Cooling agent spices are spices with a cooling effect, including natural cooling agent spices and synthetic cooling agent spices. Natural cooling agent spices refer to spices that are taken from nature and maintain the original aroma characteristics of plants. They are usually processed by physical or chemical methods such as crushing, distillation, and extraction. Synthetic cooling agent spices are prepared by chemical synthesis using chemical raw materials. Single fragrance.
1.Menthol
Menthol is the most common natural cooling spice in nature. It has the characteristics of quick cooling sensation and fresh aroma. In addition, green natural products have become more and more popular among people in recent years. Therefore, the demand for menthol in end products has gradually increased. trend. However, menthol also has its own application shortcomings, such as bitterness when used in large amounts, high volatility, and short-lasting cooling sensation. In response to these shortcomings, many application experts have made certain improvements to menthol. For example, in the "menthol-containing flavor preparation" invented by the German Simlei company, sugar alcohol raw materials and sweeteners are used to mask the bitter taste of menthol, including erythritol, xylitol, stevioside and Aspartame et al. In addition, they also add essential oils and spices to the product to reduce the burning sensation caused by menthol in the mouth. Liquid flavoring agents are also used in the "cooling composition" invented by the Swiss company Givaudan to improve the bitterness of menthol. China Tobacco Company has also added sweetener ingredients to menthol cigarettes to mask the bitter taste of menthol. Methods similar to bitter taste masking are also widely used in refreshing beverage products. Currently, commonly used bitter masking agents for menthol include sucralose, neotame, and aspartame.
Because menthol can produce a good cooling effect on the skin, it is also widely used in products in the fields of medicine, daily chemicals and so on. For example, the "Aloe Cooling Gel" produced by Suzhou Shengbai Health Co., Ltd. contains menthol, which can provide cooling and analgesic effects; Runjie Eye Drops also contains a small amount of menthol, which can sterilize and reduce inflammation. and cooling effect. At present, after cooling sensation tests, the results show that using menthol in topical cream products can achieve a faster cooling sensation effect, and the cooling sensation effect of menthol on the skin is significantly longer than that in the mouth.
2. WS series products
Since 1970, Wilkinson Sword Company has conducted extensive research on synthetic cooling agents, during which they developed approximately 1,200 compounds with a cooling sensation, namely the WS series of products. These include WS-23, WS-3, WS-5 and other products that later became commercially successful.
2.1 WS-23 products
The WS-23 product was developed and synthesized by Wilkinson Sword Company in the early 1980s. The company uses diisopropylpropionitrile (DIPPN) as raw material, first hydrolyzes it to generate diisopropylpropionic acid, then adds thionyl chloride to react to generate acid chloride, and finally reacts with methylamine to obtain the target product.
In 2002, the American International Flavors and Fragrances Company (IFF) introduced a new process for preparing WS-23 in a patent. This method also uses diisopropylpropionitrile as raw material, adds excess triacetin, and finally adds dimethyl sulfate. The ester is distilled to obtain the target product with a yield of up to 70%. In addition, Millennium Company has also proposed a new synthesis method, which uses diisopropylpropionitrile, methanol, dimethyl carbonate and other compounds to react under an acidic catalyst, with a yield as high as 90%.
Compared with menthol, the most significant advantage of WS-23 is that it has a long-lasting cooling sensation and no bitter taste in the mouth. However, WS-23 lacks the explosive cooling sensation and special mint aroma of menthol. Even so, WS-23 is still widely used in candies, beverages and other products. In some cooling candy products that require a high cooling sensation, the added amount of WS-23 can be as high as 0.3% to 0.5%, while menthol will produce a bitter feeling when added in an amount greater than 0.08%. In addition, after pulverization, WS-23 can destroy the crystalline form and form finer particles similar to powder, making them easier to add to tablet sugar products. Currently, most of the tablet sugar, ring sugar and other products on the market are Use WS-23 as a cooling agent.
In addition, WS-23 has good solubility in hot water, while most other commercial WS series products are difficult to dissolve in water. After using propylene glycol to dissolve WS-23, it can be directly dissolved in water at room temperature. Therefore, WS-23 is also one of the commonly used refreshing agents in mouthwash and beverages.
2.2 WS-3 products
The traditional synthesis process of cooling agent WS-3 is to use p-phenylammonyl-3-acyl chloride and ethylamine to react directly. However, Millennium Company has proposed a new synthesis route, which is made from p-phenylammonyl-3-carbonitrile. It is made by reacting with triethyl phosphate in the next step catalyzed by polyphosphoric acid, as shown in Figure 1. Among them, the lower the production cost of p-mengyl-3-carbonitrile, the more advantageous the product price will be.
WS-3 is a long-acting cooling agent. The cooling intensity of WS-3 tested by Millennium Company is 1.5 times that of menthol, and the cooling duration is 20 to 30 minutes. The cooling effect is mainly on the throat and also in the mouth. It has a cooling sensation, so WS-3 is often used in throat lozenges. However, it should be noted that WS-3 has the same bitter taste as menthol, and the dosage needs to be optimized during specific use. When the dosage is large, a small amount of sweetener can also be added to mask the bitter taste. In addition, WS-3 is difficult to dissolve in water. If it needs to be used in beverages, mouthwash and other products, it is necessary to dissolve WS-3 in propylene glycol and then add Tween or Span solubilizer before use.
2.3 WS-5 and WS-12 products
The cooling agent WS-5 is also called N-(ethoxycarbonylmethyl)-p-alkane-3-carboxamide, as shown in Figure 1. Its appearance is a white powdery solid, and the cooling sensation is mainly concentrated in the mouth and throat. The intensity is about 3 to 4 times that of menthol, and it is the variety with the highest cooling intensity among the WS series. WS-5 is mainly used in hard candies, lozenges, toothpaste and other products. The black toothpaste currently on the market contains WS-5 ingredients. In addition, when WS-5 is used with mint oil or menthol, it has a cooling effect. The intensity will be significantly improved.
WS-12 is also called N-(4-methoxyphenyl)-p-menthyl-3-carboxamide, as shown in Figure 1. Millennium Company's test results show that WS-12 does not have the bitter taste or burning sensation of menthol. And spicy, it can produce an impactful, refreshing and long-lasting cooling sensation, which acts on the entire oral mucosa and throat. In addition, WS-12 has high temperature resistance, and continuous high temperatures of 200°C will not affect the cooling strength of the product. However, during the application process, there is basically no cooling sensation when tasting WS-12 directly. There has been a patent report that after using a ball mill to grind WS-12 into a powder with extremely small particle size, a cooling sensation will occur in the mouth.
3 Menthol ester and carboxylic acid series products
3.1 Monomethyl glutarate
Monomethyl glutarate is a cooling agent produced by the direct esterification of natural menthol and the corresponding diacid or diacid anhydride. It has been reported in the literature that using menthol and glutaric acid anhydride to react can yield higher yields. Rate.
The cooling sensation of monomenthyl glutarate is softer and lasts longer. It is recognized as a safe cooling agent (FEMA 4006) by the Food Flavors and Extracts Manufacturers Association (FEMA). In 2002, IFF Company had a patent introducing the mixing of monomenthyl glutarate and dimenthyl glutarate in a ratio of 70:30, which can produce a better cooling sensation.
3.2 Menthyl lactate
Menthyl lactate is mainly synthesized by esterification using fermented lactic acid and natural menthol as the main raw materials, with a conversion rate of up to 75.5%. Menthyl lactate is mainly used in personal care products such as shower gel, wet wipes and talcum powder. Compared with menthol, menthyl lactate has a milder cooling effect and sensation, and the cooling sensation lasts longer.
In addition, menthyl lactate is also widely used in tobacco flavors. Since menthyl lactate has a sweet and cooling aroma, adding it to tobacco flavor can increase the sweetness of tobacco and significantly improve the taste of cigarettes. In particular, the raw materials of menthyl lactate are all natural ingredients, which are safe and harmless to the human body after volatilization at high temperatures, and will also make the flavored products more stable.
3.3 Menthone glycerol ketal
Menthone glycerol ketal is a cooling agent formed by dehydration condensation of menthone and glycerol using an acidic catalyst. Compared with menthyl lactate, menthone glyceryl ketal has a milder cooling sensation and is non-irritating to the skin, so it is often used in personal care products such as shampoo, shower gel and shaving products. In addition, menthone glycerol ketal can also be used in the preparation of daily chemicals, tobacco and cooling flavors, and is used as a cooling flavor stabilizer for mint flavors.
4 Comparison of the cooling sensation of various cooling agents
Millennium Company has provided data on the cooling intensity of various cooling agents by measuring the thresholds of various cooling agents [8]. The cooling intensity of menthol [(-)-Menthol] is defined as 100, the cooling intensity of WS-23 is 75, WS-3 and WS-12 are both 150, and WS-5 is 400. Among the menthyl ester and carboacetate series products, the cooling intensity of menthone glycerol ketal (Frescolat MGA) is about 40, and the cooling intensity of menthyl lactate (Frescolat ML) is 43, see Figure 2.
In addition, the cooling intensity of several isomers of menthol is not high, for example, D-neomenthol [(-)-Neomenthol], D-isomenthol [(-)-Isomenthol], L-neomenthol The cooling intensity of menthol [(+)-Neoisomenthol] is both 3, while the cooling intensity of L-isomenthol [(+)-Neoisomenthol] is only 11, and D-neoisomenthol [(-)- Neoisomenthol] has a cooling intensity of about 13.
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