CFC Flavor Extraction & Isolation Techniques 3

Question 1

Microwave-assisted extraction (MAE) of flavor compounds is based primarily on which heating mechanism?

Accepted Answer

Dielectric heating of polar molecules and water within the plant matrix

Answer

Conductive heat transfer from a heated vessel wall to the sample

Answer

Infrared radiation absorbed by C–H bonds in organic molecules

Answer

Resistive heating caused by electrical current through a conductive solvent

Question 2

Ultrasound-assisted extraction (UAE) of flavor compounds improves extraction efficiency primarily through:

Accepted Answer

Acoustic cavitation that disrupts cell walls and increases mass transfer

Answer

Thermal degradation of cell membranes by ultrasonic heating

Answer

Magnetic alignment of flavor molecules toward the extraction solvent

Answer

Photochemical activation of flavor precursors by ultrasonic radiation

Question 3

Preparative HPLC is used to isolate pure flavor reference standards primarily because it offers:

Accepted Answer

High resolution separation with scalable throughput and fraction collection capability

Answer

Faster analysis than analytical HPLC without sacrificing purity

Answer

Lower solvent consumption compared to thin-layer chromatography

Answer

The ability to identify compounds without requiring a detector

Question 4

When selecting an organic solvent for extracting aroma compounds from a complex food matrix, which pair of properties is most important to evaluate first?

Accepted Answer

Selectivity for target analytes and low boiling point for easy removal

Answer

High boiling point and high viscosity to retain compounds during evaporation

Answer

Water miscibility and high polarity to dissolve all food components

Answer

Low molecular weight and high surface tension to maximize yield

Question 5

Stir bar sorptive extraction (SBSE, e.g., Twister®) offers a significant advantage over SPME for flavor profiling because it:

Accepted Answer

Provides a much larger volume of sorptive phase, improving sensitivity for trace aroma compounds

Answer

Requires no thermal desorption step, making it fully compatible with all GC injectors

Answer

Uses an aqueous stationary phase that selectively extracts polar flavor compounds only

Answer

Eliminates the need for any concentration step prior to GC-MS analysis

Question 6

In the context of flavor isolation, the term 'exhaustive extraction' means that:

Accepted Answer

Essentially all of the target analyte is removed from the sample matrix into the extract

Answer

The extraction procedure uses multiple sequential solvents of increasing polarity

Answer

The sample is heated to exhaustion to drive off all volatile components

Answer

All solvent is evaporated after extraction, leaving only the solid residue

Question 7

Which factor most critically determines the partition of a flavor compound between the SPME fiber coating and the sample headspace during static headspace SPME?

Accepted Answer

The distribution constant (Kfs) between the fiber coating polymer and the headspace gas

Answer

The total surface area of the SPME fiber exposed to the headspace

Answer

The molecular weight of the target compound relative to the fiber polymer

Answer

The ionic strength of the aqueous sample below the headspace