Formulating chemists are constantly called upon to use their knowledge and creative instincts to conjure up blends of ingredients to develop functional creams, shampoos and so on. This process is analogous to cooking, which obviously also requires chemistry to perfect edible creations. This article is the second in a four-part series that highlights connections between the chemistries of cooking and personal care product development, including the reactions that occur and why, and how to best utilize these reactions for the benefit of novice formulators. The present article considers the science of meat and fish and how it compares with the formulation of personal care products. A previous article focused on dairy products, eggs and milk;1 additional articles will discuss grains and sugar, and flavors and spices of life.
Science of Meat
Fish, beef, poultry and pork can be generally classified as types of meat and grouped together since they all consist of animal-derived body tissue that can be eaten. In general, the unique flavor of a meat is influenced by the animal’s diet, digestion and percentage of fat fiber. For example, beef from grain-fed cows tastes different than beef from grass-fed cows.
Muscles, which consist of bundles of cells or fibers, are filled with filaments that are primarily comprised of two proteins: actin and myosin. These proteins, with the assistance of adenosine triphosphate (ATP), are responsible for the contraction and relaxation of muscles in living meat sources. Once the meat source perishes, blood circulation ceases and the oxygen supply of muscles is exhausted. Without oxygen, ATP cannot be generated; however, metabolism in muscles continues for a short period after death. ATP has been an area of interest in personal care primarily as it relates to the pain response in skin as well as for its potential role in inflammation and rosacea.2, 3
ATP is produced by anaerobic glycolysis in which the sugar glycogen is broken down to produce ATP. This process leads to a buildup of lactic acid in the contracted muscles and causes the state known as rigor mortis; this state is accentuated if the animal dies under stress. When a meat source dies, it takes time before rigor mortis sets in and this time is dependent upon the meat source. The buildup of lactic acid in muscle affects the taste and quality of meat. If the acid content is too high, meat loses its water-binding ability and thus water, making it tougher; if the acid content is too low, meat will become tough and dry.
After a while, rigor mortis ceases and some of the meat source’s digestive proteins, i.e., enzymes, begin to break down, changing tasteless molecules into smaller, tasty flavors. Furthermore, when these molecules are heated to certain temperatures—e.g., browning the meat—they will react with one another, producing a richer meat flavor. Additionally, aging allows available enzymes to continue breaking down muscle cells, resulting in a more tender and flavorful meat, whereas freezing of meat too soon after death forces proteins to bunch, which results in tough meat.
In addition to actin and myosin, other proteins are present in the muscle, two of which are collagen and elastin. Collagen makes up connective tissues such as tendons and ligaments; it is strong and difficult to break down. Thus, the more collagen present in a piece of meat, the tougher it is to cut and to chew. Elastin is also strong insomuch as it can only be broken down physically such as by pounding a cube steak or grinding meat for hamburger. Similarly, in personal care, human hair is made up of a tough outer cuticle (collagen) that can be dissolved in very alkaline or acid mediums to soften hair and improve porosity.
Quality and Texture
Important to the meat quality are traits such as juiciness and tenderness. These features are influenced by the cut of meat, the way in which it is prepared and cooked, and the length of time that it is cooked. Some water present in meat is bound with the proteins, fats and sugars, and some water is unbound. Generally, the longer the meat is cooked, the more liquid it loses and the tougher it becomes. During cooking, as protein bundles shrink and fat melts in the muscle, water molecules are squeezed out and easily evaporated. As temperature increases to above 120°F, protein bundles become shorter, and more and more water is squeezed out. This is why a well-done piece of meat is dry. But as meat is heated, even though water evaporates from the edges, it is also forced toward the center. The center water is easily squeezed out as pressure is applied to the meat with a knife. After cooking, if meat is covered and allowed to stand for 5–10 min, water will redistribute throughout the meat thus minimizing the release of the meat juices from the meat while it is being cut. A comparison in personal care would be the sweating of oils from the wax matrix of lipsticks, which requires the proper balance and compatibility of oil to wax without depressing the wax’s melting point.
The key to controlling the juiciness of a cut of meat is to control the cooking time and temperature. Cuts of meat containing heavily used muscle generally are tougher. In cooked meat, the quality of the flavor and texture directly relate to the ratio of muscle to fat in the meat, as well as the aging and cooking processes.
Cooking of meat results in the unwinding, or denaturing, of tightly wound proteins: as meat heats, bonds break and protein molecules unwind. At the same time, heating of meat results in the shrinking of muscle fiber diameter and length as water is squeezed out and protein molecules recombine, or coagulate. This process is comparable in personal care to the untangling of natural proteins to improve the availability of carboxylic group(s) of amino acid, particularly when conditioning hair. In addition, product formulators may find it necessary to unwind large molecular weight dimethicone and functional siloxanes to improve their compatibility in formulations and spread efficiency onto skin and hair.
Science of Browning
Browning relates to two types of chemical reactions—nonenzymatic and enzymatic. Nonenzymatic reactions include the Maillard reaction, caramelization and pyrolysis.4 Enzymatic reactions include phenolic oxidation, which results in undesirable reactions such as the browning of a cut apple. Louis-Camille Maillard realized that when meat was heated in the presence of sugars, amino acids (proteins) from the meat react with the sugar such that the meat slowly turns brown and a unique aroma is released. An example of this in personal care is the use of dihydroxyacetone or erythulose keto-sugars in self-tanners that react at skin body temperatures with skin proteins to discolor the skin and simulate sunless tanning (see Reaction of DHA/Erythulose in Self-tanners). There are various by-products from the Maillard reaction, including the ringed compounds: furans, pyrones, pyrroles, thiophenes, thiazoles, pyridines and pyrazines.
Caramelization is the reaction of carbohydrates (sugars) in the presence of heat. Depending upon the sugar that is caramelized, more than 100 different by-products can be produced, including reduced carbohydrates, organic acids, volatile molecules and various aldehydes/ketones. Pyrolysis occurs as a result of the total loss of water during cooking, sometimes referred to as scorching, when the molecule’s carbon-carbon bonds are destroyed.
A comparison to pyrolysis that can be made in personal care is when skin has been injured by burning or erythema. The injured skin loses barrier function and eventually cracks due to an imbalance in water regulation. In addition, the glue holding the stratum corneum together is compromised, causing premature desquamation of the dead skin cells and flaking.
During cooking, time and temperature play vital roles in nonenzymatic reactions, which make it difficult to consistently produce the same flavor and appearance in foods. How many times have individuals cooked a steak or sautéed a favorite cut of meat and felt that it tasted better the last time? Or perhaps this time? For expert chefs that are skilled at handling time and temperature, the taste may not be noticeably different from one preparation to another.
In relation, it is important in personal care to ensure that as many variables—e.g., time, temperature, mixing conditions, order of addition, consistency in starting raw materials— as possible are controlled to provide the most reliable reproducibility batch-to-batch.
Additional flavor can be added to meat through searing, marinating and brining. Searing is a method of browning the surface of meat to improve appearance, flavor and texture.5 Meats also can be marinated to add flavor and tenderize them. Marinades usually are comprised of three components: an acid that denatures proteins and opens “tunnels” in the meat structure, an oil, and herbs. It should be noted that marinades do not penetrate to any depth, and penetration depends on the muscle structure. As a result, for denser meat, marinades work best when the meat is cut into smaller pieces so the marinade can penetrate a larger surface area. Also of note is the fact that most marinades contain acids, e.g., vinegar and lemon juice, that act enzymatically to tenderize meat but if left on the surface too long, these marinades can cause the meat to dry out. Marinating and cutting across the grain or muscle of lesser quality cuts of meat results in improved taste and texture. In personal care, marinades are somewhat like permanent waves for hair, which are used to break down the S-S bonds to allow for reformation of the structural orientation.
Rather than an acid/oil/herb solution, brining of meat involves treating it with a saltwater solution. This adds moisture through osmosis. In a saltwater solution, the meat’s cell fluids are less concentrated than those in the brining solution, allowing for osmotic semi-permeation—i.e., water in the meat flows out of the meat cells and the saltwater is thus exchanged back into the cells. Some of the fiber proteins are dissolved by the salt and the meat’s cell fluids become more concentrated, drawing in water.
Consequently, brining adds water and salt to the cells so that when meat is cooked and water is squeezed out, there is still water left in the cells, keeping the meat soft and tender.
Indirectly, the process of brining meat is analogous to personal care in that chemists must adjust salt levels in a shampoo formula to optimize and stabilize its viscosity under various aging conditions; in addition, aging an o/w emulsion is important before testing its viscosity and pH so that the emulsion has had an opportunity to equilibrate and stabilize.
What About Fish?
Basic differences exist between fish and meats such as beef, poultry and pork. In fish, muscle fibers are much shorter and the collagen dissolves easily during cooking. As a result, fish cooks much faster and there is virtually no need to tenderize it. In fact, a challenge in preparing fish is to keep it from falling apart as it cooks because it loses the structure of its stabilizing collagen.
This is not too different from over-exposure of the skin to UV radiation, which, over years, eventually deforms the skin cells and compromises the skin barrier, resulting in drier skin, dermatitis, wrinkling and cancer cell formation. Thus, protecting skin is not that different from controlling the temperature and time while cooking fish.
Fish is easily overcooked since fiber coagulation and collagen softening happen almost simultaneously and at temperatures and times that are lower than those used for other meats.The delicate flavor of cooked fish is produced due to increased enzymatic activity. As enzymes break down, proteins, i.e., savory amino acids, are generated as well as more complex flavorful by-products.
A parallel to cooking meat versus fish can be drawn in personal care in the case of o/w versus w/o emulsions. In the former, emulsion stability and viscosity are more contingent upon the right choice (cut of meat) and concentration of emulsifier (marinade or additional flavor), as well as the timing of homogenization (browning and cooking time) to achieve the right particle size-i.e., a flavorful steak. In the latter, shear minimization (minimizing heat and cooking time) and the rate of addition of the aqueous phase to the oil phase are more critical.
Formulating chemists continue to work through the variability of raw materials, handling and formulating procedures, and best practices to develop processes that are controllable. Cooking is not all that different. Simply because one cut of meat cooked up nicely and tasted good once does not guarantee it will turn out the same way again. There is too much variability in the meat—i.e., the way in which it was raised, sacrificed, aged and stored—and an exact scientific process is not used to control cooking temperature, times, measurements or seasonings.
It is interesting to observe the similarities between cooking and cosmetics formulating, which revolve around chemistry. Add to these similarities the fact that that meat and human skin and hair have similar physiology and one can begin to appreciate how each responds to the environment to which it is subjected.
Most raw materials are derived from vegetables or animals that have undergone some degree of refinement. Since no two raw material manufacturers practice exactly the same processing methodology, one should be cautious to examine whether differences exist from supplier to supplier or from lot to lot from a specific supplier. Hopefully this review of meat, its chemistry and how it responds to cooking will help formulators unravel some of the mysteries in formulating personal care cosmetics.
1. E Abrutyn, Cooking chemistry and the formulator: Egg whites and milk, Cosm & Toil 124(3) 24–27 (Mar 2009)
2. SG Hamilton, J Warburton, A Bhattacharjee, J Ward and SB McMahon, ATP in human skin elicits a dose-related pain response which is potentiated under conditions of hyperalgesia, Brain 123(6) 1238–1246 (Jun 2000)
3. K Yamasaki et al, Increased serine protease activity and cathelicidin promotes skin inflammation in rosacea, Nat Med 13 975–80 (2007)
4. C Scandrett, Maillard reactions 101: Theory, available at: brewery.org/library/Maillard_CS0497.html (Accessed Mar 25, 2009)
5. H McGee, The searing question … searing doesnot seal in juices, in On Food and Cooking (rev.ed), New York: Simon & Schuster (2004) 161