Canning Santa Rosa Plums

Santa Rosa plums.

Santa Rosa plums.

Plum Jam and Jelly

We are enjoying a nice harvest of Santa Rosa Plums.  Today’s Project is preparing plum jam.  I ran a brief web search to review that basics.  The Steps in Processing Jams and Jellies  proves to be a good reference to read or reread prior to each day of jam or jelly making. When canning, the devil can be in the details. Miss a little step, you might give bacteria the opportunity to make your life very difficult. For this reason, updating the process in my blog prior to starting is a great way to review. I hope that you find it helpful as well.

I do modify some of the instructions largely because I have an aversion to lifting hot jars full of boiling water in and out of hot water baths. I find that the tools for lifting hot canning jars are less than secure and it is far too easy to drop a jar full of steaming hot water onto my feet.  I would much rather go for overkill with a pressure cooker or steamers where the jars are easier to lift and manage.

When I reviewed the reference sites this year, I either noticed information that I missed on previous years or the information has been updated.  The manufacturer of my pressure canner provides both boiling water canning directions for some jams, jellies and preservation of acidic fruit in addition to pressure canning instructions.  The directions also explicitly state that the use of pressure cooker canning method should not be used for some jams and jellies: rhubarb strawberry jam, grape jelly, peach jam, apple butter, pickles, and salsa. I also noticed explicit directions for slowly building pressure and dropping pressure while heating and cooling. I had problems with jars boiling over last year, I am hoping that my new awareness of these details will help prevent that problem.  We shall see.

Plum Juice

I simplify the juice extraction process.  I fill the stock pot of a pasta pot with filtered water up to the level of the bottom of the strainer insert.  Then I add the insert to the stock pot and put as many plums into the insert as I can cram in.   To the top of the plums I sprinkle about 1 cup of sugar.  I add the lid and heat the pot on the stove gradually.  The combination of sugar and steam softens the plums and juice started to trickle down to the bottom of the stock pot.  When the plums are tender, I use a potato masher to release more juice.  Then I move the strainer to a large bowel.  I elevate the strainer with plum mash by putting a smaller bowl upside down underneath.  This allows remaining juice to drain out.  The strained juice can be used as is to make jelly or frozen desserts.

I allow the plum mash in the pasta strainer to cool.  Then I remove plum pits.  I smash open the pits to expose the seeds for two reasons: 1. I have fewer plum weeds to pull the following year, and 2. The chickens like to eat the exposed seeds.  I toss the smashed seeds into the compost pile where the chickens forage.

Plum Filling

After pits have been removed from the mashed and drained plums, I put the remaining plum “meat” into a food processor and process until a smooth paste forms.  The paste can be used to make jam, chutney, pie filling, or used for in baking.  When I bake with the “plum filling”, I basically follow recipes that call for cooked pumpkin.  The moisture content is about the same, the substitution of  plum puree works out well.

Jar and Tool Preparation

I hand wash otherwise clean canning jars and tools with the hottest water I can stand. While hand washing, I check the jars for crack in the glass or chipped rims.  Jars with defects go into the recycling bin. Then I put the intact washed jars and tools into  the dishwasher in a cycle with hot water, “sani-rinse”, and heated dry.  I keep the dishwasher closed until I am ready to sterilize the jars. Then I either put the jars and tools in a steamer to sterilize them or sterilize them with a pressure cooker/canner for a minimum of 10 minutes/ 1,000 feet altitude.  Tools that might melt in steamer or pressure cooker are sterilized by immersion in a hot water bath for 10 minutes/ 1,000 feet elevation above sea level. I keep the cool jars covered in the steamer or pressure cooker until they are ready for use.

Tools to Sterilize in Advance

  • Silicon spatulas
  • Canning Jar Funnel
  • Magnetic Lid Lifter
  • Clean, natural fiber cloths/ dish towels
  • Canning Jar Lifter
  • Thermometer
  • Ladle
  • Metal slotted spoon

Other tools to have on hand

  • Clean potholders
  • Trivet or warm surface to put hot jars (Cold surface may cause hot jars to crack and spill hot contents. You won’t make that mistake twice.)


Lid Preparation

Cover new, unused canning jar lids with clean water in a small pot.  Make sure that they do not overlap – or they might stick to one another.  Boil lids for 10 minutes per 1000 elevation above sea level prior to use.  Use magnetic lid lifter to remove lids from water bath and put on jars. Be careful that the handle to the magnetic lid lifter doesn’t melt by contacting the sides of the pot. Hey designers out there, suppose a better product could be developed?

Role of Sugar in Jam and Jelly

Sugar has four functions in making jam: 1. react with pectin that naturally occurs in plum jam to thicken the juice into jam or jelly, 2. Protect the color and flavor of preserved fruit, 3. create an environment that discourages growth by many bacteria, 3. extract flavor and juice from the fruit,  and 4. add sweetness.  Some members of my family have health conditions that require severe reduction of sugar in their diets.  So, the less sugar that I use the better.  I tried to use no sugar pectin the first year I had plums.  It didn’t work.  I  got juice that never set. The second year I put one cup of sugar in a batch of jam and found that it was enough to set the natural pectin in the plums.  That jam was beyond tangy.  It made sour patch candies taste sweet. Supposedly artificial sweeteners tend to not take the heat in the canning process.  So, I just had everyone use the sweetener of their choice at the table.

Acid in Jam and Jelly

Acid (I use lemon juice) has the following functions: reacts with pectin and sugar to create a thickener that sets the juice into jam or jelly; preserves the color of the fruit, helps protect the jam or jelly from spoilage by bacteria, provides a tart & tangy taste. Plums often have enough acid (hence sour or tangy taste) on their own.  Therefore, many recipes do not call for the addition of an acid source to plum jams or jellies. I found that my plum jelly sets better with about 1 tablespoon of lemon juice.

Addition of Low or No Sugar Pectin to Plum Jam and Jelly

I found a handy Pectin Addition Chart for determining how much “Low or No Sugar Needed Pectin” I should add to plum juice to make a low or no sugar jam or jelly.  The chart recommends not exceeding 8 cups of plum juice per batch. According to the chart, my basic recipe for plum jam or jelly is as follows:

Ingredients for No Sugar or Low Sugar Plum Jam or Jelly

  • 8 cups Plum juice or mixture of plum juice and plum filling
  • 1 1/3 cups filtered water or fruit juice (use of apple juice will result in a sweeter jam or jelly)
  • 8 tablespoons low or no sugar pectin
  • Sugar, honey, sugar substitute of choice to taste ( none required for a very tangy product).  I found that the equivalent of 2 additional cups of sugar makes a nice sweet and tangy jelly.
  • 1 tablespoon lemon juice.

Filling Jars

Follow The Steps in Processing Jams and Jellies to fill warm sterilized jars.  Be sure to leave 1/4 inch air space at the top.

Take care to release any air bubbles that may be sticking to the sides of the jar or may be suspended in the jam or jelly.  Air bubbles can cause two basic problems: 1. They give any bacteria that might have survived the canning process a micro habitat to grow in; and 2) air expands and contracts with changes in heat and pressure.  I probably don’t have to elaborate on why you don’t want bacteria.  The expansion of air bubbles doesn’t sound like a big deal to inexperienced canner.  The first time you get jam or jelly exploding all over the inside of your canner, you will develop a new level of understanding of physics that you are unlikely to forget.  Long story short, the instructions for dislodging air bubbles will no longer seem excessively picky after a sticky wake up call.  Be sure to do the following:

  1. When heating the jam prior to filling the jars, remove foam as it develops on the surface of the jam.  Save the foam for a quick snack or add it to an icecream recipe where inclusion of air bubbles can be a good thing.
  2. Rub a non metal spatula along the inside of your jars after filling them to dislodge bubbles stuck to the glass.
  3. Gently tap the glass to shake loose suspended air bubbles.

After releasing air bubbles, dip the sterilized cloth in boiling water and use it to clean off the rim of jars before adding sterilized lids.  Gently add rings.  Be sure to adjust them so that pressurized air can leave the jars as they heat without dislodging the rings.  When the jars cool, the remaining air space (1/4 inch minimum) will contract and create a seal for the lid.

Canning Time and Pressure for Plum Jam

Based on the directions provided by the manufacturer of my pressure canner, plums should be processed (heated) at five pounds pressure for 10 minutes.  Since I live at about 3000 feet above sea level, the processing time is increased an additional 10 minutes for a total of 15 minutes processing time.  The processing time is in addition to the 10 minutes of heating the vent air before the lid is secured or the weights are added to create pressure.

The boiling water canning method calls for 20 minutes of processing time plus adjustment for altitude.

Cool Down

Let the pressure canner cool down slowly.  Accelerated cooling will result in the jam boiling over and creating a lesson in physics that you will remember.  Wait ten minutes after pressure had been released to loosen the lid.  Lift the jars straight up with jar lifters (hot!) to remove them from the canner.  Wipe down jars with the sterilized cloth dipped in boiling water. Gently tighten the rings.  Allow the jars to cool in an upright position for 12 to 24 hours.  Break fingers of  house hold members who try to sneak jam from cooling jars ;). Well maybe, just maybe, that might be a little extreme.  A better solution is to set aside some of the jam for them to eat while the rest of the batch is being canned:)


You are in for a well deserved treat! Tart, tangy and sweet plum heaven. Nut butters never had it this good.

Primary Sources of Information on Home Canning

Some of my favorite sites to visit for canning info include The National Center for Home Food Preservation in Georgia and UC Food Safety  which provides up-to-date publications on food preservation methods, such as freezing and canning, available from the University of California and other land-grant institutions.  Recommended pressure and cooking times for various crops are provided at  I like to check these sites every year before I start canning.  Any new information on food preservation will be posted on these sites.

My friend Rosemary Fritz Foster ,  suggested the 1995 edition of Joy of Cooking which has a really good recipe for plum chutney. She said that the current edition does not have this recipe. This is the best chutney She has ever eaten. Now I will have to track down the 1995 edition of the Joy of Cooking and try it. 

Santa Rosa Plum
Santa Rosa Plum

Additional Sources of Information

“PECTIN CALCULATOR for use with Ball low or no sugar added Pectin.” . ©2016 Hearthmark, LLC dba Jarden Home Brands All Rights Reserved. Distributed by Hearthmark, LLC dba Jarden Home Brands, Fishers, IN 46037, USA. Hearthmark, LLC is a subsidiary of Newell Brands (NYSE: NWL). ( Last accessed on June 22, 2016.

“Steps in Processing Jams and Jellies.” Elizabeth L. Andress, Ph.D., Professor and Extension Food Safety Specialist. Cooperative Extension The University Of Georgia, College of Family and Consumer Sciences in cooperation with the College of Agricultural and Environmental Sciences.  The National Center of Home Food Preservation. ( Accessed June 22, 1016.

“Preserving Food: Using Pressure Canners.” Reprinted with permission from the University of Georgia. Andress, E. (2011rev.) Preserving Food: Using Pressure Canners. Athens, GA: University of Georgia, Cooperative Extension.Cooperative Extension The University Of Georgia, College of Family and Consumer Sciences in cooperation with the College of Agricultural and Environmental Sciences.  The National Center of Home Food Preservation. ( Accessed June 22, 2016.

Pressure Canning Revisited.” Carolina Canning | A Clemson Extension Program. ( Accessed June 22, 2016.

“Using Boiling Water Canners.”  Elizabeth L. Andress, Ph.D. Professor and Extension Food Safety Specialist, Department of Foods and Nutrition. The National Center of Home Food Preservation. ( Accessed June 22, 2016.


“Atmospheric Steam Canners Can Provide a Safe Alternative to Boiling Water Canning for Acid Foods.” Carolina Canning | A Clemson Extension Program. ( Accessed June 22, 2016.


“Guidelines for Using an Atmospheric Steam Canner for Home Food Preservation.” University of Wisconsin Extension.

Home processing of acid foods in atmospheric steam and boiling water canners. Willmore, Paola, Mark Etzel, Elizabeth Andress, Barbara Ingham. 2015. Food Protection Trends 35 (3): 150-160


About Caliche Chick

I retired from a career as an Environmental Scientist and Botanist. My first career was teaching science and English as a Second Language (ESL), and content classes for ESL students at the middle school level. I also taught introductory biology at the community college level. I have an avid interest in plants that grow with little to no irrigation. I also keep a vegetable garden, fruit trees, and back yard chickens. When I am not in my yard, I am taking Construction Technology Classes at Victor Valley College and working on my "fixer upper" home.
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