39B-13

C. H. BRENES¹, L. R. Howard, and S. T. Talcott. (1) Institute of Food Science and Engineering, University of Arkansas, 272 Young Ave, Fayetteville, AR 72704

Maillard derived pyrazines are formed during frying of potato chips. Separation of these often bitter, semi-volatile compounds from fatty matrices is difficult, therefore development of a rapid method for their concentration and quantification is needed to understand and control flavor characteristics of fried foods.

To develop an extraction protocol to concentrate and analyze pyrazine compounds from potato chips using SPME-GC-MS and to identify pyrazines produced from the predominant amino acids found in potatoes.

Potato slices were leached of soluble solids by water (60°C), 80% ethanol (45°C) and then vacuum infiltrated with solutions of glucose, fructose, asparagine and glutamine at levels commonly found in potatoes. Slices were then fried in oil to produce chips. Infiltration concentration of each compound was quantified by HPLC. Pyrazine isolates were concentrated from acidified chip slurries (pH 4) by vacuum distillation. Distillates were adjusted to pH 12 and extracted using a 100-µm PDMS fiber. Identification of compounds was based on retention indices, mass spectra and external standards with data expressed as 2,3-diethyl pyrazine equivalents.

Numerous alkylpyrazines were detected in potato chip models ranging in concentration from 7 to 542 ppb, with 2-ethyl-5-methyl pyrazine, 2,5-diethyl pyrazine and 2,5 dimethyl-3-ethyl pyrazine the predominant compounds present. Distillation recovery (96%) was calculated by spiking 2,5-dimethyl pyrazine into the potato chip slurry and quantified spectrophotometrically at 278 nm. Adsorption of pyrazines onto the SPME was 5-17% higher at pH 12 compared to pH 7. Most pyrazines were present regardless of the amino acid tested, but varied widely in concentration. Differences in pyrazine concentrations were apparently influenced by competition between amino acids for reaction with reducing sugars present in the model system.

A rapid distillation method to concentrate and analyze pyrazines formed in potato chip models was developed. The procedure is beneficial as a quality control tool with specific applications to foods high in lipid content.