SE446584B - PROCEDURE FOR AROMATIZATION OF SOLUBLE COFFEE POWDER - Google Patents

Description

446 584 2 roasted coffee aromas for soluble coffee such as spray or freeze-dried coffee.

At present, substantially all commercially soluble coffee is combined with coffee oil such as by spraying the soluble coffee before packaging with either a pure or an aroma-enriched coffee oil. In this way, the soluble coffee material acquires an aroma that is more similar to non-decaffeinated roasted and ground coffee. The addition of oil is usually accomplished by the well-known oil coating technique (as disclosed in U.S. Pat. No. 3,148,070) or by oil injection (according to U.S. Pat. No. 3,790,032).

Coffee oil with or without added aroma has been the preferred medium for aromatizing coffee material as such products can still be considered as pure coffee products; however, the technology developed for the production of coffee oil (cf. Sivetz, Coffee Processing Technology, vol. 2, Avi Publishing Company, 1963, pages Z1 to 30) such as solvent extraction or removal of coffee oil from roasted coffee is not particularly desirable because the manufacturer either solvent-containing roasted coffee or a drawn cake, both of which must either be further processed or discarded. The addition of oil to a coffee product has also proved difficult in that undesirable oil droplets may appear on the surface of the beverage produced from the oily product. Thus, it would be advantageous to develop processes for the production of coffee products which used all coffee or other vegetable materials which did not require the production or use of coffee oil or other glyceride materials. 446 584 Water-soluble particles of edible materials are obtained by drying aqueous solutions of vegetable materials such as coffee. These particles are prepared so that the particles have an average (base distribution in%, by weight) diameter which is below 200 microns (u), preferably below 150 μ, usually between about 50 μ and 150 μ and possesses a microporous structure containing micropores with a probable radius of less than 150 angstroms (Å), preferably less than about 110 Å, preferably less than 50 Å. A most probable radius of between 10 and 35 Å has been found to be most preferred for the invention. Although micropores less than about 15 Å have been considered desirable for the purposes of the present invention, they have not been readily available and appear to constitute a practically lower limit for the most likely radius parameter. A pore radius of less than about 3 Å is not desirable because such a small size would exclude molecules of aromatic compounds that one wishes to fix in the microporous structure.

The fine pore structure of the porous particles of the invention was determined by analyzing the adsorption-desorption isotherms of carbon dioxide gas by these particles at -78 ° C.

A standard all-glass volumetric gas adsorption apparatus was used according to procedures known to those skilled in the art of surface chemistry (Brunauer, S., "THE ADSORPTION OG GASES AND VAPORS", Volume 1, Princeton Univ. Press, 1945). Normally, the adsorption isotherms are first determined by measuring the amounts of CO 2. which is adsorbed at different but gradually increasing equilibrium pressures and then reducing the pressure to obtain the desorption branch of the isotherm.

The desorption isotherms are generally the result of ordinary multilayer adsorption and condensation in pores, in which case the Kelvin equation, which calculates the reduction of adsorbate (C02) vapor pressure depending on the concavity of the liquid concave convex can be used. In its simple form and assuming a complete wetting of the surface (zero contact angle), the pore radius (r) is obtained according to 446 584 r = -z§_y_ RT ln Pd / Po wherein 5 is the surface tension of liquid sorbate (CO volume, On is the pressure at the desorption branch of the isotherm and Po is the saturated vapor pressure (760 mm Hg for CO2 at -7800).

Kelvin * fl GëüiO fi en shows that there is a logarithmic relationship between the pore radius and the relative pressure (P¿ / Po). Narrower pores are filled at lower relative pressure, larger pores at higher pressure and the entire pore surface is filled at saturation pressure.

Further improvements to the Kelvin equation must be made to correct the gas absorption occurring simultaneously with the gas condensation (Barrett, EP, LG Joyner, PP Halenda; J. Amer. Chem. Soc. 73, 373 (1951). Calculations are therefore made to obtain the relative pressure and consequently the adsorbed gas volumes (v) corresponding to the selected pore radius. Indentations of êy_ (cmå / q) vs r (Å) give; pore- Ar (Ä) volume distribution curves. The shape of these distribution curves reflects the uniformity or distribution of the pores. As one skilled in the art will appreciate, the pore size distribution in a given porous material generally follows a bell-shaped curve distribution pattern and the term "most likely radius" refers to the radius corresponding to the top of the pore volume distribution curve.

The aqueous solutions used to prepare the dry particles are generally obtained by water extraction of a vegetable material such as roasted coffee.

Various kinds of techniques described below are available for the production of particles with the desired micropore structure.

Conventional spray drying produces dry particles that do not possess ndknqxmsünmtur. Conventional freeze drying produces particles in which the most probable pore radius is above 10,000 Å. Pores below 150 Å are required to trap volatile aromatic compounds such as those found in coffee 446 584 in the microporous structure of the dry the particles. The entrapment of the aromatic agents with the dry particles of the invention is believed to be a result of both adsorption and more significant capillary condensation (ie condensation of vapors in the pores). The aromatics are kept within the microporous structure without requiring any coating on the surface of the particles. However, a small percentage of these aromatics will be released as a result of the light partial pressure generated by the trapped aromatics. The mechanism of capillary condensation does not occur in pores of excessive size where coating of the particles is required to retain the aromatic substances.

The dry porous particles prepared according to the present invention, after being brought into contact with the desired aromatic substances, are used to provide headspace aromas for packaged low aromatic food products such as the above-mentioned soluble coffee or tea products. These particles are combined with the food product at the preferred target level of 0.1-2%, most preferably about 0.2-1%.

In general, the dry aromatized soluble particles of the invention will only be mixed with a dry, low-aroma powdered food product.

Several methods have been identified for producing dry soluble particles of edible material obtained from vegetable material solutions so that the resulting dry particles have a diameter below 200 Å and a porous structure in which the most probable pore radius is below 150 Å.

Spraying an aqueous solution, preferably with a content of less than 40% by weight, generally 25-35% by weight, in a cryogenic liquid with a temperature below -100 ° C, preferably liquid nitrogen and subsequent freeze-drying of the frozen particles into solutions gives dry microporous 446 584 a particles with a most probable pore radio of less than 50 Å.

The spray should give particles with an average particle size of less than 200 p in diameter so that the whole particle will freeze immediately as it is brought into contact with the cryogenic liquid. It is believed that instant freezing only produces extremely small ice crystals in the particles. Should the spray droplets exceed ZOO p in average diameter, the frozen particles, even at liquid nitrogen temperature, will only possess the desired extremely small ice crystals on the surface and not through the structure. Sublimation of these extremely small ice crystals seems to give the desired micropore structure according to the invention.

The use of a cryogenic liquid with a temperature above ~ 100 ° C has not been found to give a most probable pore radius of less than 150 Å regardless of the diameter of the spray drops.

Another way to prepare the dry micropore particles is to spray the aqueous solution in an anhydrous organic solvent such as 100% ethanol, which both dehydrates the extract and forms pores of soluble solids.

Soluble coffee particles prepared in this way have been found to possess a most likely pore radius of less than 50 Å. It is also possible to start with ground spray-dried particles such as soluble coffee and to boil these particles in an edible organic solvent such as ethanol, preferably after grinding, to etch the surface of the particles and give a desirable porous structure. It is again desirable to produce or use particles having an average diameter below 200 microns to provide a sufficient surface area for the solvent so that the etching provides a sufficient number of desirable micropores.

The microporous particles prepared according to the present invention can trap volatile aromatic compounds up to about 2% by weight. In reality, it is difficult to obtain aromatic substances in amounts above 1%. The capture of the aromatics in an amount less than about 0.1% by weight would require the addition of aromatized particles to the soluble food product in an amount of 446,584 of 5% or more. It is generally preferred to add the flavored particles in an amount of less than 2% by weight. Preferably, the aromatized particles of the invention will contain aromatics in an amount of 0.2% or more, generally about 0.5%.

The manner of contact between the porous particles and the aromatic substances to trap the aroma in the particles can be many and varied. The use of high pressure and / or low particle temperature can be used to maximize the uptake of aromas or to shorten the period of time required to achieve a desired level of aromatization; however, such conditions are not required. However, it is desirable to minimize the amount that comes into contact with the soluble porous particles both before, during and after the aromatization. Appropriate condensation, aging, sweeping and / or other separation techniques can be used to separate the moisture and the aromatic substances contained in aromatic gas streams, aroma frost or liquid aroma condensate. It may also be desirable to separate the aromatics from any carrier gas (eg CO 2 in which they are trapped).

Among the techniques used for adsorbing flavors on pore substrates are: (1) that both the porous particles and a condensed CO 2 flavor frost are well mixed placed in a Valves vessel, preferably above -4000 and that the CO 2 content of the frost is allowed to sublimate , (2) enclosing both the adsorbent and a condensed aroma frost in one or two connected pressure vessels and then raising the temperature of the frost-containing vessel so that the frost evaporates and giving an elevated pressure, (3) combining a highly concentrated aqueous aroma condensate with the porous particles in an amount where it does not excessively moisten the particles, (4) condensation of the aromatic substances on cooled porous particles, (5) placing a stream of low moisture aroma-bearing gas through a bed or column of porous particles. The aromatic substances to be used according to the invention can be derived from any of the many sources well known to those skilled in the art. Depending on the method of contact to be used, the flavoring agents may be present as a component of a gas, a liquid condensate or a condensed frost. Among the flavorings that can be used are coffee oil flavorings, which are described in U.S.P. no. 2947634, aromas obtained during roasting of green coffee as described in U.S.P. No. 2562 622, flavor obtained during grinding of roasted coffee as described in U.S.P. no. 3021218, redistilled volatile aroma obtained from roasted and ground coffee as described in U.S.P. no. 2562206, 3132947, 3244521, 3421901, 3532507 and 3615665 and vacuum distilled aroma obtained from roasted and ground coffee as described in U.S.P. no. 2680687 and 3035922. It is of course also possible to use volatile synthetic chemical compounds which duplicate or resemble the aromatic compounds naturally present in roasted coffee, fermented tea or other aromatic food products.

The flavoring agents absorbed on the microporous particles [according to the invention have been found to be stable for long periods of storage under inert conditions which normally exist in the packaging of soluble coffee products. These absorbed flavorings can provide the desired headspace flavor in packaged products and, if present in sufficient quantity, also provide desired flavor effects.

The invention is further illustrated by the following examples in which the temperatures refer to degrees Celsius.

Example 1

An aqueous coffee extract with a soluble solids content of 33% by weight is promoted by the regeneration of spray-dried solid coffee constituents. This extract was sprayed into an open vessel containing liquid nitrogen whereby the extract particles were immediately frozen and dispersed. The extract 446 584 was sprayed using a two-liquid, glass-clogging nozzle (a chromatographic nozzle from SGA Scientific Inc.) using air as a pressure generating liquid.

The liquid nitrogen and particle mixture was poured into freeze-drying vessels and the liquid nitrogen was allowed to boil and left a flat bed of frozen particles with a thickness of approximately 1.6-3.2 mm. The vessels were placed in a freeze dryer and subjected to a vacuum of 10 microns Hg and a plate temperature of 5000 for 18 hours. The freeze-dryer vacuum was broken with dry CO 2 and the dry particles with a moisture content below about 1.5% were removed from the freeze-dryer and kept out of contact with moisture. The dry particles were found to have a microporous structure containing pores with a most likely radius of about 24-28 Å and a sieve analysis as follows: Standard U.S. Pat. mesh ÉF Weight percentage of so 7, s of ioo 15.0 at zoo 67, 3 containers 10.2 The dry particles were subsequently cooled in dry ice under a dry atmosphere and mixed with coffee grinding gas frost with a moisture content between 10 and 15% by weight in a weight ratio of 0 , 2 parts frost per particle. The mixture was transferred to a chilled container with pore ventilation and the container was stored at -1.8 ° C overnight during which CO 2 evolved. The cooled particles with a moisture content of less than 6% by weight were then packaged in glass containers with uncoated aggregated spray-dried solid coffee ingredients in an amount of 0.75% by weight of the spray-dried solids. The resulting containers were stored at 35.0 ° C for 8 weeks. When first opened and during a standard 7 day cycle of use, a pleasant headspace aroma was obtained which was judged to be at least as good as the headspace aroma in containers of comparatively aged flavored agglomerated spray dried coffee coated with grinding gas enriched coffee oil. This oily white sample was prepared according to U.S.P. (U.S. Patent Application 643.4S2, filed December 26, 1975) using an amount of grinding gas frosting per unit weight of soluble product, comparable to that used in the sample of the invention.

Example 2. 100 ml of coffee extract containing 50% by weight of soluble solids is sprayed by means of a glass chromatography nozzle into a large container containing 3.8 l of pure ethanol.

The ethanol was at room temperature and stirred during the spraying process. Then the soluble coffee particles were filtered from the ethanol and these particles were placed in a vacuum and about 90 ° C) overnight to remove residual ethanol. The obtained particles were found to have a microporous structure in which the most likely pore radius was 33 Å. The particles were kept out of contact with moisture and brought into contact with grinding gas frost in an amount of 2 parts by weight of frost to 1 part by weight of particles in a Parr bomb heated to about 200. The resulting aromatized particles were combined and packaged with uncoated and non-aromatized spray dried coffee agglomerates in an amount of about 0.5% by weight. The can aroma of this sample after 1 week of storage at room temperature was found to be comparable to week-old grinding gas-enriched oil-coated agglomerate.

Example 3.

Agglomerated spray-dried coffee was ground and the particles passing through a 50 mesh (U.S. standard sieve) sieve were separated and 150 g of these particles were added to 2,000 ml of 100% ethanol. This mixture was boiled for 24 hours in a steam jacketed vessel equipped with an overhead reflux condenser and a stir bar. Then the coffee particles were filtered from the ethanol and dried in vacuo for 24 hours at 800 and a vacuum of about 630 mm Hg. The dry particles weighed a total of about 90 g (about 60 g of solid coffee constituents had dissolved by the ethanol) and had a porous structure in which the most likely pore radius was about 102 Å. Two parts (by weight) of these particles were brought in contact with 1 part of grinding gas frost in the manner 446 584 ll given in Example 1 and the aromatized particles obtained were packed with agglomerated spray-dried coffee in an amount of about 0.5% by weight. The can aroma for this sample after 1 week of storage at room temperature was found to be comparable to week-old grinding gas-enriched oil-coated agglomerate.

As stated above, can aromas have been provided in commercially available soluble coffee products by means of an oil coating of a flavoring glyceride (eg coffee oil) on the soluble powder. It has also been proposed to absorb coffee aroma ingredients on oil-coated soluble coffee and this technique is described in U.S.P. no. 3823241. However, in the past it has not been thought possible to absorb or adsorb large amounts of aromatic substances directly on soluble coffee constituents so that the aromatic substances would be retained. U.S. Pat. No. 3,823,241 discloses the criticality of the oil so that upon successive opening of the soluble coffee package (ie, in the cycle of use) the consumer continues to perceive a can aroma. This is in fact the situation for the conventional spray-dried, foam-dried and freeze-dried products described in the aforementioned U.S. patent.

However, there is not the same deficiency in porous soluble coffee particles with a probable pore radius of less than 150 Å.

As stated above, conventional spray-dried coffee does not have a microporous structure, while in conventional freeze-dried coffee the most likely pore radius is in the order of 1000 Å. V It appears from the following table, which compares the rate at which aromas are released from aromatized particles of soluble coffee from Examples 1 to 3 and aromatized particles of spray dried coffee reduced to a comparable particle size by grinding with dry ice. The aroma release properties of the various flavored soluble coffee substrates can be predicted by observing the amount of organic carbon (micrograms) swept from the substrate as a function of the sweeping time. The carbon values were obtained by sweeping a known coffee 0,5 äük fi (0.5 g) with a stream of nitrogen (30 cm 3 / minute) at 446 584 12 300 for 2,000 seconds. The volatile constituents that were removed were counted every 200 seconds. The table shows the rate (expressed as% of the total amount) aroma released (cumulative) as a function of the sweep time, the aroma released for 2,000 seconds corresponds to 100%.

Table 1.

Sweep time% released aroma (pg carbon / g coffee) in respective sweep time x 100 (second) (pg ker / g coffee) in zooo seconds Example l Example 2 Example 3 Control 200 51 36 55 69 400 74 56 74 87 600 82 67 82 94 800 88 76 87 96 1000 '92 82 91 97 1200 94 87 93 98 1400 97 91 96 98 1600 98 94 97 99 1800 99 97 _ 98 99 2000 100 100 100 100 Table 1 shows that the spray-dried control material, which does not possess a microporous structure emits the aroma most rapidly and would therefore not be suitable for providing kmrkæxml during use.

Example 4.

A series of porous particles were made according to the following procedure: 1) spray-dried agglomerated coffee powder was converted into 33% soluble solids and this extract was sprayed in liquid nitrogen using a glass chromatography nozzle. The resulting frozen particles were lyophilized at 0.01 mm Hg and 25 ° C for 16 hours. Particles over 50 mesh U.S. standard sight) was removed. 2) Same as in 1 but the powder was converted to 50 8 soluble solids. 3) Spray-dried agglomerated coffee powder was converted to 33% soluble solids and sprayed in 100% ethanol. The resulting particles were collected and placed in a vacuum dryer at 100 ° and 0.9 kg / cm 2 vacuum for 16 hours. 4) 300 g of the spray-dried agglomerate were ground and boiled in 2000 ml of 100% ethanol. The resulting particles were dried at about 900 and 0.9 kg / cm 2 vacuum for 16 hours. A portion of each of the four samples was flavored by contact with grinding gas frost in an amount (by weight) of 0.4 parts of frost per part of substrate. Contact was made by mixing the frost and the substrate together in a vessel cooled with dry ice. The aroma-bearing particles were placed in separate cooled tanks equipped with a ventilation device and placed in a freezer at -17.80 overnight. Thereafter, 0.2 g of each aromatized sample was placed in a 250 cm 3 stoppered, but the flask was then evaluated using standard flask and 1 cm 3 of the resulting main space mezzanine gas chromatography technique. A proportion of each of the flavoring particles was subjected to the nitrogen scavenging test identified above (2000 seconds at 300 to assess the level of aromatic substances contained therein. This nitrogen scrubbing test is also performed with non-flavored samples. The results of these assessments are given in table 2.

Table 2.

Sample ## Porosity Released aroma Main space (Å) (4 pg carbon / (GC calculation g coffee) in millions) l 23-28 28.5 1,375 l-aromatized "1790 2 over l4O 6.75 2-aromatized" 458 0.304 3 Table 2 shows the amount of aroma which can be absorbed by the porous particles according to the invention in comparison with the amount of aroma present in the non-aromatized particles as well as the ability of these particles to give a main space aroma comparable in quantity to the main space aroma produced by grinding gas-enriched coffee oil prepared according to the above-mentioned US patent application 643,432.

Claims (3)

1. 446 584 IS PATENT REQUIREMENTS 1. Soluble coffee powder, which is added with aromatized microporous particles in an amount of 0.1-2.0%, calculated on the weight of the powder, which particles are dry, water-soluble particles of roasted coffee material with a microporous structure, characterized in that the top of the generally bell-shaped pore volume distribution curve of the microporous structure is at a pore radius between 3 Å and 150 Å, that said particles have an average diameter of less than 200 μm, and that said particles contain volatile, aromatic compounds in the microporous structure in an amount of 0.1-2.0%, calculated on the weight of the particles, and that the added amount of aromatized microporous particles is effective to give a pleasant main space aroma, when the soluble coffee powder packaged in a sealed container. 2. A product according to claim 1, characterized in that the aromatized microporous particles have an average diameter of less than 150 μm. A method of providing a main compartment aroma, initially and in use, for a packaged soluble coffee powder, characterized by the steps of: (a) preparing particles of dry, water-soluble roasted coffee material having a microporous structure, the top of the generally bell-shaped pore volume distribution curve for the microporous structure is at a pore radius between 3 Å and 150 Å and said particles have an average diameter of less than 200 μm; (b) contacting the porous particles of step (a) with volatile aromatic compounds so that the aromatic compounds are trapped in the microporous structure of the particles in an amount of 0.1-2.0% by weight; (c) the aromatized particles are mixed with a low aroma intensity soluble coffee powder in an amount of 0.1-2.0% by weight of the powder, which amount is effective to give a main space aroma initially and in use, when the 446 584 lb soluble coffee powder is packaged in a sealed container; (d) the mixture according to step (c) is packaged in a sealed container.