CHAPTER 3
POLLEN

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3.1 Introduction

Innumerable stories and even more rumours exist about the mysterious powers of pollen and its nutritional value. Pollen is frequently called the "only perfectly complete food". High performance athletes are quoted as eating pollen, suggesting their performance is due to this "miracle food", just as the "busy bee" represents a role model for an active and productive member of society. Using suggestive names, labels and descriptions in marketing of various products containing pollen sometimes reach almost fraudulent dimensions, creating false hopes and expectations in people, often connected with high prices of the product. Such practices are untruthful, unethical and should be avoided.

It is however, often difficult for a lay person to verify the numerous claims, particularly those backed up with so-called reports from "doctors". Conversely, it does not always take a "scientific" study to prove that a food (or substance of herbal origin) has a medicinal or otherwise beneficial effect. Many times, modern science is not willing or able to prove beneficial effects according to its own rigid standards, methods and technologies. However, as a whole, caution should be exercised in accepting the many claims made to the credit of pollen and for that matter also for the other products incorporating products from the bee hive.

Pollen grains are small, male reproduction units (gametophytes) formed in the anthers of the higher flowering plants (see Figure 3.1). The pollen is transferred onto the stigma of a flower (a process called pollination) by either wind, water or various animals (mostly insects), among which bees (almost 30,000 different species) are the most important ones.

Each pollen grain carries a variety of nutrients and upon arrival at the stigma it divides into several cells and grows a tube through the often very long stigma of the flower. Growth continues to the embryo sac in the ovarium of the flower, inside which one egg cell will fuse with a sperm cell from the pollen and complete the fertilization. Depending on the requirements for this process and the mode of transport from one flower to the next, i.e. insects, water or wind, each species of plants has evolved a characteristic pollen type. Thus, the pollen grains from most species can be distinguished by their outer form and/or by their chemical composition or content of nutrients. The knowledge of this is used in the identification of paleontological discoveries (paleopalynology) and in the identification of geographic and botanical origin of honeys (melissopalynology).

To determine the value of pollen as a supplementary food or medicine, it is important to know that pollen from each species is different and no one pollen type can contain all the characteristics ascribed to "pollen" in general. Therefore, in this text, pollen will always refer to a mixture of pollen from different species, unless otherwise mentioned. A logical conclusion is that pollen from one country or ecologic habitat is always different from that of another. People who are allergic to pollen will have noticed this during their travels.

Close up of a lily flower. The anthers (large yellow structures) release pollen in such abundance that it falls onto the petals. Note also the pollen grains adhering to the stigma surface. (Photo courtesy of F.Intoppa)
Figure 3.1 : Close up of a lily flower. The anthers (large yellow structures) release pollen in such abundance that it falls onto the petals. Note also the pollen grains adhering to the stigma surface. (Photo courtesy of F.Intoppa)


For those who see in nature something more than just the mechanical and chemical interactions of substances and organisms, it might be added that flowers form a very special part of plants. They carry special "energies" which are used in traditional alternative medicinal practices such as therapies with Bach flowers, aroma therapy or the use of numerous herbal teas. Such energies may well be carried by certain chemical substances other than water, but this is not necessarily the case, as for example, homeopathic preparations demonstrate.

Since pollen is a part of these flowers and in addition is or represents the male reproductive portion, it also has very special "energies" or values of its own. In a wider understanding in certain philosophical environments, special plant and pollen surface structures interact with cosmic energies and may acquire some of their characteristics by this means.

Apart from these less orthodox explanations, certain empirical results have in the past been described for the effects of pollen on humans and animals. These will be discussed under medicinal uses. As far as the miracle food aspect of pollen is concerned, the diversity of pollen must be emphasized again and the fact that some pollen types (i.e., pine and eucalyptus) are nutritionally insufficient even for the raising of honeybee larvae. In an excellent review, Schmidt and Buchmann (1992) compared the average protein, fat, mineral and vitamin content of pollen with other basic foods. Pollen was richer in most ingredients when compared on a weight or calorie content basis than such foods as beef, fried chicken, baked beans, whole wheat bread, apple, raw cabbage and tomatoes. While comparable in protein and mineral content with beef and beans, Pollen averages more than ten times the thiamin and riboflavin or several times the niacin content. Pollen is usually consumed in such small quantities that the daily requirements of vitamins, proteins and minerals cannot be taken up through the consumption of pollen alone. However, it can be a substantial source of essential nutrients where dietary uptake is chronically insufficient.

If the nutritional benefit of pollen in small dosages is accepted, as described in many non-scientific publications, it must be understood as a synergistic effect. That is, a wide variety of beneficial substances interact to improve absorbtion or use of the nutrients made available to the body from regular nutrition. Pollen nutrients may also balance some deficiencies from otherwise incomplete or unbalanced supplies, absorption or usage.

The pollen which is collected by beekeepers and used in various food or medicinal preparations is no longer exactly the same as the fine, powdery pollen from flowers. The hundreds or sometimes millions of pollen grains per flower are collected by the honeybees and packed into pollen pellets on their hind legs with the help of special combs and hairs (see Figure 3.2). During a pollen collecting trip, one honeybee can only carry two of these pollen pellets.

The pollen collected by honeybees is usually mixed with nectar or regurgitated honey in order to make it stick together and adhere to their hind legs. The resulting pollen pellets harvested from a bee colony are therefore usually sweet in taste. Certain pollen types however, are very rich in oils and stick together without nectar or honey. A foraging honeybee rarely collects both pollen and nectar from more than one species of flowers during one trip. Thus the resulting pollen pellet on its hind leg contains only one or very few pollen species. Accordingly, the pollen pellet has a typical colour, most frequently yellow, but red, purple, green, orange and a variety of other colours occur (see Figure 3.3).

The partially fermented pollen mixture stored in the honeybee combs, also referred to as "beebread" has a different composition and nutritional value than the field collected pollen pellets and is the food given to honeybee larvae and eaten by young worker bees to produce royal jelly. Saying pollen is the perfect food because it is the only food source for honeybees other than honey, their major carbohydrate source is not only based on a questionable comparison between human needs and bee requirements, but also on plain misinformation.

a)
Figure a)A honeybee forager collecting pollen from a composite flower. The pollen grains caught in the specially branched hairs of honeybees are brushed off with the legs, moistened with nectar or honey and compacted in the pollen pellets on the outside of the hind legs (photo courtesy of F. Intoppa).

b)
Figure b) A scanning electron microscopic enlargement of the hind leg of a honeybee with the pollen pellet on the outside (photo courtesy of R.C. Davis). The bottom section of the leg consists of the pollen brush. The joint between the leg segments serves to compact the pollen and push it to the outside, thus forming the typical pollen pellet.

Figure 3.2: a) A honeybee forager collecting pollen from a composite flower. The pollen grains caught in the specially branched hairs of honeybees are brushed off with the legs, moistened with nectar or honey and compacted in the pollen pellets on the outside of the hind legs (photo courtesy of F. Intoppa). b) A scanning electron microscopic enlargement of the hind leg of a honeybee with the pollen pellet on the outside (photo courtesy of R.C. Davis). The bottom section of the leg consists of the pollen brush. The joint between the leg segments serves to compact the pollen and push it to the outside, thus forming the typical pollen pellet.


3.2 Physical characteristics of pollen

Pollen grains range from 6 to 200 m m in diameter, and all kinds of colours, shapes and surface structures may be observed. These are usually typical enough to allow species or at least genus identification (see Figures 3.3 and 3.4). Most pollen grains have a very hard outer shell (sporoderm) which is very difficult or impossible to digest. It is so durable that it can be found in fossil deposits millions of years old. There are, however, pores which allow germination and also extraction of the interior substances.

3.3 The composition of pollen

Since the composition of pollen changes from species to species, variation in absolute amounts of the different compounds can be very high. Protein contents of above 40% have been reported, but the typical range is 7.5 to 35%: typical sugar content ranges from 15 to 50% and starch content is very high (up to 18%) in some wind-pollinated grasses (Schmidt and Buchmann, 1992). Composition of pollen and bee-collected pollen however, has to be distinguished. Some average values for bee-collected pollen are shown in Table 3.1.

Different coloured pollen pellets collected by honeybees (Photo courtesy of F. Intoppa) 
Figure 3.3: Different coloured pollen pellets collected byhoneybees
(Photo courtesy of F. Intoppa)


The major components are proteins and amino acid, lipids (fats, oils or their derivatives) and sugars. The minor components are more diverse (Table 3.2). All amino acids essential to humans (phenylalanine, leucine, valine, isoleucine, arginine, histidine, lysine, methionine, threonine and tryptophan) can be found in pollen and most others as well, with proline being the most abundant. Many enzymes (proteins) are also present but some, like glucose oxidase which is very important in honey. have been added by the bees. This enzyme is therefore more abundant in "beebread" than in fresh pollen pellets.

Only 16 of the 31 fatty acids found in pollen had been identified by 1989 (Shawer et al. 1987 and Muniategui et al., 1989). Palmitic acid is the most important one, followed by myristic, linoleic, oleic, linolenic, stearic acids etc. Simal et al., (1988) list 7 sterols, including cholesterol. Mono-, di- and triglycerides are fairly abundant, too.

Most simple sugars in pollen pellets such as fructose, glucose and sucrose come from the nectar or honey of the field forager. The polysaccharides like callose, pectin, cellulose, lignin sporopollenin and others are predominantly pollen components. After storage in the comb the further addition of sugars and enzymes creates beebread, through lactic acid fermentation.

Table 3.1:
The average composition of dried pollen

 

Bee-collected

Hand-collected

%a

%b

%b

Water (air-dried-pollen)

7

11

10

Crude protein

20

21

20

Ash

3

3

4

Ether extracts (crude fat)

5

5

5

Carbohydrate      
Reducing sugars

36

26

3

Non-reducing sugars

1

3

8

Starch

-

3

8

Undetermined

28

29

43

a As reported by Tabio et al., 1988
b As reported by Crane, 1990

Table 3.2:
Minor components of bee collected pollen (Crane, 1990)

Flavonoids At least 8
(flavonoid pattern is characteristic for each pollen type)
Carotenoids At least 11
Vitamins C, E, B complex (including, niacin, biotin, pantothenic acid, riboflavin (B2), and pyridoxine (B6)).
Minerals Principal minerals: K, Na, Ca, Mg, P, S. Trace elements: A1, B, C1, Cu, I, Fe, Mn, Ni, Si, Ti and Zn
Terpenes  
Free animo acids All
Nucleic acids and nucleosides DNA, RNA and others
Enzymes More than 100
Growth regulators Auxins, brassins, gibberellines, kinins and growth inhibitors

 

 

a) Anarcadium sp. From honey in Guyana
Anarcadium sp. From honey in Guyana
b) Vernonia perotteti gr. (large) and Synedrella gr (small, spiny) from honey in Malawi
Vernonia perotteti gr. (large) and Synedrella gr (small, spiny) from honey in Malawi
c) Eucalyptus camaldulensis, light microscope
Eucalyptus camaldulensis, light microscope

d) Eucalyptus sp., scanning electron microscope (SEM)

Eucalyptus sp., scanning electron microscope (SEM)
e) Acerplantanoides (SEM, approx. 2600x)
Acerplantanoides (SEM, approx. 2600x)
f) Centaurea cyanus (freeze sectioned, SEM approx 2400x) showing thick pollen wall)
Centaurea cyanus (freeze sectioned, SEM approx 2400x) showing thick pollen wall)
Figure 3.4: Pollen grains of various species. Photos courtesy of (a) L. Persano Oddo; (b and c) G. Ricciardelli d'Albore from Persano Oddo et al., (1988); (d) F. Intoppa; (e and f) S. Nilsson from Nilsson et al., (1977).


3.4 The physiological effects of pollen

3.4.1 Unconfirmed circumstantial evidence

The effects and benefits derived from pollen consumption, according to some of the non-scientific literature on the subject are endless. Many people report improvement of sometimes chronic problems. Most of the major ailments reported to improve with pollen preparations are listed in Table 3.3. However, one should be aware that the benefits reported are not usually from scientific studies but are merely personal experiences without any medical or other scientific investigation of claims. Sometimes the disappearance of symptoms was witnessed by physicians, but the reasons for such cures were not confirmed through further investigations.

Table 3.3:
Non-scientific claims and reports of benefits, cures or improvements derived
from the use or consumption of bee-collected pollen.

Improvements

Cures of benefits

Athletic preformance Cancer in animals
Digestive assimilation Colds
Rejuvenation Acne
General vitality Male sterilitya
Skin vitality Anaemiab
Appetiteb High blood pressureb
Haemoglobin contentb Nervous and endocrine disordersb
Sexual prowess Ulcers
Performances (of a race horse)  

a Ridi et al., 1960
b Sharma and Singh, 1980

3.4.2 Scientific evidence

The only long-term observations on the medicinal effect of pollen are related to prostate problems and allergies. Several decades of observations in Western European countries and a few clinical tests have shown pollen to be effective in treating prostate problems ranging from infections and swelling to cancer (Denis, 1966 and Ask-Upmark, 1967).

Supplementation of animal diets with pollen has shown positive weight gain and other beneficial effects for piglets, calves, broiler chickens and laboratory cultures of insect (see 3.5.2).

Certain bacteriostatic effects have been demonstrated (Chauvin et al, 1952) but this is attributed to the addition of glucose oxidase (the same enzyme responsible for most antibacterial action in honey) by the honeybee when it mixes regurgitated honey or nectar with the pollen (Dustmann and Gunst, 1982). Therefore, this activity varies between pollen pellets and is much higher in beebread. A very slight antibacterial effect can also be detected in pollen collected by hand (Lavie, 1968).

There is some evidence that ingested pollen can protect animals as well as humans against the adverse effects of x-ray radiation treatments (Wang et al., 1984; Hernuss et al., 1975, as cited in Schmidt and Buchmann, 1992).

3.5 The uses of pollen today

3.5.1 As medicine

In order to desensitize allergic patients, pollen is usually collected directly from the plants, to allow proper identification and purity. A pollen extract is then injected subcutaneously. Desensitization through ingestion of pollen is claimed, but has not received any scientific confirmation.

For treatment of various prostate problems, pollen is usually prescribed in its dry pellet form as collected by the bees. Pollen from different countries or regions seems to work equally well. However, pollen has not been officially recognized as a medicinal drug.

Since the consumption of pollen appears to improve the general condition and food conversion rate in animals as well as people, its support in accompanying other cures should be solicited more frequently. There may be other medicinal uses in traditional medicine which, however, have not been published in readily accessible journals.

3.5.2 As food

The major use of pollen today is as a food or, more correctly, as a food supplement (see Figure 3.5). As stated earlier its likely value as a food for humans is frequently overstated and has never been proven in controlled experiments. That it is not a perfect food, as stated on many advertisements, food packages and even in various non-scientific publications should be obvious. Its low content or absence of the fat soluble vitamins should be sufficient scientific evidence. This does not mean that its consumption may not be beneficial, as has been shown scientifically with various animal diets.

Pollen has been added to diets for domestic animals and laboratory insects resulting in improvements of health, growth and food conversion rates (Crane, 1990; Schmidt and Buchmann, 1992). Chickens exhibited improved food conversion efficiency with the addition of only 2.5% pollen to a balanced diet (Costantini & Ricciardelli d'Albore, 1971) as did piglets (Salajan, 1970). Beekeepers too, feed their colonies with pure pollen, pollen supplements or pollen substitutes (see 3.11.6) during periods with limited natural pollen sources. The relatively high cost of pollen suggests the need for a detailed feasibility analysis of pollen as food additive or supplement.

Only a good mixture of different species of pollen can provide the average values mentioned in the tables describing the composition of pollen. The real value of diversity of pollen content, however, lies in the balance of these nutrients and the synergistic effect of the diversity as well as more subtle effects or characteristics related to their origin rather than their quantitative presence. Those very subtle characteristics and sensitive compounds are easily lost with improper storage and processing, something to carefully watch when making or buying quality products containing "bee" pollen.

The stimulative effect of pollen and its possible improvement of food conversion in humans as well as animals, should be of particular interest to those who have an unbalanced or deficient diet. There are no hard scientific data to back up this information, but a detailed study might show tremendous potential benefit to a very large portion of human society. The only serious problem with incorporating pollen in foods like candy bars, sweets, desserts, breakfast cereals, tablets and even honey is the widespread allergic susceptibility of people to pollen from a wide variety of species (see 3.10).

Beebread

Traditional beekeeping cultures with honeybees or stingless bees, usually appreciate the stored pollen, i.e. beebread (see Figure 3.6). Its characteristic sour taste together with brood and honey is a delicacy consumed directly during harvesting. The pollen stored by honeybees undergoes a lactic acid fermentation and is thus preserved. This final storage product is called beebread. As also mentioned in Chapter 8, these beebread combs may be sold directly but a recipe in 3.12.2 describes the preparation of fermented pollen in a similar way. This improves the nutritional value of pollen and avoids the need for freezing.

Natural and homemade beebread will keep for a considerable time and can easily be transported to the market and served - even in small quantities - as an excellent source of otherwise scarcely available nutrients. It can be sold clean and by itself or immersed in honey to make it more attractive in taste. Small pieces of comb can thus be sold or given away as candy.

The nutritional value of beebread is much higher in places where limited food variety or quantity create nutrient imbalances. It is particularly children who might benefit the most from regular pollen supplements in their diets.

3.5.3 In cosmetics

Pollen has only recently been included in some cosmetic preparations with claims of rejuvenating and nourishing effects for the skin. The effectiveness has not been proven, but there is a considerable allergy risk for a large percentage of the population. Therefore this practice is not very advisable since it excludes a large proportion of potential customers and puts others at risk of having or developing very unpleasant allergic reactions.

Including alcoholic or aqueous pollen extracts (see 3.11.1) in cosmetic formulations appears to cause no or only rare allergic reactions. While little is known about the effectiveness of such extracts, they are still the preferred method of preparation for formulations in the cosmetic industry. 

 Beebread, fermented pollen, is stored in open cells (lighter cells).
Figure 3.6: Beebread, fermented pollen, is stored in open cells (lighter cells). Usually it is found near or on the brood combs, between honey and brood. Harvesting usually destroys the associated brood and comb.


3.5.4 For pollination

Hand and bee-collected pollen have been used for mechanical or hand pollination. The viability of hand-collected pollen can be maintained for a few weeks or months by frozen storage. Bee-collected pollen however, starts losing its viability after a few hours and increasingly with age. It is believed that some of the enzymes added by bees during foraging inhibit the pollen's ability to germinate on the flower stigma (Johansen, 1955, and Lukoschus and Keularts, 1968). Large-scale applications with mechanical dusters or by using dusted honeybees for dispersion were only moderately successful.

3.5.5 For pollution monitoring

Since the 1980's, experiments have shown that pollen collected by honeybees reflects environmental pollution levels when examined for metals, heavy metals and radioactivity, (Free et al., 1983; Crane, 1984 and Bromenshenk et al., 1985). Contaminants can be quantified and sampling may be cheaper than most standard methods currently in use. Attempts have also been made to use pollen-collecting honeybees for the identification of potential mining areas (Lilley, 1983). The same effect of accumulating aerial deposits and selective plant secretions of minerals beneficial when used to monitor pollution control becomes a hazard if pollen from heavily polluted areas is used for human or animal consumption.

3.6 Pollen collection

Extreme care should be taken that pollen is not contaminated by bees collecting from flowers treated with pesticides. During, and for several days or weeks after treatment of fields or forests in an area of several square kilometres (in a circle of at least 3-4 2 km diametre) around the apiary, no pollen should be collected. This is independent of the method of pesticide application. Even systemic pesticides have been shown to concentrate in pollen of, for example coconut (Rai et al., 1977). Since a pollen pellet is collected from many flowers, even small quantities of pesticides per flower can be accumulated rapidly to reach significant concentrations.

Though pollen pellets are collected before they enter the hive, treatment of colonies for bee diseases, can contaminate the pollen pellets. Though, for example, cleaning of debris from the hive and bees regurgitating syrup, nectar or honey during collection of the pellets.

Pollen pellets are removed from the bees before they enter the hive. There are many designs of pollen traps (see Figures 3.7 to 3.8) some easier to clean and harvest, others more efficient or easier to install. The efficiency rarely exceeds 50%, i.e. less than 50% of the returning foragers loose their pollen pellets. Bees are ingenious in finding ways to avoid losing their pellets, like small holes or uneven screens and may even rob pollen from the collecting trays, if access is possible. Under some circumstances, pollen collection methods and regimes may interfere with normal colony growth or honey production. Therefore, standard beekeeping manuals should be consulted for the timing of collections (Dadant, 1992).

Pollen should be collected daily in humid climates but less frequently in drier climates. To avoid deterioration of the pollen and growth of bacteria, moulds and insect larvae, pollen should be dried quickly. Ants can remove considerable amounts from pollen traps. Krell (personal observations) reports that losses can be up to 30% in temperate climates.

Pollen needs to be dried to less than 10% moisture content (preferably 5 % or 8% according to some laws) as soon as possible after harvesting. A simple method uses a regular light bulb (wE and 1 1OV or 20W and 220V) suspended high enough above a pollen carton or tray so that the pollen does not heat to more than 40 or 45 0C. For solar drying, the pollen itself should be covered to avoid direct sunlight and overheating.

After drying, the pollen needs to be cleaned of all foreign matter. A tubular tumbler made out of a wire mash with a fan can clean considerable quantities of pollen pellets. Simpler winning methods can be used too. Benson (1984, in English) and Marcos (1991, in French) give very good accounts on trapping and subsequent processing of pollen.

Most types of pollen traps are currently only fitted to standard frame hives. are fitted to traditional log, clay or straw hives, small modifications are necessary.

Beebread is usually found on brood combs or combs near the brood nest. Available quantities are normally very small and inadvertently the brood comb and sometimes the whole colony are destroyed during harvest. A team of Russian scientists described a nondestructive means of extracting beebread from combs, harvesting 300-600 kg per year from 1500 colonies (Nakrashevich et al., 1988).

Some races of bees will store large quantities of beebread when colonies have become queenless, or the brood nest and/or plenty super space, are above an empty box with combs. Such manipulations will be more difficult or impossible with most traditional bee hives but modifications may be worthwhile. As mentioned earlier, beebread can also be made at home from bee-collected pollen(see section 3.12.2).

Other social bees usually store their pollen in special containers separate from the brood combs. These "pollen pots" can therefore be harvested without destroying the nest, but caution is necessary not to deplete the food sources completely.

3.7 Pollen buying

Quality control of pollen is difficult and under most circumstances impossible. It is therefore very important that the buyer knows the supplier well and can trust him. A reliable supplier should have all necessary storage and processing facilities and use them. Furthermore the production area, not only the residence or processing centre, should be free of agrochemicals and industrial pollution (and chemical treatments of the colonies). There are less and less of these regions in industrialized countries and a vast array and quantity of agrochemicals are now being used even in developing countries. More remote zones have problems with proper storage and transport and may require special collection and storage centres.

a)
Figure a) Pollen trap design to fit into a hive entrance between the bottom board and the brood chamber.

b)
Figure b)The screen through which the bees have to pass can be made of a thick plastic sheet (at least 3 mm) with holes of 4.7 mm diameter for European honey bees and of 4.2 mm diameter for smaller bees such as from African races. Two wire screens with holes of similar size can also be used, spaced 4 to 7 mm apart.

Figure 3.7: a) Pollen trap design to fit into a hive entrance between the bottom board and the brood chamber. b) The screen through which the bees have to pass can be made of a thick plastic sheet (at least 3 mm) with holes of 4.7 mm diameter for European honey bees and of 4.2 mm diameter for smaller bees such as from African races. Two wire screens with holes of similar size can also be used, spaced 4 to 7 mm apart.


Sometimes, unethical, deceptive marketing or ignorance prevents consumers or buyers to be informed about the above conditions. Until reliable tests have been developed and legal requirements force more frequent testing only responsible producers can be relied upon.

Buying processed products requires similar caution. The processor has to use gentle processing procedures to maintain those subtle qualities of pollen, which earned it its collected during four days. This type of trap is placed between bottom board and brood reputation. The buyer, whether consumer, retailer or processor has to be very careful and pay considerable attention to all handling and processing from the field collection to the final product. A truthful label could describe all the essential steps taken in order to guarantee the quality of the product. The need for highly ethical behaviour and knowledge at all levels is a requirement to be considered seriously, by anyone starting in this business, be it producer, processor or distributor. Forming a self-controlling organization, which certifies and controls producers and manufacturers may be useful or necessary to minimise fraud or avoid unreliable quality.

Pollen tray of a modified OAC trap (Waller, 1980) with two types of pollen chamber permitting better ventilation and pollen removal without disturbance of the colony. Returning foragers are forced to crawl through a double screen of 5-mesh wire (5 wires per inch) with 4-7 mm distance between screens.
Figure 3.8: Pollen tray of a modified OAC trap (Waller, 1980) with two types of pollen chamber permitting better ventilation and pollen removal without disturbance of the colony. Returning foragers are forced to crawl through a double screen of 5-mesh wire (5 wires per inch) with 4-7 mm distance between screens.

3.8 Storage

Pollen, like other protein rich foods, loses its nutritional value rapidly when stored incorrectly. Fresh pollen stored at room temperature loses its quality within a few days. Fresh pollen stored in a freezer loses much of its nutritive value after one year. Longer, improper storage leads to the loss of a few particular amino acids, which cause deficiencies in brood rearing (Dietz, 1975). When dried to less than 10% (preferably 5%) moisture content at less than 45C and stored out of direct sunlight, pollen can be kept at room temperature for a several months. The same pollen may be refrigerated at 5C for at least a year or frozen to 15C for many years without quality loss as tested by feeding to honeybee colonies and recording brood rearing rate (Dietz and Stephenson 1975 and 1980).

Since sunlight, i.e. UV radiation, destroys the nutrient value of pollen, other more subtle characteristics probably suffer worse damage. Storage of dry pollen in dark glass containers, or in dark cool places, is therefore a requirement.

3.9 Quality control

Only a few countries, such as Switzerland and Argentina, have legally recognized pollen as a food additive and established official quality standards and limits. Though sold in many health food stores, pollen is not considered an additive by the US FDA (Food and Drug Administration) and it does not have to comply with special standards. It is, however in the producer's own best interest to maintain the highest standards of cleanliness for his product.

The Argentinean standards require microbiological characteristics of not more than 1SOx1O0UFC/g aerobic microbes, 1O0UFC/g fungi and no pathologic microorganisms. The moisture content should not exceed 8% (controlled by vacuum drying at 45 mm Hg and 650C). Other limits include a pH of 4-6, protein content of 15-28% Kjeldahl (N x 6.25) of dry weight, total hydrocarbons of 45-55 % of dry weight and a maximum ash content of 4% of dry weight (determined at 600 0C).

Pollen used for cosmetic purposes should have the same, if not a better quality than that destined for consumption as food. The first quality control is assessment of gross contamination with foreign substances, i.e., parts of bee and hive debris. Further controls might include measurement of moisture content and a bacterial count. Determination of various agrochemicals, including drugs used inside bee colonies are possible and may be required in some circumstances. These analyses require sensitive, expensive chromatographic equipment.

Since air pollutants and agro-chemicals have been shown to accumulate in pollen collected by bees (see 3.5.5) pollen should originate from unpolluted areas with the lowest chance of contamination by agrochemicals, industrial pollutants and drugs applied by beekeepers. Producers from such areas should make particular note of this in their advertising.

Degradation of pollen nutrients by inadequate collection, drying and storage can only be tested by bioassay, i.e. feeding pollen to honeybee colonies and observing the quantity of brood reared, which is a very lengthy and laborious process. Therefore, only reliable primary products who have the required knowledge and facilities should be considered as supplies.

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