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Using NMR to Screen Holiday Eggnog

“Even while you toast the holidays, you remain a scientist at your core.”

A quick Google search yields hundreds of recipes for eggnog and egg liqueur. Anecdotes about the history of the drink and nation of origin abound. Most, however, agree that eggnog and egg liqueur have the same fundamental ingredients — eggs, sugar and alcohol of some kind. Another universal truth: Eggnog is a social drink. While many down a cup on Christmas, some make a habit of it on New Year’s Day while visiting friends. Others, like residents across Germany, enjoy egg liqueur year round, especially at Easter.

So what is egg liqueur? According to regulations, it is a spirit drink … obtained from ethyl alcohol of agricultural origin … quality egg yolk, egg white and sugar or honey.” To ensure people get what they pay for and products meet certain standards, egg liqueurs are tested, but the methods involve time-consuming preparation and analysis. The Bavarian State Ministry of the Environment and Consumer Protection funded research into the feasibility of using 1H NMR to analyze products. The results were published in “Quantitative 1H NMR Analysis of Egg Yolk, Alcohol, and Total Sugar Content in Egg Liqueurs,” in the April 10, 2015, edition of the Journal of Agricultural and Food Chemistry.

The researchers investigated, for the first time, the possibility of using quantitative 1H NMR spectroscopy (qNMR) to analyze the ingredients in eqq liqueur. The research was conducted at the Institute of Pharmacy and Food Chemistry at the University of Würzburg in Germany and at Spectral Service in Köln, Germany.

What’s in the bottle?

To be labeled an egg liqueur, a product must adhere to strict guidelines and contain at least 150 g/L of sugar or honey, at least 70 g/L of egg yolk, and the alcoholic strength must be 15 percent or higher. Researchers analyzed 15 egg liqueurs purchased at supermarkets in Germany for alcohol level and the content of sugar and egg yolk.

First researchers ran experiments using traditional methods. Alcohol level was estimated by pycnometry after distillation. Sugar content was analyzed using redox titration. Cholesterol, a marker for egg yolk, was measured through enzymatic analysis after saponification of lipids. Then researchers tested the egg liqueur with 1H NMR spectroscopy performed on a Bruker Avance 400 spectrometer. 1H NMR analysis included two different rapid sample preparations for water-soluble and nonpolar ingredients.

Comparing results

When researchers compared the results from traditional methods with those from 1H NMR, the findings showed excellent correlations for alcoholic strength (R = 0.996, p < 0.001) and content of total sugar (R = 0.989, p < 0.001) as well as cholesterol (R = 0.995, p < 0.001), a marker for egg yolk.

In addition, 1H NMR provided information for a second marker of egg yolk, phosphatidylcholine, and for two markers of milk products, lactose and butyric actin. Products with lactose are regulated and must be properly labelled for the benefit of lactose-intolerant consumers. 1H NMR improved speed and efficiency both by simplifying preparation and by simultaneously analyzing several organic components with each spectrum providing “a fingerprint of all organic components.” 1H NMR also provided additional useful information, such as the presence of lactose.

The excellent correlation of results proved that 1H NMR could provide a more efficient method of analysis of a product’s compliance with regulations. The researchers suggest that 1H NMR be used as a screening tool. If initial results are not in compliance with regulations, further testing using traditional methods can follow. As a result of accurate, faster testing with 1H NMR, consumer protection is enhanced.

Cheers!

References

“Quantitative 1H NMR Analysis of Egg Yolk, Alcohol, and Total Sugar Content in Egg Liqueurs,” in the April 10, 2015, edition of the Journal of Agricultural and Food Chemistry. http://www.ncbi.nlm.nih.gov/pubmed/25860435

Dec. 21, 2011, TIME, A Brief History of Eggnog http://time.com/3957265/history-of-eggnog/

Editorial overview: Foodomics technologies: Foodomics: exploring safety, quality and bioactivity of foods in the 21st centuryCurrent Opinion in Food Science 2015, 4:136–138 doi:10.1016/j.cofs.2015.07.006