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Ask Chef Walter: Canning Tomato Tutorial – Chef Walter Potenza
October 26, 2025/
by Executive Chef Walter Potenza, contributing writer
A long and demanding job that will pay off during the year when you open that preserves made with your hands and with a lot of love to season your favorite dishes.
Friends:
If Columbus hadn’t discovered the Americas, we wouldn’t eat tomatoes. However, it is a historical consideration of a large proportion because tomato is not only among the ten most consumed vegetables in the world, but it is precisely in Italy that it finds a per capita consumption among the highest ones, around 35 kg per year, about 60 pounds. Incidentally, the consumption occurs in Southern Italy, where most sauces use tomato as a base.
In 2024, the USA’s fresh tomato per capita consumption amounted to 19.32 pounds and is certainly climbing this year.
Lycopene enriches tomatoes with a bright red color, protecting them from the sun’s ultraviolet rays. It also protects our cells from becoming damaged as we age, and our bodies require more protection. Tomatoes also have potassium, vitamins B and E, and other nutrients. Read more on tomatoes.
As our mothers taught us, even before our grandmothers, people can seasonally preserve tomatoes by pureeing them. For many American Italian families here in Rhode Island, canning tomatoes still dominates the post-summer food activity of choice. Children and parents gather together, reaffirming the sense of seasonal festivity while honoring ancient traditions. Thus, it is imperative to share food values with the younger generation, who probably think tomatoes in a jar belong to an Instagram video.
In addition to being used raw, seasoned with a drizzle of olive oil, salt, and basil, or cooked as for a rich ragu, the secret to having it at home all year round is to prepare it in time and cram it into the cool temperatures of a basement’s cupboard.
Whether peeled, pulped, concentrated, or pureed, tomato puree’s taste remains unmistakable in the Mediterranean diet and is a source of inspiration for countless recipes. Still, pasta with homemade tomato puree remains the most authentic, timeless comfort food. While I am not sure you will tackle the ordeal, I can tell you that it may become more work than you had envisioned. Italians use a slogan: “Good food and good shoes do not compromise.”
Let’s get started!
1) Wash purchase tomatoes with plenty of cold water and remove any unwanted bruises.
2) Cut, grind, and filter the tomato puree.
3) Cook tomato puree until boiling, plus 15 minutes.
4) Sterilize the jars and the lids.
5) Pour hot tomato liquid into jars and seal.
6) Boil-filled jars in a large stainless-steel pot for 30 minutes on a simmer. No rapid boiling is allowed.
7) Remove hot jas, and allow cooling before shelving.
Equipment you need
Extra-large stainless steel pot (two of them)
Use one pot to sterilize the jars and lids. It is the same pot you use when making soups, stews, or meat sauces. The stainless-steel coating ensures uniform cooking while retaining heat and humidity inside. In the second pot, you boil the filtered tomato puree. When the tomato reaches the boiling point, allow 15 minutes and then shut off the heat. Set aside.
Vegetable mill.
Depending on the pounds of tomato you intend to make into the puree, you can use two methods.
1) Use a vegetable mill with a mesh between fine and medium to be turned manually.
2) An electric tomato squeezer to save you the effort of getting your arms tired.
You will also need a large metal bowl to collect the smooth and thick liquid before it goes on the fire.
You will need a sturdy sieve to filter the tomato pulp, thus obtaining a smoother and velvety consistency.
Set of glass jars.
At this point, remove your set to proceed to the last phase: bottling. Perhaps even before buying the tasty, top-quality tomatoes, you must organize yourself with glass jars for the preserving stage.
Sterilize jars.
It is essential to sterilize them before use by putting them in a pot full of water to boil. Sanitize the jars, dry them very well, and decant the tomato puree into them while still hot, using a funnel and paying attention to leave 1-inch clearance from the edge. Close the sterilized caps well, obtaining the hermetic seal guaranteed by the classic “POP.” You can now boil the jars in water using “Bain-Marie.” Allow cooling before storing in the pantry. A reasonably long and demanding job that will pay off during the year when you open that preserves made with your hands and with a lot of love to season your favorite dishes.
Note: For safety purposes, please add two tablespoons of lemon juice for each tomato passata (puree) quart. You can also use 5% white vinegar, about four tablespoons for each quart. Both will increase the acidity and pH level, prohibiting the development of botulism. Add the lemon juice or the vinegar to the jars before pouring in the hot puree and sealing.
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Chef Walter is featured HERE every Sunday with his regular Ask Chef Walter column!
Meet Chef Walter! There is a constant, recognizable thread in the career of Walter Potenza to elevate the level of Italian culinary culture in the United States. Besides his unquestionable culinary talent and winning business perspective, Chef Walter has been a relentless educator with passion and knowledge who defeats stereotypes. His life, career, and values are a model, an example to follow by any chef of Italian gastronomy working outside Italy.
Chef Walter appears regularly on National and International Networks such as Food Network, ABC, CBS, NBC, RAI, FOX, and Publications such as NY. Times, Washington Post, Wall Street Journal, Food & Wine, Saveur, Gourmet, and several Italian media outlets. And every Sunday in RINewsToday.com!
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