GB2090726A - Method and apparatus for reducing oxidation and evaporation of coffee - Google Patents

Abstract

The pot life of a quantity of coffee may be extended by maintaining super- atmospheric pressure and/or substantial temperature differential between the surface of and the bottom of coffee within a pour type decanter and dispensing coffee from the bottom region of the decanter. In Figure 1, the decanter consists of a flask (12) provided with a tightly fitted cover (16) that frictionally engages the upper rim (14) of the flask. The cover (16) supports a pouring spout or tube (24) the lower end of which is adjacent the base of the flask (12) and the upper end of which extends above the cover (16). Filling means (28,30) are provided in the cover (16) and a vent (34) is provided to prevent internal vacuum and enable the establishment of super- atmospheric pressure within the closed flask. In the porcelain decanter of Figure 7 the pouring spout is external of the flask with its lower end opening through the sidewall (140). The cover may be modified to provide condensing means through which the flask may be filled. <IMAGE>

Description

SPECIFICATION Method and apparatus for reducing oxidation and evaporation of coffee The deterioration of coffee, i.e. the loss of a "fresh" or palatable flavor and aroma, is primarily caused by oxidation and evaporation. In a conventional 8-12 cup coffee decanter, deterioration is generally so complete within one or two hours, depending on the rate of consumption, as to render the remaining coffee undrinkable.

The role of oxidation, alone, in deteriorating coffee flavor is obvious to anyone who drinks coffee from a vacuum flask or container. When the container is first opened, whether after one or several hours, the coffee tastes perfectly fresh. If the container is then resealed with a lesser amount of coffee remaining therein, such as a half cup, it rapidly deteriorates as evidenced by the poor taste when it is consumed, say, one hour later. There was obviously no significant evaporation from the sealed flask or container but fresh air was inevitably admitted at the time the first cup was poured.

The deterioration due to evaporation is even more obvious as the coffee solution is concentrated by evaporation.

The concept of extending the "pot life" of coffee, i.e. that time period during which it retains the flavor and aroma of freshly brewed coffee, by substantially eliminating its exposure to atmosphere while yet retaining the ability to pour coffee in conventional fashion was described in United States Patent 3,974,758. In a pour type coffee decanter, the inventive concept of that Patent involves sealing the main body of contained coffee with respect to atmosphere. The top of the decanter is sealed by a movable follower, such as a bellows or bag, and that coffee contained within the lower end of a small diameter pour spout opening into the coffee decanter adjacent the bottom thereof serves as a liquid seal between atmosphere and the main body of the decanter contained coffee.

The result is that the only oxidation that can occur takes place at the upper coffee level in the pour spout. By keeping the cross section of the pour spout sufficiently small, that quantity of coffee that is oxidized and subsequently finds its way through the liquid seal to the main reservoir of contained coffee is negligible over the first 4-8 hours depending upon the cross section of the pour spout. Similarly, the only loss to atmosphere that can occur by way of evaporation is at the small upper coffee level in the pour spout since a state of equilibrium inherently exists across a gas/vaporizable liquid interface in a sealed container.

In other words, the previously disclosed concept involves dispensing from the bottom of the decanter while keeping the top of the decanter sealed with a movable follower maintaining atmospheric pressure on the coffee so that it can be poured without creating a vacuum lock.

The present invention seeks to eliminate the need for a movable follower while yet reducing the oxidation and evaporation of a quantity of decanter contained coffee to thereby extend its "pot life".

According to the invention, there is provided a container for coffee having an open upper end and which in use contains a quantity of hot coffee the vapor pressure of which exceeds atmospheric pressure; a top assembly closing the upper end of said receptacle; a pour spout extending from adjacent the bottom of said receptacle to the upper end thereof for dispensing coffee therethrough from the bottom of said receptacle; and means including said top assembly for venting said receptacle and maintaining superatmospheric pressure therein in the presence of a quantity of said hot coffee.

The invention also provides a method of reducing oxidation and evaporation of coffee in a pour type receptacle, comprising; introducing a quantity of coffee into a coffee receptacle; maintaining said quantity of coffee at a temperature above 1 60 F; maintaining superatmospheric pressure within said receptacle; and dispensing coffee from immediately adjacent the bottom of said quantity of coffee.

The purposes of the invention are twofoid; 1).To introduce a "restricted vent means" concept to produce, in a decanter having no moving parts, a pot life extension approaching that of the earlier concept employing a totally sealed decanter; and 2).To introduce a "temperature differential" concept for extending the pot life of coffee which requires no special top assembly as for sealing or providing a restricted vent means; indeed, the decanter top may include the large central opening characteristic of conventional automatic drip coffee maker decanters.

The purposes are stated separately because in high usage situations where, for example, a full decanter of coffee is typically consumed within one or two hours, the "temperature differential" concept will be quite adequate to keep the coffee fresh whereas, over longer consumption periods the "restricted vent means" concept will extend the pot life for up to four to five hours. When the two concepts are combined in a single decanter, as also herein disclosed, the pot life extension may reach six to eight hours approaching that of the previously described sealed decanter.

The common denominator and critical feature of both concepts is that of dispensing coffee from immediately adjacent the bottom of the decanter.

In the adaptation of the "restricted vent means" concept to a conventional blown, borosilicate decanter which is not formed with a pour spout, the object of substantially sealing the main body of containd coffee with respect to atmosphere is obtained by a liquid seal comprising the liquid column in a small diameter pour spout extending to the bottom of the decanter so that one, in effect, pours from the bottom of the decanter.However, the pour spout extends upwardly from th bottom of the decanter within the surrounding confines of the peripheral pot wall to emerge through a top assembly closing the open upper end of the decanten If the open top of the decanter were totally sealed in the absence of a movable follower member to keep atmospheric pressure on the coffee, coffee could not be dispensed through the pour spout because ofthevacuum lockthatwould occur. The need for a movable follower may be eliminated and coffee readily dispensed while yet retaining substantially all the advantages of a totally sealed decanter by providing vent means of such small dimension that the vapor pressure of a quantity of contained coffee within the decanter exceeds atmospheric pressure.The result is a vapor seal, across the vent means, that precludes the ingress of air at all times except when coffee is actually being dispensed through the pour spout. The volume of entry air that occurs during pouring is, of course, negligible as compared with that volume which enters a conventional open pot over a period of from one to several hours. Stated differently, the oxidation effected by that minimal air indrawn during pouring produces no significant deteriorating effect over a period of several hours.

Aconcomitant, and significant, consequence of the restricted vent means is greatly reduced evaporation as compared with a conventional decanter from which the vapor may freely escape.

Thus, where vapor may freely escape, equilibrium across the gas/liquid interface is never attained and evaporation may proceed to completion. Conversely, in a closed system, partial pressures of the coffee vapor will increase until a state of equilibrium exists at which time for every molecule escaping across the liquid/gas interface in gaseous form another is returning from the gaseous to the liquid from at which point no further liquid volume loss to evaporation occurs. The latter is what occurs in the process described in United States Patent No.3974758 where the space above the coffee in the decanter is totally sealed.

An analogous result can be achieved by the restricted vent means herein disclosed which, in effect imposes a back pressure on the contained gaseous phase so that equilibrium is approached with the result that percentage return from the gaseous to liquid phase approaches that of escape from liquid to gaseous. The result, over a period of up to 6-8 hours, depending on the rate of depletion by dispensing, is negligible coffee volme loss to evaporation. In actual tests conducted with a six cup volume in a twelve cup decanter with the coffee maintained at 1750F and a single 1/16" diameter vent hole; loss to evaporation was less than one-third cup over a five hour period as contrasted with a two and one-half cup loss to evaporation from a conventional decanter.It will be obvious that the smaller the vent means the closer the approach to equilibrium and the lesser volume loss to evaporation.

In summary, concerning the vent means which for the present explanation will be assumed as a single pin hole in an otherwise sealed top of a coffee decanter through which a pour spout extends to near the bottom of the receptacle; the vent means is necessary to permit pouring of the coffee, in the absence of any movable parts, without developing a vapour lock. Regarding its role in reducing oxidation, the vent means must be of sufficiently small cumula tive area to produce a back, or superatmospheric, pressure within the decanter to prevent ingress of air by a vapor seal across the vent means when the decanter is in the upright, or non-pouring, position.

The role of the restricted vent means in reducing volume loss through evaporation is that of causing the partial pressures across the gas/liquid interface to approach equilibrium.

Since the overall purpose of the present invention is to ensure that the entire contents of a coffee decanter may be consumed without having to discard the last few cups because they have deteriorated to an unpalatable state; the importance of having a small diameter pour spout which extends to substantially the bottom of the receptacle and the lower end of which remains sumberged at all times as the coffee level is depleted may be appreciated.

Thus, by the time the coffee level has been substantially depleted, as for example to the two or three cup lines both oxidation and evaporation will, if permitted, play a far greater deteriorating role that when a full decanter of coffee is initially made. First, the smaller coffee volume will be at a higher temperature than the original filled decanter (assuming a standard, automatic drip coffee maker heating means to be used) and as with most other chemical reactions, oxidation is accelerated by increased temperatures as is the rate of evaporation. Secondly, deterioration due to oxidation proceeds more rapidly because of the proportionally greater surface area exposure in a small volume while even an equal rate of evaporation produces a far greater proportional concentration in a small, as compared with a large, volume of liquid.If the lower end of the pour spout does not remain submerged as the coffee level is depleted the liquid seal is broken, air reaches the remaining coffee to oxidize the same and the approach to equilibrium across the liquid/gas interface is destroyed allowing evaporation to proceed toward completion. This is why many conventional coffee pots of the electric or stove top percolator type which have outside pour spouts are not suitable for use with the present invention. In all cases they have at least a portion of the pour spout opening into the pot at a level well above the bottom of the pot and as soon as this upper level of the pour spout opening into the pot is reached by the declining coffee level the remainder of the coffee is quickly deteriorated by oxidation and evaporation.

Accordingly, the entirety of the lower open end of the pour spout must be positioned so that it remains substantially completely submerged at all times, with the liquid seal intact, until subsequently all the coffee is dispensed, else the primary advantage of retaining the palatability of the remaining coffee is lost. In actual practice, with various 8-12 cup coffee decanters it is more desirable to ensure that the liquid seal remains intact, if possible, until the next to last cup is dispensed ieaving only one cup subject to the deteriorating effects of oxidation and evaporation. In actual practice it is found that this last cup is usually consumed before it is substantially deterio rated. The foregoing translates into a necessary positionment of the lower open end of the pour spout at such a height above the bottom of the decanter that the entire lower open end of the pour spout remains completely submerged at remaining coffee levels falling generally within the range of 1/6 to 1/4 the height of a full decanter fill level of an 8-12 cup decanter. The range is stated thus to take into account various pot capacities and configurations though it will be apparent that the lower end of the spout should be as low as feasible.

While the top assembly and the decanter wall above the coffee level inherently act as a condenser, it is possible to further reduce even that small vapor loss to atmosphere through the vent means by providing additional surface area on the top assembly, in essence a condenser section.

It is the concept of combining a pour spout and vented top assembly, which may or may not include a condenser section, as an integral, unit handled structure for a conventional coffee decanter that is one important aspect of the invention.

If the top assembly is to be placed on a decanter after it is filled with coffee then the vent means need involve only a single vent opening whereas if the top is to be placed on the decanter prior to its placement under a drip coffee maker to receive freshly brewed coffee through a central "vent means", then a second vent opening must be provided to allow escape of displaced air as the decanter is filled.

Alternatively, the decanter may be filled through a large central opening in the top assembly, as is conventional, with the same being subsequently closed by a slide valve or the like containing the restricted vent means. It is not the number or the spacing of the vent openings that is critical, rather it is their cumulative area; i.e. their cumulative area must be sufficiently small as to maintain superatmospheric pressure within the decanter when it contains a quantity of hot coffee above 160"F, for example. Indeed, specific holes need not be formed in the top assembly if so interfitted with the open top of the decanter that vent air can be admitted while precluding the outflow of coffee as the decanter is tilted to "pour from the bottom". Exemplary of the latter would be a screw cap substantially, but not totally, sealed with respect to atmosphere.

The fact of the superatmospheric maintenance within a glass decanter is readily discernible when the pour spour is made of glass or a transparent synthetic plastics material since the coffee level, within the pour spout, may be seen to fluctuate at levels at and above the level of the main body of contained coffee.

In summary, a quantity of hot coffee in a coffee decanter having a small diameter pour spout extending upwardly from the bottom through the open top of the decanter is substantially sealed with respect to atmosphere by a top assembly containing vent means of such cumulative dimension that the vapor pressure of the coffee exceeds atmospheric. Accordingly, except at that moment when coffee is being poured the quantity of coffee is sealed from atmosphere by a liquid seal within the pour spout and a vapor seal across the vent means thus substantially reducing oxidation. Evaporation is substantially eliminated as the partial pressure across the liquid/gas interface approach equilibrium in the substantially sealed decanter.Although seemingly simple in retrospect, one of the greater advantages of the present invention from the standpoint of consumer acceptance is that its objectives are achieved in a unit handled construction employing no moving parts and imposing no constraints on conventional methods of coffee service.

The primary coffee deteriorants, oxidation and evaporation, can only take place at the surface of the coffee. The rate of both oxidation and evaporation are a direct function of temperature. Accordingly, pot life extension based on the "temperature differential" concept involves maintaining a coffee surface level temperature which is less than the drinking temperature maintained at the bottom of the decanter from which the coffee is dispensed.

The temperature differential is maintained, in a bottom heated decanter, by forming at least the upper portion of the decanter wall containment and pour spout from a material exhibiting relatively poor thermal conductivity such as a thick walled ceramic (glass or porcelain) or synthetic plastics material.

Although convective flow within a bottom heated, contained liquid volume would normally tend to maintain an equal temperature throughout the liquid volume, this tendency can be ameliorated to produce a significant temperature differential between the top and bottom ofthe contained liquid by constructing the containing decanter of a material having low thermal conductivity. This for the reason that the upper portion of the decanter wall will be primarily heated by conduction from the contained liquid whose maximum temperature will typically fall within the range of 160"F-175"F as opposed to also being significantly heated by conduction through the decanter wall from the 375"F heat source on which the decanter sits as is the case with a metal decanter and, to a slightly lesser extent, with a short, thin walled, blow molded borosilicate decanter.The result is that in the case of a coffee decanter constructed from a material of relatively low thermal conductivity, such as porcelain orthickwalled glass for example, the upper decanter wall portion is cooler than is the lower wall portion and decanter bottom sitting directly on the heat source. This translates into a 5"F-15"F temperature differential between the upper coffee level within the decanter and the bottom of the coffee volume from which the coffee is poured.

The reduced surface temperature, as contrasts with the higher "drinking temperature" maintained at the bottom of the decanter from which coffee is dispensed, results in a significant decrease in both oxidation and evaporation as will be apparent from the exponential nature of the vapor pressure curve for water across the temperature range in question.

The desired temperature for decanter contained coffee is generally considered to be 175"F. Coffee maintained at this temperature exhibits a vapor pressure of approximately 335mm Hg as contrasted with a vapor pressure of approximately 230mm Hg at 1600F. Since evaporation can only take place from the liquid surface it will be apparent that the coffee to be consumed, which is poured from the bottom of the decanter, may be kept at a desired drinking temperature of 175"F while the upper surface level thereof is at a substantially lower temperature exerting a far less vapor pressure resulting in a dramatic decrease in evaporative loss to atmos phere.In the specific example just given, the vapor pressure in a conventional decanter containing coffee at 175 F would be over 50% greater than the vapor pressure of coffee maintained in accordance with the "temperature differential" concept where the differential is 1 5"F between the top and bottom of the decanter.

Since oxidation, too, can only take place at the liquid surface and since, as with most chemical reactions, the rate of oxidation is a direct function of temperature it will be clear that oxidation is similarly reduced.

The precise magnitude of the temperature differential can be controlled, inter alia, by the height and wall thickness of the decanter. A specific form of decanter is of porcelain construction having, for the most part, a wall thickness of 114" which is locally thickened adjacent the pour spout, at the handle attachment and at the base which rests on the warming burner. Test data was compiled using a similarly configured porcelain decanter having a 60 oz. capacity, a maximum base diameter of 5" and a fill level height of 7".The decanter was initially filled with coffee from an automatic drip coffee maker delivering coffee at 175"F. The burner control was set to provide a maximum burner surface temperature of 375"F and to maintain the temperature of the coffee immediately adjacent the bottom of the decanter at 175"F. The temperature at the upper coffee level within the decanter subsequently stabiiized at 165"F and the upper coffee level within the small diameter pour spout at 1 60"F. The latter is readily explainable on the basis of necessarily reduced convective flow within the relatively long, small diameter pour spout construction which is further removed from conductive heating both by the decanter contained coffee and the burner.In the test decanter, a pour spout having a circular cross section measuring 3/8" in diameter was employed.

The additional significance ofthe greatly reduced temperature at the coffee surface in the pour spout will be later described in conjection with the combination of the "temperature differential" and "vent means" concepts.

The significance of the 10 F differential between the top and bottom of the contained coffee is obvious from the nature of the vapor pressure curve across this temperature range as already described.

When employing a top assembly of more or less conventional design and having a large central opening from which vapor may freely escape, the pot life of coffee maintained in accordance with the example just given is approximately doubled depending upon the rate of depletion by consumption.

A dramatic increase in pot life is achieved when the "restricted vent means" concept is combined with the "temperature differential" concept just described. In that instance, evaporative loss to atmosphere and oxidation occurring from and at the large coffee surface level within the decanter are sharply limited by the aforesaid approach to equilibrium and vapor seal, respectively. Both of these deteriorants are even further limited by the lower surface temperatures within the decanter when the same is constructed of a poor thermal conductor.

The most significant aspect, however, ofthe combination of these two concepts relates to the upper coffee level within the pour spout. When employing the "restricted vent means" concept, the main reservoir of contained coffee is protected against oxidation and evaporation with only the small diameter pour spout presenting a coffee surface where oxidation and evaporation are unimpaired. The fact that this surface area exposure is quite small so that the deteriorating effects are so limited as to be considered negligible over a time span of several hours is the basis for the success of the "restricted vent means" concept. Nevertheless, deterioration does occur at this surface albeit to a negligible extent as compared with a conventional, fully vented decanter.Now, even that limited deterioration taking place within the pour spout may be sharply reduced in accordance with the "temperature differential" concept herein described. Thus, with reference to the vapor pressure curve, it will be seen that the temperature differential (15"F in the test case described) between the upper pour spout coffee level and the bottom of the decanter from which the coffee is dispensed will produce a significant increase in pot life even beyond that achieved by the "restricted vent means" concept, alone.

Because of the small size of the pour spout, the temperature differential just described (175"F at the bottom of the decanter and 160"F at the upper coffee level within the pour spout) does not result in a significant decrease in delivered coffee temperature.

In test situations, pouring into a cup at room temperature, delivered cup temperatures measured, consistently, at 164"F + 1"F as opposed to the generally accepted cup temperature of 165 F.

As would be suspected from the foregoing, there is no significant temperature differential between the upper and lower portions of a quantity of coffee contained in a conventional, thin walled, borosilicate decanter, this also holds true for the upper coffee level within the internal pour spout. The latter is explainable on the basis that the small diameter pour spout and its small volume of contained liquid quickly reaches temperature equilibrium with the totally surrounding liquid as contrasted with an external pour spout which is relatively isolated from conductive heating by the contained liquid.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a vertical section, with some parts shown by phantom lines, of a blown, borosilicate coffee decanter incorporating the "restricted vent means" concept and employing an internal pour spout; Figure 2 is a fragmentary, top plan view of Figure 1; Figure 3 is a vertical section, with some parts in elevation, of a modified form of the embodiment shown in Figure 1; Figure 4 is a top plan view of Figure 3; Figure 5 is a vertical section of a porcelain coffee decanter adapted to maintain a temperature differential between the surface of a quantity of contained coffee and the bottom contents thereof; Figure 6 is a top plan view of Figure 5;; Figure 7 is a vertical section of the decanter of Figure 5 fitted with an alternate top assembly for maintaining superatmospheric pressure on the contained coffee; Figure 8 is a top plan view of Figure 7; and Figure 9 is a graph of the vapor pressure curve of water.

In Figures 1 and 2 is illustrated a coffee decanter 10 having an imperforate peripheral wall 12 of thin, borosilicate glass or the like whose open, upper end terminates in a circular beaded lip 14.

A plastics top assembly 16 includes spaced inner and outer circumferential flanges 18,20 defining a downwardly directed locking ring 22 adapted to engage the beaded lip 14 by a snap fit. An integrally formed pour spout 24 extends from adjacent the bottom of decanter 10 to the upper surface of top assembly 16 and includes reinforcing ribs 26. A central fill opening 28 in top assembly 16 is adapted to be selectively closed by a slide valve 30 supported by guide brackets 32 integrally formed with the top assembly. Slide valve 30 is formed with a small vent opening 34 to permit dispensing of coffee through pour spout 24 when valve 30 is closed.Top assembly 16 is preferably formed by injection molding from a plastics such as polysulphone or polycarbonate since the coffee temperature range with which the lower end of the pour spout will be in extended contact will vary from above 1 60"F up to about 1 90"F because the various warming burners with which the decanter will be used vary significantly in their calibrations. The desired temperature range closely brackets 1 75"F to produce a desired cup temperature of about 165 F.

Locking ring 22 may be interrupted if necessaryto interfit with the upper end 38 of handle assembly 40 if it is formed to overlie a portion of the upper beaded lip 14 immediately adjacent the handle so long as the interfitting relationship is substantially tight. It will be recalled that it is immaterial whether such as interruption in snap ring 22 (not shown) makes a sealing fit on either side of the upper end 38 of the handle assembly since it is the cumulative vent area that is important.Thus if a perfect seal is not established on either side of the handle assembly, the unsealed portion is nevertheless very small so that its "vent" area taken with the vent area of central vent opening 34 still constitutes "restricted vent means" which will maintain superatmospheric pressure in the receptacle in the presence of a quantity of coffee maintained above 160 F. It is important that the seal on the pour side of the pot be intact so that coffee does not "leak" over the lip when dispensing through the pour spout.

The handle assembly 40 and the method of attachment of its steel band 42 are entirely conventional and play no contributing role to the present invention beyond the fact that some form of handle assembly is required.

In operation of the embodiment shown in Figures 1 and 2; top assembly 16 is interfitted with decanter 10 and slide valve 30 is placed in the open position as shown in Figure 2. The decanter is then placed beneath an automatic drip coffee maker and freshly brewed coffee flows through central fill opening 28.

When the decanter is filled, slide valve 30 is moved to the closed position. With a conventional warming burner maintaining coffee temperature at approximately 175"F the coffee vapor above the coffee level finds itself in a substantially closed system by virtue of the liquid seal blocking pour spout 24 and the pin hole vent 34 allowing substantially less vapor loss to atmosphere than is built up by vaporization across the liquid/gas interface. The result is the production of a superatmospheric condition within the decanter blocking air entry through the vent means and production of an approach to equilibrium across the liquid/gas interface substantially eliminating evaporative loss to atmosphere.The oxidizing effects of that relatively negligible volume of air indrawn through the vent means produces little deterioration by oxidation over a 4-6 hour period depending upon the rate of depletion by consumption.

Instead of employing a central fill opening a slide valve; the upper surface of top assembly 16 may be imperforate except for a vent opening. In such event the top assembly would be applied after the decanter is filled.

The embodiment shown in Figures 3 and 4 illustrate an application of the invention to a different style coffee decanter and employs a top assembly of increased surface area and wherein the vent means also function as a fill opening.

In Figure 3 is illustrated a thin glass coffee decanter 44 whose open, upper end includes a cylindrical neck opening 46.

A top assembly 48, formed from a deformable material such as plastic or the like, includes a cylindrical skirt 50 sized to fit neck opening 46 and is sealed with respect thereto by deformable ring seals 52, 54 respectively engaging the upper and lower edges of the cylindrical neck opening. The top assembly includes a convoluted condenser section 56 merging centrally with a well 58 whose lowermost portion is formed with a combined drip and vent opening 60. An additional vent opening 62 is formed at a location outside the well on a side remote from the pour side of the decanter. A small-diameter pour spout 64 extends from adjacent the bottom of decanter 44 to the upper surface of top assembly 48.Pour spout 64 may have typically an internal diameter of 3/8" and is formed integrally with top assembly 48, for example by blow molding or the like, or it may be separately formed and secured to the top assembly by a secondary operation. In either event, top assembly 48 which includes the condenser section 56 and pour spout 64 is a unit handled assembly which can be applied to the neck opening 46 of a conventionally formed decanter.

When used with an automatic drip coffee maker, top assembly 48 may be placed on decanter 44 before the coffee is brewed. The freshly brewed coffee then flows into well 58 and through drip opening 60 into the decanter. Vent hole 62 allows escape of displaced air as the decanter is filled past the lower open end of pour spout 64.

The cumulative area of vent openings 60 and 62 are chosen to be sufficiently small as to maintain superatmospheric pressure in the decanter when the quantity of coffee adapted to be contained therein is kept at, at least 1600F. With the usual coffee maintenance temperature of 175"F, the vent opening 60 may be 1/16" in diameter and vent opening 62, 1/64" in diameter. Where the coffee is not to be introduced to the decanter through well opening 60, it is desirable that the same be even smaller to further reduce vapor escape to the atmosphere.

The use of the "temperature differential" approach, alone, to extend the pot life of coffee is illustrated in Figures 5 and 6. In these Figures is illustrated a coffee decanter 100 having an external pour spout 102 communicating with the interior of the decanter via opening 104 immediately adjacent a thickened bottom wall 106 adapted to seat on a warming burner, not shown. The decanter and pour spout are of relatively thick-walled, porcelain construction and the lower pour spout opening 105 is wholly contained within the bottom sixth of the decanter fill level. Atop assembly 108 having a large central opening 110 is peripherally sealed with respect to the upper end 112 of the decanter 100 by a deformable seal 114.

In use, freshly brewed coffee is introduced to the decanter such as by flow from an automatic drip coffee maker through central opening 110 in top assembly 108. With decanter bottom wall 106 resting on a conventional, thermostatically controlled warming burner whose maximum surface temperature will vary from 350"F - 425"F, as among the various manufacturers, the temperature of that coffee immediately adjacent the bottom wall will typically stabilize at a "drinking temperature" within the range of 160"F - 180"F. Because of the poor thermal conductivity of the porcelain construction, the surface temperature of the decanter contained coffee will be less than the drinking temperature at the bottom of the decanter by from 5"F-1 5"F depending, inter alia, on burner temperature, volume of contained coffee, height and wall thickness of the decanter. In any event, a temperature differential inherently exists in such a bottom heated decanter and the differential is even greater at the coffee surface level in the pour spout By reference to the vapor pressure curve for water shown in Figure 9 it will be seen that the exponential nature of the curve across the range in question converts even a small temperature differential to a large change in vapor pressure. Because of the fact that coffee is dispensed from the bottom of the decanter where drinking temperature is maintained, the lower surface level temperature has no drawbacks from the standpoint of hot coffee service but has the advantage of greatly reduced evaporative loss due to the lower vapor pressure. The lower surface temperature also results in a lesser rate of oxidation.

It is to be understood that the decanter 100 of Figures 5 and 6 is fully vented to atmosphere via the large central opening 100 so that both oxidation and evaporation may freely take place at and from the upper surface of the decanter contained coffee. It is the reduced rate of both these deteriorants as a function of the lower surface level temperature as compared with the higher drinking temperature necessarily maintained at the bottom of the decanter that is relied upon to extend the pot life. The peripheral seal 114 between the top assembly and the decanter is to ensure against leakage over the top wall of the decanter when coffee is being dispensed through pour spout 102.

The decanter 120 of Figures 7 and 8 differs from the decanter 100 of Figure 5 only in the construction of the top assembly 122. Top assembly 122 includes a top member 124 which is peripherally sealed with respect to decanter top wall 126 by a seal ring 128.

Top member 124 is downwardly dished to form a well portion 130 and isimperforateexceptfora small central vent 132 with a bore of the order of 1/16" in diameter and an additional "pin hole" vent 134. The upper end of top member 124 is covered with a removable, decorative top 136 having a large central opening 138.

In use, coffee is introduced to the well portion 130 through central opening 138 from which the coffee flows into decanter 120 via central vent 132. Pin hole 134 permits displacement of air from decanter 120 as the coffee level rises above the lower pour spout opening 140. With the coffee decanter 120 filled and that coffee immediately adjacent the bottom thereof maintained at drinking temperature even that reduced vapor pressure resulting from the temperature differential concept described above results in a superatmospheric pressure above the contained coffee level because of the restricted nature of vent means 132 and 134. It is to be understood that this effect may be enhanced and pot life further extended by providing only a single pin hole rather than the central vent 132 in which event top assembly 122 would be fitted to the decanter after it is filled with coffee.In either event, the body of contained coffee is sealed with respect to atmosphere when in the upright, non-pouring position by a liquid seal within pour spout 142 and a vapor seal across the restricted vent means. Thus, oxidation is sharply limited.

Similarly, partial pressures across the iiquid/gas interface approach equilibrium sharply limiting evaporative loss.

The explanation, to this point, of limiting oxidation and evaporation by the limited vent means concept is the same as described above in connection with Figures 1-4.

Although the combination of the "temperature differential" and "restricted vent means" concepts results in pot life extension significantly greater than either, alone; it is thought that the most important aspect as it relates to the combination of these concepts is the fact of the outside poor spout being relatively isolated, thermally, from the heating sources (contained coffee and burned). The explanation is thought to be as follows: Since the upper coffee level within the pour spout is the only area, albeit quite small, at which oxidation and evaporation are unimpeded it will be apparent that, in the combination, if the temperature at the upper pour spout level is significantly less than that necessarily maintained drinking temperature, both oxidation and evaporation from this area will be reduced.

Since the temperature reduction is even greaterthat at the decanter contained surface level because of its relatively remote location, and since the temperature range involved lies on an exponential portion of the vapor pressure curve, the importance of combining these concepts can be seen. Thus, in the thin walled decanters of Figures 1 -4, the temperature at the upper coffee level in the pour spout is substantially the same as the decanter contained coffee by which it is surrounded which coffee is, in turn, at substantially the same temperature as that at the bottom of the decanter since the same is of thin walled borosilicate construction so that pot life of the same (Figues 1-4) is less than in the embodiment of Figures 7 and 8 employing both the "restricted vent means" and the "temperature differential" concepts.

Although the temperature differential that can be achieved is somewhat less, the temperature differential concept can be practiced using a decanter of composite construction if at least the upper wall portion of the decanter is constructed of a material of low thermal conductivity. For example, a composite decanter may have a stainless steel bottom joined with an upper plastics wall construction, such as polysulphone and an external pour spout.

The described apparatus and method are not restricted to coffee - they may equally be adopted for the dispensing of other hot beverages over an extended period of time, such as soups, tea and the like, where flavor and palatability may be affected by oxidation and/or evaporation.

Claims (21)

1. A container for coffee having an open upper end which in use contains a quantity of hot coffee the vapor pressure of which exceeds atmospheric pressure; a top assembly closing the upper end of said receptacle; a pour spout extending from adjacent the bottom of said receptacle to the upper end thereof for dispensing coffee therethrough from the bottom of said receptacle; and means including said top assembly for venting said receptacle and maintaining superatmospheric pressure therein in the presence of a quantity of said hot coffee.

2. A container according to claim 1, wherein said top assembly is substantially wholly contained within the profile of said receptacle.

3. A container according to claim 1 or claim 2 wherein the open lower end of said pour spout is wholly contained within the lower fourth of said receptacle.

4. A coffee receptacle adapted in use to contain a quantity of hot coffee whose vapor pressure exceeds atmospheric pressure; said coffee receptacle having an imperforate peripheral wall and an open upper end, comprising means for maintaining superatmospheric pressure within said receptacle in the presence of a quantity of said hot coffee and dispensing the same from the bottom of said receptacle through the open upper end thereof.

5. A coffee receptacle according to claim 4 wherein said means includes a top assembly substantially sealing said open top, restricted vent means in said top assembly; and a pour spout, sealed with respect to said top assembly, extending from adjacent the bottom of said receptacle to the upper surface of said top assembly.

6. A coffee receptacle according to claim 5 wherein said top assembly includes a condenser section.

7. A method of reducing oxidation and evaporation of coffee in a pour type receptacle, comprising; introducing a quantity of coffee into a coffee receptacle; maintaining said quantity of coffee at a temperature above 160 F; maintaining superatmospheric pressure within said receptacle; and dispensing coffee from immediately adjacent the bottom of said quantity of coffee.

8. A method according to claim 7 wherein the dispensing step includes dispensing the coffee through a pour spout; and maintaining the entire, open lower end of said pour spout within the lower fourth of said receptacle.

9. A method of reducing oxidation and evaporation of coffee in a pour type receptacle, comprising introducing a quantity of coffee into a coffee receptacle; maintaining said quantity of coffee at a temperature above 160"F; maintaining superatmospheric pressure within said receptacle; depleting the coffee level within said receptacle by periodically dispensing one or more volumes of coffee from immediately adjacent the bottom of said quantity of coffee; and maintaining said superatmospheric pressure within said receptacle following each said periodic dispensing until not more than a predetermined volume of coffee remains in said receptacle.

10. A coffee decanter having a pour spout openin thereinto immediately adjacent the bottom thereof, said pour spout opening being wholly contained within the lower one sixth of said decanter, wherein said decanter consists of a material exhibiting poor thermal conductivity.

11. A coffee decanter according to claim 10 wherein said decanter is of porcelain construction.

12. A coffee decanter according to claim 10 wherein said decanter is of thick walled glass construction; said wall thickness being at least 0.150".

13. A coffee decanter according to any one of claims 10 to 12, having an open upper end and adapted to contain a quantity of hot coffee whose vapor pressure exceeds atmospheric pressure; a top assembly closing the upper end of said decanter; and means including said top assembly for venting said decanter and maintaining superatmospheric pressure therein in the presence of a quantity of said hot coffee.

14. A method of reducing oxidation and evaporation of coffee in a pour type decanter, comprising introducing a quantity of coffee into a decanter; maintaining the bottom contents thereof at a drinking temperature above 160"F; maintaining the surface level temperature thereof at less than the aforesaid drinking temperature; and dispensing coffee from the bottom contents of said decanter.

15. A method according to claim 14 and including the step of maintaining superatmospheric pressure within said decanter.

16. A bottom heated coffee decanter for containing a quantity of coffee and maintaining a temperature differential between the lower bottom heated portion thereof and the upper surface level thereof, wherein said decanter is of thick walled porcelain construction and includes a pour spout continuous with an external side wall of said decanter; said pour spout opening into said decanter immediately adjacent said lower bottom heated portion.

17. A coffee decanter according to claim 16 and including means for maintaining superatmospheric pressure within said decanterwhen the lower bottom heated portion of said coffee is maintained above 1600F.

18. A container for coffee substantially as herein before described, with reference to Figures 1 and 2 or Figures 3 and 4 Figures 5 and 6 or Figures 7 and 8 of the accompanying drawings.

19. An apparatus for dispensing beverages substantially as herein before described, with reference to Figures 1 and 2, or Figures 3 and 4, Figures 5 and 6 or Figures 7 and 8 of the accompanying drawings.

20. A method of reducing oxidation and evaporation of coffee substantially as herein before de scribed, with reference to Figures 1 and 2, or Figures 3 and 4, Figures 5 and 6 or Figures 7 and 8 and Figure 9 of the accompanying drawings.

21. A method of reducing oxidation and evapora tion of beverages substantially as herein before described, with reference to Figures 1 and 2, or Figures 3 and 4, Figures 5 and 6 or Figures 7 and 8 and Figure 9 of the accompanying drawings.