Today, sa国际传媒 food writer Eric Akis begins a new Sunday series, Ask Eric. He will answer readers' questions about cooking problems that have them stumped. If there is a cooking issue that has you scratching your head, send your question to Eric by e-mail at [email protected], by fax to Ask Eric at 250-380-5353 or by regular mail to Ask Eric, sa国际传媒, 2621 Douglas St., V8T 4M2
The question:
With the abundance of tomatoes at this time of year, I've been making cream of tomato soup, some of which I put into the freezer. How can I stop the curdling that occurs when I put the hot, cooked tomatoes into the hot milk? I end up relying on the blender to partially disguise this unsightly mess, although the flavour is still delicious with the recipe I have.
-- Heather Edwards, Saanich
Eric's Answer:
When milk is cooked with an acidic ingredient, such as tomatoes, it can cause the protein in it to cluster and cause curdling. I tested a number of recipes to see what methods were more susceptible to curdling and why.
A classic method for making cream of tomato soup is to stir cooked, strained tomatoes into b脙漏chamel (white sauce). The Joy of Cooking said to peel and seed the fresh tomatoes, before dicing, cooking and straining. The book Food That Really Schmecks didn't specify about peeling the tomatoes. In The Joy of Cooking recipe, a bit of sugar is added to the tomatoes to balance their acidity.
Both recipes worked fine, but because less b脙漏chamel was used in the Food That Really Schmecks recipe, it had a more tomatoey taste, which I liked.
The Joy of Cooking recipe with the peeled tomatoes, which were simmered with celery and onions before straining, had a more creamy taste that also appealed.
Removing the skins before cooking, and covering the tomatoes as they cooked, not mentioned in the other book, also gave me more juice when straining.
To prevent curdling, when making both recipes, I very slowly whisked the strained tomatoes into the b脙漏chamel. I thought if it were added all at once, like adding melted butter too quickly to egg yolks for hollandaise, the shock might cause curdling.
Once the tomatoes are incorporated into the b脙漏chamel, The Joy of Cooking recipe is ready to serve. However, in Food That Really Schmecks, you're asked to then simmer the soup five minutes. During simmering, I thought it might curdle if it bubbled too rapidly, but I did not have a problem.
Another recipe I found that used a b脙漏chamel base for the soup was in The Fannie Farmer Cookbook. In that recipe, three cups of chopped tomatoes are mixed with a half-teaspoon of baking soda. The baking soda, which I saw used in a few other recipes, is said to help neutralize the acid in the tomatoes. The tomatoes are then mixed directly into the b脙漏chamel, brought to a simmer and strained.
The method worked fine, but the recipe didn't warn me that once the baking soda hit the hot b脙漏chamel, foam would send my soup up and over the sides of the pot.
Out of curiosity, I made the recipe without the baking soda, and it did not curdle.
Another method I found for making a creamy tomato soup was to cook tomatoes in stock, with such things as onions and garlic, until very soft. You then pur脙漏e the mixture. In the book, Soup: A Kosher Collection, author Pam Reiss uses this method but when adding milk she says it often curdled. So, to make the soup creamy, she instead prefers to stir in the more stable whipping cream.
Missing from her soup was the flour found in b脙漏chamel-based soups. In my recipe testing, I found the flour holds the milk together (what makes it a sauce) and works to prevent curdling when tomatoes, whether cooked or raw, are stirred in.
Indeed, when I cooked tomatoes directly in milk without any flour, the milk always curdled.
The store-bought, on-the-vine tomatoes I used in all my recipe testing were not overly acidic. If you've grown your own tomatoes and they are a variety that is very acidic, that could cause curdling no matter what you do.
Reader Heather Edwards told me her recipe also did not use flour and ironically, was from an older edition of The Fannie Farmer Cookbook, published in 1979, where breadcrumbs were used as the thickener. The breadcrumbs obviously don't have the same holding power as flour does and I think that's why Edwards's soup is curdling.
At right and on page C12 are two recipes for making a tomato soup creamy.
If you would like to try the Fannie Farmer recipe I tested, published in 1996, go to epicurious.com and enter cream of tomato soup into the recipe search.
Eric Akis is the author of the best-selling Everyone Can Cook book series. His columns appear in the Life section Wednesday and Sunday.
FRESH TOMATO SOUP WITH OREGANO
This tomato-rich soup is given added richness by swirling in a touch of whipping cream just before it's served. It freezes well and the recipe could be doubled. If you do freeze it, add the whipping cream after thawing and reheating it.
Preparation time: 15 minutes
Cooking time: About 20 minutes
Makes: 4 servings
3 Tbsp olive oil
1 medium onion, halved and thinly sliced
1 to 2 medium garlic cloves, chopped 2 Tbsp all-purpose flour 2 1/2 cups chicken or vegetable stock 2 cups peeled, seeded and diced ripe, fresh tomatoes (see Note)
2 tsp brown sugar
2 to 3 Tbsp chopped fresh oregano
n salt and white pepper to taste
1/3 cup whipping cream
Heat the oil in a medium-sized pot set over medium heat. Add the onion and garlic and cook until tender, about 5 minutes. Mix in flour and cook 1 to 2 minutes more. While stirring, slowly pour in the stock. Mix in the diced tomatoes and sugar. Bring the soup to a simmer and simmer 10 minutes. Pur脙漏e the soup in a food processor or blender, or in the pot with an immersion blender. Mix in the oregano, salt and pepper. Return the soup to a gentle simmer. Stir in the whipping cream, heat through 1 minute and serve.
Note: You'll need 1 1/4 to 1 1/2 lbs. of tomatoes to get 2 cups diced tomatoes. To remove the seeds, peel the tomato (see recipe page C12), then cut each tomato in half. Set a sieve over a bowl. Pull the seeds out with your fingers, letting them fall into the sieve. Push any liquid around the seeds through the sieve. Add this liquid to the tomatoes after dicing.
CREAM OF TOMATO SOUP
Serve this creamy, comforting soup with soda crackers or grilled cheese sandwiches.
Preparation time: 25 minutes
Cooking time: About 30 minutes
Makes: 4 servings
1 1/2 lb. ripe, fresh tomatoes
3/4 cup diced celery
1/3 cup diced onion
1 Tbsp brown sugar
2 1/2 cups warm whole or 2 per cent milk (see Note)
1/3 cup butter
5 Tbsp all-purpose flour
* salt and white pepper to taste
* chopped fresh parsley
Bring a large pot of water to a boil. Cut the stem end out of each tomato and cut a shallow X at the blossom end. Plunge the tomatoes into the water 45 seconds, or just until the skins start to loosen. Set the tomatoes in ice-cold water; pull off the skins.
Coarsely chop the tomatoes and set them, and any juice on the board, into a pot. Add the celery, onion and sugar and simmer, covered, over medium to medium-low heat, for 20 minutes, or until the tomatoes are very soft. Set a sieve over a bowl. Strain the tomato mixture, in batches, into the bowl, firmly pushing on the tomatoes with the back of a ladle to squash out as much juice as possible (I ended up with 1 1/2 cups). Scrape the bottom of the sieve to get any juice out of it.
Melt the butter in a medium-sized pot set over medium heat. Mix in the flour until well combined. Cook, stirring, for 1 minute, and then remove from the heat. Very, very slowly whisk in 1 cup of the milk until well combined. Set back on the heat and, whisking steadily, cook until the b脙漏chamel (white sauce) starts to thicken. Very gradually whisk in the rest of the milk. Cook, whisking regularly, until the mixture comes to a simmer and thickens. Very slowly whisk in the strained tomato mixture. Season with salt and pepper and heat the soup through 1 to 2 minutes. Sprinkle servings with parsley.
Note: I warmed the milk in the microwave about 2 minutes
