Chewing is what allows us to enjoy the juiciness and tenderness of meat—though for different periods of time in each case.
LESS THAN A DECADE AGO tenderness was thought to be the most important sign of a good piece of meat. After all, the true gourmet detests tough meat. But how does one tell tenderness and toughness apart? It had been forgotten that meat is not butter and that texture is one of its fundamental qualities. Toughness was confused with a lack of juiciness and the need to chew for a while before swallowing. To elucidate the relationship between the physical structure of meats and their texture, Institut National de la Recherche Agronomique biologists in Clermont-Ferrand analyzed the mastication of samples of meat prepared in various ways.
Studies of the texture of meat have long been hobbled by the mistaken idea that the texture of a food is the same thing as its consistency, which is a microstructural property. Texture has to do instead with the psychological reaction to the physicochemical stimuli aroused by mastication. (For example, water is a liquid, but if you land on it outstretched from a height it can feel as hard as concrete: the texture of water varies depending on whether it can be displaced beneath a falling body, but its consistency is always the same.) Sensory perceptions modulate the motor actions that break up food. Chewing causes the structure of food to be modified, revealing its texture.
Laurence Mioche, Joseph Culioli, Christèle Mathonière, and Eric Dransfield studied the question of texture in the case of meat (in this case beef), searching for similarities between the sensory perceptions aroused by tasting, the mechanical properties of the meat (resistance to compression and cutting), and the electrical activity of the muscles involved in mastication. The beef was prepared in several ways: Some samples were toughened (to a degree that cooking did not subsequently counteract) by immediate cooling after slaughter, and other samples underwent a long aging process at a temperature of 2°C (36°F). Then the different pairs of samples were cooked at 60°C (140°F) and at 80°C (176°F). One piece of each pair was analyzed mechanically, and the other was eaten by trained tasters who judged the elasticity, initial tenderness, overall tenderness, and length of time in the mouth, which is to say the time needed to chew the meat before being able to swallow it. During this exercise the physiologists analyzed the process of mastication by recording the electrical activity of the masseter and temporal muscles.
The Sensation of Toughness
The mechanical measurements corroborated the results of studies that had been conducted for many years at Clermont-Ferrand. Immediate cold storage of food after butchering multiplied by a factor of three or four the resistance to both compression and cutting. Conversely, gradual cooling followed by a prolonged maturation process diminished both types of resistance. Higher cooking temperatures greatly increased the resistance to compression but not to cutting. Finally, differences between the various samples of meat resulted mainly from the action of myofibrillary proteins (responsible for muscle contraction) and the connective tissue, made of collagen, that surrounds the muscle fibers. The physical reactions of the tasters displayed wide variation. The aging period and cooking temperature had perceptible effects on the process of chewing, but differences in preparation had little effect on the electrical activity of the muscles involved.
As they went along the tasters noted their sensations. All of them correctly identified the toughest meats: The type of muscle, the mode of storage, and the cooking temperature affected sensory perception in the same way that they affected mastication. Nonetheless, sensory descriptions did not match the experimenters’ predictions. For example, the perception of elasticity did not imply a corresponding initial impression of tenderness. Juiciness, which tasters associated with an initial degree of tenderness, but not elasticity, was influenced more by cooking temperature than by the type of storage; the loss of juice was not perceived as a loss of juiciness. Today we still do not know exactly what juiciness is. Is it the quantity of water in the meat and in the mouth? The quantity of fat? The quantity of saliva secreted in the course of chewing?
The tasters concluded their work by grouping the meats into five classes of increasing tenderness. The meats they found to be the most tender were those that had been aged the longest. The toughest meats were those that had been refrigerated just after slaughter. Lengthening the aging time had a perceptible effect only in the case of meats cooked at 80°C (176°F). Finally, meats cooked at the lower of the two temperatures were thought to be more tender than those cooked at the higher one. Juiciness was found to depend mainly on cooking temperature and much less on the type of storage or aging or on the type of muscle. Differences were plain after the first few bites.
The Reliability of the Senses
Mechanical measurements, sensory evaluations, and electromyographic measurements all yielded the same results, then, with regard to tenderness: Prolonged chewing is needed to make a judgment. By contrast, juiciness is best assessed after a few bites, which detect the general characteristics of the food, causing subsequent mastication to be adapted accordingly.
The Clermont-Ferrand study provided valuable methodological information as well. It revealed that sensory evaluation is the most effective method for detecting differences between various samples. The human perception of the masticatory sequence from beginning to end does a better job of capturing the sensory properties of the meat than mechanical measurements, and the number of masticatory cycles is a more reliable measure of elasticity, tenderness, and toughness, as it is actually experienced in the mouth, than compression measurements. But the mechanical measurement of relative compression is a better guide to juiciness. Tasters are known to adapt their style of chewing to the properties of a particular food, but at which stage of the chewing process they do this merits further study.