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Application of ultra high hydrostatic pressure for investigating the binding of flavor compounds to ß-lactoglobulin via headspace solid phase microextraction-gas chromatography

by 1977- Hoang, Tinyee Arden, PhD


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P

between the mean peak area and the concentration of analyte in the buffer was
determined by linear regression. The procedure revealed linear behavior over the whole
concentration range tested with correlation coefficients RP

2

> 0.954 for selected flavor
compounds (Figure 3). The calculated KI for diacetyl, 2-methylbutyraldehyde, ethyl
lactate, and δ-decalactone are presented in Table 1.
CONCLUSIONS
The SPME adsorption-GC detection method developed is a convenient
quantitative analytical technique for diacetyl, ethyl lactate, 2-methylbutyraldehyde, and
δ-decalactone in a model buffer solution. The small amount of time and materials
required for SPME concentration and extraction, and GC separation and detection
resulted in an inexpensive and simple method for analysis. The combination of extraction
and concentration into one SPME adsorption step significantly decreased the time
required for analysis. SPME adsorption-GC detection method described required 1.7 h
for both extraction and detection of selected flavor compounds. The selectivity of the
SPME method versus more common methods such as liquid-liquid extraction, excludes
necessary clean-up procedures which may introduce errors and extend the time necessary
for an efficient and sensitive analytical method.

(Diaz and others 2004)

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CHAPTER FOUR
Application of solid-phase microextraction with headspace gas chromatography to
the analysis of diacetyl, 2-methylbutyraldehyde, ethyl lactate, and
δ-decalactone in ultra high pressure-treated
β-lactoglobulin solutions

1 1 2 1

Tinyee HoangP P, Joseph R. PowersP P, John K. FellmanP P, and Barry SwansonP

P

(1) Dept. of Food Science & Human Nutrition, (2) Dept. of Horticulture & Landscape
Architecture, and (3) Dept. of Chemistry Washington State Univ., PO Box 646376,
Pullman, WA 99164-6376

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ABSTRACT

The effects of ultra high pressure (UHP) treatment on the flavor-binding
properties of β-lactoglobulin (BLG) were determined with selected flavor compounds
diacetyl, ethyl lactate, 2-methylbutyraldehyde, and δ-decalactone. Following UHP
treatment (600 MPa, for 0, 8, 32 min) of BLG, intrinsic tryptophan fluorescence
quenching, static headspace solid-phase microextraction (HS-SPME) and GC analysis
were used to study the flavor binding properties of BLG. Fluorescence quenching data
indicated an increase in the fractional number of binding sites of BLG for diacetyl, δ-
decalactone, and ethyl lactate with high dissociation constant values. As observed by HS-
SPME GC, native BLG retained approximately 50% of the concentration of the selected
flavor compounds added to BLG solutions. UHP treatments of BLG resulted in
significant increases (p < 0.005) in the flavor retention of the selected flavor compounds,
with the greatest retention for diacetyl following UHP of 32 min.

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INTRODUCTION
Volatile constituents in food are contributing factors to flavor, exhibited by the
observation that elimination of our sense of smell (e.g. by a common cold), results in
many foods tasting bland. The food industry is aware of the importance of flavor as an
essential factor in food selection and acceptance. Flavor is one of the most important
attributes of a food, driving consumer acceptance.
In the process of perception, food is first assessed by appearance, and then
followed by aroma, consistency and texture, and flavor evaluation, yet these attributes
tend to overlap (Meilgaard and others 1999). Aroma is the odor perceived by the
olfactory system when volatiles enter the nasal passage, either orthonasally or
retronasally. A sufficient concentration of a flavor compound in the vapor phase (nasal)
or aqueous phase (saliva) must be achieved to elicit olfactory and taste receptor
responses. The quantity of volatiles released from a food is dependent upon the
temperature and chemical properties of the flavor compounds. Flavor is defined as the
sum of perceptions resulting from stimulation of the sensory receptors grouped together
at the entrance of the alimentary and respiratory tracts (Meilgaard and others 1999),
otherwise perceived in the mouth.
Food is a complex system in which equilibrium of flavors between the aqueous,
gaseous, and solid phases is rarely reached during preparation or eating, but physical
chemistry provides tools useful for understanding and predicting flavor behavior.
Equilibrium partitioning theory can explain the interaction of flavor compounds in the
gas phase and aqueous phase or their combinations. The partition coefficient (K) of flavor
compounds between the gas phase and the aqueous phase in a closed system is described
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