L. F. CASTRO (1), C. F. Ross (1); (1) Washington State University, Pullman, WA, U.S.A.
Sensory II
Thursday, June 5 - 10:00 a.m.-11:45 a.m.
Lobby Level, Empire Ballroom
Model beer solutions with varying levels of carbohydrate and protein and
known levels of four volatile compounds (isoamyl acetate [banana],
ethyl hexanoate [apple], myrcene [dry-hop], and benzaldehyde [almond])
were prepared to study the effect of the non-volatile fraction on
volatile compound release and sensory perception. Aroma and flavor
attributes were evaluated using a trained sensory panel, while the
concentrations of volatile compounds were determined by 1) solid-phase
microextraction (SPME); 2) solid-phase dynamic extraction (SPDE) coupled
to gas chromatography-mass spectrometry (GC-MS); and 3) stir bar
sorptive extraction (SBSE) coupled to gas chromatography-flame
ionization (GC-FID). In addition, sensory and instrumental results were
modeled by principal component analysis (PCA), and relationships between
the instrumental (volatile) and sensory variables were analyzed by
partial least squares regression (PLSR). Results showed that the
non-volatile fraction had a significant effect (P <
0.05) on volatile compound release and aroma perception. Model beer
samples with low levels of proteins and high levels of carbohydrates
presented the highest concentrations of isoamyl acetate, benzaldehyde,
and ethyl hexanoate. Myrcene was only influenced by carbohydrate
content, with a higher concentration at a lower level of carbohydrates.
Apple and banana aroma attributes were perceived as less intense at low
protein content (P < 0.05). Dry-hop aroma flavor were perceived as more intense in samples with low carbohydrate content (P <
0.05). PCA showed that differentiation between samples was mainly due
to protein content, and PLSR analysis indicated a very poor correlation
between the sensory and instrumental data. The results illustrate that
sensory perception and volatile fraction behaviors are influenced by
non-volatile components and also demonstrate the need for caution when
directly relating instrumental to sensory analyses.
Luis Castro is a post-doctoral research associate at Washington State
University. He received his B.S. degree in chemistry from the
University of Costa Rica in San José. After two years spent working in
both industry and academia, he moved to Washington State University,
School of Food Science, to pursue graduate studies. After obtaining his
M.S. degree in food science under Barbara Rasco, working in the field of
food safety, he enrolled in the Ph.D. program at the same institution,
working with Carolyn Ross. Under her supervision he started research on
beer flavor chemistry and received his Ph.D. degree in December 2013.
His current research combines sensory analysis and analytical chemistry
techniques to determine the impact of flavor and matrix components on
the sensory and chemical properties of beer.
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