Laboratory Techniques & Safety Flashcards

What is a major drawback of Likens-Nickerson simultaneous distillation-extraction (SDE) for flavor isolation?

Answer: Prolonged heating can create thermal artifacts such as Maillard or degradation products

Boiling the sample for an extended time can generate compounds not present in the original food.

In a Stable Isotope Dilution Assay (SIDA), what makes the internal standard ideal for quantifying a key odorant?

Answer: It is an isotopically labeled analog of the analyte that behaves identically during workup

Labeled analogs compensate for extraction losses and are distinguished from the analyte by mass spectrometry.

Which analysis can distinguish vanillin made from petroleum-derived guaiacol from vanillin of recent biological origin?

Answer: Carbon-14 (radiocarbon) content

Fossil-derived carbon contains no 14C, while biobased vanillin carries modern 14C levels.

Which stationary phase type is used in GC to determine the enantiomeric ratio of chiral flavor compounds such as linalool for authenticity testing?

Answer: Derivatized cyclodextrin

Derivatized cyclodextrin phases separate enantiomers, revealing racemic synthetics in 'natural' materials.

Which is the most important criterion when choosing an internal standard for GC quantitation of a flavor?

Answer: It must not be naturally present in the sample and should elute in a clear region

A good internal standard is absent from the sample, chemically similar to analytes, and fully resolved.

When accurately dispensing a viscous or highly volatile flavor ingredient by volume, which pipette type minimizes error?

Answer: Positive-displacement pipette

Positive-displacement pipettes have a piston in direct contact with the liquid, eliminating air-cushion errors.

Why are high-impact aroma chemicals usually evaluated on smelling strips as 1% or 0.1% dilutions rather than neat?

Answer: Neat materials can overwhelm and fatigue the nose and distort the true character

Potent odorants smelled neat cause olfactory fatigue and can show a different character than at use levels.