Flavor Bites: trans-2, cis-6 Nonadienal


I am very fortunate in terms of food fads; there is only one food I actually dislike – cucumber. I have hated cucumber as long as I can remember. It was an inevitable ingredient of salads during my childhood, and I became very adept at inconspicuously avoiding eating it. Travel and working in the flavor industry broadened my tastes but did nothing to diminish my instant disgust at the mere sight of the evil green veggie on my plate. The arrival of sushi restaurants was a turning point. I love sushi. How could I love sushi when it often had bits of my hated veggie rolled up inside it? The answer is the level of the offending smell. At one hundred percent, especially with the skin on, cucumber is still overpoweringly obnoxious. At a trace level in sushi, it is very pleasant. I now even cook fish with a sauce based on lightly cooked, skinless cucumber.

The same logic applies to trans-2, cis-6 nonadienal, also known as cucumber aldehyde or violet leaf aldehyde (FEMA# 3377, CAS# 557-48-2). It has a very powerful green, cucumber aroma. Opening a bottle of this chemical is not a pleasant experience for me, but at very low levels it adds a lovely fresh character to a wide range of different flavors.

Note that the dose rates given throughout this article are the levels suggested for use in flavors intended to be dosed at 0.05% in ready-to-drink beverages or in a simple bouillon.

Vegetable Flavors

Cucumber: Logically, we have to start out this article with cucumber flavors. My suggested starting level is 500 ppm. This recommendation has to be taken with a bit of a pinch of salt because I’m probably oversensitive to this primary odor. Higher levels are probably very acceptable for most people.

Pepper, Bell: The effect of this ingredient in bell pepper and jalapeño flavors is much more subtle. These flavors are often dominated by methoxy pyrazines. These chemicals are very compatible with the green note of trans-2, cis-6 nonadienal, which adds freshness to the profile. A good initial level is 30 ppm.

Potato: Obvious green notes are not exactly attractive in any type of potato flavor. We are correctly taught to avoid green potatoes. Subtle additions are a different story. Low levels, around 10 ppm, of trans-2, cis-6 nonadienal are especially attractive in boiled potato flavors, but they also work well in fried potato profiles.

Tomato: Tomato flavors can suffer from a similar problem to bell pepper flavors. In this case, the dominant note is often iso-butyl thiazole. trans-2, cis-6 Nonadienal at 50 ppm adds complexity and freshness to raw tomato flavors. This ingredient can also be helpful in cooked tomato flavors, but the ideal level is lower, nearer to 20 ppm.

Tropical Fruit Flavors

Guava: Guava flavors often need a little hint of freshness and trans-2, cis-6 nonadienal, at levels of addition in the region of 15 ppm, is ideally suited to provide a very compatible fresh note.

Kiwi: In my experience, kiwi is a different story and quite a subtle and challenging flavor category. This ingredient adds a hint of complexity to the overall green note at a tiny level of addition, around .5 a ppm.

Mango: Only 10 ppm of trans-2, cis-6 nonadienal is needed to help brighten the green note in any style of mango flavor. Higher levels are also interesting and can give an interesting effect in flavors with a strong mango skin character.

Watermelon: All melon flavors, but especially watermelon, benefit from around 10 ppm of this ingredient, adding subtlety and freshness.

Other Fruit Flavors

Apricot: The ideal level of addition of this ingredient in apricot flavors is 5 ppm, modifying the more obvious green notes. This level works equally well in fresh and dried apricot profiles.

Blueberry and Bilberry: trans-2, cis-6 Nonadienal at 10 ppm gives a pleasant top note to blueberry and bilberry flavors, lifting the floral notes.

Cherry: Black cherry flavors can accept up to 15 ppm of this chemical. The combination also works for red cherry profiles, but the ideal level is a little lower, around 10 ppm.

Cranberry: trans-2, cis-6 Nonadienal is arguably not really a logical ingredient for cranberry flavors but a tiny addition, as little as .5 a ppm, can be subtly enhancing.

Fig: Fig flavors probably belong in the novelty category, but the profile is very attractive, either fresh or dried. Around 5 ppm of this ingredient is ideal in either profile.

Grape, Concord: trans-2, cis-6 Nonadienal at 20 ppm gives a nice lift to Concord grape flavors. The ingredient also works in white grape flavors but should be used at a significantly lower level, nearer 5 ppm.

Peach: An attractive level in fresh peach flavors is 5 ppm, giving a little lift to the main green notes.

Strawberry: Much lower levels, around 1 ppm, are preferred in fresh strawberry flavors. This is probably because this ingredient can resurrect memories of a very traditional strawberry flavor ingredient, methyl heptine carbonate.

Savory Flavors

Beef, Roast: Why would such an obviously green note work in savory flavors? The answer lies in the cooked fat notes. trans-2, cis-6 Nonadienal works by adding a hint of freshness to the routine series of trans-2 enals and trans-2, trans-4 dienals, notes that can easily tip into stale characters if overdone. A good starting level for roast and BBQ beef flavors is 20 ppm.

Bread: This raw material adds a hint of freshness to bread and pizza base flavors at 10 ppm.

Chicken and Pork: The same comments about freshening fatty notes apply to chicken and pork as well as to beef. The ideal level is a little lower, around 10 ppm, with higher levels in roast than in boiled flavors.

Fish and Seafood: Low levels, 5 ppm in fish and 10 ppm in seafood flavors, add subtlety to perceived freshness, which is especially important in these flavor categories.

Other Flavors

Coffee: Freshness is probably the biggest single challenge in formulating coffee flavors. trans-2, cis-6 Nonadienal simply adds a subtle hint of freshness and welcome complexity at levels in the region of 10 ppm.

Pandan: Pandan flavors can easily be very simplistic and lacking in authenticity. trans-2, cis-6 Nonadienal can be very helpful at 10 ppm.

Tea: Green, red and black tea flavors all really benefit from this ingredient. Unsurprisingly, green tea flavors can accept higher levels, around 100 ppm. Black and red tea flavors are better served by 50 ppm.

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