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Honey

Honey

Honey is the most important primary product of beekeeping both from a quantitative and an economic point of view. It was also the first bee product used by humankind in ancient times. The history of the use of honey is parallel to the history of man and in virtually every culture evidence can be found of its use as a food source and as a symbol employed in religious, magic and therapeutic ceremonies (Cartland, 1970; Crane, 1980; Zwaeneprel, 1984) an appreciation and reverence it owes among other reasons to its unique position until very recently, as the only concentrated form of sugar available to man in most parts of the world. The same cultural richness has produced an equally colourful variety of uses of honey in other products.

"Honey is the natural sweet substance produced by honeybees from the nectar of blossoms or from the secretion of living parts of plants or excretions of plant sucking insects on the living parts of plants, which honeybees collect, transform and combine with specific substances of their own, store and leave in the honey comb to ripen and mature. This is the general definition of honey in the Codex Alimentarius (1989) in which all commercially required characteristics of the product are described. The interested reader is also referred to other texts such as "Honey, a comprehensive survey" (Crane, 1975).
Honey in this bulletin, will refer to the honey produced by Apis mellifera unless otherwise specified. There are other honeybee species which make honey, and other bees and even wasps which store different kinds of honeys as their food reserves.

Physical characteristics of honey
Density
Another physical characteristic of practical importance is density. Honey density, expressed as specific gravity in Table 2.4, is greater than water density, but it also depends on the water content of the honey (Table 2.4). Because of the variation in density it is sometimes possible to observe distinct stratification of honey in large storage tanks. The high water content (less dense) honey settles above the denser, drier honey. Such inconvenient separation can be avoided by more thorough mixing.

Table 2.4:

True specific gravity of honeys with different water content (White, 1975a).

Water content

(%)

Specific gravity at 20°C

Water

content

(%)

Specific gravity at 20°C

Water

content

(%)

Specific gravity at 20°C

13.0

1.4457

16.0

1.4295

19.0

1.4101

14.0

1.4404

17.0

1.4237

20.0

1.4027

15.0

1.4350

18.0

1.4171

21.0

1.3950

 
Hygroscopicity
The strongly hygroscopic character of honey is important both in processing and for final use. In end products containing honey this tendency to absorb and hold moisture is often a desired effect such as, for example, in pastry and bread. During processing or storage however, the same hygroscopicity can become problematic, causing difficulties in preservation and storage due to excessive water content. From Table 2.5 it can be readily seen that normal honey with a water content of 18.3 % or less will absorb moisture from the air at a relative humidity of above 60%.

Table 2.5

Approximate equilibrium between relative humidity (RH) of ambient air and water

content of a clover honey (White, 1975a).

Air (%RH)

Honey (% water content)

50

15.9

55

16.8

60

18.3

65

20.9

70

24.2

75

28.3

80

33.1

Surface tension
It is the low surface tension of honey that makes it an excellent humectant in cosmetic products The surface tension varies with the origin of the honey and is probably due to colloidal substances. Together with high viscosity, it is responsible for the foaming characteristics of honey.

Thermal properties
For the design of honey processing plants its thermal properties have to be taken into account. The heat absorbing capacity, i.e. specific heat, varies from 0.56 to 0.73 cal/g/0C according to its composition and state of crystallization. The thermal conductivity varies from 118 to 143 x 10-~ cal/cm2/sec/0C (White, 1975a). One can therefore calculate the amount of heat, cooling and mixing necessary to treat a certain amount of honey, i.e. before and after filtration or pasteurization. The relatively low heat conductivity, combined with high viscosity leads to rapid overheating from point-heat sources and thus the need for careful stirring and for heating only in water baths.

Colour
Colour in liquid honey varies from clear and colourless (like water) to dark amber or black (see Figure 2.2). The various honey colours are basically all nuances of yellow amber, like different dilutions or concentrations of caramelized sugar, which has been used traditionally as a colour standard. More modern methods for measuring honey colour are described below. Colour varies with botanical origin, age and storage conditions, but transparency or clarity depends on the amount of suspended particles such as pollen. Less common honey colours are bright yellow (sunflower) reddish undertones (chestnut) greyish (eucalyptus) and greenish (honeydew). Once crystallized, honey turns lighter in colour because the glucose crystals are white. Some of the honeys reportedly "as white as milk" in some parts of East Africa are finely crystallized honeys which are almost water white, i.e. colourless, in their liquid state.
The most important aspect of honey colour lies in its value for marketing and determination of its end use. Darker honeys are more often for industrial use, while lighter honeys are marketed for direct consumption. In many countries with a large honey market, consumer preferences are determined by the colour of honey (as an indication of a preferred flavour) and thus, next to general quality determinations, colour is the single most important factor determining import and wholesale prices.

Honey colour is frequently given in millimetres on a Pfund scale (an optical density reading generally used in international honey trade) or according to the U.S. Department of Agriculture classifications (White, 1975c and Crane, 1980):

USDA colour standards Pfund scale (mm)
- water white 0 to 8
- extra white > 8 to 17
- white > 17 to 34
- extra light amber > 34 to 50
- light amber > 50 to 85
- amber > 85 to 114
-darkamber > 114

 

Figure 2.2: Different coloured honeys of unifloral and

multifloral origin. (courtesy of F. Intoppa)

More recent but not widely practised methods of colour description use spectral colour absorption of honey (Aubert and Gonnet, 1983; Rodriguez L6pez, 1985).

Crystallization
Crystallization is another important characteristic for honey marketing, though not for price determination. In temperate climates most honeys crystallize at normal storage temperatures. This is due to the fact that honey is an oversaturated sugar solution, i.e. it contains more sugar than can remain in solution. Many consumers still think that if honey has crystallized it has gone bad or has been adulterated with sugar.

The crystallization results from the formation of monohydrate glucose crystals, which vary in number, shape, dimension and quality with the honey composition and storage conditions. The lower the water and the higher the glucose content of honey, the faster the crystallization. Temperature is important, since above 25 ° and below 5 °C virtually no crystallization occurs. Around 14°C is the optimum temperature for fast crystallization, but also the presence of solid particles (e.g. pollen grains) and slow stirring result in quicker crystallization (see 2.12.2). Usually, slow crystallization produces bigger and more irregular crystals.

During crystallization water is freed. Consequently, the water content of the liquid phase increases and with it the risk of fermentation. Thus, partially crystallized honey may present preservation problems, which is why controlled and complete crystallization is often induced deliberately. In addition, partially crystallized or reliquified honey is not an attractive presentation for retail shelves (see Figure 2.3).

a.
b.

Figure 2.3: Honeys in different stages of crystallization, (a) fermentation in partially crystallized honey and (b) different stages of reliquification after previous crystallization due to storage over very long periods of time or at relatively high temperatures. These unattractive changes can be avoided by controlled crystallization, proper storage and possibly pasteurization. (courtesy of F. Intoppa)

 
The composition of honey
The average composition of American honeys, more or less representative of all honeys, is shown in Table 2.6. Table 2.7 lists the various components identified in honeys from all around the world.

Sugarsaccount for 95to 99% of honey dry matter. The majority of these are the simple sugars fructose and glucose which represent 85-95% of total sugars. Generally, fructose is more abundant than glucose (see Table 2.6). This predominance of simple sugars and particularly the high percentage of fructose are responsible for most of the physical and nutritional characteristics of honey. Small quantities of other sugars are also present, such as disaccharides (sucrose, maltose and isomaltose) and a few trisaccharides and oligosaccharides. Though quantitatively of minor importance, their presence can provide information about adulteration and the botanical origin of the honey.

Wateris quantitatively the second most important component of honey. Its content is critical, since it affects the storage of honey. Only honeys with less than 18% water can be stored with little to no risk of fermentation. The final water content depends on a number of environmental factors during production such as weather and humidity inside the hive, but also on nectar conditions and treatment of honey during extraction and storage. It can be reduced before or after extraction by special techniques (see 2.6.9).

Among the minor constituents organic acids are themost important and of these gluconic acid, which is a by-product of enzymatic digestion of glucose, predominates. The organic acids are responsible for the acidity of honey and contribute largely to its characteristic taste.
Mineralsare present invery small quantities, potassium being the most abundant. Dark honeys, particularly honeydew honeys are the richest in minerals.
Other trace elements include nitrogenous compounds among which the enzymes originate from salivary secretions of the worker honeybees. They have an important role in the formation of the honey. Their commercial importance is not related to human nutrition, but to their fragility and uniqueness. Thus their reduction or absence in adulterated, overheated or excessively stored honeys serves as an indicator of freshness. The main enzymes in honey are invertase (saccharase) diastase (amylase) and glucose oxidase.

Traces of other proteins, enzymes or amino acids as well as water soluble vitamins are thought to result from pollen contamination in honey.
Virtually absent in newly produced honey, hydroxvmethylfurfural (HMF) is a byproduct of fructose decay, formed during storage or during heating. Thus, its presence is considered the main indicator of honey deterioration.

Even though some of the substances responsible for honey colour and flavour have been identified the majority are still unknown. It is more than likely that honeys from different botanical origins contain different aromatic and other substances which contribute to the specific colours and flavours and thus allow to distinguish one honey from another. Similarly, it is very likely that, depending on their botanical origin, honeys contain traces of pharmacologically active substances. Some of them have been identified, such as those responsible for the toxicity of certain honeys (see also section 2.9), but for the majority of possible substances, scientific verification requires further studies.

Table 2.6

Average composition of U.S honeys and ranges of values (White, et al., 1962)

Component

(% except pH and diastase valute)

Average

Standard deviation

Range

Water

<>17.2

1.5

13.4 - 22.9

Fructose

38.2

2.1

27.2 - 44.3

Glucose

31.3

3.0

22.0 - 40.7

Sucrose

1.3

0.9

0.2 - 7.6

Maltose (reducing disaccharides calculated as maltose)

7.3

2.1

2.7 - 16.0

Higher sugars

1.5

1.0

0.1 - 8.5

Free acids (as gluconic acid)

0.43

0.16

0.13 - 092

Lactone (as glucolactone)

0.14

0.07

0.0 - 0.37

Total acid (as gluconic acid)

0.57

0.20

0.17 - 1.17

Ash

0.169

0.15

0.020 - 1.028

Nitrogen

0.041

0.026

0.000 - 0.133

pH

3.91

-

3.42 - 6.10

Diastase value

20.8

9.8

2.1 - 61.2

 
The physiological effects of honey
Unconfirmed circumstantial evidence
For thousands of years honey was the only source of concentrated sugar. uniqueness, scarcity and desirability connected it to divinity very early in human history thus ascribing to it symbolic, magic and therapeutic significance. Much of the myth many of the traditional medicinal uses have continued until today.
Few of these medicinal benefits have seen scientific confirmation and they are not always exclusive to honey. The majority are due to the high sugar content and therefore can also be found in other sweet substances with high sugar contents. It was not by accident that sugar, when first introduced to Europe, was considered a medicine for many diseases and was used with caution.

The major properties and effects commonly attributed to honey (Donadieu, 1983) are briefly described below, but there are hundreds of different local uses in various countries, according to the specific cultures and traditions, and it is impossible to mention all of them. The Koran also mentions several uses for honey and other bee products (El Banby, 1987).

Nutritional benefits
Honey is said to facilitate better physical performance and resistance to fatigue, particularly for repeated effort; it also promotes higher mental efficiency. It is therefore used by both the healthy and the sick for any kind of weakness, particularly in the case of digestive or assimilative problems. Improved growth of non-breast fed newborn infants, improved calcium fixation in bones and curing anaemia and anorexia may all be attributed to some nutritional benefit or stimulation from eating honey.

Benefits to the digestive apparatus
Honey is said to improve food assimilation and to be useful for chronic and infective intestinal problems such as constipation, duodenal ulcers and liver disturbances. Salem (1981) and Haffejee and Moosa (1985) have reported successful treatment of various gastrointestinal disorders.

Benefits to the respiratory system
In temperate climates and places with considerable temperature fluctuations, honey is a well known remedy for colds and mouth, throat or bronchial irritations and infections. The benefits, apart from antibacterial effects, are assumed to relate to the soothing and relaxing effect of fructose.

Benefits to skin and wound healing
Honey is used in moisturizing and nourishing cosmetic creams, but also in pharmaceutical preparations applied directly on open wounds, sores, bed sores, ulcers, varicose ulcers and burns. It helps against infections, promotes tissue regeneration, and reduces scarring also in its pure, unprocessed form (Hutton, 1966; Manjo, 1975; Armon, 1980 and Dumronglert, 1983). If applied immediately, honey reduces blistering of burns and speeds regeneration of new tissue. Many case histories are reported in the literature for human as well as veterinary medicine (sores, open wounds and teat lesions in cows). A cream, applied three times per day and prepared from equal parts of honey, rye flour and olive oil, has been successfully used on many sores and open wounds -even gangrenous wounds in horses (Lu~hrs, 1935). Lu cke (1935) successfully tested a honey and cod liver oil mixture suspended in a simple non-reactive cream base on open wounds in humans, but he gave no details on proportions.

Table 2.7:

List of coupoponds found in honey, but not necessarily present in all honeys

(from Gonnet and Vache, 1985 modified with data from Withe,

1975b Bogdanov and Crane, 1990)

 
Benefit to eye disorders
Clinical cases or traditional claims that honey reduces and cures eye cataracts, cures conjunctivitis and various afflictions of the cornea if applied directly into the eye, are known from Europe (Mikhailov, 1950), Asia, and Central America. This is said to be more true for Meliponid and Trigonid honeys from South and Central America and India. There are also case histories of ceratitis rosacea and corneal ulcers, healed with pure honey or a 3 % sulphidine ointment in which Vaseline was replaced by honey.

Medicine-like benefit
Frequently, specific benefits of unifloral honeys are reported, based on the traditional assumption that honey made from the nectar of a medicinal plant has the same or similar beneficial activity as the one recognized for the whole plant or some parts of it. Even if no transfer of active ingredients is involved, mechanisms similar to homeopathic potentiation are possible. Empirically effective therapies such as Bach flower therapy and aroma-therapy suggest that there can be much more to the medicinal value of honey than chemical analysis and quantification reveals. These claims are not supported by orthodox scientific evidence.

Diabetes
Frequently, claims are voiced that honey is good for diabetics. This is unlikely to find confirmation because of its high sugar content. However, it is better than products made with cane sugar, as a study by Katsilambros et al., (1988) has shown. It revealed that insulin levels were lower when compared to the uptake of equal caloric values of other foods, but blood sugar level was equal or higher than in the other compared products shortly after eating. In healthy individuals, the consumption of honey produced lower blood sugar readings than the consumption of the same quantity of sucrose (Shambaugh et al., 1990).

Ayurvedic medicine
Traditional, but well-studied medicinal systems as the ayurvedic medicine of India, use honey predominantly as a vehicle for faster absorption of various drugs such as herbal extracts. Secondarily, it is also thought to support the treatment of several more specific ailments, particularly those related to respiratory irritations and infections, mouth sores and eye cataracts. It also serves as a general tonic for newborn infants (see also section 2.9), the young and the elderly, the convalescent and hard working farmers (Nananiaya, 1992, personal communication). In general, no distinction is being made between honey from Apis mellifera A. cerana or A. dorsata.

Other benefits
Honey is said to normalize kidney function, reduce fevers and help insomnia. It is also supposed to help recovery from alcohol intoxication and protect the liver; effects also ascribed to fructose syrups. Heart, circulation and liver ailments and convalescent patients in general improved after injection with solutions of 20 and 40% honey in water (Kaul, 1967).

Scientific evidence
According to scientific evidence it would be better to consider honey as a food, rather than a medicine. Most of the benefits described above, at least for internal use, can most likely be ascribed to nutritional effects of some kind. On the other hand, our scientific understanding of cause and effect, typically only confirmed if a single compound measurably affects a well defined symptom, is far too limited to explain possibly more complex and subtle, particularly synergistic interactions.

Energy source
As food, honey is mainly composed of the simple sugars fructose and glucose, which form the basis of almost all indications on how, when and why to use it. The main consideration is the fact that honey provides immediately available calories, from which it derives its energy value for healthy and sick people: quick access to energy without requiring lengthy or complicated digestive action. The same direct absorption also carries a risk of pathological sugar metabolism, such as diabetes and obesity.

Non-energetic nutrients
Often honey is recommended because of its content of other nutrients like vitamins and minerals, but their quantity is so low that it is unrealistic to think they can provide any significant supplement in a deficient diet (Table 2.8). Similar arguments are made for the nutritional and health benefits from most other bee products, particularly pollen and royal jelly. Although their beneficial characteristics have been shown in numerous cases, they cannot be based on simple numeric values, i.e. X amount of substance Y. Yet, it is well known that the quality and availability of a nutrient is important for its usefulness to the body. Micronutrients in unprocessed honey can be assumed to be of the highest quality possible. Thus from a nutritional point of view, a synergistic balancing effect or one that unlocks the availability of other nutrients already present, is one of the more plausible yet untested hypotheses.

Topical applications
Topical applications under controlled conditions have shown accelerated wound healing in animals (Bergman et al., 1983, El Banby et al. 1989) and of experimental burn wounds in rats (Burlando, 1978) but also of various types of wounds, including post-operative ones in humans (Cavanagh et al., 1970; Kandil et al., 1987a, b and 1989; Effem, 1988 and Green, 1988). Similar, yet not equal, effects are obtained with the application of purified sucrose and special polysaccharide powders (Chirife et al., 1982). External as well as internal wounds from operations become bacteriologically sterile within a few days and dry out. The simultaneous stimulation of tissue regeneration by honey reduces scarring and healing times. In addition, dressings applied with honey do not stick to the wounds or delicate new skins. In many tropical field hospitals, where antibiotics and other medicines are scarce, honey has been employed successfully for a long time.

 Table 2.8:

Nutrients in honey in relation to human requirements (Crane, 1980)

Nutrient

Unit

Average amount in 100 g honey

Recommended daily intake

Energy equivalent
Vitamins
A
B1 (Thiamin)
B2 (Riboflavin)
Nicotinic acid (niacin)
B6 (Pyridoxine)
Pantothenic acid
Bc (Folic acid)
B12 (Cyanocobaltamine)
C (Ascorbic acid)
D
E (Tocopherol)
H (Biotin)
Minerals
Calcium
Chlorine
Copper
Iodine
Iron
Magnesium
Phosphorous
Potassium
Sodium
Zinc

kcal

 

I.U.

mg.

mg.

mg.

mg.

mg.

mg.

mg.

mg

mg.

I.U.

I.U.

mg.

mg.

mg.

mg.

mg.

mg.

mg.

mg.

mg.

mg.

mg.

304

 

-

0.004 - 0.006

0.002- 0.06

0.11.- 0.36

0.008 - 0.32

0.02 - 0.11

-

-

2.2 - 2.4

-

-

-

 

4 - 30

2 - 20

0.01 - 0.1

-

  1. - 3.4

0.7 - 13

2 - 60

10 - 470

0.6 - 40

0.2 0.5

2800

 

5000

1.5

1.7

20

2.0

10

0.4

6

60

400

30

0.3

 

1000

 

2.0

0.15

18

400

1000

-

-

15

Antibacterial activity
Antibacterial activity is the easiest to test and is probably the most studied biological activity of honey. In normal honey it is attributed to high sugar concentration and acidity (pH range 3.5 to 5.0). Yet, since also diluted honey has shown antibacterial activity, the active ingredient was attributed to an elusive substance generically termed "inhibin". Much of this activity was later attributed to hydrogen peroxide (H202) an enzymatic by-product during the formation of gluconic acid from glucose. The responsible enzyme, glucose oxidase is basically inactive in concentrated normal honey. Thus, in honey solutions (diluted honey) with the right pH, antibacterial activity is largely due to the presence of hydrogen peroxide. The biological significance of such a mechanism arises from the requirement to protect immature honey (with high moisture content) inside the colony until higher sugar concentrations are achieved.

Both mechanisms can partially explain the sterilizing effect of honey on wounds and some of its efficacy against cold infections, but it does not explain its beneficial effect on burn wounds (Heggers, et al., 1987) and faster wound healing with less scarred tissue. Subralimanyam (1993) has experienced 100% acceptance of skin grafts after storage in honey for up to 12 weeks. Antibacterial activity varies greatly between different types of honey (Dustmann, 1979; Revathy and Banerji, 1980; Jeddar et al., 1985 and Molan et al., 1988). In addition to glucose oxidase, honey seems to contain other mostly unknown substances with antibacterial effects, among which are polyphenols. These other factors have been identified in a few cases (Toth et al., 1987; Bogdanov, 1989 and Molan et al., 1989) but as a whole there are few scientific studies on the various claims of the beneficial effects of honey. However, it has been well demonstrated that most of the antibacterial activities of honey are lost after heating or prolonged exposure to sunlight (Dustmann, 1979).

Information sources on honey therapy
Mladenov (1972) published a book (in Rumanian) on honey therapy in Rumania and there are several articles on honey therapy in Apimondia (1976) as well as in Crane (1975 and 1990). The American Apitherapy Society collects case histories and scientific information on all therapeutical uses of bee products.

Caution
The consumption of honey by infants less than one year of age is not recommended by the US Food and Drug Administration (Anonymous, 1981). This recommendation is based on the correlation of some infant deaths with the ingestion of botulism spores (Clostridium botulinum) from honey. The spores were recognized in very few samples of Californian honey for the first time in 1976 (Huhtanen et al., 1981) and more recently also in the UK (Crane, 1979) and Italy (Aureli et al., 1986). Other surveys in Italy (Quagho et al., 1988), France (Cohn et al., 1986) and Norway (Hetland, 1986) have not found any C botulinum spores in any honey samples. Though omnipresent in the environment and in many foods, the spores normally are not capable of developing in the intestines of adults or children. However, since very young infants often have less acidic digestive tracts amd less competition from a bacterial flora as yet little developed, Clostridium spores may develop in their intestines. The toxin produced by the bacteria binds irreversibly to motor nerve endings and can only be overcome by the growth of new nerve endings. Some of the typical symptoms are mild paralysis (failure to thrive), moderate to severe paralysis, which requires hospitalization, and fulminant (sudden and intense) paralysis which can lead to death without warning. Other milder symptoms can be constipation, listlessness, lethargy, diminished appetite or activity and lack of muscle control.

In the USA there have been direct correlations between honey consumption and infant botulism, but it is difficult to say whether the one third of world-wide infant botulism cases, in which infants had prior exposure to honey, were due to ingestion of spores from honey. Spores in honey cannot grow or multiply unless they have a watery, anaerobic (no oxygen) medium with a more or less neutral pH. Therefore even in the newborn infant, special conditions have to come together to allow the spores to germinate and produce their toxin, such as after changes in the intestinal flora due to antibiotics, anomalies of intestinal secretions or others. The risk for a child less than one year old contracting this infection has been estimated by Lawrence (1986) to be about 1 in 12,000. Such a risk is likely to be higher during the first one or two months and lower during the second half of the year.

In India and many other parts of the world honey is given to newborn babies during the first few days of life as a special tonic, particularly if they were born weak or prematurely (Arora and Kual, 1973; Bansal et al., 1973 and Bhandari and Patel, 1973). In countries with better infant nutrition and generally more hygienic conditions, honey may be eliminated from the diet of an unweaned child, since it is not an essential food. Under less favourable nutritional conditions the risk of ingesting C. botulinum spores through eating honey and the resulting possibility of death must be weighted against the benefit of strengthening the young organism against many other more common stresses and diseases.

Normally, C. botulinum causes problems only in badly preserved products (contaminated or insufficiently boiled preserves or conserves, pH near 7, absence of oxygen, and storage at room temperature). Cooking the product at 800C for a few minutes will destroy the toxin and bacteria, but spores will survive up to 1300C. The presence of C. botulinum in honey is not due to any carelessness or mistreatment of the honey, nor can it be eliminated with normal processing other than ultrafiltration. Conditions in properly stored honey will not allow the bacteria to grow and produce any toxin. Fortunately, it is not a risk for anybody with a healthy intestinal flora or above the age of six months or a year.

Products containing honey and intended for human consumption or cosmetics should be treated as carefully as any food item, and with even greater care as regards storage if they are prepared with no preservatives.
 
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