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Maple Syrup

Photo credits: flickr/Doug

Photo credits: flickr/Doug

Nothing sets the tone for a drowsy Sunday afternoon like a breakfast that features maple syrup. This sticky and wonderful syrup fills the nooks and crannies of our nation’s waffles with the taste of autumn and the smell of Canada. Let’s take a moment to appreciate the science that makes maple syrup and its confectionery relatives the crown jewel of breakfast condiments.

Generally, syrups are made by extracting sap from plants and boiling them down so they become a more concentrated and viscous liquid. The sugar maple tree, Acer saccharum produces the sap that can eventually become maple syrup, as it produces sap in greater quantities than other maple varieties.

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Optimal conditions for sap harvesting involve extreme temperature fluctuations from day to night. The northeastern United States and eastern Canada, of course, have just the night-day temperature shifts to produce quality maple sap. The traditional sap-seeker drills a small hole into the cambium, or woody tissue, of a maple tree, and inserts a spout. On warm days when temperatures are above freezing, the liquid sap expands and creates positive pressure in the xylem – the plant version of veins; this pressure pushes sap out of the tap hole and into the collection vessel. When night falls and temperatures drop below freezing, sap contracts as all liquids do when chilled. As the sap contracts, this creates negative pressure, which sucks water from the soil into the roots and the tree; this replenishes the sap that has bled out of the tap hole.

Photo Credits: flickr/Chiot's Run

Photo Credits: flickr/Chiot’s Run

After harvesting, the harvested sap is boiled down until it has a viscosity of about 150-200 centipoises – a viscosity very similar to that of motor oil. When the liquid has reached this consistency, it has undergone a 40x reduction in volume. The resulting syrup is approximately 62% sucrose, 34% water, 3% glucose and fructose, and 0.5% malic acid, other acids, and traces amounts of amino acids. The distinct and lovely aromatic notes of maple come from wood byproducts like vanillin, other products of sucrose caramelization, and products of Maillard reactions between the plant sugars and the amino acids.

Photo Credits: flickr/LadyDragonflyCC

Photo Credits: flickr/LadyDragonflyCC

Another delectable treat from Northern climates is maple sugar. Maple sugar is made by boiling maple syrup (which has a boiling temperature 25-40°F above the boiling point of water, but varies with altitude) to increase sucrose concentration, then letting the syrup cool. Left alone, the sucrose accumulates into coarse crystals that are thinly coated with the remainder of the syrup. Simply put, maple sugar is plain table sugar with a natural coating of maple flavor.

Photo Credits: flickr/cdn-pix

Photo Credits: flickr/cdn-pix

A luxury to smear on your toast or pancake, maple cream is surprisingly simple to make, and despite its name, doesn’t contain any dairy. This delicious creamy spread is a malleable mixture of very fine crystals that are dispersed in a small amount of syrup. Maple cream is made by cooling maple syrup rapidly to 70°F by immersing its container in ice water, then beating it continuously until it becomes very stiff; thereafter it is warmed until it becomes smooth and has the texture and viscosity of a runny buttercream frosting.

Photo credits: flickr/ Anne White

Photo credits: flickr/ Anne White

One last note on maple syrup – beware of imposters! If the bottle doesn’t say maple syrup, it is not maple syrup. Breakfast or pancake syrup disappointingly consists of corn syrup and artificial flavors.

Works Cited

  1. “Learn about the Science of Maple Syrup.” Cary Institute of Ecosystem Studies. N.p., 24 Mar. 2013. Web. 25 Nov. 2015.
  2. McGee, Harold. “Sugars and Syrups.” On Food and Cooking: The Science and Lore of the Kitchen. 1st ed. New York: Scribner, 2004. N. pag. Print.
  3. “Viscosity Comparison Chart.” Viscosity Comparison Chart. The Composites Store, n.d. Web. 25 Nov. 2015.

Elsbeth SitesAbout the author: Elsbeth Sites received her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

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Chia Seed Apple Pie

Continuing our Science of Pie adventure, we’ve invited Elsbeth Sites of Team Chia to share her pie science project, which examines the use of a very unconventional thickener to tune the viscosity of pie filling.  Elsbeth is an undergraduate student of physiological sciences at UCLA who is passionate about food and writing, especially writing about food.

Have you ever baked a lovely pie, sliced it and placed it gently on your best dessert plates, then watched in despair as the filling fled its warm crust and bled all over the dish? This common and unfortunate experience led our team to investigate the viscosity of pie filling. We hoped to discover a way to produce a pie of perfect viscosity that upon slicing, would not spread over the plate too far, nor be too gelatinous. Most pies contain cornstarch to thicken their fillings. To make our project unique and to put a modern and healthy twist on our pie, we replaced starch with the trendy new superfood: chia seeds.

The outside of the chia seed contains large fibrous molecules called polysaccharides. When the seed is wet, these molecules are exuded from the seed and trap liquid. This allows the seed to hold approximately nine times its own weight in water, causing a bead of gel to form around the seed [1].

Chia seed hydration. Chia seeds can absorb approximately nine times their weight in water. Water absorption creates a mucilaginous gel around the seed. Figures are from [1].

With this knowledge of the chia seed, we posed these questions:

  • How do we create a pie that does not bleed across a plate when sliced while not being overly gelatinous?
  • Can chia seeds be used to increase the viscosity of our pie filling?
  • At what concentration should the seeds be added to the pie to get an ideal viscosity without compromising taste or texture?
Measuring viscosity with the “line spread” test. The line spread test measures the distance a liquid or semiliquid flows across a flat surface. We used a hard, clear, plastic surface marked with concentric circles spread 0.5 cm apart across a 7.5 cm radius. Lines originating in the circles’ center divide the circles into four quadrants. The longest distance traveled by the filling in each quadrant was averaged to find the mean distance that the filling spread.

We defined our perfect filling to be one that spread slightly when placed on a flat surface without remaining too gelatinous and not spreading at all. A traditional apple pie filling prepared with cornstarch spread 5.6 centimeters in 60 seconds. Finding the right concentration of seeds to add was a tedious process, and the heat at which the pie was baked and served greatly affected the pie’s viscosity. As shown in the figure above, our control filling with no thickening agent spread on average 5.9 centimeters in 60 seconds—clearly too runny. The filling to which we added 0.5 teaspoons of chia seeds spread 5.5 centimeters. By evaluating these spread distances and tasting each filling, we agreed that the filling with only 0.5 teaspoons seeds yielded the best viscosity and palatability. Using more seeds than this overpowered the spices in the filling, making the pie taste nutty and giving it a slimy mouthfeel.

Our experiment was successful in that we answered our original questions:

  • Chia seeds can indeed be used to tune the viscosity of apple pie filling.
  • To produce an apple pie of optimal viscosity, replace cornstarch with 0.5 tsp chia seeds per ½ cup of filling. While our pie might appeal to the culinarily curious or health savvy, those who prefer a classic pie may find the seeds of the pie annoying, or might miss the texture that more traditional thickeners like cornstarch or flour provide the filling.

If a seedy apple pie up your alley, here is Team Chia’s recipe for Chia Seed Apple Pie. The truly adventurous might even try using chia seeds in a berry pie where thickening agents are more crucial and tiny seeds are less noticeable. If you do try another variation of a chia seed pie at home, let us know how it goes in the comments below!


Pie Crust
Adapted from Everyday Food: Our Best Pie Crust

2 1/2 cups all-purpose flour, plus more for rolling dough
1 tsp salt
1 tsp sugar
16 tbsp (2 sticks) cold unsalted butter, cut into pieces
4 tbsp ice water, plus 2 more if needed

In a food processor, pulse flour, salt, and sugar several times to combine. Add butter. Pulse until mixture resembles coarse meal, with just a few pea-size pieces remaining.

Sprinkle with 4 tablespoons ice water. Pulse until dough is crumbly but holds together when squeezed with fingers (if needed, add up to 2 tablespoons more ice water, 1 tablespoon at a time). Do not over-process.

Turn dough out onto a work surface; form dough into two 3/4-inch-thick disks. Wrap both separately and tightly in plastic, and refrigerate until firm, at least 1 hour.


Pie Filling and Assembly

5 Granny Smith apples, sliced
3/4 cup granulated sugar
2 1/2 tsp chia seeds
1/2 tsp ground cinnamon
1/8 tsp ground nutmeg
1/2 cup cold water
3/4 cup apple juice

Preheat oven to 350 degrees.

Wash, peel, and core apples. Cut apples into 1/4- to 1/2-inch slices and place in cold water.

Combine sugar, chia seeds, and spices in a large pot with water and apple juice. Stir and cook on medium high heat until mixture thickens and begins to bubble. Boil for 1 minute, stirring constantly. Fold in apple slices immediately and remove from heat.

To assemble pie, roll dough into 2 14-insh rounds. Fit the first crust into the bottom of a 9-inch pie plate. Spoon filling into the pie dish. Cover the pie with the second crust, trimming the overhang to about 1 inch. Press upper and lower crust edges together and flute as desired. Cut steam slits in the center of the top crust.

Bake for 20 minutes at 350 degrees or until crust is golden brown.


References Cited

  1. Muñoz LA, Cobos A, Diaz O, Aguilera JM (2012) Chia seeds: Microstructure, mucilage extraction and hydration. J Food Eng 108: 216–224. doi:10.1016/j.jfoodeng.2011.06.037.

Josiah Citrin on Viscosity in French Sauces

Josiah Citrin visited class to discuss viscosity’s role in sauces and its effect on flavor and mouthfeel. Josiah is the chef/owner of Mélisse in Santa Monica and co-owner of Lemon Moon in West LA. 

Using the sauces that he brought for us to taste, Josiah traced out the evolution of sauce making from pre-1970s to present day. Traditional French sauces are sually thickened with a mixture of cooked butter and flour (roux). Consequently, they were thick and heavy on the palate. Then, in the 1970s, a shift towards more delicate preparations and sophisticated presentation took place. This nouvelle cuisine caused cooks to prepare sauces with less flour, relying more upon high quality butter, vinegar, and other less viscous liquids. In the 1990s and 2000s, the introduction into restaurant kitchens of techniques and ingredients previously only found in industrial food preparation saw the use of Ultratex 3, tapioca starch, xanthan gum, and other additives in sauce making.

A taste test of red wine sauce made 3 ways made this evolution particularly clear to us:
i. thickened with flour
ii. thickened with puréed shallots and butter
iii. thickened with Ultratex 3 (a tapioca-derived starch)
While the viscosities of the sauces were similar, the taste differences were quite striking. Each additive has its particular taste, and heat also creates new flavor molecules out of the base recipe.

A few of Josiah’s tips for sauce-making:
1) When making hollandaise, add salt at the beginning of preparation, before adding butter.
Why? Salt (NaCl) and water are both polar molecules, which means one part of the molecule is negatively charged while the other part is positively charged. Generally, like dissolves like, and water does dissolve salt very well. However, fat is nonpolar, and salt does not dissolve well in it. Thus, to make evenly salted hollandaise, make sure to salt while the sauce is still mostly water.

2) To make a very light and airy sauce, such as the mint cilantro cashew sauce, set with gelatin and foam with an iSi siphon.
Why? The iSi siphon produces a temporary foam consisting of air bubbles entrapped in a network of sauce molecules. However, the bubbles are unstable and will merge, causing the foam to quickly deflate. Introducing gelatin to the sauce, however, strengthens the network and extends the lifetime of the foam.

3) Need to keep sauces warm? Store them in thermoses instead of in open containers in water baths.
Why? Sauces stored in open containers will evaporate, and the flavor and mouthfeel will change due to the reduction of volume. Capped thermoses are perfect at trapping heat and also preventing evaporation.