Manufacturing of High-Fructose Corn Syrup

High-Fructose Corn Syrup (HFCS) is an extra sweet, inexpensive sweetener used mostly in soft drinks and fruit juices.

Corn is the primary source of high fructose corn syrup in the US. High fructose corn syrup is a liquid alternative sweetener to sucrose that is made from corn, the “king of crops”. It is a caloric sweetener, made from ordinary corn starch, which substitutes for sugar in a wide range of manufactured products.

Corn starch composed of glucose molecules of infinite length, consists of amylose and amylopectin and requires heat, caustic soda and/or hydrochloric acid plus the activity of three different enzymes to break it down into the simple sugars glucose and fructose present in HFCS.

The production of HFCS and corn wet milling are typically an integrated process. The wet milling process separates the corn kernel into its four principal components: the germ, hull, gluten, and starch. High fructose corn syrups, as well as other corn sweeteners, utilize the corn starch slurry produced by the wet milling process as their basic input.

An industrial enzyme, α-amylase produced from Bacillus spp., hydrolyzes corn starch to short chain dextrins and oligosaccharides. Bacterial α-amylases catalyze the hydrolysis of α-1,4 glucosidic linkages and act in a random but reproducible manner to reduce the polysaccharide molecular weight. Enzymatic liquefaction requires precise control of operating conditions like percentage of solids, temperature, time, pH and calcium level to ensure efficient hydrolysis, process economics and easier downstream processing operations.

A second enzyme, glucoamylase (also called amyloglucosidase),produced from fungi such as Apergillus, breaks dextrins and oligosaccharides to the simple sugar glucose.

A glucoamylase dosage is added to produce a maximum dextrose level in 1-4 days. Reaction time is inversely related to dose, so if a given dose yields maximum dextrose in 4 days, doubling or quadrupling the dose will reduce reaction time to 2 days or 1 day, respectively.

The product of these two enzymes is corn syrup also called glucose syrup. The third and relatively expensive enzyme used in the process is glucose isomerase (also called D-glucose ketoisomerase or D-xylose ketolisomerase),that converts glucose to fructose.

Fructose is superior to all nutritive sweeteners and humectants in controlling water in frozen system. Its water activity is low as compared to sucrose, sorbitol, dextrose, mannitol, etc. which makes it a better preservative.

Manufacturing of High-Fructose Corn Syrup 

Production of High Fructose Corn Syrup

High fructose corn syrup is a low calories sweetener commonly used in beverages, desserts and other sweet foods.

To make high fructose syrups, corn starch is first separated from other corn by products by wet milling. The wet milling process begins with steeping clean corn in water from 30 to 35 hours at 117 to 127 °F to soften kernel. 

Steeped corn then is cracked by use of an attrition mill to separate the germ and release about one-half of the endosperm (prime starch fraction).

Next the starch is digested with mineral acid and amylose to form glucose. The enzyme glucose isomerase then used to covert glucose to fructose. With the biotechnological achievement of immobilization of the enzyme, shallow beds of the immobilized enzymes can convert glucose to fructose.

The process is called saccharification. Conditions for the saccharification are 55-60 °C, pH 4.0 -4.5 and a building time of 24 – 90 hours depending upon the amount of glucose amylase used and production scheduling.

A syrup containing 42% fructose, 52% unconverted dextrose and about 6% of oligosaccharides is the first product of this process.

Through chromatographic enrichment, 55 and 90% high fructose syrups can then be produced.
Production of High Fructose Corn Syrup

High Fructose Corn Syrup

High Fructose Corn Syrup
The commercial value of high fructose corn syrup is based on the increased sweetness of the High Fructose Corn Syrup (HFCS) compared to the starting material glucose obtained from starch. On sweetness comparison basis glucose is only about 70% as sweet as sucrose whereas fructose is sweeter compared to sucrose to the extent of 20–60% depending conditions used.

The abundant supplies of cheap corn in USA, as well as efficient processing techniques and valuable by-products such as corn oil and protein provide the basis for the low cost manufacture of HFCS. Typical syrups made from starch contain a mixture of glucose, fructose, and other saccharides. The equilibrium limitation of the enzymatic conversion of glucose to fructose, as well as sweetness and manufacturing cost restrictions, led to the development of fructose syrups containing 42% fructose on a dry basis to replace liquid sucrose in many food applications.

The first stage in HFCS production is the hydrolysis of polymer corn starch containing about 74% amylopectin and 26% amylase to monomeric glucose.

In the later stages of HFCS production, large scale chromatographic techniques are use to produce syrups with the various proportions of fructose and glucose. The degree of isomerisation (DI) is the percentage of sugars dry basis, 52% glucose and 6% higher sugars. It is common practice to incorporate the DI value in the product description.

Ultra high fructose corn syrup (UHFCS) is generally restricted to those syrups having a DI value greater than 50. Sometimes ultra high fructose glucose syrup or second generation HFCS are used instead of HFCS.

There are three main stages involving three different enzymes may be identified in the manufacturing process of HFCS. These include
Liquefaction of starch
Saccharification
Isomerisation

High Fructose Corn Syrup