Thaumatin is actually a group of many low molecular weight proteins with intense sweetness. These are labelled I,II, III, (Van der Wei & Loeve, 1972) b and c (Higginbotham and Hough, 1977). The proteins are in the same family of protein sweeteners as monellin and brazzein. It is extracted using water from the arils of the West African perennial plant, the katemfe fruit, Thaumatococcus danielli Benth.
Katemfe fruit is grown commercially in many parts of Western Africa but especially Democratic Republic Of Congo, Sierra Leone, Nigeria and various other western African countries.
To many product developers it is treated as a low-calorie sweetener and flavour modifier. Indeed, this protein is often used as a flavour-modifier rather than just a sweetener. The proteins are approximately 2,000 times to 10,000 times sweeter than sucrose on a weight for weight basis. Only humans and Old World monkeys can detect this sweetness. The sweetness profile is not the same as sucrose and develops slowly which makes it similar to brazzein.
The lingering aftertaste is reduced marginally by adding other sugars and related sweeteners such as glucuronic acid, sugar alcohols including erythritol and polyol. Synergism in sweetness and taste modification exists with acesulfame K, saccharin and stevioside but not with cyclamate or aspartame.
Uses
Thaumatin is highly water soluble with good stability to heat and can be used in products with an acidic pH. The sweetness disappears with heating in neutral or alkaline pH solutions for 15 minutes but is acid stable enough at pH 2 to retain sweetness when heated for 4 hours at 80 ° Cent.
The extra stability is due to the presence of eight disulphide bridges in its structure.
There is no known interaction between other food ingredients. It has a small positive charge due to the presence of amide containing amino-acids. It may form weak interactions with negatively charged gums such as xanthan, CMC, pectins and locust bean gum but probably not amidated pectins. Precipitation is known when synthetic colours such as Alizarin have been used but the incidence is very rare and not widely reported except in anecdotal studies (FoodWrite, 2017).
Tate & Lyle market the sweetener as Talin. This is an aluminium based salt which increases its sweetness. The use of Talin is still low-level and chewing gum appears to have been the main beneficiary. Use in beverages is highly limited and has fallen away with the rise of stevia.
The sweetener has been used in studies on sweet protein receptors in humans and primates (Glasser et al., 1978).
Extraction And Production Of Thaumatin
The Katemfe fruit is cultivated locally in West African countries where it is often used to flavour fruits. Unilever have isolated and sequenced the two main proteins in thaumatin which are labelled as thaumatin I and II. These proteins were expressed in genetically engineered bacteria.
Thaumatin is produced as a pre-pro-protein. When mature it contains 207 amino acids, a molecular weight of 22,000 daltons, an isoelectric point at pH 12 and eight disulphide bonds (Iyengar et al., 1979).
Availability of thaumatin is limited and so synthesis using transgenic bacteria has been attempted and is largely successful. The bacteria E. coli and even yeast are good source organisms. Some users have even engineered the genes for thaumatin into fruit and vegetable crops to improve their sweetness and overall flavour.
Thaumatin also contains non-proteinaceaous impurities which are mainly carbohydrates derived from the plant cell structure. These include arabinogalactan and arabinoglucuron-oxylan polysaccharides which are carried over during extraction.
Metabolism
As with all proteins, digestion occurs in the gut and should be treated as any protein with a small calorific value.
Regulatory Aspects
Thaumatin is an approved sweetener in the European Union with the labelling number E957, in Japan (agreed in June, 1979) and Israel. The USA granted the proteins with GRAS status (FEMA GRAS 3732) for use in chewing gum but not as a general purpose sweetener.
Safety
No ADI is set but it is estimated that 1 to 2 mg per person per day is a safe enough limit. Toxicological studies have not indicated any adverse effects as a result of consumption.
References
FoodWrite (2017) Interactions Between Sweeteners And Taste-Modifiers, And Other Food Ingredients. Private report for client. Not available. Written October 2017.
Glasser, D., G. Hellekant, J.N. Brouwer and H. Van der Wel. (1978). The taste responses in primates to the proteins thaumatin and monellin and their phylogenetic implications. Folia Primatol. 29 pp. 56-63 .
Green, C. (1999). Thaumatin: a natural flavour ingredient. World Review of Nutrition and Dietetics. World Review of Nutrition and Dietetics. 85: 129–32. doi:10.1159/000059716. ISBN 3-8055-6938-6. PMID 10647344
Higginbotham, J.D. and C.A.M. Hough (1977) Useful taste properties of amino acids and proteins. In: Sensory Properties of Foods (Birch, G.C., J.G. Brennan and K.J. Parker, eds.), pp. 129-149, Applied Sciences, London
Iyengar, R.B., P. Smits, H. Van der Wel, FJ.G. Van der Ouderaa, J.H. Van Brouwershaven, P. Ravebstein, G. Richters and P.D. Van Wassenaar. (1979). The complete amino acid sequences of the sweet protein thaumatin I. Eur. J. Biochem. 96 pp. 193-204
Smole, U., Bublin, M., Radauer, C., Ebner, C., Breiteneder, H (2008). Mal d 2, the thaumatin-like allergen from apple, is highly resistant to gastrointestinal digestion and thermal processing. International Archives of Allergy and Immunology. 147 (4): 289–98. doi:10.1159/000144036. PMID 18617748
Van der Wel, H. and K. Loeve. (1972). Isolation and characterization of thaumatin I and II, the sweet tasting proteins from Thaumatococcus danielli Benth. Eur. J. Biochem. 31 pp. 221-225
I use the fruit in all sorts of foods because it changes there flavour so much. It is really exciting to use with meats because it seems to make them sweeter but still savoury if you get my drift.