UV-exposed mushrooms were comparable to LC-MS. Screening of ten additional types of UV-exposed mushrooms without the IS confirmed lack of interference with the IS. The limit of quantification (µg/100 g fresh weight) was 0.4 for vitamin D and 0.9 for pre-vitamin D. Mushrooms do not have to be dried, and separatory funnels and large solvent volumes were also eliminated from sample preparation.

Characterization of various isomeric photoproducts of ergosterol and vitamin D2 generated by UV irradiation

Vitamin D2 is produced from its precursor ergosterol under the impact of ultraviolet (UV) light which is also commercially carried out to increase vitamin D2 contents in mushrooms (‘Novel Food’). However, this process is accompanied by the formation of various isomers that partly co-elute with the target compound and are currently difficult to analyze. For this reason, vitamin D2 and ergosterol were irradiated with the goal to generate and characterize various isomeric photoproducts with three analytical methods. High-performance liquid chromatography with ultraviolet detection (HPLC–UV) was accompanied by using a chiral detector (CD) which was serially linked with the UV detector. Applied for the first time in this research area, HPLC-CD chromatograms provided complementary information which was crucial for the identification of several co-elutions that would have been overlooked without this approach. Additional information was derived from gas chromatography with mass spectrometry analysis. Diagnostic fragment ions in the GC/MS spectra allowed to distinguish four classes of tri- (n = 2), tetra-, and pentacyclic isomer groups. Despite several drawbacks of each of the applied methods, the shared evaluation allowed to characterize more than ten isomeric photoproducts of vitamin D2 including previtamin D2, lumisterol2, tachysterol2,trans-vitamin D2 isomers, and two pentacyclic isomers (suprasterols2 I and II), which were isolated and characterized by proton magnetic resonance spectroscopy (1H NMR).

Large Variability of Iodine Content in Retail Cow's Milk in the U.S

Iodine intake is of contemporary public health interest. The recommended daily iodine intake is 150 µg for most adults, and milk is an important source of iodine in the U.S. diet. Iodine concentration in cow's milk is affected by diet and iodine supplementation levels, milking sanitation practices, and other factors. Current analytical iodine data in U.S. retail milk are crucial for evaluating population-wide health outcomes related to diet. Samples of whole (3.25% fat), 2%, 1%, and skim (0-0.5% fat) milk were procured from 24 supermarkets across the U.S. using a census-based statistical plan. Iodine was analyzed by inductively coupled plasma mass spectrometry, including certified reference materials and control samples to validate results. No difference in iodine content was found between milkfat levels (F3,69 1.033, p = 0.4). Overall mean (SEM) was 85(5.5) µg/serving (240 mL). However, the 95% prediction interval of 39-185 µg/serving for individual samples indicated high variability among individual samples. Given the recommended 150 µg iodine per day for most adults along with the study mean, one milk serving can provide approximately 57% of daily intake. Researchers, health care professionals, and consumers should be aware of iodine variability in milk, while additional research is needed to investigate the impact of iodine variability factors.

Seasonal variability of the vitamin C content of fresh fruits and vegetables in a local retail market

BACKGROUND

Seasonal variation of vitamin C in fresh fruits and vegetables is not reflected in food composition database average values, yet many factors influence content and retention.

RESULTS

Fresh fruits and vegetables were sampled on three occasions in each season, from the same local retail outlets, for 1 or 2 years. Vitamin C was significantly higher in winter-sampled spinach (436 mg kg^-1 ) compared with spring (298 mg kg^-1 ) and summer/fall (180 mg kg^-1 ); in potatoes in summer/fall (156 mg kg^-1 ) versus winter/spring (106 mg kg^-1 ); and in oranges in winter (616 mg kg^-1 ), spring (592 mg kg^-1 ), and summer (506 mg kg^-1 ). Ranges were dramatic among sampling occasions for broccoli, oranges, potatoes, and spinach (700-1210 mg kg^-1 , 420-780 mg kg^-1 , 70-280 mg kg^-1 , and 90-660 mg kg^-1 respectively). Mean values for apples, bananas, tomatoes, and potatoes differed from the USDA National Nutrient Database for Standard Reference (SR) average by ≥10% of the daily recommended intake (90 mg). For broccoli, oranges, and spinach, vitamin C was substantially above or below the SR range in 50-100% of the samples. For spinach, the average content did not differ from SR, but vitamin C in winter was 55% higher than SR.

CONCLUSION

Database average values for vitamin C in fresh produce can significantly over- or underestimate the content in a specific food supply. © 2018 Society of Chemical Industry.

Impact on Vitamin D2, Vitamin D4 and Agaritine in Agaricus bisporus Mushrooms after Artificial and Natural Solar UV Light Exposure

Commercial mushroom production can expose mushrooms post-harvest to UV light for purposes of vitamin D2 enrichment by converting the naturally occurring provitamin D2 (ergosterol). The objectives of the present study were to artificially simulate solar UV-B doses occurring naturally in Central Europe and to investigate vitamin D2 and vitamin D4 production in sliced Agaricus bisporus (button mushrooms) and to analyse and compare the agaritine content of naturally and artificially UV-irradiated mushrooms. Agaritine was measured for safety aspects even though there is no rationale for a link between UV light exposure and agaritine content. The artificial UV-B dose of 0.53 J/cm(2) raised the vitamin D2 content to significantly (P < 0.001) higher levels of 67.1 ± 9.9 μg/g dry weight (DW) than sun exposure (3.9 ± 0.8 μg/g dry DW). We observed a positive correlation between vitamin D4 and vitamin D2 production (r(2) = 0.96, P < 0.001) after artificial UV irradiation, with vitamin D4 levels ranging from 0 to 20.9 μg/g DW. The agaritine content varied widely but remained within normal ranges in all samples. Irrespective of the irradiation source, agaritine dropped dramatically in conjunction with all UV-B doses both artificial and natural solar, probably due to its known instability. The biological action of vitamin D from UV-exposed mushrooms reflects the activity of these two major vitamin D analogues (D2, D4). Vitamin D4 should be analysed and agaritine disregarded in future studies of UV-exposed mushrooms.

Method Development for the Determination of Free and Esterified Sterols in Button Mushrooms (Agaricus bisporus)

Ergosterol is the major sterol in button mushrooms (Agaricus bisporus) and can occur as free alcohol or esterified with fatty acids (ergosteryl esters). In this study, gas chromatography with mass spectrometry in the selected ion monitoring mode (GC/MS-SIM) was used to determine ergosterol and ergosteryl esters as well as other sterols and steryl esters in button mushrooms. Different quality control measures were established and sample preparation procedures were compared to prevent the formation of artifacts and the degradation of ergosteryl esters. The final method was then used for the determination of ergosterol (443 ± 44 mg/100 g dry matter (d.m.)) and esterified ergosterol (12 ± 6 mg/100 g d.m.) in button mushroom samples (n = 4). While the free sterol fraction was vastly dominated by ergosterol (∼90% of five sterols in total), the steryl ester fraction was more diversified (nine sterols in total, ergosterol ∼55%) and consisted primarily of linoleic acid esters.