The Science of Wood and my Dad.

A question many weekend pit warriors may never consider when it comes to wood is: "How long can it last without being used - being exposed to outdoor elements over a prolonged time, will it still be safe for meat since toxins are released in smoke?" This question may never cross the mind of Pitmasters from barbecue joints because they are constantly replenishing their supply based on demand. For your holiday only cooks, this is a different situation.

I found myself pondering this while smoking ribs on a balmy 90* Father's Day with what turned out to be about five year old (at best) post oak. A smoky yellowish hue was billowing out of the stack which caused personal concern. Would today be my last to eat ribs? Or would I turn into a flesh eating zombie - on Father's Day nonetheless?

I bought my Dad a smoker for Christmas in 2006, and it may sit on or around the number of times used at 20. So as you can imagine the wood has been stacked outside for a long, long time. Possible leftovers from Noah's Ark with exposure to rain, snow, hail, insects, snakes, and possible fungus from the little droppings of rodents seeking shelter under the aluminum boat which covers the woodpile. Geez, America has elected the same president twice in this time frame.

To understand smoke, I believe it's important to know the cause of it. The science of wood.

 The components.

I'm no wood-obsessed Ron Swanson from NBC's Parks and Recreation but we all know wood is imperative to the flavor of meat, color of the smoke ring, and the composition of bark. Air-dried wood is used for one distinct reason. Fresh cut wood contains on average of 50% water, therefore utilizing more energy when burning that can produce steam in lieu of the pronounced smoke we're accustomed to seeing.

All wood is primarily composed from cellulose, hemi-cellulose, and lignin. Along with soil and climate, minerals such as oxygen, nitrogen, hydrogen, carbon, and potassium are all factors of wood which impact the flavor and fragrance of the wood type being used. For fresh cut wood, recommendations of allowing dry time range upward to 12 months with 6 months being on the lower end. We can pretty much assume my Dad's five year old oak was moisture free.

Detectors can be used to gauge the amount of moisture still being held within. A quick note is that much depends on your region's Equilibrium Moisture Content (EMC). You can find more information on EMC provided by this link from the USDA/Forest Service. Various methods for drying and storage can be found with basic research as well.

 Pyrolysis

My Dad is a former teacher of all things science who could rival Bill Nye with an uncanny ability at lulling students and sometimes himself to sleep...while sitting at his own desk. He would be amused to know I've invested so much time learning all this high school chemistry stuff I swore I'd never use again. Well here it goes.

When combustion or Pyrolysis occurs, a solid is turned into a gas product with the secondary effect being the production of light and heat. There are three stages of combustion with three basics of said combustion that will be covered in short.

Let's start with the three basics being time, temperature and turbulence. Adequate time is needed with the right conditions for the completion of combustion. Temperature is needed for the fuel gas mixture to properly ignite. Finally the mixture of combustible gases with oxygen is the result of turbulence.

First stage is when the water within the wood begins to boil from slightly over 200* of heat. Combustion cannot occur until all moisture is depleted. When the heat rises, combustible gases such as carbon dioxide, carbon monoxide and acids located in the oily liquid preservative known as creosote are formed. These gases can burn and enable heat. 

Creosote is a playmaker in the color of smoke and flavor of food while still acting as a preservative. Oversmoking can cause a bitter aftertaste on the food but methods can be used to control the creosote amount.

The second stage of combustion is when heat begins to reach 500* after the moisture has evaporated. This is basically the burning gas fuels which in turn creates the fire's flames. The wood is now ready to burn.

The final stage occurs when the wood is burned down to ash and the remaining carbon chains we know as charcoal. Charcoal is what burns long, slow and provides a low heat rate with additional energy being discharged. More wood will be added to maintain the familiar temperature of 225* which is common to pitmasters who smoke meat low and slow with their average time amount varying from 12-18 hours.  

Death by wood...smoke?

With a brief and boring summary of science above, we now take a look at carcinogens which are substances that are productive in the cause of cancer. If the carcinogens from tobacco don't kill you, the carcinogens from wood can.

Beside the minerals listed above, wood smoke also contains formaldehyde, sulfur dioxide and other nuisance gases such as nitrogen oxides. Pretty much you're one step ahead of the funeral director by embalming yourself before death.

Every single negative health symptom that a cigarette can cause mirrors that from wood smoke. Because of the particles being so miniscule, they aren't as easily filtered out and can make their home deep within your lungs-staying for months. Unlike cigarette smoke, I don't know of any studies or examples of pitmasters dying at either a young age or older age from cancer. Any information provided would be welcomed.

Back to the old age question.

The only sure advice I found when it comes to wood that has been exposed to outdoor elements is to not use wood infected by fungus or covered with mold. No real evidence was found regarding age versus use. For obvious reasons, visuals should be performed before using said wood and when in doubt, do without. 

As far as the smoke coloring, white smoke is the evaporation of water, blue smoke being the evaporation of compounds, and finally the mysterious and in my book, deadly yellow smoke. No clue. It only hovered a few seconds before dispersing into the stale June air and I don't think Dad would purposely try to kill me for not buying a Father's Day card..right? A good measure for smoke is "thick and white, it ain't right. Clear and blue, it's time to Cue".

Between hickory, pecan, oak or mesquite, there's no right or wrong, it's all self-preference. Learn the variations of taste from each type then mix and match while enjoying excessive amounts of meat. I encourage you do research first because wood like pine, redwood and cedar, among many others are suitable for firepits but because of their toxins, are not suitable for smoking food. Also wood which has been stored upon a pallet is not suitable for usage.

By the way, I have yet to crave human flesh and the oak smoked ribs glazed with pepper, ginger and lemon didn't turn out too bad either. We'll just say the oak was "well seasoned," much like my Dad who also happens to have his degree in Agriculture. Guess I am learning something from him after all these years. Happy Father's Day Dad!