After watching the vid and scanning that document I have a number of thoughts to share despite no practical experience of the options.
1) comment on vid re sprinkling dry yeast directly claims higher cell death rate that when reydrated first. That doesn't make rational sense since you are sprinkling it either way. If true you'ld need some other factors in play or the vid 'cheats' by not making fair comparisons: temp, access to air, stir v non-stir perhaps. Since advice is one can use hot wort then the wort itself shouldn't be the limiting factor.
2) Any benefit to prior hydration can only be by retaining more active living cells than using it dry and directsince yeast replication rate is double every 90mins average you'ld have to be losing 3/4 of the original cell mass to delay your fement by more than 3-4hrs - which you wouldn't really notice.
3) Comment in the article about benefit of hoppy wort to keep other microorganisms suppressed probably accounts for advice to only rehydrate first for 30-odd mins total. Factors I haven't looked up include effectiveness of campden tabs to suppress bacteria in wine making and how fast the first few % alcohol is produced and what % is required to supress those bacteria.
4)Rehydration of cells is a case of osmosis - fluid movement through a semi-permeable membrane (like soaking dried beans or prunes etc) here the cell wall is the membrane and speed of osmosis is based on the relative concentrations of fluids each side (osmotic pressure) - so the more dilute the fluid you hydrate in the faster the process except that without substrate any cell replication will be limited to reserves held within the cells. You might activate them quicker but you won't get many iterations of replication.... but then again you won't in 30 mins anyway.
5) Q10 - this is a general expression for chemical processes stating that for every 10C rise in temp chemical processes double in speed (assuming factors such as exothermic reactions have heat removed, products aren't toxic to the reaction and so forth). So having your rehydration fluid at the max temp the organisms can survive (healthily) will generally max the speed of it all happening.
6) Active living organisms generally have narrow temperature windows for survival BUT those are a factor of temperature and time (you can survive a few mins in a freezer but not hours or days. You can survive a sauna for hours but not weeks). Surgical sterilisation takes temps of say 130C wet steam under pressure to effectively kill all spore forms. Otherwise one might be inclined to ferment at 40C <s>
7) the written article describes the basics of yeast culture - providing O2, sugar, nutrients, keeping alcohol/metabolic waste down. One could imply from that that further improvement could be made by hydrating in a larger volume, stirring more often to release CO2, maintaining ideal temperature (I'd guess circa 37C = average mammal body temp), calculating & maintaining minimum good nutrient and sugar substrate levels and effective sterility to avoid contaminants. Start your rehydration with all those factors and pitch 24hrs later with a theortetical 65,535 times your starter cell numbers! Or just chuck the stuff into the wort and don't worry about it because it really can't make more than a day's difference.
<Confused? You won't be after the next episode of Soap>
pgk
