>> Thursday, May 28, 2009
A reader recently sent me an e-mail asking me if I knew anything about a mysterious ingredient called "liquid invert sugar" that was on the ingredient list of some granola bars he bought at Target. Great question! Funny, the ingredient has never registered with me, but I noticed on the ingredient list of another product the next day at the grocery store.
So...what is liquid invert sugar? Invert sugar is sucrose (a disaccharide of glucose and fructose) that has been broken into free glucose and free fructose. (Sound familiar? That's what HFCS is too - free glucose and free fructose - only the beginning ingredients and processing are completely different.) Invert sugar is sweeter than table sugar (sucrose) because fructose is sweeter than both sucrose and glucose.
Invert sugar is found naturally in honey and maple syrup. In fact, invert sugar is often referred to as "artificial honey," though it doesn't have any of the wonderful little goodies that honey (or maple syrup, for that matter) contain.
Invert sugar is sold as a liquid as either total invert sugar (50% fructose, 50% glucose) or as a mixture of half sucrose and half invert sugar (50% sucrose, 25% fructose, and 25% glucose).
Why use it? Invert sugar has a lot of desirable properties in baked goods and other processed foods. The sugar crystals in invert sugar are smaller than sucrose, which results in a smoother texture of the final product. The smaller crystals also dissolve faster than sucrose crystals. Invert sugar retains moisture better and improves shelf life. As little as 10-15% of invert sugar mixed with sucrose markedly reduces crystallization in the final product, resulting in longer shelf life as well. All the reasons that manufacturers like HFCS apply to invert sugar.
How is it made? Invert sugar is manufactured a couple of different ways - acid hydrolysis and enzymatic inversion. In acid hydrolysis, sucrose is subjected to acid and heat to break it into glucose and fructose. Many different acids can be used, including citric acid. The process is not perfect, however. Conversion of sucrose to glucose and fructose is low (around 40-70% from what I've read), and energy consumption and cost of production are high. Impurities from polymerization products are an issue with acid hydrolysis of sucrose.
Enzymatic inversion of sucrose is achieved using a yeast derived enzyme known as Invertase. Conversion of nearly 100% can be achieved through enzymatic inversion. Low temperatures can be used with enzymatic inversion eliminating polymerization products (and improving final flavor), and filtering of the Invertase is easy. Enzymatic inversion is not cheap, however, so both methods of inversion appear to be in use.
The home cook can also make invert sugar and in fact does so when making jellies or jams. Mixing sugar with citric acid, cream of tartar, or fresh lemon juice and boiling will result in some sugar inversion - enough to keep the remaining sucrose from recrystallizing.
Should I use Invert Sugar? Again, this is a personal decision. We avoid HFCS (of course) and also fructose as ingredients preferring to limit our free fructose consumption to natural products (like fruits, honey, and maple syrup) that have more to offer. Because of that, we'll probably also add invert sugar as a specific ingredient to our list of things to avoid, but I'm not going to be concerned about the invert sugar that is in jellies and other baked goods where it might form during the baking process.
Hmmm... Learning about invert sugar production does make me wonder how much sucrose if converted to fructose and glucose in our stomachs. I've heard the argument that HFCS is processed the same as sucrose in our bodies because sucrose breaks down into fructose and glucose in the highly acidic environment of our stomachs. I would love to know what the conversion of sucrose to free glucose and free fructose is in our body - something I haven't come across yet. Just one of those things I wonder about.
Keep your questions coming!