So I had an entire, HUGE post about ester flavorings typed up last night, then I accidentally deleted it all (apparently, the Shift+Up, Backspace sequence is really easy to execute on my girlfriend’s computer). I was trying to figure out if there was some correlation between chain length and flavor. I didn’t really get anywhere. So it’s probably a good thing it never got published, eh?
How about a little something on the chemistry and history of corn syrups?
I realized last night that I have no idea what the hell corn syrup actually is. Obviously it contains sugars, and obviously high-fructose corn syrup contains a lot of fructose, but what of the rest of it? Answer: corn syrup is more the process that makes it than one compound in particular.
The challenge in making corn syrup is separating starch, the ultimate sugar-bearing polymer, from other proteins and fats in the corn. The first step, “steeping,” involves soaking the kernels in warm water and allowing them to swell. Swelling causes an initial release of starch and denatures the proteins that hold things together inside the kernel. The corn is then ground and sent off in a water slurry to germ separators, which use solvent extractions and centrifuges to separate corn oil (fats) from starches and proteins.
At this point the starches are still held together by corn proteins, so a second grinding mechanism called an “impact mill” or “attrition-impact mill” is used to obtain a loose suspension of proteins and starch, “mill starch.” The mill starch is centrifuged multiple times to separate out heavier proteins, giving at last pure, unmodified corn starch.
The corn starch is turned into corn syrup by means of hydrolysis by either acids or enzymes. Starches are (usually solid) polysaccharides, and hydrolyzing them into monomers gives sugary, liquidy syrups. The neat thing is, by modulating what enzymes are used, how long they are allowed to act on the starch, etc. one can produce syrups of varying sweetness! Hydrolyzing enzymes can only produce a limited number of sugars (dextrose and maltodextrins [oligosaccharrides of dextrose]), but the use of glucose isomerase to convert glucose (read: dextrose) into fructose has led to the widespread use of the sweeter high-fructose corn syrups. Glucose is a very fermentable sugar, so corn syrups of pure glucose are often passed on for alcohol fermentation. In addition, many of the waste products of the corn refining process can be used for other applications. Check it out!