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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.

Read more by Elsbeth Sites


Kombucha Brewing: The Ingredients

Photo credit: thedabblist (64636759@N07/Flickr)

Kombucha with SCOBY. Photo credit: thedabblist (64636759@N07/Flickr)

Craving some kombucha without the grocery store prices? Why not try brewing your own kombucha? As a fermented tea drink that is brightly effervescent, deliciously tangy, and slightly sweet, having some kombucha on hand could add a little spring to these cold seasons. On top of that, the brewing and fermentation involved in kombucha-making requires a little scientific know-how and quite a bit of trial and error to perfect the flavor to your liking. Think of it as having a science experiment in your kitchen!

At first glance, making kombucha appears fairly simple, as there are only four basic ingredients that go into it: water, tea, sugar, and a “Symbiotic Colony of Bacteria and Yeast,” SCOBY. If a flavored kombucha is desired, specific flavor ingredients can be added too. A cursory investigation into each ingredient, however, may bring up some questions. What type of tea makes the best-tasting kombucha? What is SCOBY and where can you source it? Is it possible to brew a sugar-free kombucha? Here is your scientific guide to making kombucha. We provide some scientific information regarding each component to help make an informed decision in choosing the ingredients that would create the kombucha that best aligns with your preferences.

SCOBY

What is it?

SCOBY is the most important component of kombucha, since it is the only thing standing between ordinary, sweetened tea and kombucha. Other fermented foods which utilize a similar symbiotic culture include kefir, ginger beer, vinegar, and sourdough. SCOBY is a grayish-white or beige, squishy mass floating within the brewed culture, and it is responsible for the distinct vinegar-like flavor, trivial alcohol content, and characteristic carbonation of kombucha. However, to call this leathery, stringy mat a symbiotic colony of microbes is a scientific misnomer. Biologically, a colony implies a coexisting group of individuals within the same species; a microbial colony is a cluster of microorganisms which have descended from a single cell, a common ancestor. SCOBY, on the other hand, is a symbiosis of multiple bacterial and yeast species cohabiting a cellulose matrix [1]. It may be more accurate to describe SCOBY as a biofilm, a colony of several microbial species attached to one another on a surface.

SCOBY

A symbiotic culture of bacteria and yeasts. Photo credit: Robert Anthony Provost (twon/Flickr)

As the name implies, SCOBY is alive. A study on the microbial populations existing in SCOBY reveals that the bacterial genus Gluconacetobacter is the most abundant [1]. Gluconacetobacter is responsible for the biosynthesis of the cellulose matrix that the SCOBY microbial population resides within. In other words, this genus of bacteria enables easy handling by creating the solid, stringy, floating mass that SCOBY is visually famous for. The next most abundant SCOBY bacteria belong to the genera Acetobacter and Lactobacillus [1], both of which give kombucha its acidic, vinegary taste by oxidizing ethanol to acetic acid and sugar to lactic acid, respectively. The yeast population of SCOBY primarily consists of the genus Zygosaccharomyces [1], which is notable for its high sugar, high alcohol, and high acid tolerance [2]. Yeasts in SCOBY generate CO2 and thus provide carbonation; they also produce alcohol, some of which is metabolized by Acetobacter into acetic acid. It is worth noting that the microbial composition of SCOBY may vary over time [1], possibly due to rapid growth, contamination, and/or random mutations. This compositional change may lead to flavor differences among different batches that have used the same SCOBY.

Where do I get it?

Home-brewing stores and online marketplaces are the more common places to buy SCOBY. For the more ambitious, there is also the option to culture SCOBY at home. Given that it is a collection of living organisms, you need to start with some pre-existing collection of kombucha microbes.

To make SCOBY at home, a modest amount of store-bought or homemade, unflavored and unpasteurized kombucha is required. Kombucha often contains a small amount of SCOBY left behind from the brewing process. To begin, place about 1 cup of kombucha with 7 cups sweet tea in a covered container and store for 1 to 4 weeks. In storage, the SCOBY microbes multiply and aggregate, with Gluconacetobacter synthesizing the cellulose that enables the microorganisms to grow together in that signature rubbery mass. For more detailed instructions, check out The Kitchn’s recipe for home-grown SCOBY.

Teas

Which tea?

Kombucha would not be kombucha without tea, but with so many varieties and forms to choose from, it’s easy to get lost. In general, teas are categorized by how the tea leaves (from the plant, Camellia sinensis) were processed, which affects the flavor, caffeine content, and color of the brewed liquid. Varieties among the basic tea categories arise from the geography of C. sinensis, growing conditions, time of harvest, and production processing, giving rise to notable flavor differences. The type of tea chosen will influence the prominent flavor profile of the finished kombucha. For the adventurous, different teas can be mixed together to create a unique kombucha flavor base.

Left to right: green tea, yellow tea, oolong tea, and black tea. Photo credit: Haneburger (Wikimedia Commons)

Left to right: green tea, yellow tea, oolong tea, and black tea. Photo credit: Haneburger (Wikimedia Commons)

  • Black: The most common choice for brewing kombucha, black teas undergo full enzymatic oxidation during production, which gives the drink a dark brown color [3]. Furthermore, complete oxidation of the tea leaves gives black teas a deep malt, caramel, or toasty flavor. This rich tea flavor enables a quick brew without flavor loss during kombucha fermentation.
  • Oolong: Literally translating to “black dragon tea”, oolong teas are partially oxidized, ranging from 8-85% oxidation depending on the tea producer. Oolong flavor profiles fall between the robustness of black teas and the delicacy of green teas, with tones ranging from smoky and buttery to floral and fruity, depending on the amount of oxidation the tea leaves were processed.
  • Green: During production, the oxidation process is stopped early; the tea leaves undergo minimal oxidation, giving green tea a more grassy, floral flavor when compared to other types of teas [3]. Due to their light and subtle flavors, green teas may have to be steeped many times for full flavor, and kombucha with a green tea base may have to be brewed longer.
  • White: Unlike the other teas, white teas are made using only the buds of the C. sinensis plant. Additionally, some white tea varieties use buds that have been steamed or baked, which inactivates enzymatic oxidation. The minimal or absence of oxidation gives white teas a very delicate and subtle grassy flavor, and so this tea may have to be steeped multiple times and a kombucha with a white tea base may have to be brewed for a long time.
  • Pu-erh: Pu-erh stands apart from other teas that use sinensis leaves by an additional fermentation step after the leaves are dried. Fermenting the tea leaves gives pu-erh teas a complex, sweet, earthy flavor profile that the other teas do not have [3].
  • Herbal: Unlike the above four categories, herbal teas rely on steeping plant parts that do not come from sinensis. Herbal teas are strongly advised against for kombucha brewing, as the plants that are used often contain volatile oils that have anti-microbial and/or anti-fungal activity. Some common anti-microbial volatile oils found in herbal teas include lavender oil (from lavender teas), peppermint oil (peppermint teas), and eugenol oil (chai teas) [4], all of which can destroy the bacteria and yeast in SCOBY. A damaged SCOBY will not be able to ferment or carbonate the kombucha batch.

Loose leaf or tea bags?

Tea bags are cheaper and easier to find at the grocery store, but tea bags typically contain fannings or tea dust, which are broken remnants of tea leaves. These remnants were either purposefully crushed for packaging into tea bags or are the leftover fragments after the loose leaf teas are packaged. In contrast, loose leaf teas cost more than their tea bag counterparts and are primarily found in tea specialty stores, but the leaves are much bigger than the fannings found in tea bags. The primary difference between loose leaf and tea bags are the size of the tea leaves, which will affect taste and brew time. Tea leaf sizes do not always correlate to the quality of the tea [5].

Where tea brewing is concerned, fannings have a much greater surface-area-to-volume ratio due to the small particle size, and so will brew much quicker than loose leaf teas. Furthermore, crushed tea leaves may increase the strength of the brewed tea [5]. However, loose leaf teas generally offer more complex, nuanced flavor profiles which tea bags lack. The form of tea to use for brewing kombucha overall depends on personal taste preferences.

Sugar

Which sugar?

At first glance, white sugar seems like the only option, given its ubiquity. For those wishing to experiment a little further, there is no reason to try other sugar sources, since the sugar-metabolizing microbes in SCOBY are not sucrose-specific. There are a couple of notes to consider when choosing the type of sugar:

Brown sugar is sucrose sugar that contains molasses, which may add a molasses flavor to the kombucha.

Raw sugar tend to have bigger crystals, since it is less refined. Bigger sucrose particles may affect its ability to completely dissolve in the kombucha, especially at or below room temperature. If the sugar crystals are not completely dissolved, there may be less sugar in solution available for the bacteria and yeast to metabolize. This could perhaps lead to a more yeasty, rather than fizzy kombucha.

Honey is a mixture of glucose and fructose, with its golden color deriving from non-sugar components such as pollen. Other microorganisms may also be found in honey [6], so using honey for brewing kombucha runs the risk of microbial contamination which may affect SCOBY efficacy.

Sugars extracted from plants or trees other than beets and sugar canes are fair game for brewing kombucha. A few examples include maple syrup, coconut sugar, and palm sugar. Agave nectar, despite health claims, contains a higher fructose content by weight than high fructose corn syrup [7].

Sugar substitutes, such as stevia, xylitol, and glycerol, are sugar alcohols. SCOBY is unable to metabolize sugar alcohols, and so adding artificial sweeteners would not be effective at all in brewing kombucha.

How much sugar?

In kombucha, sugar is used as a food source for the SCOBY, not as a sweetener as in many other recipes. The end product has far less sugar than was originally added to the first fermentation period, as the SCOBY has metabolized most of it to create the vinegary flavor and carbonation. Therefore, adding sugar is necessary for successful fermentation.

Too little sugar, and the SCOBY does not have the necessary fuel to undergo prolonged fermentation, leading to an unsweet, not very acidic, and possibly flat kombucha. Too much sugar may cause the yeast to over-proliferate, outnumbering the other SCOBY microbes. This both decreases the efficacy of the SCOBY and decreases the flavor and carbonation of the resulting kombucha. The exact amount of sugar varies among recipes, and can be experimented with to suit personal preferences.

Flavorings

For a more unique kombucha, flavors are often added near the end of the kombucha brewing process, after the batch has undergone its initial fermentation period. Just like every other component that goes into kombucha, the choices for flavoring are abundant.

Herbs and spices: Since herbs and spices tend to have strong flavors, adding a little bit can go a long way. Keep the amount to a minimum, as some herbs and spices may contain antimicrobial activity, and adding too much may harm the microbes on SCOBY, making the second fermentation period unlikely to occur successfully.

Fruits: Whether fresh fruit or fruit juice is used, be sure to keep an eye on the batch after adding the fruits. Fruits and fruit juices introduce an extra sugar source for the SCOBY during the second fermentation period; the yeast cultures in the SCOBY go into “overdrive” with this added amount of sugar. While this may lead to a fizzier kombucha, the increased carbonation will create a pressure-build up within the container. Opening the container may risk a small kombucha explosion or the container may burst open from the pressure built up.

Kombucha flavored with raspberries. Photo credit: Lukas Chin (Wikimedia Commons)

Kombucha flavored with raspberries. Photo credit: Lukas Chin (Wikimedia Commons)

Extracts and infused waters: Like herbal teas, be sure that the extracts are oil-free as to avoid volatiles that contain anti-microbial activity. A few examples of water-based extracts would be lemon extract (not lemon oil), almond extract, and vanilla. Infused waters include rose water and orange blossom water.

With a little bit of background knowledge, kombucha brewing could become your favorite science project. Explore the possibilities!

References cited

  1. Marsh, A. J., O’Sullivan, O., Hill, C., Ross, R. P., Cotter, P. D. Sequence-based analysis of the bacterial and fungal compositions of multiple kombucha (tea fungus) samples. Food Microbiology, April 2014; 38:171-178.
  2. C. Fugelsang, “Zygosaccharomyces, A Spoilage Yeast Isolated from Grape Juice.”
  3. Types of Tea. TeaSource. 2013.
  4. Thosar, N., Basak, S., Bahadure, R. N., Rajurkar, M. Antimicrobial efficacy of five essential oils against oral pathogens: An in vitro European Journal of Dentistry, Sept 2013; 7:71-77.
  5. Does the size of your tea leaf matter? Octavia Tea. 18 November, 2011.
  6. Olaitan, P. B., Adeleke, O. E., Ola, I. O. Honey: a reservoir for microorganisms and an inhibitory agent for microbes. African Health Sciences, Sept 2007; 7(3):159-165.
  7. Bowden, Jonny. Debunking the Blue Agave Myth. Huffington Post. 17 April, 2010.

Alice PhungAbout the author: Alice Phung once had her sights set on an English degree, but eventually switched over to chemistry and hasn’t looked back since.

Read more by Alice Phung


Cotton Candy

Summer would be incomplete without carnivals and bright, fleecy, sugary cotton candy. For a snack that’s nothing but sugar and air, there’s a surprising amount of physics and chemistry involved. Below are seven science-heavy facts about this feathery-light confection.

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Editor’s note: The original post stated that 1 ounce of cotton candy is 0.105 kilocalories, when in fact, it is 105 kilocalories, which is equivalent to 105 Calories. Thanks to our astute reader, Allison of the Internet for catching that! The post has now been updated (08-18-2015 10:06 p.m. PST)


Alice PhungAbout the author: Alice Phung once had her sights set on an English degree, but eventually switched over to chemistry and hasn’t looked back since.

Read more by Alice Phung


Caramel

Caramel flavor is a major component of desserts and candies, ranging from smooth, thick sauces to crispy, dark brown glazes of crème brûlées. Through caramelization, a browning process where sugar is heated to around 170 °C and broken down, over 100 compounds are formed that contribute to the color, flavors, and textures of what we know as caramel [1].

Photo credit: APN MJM/Wikimedia Commons

Photo credit: APN MJM/Wikimedia Commons

One simple way to caramelize table sugar is by heating: this process removes water from the disaccharide sucrose (a substance composed of two simple sugars) and breaks it down into monosaccharides fructose and glucose. Next, the monosaccharides react with each other to form new compounds, such as caramelan, caramelen, and caramelin [2]. These compounds aggregate to form brown particles of various sizes due to additional water elimination, contributing to the characteristic brown color of caramel. The stickiness of caramel can be attributed to the ring form of these molecules combined with the presence of free radicals [3]. Further, when in the presence of alkali, sulphite, or ammonia, these compounds can also result in colorants used in food products such as soy sauce and Coca-Cola [4].

In addition to these classic caramel compounds, many other molecules are produced that result in different aromas that contribute to caramel’s complex flavor profile, such as furans (nutty), diacetyl (buttery), maltol (toasty), and ethyl acetate (fruity) [3].

How to tune the flavor of your caramel? The temperature the sugar is heated to determines caramel flavor. “Light caramel” (180°C) can be used for glazes, is rich in flavor, and pale amber to golden-brown in color. By contrast, “dark caramel” (188-204°C) is dark and bitter in flavor due to increased oxidation of the sucrose molecules; it is usually used for coloring. Additional heating past this point will turn the caramel into a black and bitter mess, as the sugar breaks down into pure carbon [2].

Interestingly, caramel candies made with milk or butter do not undergo the caramelization process. Instead, the heating of the dairy product in the recipe causes Maillard reactions between sugar and amines that result in the brown color and flavors produced [1].

Next time you enjoy caramel flavor, you can revel in the smell and taste of all the aromas that result from complex chemical processes. Or, simply make your own with sugar, water, and a stove.

References Cited

  1. Caramelization.” Accessed 21 October 2014.
  2. Caramelization.” Accessed 21 October 2014.
  3. The Chemistry of Caramel.” ScienceGeist. Accessed 21 October 2014.
  4. E150 Caramel.” Accessed 21 October 2014.

Catherine HuAbout the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

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Sugar Chemistry of Hard Candies

Photo Credit: Adam Zivner (Wikimedia Commons)

Photo Credit: Adam Zivner (Wikimedia Commons)

Old-fashioned candy-making is a fascinating spectacle, if one ever gets the opportunity to watch. Fortunately, the Internet is full of videos like this one, which shows how hard candies (specifically, candy canes) are made by hand:

The process that turns ordinary, granulated table sugar into solid, glassy, hard candy is as dynamic on a molecular level as it is captivating to watch on an observable scale.

As a dry ingredient, table sugar comprises granules of sucrose crystals. Transforming these granules into a solid piece of candy begins by dissolving sugar—lots of sugar—in water. When stirred into water, the granules break apart into individual sucrose molecules. Hard candy recipes typically call for 2.5–4 parts sugar in 1 part water. However, sucrose has a solubility of only 2000 g/L, which is roughly 2 cups sugar in 1 cup room temperature water [1]. This is easily remedied by turning up the heat; sucrose solubility increases with temperature, meaning much more sugar can be dissolved in hot water compared to cold or room temperature water.

Boiling a mixture of sugar and water does more than simply allow larger volumes of sucrose to dissolve in water. As the temperature of the sugar solution rises, water evaporates and leaves behind the sugar in its molten form. This creates a very concentrated sugar solution. Different sugar concentrations correspond to different types of candies (Table 1). In the case of hard candy, confectioners and professional candy-makers typically bring the boiling sugar solution to about 150°C (302°F) before removing it from the heat.

Table 1: Stages of Sugar Cooking (Adapted from Crafty Baking.)

Stage Temp (°C/°F) Sugar conc. Candy examples
Thread 110-112/230-234 80% Sugar syrup, fruit liqueur
Soft ball 112-116/234-241 85% Fudge, pralines
Firm ball 118-120/244-248 87% Caramel candies
Hard ball 121-130/250-266 90% Nougat, toffee, rock candy
Soft crack 132-143/270-289 95% Taffy, butterscotch
Hard crack 146-154/295-309 99% Brittles, hard candy/lollipop
Clear liquid 160/320 100%
Brown liquid 170/338 100% Liquid caramel
Burnt sugar 177/351 100% Oops…

At this point, the sucrose has been concentrated to such a degree that it is considered supersaturated. Supersaturated solutions are unstable, in the sense that any type of agitation, such as stirring or bumping, will trigger sugar crystallization: sucrose molecules will transition out of the molten liquid solution into a crystalline, solid state [2]. Think of sucrose molecules as Legos; crystallization is the process of these molecules locking together into a solid structure. It may not seem like it, but crystallization is a big no-no in hard candies.

In broad terms, candies are categorized as crystalline or non-crystalline. Crystalline candies, such as fondants, fudges, and marshmallows, are soft, pliable, and creamy thanks to their sucrose crystal structures. Conversely, non-crystalline candies are firmer and include toffees, caramel candies, brittles, and hard candies. Unwanted crystals in these candies create a grainy, even gritty, candy texture. Hindering the crystallization process is crucial for making a successful batch of hard candies.

This is where corn syrup, another key candy ingredient, plays an important role. Corn syrup consists primarily of starch, which is nothing more than a string of sugar (glucose) molecules linked together. When heated, the starch breaks apart into its glucose components. These glucose molecules are smaller than sucrose and can impair crystallization by coming between the sucrose molecules, ultimately interfering with crystal formation [2]. In some recipes, invert sugar or honey may be added in lieu of corn syrup. Invert sugar and honey are both mixtures of glucose and fructose, which impede sucrose crystallization the same way as corn syrup.

During the final stages of candy-making, the sugar solution is poured onto a cooling table. As it cools, it takes on a more solid, plastic-like mass that is still very pliable. Flavors and dyes are added at this stage. Sometimes an acid, such as citric acid, is also added. These acids further prevent sucrose crystallization by hydrolyzing sucrose molecules into their basic components: glucose and fructose. The sugary mass is then aerated, often by rolling, pulling, or folding, so that it cools down quickly and becomes more solid. This is the creative stage in which the candy-maker kneads, rolls, molds, and cuts the candy into its final shape.

Hard candy is ready to eat once it cools down to and hardens at room temperature. At its completed stage, hard candy is similar to glass: it’s an amorphous solid that is shiny, rigid yet fragile, and sometimes transparent.

Who knew such simple, little candies could be so complex?

References cited

  1. Sucrose, International Chemical Safety Card 1507, Geneva: International Programme on Chemical Safety, November 2003.
  2. Ouiazzane, S., Messnaoui, B., Abderafi, S., Wouters, J., Bounahmidi, T. Modeling of sucrose crystallization kinetics: The influence of glucose and fructose. Journal of Crystal Growth, 2008; 310: 3498–3503.

Alice PhungAbout the author: Alice Phung once had her sights set on an English degree, but eventually switched over to chemistry and hasn’t looked back since.

Read more by Alice Phung


“It’s all about sugar” – Barbara Spencer

Barbara Spencer of Windrose Farm in Paso Robles was our lecturer on the topic of phase transitions. 

“Why are carrots harvested after winter particularly sweet?”

Plants use sugar as an internal antifreeze. This is an example of the concept of freezing point depression. When a solution freezes, the molecules into a crystalline structure. However, when impurities are introduced to the solution, they block the molecules from clustering together and freezing. In the case of carrots, sugar is the impurity, and it keeps the liquid inside the plants from freezing at 0 °C. This defense mechanism against frost translates into carrots that taste extra sweet to us. Even on a daily basis, Barbara always picks her carrots and melons before the sun comes up, because sugar levels increase at night. Strawberries ripen at night, too.

Image courtesy of farmstayus.com

Out where the farm is in Paso Robles, the valley makes for a very active microclimate. The difference between daily temperature highs and lows can be as large as 50 °F. Apples, which need a certain number of hours of frost, thrive well there.

Storage is just as important as growth, and Barbara invested in a refrigerated truck for transporting vegetables. Leafy greens always need water, and this is why supermarkets and farmers are always spraying or misting. There is a rule of thumb that every hour lost in not cooling freshly picked vegetables to the proper temperature equals one less day of shelf life.

We were surprised to learn about the storage capabilities of some apple varieties, such that you can keep them for months on end. They’ll be good right after picking, become very gnarly quickly, and then, if you wait long enough, they’ll taste fantastic again. Which varieties do you know are like that?