GREAT REVIVAL of the TOPIC!!
Would a 150F mash at 1.5 qt/lb for 1 - 1.5 hrs help me get it drier?
Yes, a rest at 150F allows Alpha to release more glucose than sweet tasting, nonfermenting types of sugar. The temperature is used by distillers due to the high amount of glucose released by Alpha during liquefaction and saccharification. Glucose is simple sugar that yeast enjoys the most. Ensure that mash pH favors Alpha.
When malt is spent or rested at a low temperature it might take 1 - 1.5 hours for saccharification to occur. The length of time required for saccharification to take place is annotated on the spec sheet that comes with malt. After 30 minutes do a starch test. If the sample is blue/black thin down the mash a little and test after 15 minutes. If the sample remains blue/black check in another 15 minutes. If the sample remains blue/black after an hour welcome to starch carry over because Alpha was beaten to death somewhere along the line and denatured.
Alpha is the enzyme responsible for liquefaction and saccharification. When Alpha is active glucose is released from simple starch, amylose. The higher the rest temperature less glucose is released and more sweet tasting, nonfermenting types of sugar are released. The higher the temperature the less fermentable wort is and the beer will be on the sweet side.
About mash thickness. The thicker mash is when resting at a temperature that activates a particular enzyme, the longer the life span of the enzyme. A thick mash is used with the decoction method to preserve enzymes due to the length of time each step of the process takes. Mash is thinned out at the end to make lautering easier by reducing viscosity after enzymes have done their work.
Dryness, body and mouthfeel are tied in with conversion, dextrinization and gelatinization. This is where it starts to become complicated. During conversion at optimum temperature 145F Beta activates. Beta converts glucose released by Alpha during saccharification into fermentable, complex types of sugar. Liquefaction, saccharification and conversion takes place at the same time. After Beta denatures Alpha continues to release highly fermentable glucose until the enzyme denatures or until all of the starch becomes liquefied. When all that stuff happens wort contains a lot of fermentable, complex sugar and simple sugar, glucose which yeast rips up during primary fermentation cranking up ABV. Now here's the catch. When conversion occurs secondary fermentation is a given due to yeast only being able to burn simple types of sugar during primary fermentation leaving fermentable, complex sugar alone for awhile. During secondary fermentation yeast absorbs maltose and an enzyme in yeast converts the complex sugar back into glucose which is expelled back through the walls of the cell. The glucose is used for fuel and gravity drops close to expected FG. When conversion occurs beer doesn't require priming sugar or injecting with CO2 for carbonation. Beer naturally carbonates during conditioning when yeast converts maltotriose into glucose which becomes fuel and the CO2 released naturally carbonates the beer. Natural carbonation is much finer than artificial carbonation. During conditioning gravity falls to expected FG, the beer clears without fining or filtering and malt character increases and rounds out.
Now, here's the problem. When liquefaction, saccharification and conversion happens beer lacks body and mouthfeel and will dry and thin out during fermentation and conditioning because we left out dextrinization and gelatinization.
Amylopectin and limit dextrin are responsible for body and mouthfeel in beer. Amylopectin is hard, heat resistant, complex starch that makes up the tips of malt, it is the richest starch in malt. Contained within amylopectin is limit dextrin which are tasteless, nonfermenting types of complex sugar responsible for body and mouthfeel in beer. Now, here's another catch. To take advantage of the starch mash has to be boiled to burst the starch. When the boiling mash is added back into the main mash the temperature increases and enzymes activate, in this case the enzyme is Alpha. During dextrinization Alpha liquefies amylopectin and releases A and B limit dextrin, at the same time the mash jells up during gelatinization due to pectin. When the steps are omitted beer lacks richness and dries and thins out during fermentation and conditioning.
When infusion methods are used the temperatures aren't high enough to cause enough starch to burst before Alpha denatures. The starch is noticeable in spent mash. It is the small, white particles.
When wort is above 1065 gravity yeast sometimes skips reproduction, it's great that the gravity dropped to 1012!!
I hope this stuff helps a little bit with understanding what happens.