Technology is always changing and so is the food we eat and drink. With regulations becoming more strict and time becoming of the essence, the need for rapid testing measures are becoming ever more crucial. Key researchers and government bodies have taken notice to this and studies are being conducted on the out dated testing methods.
I came across two articles (see references below) and the following from Byrdwell et al. is what I feel to be important ideas from the reports.
“Historically, the measurement of vitamin D concentrations in foods has presented an enormous analytical challenge. Vitamin D is a complex, highly reactive and lipophilic molecule. Extracting vitamin D from the food materials with all the other lipid components complicates an already difficult separation process and makes detecting vitamin D by ultraviolet molecular absorption highly problematic. Consequently, saponification of the sample is necessary before a sophisticated separation process.
Today, the instrumental methods of choice for analyzing vitamin D in foods include separation by HPLC and detection by either ultraviolet absorption with diode array (DA) or mass spectrometry (MS).
In general, analysts saponify samples to hydrolyze triacylglycerols into fatty acids and glycerol, extract vitamin D2 and vitamin D3, collect both vitamin D2 and D3 as a single peak by using preparative-scale, normal phase HPLC, and separate vitamin D2 and D3 by using analytical reversed-phase chromatography with DA detection. Variability arises from the different extraction solvents (usually either hexane or petroleum ether) and internal standards used.
The methods listed have 3 major problems. First, they are time consuming and labour intensive and require extreme attention to detail. Second, researchers have only validated these methods for a limited number of materials, most notably dairy products, which have a high fat content. Third, researchers have designed and validated methods only to produce analytical values for vitamin D3. Vitamin D2 behaves similarly to vitamin D3 with respect to saponification, extraction and separation steps.
The initial results disappointed the committee. The interlaboratory RSD’s for each of the 5 control materials fell between 35% and 50%. For every control material, ≥2 laboratories reported values that differed by a factor of 2.”1
This report has reviewed the disadvantages of existing methods for analyzing the vitamin D content of foods. The authors showed that existing methods can produce accurate results, but the test is time consuming and expensive. A new method is needed to measure vitamin D in foods that is simpler and faster.
Why is it so important that these methods for vitamin A and vitamin D analysis in dairy products be updated? Even though the addition of vitamins to foods is done under strict QA/QC guidelines, there are still chances that over or under fortification can occur, whether it is due to premix levels not being accurate or the addition of premixes not being exact or some other processing error. Fortification levels are staying within the acceptable range more often now, then they were in the early 90’s, yet as observed by Holden et al.2 there are still milk products that are slipping out of this range.
“Five types of fortified milk were collected; skim, 1%, 2%, whole and 1 % chocolate. All the products should provide 25% DV of vitamin D3/ 8 oz serving. Actual vitamin content varied from zero to 47% DV, nearly double the label claim. Overall, about 77% of the products fell within or very close to the expected 100-150% of label, however, about 17% of the values were lower than 100%. The vitamin D content of milk was more variable than yogurt. Accurate, current data for vitamin D are important to the assessment of intake by the US population.”2
Researchers are finding new roles that vitamins play in our health, and making sure we get them sufficiently is just as important. Advanced technology is replacing the old in all aspects and the food industry is no different. The time for rapid, reliable and accurate analytical methods for vitamin A and vitamin D testing is here.
Comments or opinions about the above are welcome.
Robert Sikora
References:
1. Byrdwell WC, DeVries J, Exler J et al. Analyzing vitamin D in foods and supplements: methodologic challenges. Am J Clin Nutr 2008; 88, No.2:554S-557S.
2. Holden JM, Patterson KY, Exler J et al. Vitamin D3 content of fortified yogurt and milk as determined for the USDA National Food and Nutrient Analysis Program (NFNAP) FASEB J. 23: 112.8