embodiments of the present invention will now be more particularly described by way of example . the existing process for extracting thaumatin and producing commercially - usable compositions comprising thaumatin generally has the following sequence of steps . excision of arils of the fruit of thaumatacoccus danielii : the katemfe fruit is not a true “ fruit ”, but comprises the “ aril ”, a fleshy sac covering or attached to each seed ( more familiar examples may be the edible “ seeds ” of the pomegranate , or the so - called yew “ berry ”). thaumatin is naturally secreted in the aril , and there are well known cultivation techniques to produce high and reliable thaumatin levels therein . rapid freezing of discrete excised arils , followed by bulk freezing for transport and cold storage of the arils . the first extraction step is an aqueous “ mashing ” of the arils , which is followed by a primary filtration of the mash liquor . caustic treatment of the filtered liquor comprises treatment with sodium hydroxide , followed by a settlement / sedimentation step . the thaumatin remains in solution in the supernatant . the supernatant is decanted and cleaned of remaining suspended solids by a filtration step , followed by an ultrafiltration step . membrane concentration and membrane purification steps are then carried out , to produce a highly concentrated solution of substantially pure thaumatin . the thaumatin concentration may be up to 20 % w / v at this stage , and the ph has typically fallen to the range ph2 . 5 to ph3 . 0 . this “ critical solution ” is then induced to form crystals of thaumatin by reducing its temperature to well below 0 ° c . ( a final temperature of − 20 ° c . may be employed , for example ). this precipitates a very high proportion of the thaumatin as a crop of fine crystals . vacuum drying of the separated crystals is carried out at temperatures ranging from the crystallisation temperature up to ambient temperature or slightly above . the dried crystals are granulated to a desired particle size by ball - milling , followed by dry sieving to remove oversize particles ( typically using a 60 mesh to 80 mesh sieve ) and blending with suitable bulking agents such as maltodextrin , gum arabic or lactose powders ( as appropriate to the planned end - use ) to give a thaumatin composition containing a desired % w / w of thaumatin protein . the methods of the present invention differ from the above known production method mainly in the composition of the critical solution prior to crystallisation , although non - standard temperature profiles for the crystallisation step have also been found to be of benefit . in some embodiments , the aqueous solution comprises 1 ) about 10 % to about 20 % by weight of thaumatin , 2 ) about 5 % to about 15 % by weight of a water - soluble carbohydrate compound , 3 ) about 1 % to about 15 % of a water - soluble natural gum , and 4 ) is at a ph between about 5 and 7 . these embodiments provide increased enhancement of the sweet taste of other sweeteners . in a first example embodying the present invention , a thaumatin composition providing increased enhancement of the sweet taste of other sweeteners was prepared by modifying the above prior art procedure from the pre - crystallisation “ critical solution ” onwards . the remainder of the critical solution comprised water . percentages are expressed as percentages by weight of the critical solution as a whole . the crystallisation step was then carried out by reducing the temperature to − 25 ° c . over a period of approximately 30 minutes . vacuum drying of the resultant crop of crystals was carried out at temperatures gradually rising from − 25 ° c . up to ambient temperature , completing drying at 22 ° c . the dried crystals were ball - milled under standard conditions , sieved and the sub - 80 mesh fraction was blended with maltodextrin to give a series of thaumatin - containing compositions containing a range of known levels of thaumatin protein . when the thaumatin compositions of the first example were compared in organoleptic tests with thaumatin compositions made conventionally , the compositions of the first example produced significantly greater enhancement of the sweetness of other sweeteners than conventional compositions , at the same net levels of thaumatin protein by weight . in some embodiments , the aqueous solution comprises 1 ) about 1 % to about 10 % by weight of thaumatin , 2 ) about 1 % to about 5 % by weight of a water - soluble carbohydrate compound , 3 ) about 5 % to about 15 % of a water - soluble natural gum , and 4 ) is at a ph between about 2 and 4 . these embodiments provide increased enhancement of salt and umami taste . in a second example embodying the present invention , a thaumatin composition providing improved enhancement of salt and “ umami ”/ msg flavours was prepared by modifying the above prior art procedure from the pre - crystallisation “ critical solution ” onwards . the remainder of the critical solution comprised water . percentages again expressed by weight . the crystallisation step in this example was carried out in two stages . the temperature of the critical solution was initially reduced to 2 to 4 ° c . and maintained in that range for a dwell time of about 45 minutes . the critical solution was then reduced further in temperature , reaching a minimum temperature of − 15 ° c . after a further period of approximately 30 minutes . vacuum drying of the resultant crop of crystals was carried out at temperatures gradually rising from − 15 ° c . up to ambient temperature , completing drying at 22 ° c . the dried crystals were ball - milled under standard conditions , sieved and the sub - 60 mesh fraction was blended with gum arabic to give a series of thaumatin - containing compositions containing a range of known levels of thaumatin protein . organoleptic tests were carried out to compare the thaumatin compositions of the second example with thaumatin compositions made conventionally . in this example , the tests compared the enhancement of a “ savoury ” flavour , comprising a salty flavour and a msg /“ umami ” flavour . a target savoury flavour could be achieved with lower levels of salt / msg , with lower levels of thaumatin protein , or lower levels of both . higher levels of thaumatin could be used without introducing a noticeable sweet taste . in some embodiments , the aqueous solution comprises 1 ) about 10 % to about 15 % by weight of thaumatin , 2 ) about 1 % to about 5 % by weight of a water - soluble carbohydrate compound , 3 ) about 10 % to about 15 % of a water - soluble natural gum , and 4 ) is at a ph between about 5 and 7 . these embodiments provide improved masking of bitter and / or sour taste . in a third example embodying the present invention , a thaumatin composition providing improved masking of bitter / sour tastes , was prepared by modifying the above prior art procedure from the pre - crystallisation “ critical solution ” onwards . the remainder of the critical solution comprised water , and percentages are again expressed by weight . the crystallisation step in the third example was then carried out in two stages . the temperature of the critical solution was initially reduced to 2 to 4 ° c ., and was maintained in that range for a dwell time of about 40 minutes . the critical solution was then cooled further , reaching a minimum temperature of − 15 ° c . after a period of approximately 30 minutes . vacuum drying of the resultant crop of crystals was carried out at temperatures gradually rising from − 15 ° c . up to ambient temperature , completing drying at 22 ° c . the dried crystals were ball - milled under standard conditions , sieved and the sub - 80 mesh fraction was blended with maltodextrin to give a series of thaumatin - containing compositions containing a range of known levels of thaumatin protein . organoleptic tests were carried out to compare the thaumatin compositions of the third example with the thaumatin compositions made conventionally . in this example , the masking of a series of sour and / or bitter tastes was examined . the thaumatin compositions of the third example showed significantly greater masking effect against such tastes than did the conventionally - produced compositions . at present , it is believed that it is the composition and ph of the critical solution that has the main effect on the organoleptic performance of the resulting composition , while the crystallisation temperature profile is probably modifying the physical crystal form and size as much as it affects the particular crystal form of the thaumatin . the current theory is that thaumatin has a sufficiently complex structure that crystallisation in the presence of other species ( particularly saccharides ) may result in a range of subtly different crystals forms with differing organoleptic properties . while the above examples use mainly maltodextrin and gum arabic , other polysaccharides may be used , such as poly ( dextroses ) with a range of de ( dextrose equivalent ) values , or starches or modified starches . instead of gum arabic , xanthan gum or gum tragacanth might be used . potassium chloride may be used in place of sodium chloride , and in the second and third examples , magnesium chloride may be used ( nb but not for a sweetness enhancer composition , as in the first example ).
the present invention relates to processes for preparing compositions containing thaumatin having desired properties . more particularly but not exclusively , it relates to compositions containing thaumatin having particular organoleptic properties , and to processes for their manufacture .