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Thread: Filtered Steam, Sterile Air, and Sterile Co2

  1. #1
    Join Date
    Aug 2014
    Location
    Whitefish, MT, USA
    Posts
    12

    Filtered Steam, Sterile Air, and Sterile Co2

    This question pertains to kegging operations, more specifically cleaning and sanitation. When using an automatic clean-fill system, it is recommended that filtered steam, sterile air, and sterile Co2 be supplied to the system.

    My questions, and what I would like to better understand, are:

    • The importance of each of these.
    • How each of these affect the final product, and why.
    • What would the consequences be for not having these in place.

    I am looking for answers beyond the obvious risk of exposing product to non-sterile environments. What I mean is, if the keg is purged with non-sterile air, but is then sanitized with steam and purged with beverage grade Co2, what purpose does sterile-air play and why do I need it?

    Beyond that, what purpose does filtered steam play? Is the consequence limited to off-flavors in the final product, or are there other consequences?

    Finally, if my Co2 is beverage grade, why would I need a sterilizing apparatus?

    Thank you in advance.

  2. #2
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
    Posts
    1,636
    Filtered steam. The filtering here is normally considered to be to remove particulates such as rust and precipitates from steam. Firstly, the steam has to be culinary grade, i.e. rust free, odour free, and free from any chemicals used to minimise corrosion in the boiler itself and the steam distribution system, and in the case of bigger breweries, condensate collection systems. They are generally sintered metal filters. The rust or other particulates in the steam may settle on the stainless steel of the kegs and create focal points for initiation of corrosion of the keg. And you simply don’t want harmful chemicals or any odours getting into your beer. Oil is not generally a problem with steam, unless you have oil lubricated control valves when there is a risk of pickup by the steam.

    Sterile air – why introduce bacteria, moulds etc. which then have to be killed off by the steam sterilisation process? Alternatively, use steam to blow out CIP residues. As with the steam and CO2, must be odour, oil and particulate free.
    Sterile CO2 (nitrogen or mixed gas) – if you want to reduce your beers shelf life, using unsterile CO2 is a good way to do it. The keg should be sterile by the time you introduce CO2, and your beer may be flash pasteurised, sterile filtered, or simply of good enough quality to achieve the shelf life you desire. Why risk this with contaminated CO2?

    When sterilising gases, don’t forget that simply putting a sterilising filter in a housing, in the gas supply line does not guarantee sterility of the gas. So you need to be able to sterilise the gas filter with food grade steam, all the way through into the beer line. Generally NRVs are fitted between the sterilising filter and the injection point.

    The hoses you use to connect between the gas supply (bottles presumably) will not be sterile apart from initially after manufacture, and certainly not once open to the atmosphere, and if you get any beer running back into the lines, you will develop microbial growth. Pasteurisation / “sterile” filtration doesn’t guarantee absolute sterility, and anyway, there are always leaks etc to allow microbial ingress.
    Beverage grade gases are not normally guaranteed sterile – the grade refers primarily to the purity of the gas, e.g. 99.9999 % CO2 or Nitrogen with other gases, possibly including oxygen forming that 0.0001%.
    dick

  3. #3
    Join Date
    Oct 2013
    Location
    Dallas, Bangalore and soon Goa
    Posts
    245
    Sterile is always better. Dick points out the major reasons.

    Is it absolutely necessary? No. Obviously they have been making beers for a very long time. Before Pasteur was born and before they even knew about micro organisms.

    The consequences could range from nothing, to having to dump a batch of beer, to loosing expensive equipment. You may have no issues for many years, and all of a sudden a problem arises. Each of us has to determine what calculated risk we are going to take. To go against recommendations of a supplier is an increased risk. They are most familiar with the equipment and have specific reasons for their recommendations. Equipment may be degraded much faster, as well as the increased risk of contamination.

    Personally, I choose to take the risk of non sterile air and CO2. This has been acceptable in my situations and has not led to any know issues over many years. I am particular about my vendors of CO2, especially here in India. I would not take the chance of non sterile steam since it will directly contact the surfaces my beer will contact. My boiler water is treated with rust inhibitors and I do not want to risk the chemical contamination. I also would not use steam from untreated boiler water that is non sterile. It may contain iron which would impact the flavor of the beer.

    Your best bet is to ask any given vendor for their rationale as to why the recommendations are made. Then you can decide for yourself the level of risk it poses to your situation.

  4. #4
    Join Date
    Aug 2014
    Location
    Whitefish, MT, USA
    Posts
    12
    Thank you Gentlemen. I appreciate the responses.

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