Essential oils treated to remove harsh notes therefrom

Essential oils extracted from botanical material are treated with a peroxide-acid reagent to remove harsh flavor off-notes therefrom.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates to essential oils extracted from botanical 
matter which are treated with a peroxide-acid reagent to remove harsh 
flavor notes therefrom. 
Description of the Prior Art and Other Related Art 
Essential oils which are freshly distilled from botanical matter usually 
have, when freshly made, what are known as harsh tasting flavor notes. 
These harsh flavor off-notes are also known as green, burnt, still 
off-notes. This is particularly true in the case of peppermint oil or 
spearmint oil which is freshly made by means of steam distillation of the 
present botanical matter from which the oil is extracted. The customary 
procedure employed for removing those harsh flavor notes which are present 
in the freshly obtained oil is to allow the oil to age or mellow for 
periods of about 6 to 24 months, in full containers in the presence of 
oxygen and in the absence of actinic radiation. This aging-mellowing 
process is economically unattractive since it requires the use of 
carefully monitored storage facilities, for long periods of time and 
supervised by technically trained personnel. All of these storage 
requirements are economically burdensome. 
U.S. Pat. No. 4,478,864 discloses the treatment of freshly prepared 
peppermint oil with maleic anhydride for the purposes of preventing the 
formation of certain off flavor notes during the aging process. This 
process removes most of the menthofuran from the fresh peppermint oil, in 
the form of a menthofuran-maleic anhydride complex. Thus, very little 
menthofuran is present, during the aging process, to oxidize to produce 
undesirable flavor notes. This process, however, does not cure all the 
off-flavor note problems inherent in fresh peppermint oil. An essential 
oil treated by the process of U.S. Pat. No. 4,478,864 may still have to 
undergo an aging process to remove off-flavor notes that are present in 
the freshly prepared oil. 
In U.S. patent application Ser. No. 727,509 filed by the present inventor 
on Apr. 26, 1985 and entitled "Essential Oils Treated To Remove Harsh 
Notes Therefrom", which has issued as U.S. Pat. No. 4,613,513 there is 
disclosed a process for treating essential oils with Fehlings solution to 
remove harsh flavor notes from the oils. 
Prior to all of the present inventors work, therefor, it has not been 
possible to treat freshly made essential oils in a facile manner so as to 
readily remove therefrom harsh flavor off-notes then present therein with 
a reagent that can be readily removed from the oil. 
OBJECTS OF THE PRESENT INVENTION 
An object of the present invention is to provide essential oils which are 
freshly extracted from botanical matter and which are rendered free of 
harsh flavor off-notes present in the fresh, unaged oil. 
A further object of the present invention is to provide a facile process 
for treating freshly extracted essential oils of botanical matter so as to 
readily render them free of harsh flavor off-notes then present therein. 
SUMMARY OF THE PRESENT INVENTION 
It has now been found according to the present invention that essential 
oils freshly extracted from botanical matter which then contain harsh 
flavor off-notes can be readily freed of such harsh flavor off-notes by 
treating the oil with a peroxide-acid reagent. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The peroxide-acid reagent which is used to treat the essential oils in 
accordance with the present invention is a combination of one or more 
water soluble inorganic peroxides such as hydrogen peroxide and/or ozone 
and one or more water soluble inorganic acids such as hydrochloric acid, 
sulfuric acid and phosphoric acid. The peroxide is the active agent in the 
reagent system of the present invention. The acid is merely used to 
acidify the peroxide. 
The acidified peroxide is employed in amounts which are sufficient to 
remove at least substantially, if not all, of the harsh off-flavor notes 
that are present. The amount of harsh flavor notes that are present will 
vary from one sample of the essential oil to another. 
The acids are preferably employed as aqueous solutions having an acid 
concentration of about 10 to 40, and preferably of about 30 to 40, weight 
percent. 
The hydrogen peroxide is preferably employed as an aqueous solution having 
a peroxide concentration of about 30 to 50, and preferably of about 30 to 
40 weight %. The ozone is preferably employed at a concentration of about 
1-5 ppm in deaerated water or at a concentration of about 0.2 to 0.3% in 
air (at 20.degree. C.). The ozone is generated on site by techniques well 
known in the art. 
Aqueous solutions of the peroxides and/or acids having higher or lower 
concentrations may also be used. 
The peroxide and acid components of the reagent are added together to the 
oil to be treated therewith, as disclosed below. 
The essential oils which are to be treated with the peroxide-acid reagent 
in accordance with the present invention are the freshly extracted 
essential oils of botanical matter. These oils are used as flavorants in 
the food, confectionary, perfume and cosmetic industries. These oils would 
include those obtained from the following botanical materials: anise, 
basil, dill weed, chamomile, eucalyptus, fennel, geranium, hop, laurel 
leaf, lemongrass, bois de rose, caraway, amber, camphor, amyris, galbanum, 
davana, mentha (spearmint and peppermint). 
The essential oils which are to be treated with the peroxide-acid reagent 
in accordance with the present invention may be extracted from their 
parent botanical matter, ie, leaves, fruit, bark, root, grass, wood, 
heartwood, gum, balsam, berries, seed, flowers twigs and buds, by the 
commonly employed technique for doing so, i.e., steam distillation. 
The fresh oil may be rectified (redistilled) prior to or after treatment 
with the peroxide-acid reagent to improve a particular property 
characteristic. For example, peppermint oil may be rectified to remove 
dimethyl sulfide therefrom which provides a green weedy note. 
The harsh flavor off-notes in the fresh essential oils, which are to be 
removed by treatment with the peroxide-acid reagent, may be characterized, 
as such, organoleptically. Organoleptically these harsh off-flavor notes 
may be characterized as: harsh, green, raw, weedy, skunky and burnt. 
The chemical components of the fresh essential oils which are believed 
responsible for the harsh (tasting) flavor off-notes have not been 
determined analytically. They are present, at most, at trace 
concentrations in the oil. When the essential oils are analyzed by gas 
chromatography prior to and after the treatment of the present invention, 
no apparent changes in the composition of the volatile components of the 
oil can be detected (analytically). 
By volatile components it is meant those components of the oil which are 
volatile enough as to be capable of being detected by gas chromatography 
analysis using a Carbowax-20M column operated at a maximum temperature of 
230.degree. C. and with an injector temperature of a maximum of 
250.degree. C. 
In treating the essential oil with the peroxide-acid reagent according to 
the present invention the oil may be extracted in a liquid/liquid 
extraction with the peroxide-acid reagent, or it may be contacted with the 
peroxide-acid reagent immobilized on a solid support. 
About 0.005 to 8.0, and preferably about 0.005 to 2.0, and most preferably, 
about 0.01 to 0.03, percent by volume of each of the hydrogen peroxide and 
the acid components of the reagent of the present invention is used in 
treating the oil therewith, when using the hydrogen peroxides and the 
acids as 10 to 50% and preferably 30 to 40%, by weight aqueous solutions. 
Correspondingly larger or smaller volumes of the hydrogen peroxide and 
acid components would be needed when more dilute, or less dilute, 
solutions of these reagents are used. The ozone is supplied in such 
amounts as are comparable to the amounts of hydrogen peroxide that would 
be required. 
The peroxide and acid components are added to the oil, for the purposes of 
conducting the treatment therewith of the present invention, by adding 
such components together. The acid is used to form an acidified peroxide. 
The treatment with the peroxide-acid reagent may be conducted at room 
temperature, of about 20.degree.-25.degree. C., although at higher 
temperatures a more rapid/efficient extraction may be effected. The 
liquid/liquid extraction may be done by vigorously shaking a mixture of 
the oil and the peroxide-acid reagent in commonly employed shaking devices 
designed to effect efficient liquid/liquid extraction systems. Depending 
on the amount of peroxide-acid reagent used, the size of the oil sample 
being extracted, and the amount of harsh flavor off-notes initially 
present in such sample, and the shaking device employed, the extraction 
time required may be about one to ten minutes. 
Only one treatment of the oil with the peroxide-acid reagent is needed in 
order to adequately accomplish the removal of the harsh flavor off-notes. 
With such a treatment all of the harsh flavor notes are readily removed. 
After the aqueous peroxide-acid reagent is used to treat the essential oil 
in the liquid/liquid extraction process, it is readily moved therefrom by 
the use of oil/water separating devices such as a separatory funnel, with 
or without prior centrifuging. Residual traces of the peroxide-acid 
reagent can be further readily extracted from the oil by treatment with a 
solution of Na.sub.2 CO.sub.3 (to neutralize the acid) followed by washing 
with distilled water. The oil is then dried by high speed centrifugation. 
Contrary to the teachings of U.S. Pat. No. 4,478,864, whereby the agent 
which would cause the creation of the off flavor note (upon aging in the 
oil) is actually removed from the fresh oil as a menthofuran-maleic 
anhydride complex, the agent(s) which are causing the off-flavor notes in 
the fresh oil, and which are treated with the peroxide-acid reagent 
according to the present invention, are not removed from the fresh oil by 
such treatment. The peroxide-acid reagent presumably oxidizes the agents 
causing the off-flavor notes in such a way as to then render them 
innocuous from an off-flavor point of view. Thus, it is not necessary to 
further age the fresh oil, as is otherwise commonly done, to accomplish 
the same result. 
The treatment of the fresh essential oil with the peroxide-acid reagent can 
be accomplished before or after any treatment of the oil according to the 
process of U.S. Pat. No. 4,478,864. 
The various types of products into which the essential oils of the present 
invention may be added as flavors or fragrances would include food, 
confectionary, including chewing gum and pressed mints, perfumes, cosmetic 
and body hygiene products and medicinals. 
The following examples are merely illustrative of the scope of the present 
invention and are not intended as a limitation upon the scope thereof.

EXAMPLE 1 
A 100 ml sample of freshly distilled peppermint oil is shaken, in a 250 ml 
separatory funnel, with 0.02 grams each of 30% by weight aqueous H.sub.2 
O.sub.2 and 12N HCl for 1 to 2 minutes. The aqueous (bottom) layer is 
discarded after complete separation of the layers. The peppermint oil 
layer is washed by extraction with 2.times.50 ml 5% sodium carbonate 
solution and 2.times.50 ml distilled water, and the completely separated 
aqueous layer is then discarded. The oil is dried with 4 g anhydrous 
sodium sulfate and by centrifugation at 2000 to 3000 rpm. 
The resulting oil is crystal clear and possesses a clean characteristic 
mellow aroma of a good quality aged peppermint oil. The harsh 
objectionable aroma of the starting oil is eliminated. The taste of the 
treated oil, when evaluated in a sugar fondant at 0.2 weight percent level 
and in a chewing gum at about a 0.5 to 1.5 weight percent level, is 
similarly improved from that of the starting oil. 
EXAMPLE 2 
A sample of freshly distilled spearmint oil is also treated according to 
the procedure of Example 1. A similar improvement of the treated oil is 
noted. 
The magnitude of improvement in a treated oil depends on the quality of the 
starting oil; the more objectionable and the harsher the starting oil is, 
the more dramatic is the improvement obtained by the treatment thereof 
according to the present invention.