What’s so ‘Miracle’ in Miracle Fruit?

Large varieties of fruits are available in the world but only a few of them are known to the majority of population. Many of them are underutilized and are gaining importance nowadays. There is one fruit in West Africa, called miracle fruit, which has taste modifying properties. You must be thinking what do I mean by taste-modifying properties? Well, this fruit changes the taste of any substance from sour to sweet which means, you’ll perceive sweetness even if you consume sour product, e.g. lemon.

Fascinating, right?

How does it happen? Let's see in detail.

The scientific name of the miracle fruit is Synsepalum dulcificum, which is a native shrub in tropical West Africa. The fruit looks like a small, red berry with a single seed inside. When the flesh is chewed, it causes a sour substance to taste sweet and this modifying effect lasts for 1-2 hours usually.

The compound responsible for this magical effect is miraculin. Miraculin is a glycoprotein, with two sugars linked to two amino acid residues. It consists of 191 amino acids and 13.9% by weight of various sugars. If tasted like a pure compound extracted from the miracle fruit, miraculin is not at all sweet itself but causes other sour substances to taste sweet.

The mechanism of action can be explained as: On consumption, miraculin binds ‘adjacently’ to the sweet taste receptors in such a way that sugar groups can’t bind to sweet receptor sites henceforth, miraculin doesn’t cause any sweetness perception on consumption. When a sour compound is consumed, protons (H+) cause the conformational changes in the sweet receptor sites, causing the sugar groups in the glycoprotein to bind to them thereby, giving a sense of sweetness. In other words, the major mechanism for sweetness perception is the low pH-induced conformational changes of the taste receptors that detect sweetness. This effect continues till the miraculin is diluted or thoroughly eliminated from the tongue by the saliva.

The other theories suggest that miraculin suppresses the sour taste receptors or paralyzes some papillae of the tongue which gives the sweetness perception rather than sourness, but such theories are not accepted worldwide.

Miracle fruit has an important role in the food industry. Scientists have found that miraculin has a great activity as an alternative sweetener. Due to the restricted sugar consumption, many fruit-based beverages are formulated with artificial sweeteners. Although such sweeteners don’t give calories, it is advisable to not use them for a long period or above the permissible limit. In that sense, miraculin is a great alternative to artificial sweeteners. As per the studies, sweetness perceived by ingestion of citric acid after miraculin exposure is 3000 times that of sucrose. The major drawback till now is that one needs to consume a small quantity of miracle fruit or miraculin before ingestion of unsweetened sour beverage to get the sweetness perception. There is no study published claiming the same effect if miraculin is added directly in the beverage, leading to the scope for research for food technologists.

Considering the regulatory issues, FDA has not approved the usage of miracle fruit extract as a food additive. However, it is approved in Japan as a safe food additive and considered as novel food by European Union.

Since the fruit is perishable in nature, miracle fruit tablets of longer shelf-life are available in the market which has to be consumed before consumption of unsweetened beverage for the sweetness perception. These tablets can be used by the diabetic patients or calorie-conscious people to limit their intake of sugar.

So, are you interested to try this magical fruit on your own?

References:

1. Kurihara, K., & Beidler, L. (1968). Taste-Modifying Protein from Miracle Fruit. Science, 161(3847), 1241-1243. doi: 10.1126/science.161.3847.1241

2. Rodrigues, J., Andrade, R., Bastos, S., Coelho, S., & Pinheiro, A. (2016). Miracle fruit: An alternative sugar substitute in sour beverages. Appetite, 107, 645-653. doi: 10.1016/j.appet.2016.09.014

3. Sun, H., Kataoka, H., Yano, M., & Ezura, H. (2007). Genetically stable expression of functional miraculin, a new type of alternative sweetener, in transgenic tomato plants. Plant Biotechnology Journal, 5(6), 768-777. doi: 10.1111/j.1467-7652.2007.00283.x

4. BARTOSHUK, L., GENTILE, R., MOSKOWITZ, H., & MEISELMAN, H. (1974). Sweet taste induced by miracle fruit (Synsepalum dulcificum)☆. Physiology & Behavior, 12(3), 449-456. doi: 10.1016/0031-9384(74)90122-x