the invention will be explained below in more detail with reference to a few examples . immersion extraction of cocoa aroma with hot water , determination of the effect of the extraction temperature in a stirred 10 liter autoclave , 400 g of natural cocoa powder having a fat content of 10 . 5 % and denoted by the type code n - 11 - n were admixed with 4 liters of demineralized water . the autoclave was sealed and the whole set - up then heated to the desired extraction temperature while being stirred intensively with a speed of 1000 rpm , followed by extraction over a period of 1 hour . after the extraction , the aqueous extract was separated from the residue with the aid of an ultracentrifuge at a speed of 30 , 000 rpm . an entirely clear extract was thus obtained . the clear extract was then inspissated to a thick paste by means of freeze - drying . the paste was then pasteurized at 80 ° c . to make it suitable for the tasting panel . in this way , four extractions were carried out at 90 , 110 , 125 and 150 ° c ., respectively . the pastes were assessed in terms of smell and taste in a tasting panel consisting of six persons . to this end , 2 g of paste were mixed with 100 ml of warm water of about 50 ° c . for each panel member . as a reference , a 2 % strength suspension of the original cocoa powder was also assessed . the taste was assessed in terms of various top notes on a scale from 0 to 6 , no taste being observed at 0 and the aroma aspect in question being very prominent at 6 . the table below reproduces the results from the tasting panel . the results show that the best results were obtained at 110 ° c . at 125 ° c . and above an anomalous taste is produced which resembles burnt milk . at 90 ° c ., aroma and taste are less intense . compared with the reference , the aroma and taste intensity is less , with the exception of the “ bitter ” note , which is distinctly more prominent in the case of the aqueous extracts . notwithstanding advice to the contrary in the literature ( k . h . ney , gordian , 1986 ( 11 ), 204 - 205 ), a good extract is obtained with an extraction above 100 ° c . ( 100 - 125 ° c ., the preference being between 105 - 115 ° c .). at 125 ° c . and above , distinctive taste anomalies are obtained . immersion extraction of cocoa aroma with hot water determination of the effect of the extraction time the extraction was carried out in the same way , using 500 g of cocoa powder , as in example 1 , except that the extraction was carried out at 110 ° c . and the extraction time was extended to 3 hours . after 1 , 2 and 3 hours a sample was drawn which was worked up and assessed in the same way as in example 1 . the table shows that the taste strength , in particular , increases with time . after 3 hours , however , an anomalous taste begins to be observed in the aroma . extraction times of less than 1 hour give a lower yield . longer extraction times lead to anomalies in taste . immersion extraction of cocoa aroma with hot water , pilot plant - scale experiment , effect of repeating the extraction in this experiment , 6 kg of cocoa powder were extracted with 60 liters of demineralized water in a stirred 100 liter autoclave . the extraction was carried out at 110 ° c . over a period of 3 hours . after extraction , the extract was separated in a centrifuge at 2200 rpm . the residue from the centrifuge was re - extracted under identical conditions and was separated . the extract was then admixed with 0 . 1 % of potassium sorbate to prevent the growth of mould during storage . part of the extracts was inspissated by means of freeze - drying for the purpose of the taste being assessed in the tasting panel . in addition , a sample of the residue after the second extraction was drawn , which was treated in the same way as the reference . the table indicates that even on a pilot - plant scale it is possible to obtain good extraction , with a powerful cocoa aroma , under the stated conditions , with the exception of the “ bitter ” note , which again is more prominent than in the reference . as it was not possible to use an ultracentrifuge at this scale , the separation had to be carried out by means of an ordinary centrifuge , with the result that the extract was not entirely clear . the residue after the second extraction has a weak cocoa taste . this indicates that by means of the immersion extraction using hot water the aroma components are removed effectively . immersion extraction of cocoa aroma with hot water pilot plant - scale experiment effect of the technique of inspissating the extract portions of the extract of the pilot plant experiment in example 3 were inspissated in various ways : by means of freeze - drying , the extract having been clarified beforehand by means of microfiltration . by means of reverse osmosis , the extract having been clarified beforehand by means of microfiltration . the results indicate that freeze - drying does afford an aroma concentrate having a good odour and taste , except that the taste is considerably more bitter compared with the reference . moreover , the solution of the concentrate in water remains turbid , which is also less desirable . to counteract the turbidity , the aqueous extract was first clarified via a microfilter and then inspissated by means of freeze - drying . now the concentrate did produce a clear solution . however , as the table shows , the cocoa aroma has considerably decreased and the taste notes “ bitter ”, “ astringent ” and “ acidic ” have increased . all this indicates that the quality of the aroma considerably diminishes by this action . when the concentrate is inspissated by means of vacuum distillation , the aroma and the taste are largely lost . only the bitter , acidic and astringent components remain . this therefore is an unacceptable inspissation technique . in the case of inspissation by means of reverse osmosis , the aroma and the taste were well preserved , except that the “ bitter ” note became more prominent . in the course of inspissation , however , crystalline material formed in the concentrate , causing clogging of the membrane and thereby considerably hampering industrial implementation , as the membrane had to be cleaned each time with a solution of dilute hydrochloric acid . when analysed , these crystals were found largely to consist of theobromine . this is a component which occurs in amounts of about 2 to 3 % in cocoa and is co - extracted with hot water . for the purpose of inspissation by means of freeze - drying the solid particles must first be separated off . this can be done effectively only with the aid of ultracentrifuging ( examples 1 and 2 ). this is a very expensive technique . if an ordinary centrifuge is used ( example 3 ), a clear extract is not obtained . to achieve this , the extract must first be filtered via an ultrafilter . this produces a loss in aroma . another drawback of inspissation by means of freeze - drying is that the aroma is very bitter , since the bitter components are co - extracted . concentration by vacuum evaporation results in a large loss of aroma components even at a low temperature of 40 ° c . effectively , all that remains are the bitter and astringent components . many of the literature references relate to the use of vacuum evaporation . concentration by means of reverse osmosis presents major problems on an industrial scale , because of crystallization of the theobromine . furthermore , the aroma is again very bitter . moreover , a clear extract can again be obtained only by ultracentrifuging . in this experiment , various techniques of isolating the cocoa aroma from cocoa powder were compared with one another : 1 . immersion extraction as specified in example 2 using an extraction time of 3 hours 2 . extraction using steam over a filter bed comprising cocoa powder . 100 g of cocoa powder of type n - 11 - n were mixed with 200 g of calcined sea sand to keep the filter bed open during the extraction . the mixture was introduced into a double - layer press filter of type sietz supra 2600 , provided with paper filters s & amp ; s 589 - 2 . after the filter had been sealed , open steam of 100 ° c . was forced through the filter bed . this experiment had to be aborted , because the bed became entirely clogged owing to moisture being absorbed in the cocoa powder , despite the admixture of calcined sea sand . this extraction method was therefore not considered in the assessment . 25 g of cocoa powder of type n - 11 - n were placed on a fluted filter . then , four portions of 250 ml of demineralized water of 85 ° c . were poured onto the powder . the extracts were collected and inspissated by means of freeze - drying as specified hereinabove . the extraction sleeve was filled with 25 g of cocoa powder of type n - 11 - n , and the flask was charged with 100 ml of demineralized water , the powder subsequently being extracted for 4 hours under reflux . the extract was then inspissated by means of freeze - drying as specified earlier . after extraction , the ethanol was evaporated at room temperature in vacuo , and the residue was taken up in a small amount of water to produce a thick paste . in a batch set - up for supercritical extraction , 120 g of cocoa powder were extracted , at a pressure of 175 bar and a temperature of 50 ° c ., for 35 hours using 10 , 000 1 of atmospheric c 2 . the extract was collected in the decompression vessel at 60 - 80 bar . the extract obtained consisted of fat and was suspended in the warm water for the assessment . the trials show that by far the best and most powerful aroma is obtained by means of immersion extraction at 110 ° c . whilst percolation does in principle afford a good aroma , its extraction from the powder is highly incomplete . in the case of the soxhlet extraction , a significant fraction of the aroma is lost , both with water and with ethanol . in the case of supercritical extraction , the yield of the extraction was very unsatisfactory . assessment of aroma concentrates of various aroma producers compared with cocoa powder of type n - 11 - n in a chocolate coating samples of cocoa aroma were obtained from three producers . these samples were assessed in a liquid white chocolate coating . the composition of the coating was as follows : the aroma was admixed to the liquid coating in a percentage as stated in the table . they were tasted in comparison with reference 2 . a negative number means that the aroma in question was characteristically less intense than the reference . in the case of a positive score it was more intense . the aromas tested in exp . 1 to 5 inclusive are so - called nature - identical aromas from haarman & amp ; riemer . experiment no 6 is a natural cocoa aroma from prova sa . experiment no 7 is a natural aroma from nutritec . as stated by the panel , the cocoa sensation is much weaker compared with cocoa powder and many differences in taste are found . 50 kg of cocoa powder were added to 500 1 of water at room temperature . mixing produced a homogeneous mixture . the mixture was heated for 1 hour at 100 ° c . with continuous stirring , followed by cooling to 60 ° c . within 30 minutes . it is important that the extract be rapidly cooled after extraction , given the risk of thermal degradation of aromatic substances in the extract . the liquid extract was filtered with a 0 . 1 mm filter and then , at a temperature of 45 ° c ., passed through a hollow - fibre module at a flow rate of 2 m 3 / h . the hollow fibres were internally coated with a pdms layer having a thickness of 2 μm . the feed side was subject to atmospheric pressure , the permeate side to a pressure of 7 mbar . the permeate was condensed in two steps , a first condenser operating at a temperature of + 3 ° c ., with about 95 % of the permeated water being collected in said first condenser . the uncondensed permeate , viz . the remaining water , and the major fraction of the cocoa aromas were collected in a second condenser . this condenser operated at a temperature of − 196 ° c . the yield of condensate , i . e . the contents of the second condenser , was about 175 g after 1 . 5 hours pervaporation . on the basis of instrumental analyses it could be established that enrichments of relevant aroma compounds in the extract in the second condenser were at an order of magnitude of 200 - 400 compared with the feed . the extract was colourless and had an intense cocoa aroma . sensoric tests by an expert panel confirmed the enrichment found and the high quality of the product . the drawbacks mentioned in example 4 regarding the various inspissation methods do not apply to pervaporation . in the case of pervaporation a simple separation is carried out in which the bitter taste constituents remain in the retentate and may afterwards be added back to the cocoa aroma as desired , since the cocoa aroma requires the bitter components . furthermore , virtually no loss of aromatic substances occurs with the aid of this method , as can be demonstrated with the aid of dynamic - headspace gc ( dh - gc ) analyses ( wampler , see above ) and static - headspace gc ( sh - gc ) analyses . for dh - gc , aroma concentrate and cocoa ( d - ii - a , from adm cocoa bv , netherlands ) were obtained in accordance with the above and a dh - gc analysis was carried out as follows ( for details see wampler hereinabove ): chromatograms of samples of the undiluted pervaporation feed ( i . e . liquid cocoa extract ) of aroma concentrate diluted 30 × ( with water ) as collected in the first condenser and of a 400 × dilution ( with water ) as collected in the second condenser , as shown in fig1 a , b and c , respectively . this technique can be compared with the p & amp ; t gc technique used earlier . in the case of dgi - gc , a small amount of vapour from the thermostatted headspace of the sample is injected directly into the gc . this method is quicker than the p & amp ; t - gc method , but provides reliable results , particularly for the volatile components . about 2 grams of a cocoa sample were weighed into a 40 ml glass vial and sealed with an aluminium screw cap having a teflon ® septum in the centre . the samples were equilibrated for 30 minutes , before 0 . 5 ml of the headspace was injected into the gc ( 1 : 10 split ). an hs850 ce instruments autosampler was used , coupled to a fisons 8533 gc . a 50m × 0 . 32 mm internal diameter ( d f = 1 . 0 μm ) db - waxetr ( j & amp ; e scientific ) column was used for separating the samples , with a helium flow rate of 3 . 8 ml / min . the column temperature was kept isothermal during a run time of 15 minutes . the volatile components were detected by means of an fid detector at a temperature of 250 ° c . all measurements were carried out in duplicate or triplicate ; the results are shown in fig2 . fig2 a shows a chromatogram of undiluted pervaporation feed of cocoa powder n - 11 - n , and fig2 b is a chromatogram of permeate diluted by a factor of 5 , in which extracts of condenser 1 and 2 were combined . this clearly shows that the peak pattern after pervaporation ( fig1 b and 1c , and fig2 b ) substantially matches the pattern after extraction ( fig1 a and fig2 a , respectively ), which means that the concentration ratio of the aromatic substances in question in the condensate ( i . e . after pervaporation ) substantially matches the ratio in the extract .
described is a method for recovering aroma concentrate from a caffeine - or theobromine - comprising food base material , such as coffee or tea , and in particular cocoa , at least including the steps of : introducing the food base material into an aqueous extractant and incubating the food base material at a suitable temperature and for a suitable period , substantial extraction of the aromas taking place to form an aqueous food extract , pervaporating the food extract using a hydrophobic pervaporation membrane to form a food aroma permeate , recovering the permeate to obtain the aroma concentrate . also described are food concentrates obtainable via the abovementioned method .