DERIVATIVES OF DIACETYL AS FLAVOURING AGENTS

The present invention relates to dioxolanones and dioxanones having the ability to release diacetyl (2,3-butanedione) upon elevated temperature. It further relates to a process of their production and flavour products comprising them.

Diacetyl is a well known butter flavour ingredient possessing a sweet, strongly buttery, creamy milky aroma and thus widely-used in butter-flavoured foods. For example, in recent years butter-flavoured microwavable popcorn has become extremely popular.

There is an ongoing demand for the replacement of diacetyl by ingredients possessing similar taste characteristics when consumed but being less volatile thus minimising the flavour lost during processing and storage.

Surprisingly, inventors now found a new class of compounds which release diacetyl upon elevated temperature in the presence of moisture.

Accordingly the present invention refers in a first aspect to compounds of formula (I)

wherein n is selected from 0, 1 and 2; and

R ¹ is selected from hydrogen, methyl, ethyl, and propyl (e.g. n-propyl, iso-propyl).

The subject compounds are essentially tasteless but release diacetyl (A) and hydroxycarboxylic acid (B, such as lactic acid, 2-hydroxybutyric acid, and 2- hydroxyvaleric acid) upon elevated temperature in the presence of moisture as shown in Scheme 1. Lactic acid is commonly used as additive in food products. When used in

combination with diacetyl it enhances the creamy effect of the overall taste characteristics.

Scheme 1:

Accordingly, in another aspect there is provided a method of generating diacetyl, the method comprising, adding a compound of formula (I) as hereinabove defined, or a mixture thereof, to a food product and subsequently exposing the food product to elevated temperature in the presence of moisture.

In a further aspect there is provided a method of imparting a butter flavour to a food product, such a popcorn, the method comprising, adding a compound of formula (I) as defined hereinabove, or a mixture thereof, to a food product and subsequently exposing the food product to elevated temperature in the presence of moisture.

Still another embodiment provides a popcorn product produced by the aforementioned processes.

By "elevated temperature" as used herein is meant a temperature higher or equal to about 105 ⁰ C, preferably between about 175°C to about 205 ⁰ C, e.g. 204°C, which may be achieved for example by heating the food product by microwave radiation or by an external heat supplier such as an oven, heating mantle or coil, or flame.

By "moisture" as used herein is meant water in an amount from at least 5 weight %, e.g. between about 10 and about 30 weight % based on the food product before heating. This small amount is sufficient enough for releasing diacetyl from a compound of formula (I) when heated. Because almost all food products in its consumable form

comprise water the aforementioned ranges is thus not necessary to added further water.

For example, usually popcorn kernels have an internal moisture level of about 11 to about 16 weight %, e.g. a range of 14 - 15% by weight, which is sufficient enough for releasing diacetyl of a compound of formula (I) when heated.

When popcorn kernels are heated past the boiling point of water, the moisture in the kernel is turned into a superheated pressurized steam, contained within a moisture- proof hull. Under these conditions, the starch inside the kernels gelatinizes, softening and becoming pliable. The pressure continues to increase until the breaking point of the hull is reached. The hull ruptures rapidly, causing a sudden drop in pressure inside the kernel and a corresponding rapid expansion of the steam, which expands the starch and proteins of the endosperm into an airy foam. The expansion of the steam is sufficient enough to cause compounds of formula (I), applied to the outer hull of the popcorn kernels, to break down and thus releasing diacetyl.

For the manufacturing of popcorn, particularly microwave popcorn, the corn kernels may be sprayed with an oily or aqueous composition comprising a compound of formula (I) and optionally other flavourings. These flavourings may include salt and/or sugar and other natural and/or artificial flavour ingredients such as artificial butter, cheese flavour, pizza flavors, sweeteners, such as sucralose, savory flavors and other artificial or natural flavorings, such as cinnamon, caramel, apple and coffee, and spices. The composition is typically sprayed onto the corn kernels at room temperature or at a temperature slightly above room temperature, for examples at a temperature from about 15 to 6O ⁰ C. In the case of microwave popcorn, following spraying, the corn kernels are packed and sealed in a suitable container such as a bag until the time of use.

The oil may be any acceptable food oil, such as palm oil, palm kernel oil, cocoa oil, shea nut oil, partially hydrogenated or fully hydrogenated oils including vegetable oils, sunflower oil, safflower oil, rapeseed oil, cottonseed oil, maize oil, linseed oil, groundnut oil, or soybean oil. Other suitable oils include nut oils (such as almond, brazil nut, cashew, coconut, hazelnut, pecan, peanut, and walnut), olive oil, sesame oil, or flaxseed oil.

In addition the oily or aqueous composition may further comprise one or more ingredients or excipients conventionally used in conjunction with popcorn, for example antioxidant, food-grade colorants, and vitamins.

The unpopped popcorn products typically comprise from about 600 to about 900 ppm of a compound of formula (I), or a mixture thereof based on the total weight of the flavoured corn kernels.

In a further aspect there is provided a package comprising popcorn kernels and a flavouring composition comprising a compound of formula (I), or a mixture thereof, for heating in a microwave oven for producing flavoured popped popcorn. The package may take a variety of forms including flexible bags or tube arrangements. The package is preferably microwaveable for placing in a microwave oven.

The compounds of formula (I) may be prepared by reacting diacetyl with the appropriate hydroxycarboxylic acid in the presence of an acid, such as trimethylchlorosilane, under conditions known to the person skilled in the art.

As will be understood from the nature of the compounds of formula (I), they are not only suitable for flavouring popcorn, in particular microwave popcorn, but also suitable for flavouring of all kind of food products as long as the product will be heated before consumption, including but not limited to sauces, soups, desserts, cake mixes, bake goods, heat treated beverages, e.g. nutritional drinks, coated cereals and chips.

Products such as cereal and chips which do not contain water in its consumable form may be flavoured during processing by admixing an aqueous or oily flavouring composition comprising a compound of formula (I), or a mixture thereof, to the product before drying.

Depending on the solubility properties of the compound of formula (I) it may be either pre-solved in a food-grade solvent, such as ethanol, and subsequently further diluted in oil, such as miglyol, or directly admixed with natural and/or artificial flavour ingredients such as artificial butter, cheese flavour, pizza flavors, sweeteners, such as sucralose,

savory flavors and other artificial or natural flavorings, such as cinnamon, caramel, apple and coffee, and spices.

Thus, in a further aspect there is provided an oily or aqueous solution comprising a compound of formula (I) and at least one flavouring.

In still a further aspect there is provided a flavouring composition comprising a compound of formula (I) and at least one flavour ingredient.

The flavouring composition typically comprises from about 5 % wt/wt to about 20 % wt/wt of a compound of formula (I). However, these values are given only by way of example, since the experienced flavourist may also achieve effects or may create novel accords with lower or higher concentrations, e.g. up to about 40% wt/wt weight percent based on the flavouring composition.

The following list comprises examples of known flavour ingredients, which may be particular suitable combined with the compounds of the present invention:

- propionic acid, butyric acid, hexanoic acic, delta-docecalactone, and delta- decalactone, or mixtures thereof.

Further examples of flavour ingredients may be found e.g. in "Perfume and Flavor Material of Natural Origin", S. Arctander, Ed., Elizabeth, NJ. , 1960; in "Perfume and Flavor Chemicals", S. Arctander, Ed., Vol. I & II, Allured Publishing Corporation, Carol Stream, USA, 1994; in "Flavourings", E. Ziegler and H. Ziegler (ed.), Wiley-VCH

Weinheim, 1998, and "CTFA Cosmetic Ingredient Handbook", J. M. Nikitakis (ed.), 1 ^st Ed., The Cosmetic, Toiletry and Fragrance Association, Inc., Washington, 1988.

The invention is now further described with reference to the following non-limiting examples. These examples are for the purpose of illustration only and it is understood that variations and modifications can be made by one skilled in the art.

Example 1 : 2.2'.5.5'-tetramethvl-2,2'-bi(1 ,3-dioxolane)-4,4'-dione

Under nitrogen, trimethylchlorosilane (7.4 g, 68 mmol) was added to a solution of

diacetyl (6.9 g, 68 mmol) and lactic acid (6 g, 68 mmol) in 60 ml of hexane. The reaction was allowed to stir at room temperature for 16 hours. The crude product was neutralized with a sodium carbonate solution and extracted with MTBE. The extracts were washed with brine, dried over sodium sulfate and concentrated. The residue was 5 purified by silica gel column with MTBE/hexane (15:85) giving 4.5 g (28% yields) of a white solid product. Melting Point = 105 ⁰ C.

Taste description (200 ppm in ethanol): tasteless with a thinking of butter notes

10 MS (El): M/z 116, 115, 87, 56, 43 (100%).

¹ H NMR (CDCI ₃ , 300 MHz): δ 4.5 (m, 2H), 1.63 (m, 6H), 1.48 (m, 6H).

¹³ C NMR (CDCI ₃ , 300 MHz): δ 173.3, 172.6, 172.0, 110.2, 109.8, 108.3, 72.1, 71.6,

71.1, 21.8, 21.5, 20.6, 18.4, 18.2, 16.5.

15 Example 2: Popcorn

2,2',5,5'-Tetramethyl-2,2'-bi(1,3-dioxolane-4,4'-dione that was diluted to 9 weight % in ethanol and then further diluted to 9% in miglyol (i.e. the miglyol composition comprised 0.81 weight % of 2,2',5,5'-Tetramethyl-2,2'-bi(1,3-dioxolane-4,4'-dione ) was mixed with

20 popcorn kernels at 800 ppm in a popcorn bag. Together with a control popcorn bag, i.e. natural popcorn kernels, they were heated in separated microwave ovens for 1 minutes and 50 seconds. After popping, the popcorn admixed with 2,2',5,5'-tetramethyl-2,2'- bi(1,3-dioxolane-4,4'-dione emitted butter aroma, but the control did not. The butter was also tasted from the popcorn containing the diacetyl precursor, but it was not tasted

25 from the control.

The next comparison was with the popcorn kernels containing diacetyl at 300 ppm with kernels containing 2,2\5,5'-tetramethyl-2,2'-bi(1 ,3-dioxolane-4,4'-dione at 800 ppm (which is equal to about 300 ppm diacetyl). They were heated in separated microwave 30. ovens for 1 minutes and 50 seconds. The popcorn containing 2,2',5,5'-tetramethyl-2,2'- bi(1,3-dioxolane-4,4'-dione emitted the butter aroma at the lower intensity than the popcorn containing diacetyl. However, their tastes were indifferent.