Sunday, October 23, 2011


Man's quest for natural substances that can mimic sweet taste is never ending and it has assumed a new urgency because of the debilitating adverse effect of high intake of sugars like Sucrose in human body. The diabetic population that cannot ingest too much sugar and over weight consumers look for sugar substitutes which are safe for long term consumption. Almost all successful substitutes in the market to day are synthetic ones except Stevia Ribaudiosides and their safety status is always mired in controversy, leaving the consumers in a blind regarding the desirability of using them in daily diet. As for Stevia sugar, there is still some uncertainty regarding unreserved and universal clearance though consumers seem to be preferring this product increasingly these days.

Arrival of sweet tasting proteins has further kindled the interest in sugar substitutes and exciting developments are taking place to make some of these protein based natural sweeteners commercially available. A few of these proteins having potential to become acceptable sugar substitutes include Miraculin, Brazzein, Curculin, Monellin,Thaumatin, Pentadin and Mabilin, all natural substances present in plants growing in Africa and other places with traditional use well established. Of all these substances, Miraculin, a glycoprotein  occurring in the so called Miracle fruit from Africa has attracted world wide attention because of its peculiar property to impart sweetness in the mouth through molecular interaction on the tongue, without being sweet by itself. There are many commercial products based on this fruit that promise a lot to the consumers but unless more developmental work is done it is unlikely to go main stream immediately.

The Miracle fruit which is now grown in Ghana, Puerto Rico, Taiwan and Florida in the US is perishable, lasting for 2-3 days but can be processed to get the pulp which if freeze dried can be quite stable for more than 6 months. Most commercial preparations are based on freeze dried powder which can be formulated into convenient form of delivery such as tablets and capsules. When the fruit is chewed for some time in the mouth, Miraculin released from the fruit interacts with the taste buds linked to sweetness and the resultant coating causes any food at acidic pH tastes sweet. The sweetness created can be equivalent to a 17% sucrose solution but its effect can be varying depending on the acidity of the food consumed. It is not effective below a pH of 3 or above 12. Interestingly sweet modifying effect lasts for 6 months if stored at 5C. Being a protein, Miraculin is not very stable at high temperatures beyond 100C and hence not suitable to be used in baked foods.

Genetic engineering technology has been able to get the Miraculin expressed in E.coli, Lettuce and Tomato. 2 gm of GM Lettuce can express same amount of Miraculin as a single berry of Miracle fruit. However these products will remain unexploited for long because of lack of clearance by the safety authorities world over. One of the reasons for Miraculin not taking off as a sugar substitute is that there are not enough studies on its safety for long term human use as a food additive. The only country that allows use of Miraculin in foods is Japan where commercial products containing Miraculin are in the market.

Imagine the potential for designing hundreds of new products using Miraculin that can be a boon to millions of consumers around the world desperately yearning for sugarless products to sustain their life style, not willing or able to consume high sugar containing foods and beverages. If Miraculin can achieve sweetness equal to 17% of sugar syrup, new products with less sugar or no sugar can be easily developed, the only limitation being that this substance, a protein by nature, is not stable at high temperatures as being encountered in baking. Is it not fantastic that almost all synthetic beverages, most of them made with the much hated HFCS, can be made with zero sugar using Miraculin as an ingredient? How about chocolate products being manufactured using Miraculin that may enable millions of chocolate loving consumers to continue to eat them without any "guilt conscience"! Why not Miraculin containing preparations be made available for household use so that fresh food preparations with sweet taste can be made using significantly less sugar or no sugar at all?

Of course the food technologists will have to work around to evolve right conditions in new products to "activate" Miraculin effect at the point of consumption. This is now possible because the mechanism of action of this active chemical has been elucidated by scientists in Japan and France who report that Miraculin's interaction with the tongue's sweet sensors depends on the acidity of the local environment. At a pH of 4.8,  the sweet-tasting cells on the tongue respond twice as vigorously to Miraculin than they do at a less acidic pH of 5.7. With pH levels of 6.7 and higher, the protein seems to slightly change its molecular shape, blocking the sweet sensors but not activating them. Probably this accounts for the phenomenon that, under certain conditions, sweet foods may taste less flavorful after eating the berry. Plants are known to pack their fruits with sugars to attract animals, which after eating the fruit, distribute the seeds inside through their droppings. But, in a trick of nature, some plants like Miracle fruit, protein instead of sugar, is used to deliver a sweet taste. It is possible that these fruits, small in size with limited biochemical ability to synthesize sugar, have a different mechanism of synthesizing proteins that give the same effect. Interestingly Miraculin is the only one sweetness associated natural protein which does not taste sweet while all others, considered sugar substitutes, be it chemical or natural, are sweet themselves at relatively low concentrations.


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