Pique the Geek 20101219: The Science behind Christmas Goodies

Republished from the Pique the Geek archives by Translator, aka Dr. David W. Smith

Doc passed away earlier this year. He is missed.

This is the time of the year that I get creative in the kitchen, and almost all of what I prepare is given away to friends and family.  I had hoped to be ready to ship tomorrow, but I got behind and will have to ship Tuesday.  Perhaps too late for Christmas, but certainly not for the rest of the holiday season.

I vary my menu year to year, but a couple of things are standard.  One is Lizzies, a sort of fruit cookie that is reminiscent of fruit cake, except Lizzies are good.  Another is chocolate fudge, with black walnuts.  Both of these were always around during my childhood, because my mum loved everything about Christmas and was an excellent cook.

I have a couple of links for past Christmas goodie posts, and actually the second link is contained in the first one.  These are pretty much recipe based, with a little science here and there.  Except for two new products, you can go there to get the recipes.  We shall concentrate on the science this evening.  http://www.dailykos.com/story/2009/1… is the link, and look for the other one in it.

This year I prepared one brand new treat, and make some more of another that I just created last year.  The first one is Butter Toffee with Hickory Nuts.  Almonds are traditional for butter toffee, but I had an extremely good crop of hickory nuts this year so I decided to try them in toffee.  Here is the recipe:

1 cup (2 regular sticks) butter.  Please do not attempt this with margarine.

1 1/3 cup granulated sugar

1 tablespoon light corn syrup

3 tablespoons water

3/4 cup coarsely chopped hickory nuts, roasted.

1/2 cup finely chopped hickory nuts, roasted

To roast the nuts, put them in a pan with a lip in a 375 degree oven, only one layer thick.  Stir every couple of minutes until aroma is developed.  It took about 12 minutes for the coarse ones and about nine for the fine ones.  You can do it in a skillet on the stove top, but you have to be really careful not to scorch them.

Dump everything but the nuts into two quart, heavy saucepan and turn up the heat.  Use a candy thermometer to determine progress.  This is almost essential, especially with candies like toffee that brown.  Bring to the boil and watch the temperature, and stir with a wooden spoon now and then.

In the meantime, put a piece of waxed paper in a 13 x 9 inch pan, and spray it with cooking spray.  Sprinkle half of the finely chopped nuts on the waxed paper.  Watch the thermometer and reduce the heat to about 75 or 80 per cent and stir more often when the temperature hits about 280 degrees.  Be extremely careful with candy at these temperatures!  If you get it on you, it burns extremely badly, and can damage your eyes if splashed in them.  Eye protection is not a bad idea.

Here is what it looks like just at the boil.


At about 255 degrees, you will notice that the mixture begins to darken.  This is Maillard browning (named after the French chemist who described it in the early 1900s).  Maillard browning occurs when carbohydrates and proteins are heated together.  These reactions provide colors and flavors quite different from anything else (the crust on bread is another example) and are different than carmalization reactions that occur in sugar solutions alone.  Here is how it looks at that temperature.


In this instance, the protein comes for the little bit of milk proteins in the butter.  Butter is mostly butterfat and water, but there are enough milk proteins to produce Maillard products at a fairly high temperature.

At 290 degrees the browning gets much more noticeable, and the aroma changes.  This is due to carmalization, and occurs at the higher temperature.  Keep on stirring, but turn down the heat to only about 50%.  It turns out that carmalization is exoergic (energy releasing), so the material itself is heating up some.  At precisely 300 degrees (the hard crack), snatch the pan from the fire and stir in the coarse nuts.  Pour immediately into the 13 x 9 pan, working quickly to get an even thickness.  Sprinkle the other half of the fine nuts on top whilst still hot.  Let set until cool, and break up into manageable sized pieces.  Store in an airtight container to keep it from picking up water and going sticky.  I was working too fast to grab the camera at 290 degrees, but here is the finished product.


Toffee is a sugar based candy that is amorphous.  That is, it is cooled so quickly that the sugar molecules do not have time to align into regular crystals.  By the way, the little bit of corn syrup is added to retard crystallization even more, so that what is essentially a glass is produced.  The fat and protein in the butter prevent it from being clear, and further interfere with crystallization.  Lollipops are also amorphous, but use only sugar, corn syrup, and water, so they are transparent.

In contrast to toffee, fudge is a crystalline candy.  The first link explains why fudge is often grainy and how to prevent it.  I will not go into that part of the science behind fudge since you can read it there.  If you look at fudge before you add the chocolate, you will see that it is almost as dark at only 236 degrees (the soft ball stage) as the toffee is at 300 degrees.  The reason is that because of the much larger amount of milk proteins because of the evaporated milk (I use a standard can per batch) form more Maillard reaction products than butter alone.

The second recipe that I have not previously reported is White Chocolate Chip/Black Walnut Tollhouse cookies.  These use the standard recipe on the back of any Nestle toll house morsel pack, except obviously white chips are substituted for the dark ones, and black walnuts for the pecans or (UGH!) Persian (English) walnuts.  I invented this last year (I have never seen a recipe of this description), and just finished a batch before I sat down to write this.

Black walnuts are marvelous, and EXPENSIVE, if you can find them.  I saw some at Wal-Mart last week, but I always forage my own.  This was not a good year for black walnuts.  Although there were lots on the ground, after cleaning and curing (I wrote about this a couple of years ago), only about one in 12 was good, and normally one is 12 is bad.  This year they were dried out for some reason.  Thus, I have only a very limited supply this year.  No black walnut cream cheese bread this year, since I have almost exhausted by supply with the fudge and the cookies.

The reason that I used white chocolate was to employ a material that would bring some flavor with it but not overwhelm the black walnuts.  I have made them with semi-sweet bits before, but these are much better.  It was worth the full cup of nuts for these marvelous cookies.

The science behind cooking these cookies is interesting.  The recipe directs you to sift flour, baking soda, and salt together and set aside.  Then you soften butter (since I keep my house at 58 degrees, I had to pop the mixing bowl with the butter in it into the oven for a couple of minutes), then cream in the sugar (half and half brown and white), then beat in two eggs.  Then you slowly add the flour mixture to the butter mixture until completely mixed.  Then you add the morsels and nuts, stir them in, and bake at 375 degrees (depending of the size of the cookie, from eight to 11 minutes in my oven).

Let us look at why this recipe works.  First, the flour provides what is essentially the glue to hold the cookie together.  During the mixing with the liquid, gluten is formed and that acts as a binding agent.  But it gets much more complicated!  The salt is mostly a flavor enhancer.  Many people do not realize that adding a little salt to a sweet dish makes it seem sweeter.  The baking soda is to make the cookies rise just a little.

The butter provides the shortening required to keep from having a dry, tough cookie, in addition to the flavor that it contributes.  The sugars are, of course to make them sweet, but they do more.  Sugar and salt both inhibit gluten formation in flour (there is not really enough salt to do much in this recipe).  If the gluten were fully formed, the cookie would be very chewy, like bread, rather than melting.  The recipe balances the gluten formation to make what we recognize as a Toll House cookie.  In addition, brown sugar is slightly acidic because of the molasses on it (most brown sugar now is made by spraying white sugar with molasses), and the acid reacts with the baking soda to produce carbon dioxide, making them rise a bit.  

Because of the large amount of protein in the flour and eggs, and the large amount of sugar, Maillard browning is extreme and fast.  A 375 degree oven is fairly hot, but not extremely so, and the cookies brown very nicely at that temperature.  Another effect is that the nuts toast it that temperature as well, but because of all of the butterfat, most of the aroma is trapped in the cookie.  You can smell them while they are cooking, but the black walnut taste is very distinct in the cooled product.

Here is a tip for taking the cookies out of the pan (it is in the recipe on the Nestle bag, but they do not say why).  After you take the cookie sheet out of the oven, let it stand off the heat for a couple of minutes before you try to take up the cookies.  If you try to take them up too soon, they just break apart because they are so tender when they are hot.  In my 58 degree house, a little over a minute is sufficient.  But if you wait too long, they stick to the pan!  The reason is that the sugar hardens if they stand too long in the pan, so they “lock up” onto it.  Another tip is to use a thin, metal spatula to take them up from the pan.  I did not break a single cookie out of the six dozen that I made.

In the link to fudge making, I mentioned that you have to stir, stir, stir.  It is important to reiterate that.  Remember, above talking about toffee I said to stir now and then until the very end, and the very end is at 300 degrees.  The very end for fudge is only 236 degrees, and if you do not stir constantly as soon at the mix comes to the boil, you will scorch it.  Why is that?  The only protein in toffee is the little bit in the butter, but fudge is rife with it from the evaporated milk.  The very Maillard browning reactions that we desire for flavor and aroma are the enemies here.

I guess that I should describe the Maillard reactions briefly.  When proteins and carbohydrates are heated together, an extremely complex and not fully understood set of reactions occur.  The ones that contribute aroma and flavor have to do with “average sized” molecules reacting together and releasing new, smaller molecules.  Remember, you can not smell molecules that are too big to evaporate.  However, these same reactions also “tack together” left over parts of the average sized molecules to make really big molecules.  These really big molecules tend to coat the bottom of the pan, and thus insulate it from the liquid above.  This causes the bottom of the pan to become very much hotter than the contents, charring the coating if not constantly being stirred off of the bottom.

This is true in general for most materials that can undergo Maillard browning.  For this reason, stews (if made properly, from breaded and seared pieces of meat) tend to stick and burn on the bottom unless cooked gently in a very thick vessel.

Whilst I am thinking of it, I strongly recommend that you use only wooden utensils when making candy in general and fudge in particular.  As a matter of fact, I like wooden utensils in general because they are extremely heat resistant, nontoxic, and do not get hot on the handle.  This very insulation is critical for fudge, because a metal utensil conducts heat rapidly, increasing the risk of forming seed crystals of sugar in the stirred batch.  Plastic ones would not pose that risk, but I in general do not like to put plastics in anything hotter than boiling water, and at 300 degrees, toffee is certainly much hotter.

All plastics decompose when heated strongly enough, and at those extreme temperatures it can be significant.  In addition, many decomposition products are fat soluble, so the buttery goodies that we are making are ideal to trap and retain those products until we eat them.

Well, I guess that this is sensory overload when you were just going to learn a new toffee recipe, so I shall stop now.  By the way, I am new to toffee making, so if anyone has what he or she considers to be an outstanding recipe, I would appreciate you posting it in a comment.

You have done it again!  You have wasted many more perfectly good einsteins of photons reading this syrupy post!  And even though Michele Bachmann realizes that she has no qualification to be on the Intelligence Committee when she reads me say it, I always learn much more than I could possibly hope to teach by writing this series.  Thus, please keep coming with questions, comments, corrections, and other issues.  Remember, no scientific or technological issue is off topic here.

I shall stay around as long as comments warrant tonight, and will return for Review Time tomorrow after Keith’s show.  Friday, Popular Culture will consist of my Christmas address to all.

Warmest regards,


Crossposted at Docudharma.com and at Dailykos.com


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