If you missed us at AOAC in Denver, CO, links to our oral and poster presentations are available below.

Oral Presentation

Title:  Yes, Solid Phase Microextraction is Quantitative – A Walk-Through Development

Date:  Tuesday, September 10, 2019

Time:  1:00 pm – 1:30 pm

Location:  Governor’s Square 10 Room

Abstract:  Solid phase microextraction (SPME) is a simple, fast, inexpensive and easy-to-automate sample preparation technique. There is some misconception that this technique is only useful for qualitative work, however SPME can be used effectively for quantitative applications. Accurate quantitative methods can be developed using SPME if a few basic principles are applied. In this seminar, we will cover the activities involved in developing and validating a quantitative SPME method - specifically for determining alcohol content in Kombucha tea. This method was recently moved to first action official method status by the AOAC.

Poster Presentations

All posters will be in the Plaza A-E Hall and Plaza Foyer of the Sheraton Denver Downtown Hotel.

Evaluation of a Surrogate Matrix for Whey Protein Quantitation in Infant Formula by LC-MS

On Display: Monday, September 10, 2019, 10:00 am – 5:00 pm
Author Presents:  12:00 pm – 1:00 pm

Authors: Derrell Johnson, Judy Cao, Uma Sreenivasan, and Kevin Ray
Poster Board Number: P-M-083

Infant formula, an alternative to breast milk, provides nutrition for the growth of babies. For example, α-lactalbumin (LA), a predominant whey protein in infant formula, plays important roles in several biological processes including lactose biosynthesis and immune system regulation. On the other hand, another whey protein, β-lactoglobulin (LG), present in bovine milk but absent in human milk, has been reported as one of the allergens in infant formula. Therefore, it is essential to develop quality control methods for the quantitation of LA and LG in infant formulas. Among various techniques which have been developed for the analysis of whey proteins, liquid chromatography-mass spectrometry (LC-MS) is becoming more widely adopted. However, one of the challenges is the selection of surrogate matrix for the preparation of calibration standards. In this poster, we will present our approach to determine the suitability of a surrogate matrix for the quantitation of LA and LG in infant formula by LC-MS.

Measuring Ethanol in Kombucha Tea by Headspace Solid Phase Microextraction (HS-SPME); a Walk-Through Method Development and Validation

On Display: Tuesday, September 11, 2019, 10:00 am – 5:00 pm
Author Presents:  12:00 pm – 1:00 pm

Authors: Katherine K. Stenerson, Olga I. Shimelis, and Teresa Marsala
Poster Board Number: P-T-093

Kombucha tea has been gaining in popularity throughout the United States and Europe. The fermentation process used in its production results in a tangy, sometimes fizzy drink that is rich in probiotics. Yeast present in the Kombucha consumes sugars which in turn produces alcohol. In the United States, if the alcohol level is > 0.5%, it is considered an alcoholic beverage and is thus subject to appropriate laws and regulations. Kombucha manufacturers are held responsible for the ethanol level in their products and are encouraged to have testing done using a reliable method. Since Kombucha can contain a variety of flavorings and additives, the method must be accurate with the presence of a variety of matrix components. Recently, AOAC adopted as first action a headspace solid phase microextraction (HS-SPME) method for analysis of ethanol in Kombucha. This method was developed and validated using a variety of Kombucha tea products. Analysis was done by GC-MS which allowed use of isotopically labeled ethanol as an internal standard, thus ensuring a high level of accuracy. The data presented will summarize the steps done to develop the SPME method, as well as the results of the single-lab validation study. In addition, the method was also adapted to the testing of wine samples. Using the appropriate dilution, it was found to be applicable to this matrix as well.

The Measurement of the Effects of Container Materials on Production of Light Induced Off-Flavors in Milk Using Solid Phase Microextraction (SPME) Gas Chromatography-Mass Spectroscopy

On Display: Wednesday, September 12, 2019, 10:00 am – 5:00 pm
Author Presents:
  12:00 pm – 1:00 pm

Robert Shirey, Katherine K Stenerson, and Stacy Shollenberger
Poster Board Number: P-W-024

It has been well documented that when milk is exposed to UV light, off-flavorings are produced. Ultra-violet (UV) light causes a free radical reaction with unsaturated fatty acids, primarily linoleic acid, forming hydroperoxides that readily oxidize mostly to pentanal and hexanal. Because of their low sensory threshold, these malodors are readily detected in milk products. Other UV induced malodors are sulfides formed from the degradation of sulfur-containing amino acids. Dimethyldisulfide and dimethyl sulfide are the primary products of this reaction. The presence of these products was readily observed with the transition from glass to plastic milk storage containers. In this study, milk was place in similar sized containers made from both glass and a variety of plastic materials. The containers were then exposed to fluorescent lighting for a fixed time. The flavors and off-flavors in the exposed milk were extracted using headspace SPME with a Carboxen®-PDMS coated Nitinol fiber followed by analysis using GC-MS. This fiber coating retains low molecular weight analytes, and allowed detection in the samples at concentration levels less than 1 ng/mL (ppb). The major flavoring contaminants were quantified in milk samples stored in the various containers. This presentation will show the differences between storage containers and the effectiveness of SPME to identify and quantify the off-flavors formed in the milk samples.