Friday, September 11, 2009

And now...Food Science Fridays

In case you didn’t know, Justin and I are food scientists. We both have Ph.D.s in food science from the University of California, Davis. And we thought you might want to hear a tidbit of food science trivia on Fridays. So, please send us your comments or even potential topics.

Today’s food science Friday fact is about flour. Did you know that there is actually quite a difference between types of flour like bread flour and cake flour? You might use all purpose flour for general cooking but bread flour and cake flour are blended and milled for those specific applications.

Bread flour has higher protein or gluten content for dough development and bread structure. The higher amount of gluten is critical for giving the yeast-raised dough enough strength to maintain its structure and form a loaf of bread. Cake flour is a finely milled, bleached flour that is lower in protein and higher in starch to create cakes that won't collapse with fat and sugar and that result in a lighter crumb and texture.

When companies make products containing flour, food scientists will choose the blend of flour that has the appropriate qualities for that specific application. We have at least three kinds of flour in our house: all-purpose for most things, bread flour for bread and yeast-raised dough recipes and cake flour for special cake recipes. Rule of thumb for home- never substitute cake flour and bread flour for each other!


Unknown said...

I'm so excited that you are doing this. I am equally happy you explained about the flours. I have just started baking my own bread & bought bread flour but wasn't sure if I was being smart or wasting money. Thanks for the reassurance.

Also, when I knead my bread, I usually use all-purpose flour during that process. Is that a good idea or okay or should I be using the bread flour for that too?

One more question, if you don't mind, I made bread last weekend that seemed to (1) cook faster than I thought it should & (2) seem a bit dry afterward. Do you think I over kneaded it? When I was kneading it it seemed to be ready to rise after kneading for about 1/2 the time that the recipe called for. Thanks.

Holly said...

how do they control the amount of protein, gluten, etc. in the flour? are difference wheat species used or is it proportional to the parts of the grain head used?

Marian said...

Great post! I teach Food & Nutrition at the Secondary level... there's another course in our school which is more science-based than mine (mine relates more to psychology etc.), but we touch on the scientific basics too. Am looking forward to your Friday posts!

Can you reccommend any nutritional sites from youtube or elsewhere as well please?

Lauren said...

Thanks, Kris tea, Holly and Marian for the great comments. Justin and I will post our thoughts here tomorrow on all of your questions. We have a lot say!

But off the top of my head, I have to recommend this site on the science of cooking from the Exploratorium:

It's a great mix of science and everyday questions about food- perfect for teachers!

Marc said...

This looks like it could be a great series. When I have a vexing food science question I'll be sure to submit it.

I'm curious about the protein content of flour. Does a certain brand always have the same protein level? Does King Arthur AP always have X% while Gold Medal AP always has Y%? Is there a summary table anywhere?

@kris_tea -- on KCRW's Good Food radio show/podcast, a baking instructor at a culinary school in L.A. talked about the different kinds of flour and said that bread flour is best for dusting surfaces because its lower starch content reduces sticking.

Lauren said...

Hi Kris_Tea!

We’re so glad you liked this post!

To answer your first question, in our opinion it shouldn’t greatly matter if you use all-purpose flour to take up excess moisture and prevent excessive sticking during your kneading process. All-purpose flour is the middle-of-the-road flour that some may use as the standard flour for their bread. You’re well ahead using higher-gluten bread flour for your dough and the All-purpose flour shouldn’t ruin it (however, we saw Marc’s comment and respectfully realize others may have somewhat different thoughts).

Regarding your questions about the proof time (time to rise) and bake time and impact on the taste of the final product . . . as you’ve found bread making is dynamic and your experience and feel will guide you in making tiny adjustments that can make a big impact.

Different flours (or even the same type of flour over time) will vary in its capacity to take up water and the strength of the dough, however, millers take great care to standardize each type of flour to certain specifications . . .more on this later! Also, the rate of yeast fermentation, which makes the bubbles of carbon dioxide that cause the dough to rise, can depend on a number of things: temperature in the room, humidity, viability of the yeast, the type of yeast (rapid rise vs dry active). All of these and more can influence the proof time and rise. Justin’s Grandma, who used to make at least five loaves a week, would often comment on the weather in bread making terms . . . as in how it would impact the her bread. Bakers very much use recipes but also go by the look and touch and feel of the dough throughout the process rather that the recipe alone.

As for the bake time there can be variations here as well--how accurate is the oven temperature, did you use the recommended pan size as the recipe suggested (that happened in my no-knead bread post and it baked much faster), was it overcooked it resulting in a drier crumb? Since you had originally asked the question of if adding dusting flour could hurt your bread, we wonder if maybe using a little less flour during kneading might improve the dry texture. It may help and you will see what happens when you go with what feels like a slightly stickier surface.

Our advice to you is to make it again and along the way, observe the quality of dough and compare it to your first bread. One way to check for the level of kneading is to take a tiny piece of the dough, flatten it and pull it apart slowly. It should start to form a very thin stretchy sheet if it is properly kneaded. If you were kneading the dough in a mixer or a machine it’s more common to over-knead and begin to break down the structure, however this is much harder to do by hand! Also check the expiration on your yeast and the type of yeast you are using. Bread-making is both a science and an art and experience is the best teacher! Happy baking!

More to come on Marc and Holly's questions tomorrow.


Marc said...

Another science question: it seems to be common knowledge that the alcohol in sparkling wine affects us quicker than still wine. Is that true? If it is related to carbonation, then do other sparkling drinks -- like scotch and soda -- have similarly accelerated alcohol delivery? And would a bubbly beer have a similar effect? Or is it all a legend?