Try grinding your corn to the consistancy of cornmeal. That increases the ability of the grain to absorb water and geletanize the starches.
When initially adding in the alpha-amylase, the pH of the mash should be around 5.8 to 6.0 for maximum activity. A pH below 5.2 or above 7 will produce less than desirable results.
Think of enzymes as having a half life like uranium or other radioactive materials. After x amount of time, half of the enzymes will become denatured, with another half being denatured in another x amount of time till there is very little working enzymes left or the starch has been fully converted. The half life rate depends on temperature, pH, and time.
Generally increasing the temperature increases the activity of the enzyme exponentially while the half life more or less gently decreases provided all other variables are optimum. This is why we mash at higher temps rather than dumping them in at room temp.
Bacterial based alpha-amylase enzymes are somewhat to greatly more thermostable than those derived from malted barley or fungal amylases. This is because all enzymes are essentially large proteins and each species or strain used in their manufacture produces a slightly different enzyme even though they do the same thing. As such, different manufacturers use different microbes and their enzymes will have different optimium parameters. Non-thermostable bacterial alpha-amylase generally shows activity up to 85ºC before it begins to denature with peak activity around 65-70ºC, or around the point where the starch gelatanizes. If it were me, I'd shoot for a 70ºC strike temp and see how it goes. If it works, then kick it up to to 75ºC and finally 80º. Remember, your strike water takes a temperature of approx 10ºC more degrees greater than your target strike temp depending on how much heat your mash tun absorbs upon addition of strike water.
Alpha-amylase should have some free calcium ions in the solution. This helps to stabilize the enzyme and make it work more efficiantly. 2 grams per gallon of anhydrous calcium chloride per gallon of should be sufficiant to accomplish this. That should result in a Ca++ ion content of around 144ppm. Bumping it up to 3 grams per gallon would result in a level of 216ppm. In practical terms, calcium chloride normally comes in the form of a dihydrate so 3 grams should result in somewhere between 144 and 216ppm. Be aware that it is possible to overdose on the calcium chloride which results in the amylase being denatured.
Alpha-amylase should be added in two doses. The first dose is for liquefication purposes during cooking and the second is where the actual dextrinization occurs. One could theoretically add strike water at the proper temperature to achieve a mash temp of about 80 degrees or so, then let it sit in a cooler and cook till the temps drop to ideal temps for the second addition. This will eliminate scorching issues.
When cooking other enzymes may be added to assist in liquefication. One such enzyme is Phytase which will work to neutralize phytic acid which is detrimental to alpha-amylase. Supposedly it also allows alpha to work at a lower temperature. Here is one site that might be useful source of this and other enzymes... http://nutriteck.ca/sslshop/product_inf ... cts_id=145
Mash grain to water ratio comes into play as well. A thicker initial mash helps to stabilize the alpha-amylase enzyme. Industry uses a 30% or so average w/w grain to water ratio. Some references are vauge as to whether the ratio includes or does not include the moisture content of the grain when calculating the ratio. 1 gallon 30% slurry by volume taking consideration of the latent moisture in the grain should consist of approximately 1425g of corn with the remainder being 2739mls water. Converted into pounds/quarts thats 3.13 lbs corn to 2.85 quarts of water or a water to grain ratio of .91 Using plain corn weight, those figures changes to 1250g corn and 2932 mls water or 2.75lbs corn to 3.1 quarts water needed to make one gallon of slurry volume. Remember, you'll use slightly more grain/water than the weight of one gallon of water since corn is more dense than water. In any case a simple 1.25 ratio water to grain ratio should be acceptable which would be 2.5lbs grain to 3.2 quarts of water to make one gallon of mash by volume.
Fortunately glucoamylase or amylogluconase or GA-100 is much simpler to use since it can be used in a simultaneous saccarification and fermentation process. Think whiskey yeast with AG. The only catch is glucoamylase requires a lower pH than malt barley or alpha amylase. Peak activity is normally around pH 4.3 however this is dangerously close to too low a pH for ideal yeast activity. An ideal pH for a mash would be around 4.6. Several acids can be used to accomplish this with industy using hydrochloric or sulfuric acids. In addition, pH buffers can be used such as acetic acid/sodium acetate or citric acid/sodium citrate. The pH buffer sold in 1lb jars to set the pH at 5.2 should not be used with synthetic enzymes since it is too high for the glucoamylase to work properly, however, it is perfect for malted barley.