Mash Time Dependency of Wort Fermentability

Abstract

Does continuing alpha amylase actity after the mash has been converted increase the wort fermentability? The literature suggests that alpha amylase has only little affinity towards shorter chained dextrines which should result in only a small affect on the fermentability of the produced wort. This experiment tries to answer this question.

Equipment

• 2 Gal cooler as mash tun
• Weyermann Pilsner malt (0.75 kg)
• thermometer
• ladle
• pot for boiling the mash
• strainer and paper towles for latuering the mash
• bottles for fermenting the samples
• lager yeast (Wyeast 2206 from a home brew batch)
• sanitized syringe for measuring the yeast
• oxygenation stone and oxygen bottle

Procedure

The bottles and the funnel are kept in a pot of boiling water. This sanitizes them and keeps the bottles heated so they don't shatter when filled with hot wort.

2.4 l strike water were mixed with the 750g Pilsner malt to reach a mash temperature of 155 *F (68 .3 *C). Since this was lower than the target, 0.2 l boiling water was added after 4 min to get to 159 *F (70.5 *C). A high mash temperature was desired to start out with a mash that is poorly fermentable and is thus able to show any drop in fermentability over time.

The mash pH was measured at about 5.3 with a ColorpHast test strip.

The cooler was placed in an ambient temperature of 170 *F (77 *C) to avoid a temperature drop. But despite this effort the temperature dropped to 152 *F (66.6 *C) before the first sample was taken. After that it remained at that temperature.

Starch conversion was tested with iodine on chalk and after 40 min the mash was iodine negative. At this time the first sample was pulled. 300ml mash were strained into a pot through a strainer. The spent grains were again mixed with 300ml water and strained again. The resulting wort was brought to a boil for 15 min. After the 15 min it was filtered into a bottle through a paper towel. paper towel, strainer and funnel were sanitized in boiling water. Each bottle was capped with aluminum foil. The whole procedure took about 25min for each sample

4 more samples were taken every 30 min. During this time the mash temperature stayed at 152 *F (66.6 *C).

All samples were left to cool for 6 hrs (overnight). Then the original extract was measured for each sample. 5 ml of Wyeast 2206 yeast slurry were injected into each bottle after 10 s of oxygen though an oxygenation stone.

The samples were fermented at room temperature ( ~67 *F / ~19 *C) and shaken occasionally.

Results

The measurement error for the original extract was estimated with +/- 0.12 *P

Conclusion