Fantastic Flavours Pty Ltd
Australia
Flavour Chemistry
How is your chemistry?
Although we don't think of it, its amazing just how much chemistry is going on all around us. With food, wine, coffee and fresh bread, all change rapidly on exposure to air. Its how we tell if the food is fresh! If the reaction occurs we won't smell the "fresh, unreacted" aromas that we associate with the fresh product.
Thiols which have very low flavour thresholds are easily oxidised so that is why Expresso Coffee is best fresh. Using freshly roasted beans and grinding just before extraction are key to minimising aroma loss due to oxidation.
Thiols are also present in some wines and give a tropical note at very low concentrations but if the wine is exposed to air they react (oxadise) and become odourless.
The valencene in canned orange juice reacts with the metal and produces nookatone which gives canned orange a grapefruit note.
Most flavourists rely more on experience than chemistry. I often wonder why something happens and approach the chemists only to find they are often specialists themselves and cannot help. When there is a breakthrough in flavouring, chemists are involved and this leads to new aroma substances or ways to prevent a flavour substance from being oxidised or hydrated. When flavour compounds are added to a food they change, d Limonene hydrates to terpineol in water and acid. Hence the high alpha Terpineol in distilled lime oil and none in cold pressed. Furaneol the new sugary compound in strawberry changes while the old fashioned ethyl maltol remains the same. Vanillin seems to react with everything, is often overdosed because it is cheap
Thiols which are an important component of wines and other tropical flavours as well as coffee, deterioate very quickly in air.Oxygen reacts fairly quickly with these thiols and extremely fast if the oxygen is in the form of ozone. If you are a winemaker you need to protect your wine from oxygen if you want to preserve the delicate aroma of trace thiols.Beer and blackcurrant are amongst the thiol flavours.Ground Coffee needs to be stored in a fridge for similar reasons.
Thiols that are used in town and natural gas are quickly destroyed in the flames.
So it helps to know chemistry or at least try and understand what is happening.
The links on this page are to some interesting sites.
| Aroma Impact Components Newly Identified in Foods | |
| Bread crust, wheat | 2-Acetyl- 1 -pyrroline |
| Beef meat, boiled | 2-Methyl-3-furan thiol |
| Beef meat, roasted | 2-Acetyl-2-thiazoline |
| Beef meat, stewed | 12-Methyltridecana |
| Coffee, roasted | 3-Mercapto-3-methylbutyl formate |
| Cheese (Emmentaler) | Furaneol, homofuraneol |
| Grapefruit | 1 -p-Menthene-8-thiol |
| Wine (Sauvignon) | 4-Mercapto-4-methyl-2-pentanone |
| Tea, green | 3-Methyl-2.4-nonanedione |
| Lovage | Sotolon |
Look up the chemical structures using Wolfram/Alpha
Symrise range of aroma chemicals
The science of flavour creation
Science Lecture esters
Flavour Science
Not all volatile substances have odours. The shape and polarity of the compounds determine their odour. There are numerous optical isomers with different odours.
l-carvone is spearmint whereas d-carvone is dill or caraway. Several lactones and ionones have different odours depending on their optical rotation. It is to be expected that one optical isomer will have a different threshold to its mirror image.
It is only in recent years that such compounds could be separated on special GLC columns.
This phenomenon explains the various claims that “natural” is better, meaning that synthetically made aroma compounds are different to those in nature.
Threshold value the concentration an aroma or taste can be detected
(air, water and fat) Flavour components thresholds
Recognition Threshold The concentration at which you can identify an odour.
(air, water and fat)
Odour unit the concentration divided by the threshold
Flavour impact value the rate of change in perception with concentration.
The flavour contribution of a aroma component in a mixture to the total profilecan be calculated from the total odour units and the number contributed by that aroma chemical.
Threshold in a food is dependant upon:
The threshold of an the aroma in air.
Concentration in the food
Solubility in oil and water
Its Vapour pressure
Partition coefficient between the air and the food
pH of the food some aroma compounds are effected by the pH, weak organic acids are protionated at low pH making them less soluble and hence more volatile.
The concentration of an odour above a food is dependant on its solubility in that food and its vapour pressure and concentration in that food.
Additive and Synergistic effects
The other aroma components, concentration and thresholds needs to be determined.The synergetic effects of these and their additive effects need to be determined.
If we know the flavour threshold for each component in a flavour and divide it by its threshold value we can calculate the number of odour units that component contributes to the total flavour. From this information we could produce a flavour profile.
Threshold values of Vanillin and Ethyl Vanillin
Threshold (ppb)
Ethyl Vanillin
Vanillin
Detection smelling in water
0.1
0.2
Recognition smelling in water
1
4
Water by tasting
1
4
Odour threshold in air
0.01 ng/litre
0.02 ng/litre
Vapour pressure
1.9 mg/l
1.8 mg/l
Kirk Othmer (vol 10, 1993)
pH effect examples
Trimethylamine has a strong fishy smell, with lemon juice or vinegar this alkaline compound is neutralised to the organic salt.
Milk sours and develops a distinctive smell. This is aided by the formation of lactic acid which reduces the pH making acids such as butyric less soluble and more volatile.
The opposite effect is achieved by bicarbonate of soda when used to deodorise carpets.
The carpet which has free short chained acids is neutralised by the action of the bicarbonate which produces non volatile salts.
d-limonene is hydrated to alpha terpineol in acid drinks. Lemon-containing drinks move to a lime taste with age.
Flavour perception
How the public views a flavour is often measured by sensoric evaluation companies.
By presenting a sample and asking questions, they determine if the product is acceptable to the target market. Marketing people place reliance on this scientific evaluation of a new products using this method. However there have been numerous failures that rated highly in such tests and numerous successes that fared poorly. Taste preferences are acquired or learned. To design a flavour that will give a high rating in such a test you need to study the flavour of the leading brands. Type of flavour, colour strength, acidity, sweetness, salt level and umamy level are probably at the optimum levels and would score highly in such tests. You need to compose your flavour to mimic these key parameters and expand the flavour profile to give a “different aroma”. With sweet flavours the classic combination of lemon ,lime, vanilla always rates highly in soft drinks.
Useful links
30years of Flavour Chemistry (google books)
ABC Chemistry great catalogue of Journals in Chemistry
Big Links for flavour and aroma
ChemoReception Web lots of links
Cornell useful links List of flavour sites on Cornell University site
Dr. T.E. Acree Excellent scientific approach to flavours Flavournet links
Flavour History, Society of Flavour Chemists Large presentation, wait for it!
Isotope analysis Testing if the sample is natural
Maillard reactions Candy, coffee and Roast beef have Maillard reactions in common
Review of the flavour/aroma of rice
Strawberry Flavour Ingredients
Taste - A brief tutorial by Tim Jacob
The Society of Flavour Chemists
Tobacco additives and flavours
Nootkatone has another use?
Nootkatone, So A-peeling in Grapefruit, is Repellent to Mosquitoes and Ticks
Bruce V. Bigelow 4/28/11
When I profiled Allylix last summer, CEO Carolyn Fritz explained how the San Diego startup was using genetically engineered yeast and proprietary fermentation technology to produce specialized “aroma chemicals” for the $1.9 billion flavor and fragrance market. The company’s first product was a compound with a keen grapefruit taste and smell called nootkatone, a flavor enhancer previously extracted from grapefruit peels through a costly process.
Nootkatone is just one example of a huge class of molecules known as terpenes—naturally occurring compounds that Fritz said also happen to be highly prized in markets for pharmaceuticals, flavors and fragrances, and insect repellents.
Now, the Centers for Disease Control and Prevention are pushing to develop nootkatone as a completely natural insect repellent, according to a recent report from National Public Radio.
Unlike DEET, (also known as also known as N,N-Diethyl-meta-toluamide), which is the most common active ingredient in conventional insect repellents, CDC officials say nootkatone is nongreasy, dries quickly, and has a very pleasant, citrus-y grapefruit odor. Nootkatone also is so nontoxic you can actually drink it, as it’s already an approved flavor-enhancing food additive used in grapefruit-flavored drinks like Squirt. Yet nootkatone is highly toxic to mosquitoes, ticks, and other insects.
In an e-mail to me, Fritz writes, “In addition to being a flavor and fragrance, nootkatone is an effective insect repellent, and is the most effective tick repellent tested by the CDC. It has the added benefit of a natural product [officially designated as] GRAS (Generally Regarded as Safe).”
She adds, “We and another company have co-exclusive rights to the CDC’s patents on the use of nootkatone as a repellent. It’s actually quite exciting.”
One CDC official who talked with NPR said nootkatone is so nontoxic that it could someday become an ingredient in the world’s first all-natural and environmentally safe insecticidal soap. The challenge, according to the NPR report, is that nootkatone produced conventionally from grapefruit peel is expensive—about $4,000 per kilogram (about 2.2 pounds).
Producing nootkatone at lower cost, however, is one of the advantages addressed by the technology under development at Allylix—which might be why Fritz views nootkatone-based insect repellent as “exciting.”
Bruce V. Bigelow is the editor of Xconomy San Diego. You can e-mail him at bbigelow@xconomy.com or call 858-202-0492
Pentadecanolide
Noble prize Chemistry Leopold Ruzicka The Nobel Prize in Chemistry 1939
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Fantastic Flavours Pty Ltd
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