Re: [compost_tea] Grain sterilization

From: <soilfoodweb_at_aol.com>
Date: Thu, 06 Nov 2003 10:33:52 -0500

Any time you culture microorganisms in order to grow a specific species, or set of organisms, sterilization has to be performed. The set of microorganisms that are normal inhabitants of any surface have to be killed if you want to be 100% successful at growing the desired set of organisms.

To be assured that a pure culture of Agaricus bisporus (the white mushroom we all love to eat) will grow on a desired substrate, all the other organisms on the substrate (food resource) have to be killed, or a significant percentage of the time, some other organisms will out-compete the Agaricus, adn the grower will lose money.

Chris is absolutely correct about sterilizing grains. It's done all the time.

Typically grains used to make beer are at least pasteurized, and usually sterilized, especially in large production facilities where they can't allow contamination to destroy the product they are trying to sell. Does the heat treatment affect the quality of the final product? Sure it does.

Wine production uses high sugar content, inoculation of HIGH levels of yeast, and low pH to control the fermentation instead of sterilizing the initial starting materials.

If you use high heat on sugars and proteins - which is what grape juice is all about - you denature the sugars and proteins, and the yeasts you want for the fermentation won't grow. Some folks use sulfur compounds to try to control yeast populations, but many of us are sensitive to that sulfur in the wine.

Why don't we sterilize or pasteurize the substrates gong into compost tea brews? You could do that, except it is usually not necessary. You do want to be careful though. We reacently had a person sending in tea where tea had an unpleasant microbe growing in it. The person got upset at me (they still aren't speaking to me), because we showed them their tea was contaminated. We asked them to send in all the starting materials for the tea, and proved that the contamination was in the molasses. They wanted to sue the company making the molasses (sigh), except they were using a molasses container that they had been using for years. Probably that container became contaminated by various people making tea. Not the fault of the company providing the molasses.

Take home story: If you put compost tea onto things you will eat without washing them, make certain the material you put into the tea are food-grade.

Take home story number two: If you live in high human density areas, wash your food before you eat it. What was on the hands of the person who handled that food before you? Did that deer that wandered through your garden pee as it walked through? Wash fruit before you eat it.

Haven't had time to go look for USDA peat pasteurization regs. Will try to do that soon.

Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
www.soilfoodweb.com

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Received on Thu Nov 06 2003 - 13:37:51 EST

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