Thickening Tomato Sauce

Joined Jan 15, 2008
One of the things that I love to make is homemade tomato sauce. it tastes so much better than the stuff at the store, and it is just extremely satisfying. I run a couple of cans through a mill to remove the seeds and membranes, heat up the juices and pulp with the rest of the ingredients, bring it up to a simmer, and reduce it. My problem is that the sauce is still fairly runny. I have heard of using cornstarch for thickening some sauces. What are some effective ways that I can thicken the sauce?
Joined Jun 27, 2006
You may not like the answer but you need to cook it longer. When O do my sauce with fresh tomatoes it simmers for close to 12 hours. Usually I make it the day or so before I need it. That way I don't have to do all the cooking in one day. Helps the flavor too. If you're going to go through all the trouble of preparing the tomatoes for cooking why throw in paste.

Paste has it place. I use it but not with fresh tomatoes.

You can also cut your tomatoes the day before you need them, place them in a china cap, collander or chinoise and drain them into a bowl over night. This will also remove a good deal of moisture. :)


Staff member
Joined Mar 29, 2002
A number of issues here

Canned Tomatoes
Canned tomatoes can be surprisingly good or plain awful. It sounds like you're using whole tomatoes, a good start. But what are they packed in? As a generalization, puree is better than juice which is better than water. Read your ingredients to find out what you've got. This is probably one of your problems with runniness.

Also look at additives. There are usually two: Salt and Calcium Chloride. Salt offers some flavor and preservative effects. Calcium Chloride has a very salty flavor, is a firming agent as well. Purists avoid the calcium chloride. I have a sodium restricted diet so I actually use a brand with only tomatoes and calcium chloride which works well for me.

I do have to give props to Pomi brand tomatoes whose aseptic packages list but one ingredient: Tomatoes. I used Pomi exclusively when I lived in Germany and was very happy with the product. They're quite a bit more expensive here in Europe.

Muir Glen is a respected quality brand of canned tomatoes in the US and can be had at reasonable prices on sale, but is otherwise expensive in my book. I stock up at sales.


Thickening may not be what you want to do really. It depends on what you want to do with it.

The more you cook a tomato sauce, the less tomato impact it tends to have. There are times this is what you want such as a bolognese with a more blended meaty flavor.

But for pizza or marinara, a fresher tomato taste is generally desirable.

Here are some ideas you may find useful.

Drain your tomatoes and reserve the liquid. Lightly crush the tomatoes and drain again adding that liquid to the reserved liquid.

Mill your tomatoes as normal. You could add in the amount of liquid you want for the sauce so you have the fresh taste of a less cooked sauce. Or you might try reducing the liquid and blending that into the solids. I'm not sure where the flavor profile would end up though.

Joined Aug 27, 2007
When I simmer a sauce that I know will take a long time to thicken, I do it in the oven at about 250 degrees. Then I don't have to stir it as often to keep it from scorching.
Joined Nov 19, 2007
I'm with old school on this one. Even my Marinara sauce gets a good 6 hours of simmer before I finish it. Slurry in tomato sauce is a travesty of justice. The other possible issue is that your sauce is not homogenous. If you have a lot of chunky solids and separate water, a couple of pulses with an immersion blender helps. Just don't kill it or you will have ketchup. Also, when I finish my sauce I mount it with a good bit of extra virgin olive oil. This helps to emulsify the sauce and give it body. It also gives Marinara sauce much needed fatty richness.
Joined Jun 6, 2007
Hi French Foodie,

There is good advise here already.

Here are my observations:
Choose quality tomatoes.
as already stated, simmer, simmer then simmer longer.

Regular home cornstarch will not hold too long in an acidic environment like tomato sauce.

Add lemon juice, the added acid will help the natural pectin to firm up. (citric acid is better if you can find some).

If all else fails, add tomato paste.

Luc H.
Joined Jan 15, 2008
Thank you all for the information. Here's a bit more info on what I used for the sauce.

The tomatoes were canned in juice. I'm not sure about the additivies, but they didn't taste salty to begin with. I don't have any cans lying around currently either. When I made the sauce I sent the whole tomatoes through the mill, and then combined all the ingredients (pulp and jucie from tomatoes, and extra juice from the can) to the pot. It seems that my main problem may be the adding of the juice from the can. That would make sense for the runniness of the sauce.

The flavor profile on the sauce tastes good, it's just really runny (due to the extra juice?) I'm not trying to get the sauce extremely thick, but less watery than it currently is. I'm trying to stay on the cheaper side, due to a college budget, but I also love good food.

Phatch: Do you find the flavor of sauce made with fresh tomatoes leaps and bounds above canned tomatoes? If so, is it best to just wait until the summer, go to some farmer's markets and make a huge batch then? My only concern is that fresh tomatoes can be pretty costly.


Joined Dec 20, 2006
When I make sauce using canned tomatoes, I prefer the juice to the puree. I drain the liquid, hand crush the tomatoes, and simmer in a skillet or saute pan to allow for more rapid evaporation. After the sauce has drained, I add back some liquid and add a little red wine. I can make a nice thick sauce in about 1/2 - 45 minutes.

Joined Apr 18, 2013
Well, I was just here looking at what other people did to thicken tomato sauce. Here's exactly what I did:

1. I picked about 2 handfuls of cherry-tomato (i'm not positive what kind of tomato it is) sized tomatoes, washed them, and cut off the stems. 

2. I cooked (not really carmalize) diced onions of half a medium-large onion with good amount of olive oil. (BTW, its cooking the whole time while you're preparing the next item to add. no need to wait to turn on the fire.)

3. add tomatoes and 3-5 tablespoons of bought tomato sauce. (I don't know about the results if you skit it. It was just around the house and I said, "why not?" and it is organic and everything. trader joes

4. add rosemary or any herb bunch tied by string (my younger sister hates flecks of herbs in her food)

5. I added a small handful of chopped (or minced) cilantro. (i prefer the flavor to parsley)

(BTW, its cooking the whole time while you're preparing the next item to add. no need to wait to turn on the fire.)

6. After cooking awhile (10 min about) add squeeze of lemon juice and pinch of flour.

7. cook for 20-30 more min.

Joined Aug 8, 2013
For thick sauces we use our own tomatoes. After processing we take the large 20qt pans and place them in the refrigerator overnight. This allows the pulp to separate from the water. Ladling off the pulp into another stainless pot we then begin the sauce. This makes a huge difference in thickness. No vast cooking times needed...saves energy. Cheap and Easy.../img/vbsmilies/smilies/smile.gif.
Joined Jul 13, 2012
I'm going against the grain here.  When I make tomato sauce for spaghetti I cook it 30 - 40 minutes.  I finish cooking my pasta in it and the sauce gets absorbed into the pasta.  I detest a blob of sauce on top of a pile of spaghetti.
Joined Apr 3, 2011
FrenchFoodie says nothing about fresh tomatoes, so I'm rolling with my opinion in regards to canned.  Here's my process for a tomato sauce for the home.

Decent olive oil.  A bit more than you might think.

Slowly toast a garlic clove or two in the oil.  Add your whole tomatoes (I like Muir Glen or Alta-Cocina) with juice and gently crush with your hands.  Should be nicely smashed, but doesnt need to be perfect.  Salt and pepper.

Cook on medium heat until the consistency you want.  I personally dont like cooking low and slow because the sugars caramelize too much and I end up with a sweeter sauce.  I prefer a more acidic tomato base so, for me, quicker is better.  At the end I typically invert a small bunch of basil into the sauce and let it cool to room temp.  Remove the basil and youre good to go.  You can either smash up the garlic cloves with a fork or just remove them.
Joined Nov 7, 2011
Just keep simmering longer.   Xanthan gum will do a good job of thickening sauces but use a very small amount.  A little goes a long way.
Joined Mar 19, 2009
A friend of mine, Italian, after many years cooking tomato sauce the classic way, is lately roasting the fresh tomatoes alla Alton Brown, with good success.
Joined Sep 3, 2013
Question:  I like the idea of putting the 20 quart pot in the fridge overnight.  Only question is when you remove the pulp is it the pulp to make the sauce or what is left in the pot?
Joined Jul 13, 2012
Question:  I like the idea of putting the 20 quart pot in the fridge overnight.  Only question is when you remove the pulp is it the pulp to make the sauce or what is left in the pot?
I score and blanch my tomatoes before pealing and I like to get as many seeds out as I can at that point.  I season them well and put them in the food proc to mince them down.  I don't own a food mill at this time so I have to do it old school which means more manual labor.  I mince my tomato through a strainer and push it with a spatula made for that purpose.    Before this new appliance age we did things the old school way. .  . by hand so don't be put off by what you don't have.  IMPROVISE - In fact - it goes like: Adapt, improvise, overcome. - best of luck love.
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Joined Aug 13, 2006
I wonder how thick you want it.  Do you want it to mound up if you pick up a spoonful?  then i think you can't really make a decent sauce that thick without sacrificing flavor.  If your sauce is truly watery, strain the tomatoes from the can before adding.  If you cook with chunks of carrot, celery and onion until these are soft, you can run through a food mill or use an immersion blender and it will be thicker. 

I would never cook a sauce more than an hour.  Most of my sauces are cooked on high heat for a very short time.  If, however, i'm making a ragu, then it has to simmer slowly.  A marinara, it seems to me, needs to be as close as possible to fresh tomato consistency

I've never cooked pasta in the sauce, and i doubt i would like it (i imagine it would get a more "creamy" consistency, and that's not how i like my sauce) but you might try that if the sauce seems watery.  Or half-cook it and then finish cooking in the more watery sauce. 

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