Described as a sweet, yellow, viscous liquid produced by bees from flower nectar, honey is actually a solution of high levels of glucose, fructose and other sugars made with water. Sugars determine the basic properties of honey. It contains 17.20 percent water, 80.85 percent carbohydrates, and 0.51 percent proteins, amino acids, vitamins, and minerals.
During honey extraction, heat treatment is applied to facilitate the filtration process and to delay crystallization. Especially if the water ratio of honey is over 18%, heating should be applied in order to prevent fermentation and delay crystallization. Correct application of the heating process stops fermentation by killing microorganisms found in honey, reduces the amount of water and increases its fluidity, and also improves the marketing quality of the honey by dissolving the crystal particles present in the honey.
However, if the applied heat treatments are not done carefully and in a controlled manner, it decreases the quality and nutritional value of honey. If the honey is heated at high temperature or for a very long time, the taste and aroma of the honey changes, the color becomes darker, and quality losses occur as a result of the loss of diastase (amylase), invertase (saccharase) and glucosidase enzymes.
Despite the decrease in diastase activity, fructose breaks down and increases the amount of hydroxymethyl furfurol (HMF). Therefore, the main principle in the heating of honey should be to keep the yeast that causes fermentation at the lowest temperature that will prevent crystallization and as soon as possible.
Changes in Taste and Aroma in Honey as a Result of Heating
Each honey has a unique taste. The flavor of honey comes from the combination of fructose, glucose, gluconic acid, and proline, which are the main ingredients of sugar, organic acids and amino acid fractions in honey. The aroma of honey can vary according to the characteristic esters in the nectar of different flowers. The main ingredients of the flavor in honey are esters, aldehydes, ketones, alcohols, and free acids. Alcohols take the widest place among these substances.
The structure of these compounds can be disrupted by heat treatments and the pleasant characteristics of honey are lost. In addition, the high temperature disrupts the structure of the sugars in honey, causing caramelization and spoils the taste and color of the honey. Honey has a special smell depending on the pollen in it. In honey heated at high temperatures, the structure of the aroma substances that give the honey natural smell, like diketone, is destroyed and a large part of it is lost.
Loss of Enzymes in Honey as a Result of Heating
Honey is very rich in enzymes. The main known enzymes of honey are amylase (diastase), invertase (sucrose), catalase, and phosphatase enzymes. Some of the enzymes are made up of nectar and the secretion left by the aphids on the leaf, and a large part of them from the salivary gland secretions of the bees. The enzymes in it distinguish honey from other flavoring substances. Heat and light adversely affect the activity of enzymes in honey, especially diastase and invertase.
The diastase enzyme is a reagent in determining whether honey is heated or not. The low number of diastasis is an indication that honey is being adorned or heat is applied above 55 ° C. The number of diastases in honey cannot be less than 8. However, the number of diastases in honey such as citrus honey, which naturally contains a low amount of enzymes and whose HMF amount is not more than 15 mg/kg, cannot be less than 3. In addition, as the temperature increases, the enzyme diastase breaks down and decomposes more quickly.
Bees convert sucrose from nectar to glucose and fructose with the help of another enzyme, invertase. The amount of this enzyme may vary depending on the nectar source and density, the bee age and the nectar flow period. Like all other enzymes in honey, invertase is heat sensitive. When the studies on the subject are examined in the literature, it can be seen that the invertase enzyme, which is heated up to the same temperatures, breaks down and breaks down faster than the diastase enzyme. Therefore, in some countries, the invertase enzyme is used as a reagent in order to determine the heat treatment applied to honey.
When the change of invertase enzyme caused by heating in different honey types is analyzed, it can be seen that the decrease in the invertase enzyme starts at 35 ° C. Studies have shown that the amount of HMF does not increase significantly at 55 ° C, while the invertase enzyme is reduced by half. Although citrus honey initially has the lowest concentration of invertase enzyme, it is the example of honey that shows the most resistance to heat treatment. At 75 ° C, it is seen that the enzyme is almost completely destroyed.
While bees produce honey, the glucose oxidase enzyme breaks down glucose in the presence of water and oxygen, and hydrogen peroxide is released. The hydrogen peroxide formed gives the honey antimicrobial properties. Glucosidase enzyme, which is effective in the formation of hydrogen peroxide, is damaged by heat and light. In a study, loss of hydrogen peroxide production was observed by keeping the honey in the light for 10 minutes. In another study conducted by heating the honey for 10 minutes at 70 ° C, it was determined that honey lost their antimicrobial activities by 80%.
Approximately 200 compounds that play a role in antibacterial activity in honey heated up to 37 ° C are broken down. While heating up to 40 ° C, invertase and other important enzymes are broken down, heating at 50 ° C and above distorts the valuable sugars in the honey and turns it into the caramel. Generally, all heat treatments performed over 10 ° C cause deterioration in the structure of honey.
Increased Amount of Hydroxymethyl Furfural (HMF) in Honey as a Result of Heating
The content of hydroxymethylfurfural (HMF) in honey is affected by heat treatment. HMF is a compound formed by the reaction between sugars and amino acids resulting from heat treatment and the amount is limited in order to prevent excessive heat application in many products. It is undesirable to have HMF in foods. It causes undesirable changes in the taste, color, and smell of the product. It has been used as a quality parameter in honey for years. In addition, HMF has been found to have genotoxic and tumorigenic effects.
Fresh honey may contain small amounts of HMF. The starting amount of hydroxymethylfurfural varies depending on the chemical properties of the honey and the climate, such as sugar concentration and pH. However, it was found that the amount of HMF formed in the honey did not depend on the initial HMF amount of honey. It was determined that the HMF level in honey is largely related to the temperature and duration of the heat treatment applied. In a study, the results of honey samples kept for 24 hours in a water bath of 35, 45, 55, 65 and 75 ° C were examined and the relationship between the heat treatments applied to different kinds of honey and the change in the amount of HMF was analyzed.
Different HMF values may occur in different kinds of honey with the same processes. The reason for this change is that the chemical properties and nectar sources of honey are different. But in all of them, when the temperature exceeds 65 ° C in common, the amount of HMF has exceeded the permitted limits. Hydroxymethyl furfural (HMF) is formed by heating the honey, as well as it can occur over time in the honey that is kept for a long time. As long as the honey is stored for a long time and heated at high temperatures, this rate rises to 30-40 milligrams/kilograms, and sometimes it can exceed these limits. Studies have demonstrated the effect of storage temperature on the amount of HMF formed in honey. The amount of HMF increases significantly in honey stored under unfavorable conditions.
If honey is in transparent packagings, such as a glass jar, it should be stored in the dark. Light, storage temperature and relative humidity are factors that affect the storage of honey. If the honeycombs taken from the hive are to be stored for a long time, storehouses with a temperature of less than 10 ° C and relative humidity of 60% should be used. As the heating time increases, the number of HMF increases in honey. In addition, HMF has harmful effects on honey bees. HMF occurs when high-fructose-containing corn syrups, which are used in bee nutrition because they are cheap are exposed to heat treatment. Because the amount of HMF increases in direct proportion with the sugar ratio (especially fructose). According to researches, it is sufficient to heat these syrups at 48 ° C in order to see large increases in the amount of HMF. Jachimovicz and Sherbiny discovered in 1975 that HMF was responsible for bee deaths.
The amount of 15 mg / 100g HMF in commercially acid-hydrolyzed invert sugar syrup is reported to be fatal for bees. When fed with sugar syrup with 15 mg / 100g HMF content, an average of 58% of bees died within 20 days. Amounts of 3-6 mg / 100g HMF are harmless for bees. As a result, many experts argue that the amount of HMF in invert sugar syrups should not exceed 2 mg / 100g. As a result of the researches, it has been determined that the HMF rate of honey taken from bees fed with invert sugar syrup is 20 times more than honey obtained from bees fed with honey and sucrose syrup.
The researchers stated that this was due to the high-temperature exposure of the invert sugar syrup. Feeding with honey and syrup with high HMF content can lead to decreased performance of bees, poisoning due to HMF level and even mass bee deaths. According to the law, the amount of HMF in honey can be up to 40 mg/kg. The amount of HMF in honey originating from tropical climatic regions should be 80 mg/kg at most, provided that it is stated on the region label.
Things to Do to Protect the Honey From the Harm of Heating
- It should be remembered that all heat treatments above 10 ° C applied to the honey will cause a change in the structure of the honey. If heat treatment is to be applied, it should be applied at the lowest possible temperature for a short time.
- Filtration, ultrasonic wave method, cold shock application method or microwave heating methods can be used instead of the classical heating methods to prevent crystallization.
- Honey harvesting should be done at the appropriate time. Thus, the water rate in the honey will be low and there will be no need to apply heat treatment to prevent fermentation and to decrease the water rate.
- Honey should be stored under suitable conditions. When storing, it is necessary to pay attention to factors such as light, storage temperature, and relative humidity. If honey is in transparent packagings, such as a glass jar, it should be stored in the dark. In honey stored under improper conditions for a long time, there is a decrease in enzyme activity and an increase in HMF.
Heated Honey Concept in Ayurveda
Ayurveda or Ayurvedic Medicine is an ancient health system originating from India, but today has many followers and advocates around the world. Ayurveda primarily aims not to get sick, and diagnosis and treatment processes follow this concept.
In Ayurvedic medicine, it is believed that the disease is caused by physical and mental imbalance, which reduces the endurance of the body. With the aim of correcting this imbalance, the body is balanced in a way that eliminates the disease by methods such as herbal formulas, changing lifestyle and diet. Yoga and meditation are also indispensable parts of this system.
According to Ayurveda, heated or cooked honey (including honey added to hot drinks) is toxic because it closes the chakras. This is the biggest basis of the claim that cooked honey is toxic, which is harmful to the human body. There is no successful scientific study that honey becomes toxic after its temperature rises. Because there is not enough research and experiments on the subject yet.
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