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__Corn Syrup: What it is and What That Means, From Past to Present__

__Introduction__

Up until around the beginning of the 20th century, the word sugar was synonymous with sucrose- a natural sugar obtained from many different sources. However, in current times, the sugars and the compositions of the sugars in the food we eat aren’t as obvious. What lead to this major shift in production of sugary foods in the nation and the way we think about our these foods all revolves around the desire and necessity for our bodies to have sugar and the different ways people and production have found to give it to us.

In the early 1800s, the wars fought in the name of Napoleon Bonaparte managed to hinder the import and export of sucrose. It is believed that this gave Gustav Kirchhoff the thought of engineering sugars other than sucrose [1]. Whatever the cause, in 1811, Kirchhoff, better known for his work with electrical circuits, spectroscopy, and black body radiation, published a paper providing a method of hydrolyzing starch to create sugar [2]. This method is the backbone of what would eventually become a multibillion dollar industry.

Starch, along with cellulose and glycogen, is a polysaccharide of many glucose molecules linked together in specific patterns and arrays by dehydration synthesis (specifically called a glycosidic linkage) [3] [4]. It is also the main storage unit for energy in plants. This being the case, many plants could be chosen to remove the starch from and apply the fruits of Kirchhoff’s labor to. Corn was a desired choice to extract starch from because of the high content the plant had and the sheer amount of corn available [2]. The most popular candidate for Kirchhoff’s process, as current times would tell you, turned out to be a success.

__The Creation of Corn Syrup__

First employed in the late 19th century until 1938 [5], corn syrup was created from the processing of corn starch by acid hydrolysis. The processing of starch via acid hydrolysis required dilute hydrochloric acid added to corn starch soaked with water [6] [7] [8]. Then, the temperature and pressure of the mixture are both raised to increase the reaction yield. Even though the reaction was placed under conditions so that the maximum possible yield was obtained, it was only about 18% efficient [1]. This 18% glucose solution takes spins on centrifuges and passes through ion exchange and carbon adsorption columns to remove impurities and partially evaporated in what is often simply called purification. This increases the amount of glucose to about 42%, with other sugars comprising the rest of the solution [1]. This low yield was not a very favorable quality of the solution that would take the food production industry by storm.

The main focus now shifted to developing another method that would increase the yield of corn syrup made. This new method, called enzyme hydrolysis, followed the same premise of breaking the glycosidic linkages of corn starch. As implied by the name, enzyme hydrolysis uses enzymes, α-amylase and γ-amylase. The enzyme, α-amylase, naturally cleaves the bonds via hydrolysis to make smaller oligosaccharides, usually the disaccharide maltose. Those oligosaccharides are then broken into glucose molecules by the enzyme γ-amylase [6] [9]. The yield of this reaction was more than twice as high as acid hydrolysis, measuring to around 96% efficient [1]. After refining, the corn syrup is now ready to be used in food with a concentration somewhere between 98% and 100% glucose [1]. The final product can also be called glucose syrup, in honor of the sugar that comprises most of the solution.

__Pros of Corn Syrup__

By the early 20th century, corn syrup was easier for manufacturers to use in production and quickly began to replace sucrose. The different properties of this different carbohydrate made it better suited for use in the production of many foods. Sweets, such as ice cream, became smoother and tasted better because of corn syrup’s ability to become gooey instead of hard when subjected to such low temperatures. Another problem that corn syrup was able to solve didn’t involve the production of food, but the preservation of it. Canned fruit was commonly preserved with sugar water (sucrose) or, less commonly, with brine solution (salt). Obviously the brine solution made the canned fruit salty, but the problem came from the sucrose solution. Primarily, sugars with less glycosidic linkages are sweeter to the taste because they are less hindered from fitting in the receptors in our tongue. However, depending on the sweetnesses of the sugars that make up an oligosaccharide, that can vary. For example, sucrose is about 1.33 times sweeter than glucose [3]. So, with corn syrup being roughly 23-29% water [4] [10]- water having a sweetness of 0- then sucrose is about 1.66 times sweeter than corn syrup. Replacing the sucrose with corn syrup made canned fruit more edible while creating the canning procedure that we currently use to this day.

__Cons of Corn Syrup__

Although the decreased sweetness of corn syrup was an attractive quality for canned fruit, for other products to be as sweet as they were when using sucrose, more corn syrup would have to be used. So, although corn syrup fit into the manufacturing business well, more of it would have to be used compared to sucrose. If corn syrup could somehow be made sweeter, less of it would need to be used and costs of production would decrease. This breakthrough didn’t come until 1957, when Richard O Marshall and Earl R. Kooi conceived high fructose corn syrup [5]. However, this breakthrough only proved that a sweeter corn syrup was possible. Despite the magnitude of this breakthrough, this method of producing high fructose corn syrup wasn’t even adopted for mass production in hopes that a better method would be found [6].

__Creation of High Fructose Corn Syrup__

From 1965-1970, the industrial process for creating high fructose corn syrup was developed by Dr. Y. Takasaki of the Agency of Industrial Science and Technology of Ministry of International Trade and Industry of Japan [6]. High fructose corn syrup is defined as any corn syrup in which the glucose and fructose ratios have been chemically altered by the work of enzymes. The first high fructose corn syrup to be mass produced was HFCS-42. This high fructose corn syrup has a sugar content of about 42% fructose, 53% glucose, and 5% other sugars and impurities [10] [11] [12]. Starting from 100% glucose syrup, glucose isomerase, another enzyme that converts glucose into fructose, is added. To increase the yield of the reaction to about 42% efficiency [5], magnesium metal is also added. Although this finally creates HFCS-42, there are more steps to creating the most common high fructose corn syrup, HFCS-55.

Picking up where we left off, some of the HFCS-42 will then be converted to one of two higher-order fructose solutions, HFCS-80, HFCS-90, or HFCS-95. HFCS-95 has a 95% fructose, 4% glucose concentration and 1% other sugars, HFCS-90 has a 90% fructose and 10% glucose sugar content, and HFCS-80 has an 80% fructose and 18% glucose sugar content, with about 2% other sugars [4]. Liquid chromatography is used to create the necessary concentrations of both glucose and fructose for each variety [5] [12]. Lastly, a higher-order fructose corn syrup is mixed with HFCS-42 to create HFCS-55 [6]. HFCS-80 is mixed with HFCS-42 in a ratio of about 50:99, HFCS-90 is mixed with HFCS-42 in a ratio of about 100:283, and HFCS-95 is mixed with HFCS-42 in a ratio of about 100:327 [12]. The final result is a high fructose corn syrup that is composed of 55% fructose, 42% glucose, and about 3% other sugars and impurities [12]. It is HFCS-55 that is most often used in the food production industry [4] [13].

With manufacturers able to make HFCS-80, HFCS-90 and HFCS-95, it would seem more effective to convert all of the HFCS-42 into HFCS-95 and use it in the production of goods. Instead, HFCS-55 is the most favorable blend simply because its sweetness is closest to that of sucrose [12]. This is because fructose is roughly 1.75 times sweeter than sucrose [3] [6] [10]. With most of the sugar content being fructose, the presence of water, once again, lowers the overall sweetness of the solution to equal that of sucrose. Discerning the numerical sweetness of any high fructose corn syrup that doesn’t have a fructose to glucose ratio of about 1:1 is more difficult because of the 91g/100g water solubility of glucose and the 4g/g water solubility of fructose [4]. Depending on the degree of saturation of fructose in the solution, the sweetness can change dramatically. However, it is certain that HFCS-80, HFCS-90 and HFCS-95 are all sweeter than sucrose and less sweet than fructose. Because sucrose had been the sweetest and most used sweetener in production until the arrival of high fructose corn syrup, it was easier to continue using sweeteners of similar sweetness than to start using these sweeter fructose syrups on a regular basis [4].

__Pros of High Fructose Corn Syrup__

In the mid 80s, the relatively new high fructose corn syrup began rapidly replacing sugars used in the production of consumables. Still being a liquid solution, high fructose corn syrup was easily incorporated into any food industry that had already been using corn syrup. Also, with HFCS-55 being as sweet as sucrose [12], less high fructose corn syrup in comparison to corn syrup. Only having to use 75% as much HFCS-55 as glucose syrup and a low cost of production further encouraged the incorporation of high fructose corn syrup [14].

__Cons of High Fructose Corn Syrup__

As high fructose corn syrup has now become a commonplace ingredient in many different foods, it brings up concerns about the safety of using it as an ingredient in the production of foods. Remembering that sucrose is the sugar that corn syrups, specifically high fructose corn syrup, are replacing, comparing them to sucrose would be ideal for figuring out the change in health habits [10]. It just so happens that despite the many tests that have been conducted, no concrete evidence proving that high fructose corn syrup is detrimental to one’s health has been found [14]. In comparison, the most commonly used high fructose corn syrup, HFCS-55, and sucrose are almost identical. HFCS-55 is close to the 1:1 ratio of fructose to glucose that sucrose has [10]. High fructose corn syrup also has small amounts of other sugars, including sucrose, and water in it. Furthermore, the fructose and glucose from both sources are broken down the same way in the human body.

As high fructose corn syrup does have more fructose knowing how the body manages fructose is helpful in discerning what the effects of the extra fructose would be. When absorbed from the small intestine, fructose, glucose, and galactose, the final dietary carbohydrate, are all aided into the liver by glucose transporter 2. After fructose is in the liver, there are some options that the body has as far as how the fructose is handled.

Much in the same fashion as glucose, its chemical isomer, fructose, can create the same products as glucose and contribute to the metabolic pathway [15]. However, furctose is only phosophoylated during the energy investment phase of fructolysis and, after breaking, the unphosphorylated product is phosphorylated to give the same products that would be formed by glycolysis [16]. These products can then follow the same metabolic pathway as glucose [15].

Image 1: A flow chart of the metabolic pathways of fructose and glucose. [16]

The next option for fructose deviates after the energy investment stage. Once fructose splits into dihydroxyacetone phosphate and glyceraldehyde, dihydroxyacetone phosphate can be isomerized to glyceraldehyde 3-phosphate by triophosphate isomerase [16]. The glyceraldehyde formed can also be converted into glyceraldehyde 3-phosphate by glyceraldehyde kinase. The formed glyceraldehyde 3-phosphate is able to contribute to the formation of glycogen and may actually be better for allowing the creation of glycogen than glucose.

The final, and least likely, option for fructose metabolism deviates in the way the products of energy investment are handled. The formed glyceraldehyde and dihydroxyacetone phosphate are both converted to glycerol 3-phosphate [16] [17]. Glyceraldehyde is first phosphorylated by glyceraldehyde kinase and adenosine triphosphate and then acted upon by glyceraldehyde 3-phosphate dehydrogenase [16]. Dihydroxyacetone phosphate is reduced by glycerol 3-phosphate dehydrogenase [17]. When the phosphate group is removed from glycerol 3-phosphate, glycerol, the backbone of triacylglycerol, fat, is made. This final option contributes to the fat content of the body [17].

This final option is not exclusive to the metabolism of fructose, however. As glucose is very close in composition to fructose, it can also use the last pathway to store its energy as fat when the previous two pathways have been exhausted [15][16]. This means that high fructose corn syrup does not necessarily contribute to bad health habits and diseases any more than sucrose does. However, because of the massive panic over that possibility, the corn refiners association has come up with a corn syrup that can do what high fructose corn syrup is suspected of doing.

__Creation of High Maltose Corn Syrup__

Image 2: The two structures of maltose, composed of two glucose molecules. [18]

Looking for another way to sweeten consumables, high maltose corn syrup was born. This new corn syrup was actually already being produced in the process of making glucose syrup. Starting with corn starch, the only first step of enzyme hydrolysis is applied- using β-amylase to convert much of the starch into maltose [9]. By repeating this process and purifying the product by carbon adsorption and ion exchange, high maltose corn syrup is achieved. The usual varieties of high maltose corn syrup are HMCS-50, HMCS-65, and HMCS-70, with the remaining percentages of each mainly consisting of maltotriose, with glucose and few higher order sugars in lower percentages [19]. Having a solubility of 108g/100g water, maltose is more soluble in water than glucose is. This means that the sweetness of high maltose corn syrup nears the sweetness of crystalline maltose faster as it’s concentration get higher. It is, therefore, unnecessary to create solutions of high maltose corn syrup around 100% maltose.

__Cons of High Maltose Corn Syrup__

Although high maltose corn syrup is now beginning to replace high fructose corn syrup, it is primarily because of the lower cost of production and public concern surrounding high fructose corn syrup [14]. One disappointment is of the new syrup is that high maltose corn syrup is nowhere close to as being as sweet as its fructose counterpart [3]. Maltose is only a third as sweet as sucrose, meaning that all versions of high maltose corn syrup are less sweet than sucrose. In fact, glucose is 2.25 times as sweet as maltose [3]. This means that more high maltose corn syrup must be used to provide the same amount of sweetness as sucrose and even glucose syrup. The low cost of production of high maltose corn syrup helps of offset some of the costs of having to use more- keeping it in use in production of some consumer goods [14]. Also, because it breaks down into two glucose molecules when metabolized [20], it actually has a greater chance of contributing more to the storage of fat than high fructose corn syrup [21]. The only positive aspect of high maltose corn syrup being that it isn’t high fructose corn syrup, its production was literally a step or two backwards. The next corn syrup produced will need to have sucrose sweetness without getting such a bad reputation with the general public.

__Discussion__

The use of corn syrup has been central to the United States’ food production industry since its creation. The improvements made to the original formula have had both negative and positive aspects. Unfortunately, public opinion has become slanted against what could be argued as the best version of corn syrup produced to this day. Whether this setback halts the use of corn syrups or spurs the next iteration to outdo high fructose corn syrup is a question of the creative minds available for the task. With our history, and what could be called an addiction, to corn syrups, I believe that there will be another part to this story in the near future.

__References__

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