Home / Summaries / Food Flavour Design / concentration-headspace-compound

Measuring Flavours in foods - Static and dynamic flavour analytics - methodologies for key aroma compounds identification and quantification

47 important questions on Measuring Flavours in foods - Static and dynamic flavour analytics - methodologies for key aroma compounds identification and quantification

Which cross modal interactions are there?

Between aroma, taste, sound, vision, texture and mouth feel.

What are the 4 phases in flavour analytics?

  1. Definition phase: sensory methods. Untrained or trained panel evaluated the product formulation. Results (e.g. Off-flavour, not creamy enough), are used as a base for flavour analytics.
  2. Discover. The (flavour) analytical phase: compounds analysed with different methods including in-vivo measurements. The importance and contribution of certain compounds to the flavour profile is investigated.
  3. Understanding: optimise or design new products on laboratory scale
  4. Delivery: continue from laboratory to pilot scale.

What are general characteristics of volatile aroma compounds?

  • Low boiling point
  • Limited solubility in water
  • Higher grades + faster learning
  • Never study anything twice
  • 100% sure, 100% understanding
Discover Study Smart
Testimonial person
Sophia
Law student
Quotes

For my 1st exam I got a C. Then, I started looking for ways to learn better and I came across Study Smart. Since then I have scored a A+, A, A- and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!

Testimonial person
John
Economics Student
Quotes

I was struggling to finish all my first-year subjects for 3 years. Then I discovered Study Smart, which helped me to finish all of them within 3 months.

Testimonial person
Sara
Public Administration Student
Quotes

Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, now I usually score an A or A+.

Testimonial person
Mary
Business Student
Quotes

Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!

Testimonial person
Melanie
Psychology Student
Quotes

Since using Study Smart, my average has increased significantly. I even completed a statistics course with a A+ while I'm bad at statistics. I took on extra courses this year, because of Study Smart. Thanks so much!

Testimonial person
Jane
Nursing Studies
Quotes

Ever since I started studying with StudySmart I passed all my exams !!! No more re-sits!! At first, I was happy with a pass and now I only get good grades. Many thanks!

Testimonial person
Rose
Political Science Student
Quotes

I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.

Testimonial person
Tina
Medicine Student
Quotes

I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on my grades, my speed and the pleasure I have in learning.

Testimonial person
Julie
Marketing Student
Quotes

For the first time, I finally feel totally confident about the way I learn. I have the perfect overview and make great progress in terms of speed and the grades I get. Thanks, Chris!

Testimonial person
Matt
Industrial Engineering Student
Quotes

I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..

Testimonial person
Emma
Law Student
Quotes

Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a huge amount of my time on creating my summaries.

Testimonial person
Michael
Psychology Student
Quotes

At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.

Testimonial person
Emily
Teacher
Quotes

Students that study with Study Smart get better grades. The system applies all the learning methods in such a way that both well-performing students and students who struggle perform much better.

Testimonial person
Richard
Literature Student
Quotes

Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!

Testimonial person
Madison
Parent
Quotes

The largest effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school, Study Smart made it happen.

Testimonial person
Robert
Accountant Student
Quotes

In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any D's. My average score is now an A and those are results I would have never had in the past

Testimonial person
James
Business and Science Student
Quotes

With my old method, I passed only 3 out of 8 courses. Since I started taking my notes digitally in Study Smart, I have passed all my courses on the first try. For me, StudySmart takes away the stress of wondering if I will pass or not.

Testimonial person
Christopher
Veterinarian Student
Quotes

Thanks to StudySmart, I passed all my exams, and with better grades than before! On top of that, I have mastered a very good study method now, which I am confident will help me earn my degree.

Taste compounds can have a major contribution to the overall flavour profile at very low concentrations. T/F

False

How can volatiles be isolated?

  • (Dynamic) headspace
  • Solvent extraction
  • (High vacuum) distillation
  • Sorption extraction

How can the obtained aroma extracts be analysed?

  • Gas chromatography (GC)
  • Mass spectrometry (MS)

What happens in the static headspace method?

It makes use of the equilibrium of a compound between the solution and the gas phase. If this equilibrium is known, upon analysis of the gas phase the concentration in the solution can be directly derived.

What are advantages of the static headspace method?

  • Relatively fast
  • Simple
  • Large number of samples at the same time

How can the concentration in the gas phase be influenced?

By changing the partition coefficient (K) or phase ratio (Beta). Both B and K low as possible gives highest possible concentration in gas phase.

How can the phase ratio be altered?

By increasing the sample volume, the headspace volume decreases and the phase ratio decreases.
Phase ratio (beta) = Vg/Vs

How can the concentration of the compound in the headspace be increased?

Cg = Co/(K + B). To increase Cg, the partitioning coefficient (K) or the phase ratio (B) should be decreased.
  • Decrease K: increasing temperature, addition of salt
  • Decrease B: increase sample volume

Why is increasing the temperature to increase the concentration of the compound in the headspace, not always that smart?

A temperature increase could start undesired reactions, cause other sample matrix components to go into the headspace, viking a pressure increase inside the vial. This pressure could affect the sampling process and in extreme cases even cause leakage or breakage.

What happens during dynamic headspace analysis?

A purge gas is let into the vial and takes the headspace along. The purge gas with headspace passes through a water condenser after which adsorption takes place on a tube filled with an adsorption material e.g. Tenax. After this extraction and subsequent concentration step, compounds can be desorbed again for GC analysis by heat (thermal desorption unit).

What is the difference in measurable compound concentration in dynamic headspace compared to static headspace analysis?

In dynamic it is higher, due to a higher sensitivity due to the concentration build up during adsorption.

What are the differences between SPME and static headspace analysis?

In SPME the compound is more concentrated, due to the exclusion of the introduced gas and because of a higher compound concentration caused by adsorption.

The SPME fibre can also be placed into the solution and adsorb compounds directly from the solution instead from the headspace. T/F

True

What is Stir Bar Sorbent Extraction (SBSE)?

It can be used for flavour isolation. The used stir bar contains an adsorption layer. The stir bar can be submerged into the solution inside the vial. The compound in the solvent wil establish an equilibrium between its concentration in the solution and adsorbed concentration on the stir bar.

What is headspace sorbent extraction (HSSE)?

Using stir bars that can be placed into the headspace. The stir bars are cleaned before washing them down, with for example water, before they are placed in the desorption unit (= solution).

SBSE can be used directly in a vegetable oil. T/F

False

Which equilibria occur during static, dynamic headspace, SPME and SBSE?

  • Static and dynamic headspace analysis: equilibrium between the concentration of the compound in the solution/sample and the headspace
  • SPME: equilibrium between the concentration of the compound in the solution/sample, the concentration of the compound in the headspace and the adsorbed concentration of the compound onto the fibre
  • SBSE: equilibrium between the concentration of the compound in the solution/sample and the adsorbed concentration of the compound onto the stir bar
  • HSSE: equilibrium between the concentration of the compound in the solution/sample, the concentration of the compound in the headspace and the adsorbed concentration of the compound onto the stir bar

What is the difference in sensitivity between SPME and HSSE

HSSE has a stir bar, SPME a fibre. The stir bar is more sensitive compared to the fibre, a higher concentration of the compound can adsorb onto the stir bar due to its higher surface area.

What is a disadvantage of using steam distillation to extract flavours?

High temperature (> 80-100 C) are used and is therefore prone to the occurrence of Maillard reactions.

Why is the SAFE technique often used?

It uses relatively low temperatures and high vacuum, so minimises the change of Maillard reactions.

What are advantages and disadvantages of headspace based extraction methods?

  • Advantages:
    • simple
    • fast
    • cheap
    • performed with minimal human assistance (automation)
  • Disadvantages:
    • low recovery values for the volatile compound after extraction
    • difficulties to extract low concentration of volatiles with a low odour threshold
    • new sample is needed for each separate analysis

What kind of extraction methods are SPME and HSSE?

Headspace extraction methods

What are advantages and disadvantages of distillation techniques?

  • Advantages:
    • high recovery values for compounds that are less volatile, after extraction. The SAFE has the highest recovery values for most compounds (not lactones).
    • possibility to perform multiple injections/extractions on one sample solution
    • further concentration possible
  • Disadvantages:
    • more laborious
    • more prone to contamination
    • not able to extract compounds that are more volatile

Why is 2C-GC used in flavour analysis?

It is not always possible to detect and analyse the different compounds using one column. It is possible to use two consecutive columns in the GC. The second column will provide an improved separation of the volatile compounds. This is called two dimensional gas chromatography (2C-GC).

GC is always combined with a detector. T/F

True

For which volatile compounds is the detector ECD?

Specific, Cl and Br

For which volatile compounds is the detector PID?

General, so a large variety.

What is GC/O?

Gas chromatography with olfaction (sniffing). Consecutive dilution of the same sample are injected into the GC. Less odours will be detected. The peaks in the gas chromatogram will correspond with the odours that are still detected after the final dilution.

What is the odour threshold value (ODT)?

The concentration at which an individual first perceives the stimulus (odour).

What is the odour activity value (OAD)?

The ratio of the concentration of a specific aroma compound over the ODT.
  • OAV > 1 --> concentration in sample is higher than ODT, compound is perceivable and contributes to the smell of the product
  • OAV < 1 --> concentration in sample is lower than ODT, compound unperceivable and does not contribute to the smell of the product

Which two types of ionisations are used for aroma compounds in MS?

  1. Electron Impact (EI)
  2. Proton Transfer (PTR)

What is Proton Transfer (PTR) ionisation?

The compound does not fall into fragments upon ionisation (like EI). The proton transfer is perfumed using the cation of water, H3). The ionisation of the volatile compound is required for the compound to pass through the ion filter, a magnetic tube. All compounds that have not been ionised are pumped away by a vacuum. After the ion filter the ions will each reach the detector. Intact ions, composed of the original volatile compound and an added proton, will reach the detector. Due to the lack of fragmentation, no compound specific spectrum is obtained.

What is the difference between EI and PTR ionisation?

In EI the compound falls into fragments upon ionisation, in PTR not. This makes it harder to identify the different compound in a PTR-MS spectrum. It can however be used to have a fast indication of the compound composition of a sample.

Which two categories of MS exist? And what are their differences?

  • High resolution MS (HRMS)
    • can measure mass more accurately
    • can detect minimal differences in mass between multiple compounds based on differences in the decimal numbers
  • Low resolution MS (LRMS)
    • overlaying peaks, cannot detect differences in mass between multiple compounds

How can flavour perception be analysed in vivo during product consumption?

With PTR-HRMS.

How can flavour perception and (multi) compound interactions be analysed?

  • Product reformulation or recombination: a flavour compound is added to the original product and evaluated for its masking properties by follow up sensory testing
  • Olfactometry/Gustometry

How does an olfactometer work?

An olfactometer contains multiple flasks with different flavour compound solutions. Using a pipe, an air flow is introduced into each flask. This air flow causes bubble formation in the flasks, resulting in the release of flavour compounds into the gas phase, the bubbles. The flavour compounds are subsequently transported out of the flask and into the nose of the consumer or trained panellist who is performing the sensory evaluation.

The olfactometer can be used to test masking of off-flavours and enhancing of flavour, how?

  • The olfactometer delivers the off-flavour or flavour
  • GC-O delvers the aroma compound to be assessed for its masking potential or enhancing potential.

What is a gustometer?

An olfactometer but then for taste. It contains pumps comparable to those used in High-Performance Liquid Chromatography (HPLC).

Which compound can mask methional (gives a potato off flavour)? Is this desirable?

Octanol. Gives a citric flavour, desired in orange juice and Radler beer, but not in regular beer.

What aroma do you get when combining methional (potato) and z-1,5-octadien-3-one (harsh geranium)?

Fishy aroma

How does the Composcent work?

  • It consists of an input, a GC and an output.
  • The input is the headspace, with the volatile compounds, of a sample (product). Inside the column of the GC, the aroma compounds of the headspace are separated. At the end of the column, the headspace of the sample is collected in two vials, the output.
    • One vial contains the flavour profile without separated aroma compound
    • Other vial contains the separated aroma compound

In direct-MS, no GC is used. T/F

True

What method to use when you want to screen key-aroma compounds in a product flavour?

Omission (Composcent).

The question on the page originate from the summary of the following study material:

Food Flavour Design

View summary
  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo

Topics that are related to Measuring Flavours in foods - Static and dynamic flavour analytics - methodologies for key aroma compounds identification and quantification

Summaries related to Flavour Generation