Aromas- lec 1 Flashcards
what other units are equal to 1 ppm?
1mg/kg
1 microgram/g
what compound is responsible for the aroma of coffee? what is its threshold?
furfurylthiol
-5pp trillion
What is the role of volatile compounds in aroma perception? what are the 2 pathways? what detects the aroma?
Volatile compounds interact with olfactory receptors, detected through orthonasal and retronasal pathways.
Define aroma thresholds.
The lowest concentration at which an aroma compound is detectable.
what is the difference between flavour and aroma? what are the characteristics of the compounds responsible for this?
Flavour compounds: non-volatile, interact with taste receptors on tounge
Aroma: volatile, percieved by odour receptors (olfactory tissue) in nasal cavity
-orthonasal (nose)
-retronasal (throat after chewing)
How do odor thresholds vary in different media? what is the reason for these differences?
Air: Lower threshold
Water: Higher threshold
Fat-Based Matrices: Lipophilic compounds dissolve more readily
-change of threshold between different mediums has to do with the polarity of the substance to the medium. Substances that have a higher attraction to the medium will be less volatile
-> higher threshold
What compound gives of “woody, spicy”? what about “grapefruit”?
(-)-Nootkatone and (+)-Nootkatone
What causes aroma defects and off-flavors?
- Lipid oxidation
- Microbial metabolism
- Chemical reactions
*Food processing
*Environmental pollution
What is Gas Chromatography-Olfactometry (GC-O)?
A technique that separates volatile compounds, sniffed by trained panelists to identify key aroma components.
How does stereochemistry affect aroma perception?
Different stereoisomers can have distinct aroma properties.
what 4 rxns lead to the generation of carbonyl volatiles?
1) lipid peroxidation
2) caramelization
3) AA decomposition
-strecker/maillard rxn
4) degradation of carotenoids
What is the Maillard Reaction? what are important derivatives?
A chemical reaction that generates roasted and caramel-like aromas
-generates dicarbonyl compounds which can then produce maltol and isomaltol (important flavour and aroma compounds)
What is the significance of the strecker rxn? what compounds are involved? what is produced?
rxn between a dicarbonyl compound and an amino acid; forms aldehydes, CO2, ketones and volatile compounds
involved in heavily in flavour and aroma formation
Where is maltol found in food?
coffee, chocolate, beer (dependent on amount)
what aroma does furaneol give rise to?
strawberry
-coffe in other amounts
How does pH impact threshold?
Structure and pH play an important role in the threshold level, with the threshold changing with a change in pH
How does the aroma of fresh fish change over time? what is the best measure of the freshness?
The compounds responsible for fresh fish are:
-TMAO
-Aldehydes
-unsaturated alcohols + esters
-The composition of DHA/EPA impact the aroma profile
As fish degrades TMA-O is broken down into TMA and DMA (indicators of freshness)
What do you expect of TMA-O, TMA, sensory evaluation and T-volatile base (TVB) levels over time?
TMA-O: decreases
TMA: increases
sensory evaluation: decreases
TVB: increases
How does molecular mass and saturation impact volatile threshold?
1) Threshold increases when molecular mass increases
2) cis-isomer (more volatile) tend to have lower threshold than trans-isomers
3) unsaturation (more db) lowers threshold- higher threshold w saturated compounds
what type of compound is typically generated in fruits that give it its aroma?
esters
what type of aroma compounds are common in meat?
hetero cyclic
