HSA is a much debated topic among large scale brewers. I once read a study done in Germany where every aspect of the wort was in inert gas. Nitrogen I think. They concluded after the odd fermentations that resulted: oxygen was needed on some level for normal ferments. (The wort was oxygenated using pure o2 on the cold side on the way to the fermenter.)
I would minimize splashing wort that was lower than boiling. You should be right in line with the big boys.
It is very important that you aerate the wort after it has cooled down to yeast pitching temperature There are two reasons for aerating the COOLED liquid:
- undesirable reactions occur between oxygen and some compounds in the wort/must when hot, and
- gas does not dissolve very well in hot fluid.
I'll take some time to review this stuff, but from my initial understandings there are way too many other things to worry about in your brews. I suppose it is best to be as cautious as possible when handling hot/warm wort before fermentation by avoiding agitation.
I fly sparge, and when I drain my lauter tun into my boil pot, the liquid drops about 8" from the end of my drain tube into the boil pot. Until I've drained a gallon or so, the sweet liqour splashes on the bottom of the pot, creating lots of bubbles and foam. Is this splashing a concern, or is HSA only a problem post-boil?
HSA is a problem at any point during the brewing process so yes you could get some by what you describe. I doubt you are getting a noticeable amount as you really need to aerate the wort before you get off flavours. If you are worried about it just extend the tubing from your MLT closer to the bottom of your boil kettle.