You wait for a full steady flow of steam. The time for venting is 10 min. not 7 min. according to safe USDA guidelines.

Linda Lou won't ever steer you wrong. ;) Quite a lot of steam and then wait the full 10 mins.

To try to rush the process is to live to regret it.

Dave

I put the regulator weight on the stem when the first steam starts to come out , but don't start timing until it starts rocking. Maybe yours works different.

Definitely as Linda Lou said. Most of the pressure canner manuals have not been updated, so write in the revised 10-minute time and double-check any other canning time and pressure recommendations in the manual before following them.

Carol

My manual that I received with my new All American canner says 7 minutes.

tanyak - Well I suppose if one wanted to be picky about it 7 mins. or 10 mins. won't make much difference. Of course it's your choice so if you prefer, split the difference and go for 8 1/2 mins. ;) But honestly, regardless of what your pressure canner manual says, as we have said 10 minutes is the time required by the USDA and all the professional testing laboratories.

westelle - we are talking about two different things here. ;) The question pertains to the amount of time required between when the canner begins to steam and when one places on the weight - 10 mins. is required as said above - not when steam first begins to come out.

There is a very good reason for this requirement - all of the trapped air within the canner must first be expelled for the temperature to reach the required levels. Retained air in the canner reduces the internal temperature and increases the risk of improperly processed food. The steam forces out all the air so that the canner contains only boiling water and steam. That way the required temp of 240 F can be easily and quickly attained, and will be maintained throughout the entire processing time.

You are apparently referring to the time called for in the recipe for the product to cook under pressure. You are correct, depending on your model of canner, once the weight begins jiggling you then start timing. Different issue. ;)

Dave

Thanks all - I'll rather wait 10 minutes then. How long does it usually take to start venting if you're heating it on gas (quite high turned up) before it starts venting? I suppose it depends on how large your pot is . . . Mine takes about 15 minutes - does that sound about right?

Right - it depends on the size of the canner and the BTU output of the stove burner - but it could be 15 minutes with a really big canner. General rule of thumb is that it takes water 10 minutes to boil depending on the air temps and heat source.

Start with hot tap water, the required 3-4" of water in the canner, the burner on high, and preheat it before inserting the jars of hot product. That may cut some time off the process.

Dave

There is a very good reason for this requirement - all of the trapped air within the canner must first be expelled for the temperature to reach the required levels. Retained air in the canner reduces the internal temperature and increases the risk of improperly processed food...

Steam occupies ~1500x the volume of water, depending upon pressure. And steam is more dense than air. So in my view, the "venting" requirement is primarily recommended to confirm (in a simplistic way) that the contents of the jars have gained a temperature close to that of the boiling point of water before increasing the pressure (and thus marking that point in time [ or shortly thereafter ] as the beginning time of the canning process). Not to rid the vessel of air, which will occur rather rapidly even with the weight applied to the vent when the water is at boiling temp.

So basically, a 10 minute boiling time (as evidenced by the venting of steam) should usually push the vessel's contents (regardless of the initial respective temps of the water and the jars and the contents of the jars) close to the boiling point and, after the recommended time at pressure, virtually assures that the 240-250 °F will have been attained by the contents for the necessary length of time.

...I to not vent the pressure canner.

Reg

I don't claim to be a professional or an authority, Reg so your more technical explanation may very well be correct.

I'm just quoting the guidelines and the reasons for those guidelines from the USDA and the Cooperative Extension of the University of Georgia home preservation testing laboratories. They are generally recognized as the authorities on the subject of home canning safety so most of us elect to abide by their guidelines.

But as is often said here - each person chooses their own level of acceptable risk.

Dave

Cooperative Extension...

These organizations are very conservative on methods used to preserve food... and correctly so. But some of the things they recommend regarding canning make no sense to me. Such as sterilizing the glass jars before using them in a canning event... why ? Come on, that is just a perpetuated old wives tale.

I mean the jars come out of the sterilization process and come back to room temp and are exposed to lots of bacteria both airborne and in the food mix with which they are filled before canning. What did that accomplish other than to waste energy and time ? Just well-clean the jars with warm water and detergent and thoroughly rinse. The only real (and needed) sterilization will be accomplished during the canning process.

Reg

Extension agencies only recommend sterilizing jars if processing time is less than 10 minutes (i.e. for a jelly BWB 5 minutes in 8-oz. jars). You may have heard otherwise somewhere, but it's not the standard to sterilize in other instances.

Tanya, my All-American canner is relatively new and my manual also says 7 minutes. It demonstrates exactly what I mentioned earlier re. the vent times in the manuals. The pressure canner companies just keep churning the product out but don't update manuals to reflect recent USDA standards.

I have a gas hob and my 21.5 quart All-American canner also takes approximately 15 minutes.

Carol

Extension agencies only recommend sterilizing jars if processing time is less than 10 minutes (i.e. for a jelly BWB 5 minutes in 8-oz. jars)...

Makes no sense and here is why:

You "sterilize" the containers whose contents need a processing time of 10 or fewer minutes (such a product will not be infected with C botulinum bacteria even if left in open air). Then, before putting in the stuff, you "unsterilize" the containers by exposing them to ambient conditions. Then they are processed for 10 or fewer minutes.

This makes no sense to me, unless one assumes that the initial sterilization eliminates bugs that cannot contaminate the containers by air borne exposure. No conservative approach would make that assumption. At this rate, just clean the jars and process them so that their domes will seal for long storage.

Reg

Reg, I agree that sterilization is not about botulism, or even mold or other airborne contaminants. For me sterilization is about killing any surface bacteria that may have gotten onto the jar during washing. Could be salmonella from the raw egg that went into a mixing bowl that was washed in the sink that I set the jar in. Could be icky bacteria that went from a pile of poop to my dog's whisker to the spoon I used to feed him peanut butter to the jar I soaked the spoon in (on second thought let's pretend that couldn't happen).

Even in the case of mold, for a short processing time I think it's worth trying to kill any spores hanging onto the jar rather than assuming they all came off in the wash. Some more will land on the jar during filling, but not as many as it collected sitting in the basement all winter.

I don't sterilize, I process jams for 10 minutes. But it's come up on here before: the multiple layers of safety are there for a reason. Even the best canners don't get every little thing exactly to USDA standards, but the factor of safety is built in.

Melissa