¶ Equipment and facilities
- 7 quart pressure cooker
- metal steamer basket that fits in the bottom of the pressure cooker
- stove if the pressure cooker needs one
- Electric pressure cookers like Insta-Pot need no stove
- 2 cup measuring cup
- tap water faucet
- tongs for removing hot things from the pressure cooker
- half-pint freezer-safe mason jars (regular mouth)
- plastic lids for regular mouth mason jars
- They'll probably be embossed with small print that says “not suitable for canning”, but I've found these can handle pressure cooker heat just fine if they are made of polypropylene. That's recyclable plastic #5, i.e. PP ♷.
- Two 250 mL glass culture media bottles with GL45 plastic screw caps
- Wash and dry all mason jars, lids, bottles, and screw caps.
- I used an automatic dishwasher on its “sanitize” cycle.
- Put 2 cups of cold tap water in a 7 quart pressure cooker.
- N.B.: we start with 16 fluid ounces of water in the pressure cooker for steam production. At the end of 30 minutes of cooking at pressure at sea level (Boston area is basically sea level), I found 12 fluid ounces of water remaining in the pressure cooker, for an approximate loss rate of a cup per hour of cooking at pressure. --FL 10-Dec-2020
- Put the steamer basket upside down in the bottom of the pressure cooker. This creates a raised platform above the water level that allows steam through.
- Screw the plastic jar lids onto the mason jars.
- Screw the caps onto the glass culture media bottles.
- Arrange the jars and bottles in the pressure cooker so the pressure cooker lid can still close tightly.
- Close and seal the pressure cooker.
- Follow the pressure cooker manufacturer's instructions for bringing the cooker up to pressure.
- Cook for 30 minutes at pressure.
- Turn off the heat.
- Wait for the pressure cooker to unlock by itself.
- Use tongs to remove the now ostensibly sterilized (and hot!) jars, lids, bottles, and screw caps from the pressure cooker.
TBD. Roughly, I plan to:
- Mix up rich growth media and fill the jars and culture media bottles with it.
- Sterilize the jars and bottles using the procedure above.
- Uniquely label each jar/bottle. I plan three categories of jars:
- A. Closed immediately after sterilization. Experimental control. (See how well pressure cooking sterilized jars.)
- B. Opened briefly to innoculate with bread baking yeast, then closed.
- C. Opened briefly to innoculate with sterile innoculation loop/tool, then closed. (Acts as experimental control for B.)
- Incubate the jars and bottles at 30°C for 30 days.
- Every day, take a photograph of each jar without opening it. Record in notebook.
- At the end of the 30 days, open every jar and bottle, photograph the media within, and smell. Record photos and notes on smell. Use microscope to examine any interesting growth.