Tuesday, April 11, 2006

High fructose corn syrup

[Michael Pollan's new book, on "Fresh Air"...]
High fructose corn syrup (HFCS) is a newer and sweeter form of corn syrup. Like ordinary corn syrup, it is made from corn starch using enzymes. The process of developing HFCS was discovered by Japanese researchers in the 1970s.

By increasing the proportion of fructose, a syrup is produced which is more comparable to an ordinary sugar (sucrose) syrup in its ratio of fructose to glucose and in its sweetness. This makes it useful to manufacturers as a possible substitute for ordinary sugar (sucrose) in soft drinks and other consumer goods.

Through processing, the fructose content can be increased to 55%, yielding a product that has the same sweetness as sucrose, or higher. Common commercial grades of high fructose corn syrup include fructose contents of 42%, 55% (used in soft drinks and equivalent to caster sugar), or 90%.

High-fructose corn syrup (HFCS) is produced by processing corn starch to yield glucose, and then processing the glucose to produce a high percentage of fructose.

First, cornstarch is treated with alpha-amylase to produce shorter chains of sugars called polysaccharides.

Next, an enzyme called glucoamylase breaks the sugar chains down even further to yield the simple sugar glucose.

The third enzyme, glucose-isomerase, converts glucose to a mixture of about 42 percent fructose and 50-52 percent glucose with some other sugars mixed in. While alpha-amylase and glucoamylase are added directly to the slurry, glucose-isomerase is packed into columns and the sugar mixture is then passed over it. 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. Numerous ion-exchange and evaporation steps are also part of the overall process....

Fructose produces lower levels of the hormones leptin and insulin than glucose. Raising leptin and insulin levels trigger the feeling of "fullness" while eating. The level of the hormone ghrelin remains higher with consumption of fructose than it does with glucose. Ghrelin appears to control the feeling of "hunger". This double change in normal production of these hormones results in a slower decrease in appetite and a tendency to consume more than if glucose were to be used. Thus more is consumed to get the same "full" and "satiated" feeling and the total caloric intake is greater. Additionally, the level of blood triglycerides shows a rapid and prolonged elevation after consuming fructose as opposed to glucose. JCEM 2/24/2004

The delayed decrease of the hormone ghrelin has been shown in obese subjects but not in normal weight subjects. This means that chronic consumption of fructose may actually be preconditioning the metabolism of a normal weight individual to behave like an obese individual's metabolism. JCEM 11/2/2004

High triglyceride levels are believed to be linked to clogging of the arteries and may increase the risk of heart attack or stroke. They may even be more important for determining the risk of heart disease than cholesterol.


No comments: