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Master Brewers Association of the Americas > BREWING RESOURCES > Ask the Brewmaster
November 03
DMS breakdown during wort boiling

Q: What time is needed for DMS breakdown during wort boiling?

A: Dynamic low-pressure boiling uses a temperature range of 100–103°C for wort boiling. Necessary parameters of wort boiling, such as the stripping of dimethyl sulfide (DMS), can be widely influenced by a number of factors including the number of pressure build-up intervals, the intensity of the pressure, and the rate of alteration of the pressure (Δp/ΔT). With all these factors in mind, total evaporation can be reduced to 4–5%. In this case, boiling and DMS reduction can be done in 60 minutes.

August 25
Pectin build up problems

​Q:  Is pectin build-up a problem for kegs or bottle fillers used to package cider?

A:  Pectin is found in fruits where it is part of the cell wall material.  It is a complex polysaccaride and forms a jell. There is very little available data on how to deal with pectin build-up on filling equipment in packaged cider, however many cider makers will use a pectinase enzyme to break it down and eliminate it from being a problem.  For cider makers who do not treat the pectin with an enzyme and package unfiltered product pectin build up can be an issue in both kegs and fillers.  I asked Joe Dirkson (Ecolab) and Dana Johnson (Birko) to weigh in on this. Their consensus is to use a heavier caustic concnetration (up to 4%) with an oxidizer additive to help break up the pectin.  They both preferred a hydrogen peroxide additive.  The additive has a short life in the caustic and must be injected in small amounts at regular increments to be effective and to keep a concentration between 1000-5000 ppm.

August 12
Aging of whole hops

​Q:  In Volume I of the MBAA Practical Handbook for the Specialty Brewer, in the hops section, it was stated that freshly harvested hops should be aged for a minimum of 6-12 months before using.  This caught me by surprise.  I would have figured fresher the better.  Really?

A:  For some hops, particularly low alpha aroma varieties, the slow oxidation that occurs in baled whole hops kept at freezing storage temperatures (below 0 degrees C) over the course of several months will develop, improve and stabilize their flavors.  This is due to the oxidation of certain compounds called sesquiterpenes.  The oxidized sesquiterpenes develop complex flavors.  However over aging the hops can also produce a harsh bitter quality and cheesy aromas. Most brewers are using pelleted hops so any request for aging would have to be made to the supplier and specified because once pelleted and packed into nitrogen flushed bags, the oxidation process is almost completely shut down. 

July 15
DMDC anti-microbial additive

Q: Awhile back I noticed the TTB approval of Dimethyl Dicarbonate (DMDC) as a processing aid in beer production, but I haven't seen anything more written about it. Can you tell me a little about this option? The TTB release describes it as a "microbial load reducer" and I can find a number of resources that cite its use in winemaking. They seem to use it to reduce wild yeasts. Does DMDC have any effect on beer-spoiling bacteria? Is this a product we'll see beer suppliers carrying in the near future? An overview of processing instructions or help identifying further resources might be useful as well.

A: The commercial name is Velcorin and it has been used in soft drinks and wines (usually low alcohol sweet wines with some residual sugars) for some time, mostly in South America and South Africa.  It has recently been approved for use in both wine and beer in the US and at least one large US winery is studying its use in sweet, low alcohol wines.  Velcorin is effective against yeast, bacteria and molds.  It penetrates the cell membrane and targets certain enzymes which results in the cells lysing (opening up) and re-fermentation is almost impossible. You can find out more at www.velcorin.com.


July 08
Recapturing rinser water

​Q: You had mentioned that you had some experience with reclaiming bottle rinse water and sending it through the filler vacuum pump and possibly into a pasteurizer. Do you recall if there was any filtration of the water? Was there some sort of a storage tank for the water? We really see this as a great opportunity with 3 bottling lines and 2 can lines and any insight would be GREATLY appreciated.

A: The rinse water recovery is low hanging fruit but will need a receiver tank, float control for fresh water refill and a pump.  We let the water from the rinser fall by gravity into a receiver tank and then pumped that water through the vacuum pump to cool the seal.  If the water level got low (rinser had shut off) then the float would open a fresh water valve and keep the tank full so the seal would not run dry and overheat.  We then would collect the water out of the vacuum pump and into another receiver and pump that water (now slightly warm) to shower off bottles coming off the crowner.  The shower water would go to drain.  This way we used the water 3 times and saved an appreciable amount off the water and sewer bills.  You could use the water out of the vacuum pump in a pasteurizer as well.

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