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Keep Berries from Spoiling and Blackberry Coulis

One of the biggest money wasters of your food budget is having to throw things away because they go bad before you can eat them.  This can be especially true for fragile produce like berries. Last year Eric and I picked two huge bucketfuls of blackberries, I made one cobbler, and the rest were all covered in mold the next day.  It was so disappointing!  Fortunately, I saw an article in the New York times on thermotherapy before we picked blackberries this year.

Thermotherapy (which my spell check keeps telling me should be chemotherapy!) is the process of dipping the berries into boiling water to kill of the bacteria that spoils your berries.  As Harold McGee says in the article “Fruits go moldy because mold spores are everywhere, readily germinate on the humid surfaces of actively respiring, moisture-exhaling fruits, and easily penetrate the smallest breach of their thin skins.” He did some experiments with different berries at different temperatures for different amounts of time and was astonished at how well it worked!

(Have you ever tried taking a picture of something you’re holding over a pot of boiling, steaming water? This was the clearest shot and I only got it by blowing the steam away with my lung power!)

I decided to do my blackberries for 30 seconds in boiling water.  I rinsed the berries, then put them in a mesh sieve.  I dipped that into the pot of boiling water, holding it there for 30 seconds, and then rinsed them with cool water immediately after.  One interesting thing I noticed is that the boiling water turned a lot of the blackberries a red color.  I spread most of them out on a cookie sheet to put in the freezer.  This helps them freeze individually instead of in a big clump!

Then a I filled a quart sized Ziploc bag with the rest of the heat treated berries.  They kept for 2 weeks in the fridge!  I’ve never had berries last that long!  I was shocked I was able to eat/use them all before they went bad.  This thermotherapy stuff really works to keep berries fresh longer.  Thank you Harold McGee!

I ended up making a blackberry coulis Monday with the last of the fresh berries, because Eric came home and told me he’d just gotten a great gig building a website that’s going to bring in some much needed money, look great on his resume, and give him a lot of confidence and new skills.  I was so proud I wanted to make him a special dessert.  The coulis (pronounced cool-ee) is a pureed and strained fruit sauce, so in this case it’s basically a seedless blackberry sauce.  This isn’t a technical coulis, because in the interest of saving dishes, I strained it without first pureeing in the food processor.  It made a thinner sauce but worked perfectly for the dessert I created.

I used a foley food mill to get the juice of the berries without the seeds.  I got mine at Goodwill, and often see them at different thrift stores for under $2.  If you want a thicker coulis, puree the sauce in a food processor, and strain the seeds through a seive.  For the dessert, I wanted something really simple that made only two servings.  If I make a whole pie or cake, we end up eating more dessert than we need.  So I decided to just make a few little shortbread cookies(using the simple shortbread recipe I’ve been making since I was a kid) , dollop them with whipped cream, and drizzle with the coulis.  It was so simple, yet so delicious! I made the full batch of shortbread dough, and froze the rest in a log wrapped in saran wrap, so I can just cut round cookies off as a I want to make more, like for tonight’s dessert!  Frozen blackberries are a great garnish.

Blackberry Coulis

makes 1/2 cup


1 cup blackberries
1 tsp lemon juice
1 1/2 TBS sugar


Combine ingredients in a small pot.  Bring to boil and reduce heat to low, cover and simmer for 20 minutes.  Every 5 minutes or so, mush the berries a little with a wooden spoon.  After 20 minutes, remove from heat.  For a thicker coulis, process in a food processor and then use a spoon to force it through a sieve and separate the seeds out.  For a thinner coulis, pass through a foley food mill.


makes 20-25 round cookies


4 ounces (one stick) of softened butter
1 1/4 cup flour
1/3 cup sugar


Use freshly washed and dried hands to mix the ingredients well.  The dough should be slightly crumbly but hold together when you press it.  For a full batch, press into a cookie sheet and cook 30 minutes or until pale tan.
For just five cookies, roll a little dough out to 1/4 inch thickness.  I used an espresso shot glass to cut five circles out of the dough.  Bake on a cookie sheet for 15-20 minutes, or until slightly colored.

Whipped Cream

makes about 1/2 cup


1/2 cup heavy whipping cream
1 TBS sugar
1/4 tsp vanilla extract


Combine ingredients and mix with hand mixer or immersion blender until thick and creamy.

Approximate cost/serving: In Washington, blackberries are a weed and free for the taking.  We buy our sugar and lemon juice in bulk so this ended up costing less than 5 cents for the coulis!  The whole dessert was about 50 cents to make, so 10 cents a cookie with cream and coulis.

Vegetarian/gluten free: Totally vegetarian.  For gluten free shortbread, try this recipe made with rice flour and cornstarch.

If you love Dianasaur Dishes, would you nominate me for a Foodbuzz Food Blog Award?  I so think my sister (who did the graphic design for my blog) deserves the Best Visual Blog Award!

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9 thoughts on “Keep Berries from Spoiling and Blackberry Coulis”

  1. Hey, Diana … if you see one of those Foley Food Mills at a thriftstore for 2 bucks, again, would you pick one up for me? I can actually afford $2. 🙂 I’ll keep my eye out, as well, but you might see one before I do.

  2. You definitely can Sharon (I mean Sundancer!). It’s also great over pancakes or waffles. As with freezing any liquid, just make sure there’s enough room for it to expand as it freezes. If you freeze it in a plastic food storage container, don’t drop it as you dig through the freezer, I’ve lost many a good container that way 🙁

  3. Hi my name is Katie. Thank you sooo much for the tip, im doing a project on strawberries and it took FOREVER to find an answer about Thermotherapy. Also i was wondering if i can have your full name because, we have to have a bibliography with it and i need the author of the article. If you don’t want to its okay. i’ll tell my teacher i couldn’t find it. So thank you for the tip again!
    from Katie. 🙂


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