Naked Science Forum

General Science => General Science => Topic started by: Debbie Knipe on 20/01/2011 06:30:06

Title: Why do my jars of preserve sometimes go fizzy?
Post by: Debbie Knipe on 20/01/2011 06:30:06

Debbie Knipe  asked the Naked Scientists:
   
Dear Chris
 
I am a keen listener (http://www.thenakedscientists.com/HTML/podcasts/) of Cape Talk and enjoy your timeslot very much.
I know that you are not the naked chef but I am pretty sure the naked scientist can answer my question.
 
I make a chilli product which consists of Chilli; fresh ginger; garlic, lemon juice and olive oil.  I chop and mix all the ingredients and spoon it into a jar.  My problem is that sometimes, when I open a jar of my chilli it fizzes out, as if its fermented.  Why does this happen? And How can I prevent it?  I usually put my jars in the microwave for four minutes so the jars are hot when I spoon the ingredients into it.  I refrigerate it immediately.  

Please help.
Kind regards
 
Debbie Knipe

What do you think?

Title: Why do my jars of preserve sometimes go fizzy?
Post by: CliffordK on 20/01/2011 06:34:00

Do you taste/smell it when it is fizzy?

Be somewhat concerned about Botulism in canning though.  If you do choose to eat it, I'd cook it well a second time.

Have you considered a pressure cooker?

Title: Why do my jars of preserve sometimes go fizzy?
Post by: Geezer on 20/01/2011 08:02:14

Sounds like you are not actually heating it after you put in the jars. If so, you are not really doing anything to preserve it, so it may well ferment, even at refrigerator temperatures.

You need to elevate the temperature in a special canning pressure cooker to kill all bacteria. It needs to be a lot hotter than boiling water. I'd suggest you get a book on canning and read all the precautions very carefully.

Title: Why do my jars of preserve sometimes go fizzy?
Post by: graham.d on 20/01/2011 09:08:23

You say you are heating the jars before you put the ingredients into it. I'm surprised they get warm at all. Empty glass jars (assuming they are glass) will not heat much in a microwave. Microwaves only heat things that are moist and/or slightly conductive. Glass will not heat up. Use a conventional oven and get them to a over 100C for a few minutes. You can sterilise using the microwaves (not the heat but the microwaves themselves) but some bugs are resilient - I think 12 minutes would be better according to what I hacve read. What do you do for lids??

I'm no expert on making preserves, but isn't it usual to boil the ingredients to kill any bacteria? It also seems that the stuff you making has not got any natural antibacterial substance (like sugar or vinegar) so killing off the natural yeasts and bacteria before bottling should be necessary if you want to keep the stuff for a while.