Kit instructions are written to make their preparation as simple as possible. Pitching dry will generally work but it far from best practice and will not give you the best results. When pitching dry, 50% will die on first contact with your wort as the yeast cannot distinguish nor therefore regulate what passes through their delicate cell walls. This means you will have under-pitched which Wyeast state can cause;
excess levels of diacetyl,
an increase in higher/fusel alcohol formation,
an increase in ester formation,
an increase in volatile sulphur compounds,
high terminal gravities,
stuck fermentations and
an increased risk of infection.
Do you still maintain that pitching dry is fine?
Thanks for this info, I will rehydrate the yeast in future. It seems odd that two batches in a row have 'stuck' at 1020 when it has worked for me in the past but maybe this explains it. I'll certainly try it next time.
There is no chance that using yeast which didn't come with the kit could be the problem?
Is this a good example of how to rehydrate dry yeast?
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Preparing Dry Yeast
Dry yeast should be re-hydrated in water before pitching. Often the concentration of sugars in wort is high enough that the yeast can not draw enough water across the cell membranes to restart their metabolism. For best results, re-hydrate 2 packets of dry yeast in warm water (95-105°F) and then proof the yeast by adding some sugar to see if they are still alive after de-hydration and storage.[/FONT]
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If it's not showing signs of life (churning, foaming) after a half hour, your yeast may be too old or dead. Unfortunately, this can be a common problem with dry yeast packets, especially if they are the non-name brand packets taped to the top of malt extract beer kits. Using name brand brewers yeasts like those mentioned previously usually prevents this problem. Have a third packet available as back-up. [/FONT]
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Figure 34 and 35: Dry yeast that has been re-hydrated and the same yeast after proofing. [/FONT]
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Re-hydrating Dry Yeast
1. Put 1 cup of warm (95-105F, 35-40C) boiled water into a sanitized jar and stir in the yeast. Cover with Saran Wrap and wait 15 minutes.
2. "Proof" the yeast by adding one teaspoon of extract or sugar that has been boiled in a small amount of water. Allow the sugar solution to cool before adding it to the jar.
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3. Cover and place in a warm area out of direct sunlight.
4. After 30 minutes or so the yeast should be visibly churning and/or foaming, and is ready to pitch.
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Note: Lallemand/Danstar does not recommend proofing after rehydration of their yeast because they have optimized their yeast's nutrional reserves for quick starting in the main wort. Proofing expends some of those reserves.[/FONT]
Thanks