Texture and Taste1st Installment

Texture and Taste1st Installment

Oil and viscosity

The term 'oil viscosity' relates to the viscous property of oil. Oils of high viscosity enable the creation of an oil film on the surface of metals and allow support of large loads. However a higher viscosity does not necessarily mean better, as too high a viscosity may lead to excessive resistance increasing power loss.
Conversely low viscosity may reduce power loss but increase chances of loss of the oil film. For these reasons, it is important to follow manufacturers recommendations regarding proper viscosity levels.

What is Viscosity?

It may be simple to say that viscosity is a unit which indicates the degree of "stickiness" or viscous ness of a substance. However viscosity is not such a simple matter. For someone who is uninitiated in viscosity, the chameleon-like changes viscosity may undergo make it difficult to grasp its true form.
Then, what is the true form of a substance? A more accurate definition will be offered in a later column but we would like to preface this in this column with a discussion on some related aspects.
The study of the viscoelasticity of substances is referred to as rheology, which is known as a rather formidable field. At the same time, it is somewhat unique in that it has such great impact on and application in our daily lives.
Those who like cars or machines, for example, are probably aware of the effect of machine temperature on changes in the condition of the oil and realize the importance of the viscous ness of the oil. The same can be said in cooking. For tempura and other fried dishes, the condition of the oil is an important factor and this is related to viscosity.
Viscosity also plays a critical role in our bodies and health. Take pulmonary embolisms, the "economy class illness syndrome", for example. Respiratory illnesses are frightening because in the worst cases may lead to death. Such illnesses are often caused by sitting for long periods which causes blood flow to become sluggish. If conditions of dryness and lack of fluid intake are added, the viscosity of the blood flowing in the body tends to rise and high blood viscosity is apt to cause blood clots or embolisms which can block the arteries to the lungs.
The human body is largely composed of water. However the water is not always in its easy flowing state and the simplest way to maintain this state is to keep the body replenished with fluids. From a rheological standpoint this would represent an excellent means of viscosity control.
Rheology also plays a large part in our daily lives - from unraveling the secrets of cooking good rice to developing non-drip bathroom cleaners, for example. In industry of course, the role of rheology is a large one. It is indispensable in raw material and product evaluation, quality control, and in research & development of new materials as well as a useful tool in quantitative applications relating to viscosity and visco-elasticity.

What is "tasty" ? "Taste" from the chemical and physical perspectives.

Shifting the discussion, let us look at the concept of taste, as in "tasty" or "delicious", from the rheological point of view.
There are two basic factors in evaluating taste. One relates to "chemical taste". Various taste sensations relating to preferences such as "liking things spicy hot", "disliking bitter tastes", and including taste judgments such as "this tastes a little strong" and "this sweetness is fine" which are measurable are referred to as "chemical taste".
Chemical taste is determined by the sensors or taste buds on the tongue. However as the number and sensitivity of the taste buds differ with the individual, the degree of sweetness, for example, may differ according to the individual even when tasting something with the same amount of sweetener added. In addition whether the sensation of sweetness, as it stimulates (signals) the taste buds is pleasurable or not is a subjective issue. Thus quite a variance is involved in ascertaining whether something is 'good tasting' or 'bad tasting' from the chemical perspective.
The other taste factor may be referred to as "physical taste". Simply described, this relates to taste texture - such as judging firmness, smoothness to the palate and throat, and so forth.
For example, take a creamy gelato ice cream. Which tastes better - eating it with a spoon or drinking it through a straw as a shake? From the standpoint of chemical taste, they are nearly the same. But we think people who prefer it frozen are in the overwhelming majority. In this manner texture becomes the important factor in judging whether something is tasty compared to judging it on a chemical taste basis.
Imagine gum that is hard (like leather), 'ikura' that is soft with no resilience, fish cakes or tofu that are not firm, or coffee with rough ground residue. Not very appetizing. With solid foods especially, texture is believed to govern taste preference in many cases.
If a foodstuff can be referred to by its viscosity, viscoelasticity, agglutination, "stickiness", or palate sensation, it may be defined by the amount of water or fat it contains which would be a rheological indicator.

Importance of texture

Foods each have a natural firmness and a texture when eaten. Foods such as fruits taste best in their raw state while others such as burdock root need to be heated in order to bring out their delicacy. Cooking implies not only adjustments of taste by the addition of seasonings but also changes in texture.
Cooking is now scientific and no longer are boiling, grilling, steaming, cutting, mashing, stretching and other techniques limited to the skills of the cook. To cope in this age where eating out is now part of the general lifestyle and to be able to create tastes favored by the masses, food substances (types of food additives) which improve texture are being developed and are playing an important role.
The term "food additives" may not have a good connotation and may be a cause of unnecessary concern. However food additives also include substances like starch, for example, which is a good and effective substance for improving texture (although when bringing this forth, a high level of enzyme technology is also involved in the process). The addition of one type of wheat flour starch results in a firm, viscous 'udon' noodle while another type of starch results in a soft, sticky 'udon' noodle. Textu' noodles can be so tailored to customer preferences, that would indeed be an impressive feat of culinary artistry.
Improvements in texture can be applied to chemical taste as well. As chemical taste is detected by stimulus of the tongue's taste bud sensors, by manipulating this sensitivity it is possible to change the way taste is chemically perceived. If viscosity is raised, for example when a broth is thickened to lock in the ingredients of flavor so that they do not reach the taste buds easily, proper seasoning will enable the creation and tailoring of fine dishes. Such control can also extend into 'Yakuzen' cuisine where bitterness and acidity are restrained to moderate levels.
Thus while we may not be aware of it, texture control plays an important and varied role in our daily lives.

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