Glass jars do not require sterilisation (boiling jars for 10
minutes) if the water bath (or steam canner) processing time is 10 minutes or
more - or if you are pressure canning. For processing times under 10 minutes,
sterilise jars in the water bath canner (filled with water) by boiling for 10
minutes (see chart below with sterilisation time for different altitudes), before
filling with your hot pre-prepared food. Alternatively, if your processing time
is 5 minutes, you could increase your water bath processing time to 10 minutes
and skip the sterilisation step!
|
Sterilisation
Time
|
Altitude
(feet)
|
Altitude
(metres)
|
|
10 minutes
|
0 – 1000 feet
|
0 - 300
metres
|
|
11 minutes
|
1001 – 2000
feet
|
301 – 600
metres
|
|
12 minutes
|
2001 – 3000
feet
|
601 – 900
metres
|
|
13 minutes
|
3001 – 4000
feet
|
901 – 1200
metres
|
|
14 minutes
|
4001 – 5000
feet
|
1201 – 1500
metres
|
|
15 minutes
|
5001 – 6000
feet
|
1501 – 1800
metres
|
|
16 minutes
|
6001 – 7000
feet
|
1801 – 2100
metres
|
|
17 minutes
|
7001 – 8000
feet
|
2101 – 2400
metres
|
|
18 minutes
|
8001 – 9000
feet
|
2401 – 2700
metres
|
|
19 minutes
|
9001 – 10000
feet
|
2701 – 3000
metres
|
It is recommended to pre-heat jars (i.e. warm jars up in hot
water, no boiling required – boiling is up to you). Unsure if jars are high
quality, tempered glass? Pre-heating is recommended to reduce the risk of
thermal shock (sudden expansion/shrinking when cold jars are filled with a hot
preserve, or vice versa). Jars can be pre-heated in a water bath canner,
dishwasher or sink full of hot water.
Jars (including lids and seals) are not sterile out of the
packaging – even if they are brand new. Jars or lids may have glass residue, dust,
or a bug/pest in the packaging for example. A quick, hot rinse (soapy water
first, then just hot water) of all jars prior to use in preserving is
recommended – via dishwasher or by hand. Lids and seals are best rinsed by hand
in hot water.
Do not boil the lids/seals – this can reduce the effectiveness of
the sealing compound inside the lid/seal. Lids and seals can be used at room
temperature, or slightly warmed for a few minutes in hot water (not on heat) if
you prefer. Jar rings (i.e. mason jar rings) and jar clips do not require
boiling either, as they do not come into contact with any preserve. Ensure they
are clean before use though. Jar gaskets (rubber rings) do not require boiling
but do need to be soaked in warm water prior to adding to prepared jars.
As educators, we must teach the safest technique to ensure high
quality preserves and help jars to last for years (or generations). We recommend
warming jars up as explained above. Jars are not recommended to be warmed via a
microwave or oven.
Author: Megan Radaich
Image Credit: Megan Radaich
Publication: www.foodpreserving.org