Verslag_hydratatie_experimenen.pdf

7/31/2019 Verslag_hydratatie_experimenen.pdf

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Jacques Bertens is a Dutch home brewer for already more than 30 years. During this time many insights in

brewing have changed about which he wrote a large number of publications for the Dutch home scene. Initially

for a regional dutch brewing club, de Roerstok (Tilburg close to LaTrappe brewery) which he also chaired,

later on also in the Dutch and Flemish magazine Proost. Around 1990 Jacques founded the website

Hobbybrouwen.nl which includes a forum (8000 hits per day, 1800 members, 150 members daily online, 100

posts per day). This forum is the largest virtual community for Dutch and Flemish home brewers. Furthermore

Jacques has been a member of the Dutch association for beer judges for more than 20 years.

In the Basic Brewing podcast of April 14th 2011 a request was made to participate in a brewing experiment. The

experiment aimed to determine the effect of hydration of dry yeast and the way of adding yeast to wort on lag-

time before fermentation starts, krausening, apparent degree of fermentation, the final taste of the beer and other

characteristics.

I welcome the opportunity to contribute to this request. Already for quite some years I perform experiments in

this field, not as a scientist but as a home brewer who is interested in the science behind brewing.

In many publications, such as the book Yeast by Chris White and Jamil Zainasheff, it is stated that hydration of

dry yeast is needed for fermenting into a good beer. Many home brewers, including myself have experienced that

just sprinkling the dry yeast onto the wort can also lead to a good beer. In order to experience whether hydrationof dry yeast is really needed for obtaining a better beer I carried out a number of experiments over the last years

which I will describe below

1 - Historic data desktop research

In spring of 2010 I carried out a large desktop research. To this end a web questionnaire was designed in which

Dutch home brewers who are active on the Dutch forum www.hobbybrouwen.nl/forum could enter specific data

on beers they had fermented using dry yeast. Among the parameters asked for was the way of brewing the beer

(e.g. mash scheme, malt bill, percentage sugar), starting and final gravity, type of yeast, whether or not the dry

yeast was hydrated prior to pitching, amount of yeast per liter wort etc. Data of 274 beers were analyzed! For

now I will only focus on the degree of fermentation in relation to whether or not to hydrate dried yeast.

74,5

75

75,5

76

76,5

77

77,5

78

Hydrated Dry

Degreeoffermentation%

Hydrated

Dry

Figure 1

The average degree of fermentation of beers fermented with hydrated yeast was 75.3% (number of observation

was 143) whereas for non-hydrated yeasts this was 77.2% (number of observations 131). This difference was

significant at level of confidence 99 %.

When looking at the difference between yeast types it was shown that for 9 out of 12 yeasts there was a

significant effect of hydration of yeast, hydration leading to lower apparent degrees of fermentation. In case

there were no significant differences the number of observations were often too low (Figure 2)


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60,0

65,0

70,0

75,0

80,0

85,0

Brewferm

Blan

che

B

rewfer

mLa

ger

Brewfer

mTo

p

Coopers's

Ale

Danstar

Notting

ham

Dan

starW

indsor

Fermen

tisSafA

leS-04

Fermen

tisSafA

leS-33

Ferm

entisS

afAleUS

-05

Ferm

entisS

afBrew

T-58

Ferm

entisS

afBrew

WB-

06

Ferm

entisSafL

ager

S-23

DegreeofFermentattion%

Hydrated

Dry

Figure 2

2 - Experiment microscopic observations

Shea A.J. Comfort (Guidelines to Hydrating Active Dry Wine Yeast, & A Recommended Nutrient Regimen)

stated that hydration of dry yeast should not be performed at temperatures below 35C/95F because at these

temperatures hydration would not be optimal. Best results were obtained at hydration temperatures of about

40C/104F because according to Shea this represent the best balance between the water being warm enough tomaintain an ideal elasticity of the yeasts cell membrane as it is being reformed, while not being too hot so as to

start damaging the cell itself.

To verify these observations, experiments were performed in which the effect of hydration temperature on yeast

cell viability and fermentation characteristics was determined.

This experiment was performed in November 2008 using the following set-up;

Sample Treatment

1 3 g of dry Coopers yeast is gently mixed in 100 g water of 40C/104F in which 10 g of sugar was

dissolved

2 3 g of dry Coopers yeast is gently mixed in 100 g water of 30C/86F in which 10 g of sugar was

dissolved

3 3 g of dry Coopers yeast is gently mixed in 100 g water of 40C/104F (no sugar dissolved)

4 Dry Coopers yeast, not hydrated

The weight of water was determined with an accuracy of 0,1 g and the amount of sugar (cane sugar) and yeast

(Coopers) was determined with an accuracy of 0,01 g. After addition of the yeast the solutions were allowed to

cool down to room temperature (19C/66F).

About 30 minutes after hydration the samples were stirred to make them homogeneous and exactly 10 ml of each

sample was added to 680 ml malt extract solution with a starting gravity of 1041 and a pH of 4,96. This stock

malt extract solution contained 0,1 g Wyeast Nutrient and 0,33 ml 20% phosphoric acid per liter solution. The

samples were contained in 1 liter bottles.

In this way every bottle contained 0,3 g dry yeast. The bottles with sample 1 and 2 contained an additional 1 g

sugar coming from the hydration solution (increased starting gravity from 1041 to 1042). To bottle 4 exactly 0,3

g of dry yeast was added at room temperature.


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Shortly after addition of the yeast a 10 ml sample was taken to determine yeast cell viability using methylene

blue staining in combination with bright field microscopy. The sample was diluted with 150 ml water to achieve

the proper dilution. One ml of this diluted sample was stained with 1 droplet methylene blue and evaluated using

a microscope equipped with a counting chamber (Brker Trker). Per sample about 1250 cell were counted.

The following results were obtained:

Sample Viable cells

(%)

1 (40C/104F and sugar) 75

2 (30C/86F and sugar) 71

3 (40C/104F no sugar) 68

The samples were allowed to finish fermentation which took about 6 days at 20 C. The final gravity was

determined using an high accuracy Plato-meter.

Sample starting

gravity(kg/m3)

Final

Plato(P)

Final specific

gravity(-)

Yeast

(g/l)

App. Degree of

Fermentation(%)

1 (40C/104F and sugar) 1042 3,65 1,0146 0,44 65,2

2 (30C/86F and sugar) 1042 3,68 1,0147 0,44 64.9

3 (40C/104F no sugar) 1041 3,62 1,0145 0,44 64,6

4 (room temperature; non

hydrated)

1041 3,70 1,0148 0,44 63,9

The differences between the various treatments (hydration temperature and the presence of sugar) on the final

gravity and the apparent degree of fermentation is very small and not significant. Based on this limited set-up it

can be concluded that both hydration temperature and presence of sugar in the hydration solution do not affect

cell viability and yeast performance.

Sensory evaluation of the fermented worts did not show any pronounced differences.

3 - The big hydration experiment

After publication of the above mentioned results on the hobbybrouwen.nl forum there was quite some discussion

on the ratio yeast to water. In the afore mentioned experiment the weight ratio yeast to water was about 40 times

lower as normally advised by the yeast manufacturers.

Therefor a bigger experimental set-up was carried out in order to verify previous results and to check the effect

of the water yeast ratio. Furthermore the fermented beers were sensorial evaluated to see the effect of the water

yeast ratio. This experiment was carried out December 2010.

In this experiment 6 variations were tested.

Every variation was prepared in a 1 liter bottle. These bottles were filled with exactly 750 ml wort from a home

brew with a starting gravity of 1054. Since the dry yeast was hydrated with different amounts of water, the

bottles were topped with water in order to achieve the same volume in every bottle after hydrated yeast addition.

For this experiment the dry yeast Safale S-04 was used. The yeast was hydrated in water of 27C/81F or

40C/104F at different water-yeast ratios and allowed to hydrate for 30 minutes. In order to avoid cooling of

the water yeast suspension the hydration vessels were placed in water baths set at 27C/81F or 40C/104F.

After 30 minutes the hydrated yeast was quantitatively transferred to the bottles. Fermentis

(http://www.fermentis.com/fo/pdf/Tips-Tricks.pdf) advises to hydrate top fermenting yeast at a temperature

between 25C/77F and 29C/84F.

Photo 1 shows the water bath used.


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Photo 1

The amount of dry yeast added was calculated using Mr Maltys yeast calculator

(http://www.mrmalty.com/calc/calc.html ). According to this tool 0,37 g of dry yeast needed to be added to 750

ml of wort with a starting gravity of 1054. In bottle 5 the yeast was not hydrated in water but added directly to

the wort. In bottle 6 a higher concentration of dry yeast (+25%) was directly added to the wort without hydrationin water. The worts were fermented at room temperature. Fermentation was finished after 14 days and the

fermented wort was bottled using 8 g sugar per liter.

The different experimental varieties and the measured f inal specific gravities and apparent degrees of

fermentation just before bottling are compiled in the table below.

Final gravities were determined using a high accuracy hydrometer.

Bottle Weight

yeast

(g)

Yeast

concentration inbottle(g/l)

Water/yeast

ratio athydration(-)

Temperature

hydration

(C/F)

Final

specificgravity(-)

Apparent

degree offermentation(%)

1 0,37 0,48 6 27/81 1,0123 76,3%

2 0,37 0,48 10 27/81 1,0117 77,5%

3 0,37 0,48 40 27/81 1,0119 77,1%

4 0,37 0,48 40 40/104 1,0121 76,7%

5 0,37 0,48 - - 1,0117 77,5%

6 0,46 0,59 - - 1,0115 77,9%

The results show that the differences between the apparent degrees of fermentation for the different treatments

are very small. Hydration of dry yeast according to instruction of the yeast manufacturers does not lead to higher

degrees of fermentation compared to using other water-yeast ratios or different hydration temperatures.

The lowest degree of fermentation was obtained when using a lower amount of water for hydration then

according the instructions although the differences are small. Hydration at higher temperatures appears to be less

useful for obtaining higher degrees of fermentation. The beer that was fermented with 25% more yeast obtained

the highest degree of fermentation although also here the difference is minor. This beer was also the first one in

which fermentation was visually active by airlock activity.


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About 10 weeks after bottling the beers were sensorial judged by 5 experienced tasters, including myself. The

beers were judged blind in which the order of tasting was randomized. Only after all beers were judged and the

findings were collected, the findings were evaluated.

This evaluation lead to the following results:

all beers were good tasting without any brewing errors or infections.

the difference between the various beers were very small, even smaller then at bottling time the beer hydrated with lowest amount of water was judged as the most fruity the beer with no hydrated yeast appeared to be slightly sweeter.

4 - The effect of hydration on taste

The results from the previous experiment initiated a discussion on the hobbybrouwen.nl forum about what the

effect of hydration on taste of the final beer would be. It already appeared that whether or not hydrating the yeast

did not affect the final degree of fermentation. Since there might be a yeast effect, three different yeasts

(Brewferm Top, Danstar Nottingham and Fermentis Safale US-05) were tested which were hydrated prior to

pitching or that were sprinkled onto the wort as dry yeast. This resulted in 6 variants.

The wort for this experiment was obtained from a brew on February 13rd 2011. The wort had a starting gravity

of 1057 or 13,9 Brix..Each bottle had a volume of 2 liter and was filled with 1600 ml wort. The amount of dry yeast needed was

calculated using the Mr. Malty yeast pitch calculator and resulted in 0,85 g dry yeast per bottle (=0,53 g/l). For

every yeast two portions were weighed accurately. One portion was added directly to the bottle. The other

portion was hydrated according to the instructions by Fermentis. In short: sprinkle the yeast in a weight of water

10 times the weight of yeast and allow to sit at 27C/81F for 25 minutes (in water bath) and subsequently stir

the bottles for 30 minutes using 5 minutes intervals while slowly cooling the bottles to room temperature.

The hydrated yeast was quantitatively transferred to the bottles containing the wort. To bottles containing the

non-hydrated yeast an additional 15 ml water was added to correct for the water added to the bottles with

hydrated yeast so that the final starting gravities were equal.

Visual observation of the airlock activity showed that for Brewferm Top and Nottingham the hydrated variants

started sooner to ferment then the non-hydrated variants. Both variants of US-05 were lagging behind.

Furthermore the Brewferm Top and the Nottingham showed high airlock activity (higher bubble rates) whereasthe US-05 showed much less activity and it took about one day longer for the main fermentation to finish. There

was no clear difference in activity between hydrated and non-hydrated yeast.

The final gravity and the apparent degree of fermentation determined after 26 days are given below:

Bottle Yeast Yeast

concentration

(g /l)

Hydration

temperature

(C/F)

Final

specific

gravity

(-)

Apparent

degree of

fermentation

(%)

1 Brewferm Top 0,53 27 /81 1,0136 76,1%

2 Brewferm Top 0,53 - 1,0130 77,2%

3 Danstar Nottingham 0,53 27/81 1,0104 81,8%

4 Danstar Nottingham 0,53 - 1,0104 81,8%5 Fermentis SafAle US-05 0,53 27/81 1,0098 82.8%

6 Fermentis SafAle US-05 0,53 - 1,0110 80,7%

As shown in the previous experiment. there is an effect of hydration on the final degree of fermentation but the

effect is small and the effect is yeast strain dependent.

At the moment of bottling the beers were judged by myself.


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Yeast Taste

Brewferm

Top

No difference between hydrated and non-

hydrated

Danstar Nothingham

The non-hydrated is slightly more fruity anddryer and slightly less sweet compared to the

hydrated variant

Fermentis

SafAle US-05

The non-hydrated is slightly more fruity and

dryer and slightly less sweet compared to the

hydrated variant

About three months after bottling the beers were tasted by 13 persons (average tasters) (12 persons tasted 6

beers and one person tasted 2 beers) The beers were offered in pairs (dry / hydrated) and the people were asked

to indicate their preferred beer. It appeared that the dry yeast was preferred 19 times whereas the non-hydrated

yeast was preferred 18 times indicating there was no difference in preference for beers fermented by eitherhydrated yeast or non-hydrated yeast. However, for some yeasts there seems to be a positive effect of hydration

on taste. This will be the subject of a future study. In this study the beers will be evaluated by certified beer

judges to have taste differences more clear.

Yeast Dry / Hydrated # preferred

dry 4Brewferm

Top hydrated 9

dry 9Danstar

Nothingham hydrated 3

dry 6Fermentis

SafAle US-05 hydrated 6

Discussion / conclusion

For quite some years there is a debate amongst home brewers whether or not dry yeast should be hydrated before

pitching. Some even state that sprinkling dry yeast on wort would lead to a decrease in cell viability by 60 to

70%.

Based on the historic data desktop research and the experiments that were performed using different yeasts I

conclude that hydration of yeast is not needed to make a good beer. It does not lead to higher degrees of

fermentation. On the contrary, the historic data research showed that the average brewer obtained lower degrees

of fermentation upon hydration of dry yeast. The historic data research showed that for 9 out of 12 yeast

hydration lead to significant lower degrees of fermentation.

The experiments also showed that when hydration is carried out under exactly the same conditions that it useful

for some strains and not useful for other strains with respect to degrees of fermentation and taste. The

experiments showed that for the Safale US-05 there was a positive effect of hydration on the degree of

fermentation whereas the historic data research did not show a significant effect for the same yeast on the degree

of fermentation. This might indicate the importance of the home brewereffect.

The experiments did not show a significant effect of hydration temperatures of 27C and 40C on the degree of

fermentation for the Safale S-04. However the historic data research showed a significant lower degree of

fermentation upon hydration. This might be due to non-controlled hydration temperature, either be too low

(20C) or too high (>40C).

Based on the described data it is recommended not to hydrate dry yeast since this may cause risks when not

carried out in the proper way. Even when hydrating the yeast one might wonder what the benefit will be over theextra effort and risk.


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Jacques Bertens

--------------

This article was translated from Dutch in English by William Kloek. I would like to thank him for that and also

for having a critical look at the text and suggesting some improvements. Furthermore I would like to thank the

hobbybrouwen.nl forum community for the discussions on the experiments described.

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