properties of sugar

① have a sweet taste
It is a disaccharide in which one molecule of glucose and one molecule of fructose are combined.
Characterized by refreshing sweetness.

② Solubility and solubility
Sugar is highly hydrophilic and dissolves easily in water.

temperature °C

grams of sucrose in 100 g of solution

grams of sucrose dissolved in 100g of water

specific gravity of solution

③ Hygroscopicity (dehydration effect due to osmotic pressure)
Sugar is hygroscopic, but fructose is the most hygroscopic sugar, so adding invert sugar containing fructose prevents drying.

④ Prevention of aging of starch
Since sugar is a hydrophilic substance, it has the property of attracting water molecules. When pregelatinized (gelatinized) starch and sugar coexist, the sugar takes up water molecules, leaving the starch in a low-moisture state.
If there is little moisture, α-starch is difficult to be beta-converted (aging).
White bread is easy to stale, but castella with a lot of sugar is hard to stale.
starch and sugar

⑤ Antiseptic
Adding a large amount of sugar to food changes the "free water" to "bound water" and increases the shelf life.
Free water is used by bacteria, fungi, etc., so it causes "rot".

Free water: water that can move freely in food
Bound water: water that is strongly attracted to food components and cannot move

⑥ Anti-oxidation
Oxygen does not easily melt in a concentrated sugar liquid, so confectioneries containing a lot of sugar are less likely to oxidize and give off bad odors even if they contain fat. As a result, the color, aroma and taste are preserved and the shelf life is improved.

⑦ Fermentability
The presence of sugar is required when yeast is issued. Sugar is broken down into glucose and fructose by yeast's invertase, and zymase produces alcohol and carbon dioxide gas, which are useful for creating the porous structure of bread and confectionery.

⑧ Generation of jelly
When sugar is added to fruits or fruit juices containing appropriate amounts of pectin and organic acids and boiled down, gelation occurs when the ratio of sugar concentration, pectin and acid becomes appropriate, forming jam or jelly.

⑨ Prevention of protein denaturation
Adding sugar to the egg mixture increases the heat coagulation temperature. In other words, since protein denaturation is suppressed, it hardens slowly when heated, and sudachi is less likely to occur.
It suppresses the return of egg white foam and stabilizes the foam.

⑩ Caramelization
When a small amount of water is added to sugar and heated, it burns and becomes colored, so it is used in sweets, sauces, etc.
Sugar (sucrose) becomes sweeter when heated

⑪ Improve dispersibility

From here on it's subjective.

When I was in culinary school, I learned that sugar is "water-holding" and "dehydrating."
When I first learned how to do this, I thought, "Which should I do, water retention or dehydration?!" Now that I think about it, it seems correct to say that "sugar itself retains water by dehydrating it from the target food."

There was a time when mold grew on jam. The reason for this is the high water absorption of sugar. In other words, sugar absorbs moisture such as humidity, and the concentration of sugar on the surface of the jam decreases, causing mold to form.

As a countermeasure, I think that it can be prevented by storing it in a dry place and by increasing the concentration of sugar when making homemade jam.