A flavor, like a musical chord, is made of a set of notes. The fullness of a flavor is the result of the interplay between the numerous chemical components that constitute the flavor’s profile.
A flavorist creating a fruity flavor – let’s say, peach flavor for an ice cream —will usually need a “green” or botanical note to round out the flavor. One of the popular chemicals used by flavorists to impart “greenness” is called cis-3-hexenol. A whiff of pure cis-3-hexenol reminds one of a freshly mowed lawn.
For our purposes the salient fact about this chemical is that it is composed of six carbons. In fact, most green notes are some variation on this six carbon theme. Just remember six, and we’ll come back to it shortly.
There are three standard methods for producing a green note. The third is the most sensitive.
The first is from petrochemical. A flavor chemical produced in this way is easily identifiable because it is being claimed, or promoted, as “nature-identical”. There is no kashrus consideration with cis-3- hexenol that is produced from petrochemical.
Green notes that can be labeled “natural” are recovered from the distillation of mint oil, from mint leaves. Fred Plaggi, of Frutarome, points out a drawback of this process.
The companies will effectively crush [mint leaves] up and extract it with chlorform methyl acetate, and then do fractional distillation to get the specific compounds they’re interested in. And they’ll derive four or five-dozen compounds at a time. The issue there is that a lot of times it’s hard to fractionally distill one compound from another one.
A third method also can be labeled “natural” and avoids the cumbersome process of fractional distillation. It involves taking a molecule that is eighteen carbons long and found in vegetable oils. The eighteen carbon molecule is spliced to the six-carbon molecule we’re looking for.
One candidate for a starting molecule is linoleic acid. It is a polyunsaturated fatty acid. “Unsaturated” means there are double bonds (represented by the horizontal double lines in the representation below) and “poly” means the double bonds occur more than once. There are eighteen breaks in the diagram below, each one representing the presence of a carbon.
Each of these double bonds is a potential reactive site. Notice that one of them is at the sixth carbon along the right side of the chain.
A double bond at the sixth carbon is only found in polyunsaturated fatty acids, and all polyunsaturated fatty acids are derived from vegetable oils, as opposed to animal fats. This is a good thing for kashrus.
However, a well known flavor company has a patent that refers to using oleic acid as a starting point. Oleic acid is often derived from animal fat. Oleic acid has a double bond in the ninth carbon. Dr. Claus Schmidt, the vice president for regulatory affairs for Symrise North America (who kindly provided background information for this article) could not figure out how oleic acid could be a feasible starting point. Dr. Schmidt speculated that the author of the patent was simply being exceedingly inclusive so as to minimize or eliminate the possibility that a competitor would use the method the flavor company described without having to pay royalties.
The fact that vegetable oil is a starting point does not get us out of the woods. As mentioned elsewhere in OU documents, vegetable oil fatty acids are not necessarily kosher since they are often produced in non-kosher factories.
There’s another concern. The mechanism for splitting the eighteen carbon molecule to a six carbon molecule is a lipase enzyme. Plant or microbial enzymes could be used but, according to Dr. Schmidt, animal lipase enzymes can be as inexpensive as a microbial enzyme and could, in theory, also be used.
Both the starting material and the enzyme used in the production of cis-3-hexenol and other green notes are sensitive. Therefore, in theory green notes are not acceptable without supervision on their production (compounds of these ingredients, such as cis-3-hexenyl benzoate, -butyrate, -isovalerate, and so on, are equally sensitive). However, according to Dr. Schmidt, there are only two actual manufacturers making use of this relatively sophisticated process. Both are kosher certified by well-respected agencies. The market for green notes, he added, is “settled”; there is no third party vying to enter.
In short, there are serious concerns involved in the production of green notes. However, we are familiar with the production facilities capable of producing green notes and in fact there does not appear to be any non-kosher product on the market.