From the Helpline

Got a Question?

We receive food preservation and food safety questions from all over the world. What follows are some of the most popular and intriguing ones. Remember, if you have a question for us, please use our contact form: Got A Question?. We would love to help you safely preserve!

Cottage Food Operations

I am starting a small business out of my home preserving jams and jellies. I would like to sell my products at local farmer’s markets. Are there any state or local requirements for this?

Yes, there are established regulations for this activity known as a cottage food operation. A cottage food operation is a small-scale business that prepares and sells certain non-potentially hazardous foods from a private home kitchen in California. The cottage food operation is regulated by the California Homemade Food Act, which was enacted in 2013 to promote economic recovery and entrepreneurship. The cottage food operation must follow the approved food list, labeling requirements and sales limits set by the state.

Here is a website that will introduce you to Cottage Food Operations and requirements:

https://www.cdph.ca.gov/Programs/CEH/DFDCS/Pages/FDBPrograms/FoodSafetyProgram/CottageFoodOperations.aspx

Cottage Food FAQs: https://www.cdph.ca.gov/Programs/CEH/DFDCS/CDPH%20Document%20Library/FDB/FoodSafetyProgram/CottageFood/CFOFAQ.pdf

What is a Steam Canner?

Steam canning, or atmospheric steam canning, can be a safe method for home food preservation of most high acid food (i.e., food with pH of 4.6 or below). The steam canner was initially developed in the 1920s as an alternative to the boiling water canner; however, it was not approved for home canning until 2015. Steam canning is a more environmentally friendly process than boiling water canning for the following reasons: (1) the steam canner uses much less water than a boiling water canner and (2) the steam canner reaches the required temperature for processing more quickly and thus uses less energy than the boiling water canner. Read more…

Burning Issue: Can Acid Foods be Processed using Steam Canners?

The University of Wisconsin, under the leadership of Dr. Barbara Ingham, has conducted research on appropriate use of atmospheric steam canners for home canning in collaboration with the National Center for Home Food Preservation (NCHFP). Atmospheric steam canners are used for processing naturally acid or properly acidified foods with natural or equilibrated pH values of 4.6 or below. They are not pressurized vessels used for processing for low-acid foods.

Sufficient studies and peer review have been completed that we are now able to say that as long as certain critical controls at various steps in the canning process are achieved, USDA and NCHFP process times for canning acid or properly acidified foods (pH of 4.6 or below) at home with properly research based recipes and procedures can be used. The research looked at temperature distribution in the steam environment surrounding the jars in a dome-style steam canner, heating patterns of several different food types during processing in the canner, and the contribution of standardized cooling procedures at the end of the process time.

Some of the key controls in addition to the acidity of the food product are knowing that the canner has had the air vented out of the steam before processing begins, and that the pure steam is at the temperature of boiling water at the start and during processing. Jars must be preheated before filling with food and cooling prior to processing must be minimized. Processing times must be adjusted for altitude, and must also be 45 minutes or less, including any altitude modification. The processing time is limited by the amount of water the canner base will hold, and the canner cannot be opened to add water or for any reason at any time during the process. Finally, cooling of jars must take place in still, ambient air without any forced, more rapid cooling. The slow cooling of processed jars is important to the overall food safety of the whole canning procedure.

Dr. Ingham provides further instructions and details about carrying out canning in an atmospheric steam canner using USDA acid food processing recommendations in the article: "Steam Can it Right".

Eventually we will integrate this and more complete advice into additional offerings on the National Center for Home Food Preservation website (https://nchfp.uga.edu/).

The results of this research were published in a peer-reviewed scientific journal in May 2015.
Willmore, P, Etzel, M, Andress, E. and Ingham, B. (2015). Home processing of acid foods in atmospheric steam and boiling water canners. Food Protection Trends, Vol 35, No. 3 (May-June), p.150–160.

September 9, 2015
National Center for Home Food Preservation

Should I Can in my Electric Multi-Cooker?

From the National Center for Home Food Preservation:

Should I can in my electric multi-cooker appliance?

Even if there are instructions for pressure canning in the manufacturer’s directions, we do not support the use of the USDA canning processes in the electric, multi-cooker appliances now containing "canning" or "steam canning" buttons on their front panels. Our pressure process directions have not been developed for that type of appliance, and the canner being used does matter. Our recommendations were determined for stovetop pressure canners which hold four or more quart-size jars standing upright.

We do not know if proper thermal process development work has been done in order to justify the canning advice that is distributed with these pressure multi-cooker appliances. What we do know is that our canning processes are not recommended for use in electric pressure multi-cookers at this time.

Some of the major reasons we cannot recommend using electric multi-cookers for pressure canning:

Thermal process canning work relates the temperatures in the jars to the temperature inside the canner throughout the processing. No USDA thermal process work has been done with jars inside an electric pressure cooker, tracking the actual temperatures inside the jars throughout the process. It is ultimately the temperature and heat distribution inside the jars that matters for the destruction of microorganism in the food product. The position of jars in the canner and flow of steam around them also impacts the temperature in the jars. For example, there would be expected differences in jars piled together on their sides from those standing upright on the canner base.
What matters is temperature, not pressure. One manufacturer says its cooker reaches the pressure required for canning, but that alone does not prove the food in the jars is heated throughout at the same rate as in the canner used for process development. A manufacturer should do process development work to document temperatures throughout the unit at a given pressure and throughout the whole process time. Just producing an interior pressure is not sufficient data for canning recommendations. For example, if air is mixed in the steam, the temperature is lower than the same pressure of pure steam. That’s why a proper venting process is so important in pressure canning – to obtain a pure steam environment inside the canner. Also, one has to know how to make adjustments in pressure readings at higher elevations. The same pressure and process time combination cannot be used at all elevations.
In order to ensure the safety of the final product, the temperature in the canner must stay at minimum throughout the process time. Do power surges or drops with an electric canner cause the temperature to drop too low? How will you the user know if that happens with your cooker?
One of the big concerns is that the USDA low-acid pressure process times rely on a combination of heat from the time the canner is coming to pressure, during the actual process time, and then during the early stages of cooling the canner and jars. Even after the heat is turned off under the canner, at the end of the recommended process time, the food remains at high enough temperatures for another period of time that can still contribute to killing of bacteria. This retained heat while the canner has to cool naturally to 0 pounds pressure before opening is used to advantage in calculating the total sterilizing value of the process to preserve some food quality. If anything is done to shorten the cooling period, including using a very small cooker, then the food could cool down more quickly, and be under-processed. (That is why we recommend using only pressure cookers that hold four or more quart-size jars.) Bacteria are not killed in the food only during the process time; the time it takes the canner to come up to pressure, the process time, and the cool-down time all matter. There is no way at this point in time to know exactly the percentage of contribution from cooling for each of the canning recommendations.

Please note: This statement about electric cookers does NOT include the Ball Automatic Home Canner for acid foods only, which is electric, but (1) is not a "multi-cooker", but a dedicated canner, (2) comes with its own instructions and pre-set canning options for specific food preparations, and (3) has had proper thermal process development done to support the recommendations with it. Jarden Home Brands also sells an electric boiling water canner, but it is not a pressurized appliance and for canning purposes operates similar to a traditional boiling water canner. Directions from the manufacturer for this Ball canner, as well as for the Weck non-pressurized electric boiling water canners, should be followed to get them assembled and for managing temperature settings to achieve a boiling process.

For more information about canning in pressure cookers, please read NewsFlash: Canning in Pressure Cookers.

February 1, 2019
National Center for Home Food Preservation

Testing a Presto Pressure Canner Gauge

I reside in San Diego. I believe you are the closest facility to perform the annual testing on my Presto canner pressure gauge. You advertise that you can do the testing at your facility in Orange County during a public event. As there are no public events at which to have this service done due to Covid19 - has an alternative procedure (mailed in perhaps?) been developed?

Presto will test canner pressure gauges for free, but they must be mailed in. See details in a previous Helpline request below. As an alternative, you can buy a weighted gauge regulator for your Presto so you don't need to rely on the dial. You would also be able to get an idea of the accuracy of the dial by comparing it’s reading when the weighted gauge started to regulate the pressure.

Per Presto:

Presto makes a 3-piece adjustable weight that can “convert” your Presto Gauge Pressure Canner into a dual-gauge pressure canner, like the All-American. It's a 3-piece weight that adjusts easily to 5, 10 and 15 lbs of pressure; the Presto part number is 50332. This 3-piece weight is only designed for use with a Presto.

This item is available at several locations/internet sites by googling "Presto weighted gauge pressure canner" or similar.

Here is a YouTube on how to use a weighted gauge pressure canner, not for Presto, but similar product:

https://www.youtube.com/watch?v=uAUC6cvpW0Q

And, in case you need the canner manual:

https://www.gopresto.com/content/parts-service/manuals-finder

Where can I get my pressure canner gauge tested and how much does it cost?

Pressure canners with only a dial gauge need to be tested annually to ensure dial gauges are accurate. If your dial gauge is not accurate, it is not correctly reading pressure which may result in under or over processing and unsafe food.

UCCE Master Food Preservers of Orange County recently acquired a device to test Presto Brand pressure canner gauges and offer free pressure gauge testing at our public workshops and events scheduled at the South Coast Research & Extension Center.

For a listing of our workshops and events, please check our website Home Page calendar regularly.

See information below for the two major pressure canner companies: All American and Presto.

All American Pressure Canners: If you have an All American pressure canner, All American, as well as its parent company, Wisconsin Aluminum Foundry, does not provide this service. A telephone conversation with a service representative at All American revealed that the cost of mailing the old parts for testing was more than the cost of replacing the part(s). In fact, if you have a model older than 1995, you can simply replace the older gauge with a newer one.

Presto Pressure Canners: Presto will test Presto canners for no charge. Simply send gauge to them (prefer shipment by UPS; allow turn around time of more than two weeks, so plan ahead!)

NATIONAL PRESTO INDUSTRIES, INC.
Consumer Services Department
3925 N. Hastings Way
Eau Claire, WI 54703-2209
Phone: 1-800-877-0441 1 – 800-368-2194.
Email: contact@gopresto.com

Information on purchasing your own Presto pressure testing unit is at the National Center for Home Preservation’s site: http://nchfp.uga.edu/educators/Presto%20Testing%20Unit%20ADW07-5239C.pdf

General information:

An excellent article on pressure canners, which includes discussion about the weighted gauges and dial gauges, as well as resources for testing the gauges can be found at:
http://ucfoodsafety.ucdavis.edu/files/75897.pdf.

This publication also shows other parts of the state where gauges can be tested, such as

Non-UC Testing Services:
Embarcadero Home Cannery
2026 Livingston Street
Oakland, CA 94606
Phone: 510-535-2311
Email: ehcan@hotmail.com
Dial gauges are tested for approximately $5 plus return postage. Individuals would remove the gauge and mail it to EHC. They will test it using their master gauge and return it with a report as to its accuracy and invoice. They sell new gauges for $21. Once mailed, EHC will return within a week.

Don't Have a Master Food Preserver course near you?

California counties that have a Master Food Preserver program can be found at this link: https://mfp.ucanr.edu/Contact/Find_a_Program/

For those counties that do not have a Master Food Preserver program, the statewide UC Master Food Preserver Program is offering a series of online food preservation classes for students who will not become volunteers upon course completion and want to learn to preserve food safely. If this interests you, please click on this link to find out more about the 2025 UC Master Food Preserver Online Program Training: https://mfp.ucanr.edu/Volunteer/BeMFP/2025-Online/

To learn more about safe home food preservation, the primary source we use is the National Center for Home Food Preservation (NCHFP). NCHFP uses research-based methods and partners with the USDA for food safety.

The University of Idaho offers a six-week online class for individuals who want to can and preserve foods for their families. No prior knowledge is required. "Preserve at Home".

We also have videos from extension offices around the country on our site at UC Master Food Preservers Video Library.

Is the fruit of an apple with apple scab safe to eat?

Apple Scab: The fungus, venturia inaequalis, lives in dead leaves on the ground. If they are beneath an apple tree, the fungus is transferred to the young fruit via spores and results in apple scab. Venturia inaequalis actually grows only very superficially on the apple.

Is the fruit of the apple then safe to eat?

The University of Nebraska publication on Apple Scab states, “Though the fruit may appear unsightly, it is safe to eat.” See the full publication by author Amy D. Ziems, Extension Educator.

Obviously, as with any ‘spoiled’ fruit, you would cut the ‘bad’ parts off and scrub/wash it well before eating.

The UC Davis publication titled, “Key Points of Control and Management for Microbial Food Safety: Edible Landscape Plants and Home Garden Produce”, while it doesn’t specifically address apple scab, does address ‘damaged’ produce. The publication states that: “cutting away the decayed or damaged areas of the [fruit] to at least once inch beyond the edge of the defect is generally effective for produce that is to be consumed immediately or promptly refrigerated”. See the full article.