A Ministry of Christian Chefs International (CCI)

Monday, July 1, 2013

July 2013

Last month we looked at heat in general and what happens at the molecular level when we use heat to cook. This month we will be looking at low heat and high heat, and why low heat is sometimes the better option.


Although low heat keeps the moisture in foods, as water molecules won't evaporate as quickly from the surface as with high heat, but it doesn't produce as much flavor as high heat.

The Maillard Reaction (named after Loius-Camille Maillard) explains why high heat produces a dark surface with a unique flavor profile.
When we heat sugars, such as glucose and sucrose, they react with amino acids and create new distinct flavor compounds. These compounds, called dicarbonyls, in turn react with more amino acids to form even more compounds, multiplying rapidly on both the surface of the cooking food and in the cooking vessel. Ultimately, very large molecules called melanoidin pigments are formed, which create the deep brown hue.


The final flavor depends on the amino acids present and their ratio, and how they react with the reducing sugars. Different products have different kinds of amino acids, which result in a different flavor profile. For example, if the amino acid has sulfur in it, you get “roasted meat” flavor etc.

Maillard reaction begins when the surface temperature exceeds 300 degrees. Because of conductive heat  (the temperature on the surface rises as the heat makes it way to the interior), by the time a steak reaches an internal temperature of 80 degrees, the surface may already be 300.
Boiled foods do not turn brown, because water boils at 212 degrees.
Significant heat is requires to jump-start the chemical reaction that causes food to brown. Even with dry-heat cooking methods like sautéing and grilling, the surface moisture of food will steam, lowering the temperature and slowing the speed of the reaction. When grilling, remove excess moisture from the meat, so the Maillard reaction can begin instantaneously.


Meat consists of four components


When meat is cooked, the muscle fiber strands begin to shrink, first in diameter (104-145 degrees F), then in length (above 145 degrees F), expelling moisture as they contract. The rate of moisture loss becomes high around 140 degrees, but at this point, the connective tissue begins to tighten as well, squeezing the fibers even more firmly, creating a potentially tough, dry meat - if it wasn't for collagen.

Collagen is the predominant protein found in everything from a cow’s muscle tendons to its hooves. Collagen is composed of three protein chains tightly wound together in a triple-stranded helix and therefore is almost unchewable when raw. Temperatures under 140 degrees do not affect this protein, but after 140 degrees, collage begins to relax, unwinding into individual strands. When held at a temperature above 140 (about 160-180), for an extended period of time, the triple helix of collagen unwinds and forms a gelatin, a single stranded protein able to retain up to 10 times its weight in moisture, which tenderizes meat, and adds a thickness to sauces and braised dishes.

The conversion of collagen into gelatin requires both TEMPERATURE and TIME: the longer the food is held in the ideal temperature (160-180), the more collagen breaks down.
This is why extended cooking destroys lean cuts with little collage (such as tenderloin), because as the muscle fibers contract, they steadily give up their juices and become drier and tougher with time. The final cooking temperature should not be any higher than 130 degrees for beef, and 150 degrees for pork.

Collagen-rich cuts are too tough to eat, when cooked to rare or medium-rare. Extended cooking tenderizes tough cuts with lots of sinuous collagen (like beef brisket), because it lets the abundant collage to transform into gelatin, keeping significantly more moisture inside the meat as the tightening muscle fibers relax a bit, drawing moisture back inside the meat.


Fish and seafood, other than salmon, have very little fat. Their internal temperature is lower than meats (140), which creates the danger of overcooking. Cooking with high heat would result in a dry and tough product, but although cooking in a lower temperature retains more moisture, high heat produces flavor. Because the Maillard reaction doesn’t occur until 300 degrees F, the browning process must be aided. Sugar and butter can aid in the browning process.

Sugar (sucrose, disaccharide) added to the wet surface of the fish that is exposed to the heat of the pan quickly breaks down into glucose and fructose (monosaccharide). Fructose begins to caramelize at around 200 degrees, a temperature the exterior of the fish reaches within a minute or so after being placed on the pan, which gives it a good crust before the fish dries out. 

With fish, you don’t want any carryover cooking. You want to halt the cooking as soon as possible, for fish does not contain any fat, wherefore it dries quickly. Slicing the fish as soon as it is cooked, arrests the carryover cooking.  

So there you have it, the science behind a perfectly cooked meat and fish. Summer is here, so bring out the barbeque, and enjoy!

Susanna Krizo