The sweet life of a chemist

Sweetness has a positive connotation. The sweetness of character traits attracts people. Small children and animals are "cute". Victory tastes sweet, and everyone wants a sweet life - although we must be careful when someone "sweetens" us too much. Meanwhile, the materialization of sweets is ordinary sugar.

Scientists wouldn't be themselves if they didn't look at this abstract concept. They came up with it in the semblance of density or volume sweetnesswhich numerically describes the measure of sweetness. More importantly, sweetness measurements are quite acceptable even in modest home laboratory settings.

How to measure sweetness?

There is no (yet?) sweetness meter. The reason is the incredible complication of the primary chemical senses: taste and the associated sense of smell. In the case of much younger in evolutionary sense organs that respond to physical stimuli (sight, hearing, touch), equivalent instruments were constructed - light-sensitive elements, microphones, touch sensors. In terms of taste, there are assessments based on the subjective feelings of the respondents, and human tongues and noses are measuring instruments.

10% food sugar solution, i.e. sucrose. For this ratio, the conditional value is 100 (in some sources it is 1). It is called relative sweetness, denoted by the abbreviation RS (English). The measurement consists in adjusting the percentage concentration of a solution of the test substance so that the impression of sweetness it produces is identical to that of the reference. For example: if a 5% solution has the same taste effect as a 10% sucrose solution, the test substance is sweet at 200.

Sucrose is the benchmark for sweetness.

It's time for sweetness measurements.

You need it the weight. In a home laboratory, a cheap pocket model is enough for a dozen zlotys, with a carrying capacity of up to 200 grams and weighing with an accuracy of 0,1 g (it will come in handy during many other experiments).

Now proven products. Sucrose regular table sugar. Glucose can be found at the grocery store, it is also available there xylitol as a sugar substitute. [glucose_xylitol] fructose take a look at the diabetic food shelf while lactose used in home brewing.

We prepare solutions with concentrations from 5 to 25% and label them in a known way (a solution of each substance in several concentrations). Remember that these are products meant to be eaten, so be sure to keep an eye on them. hygiene rules.

Look for experimenters among your family and friends. Sweetness tests are carried out under the same conditions as when tasting the aromas of wine and coffee, only the tongue is wetted with a small amount of solutions (without swallowing) and the mouth is thoroughly rinsed with clean water before tasting. next solution.

Not always sweet sugar

Sugar	RS
fructose	180
glucose	75
mannose	30
galactose	32
sucrose	100
lactose	25
maltose	30

The tested compounds were with sugar (except xylitol). IN table they have corresponding RS values. Simple sugars (glucose, fructose, mannose, galactose) are usually sweeter than disaccharides (sucrose is the only very sweet complex sugar). Sugars with larger particles (starch, cellulose) are not sweet at all. For the perception of sweetness, it is important that the molecule and the taste receptor match each other. This condition is especially relevant to the size of the molecule, which explains the greater sweetness of sugars with smaller molecules. The sweetness of natural products is due to the presence of sugars in them - for example, honey (about 100 rupees) contains a lot of fructose.

The evolutionary reason sugars are perceived as palatable (which leads to the consumption of foods containing them) is their easy digestibility and high calorie content. So they are a good source of energy, "fuel" for the cells of our body. However, the physiological adaptations that were necessary to survive in the era of prehumans in an era of easy access to food cause many negative health consequences.

Not only sugar is sweet

They also taste sweet non-sugar compounds. Xylitol has already been used in attempts to determine the sweetness of substances. It is a natural derivative of one of the less common sugars and its RS is similar to sucrose. It is an approved sweetener (code E967) and is also used to improve the taste of toothpastes and chewing gums. Related compounds have similar uses: mannitol E421 i sorbitol E420.

Molecule model of some sugars: glucose (top left), fructose (top right), sucrose (bottom).

Glycerol (E422, liquor sweetener and moisture retention) and amino acid glycine (E640, flavor enhancer) are also sweet tasting substances. The names of both compounds (as well as glucose and some others) are derived from the Greek word meaning "sweet". Glycerin and glycine can be used for sweetness tests (provided that they are pure, obtained, for example, from a pharmacy). But let's not test the taste of any other compounds!

Proteins extracted from some exotic plants are also sweeteners. In Europe it is allowed for use. Taumatine E957. His RS is around 3k. times higher than that of sucrose. There are interesting relationships miraculinAlthough it doesn't taste sweet on its own, it can permanently alter how the tongue's receptors work. Even lemon juice tastes very sweet after taking it!

Other sugar substitutes stevioside, that is, substances extracted from a South American plant. These substances are about 100-150 times sweeter than sucrose. Steviosides have been approved for use as a food additive under the code E960. They are used to sweeten drinks, jams, chewing gum, and as sweeteners in hard candies. They can be eaten by diabetics.

Of the popular inorganic compounds, they have a sweet taste. giving the sun (originally this element was called glucin and had the symbol Gl) and Lead. They are very poisonous - especially lead (II) acetate Pb (CH₃Chief operating officer)₂, already called lead sugar by the alchemists. Under no circumstances should we try this relationship!

Sweetness from the lab

Food is increasingly full of sweets not from natural sources, but straight from the chemistry lab. it's definitely popular sweetenersThe RS of which is tens and even hundreds of times greater than that of sucrose. As a result, the amount of energy from the minimum dose must be eliminated. When substances are not burned in the body, they really have "0 calories". Most commonly used:

• saccharin E954 - the oldest artificial sweetener (discovered in 1879);
• sodium cyclamate E952;
• aspartame E951 - one of the most popular sweeteners. In the body, the compound breaks down into amino acids (aspartic acid and phenylalanine) and the alcohol methanol, which is why foods sweetened with aspartame carry a warning on the packaging for people with phenylketonuria (a genetic disorder of phenylalanine metabolism). A common complaint about aspartame is the release of methanol, which is a toxic compound. However, a typical dose of aspartame (when consumed no more than a gram per day) produces only tenths of a gram of methanol, which is not related to the body (more is produced by natural metabolism);
• acesulfame K E950;
• sucralose E955 - a derivative of sucrose, in which chlorine atoms are introduced. This chemical "trick" prevented the body from metabolizing it.

The disadvantage of some artificial sweeteners is that they break down during food processing (eg, baking). For this reason, they are only suitable for sweetening prepared foods that will no longer heat up.

Despite the tempting properties of sweeteners (sweetness without calories!), the effect of their use is often counterproductive. Sweet taste receptors are scattered throughout many organs of our body, including the intestines. Sweeteners stimulate intestinal receptors to send a “new delivery” signal. The body tells the pancreas to produce insulin, which helps move glucose from the blood to the cells. However, when sweeteners are used instead of sugar, there is no substitute for glucose excreted in the tissues, its concentration decreases and the brain sends signals of hunger. Despite eating a sufficient portion of food, the body still does not feel full, although sugar-free products contain other ingredients that provide energy. Thus, sweeteners prevent the body from properly estimating the calorie content of food, resulting in a feeling of hunger that encourages further eating.

Physiology and psychology of taste

Time for some impressions.

We put a large crystal of sugar (ice sugar) on the tongue and slowly suck it. Rinse your mouth with water and then dust your tongue with a pinch of powdered sugar (or finely ground regular sugar). Let's compare the impressions of both products. Fine crystalline sugar seems sweeter than ice sugar. The reason is the rate of dissolution of sucrose, which depends on the surface of the crystals (and this, in total, is more for a small crumb than for one large piece of the same weight). Faster dissolution results in faster activation of more receptors on the tongue and a greater sensation of sweetness.

super sweet

The sweetest known substance is a compound called Lugduname, obtained by French chemists from Lyon (in Latin). The RS of the substance is estimated at 30.000.000 300 20 (that's XNUMX times sweeter than sucrose)! There are several similar connections with Rs XNUMX million.

In the old biology textbooks there was a map of the sensitivity of the tongue to individual tastes. According to her, the very end of our taste organ must have been particularly receptive to sweets. Moisten a hygienic stick with sugar solution and touch the tongue in different places: at the end, at the base, in the middle and on the sides. Most likely, there will not be a significant difference in how different areas of it respond to sweetness. The distribution of receptors for basic tastes is almost uniform throughout the tongue, and the differences in sensitivity themselves are very small.

Finally, something from psychology of taste. We prepare sugar solutions of the same concentration, but each of a different color: red, yellow and green (we color, of course, with food coloring). We carry out a sweetness test on acquaintances who do not know the composition of the solutions. They will most likely find that red and yellow solutions are sweeter than green solutions. The result of the test is also a relic of human evolution - red and yellow fruits are ripe and contain a lot of sugar, unlike unripe green fruits.