Sweetness is one of the 6 basic tastes1. Mankind has felt the need to sweeten some of the foods they consume for a very long time. It has long been used to sweeten foods that are very sweet and high in carbohydrates, such as honey and molasses, to sweeten their food.
The discovery of granulated sugar by Indians crystallizing sugar from sugar cane in the 4th century AD opened a new door in the sweetening of foods. Granulated sugar has been used extensively in the sweetening of foods since then.
Looking at the chemistry of the job, the reason why foods such as honey, molasses and granulated sugar are sweet is that they contain a high percentage of carbohydrates or are composed entirely of carbohydrates.
As a matter of fact, carbohydrates are sweet compounds and glucose, a carbohydrate monomer, takes its name from the Greek word “gluco” meaning “sweet”. The fact that carbohydrates are sweet substances has caused them to be called “sugars”.
As of the 19th century, the discovery of some “sweet” substances such as saccharin2 by chance opened a very different window in the sweetening of foods. Saccharin and the class formed by these sweet substances discovered later are referred to as “sweeteners” today.
Sweeteners have significant advantages over carbohydrates. Their main advantage is that although carbohydrates are an important source of calories, sweeteners have little or no calories. In this way, sweeteners provide the opportunity to sweeten the food they are added to without increasing the calories.
This is an important plus in terms of body health and paves the way for individuals who cannot consume glucose-containing foods, such as diabetics, to sweeten their foods. Another important advantage of sweeteners is that very small amounts are sufficient to sweeten food.
At this point, it is necessary to elaborate on the concept of “degree of sweetness”. Not all sweet substances are equally sweet; degrees of sweetness are different. The degree of sweetness of sweeteners is determined by comparing it with the “sweetness imparted by sucrose”.
In this context, the sweetness of sucrose was accepted as 100 and the sweetness of other sweet substances was determined by comparing it with sucrose. For example, lactose (sweetness 20) is less sweet than sucrose, while the artificial sweetener aspartame (sweetness 10,000-20,000) is much sweeter than sucrose. The table below shows the sweetness levels of sweet substances;
Degrees of the sweetness of sweeteners
| Name | Degree of sweetness |
|---|---|
| Sucrose | 100 |
| Glucose | 70 |
| Fructose | 180 |
| Lactose | 20 |
| Maltose | 30 |
| Xylose | 40 |
| Raffinose | 23 |
| Invert sugar | 130 |
| Corn syrup (fructose syrup) | 100 |
| Xylitol (E 967) | 100 |
| Sorbitol (E 420) | 60 |
| Mannitol (E 421) | 40 |
| Monellin3 | 300.000 |
| Stevia (E 960a – E 960c) | 25.000 |
| Thaumatin (E 957) | 75.000-160.000 |
| Saccharin (E 954) | 30.000-50.000 |
| Aspartame (E 951) | 10.000-20.000 |
| Cyclamate (E 952) | 3.000 |
| Acesulfame K (E 950) | 13.000-20.000 |
| Neohesperidin DC (E 959) | 40.000-60.000 |
| Neotame (E 961) | 700.000-1.300.000 |
As it is known, sucrose is a disaccharide carbohydrate found in granulated sugar4. The disaccharide structure consists of glucose and fructose monosaccharides.
As can be seen in the table, glucose has a sweetness degree of 70 and fructose has a degree of sweetness of 180, while the sweetness degree of sucrose, which is formed by the combination of the two, is 100.
Therefore, if sucrose is broken down into its building blocks, the sweetness will increase, although the amount remains unchanged. If sucrose is treated with acid (such as citric acid, formic acid and acetic acid), the bond between fructose and glucose is broken and equal amounts of D-glucose and D-fructose are released5. The new sweetness degree of the resulting mixture is 130.
This product is called “invert sugar” and is frequently used in industry. In this way, more sweetness is obtained from the unit amount and less amount of sugar is used. The use of invert sugar can also prevent the crystallization of sugar in the product.
In this way, both cost advantage is provided in the industry and possible structural problems that may be encountered in the product are eliminated6.
The condition that disaccharides can become sweeter when broken down is also observed in lactose-free milk. Lactose, as it is known, is a milk carbohydrate and its sweetness level is 20.
Some people experience a digestive problem called “lactose intolerance” when they consume lactose-containing food. Therefore, these individuals cannot consume any food containing lactose.
Some product developers have chosen to break down lactose in milk to solve this problem. In this way, they developed a method that allows individuals with lactose intolerance to consume milk and dairy products.
As it is known, these products are available in the market as “lactose-free milk”7. In this method, the “lactase” enzyme is added to the milk and the lactose in it is broken down. Thus, the lactose problem is solved. When lactose is broken down, its monomers D-glucose and D-galactose are released.
However, these monomers are sweeter than lactose, resulting in milk that is sweeter than it should be. This is because the consumed “lactose-free milk” is perceived as sweeter than normal milk.
Corn syrup (also called fructose syrup or high fructose corn syrup) is obtained by hydrolyzing corn starch followed by a series of treatments. Essentially, starch is composed of glucose monomers. However, after starch is hydrolyzed and glucose is released, glucose is converted to fructose by the enzyme isomerase.
As can be seen from the table above, fructose is a very sweet molecule compared to glucose (fructose; 180; glucose; 70). Therefore, with this process, the sweetness of the unit amount is increased. In this way, a cost advantage is provided. Corn syrups have different fructose-containing varieties such as 42%, 55% and 90%.
The rest of the percentages are predominantly glucose and very small amounts of other components. As the fructose ratio in the syrup increases, the sweetness also increases. Today, the use of corn syrup is estimated to account for 40% of total sweetener use.
Health Effects of Sweeteners
Consumption of high amounts of fructose can cause some problems in terms of human health. As a matter of fact, the metabolism of fructose in the body is quite different from glucose. The absorption of glucose from the intestines requires energy expenditure (ATP), while the absorption of fructose does not require energy.
As a result, the high amount of fructose absorbed from the intestines accumulates in the liver. A high amount of fructose, which is metabolized in the liver, does not affect the release of insulin and leptin hormones as glucose does, causing high energy to be obtained without creating a feeling of satiety in the body. This situation constitutes the first link in a chain of health problems.
It has been suggested by researchers that high fructose consumption habits may cause oxidative stress, glucose intolerance, insulin resistance, type 2 diabetes, obesity, hypertension and cardiovascular disorders; It is reported that it may also have harmful effects on the nervous system (Ross et al. 2009).
Another negative aspect of corn syrup is that it can be contaminated with mercury during production (Karaoğlu 2011). As it is known, mercury has a toxic effect on the human body.
Corn syrup is also frequently used as bee food in beekeeping. However, it is reported that corn syrup may have a toxic effect on bees and thus cause the deterioration of bee colonies.
As a result, it can be said that the widespread use of corn syrup, which is economical and readily available, is not very suitable.
Some researchers suggest that some sweeteners such as aspartame and saccharin have negative effects on human health. Today, the opinion that these sweeteners have negative effects on health is widely accepted in society.
However, the US Food and Drug Administration (FDA) gives the following response to these claims; “Food safety experts generally agree that there is no convincing evidence of a cause-and-effect relationship between these sweeteners and adverse health effects in humans. The FDA has been monitoring consumer complaints about possible adverse reactions for more than 15 years. For example, aspartame has not been shown to cause adverse or allergic reactions in carefully controlled clinical studies.”
On the other hand, in July 2023, the World Health Organization (WHO) declared that aspartame is “possibly carcinogenic. However, there is no definitive evidence, WHO bases this declaration on three scientific studies on liver cancer. WHO did not prohibit the use of aspartame and the daily consumption limit did not change the limit of 40 mg per kilogram.
This approach of WHO is interpreted as “avoiding excessive consumption.” Today, aspartame is used in approximately 6000 products, primarily diet foods.
Regarding the negative effects of sweeteners on health, the Food Standards Agency (UK) makes similar statements to the FDA. The FSA reports that funds are provided for research in this direction and that aspartame does not cause any adverse health effects as a result of the studies.
Regarding aspartame, it is necessary to give the following information; Aspartame is a molecule containing the amino acid “phenylalanine”. Some individuals have a rare inherited disease known as phenylketonuria (PKU).
Phenylketonuria patients cannot consume any food containing phenylalanine. Therefore, foods containing aspartame should not be consumed by patients with phenylketonuria. Although aspartame contains only a small amount of phenylalanine, the labels of foods and beverages containing aspartame should include a statement declaring the presence of phenylalanine for people with phenylketonuria.
Referenced sources;
Ross, A.P., Bartness, T.J., Mielke, J.G., Parent,. M.B. 2009. A high fructose diet impairs spatial memory in male rats. Neurobiology of Learning and Memory, 92: 410–416.
Karaoğlu, M. 2011. “Yüksek fruktozlu mısır şurubu.” Gıda Mühendisliği Dergisi 33: 1-12.
1 Other basic flavors are saltiness, bitterness, sourness, metallic taste and umami taste.
2 Saccharine was discovered accidentally in 1873 and was the first artificial sweetener to be used. The discovery of saccharine was followed by the discovery of cyclamate in the 1950s, aspartame in 1965 and acesulfame K in 1967.
3 Monellin is a sweet plant-derived protein. Being a protein causes its structure to be denatured in heat treatment applications. Therefore, its usability in the food industry is quite limited. However, it does not have legal status in the European Union, the United States of America and Turkey. Therefore, it is not used as a sweetener in the food industry in these countries. However, it is approved as an additive in Japan.
4 Granulated sugar is produced from sugar cane and sugar beet. Powdered sugar consists of 99.9% sucrose. In general, 1 kg of granulated sugar is obtained from 7-8 kg of beet. Although their sources are different, there is no chemical difference in the granulated sugar obtained from both plants and they have equal nutritional properties.
5 Apart from acid treatment, it is possible to break down sucrose with enzymes called “invertase”.
6 The use of invert sugar can reduce the crystallization problem of sugar. However, excessive use of invert sugar causes adhesion problems in the product; If it is used less, it can cause crystallization and a rough appearance in the product.
7 In fact, it would be more appropriate to call these kinds of milk lactose-cracked milk instead of lactose-free milk.
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