pear conference and doyenne

Science of Pears: From Harvest to Cake

Every year in August/September our pear trees give us a good supply of pears. They’re not the pretties, but sure are tasty. We have two types: Conference and Doyenne du Comice and once they start coming off that tree we have more than we can eat. So it’s a good time to experiment with pears! And experimentation is what we love doing best :-). Cakes, pies, jams, we put the pears in anything we can think until they’re all gone.

Along the way, we’ve learned a thing or two about these delicious green fruits. About time we dig into the science of pears!

Introducing: Pyrus

The pears that we’re referring to belong to the genus Pyrus. There are quite a few different types, some are round, like an apple, but they’re more well known for their round bottom and slightly longer elongated top. A lot of pears are green, but some varieties (e.g. the Asian pears) are more yellowish in color. They grow on trees and shrubs in mostly more moderate climates.

They very definitely aren’t prickly and thus are something very different than prickly pears. Even though prickly pears are called pears, they are not related. Instead, the prickly pear is the fruit from a cactus species and is not related to the Pyrus pears!

Importance of harvest for pears

One of the pear’s special features is when a pear should be harvested. Most fruits (though not all) are at their best when harvested when ripe (which doesn’t mean they’re always harvested when ripe, but ideally, that’s when they’d taste best). However, this is not the case for pears. Instead, pears should actually be harvested before they ripen, leaving them to ripen off the tree (it’s a climacteric fruit).

If you do harvest pears only once they’ve ripened they will have started to develop a woody structure within the pear. The plant does this to protect the pear, but it, unfortunately, gives the pear a gritty texture that is not so pleasant to eat. Once it has been formed, the woody structure will not be able to disappear. Even not during further ripening and softening either.

When pears ripen off the tree they will not form this woody texture. Instead, they’ll remain juicy and during ripening, they will turn softer and moister, even mushy, if kept for too long. Ripening happens faster at room temperature, but can be slowed down considerably in refrigerated conditions. Since pears are a climacteric fruit, ripening speeds up when they’re exposed to ethylene, a natural ripening gas. It is actually quite tricky to store pears properly and have them ripen well before selling to consumers. It’s why in the US at least, it often loses the popularity battle from the apple!

Tip: buy slightly unripe pears, this way you can control their ripening. Some people may like slightly unripe pears (myself included) whereas others prefer them very ripe and juicy. If you want to speed up ripening, place them next to bananas, they produce a lot of ethylene which helps ripen the pears.

Want to learn more about pears? This book might be right up your alley (affiliate link)

The texture of pears

Pears and apples may seen like quite similar fruits. Not only can they be shaped similarly (some pears truly just look like apples), they also grow in similar moderate climates and both have a decently mild taste and flavor. However, pears have quite a different texture than their popular colleagues. They’re a little firmer and when you cook or bake with them they fall apart less easily.

Air content

This can mostly be explained by comparing the texture and structure of pears and apples. A first major difference is the air content. Apples tend to contain about 25% of air (the exact amount differs per variety). Pears on the other hand, only contain a few percent of air. This is a big difference! Air is released when the cells of the fruit break down. As a result, apples might lose about 25% of their volume when cooked, whereas pears will more or less maintain their volume.

Cell wall composition

Another important difference is the composition of their cell walls. Apples tend to contain a lot of pectins in their cell walls. These pectins contribute to their smoothness (just as they do for pumpkins). Pears on the other hand don’t have as many of these pectins.

top view of pear cake
Pear cakes with cooked pear on top (see recipe below)

What happens during cooking & baking

So texture is an important property of pears. It’s important for pears that are eaten just so, fresh, but even more so when you’re cooking and baking with pears. You’ll want to make sure that the pear disintegrates the right amount for your type of preparation method.

Loss of turgor

Remember turgor? Cells in plants, which includes fruits and vegetables!, have a special structure that ensures they are plumb and firm when fresh and moist, called turgor. When cells are in turgor, they are plump, swollen full with water. Once water starts leaving the plant (or fruit in this case) the pressure is gone and the fruit becomes softer (it’s why salad leaves wilt and pear will wrinkle over time). Compare it to a balloon, full of air it’s firm, however, when most of that air leaves the balloon it becomes soft and wrinkly.

A fresh pear’s cells will be in turgor. However, by heating the pear, cells walls are broken down and water can escape. As a result, the pear (pieces) will become softer.

Breaking down molecules

This loss of turgor is caused by large (mostly polysaccharides, such as pectins) molecules being broken down. These large molecules provide structure and strength. However, once they break down, the whole pear will soften and open up to letter water out.

Color changes

When boiling pears in water, some pears may turn from a beige to a light pink color. This color transformation is due to the earlier mentioned polyphenols. Aside from producing astringency, the procyanidins can react into an anthocyanin-like molecule. Anthocyanins are molecules with a red/pink/purple hue, causing the pear to change color. (Red cabbage also contains a lot of anthocyanins, just one of many red natural colors in food.)

conference pears
Conference pears are great to be eaten just so.

Pear varieties

Even though you might only find two or three pear varieties in your local store, there are actually thousands of pear varieties. Which ones you’ll find at your store depends on the varieties that grow well in your region. For instance, in the Netherlands, we’d find ample Conference pears, whereas these aren’t common at all in the US. Asia again has slightly other common varieties.

Some pears are good to be eaten raw, you might find them being called ‘dessert pears’. Others are best eaten cooked, or they’d be too hard and dry. Yet again other varieties are mostly used for being made into drinks (e.g. perry, the pear variety of apple cider).

Taste & astringency

Which application suits a pear best, depends on various factors. First of all their taste, some pears are sweeter and more flavorful than others, making them more appealing to eat raw. When transforming a pear into perry, as is the case for apple cider, you’ll want some astringency. This comes from the polyphenols in the pears, mostly procyanidins.

Textural varietions

Secondly, their texture and cell wall composition are important. Pears that contain more pectins for instance tend to be better suited for use in butters (or jams) since they give a creamier consistency. When making poached pears, on the other hand, you mostly want to ensure that the pear keeps its shape and doesn’t fall apart. As such, it will need enough cellulose and non-degraded pectin in its structure to hold up after being heated for an extended period of time!

Unfortunately, there’s not a lot of data available on the composition of different pear varieties. As such, instead of focusing on their composition, it is best to follow recommendations in recipes and with the produce as to what they should be used for.

cardamon pear cake with two slices

Cardamon Pear Cake

Yield: 1 cake, 10 portions
Prep Time: 30 minutes
Cook Time: 40 minutes
Total Time: 1 hour 10 minutes

A juicy, caramelized pear cake, based on the Cardamon Pear Cake by Chetna Makan in the Cardamon Trail.

The pears get a good chance to soften by being pre-cooked and by being at the bottom of the cake.

Ingredients

Pear caramel

  • 25g butter
  • 50g brown sugar
  • 35ml water
  • 1/2 tsp cardamom powder
  • 2 pears (cored and cut into pieces)

Cake batter

  • 100g granulated sugar
  • 150g butter (or a mix of margarine and butter, almost any ratio works)
  • 1 egg
  • 1,5 tbsp corn starch
  • 50g flour (all-purpose or cake)
  • 50g buckwheat (can be replaced by wheat flour, but adds some taste)
  • 35g almond meal
  • 1,5 tsp baking powder
  • 1 tbsp (15 ml) orange liquor (e.g. Cointreau) - optional, can be left out
  • 1/2 tsp cardamom powder
  • 35ml water

Instructions

Pear Caramel Layer

  1. Add all ingredients for the caramel in a small pan and gently bring to a boil. Keep on a low simmer for 10-15 minutes to dissolve all the sugars and soften the pears. If your pears are very hard and unripe it's best to simmer a little longer whereas if you have very ripe pears, only simmer until the sugar has all dissolved to prevent the pears from falling apart.
  2. Leave to cool down slightly.

Cake

  1. Mix the sugar, butter, and egg to ensure the butter is spread throughout evenly.
  2. Add the remaining ingredients and combine until mixed homogeneously. You could use the paddle attachment on a stand mixer or just mix by hand.
  3. If the cake batter is very thick, add a little (e.g. a tbsp, 15 ml) extra water.

Assembly

  1. Prepare a cake pan (we used a rectangular pan, 15 x 23 cm) by coating the bottom and sides with fat, either using a spray or some margarine/butter. Do not use a springform, the caramel will seep out at the bottom!
  2. Pour the pear + sugar mixture into the bottom of the pan.
  3. Spread the cake batter on top.
  4. Bake in a pre-heated oven at 180C (355F) for 40 minutes until a toothpick comes out clean. If you use a smaller pan the cake will need a little longer since it'll be a thicker layer. The reverse is true if you're using a larger pan, then you'll have to shorten the baking time.
  5. Leave to cool down slightly and ensure the sides are loose. Place a plate on top of the pan and turn the cake over onto the plate. Enjoy!

Sources

Marwa Brahem, Severin Eder, Catherine Renard, Michele Loonis, Carine Le Bourvellec. Effect of
maturity on the phenolic compositions of pear juice and cell wall effects on procyanidins transfer.
LWT – Food Science and Technology, Elsevier, 2017, 85, pp.380-384. link

Harold McGee, On Food & Cooking, 2004, Scribner, p.356

Joan Morgan, The Book of Pears: The Definitive History and Guide to Over 500 Varieties, 2015, Chelsea Green Publishing, link

Thyran Phaneuf, The Push to Make Pears the New Apples, 2016, link

Devin Powell, Fruit ‘lungs’ explain why pears rot faster, 15 July 2008, New Scientist, link

Catherine MGC Renard, Effects of conventional boiling on the polyphenols and cell walls of pears, J Sci Food Agric 85:310 – 318 (2005), link

Pieter Verboven, Greet Kerckhofs, Hibru Kelemu Mebatsion, Quang Tri Ho, Kristiaan Temst, Martine Wevers, Peter Cloetens, Bart M. Nicolaï, Three-Dimensional Gas Exchange Pathways in Pome Fruit Characterized by Synchrotron X-Ray Computed Tomography, Plant Physiology, Volume 147, Issue 2, June 2008, Pages 518–527, https://doi.org/10.1104/pp.108.118935 (the photos are amazing!)

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6 Comments

  1. I love this post, thank you for all the links and for the science-based explanations. For your pie recipe, why do you recommend pealing the pears? Is it a texture thing? Would peeling them sacrifice some of the flavor?
    Also wondering if you know of specific varieties of baking pears, had never heard of them.

    • Hi Andrea,

      Peeling the pears is more for texture than flavor. Some pears have quite thick skins that don’t really soften that well in the pie, you’d want to take that away. Also, since we’re using large pieces of pear the skin might get in the way of cutting etc. Although if you prefer to keep the peel on, you can definitely do so!
      There aren’t necessarily specific types of baking pears, but some are more suited than others. A very soft ripe conference pear might be too soft for your taste, it’s nice if there’s a little bite left over. Some pears disintegrate a very quickly after cooking (e.g. the Bartlett pear) so are great for a puree, less so for a pie.

      Hope that helps!

  2. Does this answer the actual question? Which are better ripe, over ripe or under ripe? Or how to ripen pears faster?

    And baking time for each would be helpful.

    Sorry if I missed something but didn’t find this helpful at all to the initial question.

    • Hi Kat,

      You’re absolutely right. We’ve just corrected the title and given the post a needed update. Since there are a lot of pear varieties (thousands) it’ll be too challenging to give a baking time for each. The baking time will also depend on your application (e.g. in the cake recipe we added at the bottom, the pears cook for 10-15 minutes, then bake another 40 minutes in the cake). Poaching pears generally take a little longer to soften than those you can eat just so. Also, a ripe pear is done a lot more quickly than one that’s still a little firm, add a few minutes baking time to a slightly unripe one.

      I would not recommend using overripe pears for any application where you still want a little bit of bite of the pear (e.g. poaching, baking, or even in a pie) since it will easily disintegrate completely. Overripe pears are not a problem for a jam or saucy application though since it has to break down fully anyway! Otherwise you can use slightly underripe and ripe pears for most applications, it’s a matter of taste as well (I prefer slightly underripe pears over ripe ones for instance).

      Lastly, you can speed up ripening of the pears by storing them outside of your fridge and make it go even faster by placing them close to ethylene producing bananas.

      Hope that helps and thanks for the feedback :-)!

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