Meat Flavor -Chemistry and Perception

Gary ReinecciusDept. of Food Science and Nutrition

Saint Paul, MN

greinecc “at” umn.edu

Presentation

• Overview of the evolution of flavor chemistry

• Chemically define meat flavor• Future hurdles

Historical view

• Modern flavor chemistry is barely 40 years old

• Knowledge progresses via evolution

“Holy Grail”

• Chemically characterize the “flavor” of a food

• Define the chemical components needed to provide the required sensory stimuli to yield the desired perception

– Compounds and their concentration limits

First efforts

• Identification of aroma compounds in foods• Developed long lists covering most food

products (> 7,000 cpds to date)

• Objective: Identify all of the volatiles in a food so that the “flavor” can be reproduced

Source: TNO-CIVO Volatile Compounds in Foods (Beef)

Result?• Found thousands of new compounds in

foods/nature• Proposed many pathways and precursors• Better understanding of nature

• Solve problems? No• Could not duplicate nature based on this

data - could not define flavor from this data

Period of statistical correlations

• Collect gas chromatographic data to use in correlations with sensory data or product data.

• 1970s

• Can we predict sensory properties based on GC data?

“Yes” and “No”

• Can do OK in terms of simple off flavors

• Predict desirable flavor? - poor success rate

What are “defining” volatiles in a food?1980s to present

• Concept of “Odor Units” developed many years ago

• Approaches promoted by Acree (Cornell),Grosch (Germany), McDaniel (Oregon State) and Pollien et al. (Nestle, Switzerland)

Terminology

• Odor Units• Acree - CHARM• Grosch - D values, Odor Activity Values• McDaniel - OSME• Pollien et al., NIF (nasal impact frequency) or

SNIF (surface of nasal impact frequency)

Methodology

• Isolate sample (liquid extract andheadspace)

• Concentrate• Inject into GC and get KI and profile• Smell GC effluent• Note start and stop of odors (and intensity

for OSME)

Sample Data

Data interpretation

• Quantify the compounds that have the highest sensory values (OSME, CHARM, OAV, etc.)

• Divide quantity present by sensory threshold -Odor Activity Values

• “Suggests” importance to the aroma of the food

Odor activity values of “key” volatiles in roasted beef (Cerny and Grosch, 1993).

Odor activity valueOdorantNasal Retronasal

4-Hydroxy-2,5-dimethyl-3(2H)-furanone

9 31

2-Acetyl-2-thiazoline 28 282-Ethyl-3,5-dimethylpyrazine 3 222,3-Diethyl-5-methylpyrazine 27 540Guaiacol 1 3Methional 7 313

“Key” volatiles in meatsGasser and Grosch, 1990)

FD FactorsCompound Chicken Cow Ox2-Methyl-3-furanthiol 1024 512 512Bis(2-Me-3-furfuryl)disulfide <16 2048 10242-Furfurylthiol 512 512 2562,5-Dimethyl-3-furanthiol 256 <16 <163-mercapto-2-pentanone 128 32 32Methional 128 512 10242,4,-Decadienal 2048 64 322-Undecenal 256 <16 <16

Add the selected compounds to an unflavored base (deodorized base).

• Subject the sample to sensory analysis.• How to do - Problematic!

– Compound selection? - Compounds below their sensory threshold may impact the perception of other compounds.

– How to evaluate their contribution? Omission testing?

Useful? Absolutely!

• Pathways leaning to meat flavor -understanding of the process, also stability

• But still do not have the ability to reproduce a flavor by simply mixing this set of compounds - problem?– Not right compounds? or– is it their “RELEASE”?– Or ???????

Flavor Release

• The freeing of volatiles during eating

• Key figures: Andrew Taylor/Rob Linforth et al in Nottingham, UK (others less involved but make important contributions)

“Nose space” (Breath Analysis)

• Techniques for measuring the amount of odorants in the breath during eating (in real time)

• Mass spectrometry based

Breath sampling (Roberts et al. 2003)

Rob Linforth - Nottingham

Chewing gum

Menthone in nosespace

Sensory intensity

Sucrose

Study using a model system

• Supplied acid, sugar and aroma (strawberry)• Measured all stimuli and sensory intensity

• Stopped acid -• Stopped sugar -• Stopped aroma-

Outcome

• Learned a lot about what influences the release of aroma compounds to be sensed

• But …..

Non-volatiles?

• Just beginning to understand their role in perception and interactions

• Major obstacle

Current frontiers

• Non-volatiles

• Brain functioning and perception (Major symposium in NYC this past year)

New paradigm for flavor industry

• To solve unsolved problems:– Recognize that they cannot simply sell drums

of volatiles any more– Must offer a complete package of stimuli -

alone or in conjunction with the customer

In conclusion

• Where are we in our quest for the “Holy Grail?

Duplicate Nature?

• Only within limits - some “simple” foods -can come close

• However, NO food flavor has been chemically characterized– What volatiles are necessary and the limits of

each of them to provide an acceptable flavor– What non-volatiles are required?– What other stimuli are required?

Flavor research?

• Can identify compounds that may beneeded to reproduce the aroma component of flavor

• Long way to go without the understanding or tools to go there– Non-volatiles– Sensory knowledge and techniques– Understanding of perception

Recognition that perception is multi-modal

• Must supply color, appearance, mouth feel, sound (crispness), taste, aroma and even environment!

• Must supply the brain with ALL the stimuli expected to be associated with a food - not just aroma