High-fructose corn syrup

High-fructose corn syrup (HFCS) – called isoglucose^[1] in Europe and glucose-fructose in Canada – comprises any of a group of corn syrups that has undergone enzymatic processing to increase its fructose content, and then been mixed with pure corn syrup (100% glucose). HFCS is ubiquitous in processed foods and beverages, including soft drinks, yogurt, cookies, salad dressing and tomato soup.

The most common types of high-fructose corn syrup are: HFCS 90 (mostly for making HFCS 55), approximately 90% fructose and 10% glucose; HFCS 55 (mostly used in soft drinks), approximately 55% fructose and 45% glucose; and HFCS 42 (used in most foods and baked goods), approximately 42% fructose and 58% glucose.

The process by which HFCS is produced was first developed by Richard Off. Marshalle and Earl P. Kooi in 1927. The industrial production process was refined by Dr. Y. Takasaki at Agency of Industrial Science and Technology of Ministry of International Trade and Industry of Japan in 1965–1970. HFCS was rapidly introduced to many processed foods and soft drinks in the U.S. from about 1975 to 1985.

Per relative sweetness, HFCS 55 is comparable to table sugar (sucrose), a disaccharide of fructose and glucose. That makes it useful to food manufacturers as a substitute for sucrose in soft drinks and processed foods. HFCS 90 is sweeter than sucrose; HFCS 42 is less sweet than sucrose.

Use as a replacement for sugar

Since its introduction, HFCS has begun to replace sugar in various processed foods in the USA and Canada. The main reasons for this switch are:

• HFCS is somewhat cheaper in the United States due to a combination of corn subsidies and sugar tariffs/quotas. Since the mid-90s US Federal subsidies to corn growers have amounted to $40 billion.
• HFCS is easier to blend and transport because it is a liquid.

Production

High-fructose corn syrup is produced by milling corn to produce corn starch, then processing that corn starch to yield corn syrup which is almost entirely glucose, and then adding enzymes which change the glucose into fructose. The resulting syrup (after enzyme conversion) contains approximately 90% fructose and is HFCS 90. To make the other common forms of HFCS (HFCS 55 and HFCS 42) the HFCS 90 is mixed with 100% glucose corn syrup in the appropriate ratios to form the desired HFCS. The enzyme process which changes the 100% glucose corn syrup into HFCS 90 is as follows:

1. Cornstarch is treated with alpha-amylase to produce shorter chains of sugars called oligosaccharides.
2. Glucoamylase breaks the sugar chains down even further to yield the simple sugar glucose.
3. Xylose isomerase (aka glucose isomerase) converts glucose to a mixture of about 42% fructose and 50–52% glucose with some other sugars mixed in.

While inexpensive alpha-amylase and glucoamylase are added directly to the slurry and used only once, the more costly glucose-isomerase is packed into columns and the sugar mixture is then passed over it, allowing it to be used repeatedly until it loses its activity. This 42–43% fructose glucose mixture is then subjected to a liquid chromatography step where the fructose is enriched to approximately 90%.

The 90% fructose is then back-blended with 42% fructose to achieve a 55% fructose final product. Most manufacturers use carbon absorption for impurity removal. Numerous filtration, ion-exchange and evaporation steps are also part of the overall process.

The units of measurement for sugars including HFCS are degrees Brix (symbol °Bx). Brix is a measurement of the mass ratio of dissolved sugars to water in a liquid. A 25 °Bx solution has 25 grams of sugar per 100 grams of solution (25% w/w). Or, to put it another way, there are 25 grams of sugar and 75 grams of water in the 100 grams of solution. The Brix measurement was introduced by Antoine Brix.

When an infrared Brix sensor is used, it measures the vibrational frequency of the high-fructose corn syrup molecules, giving a Brix degrees measurement. This will not be the same measurement as Brix degrees using a density or refractive index measurement because it will specifically measure dissolved sugar concentration instead of all dissolved solids. When a refractometer is used, it is correct to report the result as "refractometric dried substance" (RDS). One might speak of a liquid as being 20 °Bx RDS.

This is a measure of percent by weight of total dried solids and, although not technically the same as Brix degrees determined through an infrared method, renders an accurate measurement of sucrose content since the majority of dried solids are in fact sucrose. The advent of in-line infrared Brix measurement sensors have made measuring the amount of dissolved HFCS in products economical using a direct measurement. It also gives the possibility of a direct volume/volume measurement.

Recently an isotopic method for quantifying sweeteners derived from corn and sugar cane was developed by Jahren et al. which permits measurement of corn syrup and cane sugar derived sweeteners in humans thus allowing dietary assessment of the intake of these substances relative to total intake.