There are differences between the quality of honey of different shapes and appearances according to plant source, production, and marketing methods.
The quality of honey is determined not only by a single parameter but also by examining several parameters. Melitopalinological, physical, chemical and organoleptic analyses of honey must be performed together to determine the quality of honey.
Melitopalinological Analysis for the Determination of Honey Quality
Melitopalinology (microscopic analysis of honey), along with organoleptic analysis, has been used in the determination of the botanical and geographical origin of honey for the last thousand years. Pollen analysis provides important information about the fermentation of honey, whether it contains adulteration, starch grains, and microscopic particles contaminated with honey such as mineral powders that should not be present in the honey.
Melitopalinological analysis of honey is an effective method that provides information on the origin, geographical origin and quality of honey from nectarine plants that are the source of honey. Pollen analysis of honey was first made by Pfister in 1845 and this method has been used for many years to determine the quality of honey. Honey pollen analysis is the most used method to determine the quality of honey. In the following years, the examination of microscopic analysis of honey in the world continued in parallel with the equivalent world technology.
Physical and Chemical Analyzes for the Determination of Honey Quality
The differences in the physical and chemical properties of honey depend on the plant source, the color of the nectar and its pollen, its flavor, moisture, protein, and sugar content. Studies on the physical and chemical properties of honey contain a lot of literature in the world due to the importance of the subject.
Effect of Physical Content of Honey on Its Quality
- Taste and Aroma of Honey
The composition and taste of honey vary depending on the source of the nectar, the climate and the method used by the beekeeper in the processing process. Maeda et al. (1962) reported that the taste of honey depends on the amount of proline, sugar and gluconic acid. Volatile and semi-volatile organic compounds in honey affect aroma/odor quality to a great extent.
The taste and aroma of honey vary depending on whether it is monofloral or poly floral. Honey is defined as monofloral or poly floral depending on the plant diversity of the pollen level in honey. In monofloral (uni floral) honey, the proportion of the original nectar from which honey is obtained is at least 51%, or the pollen content of a single plant species is above 45%. Honey can be named using the name of the plant from which it was obtained (eg Acacia honey, chestnut honey, manuka honey, etc.). Monofloral honey has a distinctive aroma, specific to their original nectar source. Poly floral honey is not dominant in the single plant species pollen. As with Anzer honey, the nomenclature is usually made according to the geographical region from which it is obtained.
- Color of Honey
The color of honey varies from light to dark amber, even black. The components that affect the color of honey are different plant pigments such as carotene, xanthophyll, anthocyanin. Many studies have shown that the color of honey varies with floral welding, industrial processing methods, temperature, and storage time. Pollen grains (morphology and color) can be effective in determining the color of honey. The mineral content of dark-colored honey is higher than light-colored honey. Dark honey has a high incidence of phenolic acid derivatives and contains greater amounts of flavanoid.
The color of the honey is evaluated according to the Pfund scale. According to experts, the color of honey can vary from water white to dark amber. The colors of the nectar and pollen, the sugar reactions in honey and whether the honey is old or new, affect the color. The color of honey comes from compounds such as polyphenols, flavonoids, terpenes and carotenoids that can absorb light in the visible range. In addition, Maillard reaction products such as melanoidin contribute to the color of honey. Maillard reaction or non-enzymatic browning occurs between amino groups of amino acids and reducing sugars and is a common side effect of honey preservation. Browning of honey during storage is a factor adversely affecting consumer choice. For a long time and especially at high temperatures, the honey will become darker. In two separate studies, where various honey samples were stored at 37 ° C for 90 days and at 35-40 ° C for 4 years, the darkening of the color was observed due to increased storage time. In another study, it was found that the amount of UV absorbing compounds and melanoidins increased in darkened honey after being kept for 1-3 years.
- The Viscosity of Honey
The viscosity depends on the composition of the sugars in the structure according to the content of honey (disaccharides give more viscosity), the number of small crystals and air bubbles it contains and the moisture content. When designing and using the equipment used in honey processing, the viscosity of honey is taken into consideration. It is known that high heat treatment of honey reduces viscosity. However, it has been reported that the viscosity increases when honey treated with high heat treatment is brought back to room temperature and kept.
The viscosity of honey is important at all stages of honey production, starting from extraction from the hive, to the process of filtration, mixing, processing and packaging. Generally, the viscosity of honey decreases as the number of water increases. The viscosity of honey varies depending on temperature, humidity, and botanical origin, and at low humidity, it is more affected by temperature changes.
- Hygroscopic Properties of Honey
Honey is a product with moisture absorption (hygroscopic). The moisture absorption of honey varies depending on its specific structure, sugar content and the amount of water in it. The moisture value of honey varies until it reaches the equivalent ratio with the air humidity. Due to its hygroscopic properties, honey keeps the baked goods and candies fresh and soft and is used to prevent excessive drying of tobacco products.
- Surface Tension Force of Honey
Although the surface tension force varies due to the colloidal substances whose quantity varies according to the source of the honey, it is generally low, because of this feature, honey is used as a moisturizer in cosmetic products. As the surface tension force and density increase together, honey foams.
- Honey Polarization
The direction and amount of the polarization of honey are dependent on the type of honey and the amount of sugar it contains. Since flower honey turns polarized light to the left and secretion honey turns to the right, the botanical source of honey can be understood by making use of this feature. This is a normal result of the predominant presence of fructose with negative specific rotation in the content of the flower honey.
- Crystallization of Honey
The most important physical quality criterion is the crystallization of honey. Crystallization is a natural process and there is no difference in nutritional value between crystallized honey and liquid honey. Crystallization occurs when the glucose in the honey is separated from the water and the glucose molecules precipitate into small crystals by taking other particles in the honey. Natural crystallization is undesirable by consumers as it leads to degradation of honey texture. Furthermore, the weak liquid phase separated from the sugar may initiate fermentation. In order to prevent these problems, industrial crystallization applications are made by using the Dyce method. In this method, about 10-20% of the well-crystallized honey is mixed into the liquid honey and left at 14 ° C to initiate the crystallization process.
When crystallization is done in a controlled manner, cream honey is obtained in the consistency of butter and texture. Cavia et al. have long investigated the effects of the enclosure on crystalline honey and liquid honey obtained by the industrial method themselves. As a result of the study, it was determined that the free acid level of 2 of the liquid honey samples and 1 of the cream honey samples which were analyzed at 30 months increased above the standards (50 meq/kg). It has been reported that the enclosure increases the pH and free acid level of honey, but industrial crystallization has no such effect. Many factors affect crystallization in honey. The moisture and dextrin content of honey, water activity, the presence of microcrystals in honey, the storage temperature and the pre-applied heat treatments are some of them. Particles and air bubbles remaining in the honey during filtration are factors that increase crystallization. The glucose/water ratio and fructose/glucose ratio affect crystallization.
- Fermentation of Honey
The fermentation of honey is an important problem due to the ubiquity of osmophilic yeasts. These specialized yeasts disrupt the structure of honey with high water content. Fermentation of honey occurs as a result of the activity of osmotolerant yeasts on fructose and glucose, due to the formation of ethyl alcohol and carbon dioxide. Alcohol is broken down into acetic acid and water in the presence of oxygen so that honey begins to ferment and the taste may deteriorate. In honey, fermentation-causing yeasts are naturally present, and Saccharomyces spp. is the most common of these. In honey, the presence of high monosaccharide (fructose and glucose) and low moisture content prevent the development of osmotolerant bacteria.
- Electrical Conductivity of Honey
Electrical conductivity is a physical property of honey that varies depending on the source of nectar and the amount of mineral, organic acid, and protein in honey. Electrical conductivity is one of the most important parameters that distinguish flower honey from secretory honey.
Effect of Chemical Content of Honey on Its Quality
Honey contains approximately 181 substances. According to White, (1979a), honey contains 200 substances. Honey contains about 80% sugars, 17% water and other minor compounds such as organic acids, mineral salts, vitamins, proteins, phenolic compounds, fats, and free amino acids. The content of honey also includes lactones, vitamins (B1, B2, C and nicotinic acid), pollen, beeswax, and pigments.
The content of honey varies depending on differences in plant origin, climatic conditions and environmental factors. Inorganic compounds in honey include water, potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), manganese (Mn), iron (Fe), chloride (Cl), sulfur (S), phosphorus (P) and silicon (Si) (Crane, 1980). The mineral content of honey and trace elements can be used to determine the geographical origin. The amount of amino acid in honey is 1% and a large part of the total amount of amino acid, such as 50-80%, consists of proline.
The content of honey contains a large number of phenolic compounds, the presence of which varies greatly depending on the plant origin of honey. There is a correlation between the total amount of phenolic compounds of honey and antioxidant activity. In secretory honey, the total amount of phenolic compounds has the highest value. The determination of the total amount of phenolic compounds of honey is a good parameter in determining the quality and therapeutic properties of honey. The honey also contains volatile substances that are responsible for the formation of the characteristic taste.
- Carbohydrate Content of Honey
The sugars in honey are formed by the activity of various enzymes on nectar sucrose. Honey contains about 80% carbohydrate. Carbohydrate is the natural food of honey bees and is mostly used in energy production. Carbohydrates can be converted into fat by honey bees and stored. Adult bees can use glucose, fructose, sucrose, trehalose, maltose, and meiezitose. However, they cannot use rhamnose, xylose, arabinose, galactose, mannose, lactose, raffinose, dextrin or inulin. Nectar collected by honey bees with their mouths moves from the esophagus to the stomach. The sucrose in nectar is broken down in the stomach by glucose and fructose by invertase enzyme. The result is a complex mixture of about 70% monosaccharides (glucose and fructose) and 7% disaccharides consisting of glucose and fructose with various configurations of glycosidic interactions.
Fructose and glucose are the main monosaccharides found in honey. Honey also contains a small proportion of other sugars such as sucrose and maltose. In many kinds of honey, fructose is high, glucose is the second main sugar, and these two sugars account for about 75% of honey carbohydrates. Other carbohydrates that comprise the content of honey are maltose and sucrose as main disaccharides meiezitose as the main trisaccharide and some oligosaccharides to a lesser extent.
- Moisture Content of Honey
The moisture content of honey varies during the ripening period depending on the climatic conditions, the moisture of the nectar that forms the source of honey and the storage conditions after extraction. Therefore, the moisture content of honey can vary between 17-19. Water ratio is an important parameter in terms of the shelf life of the honey.
The moisture content of honey varies from year to year depending on the environmental conditions and the processing time of the honey. High moisture content can accelerate crystallization in some honey types and produce an increase in water activity, leading to the development of yeasts that will cause fermentation. Honey with high water content is prone to fermentation.
- Acidity of Honey
The pH values of honey vary between 3.5-5.5 depending on the presence of organic acids that contribute to their taste. Acidity contributes to the taste of honey, its stability against microorganisms, an increase of chemical reactions in honey, antibacterial and antioxidant activity. The acidity of honey depends on the presence of organic acids, in particular, inorganic ions, such as glycolic acid, phosphate, and chloride, which make up less than 0.5% of the constituents of honey.
Organic acids in honey are glycolic, formic, acetic, butyric, lactic, oxalic, citric, succinic, tartaric, maleic, malic, pyroglutamic, fulvic, α-ketoglutaric, and glycolic acids, as well as α or β glycerophosphate and glucose-6-phosphate. The source of the presence of other acids, except glycolic acid, in honey, is unknown. Many acids are present in nectar at a very high rate in the Krebs cycle of biological oxidation. Glycolic acid, which provides the greatest contribution to the acidity of honey, is formed by the effect of glucose oxidase enzyme on the glucose and is in equilibrium with gluconolactone. In addition, other organic acids, together with inorganic anions, contribute to the acidity of the honey.
- Mineral Content of Honey
Mineral matter concentration of honey is between 0.1% -1%. Potassium is the main metal in honey, followed by chlorine, sulfur, silicon calcium, magnesium, sodium, and phosphorus. Honey contains trace amounts of iron, copper, zinc, and manganese.
The amount of mineral matter depends on the nectar composition of the plant dominating the honey. The type of soil and water in which the nectarized plant constitutes the source of honey affects the mineral amount of the nectar and pollen.
- Protein Content of Honey
The protein and amino acids in honey are mostly of plant origin and most of them come from pollen. Echigo et al. (1973) reported that honey amino acids are of different origins, such as nectar, honey bee, and pollen. Some amino acids have been found to have antioxidant properties. Amino acids in honey are proline, glutamic acid, alanine, phenylalanine, tyrosine, leucine, isoleucine.
The amino acid content of honey is about 20-300 mg / 100 g. Honey contains 1% (w / w) of amino acids and 50-85% of the total amount of amino acids is formed by proline. Apart from proline, there are 26 amino acids in close proportions depending on the origin of honey (nectar or secretion). Pollen is the amino acid source of honey and therefore the amino acid profile of honey can be used to determine the botanical origin of honey.
The proline content of honey shows characteristic values in different uni floral honey and is associated with enzymatic activity. Although it is present in different amounts in different uni floral honey types, it is impossible to classify them only by the amount of proline. Proline is an amino acid that is added by the honey bee during the conversion of nectar to honey and shows the maturity of the honey. It is thought that the amount of proline in honey and enzymes produced by honey bees, such as sucrose and glucose oxidase, indicate the maturity of honey. The amount of proline in quality honey should be higher than 350 mg/kg and at least 66% (usually 80-90%) of the total amount of amino acids. Enzymes constitute a small portion of the protein in honey.
- Enzyme Content of Honey
Diastase and invertase are added by honey bees. Honey bees mix the nectar they collect with the secretions of the salivary and hypopharyngeal glands, while the nectar in the hive is transferred from the bee to the bee before being filled into the honeycomb eyes, more secretions are added to facilitate the ripening of the honey. The amount of enzyme added as a result of this process varies depending on the age, physiological stage and feeding of honeybees, colony strength, temperature, nectar flow. Diastasis and invertase are the most important nutritional enzymes in the honey. Diastase hydrolyzes carbohydrates for easy digestion while invertase hydrolyzes sucrose and maltose. Diastase breaks starch grains in dextrin and maltose, while invertase breaks down sucrose to glucose and fructose.
Invertase catalyzes the main reaction that leads to the conversion of nectar to honey. White and Maher (1953) stated that honey invertase is a variant of R-glycosidase. This was confirmed by White and Kushnir (1967). Invertase is produced in the hypopharyngeal glands of honey bees. This enzyme helps honey bees produce highly concentrated sugar solutions that are resistant to fermentation and provide high energy. Invertase activity, together with the amount of diastase and hydroxymethylfurfural, is used as a honey quality control parameter. In honey produced by Apis mellifera, the measurement of invertase activity is of commercial importance because the invertase can vary with the freshness of the honey and the temperature and storage conditions. Invertase is more sensitive to temperature changes than diastase. Invertase can be present in honey in higher amounts than diastase because they must add the invertase to both nectar and slime.
Glucose oxidase is another important enzyme that catalyzes glucose to gluconic acid and hydrogen peroxide. The antimicrobial properties of honey which are used as a therapeutic agent in gastrointestinal diseases such as wounds, indigestion, bacterial gastroenteritis, ulcer, and duodenal ulcers are mainly dependent on the hydrogen peroxide content.
Giri (1938) was the first scientist to find the presence of acid phosphatase in honey. This enzyme is a hydrolase enzyme that converts organic phosphates into inorganic phosphates. Although acid phosphatase is present in the composition of the nectar, it is mainly present in pollen. Zalewski (1965) and Ivanov (1981) investigated the effects of storage on acid phosphatase of honey; found significant reductions in acid phosphatase amount after six months. Acid phosphatase has low enzymatic activity in honey. Determination of acid phosphatase activity in honey is very important because the amount of acid phosphatase can be a criterion for the susceptibility of honey to fermentation. Giri (1938) reported that fermented honey has higher acid phosphatase activity than non-fermented honey. In addition, some researchers have stated that this enzyme may depend on the botanical source of honey. This enzyme is a useful parameter in the characterization of honey. Alonso-Torre et al. (2006) reported that as the pH of honey increases, the decrease in acid phosphatase activity decreases.
- Vitamin Content of Honey
Honey contains vitamins such as B6, vitamin C, thiamine, niacin, riboflavin, nicotinic acid, and pantothenic acid.
- Antioxidant Content of Honey
Numerous studies have been conducted with a large number of medicinal and aromatic plants, such as the leaves and fruits of fruit trees, which can be used as natural sources of components that synthesize phytochemicals with antioxidant activity and destroy free radicals. Most of these plants are visited by honey bees; as a result, plant-derived bioactive substances can be transported to honey.
When chemical analysis of honey is carried out, it is seen that it contains a large number of antioxidants that ineffective biologically occurring oxidizing degradation products which do not have nutritive properties depending on plant sources and cause many degenerative diseases and damages. The antioxidant capacity of honey depends on the polyphenolic compounds of plant origin, flavanones such as chrysin, pinobanksin, pinocembrin, enzymes such as catalase and the amount of vitamin C. Honey with a high content of flavanone is usually dark.
- HMF Content of Honey
Hydroxymethyl furfural (HMF; 5-hydroxy-2-Furancarboxaldehyde) is classified by its mutagenic activity. However, the usual cytotoxic, genotoxic and carcinogenic effects for human health have not been integrated. However, it is clear that this highly reactive component enters reactions, leading to degradation of the unstable components of the honey, leading to a decrease in the nutritional value of the honey or discoloration of the honey at high concentrations.
This is caused by dehydration of the cyclic aldehyde hexoses in acidic medium or by milliard reaction. Honey provides a suitable medium for HMF with its high saccharide content (especially hexoses), low pH value, presence of organic acid and low water activity. The amount of HMF in fresh honey is close to zero and very low. However, the amount of HMF increases during the heating and storage process. Therefore, the amount of HMF is an important criterion in determining the quality of honey. It also facilitates the determination of the freshness of honey.
The earliest record for HMF was in 1933. HMF can occur as a result of heating the honey and during storage the number of HMF increases depending on the conditions. With the studies carried out in the 1950s, HMF amount measurements in honey started to be used. In 1955, two methods were developed to use HMF to determine honey quality. In the 1700 honey samples imported to Germany and Switzerland, the honey standards of the Alimentarius Codex stated that the maximum value of HMF in honey was 4mg / 100gr, based on data from studies conducted in the 1955-1960s.
Organoleptic Analyzes for the Determination of Honey Quality
In addition to microscopic and physicochemical analyzes of honey, organoleptic analyses should be performed. Sensory analysis is performed by evaluating a product through perceptions of five sensory organs (color, smell, taste, sensation, tissue). Sensory analysis, used in many fields, allows the organoleptic profile of different types of products (such as food, cosmetics, textiles, etc.) to be extracted and to understand how these products are perceived by the consumer. Until the 1960s, sensory analysis techniques mainly depend on the personal experience of the competent authorities. Sensory analysis for honey was first used in France by Gonnet and his team along with traditional techniques.
In Italy, Gonnet’s ideas have created excitement. After that, the number of studies on the subject started to increase. These studies led to the establishment of ‘Certified Italian Honey Sensory Analysis Specialists’. It has established traditional methods and includes forms of assessment of harmonized terminology, tasting methods, criteria for selection and training of assessment experts, and sensory evaluation of single-flora Italian honey. Similarly, this heritage of Gonnet has been taken into consideration and developed in other developed European countries such as Spain.
Quality of Honey and Its Effects on Human Health
Since ancient times, honey has been considered a nutrient that promotes healthy living. Honey is the only product mentioned in almost all mythological texts. Homer’s epic Iliad and Odyssey, the Deipnosophist of the Athenians, and the philosophical texts of Plato, Aristotle, Democritus, and others have been praised for the importance of honey for people. Hippocrates stressed that the nutritional and pharmaceutical value of honey is not accidental. In ancient Greece, honey was used as a nutrient as well as for medical purposes. There are records that the medical formulas of the ancient Greeks are based on honey. The Bible describes the wound healing properties of honey.
Honey has been used since ancient times for the treatment of burns, digestive system disorders, asthma, infectious wounds, and skin ulcers. Honey is effective in the treatment of wounds, burns and stomach ulcers due to its antioxidant and antimicrobial properties. The antibacterial property of honey is the result of low water activity, hydrogen peroxide effect, high acidity, causing osmosis. Antioxidants in honey reduce the damage to colon caused by inflammation of the large intestine. According to some studies, honey has been reported to be effective in increasing probiotic bacteria in the system, thereby strengthening the immune system, reducing indigestion, lowering cholesterol and preventing colon cancer.
Chepulis (2007) found that mice fed with honey had decreased weight gain (due to indigestion reducing property of honey) compared with mice fed with other sugars in a six-week period in his study. Honey is used against mouth, throat and bronchial infections with its antibacterial properties. Honey also regulates kidney function, relieve insomnia, and it is used against antipyretic effects, and heart, circulatory system diseases, as well as liver diseases.
In clinical studies, it has been reported to be used directly against the eye, against cataract disease, conjunctivitis, and various corneal diseases. Honey, sugar syrup and other natural sweeteners are a potential hazard for babies. Clostridium botulinum endospores, which are not harmful to humans due to gastric acidity, are commonly found in the environment and thus in honey. Since the digestive enzymes of a baby are not acidic, the stomach of the baby creates a favorable environment for the development of Clostridium botulinum endospores, where it produces toxins and causes botulism. Therefore, it is recommended that infants under 12 months should not be fed either honey or other sweeteners.
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