Isomalt is one of those ingredients that has been around long enough for everyone to be familiar with the name and still not necessarily know what exactly they are dealing with. It’s gone mainstream with the advent of Ace of Cakes and the Cake Boss. If you watch either of these shows you can't help but be familiar with the terms “dirty ice the cake” and “I used isomalt for…” We were starting to get more questions about isomalt and we knew it was time for us to take a closer look at what we were working with.
Isomalt is a sugar alcohol. Contrary to what you may think, a sugar alcohol does not contain alcohol, its structure simply has many of the chemical attributes of both sugar and alcohol. Isomalt is derived from beet sugar. The sucrose is treated with an enzyme to become isomaltulose. Then it is hydrogenated and converted into two different disaccharide alcohols: gluco-mannitol and gluco-sorbitol. The chemical changes make the isomalt more stable than sucrose. It is approximately half as sweet as sugar with a very low level of hygroscopicity, meaning that it doesn’t absorb water in the same way that sugar does.
Isomalt is commonly used as a sugar replacement. It can be substituted at a 1:1 ratio with sucrose although the isomalt recipe will be less sweet than the original. It is often combined with sucralose or other intense sweeteners and provides the bulk and texture of sugar while simultaneously masking any bitterness from the other sweetener. Isomalt is resistant to acid and enzyme hydrolysis. It has good solubility and melts at temperatures from 140-150°C. Isomalt has good flavor release, dissolves slowly, and holds color well. It is often used in baked goods, sugar free jams and jellies and candy making. Isomalt is also popular for sugar art; it is often used to make display pieces, candy jewels and cake decorations.
According to the manufacturer there are four types of isomalt. Isomalt ST, which is their all purpose product, used at a 1:1 ratio with sugar and considered especially good for baked goods and hard candies. Isomalt GS is designed for use in coatings and other applications requiring solubility in the finished product. It is used for chewy candies and other soft sweetened products. Recipes made with GS have a good spreading texture with little syneresis or browning. Isomalt LM is designed to work with chocolate to preserve the products melting properties and the snap and texture of tempered chocolate. The fourth product is isomalt DC designed for use in compressed products like vitamins and flavor tablets, which is more of an industrial application than a culinary one. Interestingly most purveyors simply sell isomalt without specifying the type. Isomalt ST seems to be the one most readily available.
Isomalt is popular because it has a very low calorie value, only 2 per gram. It is not easily digested and passes through the intestines like dietary fiber. For this reason it can cause some gastric upset, much the same way that beans or other high fiber foods can inspire gas, bloating, and diarrhea. Studies have shown that if isomalt is consumed on a regular basis a tolerance can be built up in the system. Generally speaking it is recommended that people keep consumption to a minimum and do not overindulge until they know how well their systems handle isomalt and any other sugar alcohols.
Isomalt is low on the glycemic index making it a good sugar substitute for people with type 1 or type 2 diabetes. In general sugar alcohols convert to glucose more slowly than sugars, don't cause sudden increases in blood sugar when consumed, and require minimal amounts of insulin to be metabolized by the body.
Isomalt does not promote cavities because plaque bacteria do not break it down into acids in the mouth. It encourages the release of salivia in the mouth, which reduces acid levels in the mouth and increases the presence of calcium on the surface of teeth.
To be sure isomalt does not behave exactly like sugar. No substitute can be expected to have all the same properties as the original. In fact the reduced sweetness is a major selling point for chefs because sometimes desserts can be too sweet when you add the amount of sugar needed to provide moisture and body to a specific application. The most common application is to use isomalt to make croquants, either on its own or in combination with other sweeteners. It's reduced sweetness allow chefs to make savory croquants in flavors that were not possible in the past. A quick google search will yield countless recipes from chefs around the world. Isomalt is a versatile ingredient definitely worth exploring.