Section i. Human smell and taste
Sensory analysis can generally be divided into two broad categories: analytical sensory analysis and partial sensory analysis。
The analysis of most spices uses analytical sensory analysis, which is more “objective” and sometimes preference-type sensory analysis. The fragrance of the aroma product is a partial sensory analysis, which relies on a combination of mental and physical perceptions, the results of which are influenced by a variety of factors, such as the living environment, the habits of life, the aesthetic outlook and so forth, and often vary from person to person, from time to place。
Preference sensory analysis varies from person to person, from time to time and from place to place, because people have different senses of smell and different preferences, and even if the same person sniffs a sample at different times, the same conclusion is not necessarily drawn. These factors directly affect the evaluation results. This section therefore briefly describes the theory of human smell, so that readers can have a clearer understanding of the findings and “conclusions”。
The sense of smell and taste dominates the work of the fragrance tissue, and errors in the sense of smell and taste will have a significant impact on the results of the fragrance analysis. Therefore, we must understand the physiological characteristics and basic patterns that lead to the misperceptions of smell and taste, in order to minimize the error of smell in the selection of the assessor, the setting of the experimental environment, the design of the experimental programme, and the processing of the results。
The sense of smell is the perception of the smell. The sniffer is located at the top of the nasal cavity in which the sniffer is the sensory sensory of the smell and receives the smelled molecule. Appropriate irritants of smell must be volatile and soluble, otherwise they are not easily irritated and do not cause smell. The irritating aromatic molecules must have the following basic conditions in order to cause a nervous impulse: volatilism, water solubility and lipid solubility; a fragrance atoms or fragrance groups; a molecular profile of 17 to 340; an infrared absorption spectrum of 7,500 to 1400 nm; an absorption spectrum of 1,400 to 3500 nm; and a refraction rate of about 1. 5。
"enter the room of ziraan without hearing its scent" is typical of smell adaptation. Sniffing cells are prone to fatigue, and when a central system, such as a snuff ball, is in a negative state of feedback due to the irritation of the odor, the sense is suppressed and the odor is lost, which is adaptive to the odor. Therefore, the number and duration of evaluations should be kept to a minimum。
The individuals who smell are very different, and those who are acute and slow to smell. Sniffers are not all sensitive and vary according to the smell. The physical condition of a person can have a direct impact on the smell organs. A person who suffers from cold, physical fatigue or malnutrition causes a loss of smell function. There is a lack of smell or allergie among women during menstruation, pregnancy and menopause。
The human sniffing brain (the brain sniffing centre) is smaller, usually a little bit smaller than the small tip of the finger, and the area of smell on the top of the nasal cavity is small, about 5 cm2 (the cat is 21 cm2 and the dog is 169 cm2) plus the human-level sniffing nerve is less than any other mammalian (the signal from the sniffer goes through the ball, the first nerve is far from meeting the need for subsequent transmission), so the human smell is far less sensitive than that of other mammals. The human sense of smell can generally distinguish 1,000 to 4,000 different odours, and specially trained noses can distinguish up to 10,000 different odours。
Sniffing cells are prone to fatigue, because the smell impulse signal is carried out from the first to the second peak, and the nerve takes 1 ms or more to recover from the first to the second peak. If the second irritation interval is greater than the time required for the nerve to recover, it manifests itself as an exciting effect; if the interval is too short, the nerve is still fatigued, which in turn contributes to an absolute non-extension, and any intensity of the stimulus does not react and is reflected in a inhibiting effect. That is the logic of entering the room of zeran for a long time without hearing its scent, and entering the room of the abalone for a long time without smelling its smell. As a result, ordinary people must take a break after they have smelled three samples, otherwise they will have abnormal results and impact assessments。
Training enhances people's sense of smell. A “good nose” should be a high sense of smell sensitivity and a high degree of “resolution” of the various scents. Sniffing sensitivity is congenital, and some people are born to be sensitive to a variety of odors, while each person's snuffiness decreases with age. However, human “resolution” of various odours can be greatly enhanced through training, and the sense of smell sensitivity of most fragrances and critics can only be average, but the “resolution” of odours is largely invisible, as a result of long-term training。
Tasting means that food is an irritation and a feeling of the chemical perception of the oscillating organs in the human mouth。
Several basic tastes of the human being come from the taste buds on our tongues, which have a large amount of sweet buds on the front of the tongue, the tip of the tongue, the first half of which is salty, the second half of which is sour and the close part of the tongue is bitter. In fact, the taste buds on our tongues can sense all sorts of tastes, but they have different sensitivity. The axial neurons, tongue neurons and locomotive neurons break into the brain dry beam core, change the neurons and then pass through the hypothalamus to the odour zone of the island's lid。
Traditionally, there are only four basic tastes: acid, sweetness, bitterness, salty. The smell was later discovered. Until recently, the sixth taste, “fat”, was discovered and introduced. Thus, it can be argued that there are six basic tastes that are currently widely accepted, namely, acid, sweetness, bitterness, salt, freshness, fatty (which has recently been suggested as the seventh taste of starch, which has not been widely accepted), which are the result of direct food stimuli。
Among the six basic tastes, people feel the most salty and bitterest, but in terms of human sensitivity to taste, bitterness is more sensitive and detectable than other tastes。
People living in different regions have different classification of taste:
Japan: acid, sweet, bitter, spicy, salty。
Europe and america: acid, sweet, bitter, spicy, salty, metal smell, calcium (undetermined)。
India: acid, sweet, bitter, spicy, salty, tastey, dim, abnormal。
China: acid, sweet, bitter, spicy, salty, fresh, dark。
There are only six basic odours: acid, sweetness, bitterness, salt, freshness, fatty. They're made of food directly stimulating buds. The acid and salt are received by the ion channel of the sensor, while sweet, bitter, fresh and fat are a g-protein-polymer receptor。
Spicy: a pain caused by food composition irritating oral mucus, nasal mucus, skin and trident nerve. This is the self-protection function of the human body, where spicy foods are excluded as a harmful substance in early childhood, which is the reason why adults throw up and down when they over-eating. To be precise, spicy isn't a taste, it's an irritation, it's a pain, it's a direct irritation of our tongues or the nerves of our skin, just like you feel irritating when you put a slice of chili next to your eye, and when you cut onions, it feels hot, because spicy is an irritation。
Tastes: the food composition stimulates the mouth, so that the protein coagulates as a condensation. Taste is not the basic taste of food, but the result of stimulating the sensory nerve end。
The process of osteoporosis: taste-based irritation of odour senses in the mouth, then transmitted to the heart of the brain through a nervous sensory system that collects and transmits information, and finally produced through the analysis of the integrated nervous central system of the brain. Different odours arise from different odours, and the odours interact with different odours。
Taste transfer: irritation received by two thirds of the oscillator in front of the tongue, transmitted by the drums of the facial nerve; a third of the oscillation of the back of the tongue is transmitted by the nerve of the tongue; a third of the irritation received by the oscillator in the centre of the tongue and in the soft, oscillating, anorexic sensor is transmitted by the loser. The axial neurons, tongue neurons and locomotive neurons break into the brain dry beam core, change the neurons and then pass through the hypothalamus to the odour zone of the island's lid。
Taste buds: taste buds, followed by free nerve endings, have 10,000 taste buds for infants, thousands for adults, decrease in the amount of taste buds with age, and decrease sensitivity to tasteful substances. Taste buds are mostly distributed in breast-shaped sprawls on the surface of the tongue, especially in the mucus of the tongue. Taste buds typically consist of 40 to 150 osteopathic cells, which are replaced every 10 to 14 days, with many osteometric molecules on the surface of the osteopathic cells, and different substances can combine with different osteometric molecules and have different tastes. The tip of the tongue and the edge of the tongue are more sensitive to salt, the front of the tongue is more sensitive to sweetness, the sides of the cheek of the tongue are more sensitive to acid, while the roots of the tongue are more sensitive to bitterness and spicy. The human odour is from a tasteful substance irritation to a taste of 1. 5 to 4. 0 ms, which is faster than vision 13 to 45 ms, hearing 1. 27 to 21. 5 ms, touch 2. 4 to 8. 9 ms。
Threshold: the lowest concentration of the substance necessary to feel the taste of the substance。
Depending on the method of determining the threshold, the threshold may also be divided into:
Absolute threshold: people feel the taste of a substance from nothing to nothing。
Discrepancies threshold: the difference in the amount of irritation in which a person feels a substance with a significant difference in taste。
Final threshold: people feel that the stimulation of a substance does not increase the amount of stimulus as the stimulus increases。
The relationship between substance (structure) and taste: sugar - sweet, acid - acid, salt - salt, bioalkali - bitter。
The water solubility as a substance is necessary to allow for a sense of taste, and substances that are completely insoluble in water are odourless, and substances whose solubility is less than the threshold are odourless. The higher the solubility of water, the faster the sense of taste becomes, the faster it disappears, the greater the solubility of acid, sweet, salty substances, and the more soluble of bitter substances。
Temperature: the temperature generated by the most suitable sense of taste is 10 to 40°c, especially 30°c, which is the most sensitive and which is more or less retarded。
The temperature also has a clear effect on the threshold of the substance:
25°c: 0. 1 per cent sugar, 0. 05 per cent salt, 0. 0125 per cent lemon acid and 0. 001 per cent sulphate。
0°c: 0. 4% sugar, 0. 25% salt, 0. 003% lemon acid and 0. 0003% sulfate。
When two identical or different odour-based substances enter the mouth, they produce a change in both odours, known as odour-based interactions。
A contrast of taste: an appropriate combination of two or more odour-bearing substances can make a certain odour-based substance more visible. Adding 0. 15 per cent of sodium chloride to 10 per cent of sugar cane water solution would make sugar sweeter, adding a certain amount of sodium chloride to acetic acid solution would make sodium chloride more acidic, and adding sodium chloride to the sodium water solution would make fresher。
Complication of taste: when two substances of the same taste enter the mouth, their taste intensity exceeds the sum of the taste intensity used by the two alone, called the synergy of the taste. For example, ammonium licorice itself is 50 times sweeter than sugar, but can be used with sugar at the end 100 times sweeter than sugar。
Taste extinction: a odour-based substance can reduce the intensity of another odour-based substance, known as taste stress. For example, the interaction between sugar cane and sulphate queening。
Tastes change: two odour-bearing substances interact with each other and change their taste. It's sweet when you've just eaten it; it's bitter when you brush your teeth。
Taste fatigue: after a long period of irritation with a odour-based substance, it is felt that irritation or irritation is decreasing。
Taste is a basic biological feeling in humans and animals, which is used to identify the nature of food, regulate appetites and control diets. Taste is not only in the mouth, but also in the gastrointestinal tract. Studies have shown the presence of cells on the mucous membranes of the animal intestinal tracts that express odour receptor and odour-related factors, the regulation of intestinal hormones, such as glp-1 and gip, and the expression of sugar trans-shipments, gslt-1 and glut-2. The stimuli of sweets affect the hormonals and the expression of the vectors, thus affecting the absorption and use of glucose in the organism. The study of intestinal palsy helps to reveal the regulatory mechanisms for intestinal digestive absorption, while providing new entry points for the treatment of diabetes, obesity, metabolic disorders and other dietary-related diseases。
Like tongues, the intestine can “eat” the food we take, sense its bitterness, sweetness, fat and fresh taste, and its signal transfer mechanisms are similar. Once the food enters the intestinal tract, the body is able to control hunger and blood sugar levels with the corresponding hormones. During over-ingestion, the stomach sensor or receptor produces the corresponding signal. The failure of these receptors can play an important role in the occurrence of obesity, diabetes and related metabolic problems. The selective targeting of the aroma receptor on intestinal cells, which causes humans to develop hormonal hormones with abdominal saturation, can simulate post-eating physiological effects, thus creating an already edifice. There is growing evidence that obesity and associated metabolic problems may be prevented and treated in this way. Although not fully understood, its mechanisms may also be related to changes in intestinal hormones. These odor receptors are targeted and do not need to be operated to influence hormone distribution and control food intake. Work is still needed to determine which intestinal receptors can serve as effective drug targets。
