Mash temp for starter wort
#1
Posted 25 July 2009 - 06:36 AM
#2
Posted 25 July 2009 - 09:23 AM
#3
Posted 25 July 2009 - 09:26 AM
#4
Posted 25 July 2009 - 09:36 AM
#5
Posted 25 July 2009 - 10:22 AM
Edited by JKoravos, 25 July 2009 - 10:27 AM.
#6
Posted 25 July 2009 - 10:28 AM
#7
Posted 25 July 2009 - 10:41 AM
#8
Posted 25 July 2009 - 11:57 AM
Through the years, I have frequently heard references to adding yeast to the boil as a nutrient, but I've never heard an explanation of how or why it works. Can you provide one?Servo is the caddillac of yeast nutrient, but a bit of bakers' yeast added to boil will help, too.
#9
Posted 25 July 2009 - 12:10 PM
www.whitelabs.com/beer/Yeast_Nutrition_Article.pdfpage 3*doesn't touch on bakers yeast though just thier productThrough the years, I have frequently heard references to adding yeast to the boil as a nutrient, but I've never heard an explanation of how or why it works. Can you provide one?
#10
Posted 25 July 2009 - 12:42 PM
And it doesn't really address using any kind of yeast as a nutrient, except when it's grown with the special nutrients they mention. So, throwing old brewing yeast in may or may not do anything.www.whitelabs.com/beer/Yeast_Nutrition_Article.pdfpage 3*doesn't touch on bakers yeast though just thier product
#11
Posted 25 July 2009 - 01:30 PM
The hypothesis that I heard was tied together autolysis/yeast are cannibalistic and one yeast nutrient made of yeast hulls. So if you had some extra yeast, you could thow it in the boil as a homemade yeast nutrient. Unless you add a ridiculous amount, I cannot see any harm.IMHO: Commercial yeast nutrients are so cheap that if you need some boost to your wort, do it right and use a product that is designed to do the job.But then this is homebrewing, where saving are often not measured in pennies or dollars, but in percentage points.zymotThrough the years, I have frequently heard references to adding yeast to the boil as a nutrient, but I've never heard an explanation of how or why it works. Can you provide one?
#12
Posted 25 July 2009 - 05:16 PM
The yeast are using the sugars in the wort for energy, correct? I would think that having more sugars that they can use for energy the more yeast growth there would be. Am I wrong here?fermentability only matters for fermentation, not aerobic yeast growth.
#13
Posted 26 July 2009 - 08:02 AM
You are correct that they use glucose for energy, but their level of growth is dependent on oxygen in a starter. The amount of sugar they will use by the time they've consumed all the oxygen hardly makes a dent in your gravity. Now, if you've got a continuous aeration system, there is a point that you will need to add more sugars, but the difference between a 146F or a 156F fermentability I believe is negligible.The yeast are using the sugars in the wort for energy, correct? I would think that having more sugars that they can use for energy the more yeast growth there would be. Am I wrong here?
#14
Posted 26 July 2009 - 08:24 AM
OK, I'm doing one as a stirplate starter and one as a simple starter. (don't mind the messy workbench, it's usually spotless )So, during aerobic growth they're not using much sugar, but during anaerobic growth they are using only sugar. I'm assuming the sugars they are using during aerobic growth are actually being used in a different pathway then the oxygen. Yes?You are correct that they use glucose for energy, but their level of growth is dependent on oxygen in a starter. The amount of sugar they will use by the time they've consumed all the oxygen hardly makes a dent in your gravity. Now, if you've got a continuous aeration system, there is a point that you will need to add more sugars, but the difference between a 146F or a 156F fermentability I believe is negligible.
#15
Posted 26 July 2009 - 08:44 AM
Yes. This is not my strongest area. I have some nice diagrams of how the yeast cell transfers energy but they are at work. I'll see what I can find out when I am there tomorrow.So, during aerobic growth they're not using much sugar, but during anaerobic growth they are using only sugar. I'm assuming the sugars they are using during aerobic growth are actually being used in a different pathway then the oxygen. Yes?
#16
Posted 27 July 2009 - 09:00 PM
#17
Posted 05 August 2009 - 09:43 PM
I think you've got the idea...Just to clarify... at least for us homebrewers, yeast will never respire aerobically. They will be in an aerobic environment but will always metabolize sugars via fermentation. The reason for this is the high concentration of sugars in the worts we pitch the yeast into. The yeast "sense" the sugar concentration and bypass aerobic respiration even though oxygen is available (a phenomenon known as the Crabtree Effect). They do take up oxygen molecules but they are not used for metabolism. Instead, the oxygen is used for sterol synthesis and cell wall maintenance/growth.Let's say you aerate your starter initially and then let it sit after pitching yeast. The yeast will initially consume the oxygen to prepare their cell walls. During this initial "lag", the yeast do not consume any sugars in the wort. All cell activity is powered by glycogen reserves within the cell. Once the cell wall is prepared, the yeast will begin fermenting the sugars and enter exponential growth. As the yeast use up the oxygen, their environment slowly moves from aerobic to anaerobic (I think this is what you were alluding to above). Any metabolizing of sugars was done only via fermentation.Now, let's say you continuously aerate your starter with a stirplate. This time, the yeast will always be in an aerobic environment. That is, there will always be oxygen available to the yeast. The yeast will take up oxygen to prepare their cell walls and then they will begin fermenting the sugars. Again, all metabolic activity is via fermentation only. This time, while the yeast is fermenting and growing exponentially, they can continue to take up more oxygen for cell wall growth and maintenance. This will result in larger cell counts in the starter.Sorry for the lecture... I just started typing and couldn't stop.So, during aerobic growth they're not using much sugar, but during anaerobic growth they are using only sugar. I'm assuming the sugars they are using during aerobic growth are actually being used in a different pathway then the oxygen. Yes?
#18
Posted 06 August 2009 - 05:40 AM
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