Vegetables in baking – Part two: rise and shine

Vegetables in baking – Part two: rise and shine

Last week’s blog post sparked a lot of discussion and debate on the topic of vegetables in (sweet) baking. It seems that everybody has an opinion, some are surprised with the idea, some are keen to try it and many already have and offered some great recipes.  I have really enjoyed baking with various vegetables myself… and seeing the response of my taste testers, but more of that next week…. this week I promised to discuss how vegetables contribute more than just sweetness to the baking.

What else is there?

 Last week I mentioned that vegetables contain starch.  Wheat flour typically used in baking contains up to 75% starch.  Many vegetables such as potatoes, peas, corn and squash have a high starch content also.   It is a grainy substance contained within the plant cells.
So what does starch contribute to baking ?
Potato starch granules in potato cells; Image credit: Dr. Philippa Uwins via Wiki Media Commons
Potato starch granules in potato cells; Image credit: Dr. Philippa Uwins via Wiki Media Commons


Starch is referred to as a complex carbohydrate.  The carbohydrate bit means it is made up of carbon, hydrogen and oxygen. The complex part means that the structure of starch is a long chain of these carbohydrates  molecules all linked together in a chain.  The carbohydrate is starch is the sugar glucose and starch is composed of a chain of hundreds of glucose molecules.

Starch is typically tasteless and odourless, its contribution in baking is a structural rather than flavoursome one.  In the presence of heat and moisture starch granules will begin to swell and thicken.  These swollen starch complexes form a scaffolding like network within the mix.  When gluten is present it breaks down with heat and the starch absorbs the water it releases making the gluten dry and rigid, strengthening the structure even further.  This starch-gluten structure gives baking its texture and rigidity and allows it to keep its shape once out of the oven.

When vegetables are used in baking the amount of flour required is reduced.  This substitution of a natural starch in place of a refined one not only makes for a lighter, less stodgy cake, it also improves the nutritional content.  Vegetables are packed full of vitamins, minerals and fibre.  These all contribute to the positive health of our skin, hair, digestive system, mood, cholesterol levels and brain power.


What about a bit of water?

 Vegetables also have a high water content which can contribute to the moistness of the cake.  The baking process allows the water to be contained within the cake as well as helping to retain the vitamins and minerals.  Vegetables with a high water content include courgettes, spinach, peppers, tomatoes, peas and aubergines.  This added moisture also keeps the cake fresher for longer, meaning it can be enjoyed over several days without drying out …. that’s if it lasts that long of course.
Tomatoes are made up of 94% water
Tomatoes are made up of 94% water
Adding vegetables to baking changes the texture of the final product.  As I mentioned last week, vegetables contain fairly high levels of  cellulose, a fibre.  In fact cellulose makes up about one third of all vegetables. This cellulose serves a structural role in the plant cells, along with smaller polysaccharides called hemicellulose.  The presence of both of these greatly changes the texture of the cake.  The cellulose is broken down, in part, during the baking process and this also contributes to the structure (rising) of the cake. However, cellulose still maintains a crystalline structure at the high temperatures typical of baking, and these granules directly contribute to the texture of the cake. Studies have shown that smaller granules of cellulose can yield more favourable rising of bread and other baking allowing for a lighter consistency.
Beetroot Chocolate cake; Image Credit: Dee Sewell of Greenside Up
Beetroot Chocolate cake; Image Credit: Dee Sewell of Greenside Up

gives lovely texture to Dee’s Chocolate cake!


The final word

 So there you have it… not only do vegetables contribute a lovely sweetness to baking but they play a major part in the structure, moisture and texture of the cake.  Surely you must be convinced by now? If not make sure to check back next week for the final part of this blog series when I will be sharing some recipes I have tested and the response they have received.

Tune in next week for Part 3 of the series where I will be sharing lots of recipes and letting you know what people thought.

In the mean time… if you have any comments, tips or experience to share please leave a comment below; I always love to hear from you and will be sure to reply!


Further reading:

Starch in baking

Vegetables in baking – Part one: keeping it sweet

Vegetables in baking – Part one: keeping it sweet

Now that I have entered the world of blogging I enjoy reading other blogs as much as I do writing and researching this one.  I have some favourites that I check in to regularly as a little treat; chief among them is the Greenside Up blog!  Written by the lovely Dee Sewell, this blog brings together garden, community and kitchen, always with a refreshing, informative and jovial note!  Last week was no exception as Dee shared a recipe for Beetroot Chocolate cake. The post not only extended my baking “to do list” but also posed the question…

“Why do vegetable work so well in baking?”


The concept is fairly new to most of us (although we are all familiar with the carrot cake) but is growing in popularity.  With good reason too, it seems.  Tempted, or completely put off by the idea?… I have prepared a short series of blogs to explain a little of the science behind the concept and hopefully to convince you to give it a go!

In this first blog I will look at the sugar content of vegetables and how it contributes to the flavours in the baking.

Firstly, what defines a vegetable?

photo credit: Marj Joly via photopin cc
photo credit: Marj Joly via photopin cc

We can be a little more specific when defining a fruit as its botanical definition is the ovary of the flowering part of the plant; to put this more simply it is any fleshy material covering the seed, or seeds, of a plant.  In general people tend to define a vegetable as a plant used in savory meals and a fruit as a sweet option.This is a tricky one as there is no real scientific definition of a vegetable.  Although there are some generally held guidelines these too vary depending on the classification, criteria used and even the Country you live in. The most common definition of a vegetable is a plant grown for culinary use.

So far, so good, right?  However you don’t have to look too long to find that the lines are very blurred …. for example, in the botanical sense courgettes, tomatoes, pumpkins, squashes and avocados are actually fruit.  Then there is the question of whether mushrooms are vegetables (technically speaking they are not plants but fungi); and what about potatoes? Due to their high starch (carbohydrate) content they are grouped with rice, bread and pasta and are not included as one of our “five a day”.

So the truth of the matter is I cannot actually define a vegetable for you.  All I can say is that, for the purpose of this blog, I am going to lump all these in together as vegetables…. potato, tomato, courgette, even the mushroom (although as a scientist that one grates on me a little)!


Why use vegetables in (sweet) baking?

We all enjoy a nice baked cake now and again and naturally associate the sweetness of fruit with the sweet treat.  No one needs to be persuaded of the virtues of a lovely homemade apple tart!  The key to adding fruit is, primarily, to exploit and enjoy the sugar contained within.  When we think of vegetables we tend to think of a more savory dish, however vegetables do contain sugars as well as fruit, and some in quite significant amounts.  Some of the sweetest vegetables include carrots, beets, peppers, potatoes, peas and corn.  Just to give you an idea….carrots contain approximately 4 grams (g) of sugar per 100 g, while beetroot contains up to 8 g  per 100 g.  Compare this to an apple that comes in about 10 g sugar per 100 g or a strawberry, about 4.5 g per 100 g.  We begin to understand why Dee’s Beetroot Chocolate Cake was so well received by her family!

eetroot Chocolate Cake; Image credit: Greenside Up
Beetroot Chocolate Cake; Image credit: Greenside Up

What sugars do we find in vegetables?

Now we begin to realise the extent of sugars present in many vegetables, but what kind of sugars are they?


photo credit: howzey via photopin cc
photo credit: howzey via photopin cc
  • Another sugar found naturally in vegetables is Sucrose, what we know as common table salt.  Sucrose is made up of the two sugars glucose and fructose.  Most plants make sugar through the process of photosynthesis.  Vegetables make a simple sugar called glucose in this manner.  Glucose is a single sugar molecule that is the ultimate energy fuel for our brain and body.
  • Long chains of glucose form the polysaccharide known as starch.  The longer a vegetable is left on the plant the more likely it is to convert its glucose into starch for storage purposes.  We are able to consume this starch and break it back down into its glucose molecules.
  • Finally, vegetables also contain sugar in the form of fibre, known as cellulose.  We do not metabolise cellulose very well and do not absorb the component sugars into our bodies.  Fibre is a necessary part of our diet though and helps us to maintain a healthy digestive system and a balance of good bacteria within our intestine.


The Maillard reaction

So why do we consider vegetables a more savory dish if they are so full of sugar?  The answer lies in the way we cook them.  Firstly we need to understand a little of the science behind the process.

I have talked about the Maillard reaction in a previous blog, but feel it needs another mention here as it is primary to the discussion of baking, vegetables and sugar!  The Maillard reaction was developed in 1912 and is named after the French Scientist who first proposed it!  Basically it says that when you mix sugar and amino acids (protein) at high temperatures they react to form a variety of different flavours and aromas.

When we add vegetables to our baking the high temperatures of the oven allow the aldehyde group of the simple sugars found in the vegetables to react with the amino (nitrogen) group of the proteins present in the mix to create a variety of pleasant tasting compounds.

When we boil or steam vegetables the heat and moisture do not lend themselves to the browning/sweetening reaction described by Maillard, therefore they have a much more savory taste.  If you need a little convincing just try a little experiment of your own…. prepare a vegetable such as carrot, beet, squash or pepper in two ways… boil one lot and roast the other.  A quick taste test should convince you what Maillard was talking about, even if the Science is a little baffling, even to the Scientists!

Tune in next week when I will discuss how vegetables contribute to the texture of baking, while Part 3 of the series will be the “proof in the pudding” blog with lots of tasty recipes to try.

In the mean time… if you have any comments, tips or experience to share please leave a comment below; I always love to hear from you and will be sure to reply!