Fruit Puree

blender-6311406Fruit purees, bright viscous liquid fruits, are a staple in a pastry kitchen. They are the base for sauces, ice creams, panna cottas, fluid gels, mousses, and glazes.

Most home cooks, even those that collect the cookbooks of restaurant pastry chefs, will be unfamiliar with the kinds of purees stocked in the pastry kitchen. Recipes, when translated for home use, call for the whole fruit and instruct you to give it a whir yourself in a blender, perhaps simmering a fruit first, but likely not. It’s a simple act, really. Just put the fruit in a blender, hit the highest speed, and voila! Liquid fruit.

However, a pastry kitchen, built on production cycles, would be slowed greatly if processing fruit was required every time you make a recipe. Instead, we keep fruit purees around. They are an ingredient, not a process, called for in our recipes in exacting grams rather than estimated pints of berries. To make this even easier for us, there are companies that purchase fields of berries at a time, process it in season, and tuck it away in a sub zero freezer to sell to us year round. Some are better than others, but adding fruit to a recipe in a professional pastry kitchen doesn’t always mean the whole fruit passes through our hands.

Dont’ freak out. It’s not the processed food monsters taking over our local foods movement. Often times, the fruits the puree companies are able to buy, in bulk, in season, at the source, is a much higher quality than what we can purchase whole. I’ve yet to taste a mango in chicago that can hold a candle to the alfonso mango puree I purchase. Strawberries have a short season, one that can be greatly effected by the summer storms here in chicago. The mara du boise berries that cap fruit puree company buys by the  fieldfull can, at times, outshine my local offerings, if the local offerings are even available. I am in great support of purchasing local fruits from the brave farmers in this region. But it’s not an option to walk into my dining room and say, this strawberry ice cream isn’t really very flavorful this week, but hey, it’s local. And if the local option isn’t available? Pureeing a clear plastic container of white centered strawberries? Forget about it.

So, we do at times order from the catalog of fruit purees, which come to us in 1 kilo containers, locked in icy preservation. We thaw them moments before they are used, and the resulting desserts are fruit forward, and above all, consistent.

However, at blackbird, we have started our own puree program. Its a money saving venture, if you look at the dollars and cents. The time it takes to process the fruit is lengthy, but makes use of pockets of down time in our cooks days, and gives our externs a chance to busy their hands while they make conversation with our cooks. The freezer space is often difficult to allocate, and managing the inventory over the course of the year takes effort. But it’s a worthwhile venture, and one I modeled after Sherry Yard’s similar program in LA. She took it one step further, securing freezer space in a produce merchants freezer, having them deliver her house made purees to all the pastry kitchens she managed when orders were placed for their produce.

Here at Blackbird, We bring in fruits from midwestern farms and orchards when the sun has ripened them, often working with the farmers to take over-ripe or seconds off their hands, and we process it ourselves. We spend the time to bring out the best of each fruit, simmering apricots and peaches until velvety, poaching cherries, letting black raspberries bubble until their musky scent is strong. Sometimes we roast stonefruits in the woodfire oven at Avec where juices evaporate as the fire embues the fruit with woodfire flavor. And the grapes, oh the grapes! They swell and burst on the stovetop with bright flavors before quietly simmering into luxurious submission. We leave the skins on our fruits, whick break down and add thick pectins to the purees, a time saving step that will prove doubly useful in sorbets giving them a softer, creamier texture. The cooked fruits are then sent for a ride in our super powered vita prep blender before we strain any pulp, skin, or seed from the liquid fruit. Packed into vacuum sealed bags, 1 kilo each, our purees stay frozen for use through out the year.

There are exceptions to every rule, and my strawberry and raspberry purees are just that. While they require no cooking, the berries themselves are by no means the least challenging of all our purees to produce. We put our berries through a freeze-thaw cycle before we take the time to puree them. It’s a process I’ve been using for years, and one I’ve written about before…….

“Why does freezing my berries make such a huge impact on the resulting thickness, color, and flavor?” The answer is simpler than I thought. Ice.

The information I found in On Food and Cooking discussed the damages ice crystals cause on vegetable matter when frozen, and how to avoid this. Because I am not avoiding this process, rather using it to my advantage, I went to Chris Young.

Anyone who has placed liquid in the freezer is aware that it expands. Thus, when we freeze our berries, the water molecules inside the cells expand. The sharp crystals of ice damage the cell walls of the fruit, causing for a better extraction of liquid, carrying both pigment and aroma molecules (Remember that flavor is made of 5 tastes on our tongue, and about a billion aromas in our nasal receptors).

So freezing makes for more release of liquid. Logically, more liquid would seem to make a runnier, thinner puree. But not so. What this process also does is break down the cell walls themselves. When the blade of the blender tears apart the cells, breaking them open to extract the liquid, it also breaks some of the cell wall down into particles small enough to remain in the puree. The damage from the ice allows for more of the cell wall to break down and become part of the puree and act to thicken it.

Finally, the freezing temperatures slow the enzymes that naturally deteriorate the bright hues of berries. Pureeing the fruit while still icy cold slows these enzymes from discoloring your fruit while the pigments are released.

If Dana circa 2006 doesn’t sound convincing, try it for yourself. The better your fruit, the better your puree, and those tender, sun-kissed strawberries flushed bright red are upon us! It does seem an outlandish step if you’re only pureeing 2 cups of strawberries once this year to flavor a home made ice cream. The benefit when you use puree every day is evident, but even for home cooks, the result is well worth the effort. You’ll be surprised how many uses you’ll find for bits of extra fruit purees if you have them lying around.

Simmered Fruit Puree

Strawberry and Raspberry Puree- freeze/thaw method

Roasted Stone Fruit Puree

Poached Fruit Puree