30B-25 |
Modeling changes in amides and reducing sugars during long-term storage of potato tubers and evaluation of their impact on potato chip pyrazines |
C. H. BRENES, Department of Food Technology/Biotechnology Research Center, ITESM-Campus Monterrey, 1209 San Dario Ave PMB 7-340, Laredo, TX 78040, L. R. Howard, Institute of Food Science and Engineering, University of Arkansas, 272 Young Ave, Fayetteville, AR 72704, and S. T. Talcott, Institute of Food and Agricultural Sciences, University of Florida, 459-C FSHN, P.O. Box 110370, Gainesville, FL 32611-0370. In raw potatoes, free amino acids (FAA) are in excess compared to reducing sugars (RS), and levels generally increase during long-term storage. Because of this abundance of FAA, RS are considered the limiting factor for Maillard browning in potatoes and the primary index for fried product quality. Acceptable levels of RS are usually based on final potato chip color, and have not considered variability in flavor characteristics at different FAA levels. This project evaluated the impact of increasing concentrations of FAA (asparagine and glutamine) and RS on the formation of specific pyrazine compounds during potato chip frying. Sliced potatoes were leached of soluble solids, and then vacuum infiltrated with increasing concentrations of amides (0-1.5% FW) and RS (0-0.32% FW), simulating metabolic changes in raw potatoes during long-term storage; then fried in oil to produce chips. Pyrazines were concentrated from chip slurries (pH 4) by vacuum distillation, adjusted to pH 12, and adsorbed onto a 100-mm PDMS, SPME fiber. Identification of compounds was based on retention indices, mass spectra, and comparison to external standards. Increasing RS concentrations enhanced pyrazine yield, confirming their importance to potato chip flavor, but increasing FAA affected pyrazine yield differently. Of special interest was the observed trend for eight pyrazines, which included the most abundant found in chips (2-ethyl-3-methyl-, 2,5-dimethyl-3-ethyl and 3,5-diethyl-2-methyl pyrazines). For this group of compounds, concentrations were not significantly affected by increasing FAA content at low RS levels (<0.08% FW), but at higher RS levels (0.16 and 0.32% FW) their yield increased with increasing FAA levels; a synergistic effect that could have a negative effect on flavor. Our results indicate that undesirable bitter/burnt flavors, derived from pyrazines, could be generated below the RS levels commonly used as the lower limit for the prevention of color defects in potato chips when FAA are present in sufficiently high concentrations.
Session 30B, Fruit & Vegetable Products: Sensory, Product Development, Fresh-Cut, and Storage
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