Honey evolves from nectar, which is the sweet sap and sugar substance rich in fructose, collected and con­

densed by the bee (Avis Mellifea) from the nectarines of flowering plants, and which it deposits in the honey comb. Factors evolved in the transformation of this nectar into honey have been the subject of study (1). The product is a thick, syrupy translucent pale yellowish or yellowish/brown liquid, of sweet taste and pleasant odour. It is also sometimes referred to as Mel, Ceramel, Hydromel and Oxymel, and was a precious commodity in early Roman, Greek and Egyptian civilizations, and for people 2000/4000 years ago it was the main source of sugar. It has been referred to as a folkloric ingredient, and its name, honey, is often used on labels of products because of its association with delightfulness. A number of general reviews of the product have appeared in the general technical press (2) and several books have been published on the material (3), reviewing the composition, physiological action, nutritional and theraputic value and toxicity (4). An international defini­tion of honey was published some years ago and data regarding its chemical composition (5). The determina­tion of the botanical source of a given sample of honey usually depends primarily on the identification of the principal portion of the pollen spectrum, assisted by its colour and free acid content (6). Honey varies greatly in flavour owing to the different flowers upon which the bee feeds, but chemically there is little variation, but where honey contains more than 8% sucrose it is an indication that the bees have been fed on sugar (7), and methods have in fact been published for determining if honey is pure nectar honey or from sugar fed bees (8).

The Extraction & Purification of Honey Most honey is extracted from the honeycomb by centri-fuging or by procedures employing pressure (9). Purifi­cation and refining procedures have been evolved (10), including ultraf i l trat ion and electrodialysis (11), although a simple purification of honey can be achieved by melting the crude material at not more than 80°C and allowing to stand, the impurities rising to the surface to be skimmed off and the liquid diluted with water until the product has a density of 1.355 @ 20°C.

Refining honey to improve flavour of (U.S.A.) honeys with objectionable flavours e.g. buckfast, buckwheat, fa l l f lower, horsemint , clover-heartsease and sweetweed has been carried out (12).

Clarification of honey has been carried out using filters and filter aids (13) and removal of colloidal con­stituents has been obtained by the use of ultrafiltera-tion (14). It has been found that the commercial clarifi­cation of honey can decrese the thismin, riboflavine, pantothenic acid, nicotine acid, and ascorbic acid contents of so treated material (15). Improvements in the colour (and odour) in honey has been brought about by the treatment with activated carbon and by treatment with kieselguhr (16). Crude honey has also been decolourized by blending ten kilograms of the product with half a kilogram of paraffin wax, of melting point 60°C, and keeping the blend at 70/75°C for three hours, the lower layer being the refined material (17). Honey has also been bleached using bleaching carbons (18). Cobalt y — irradiation of honey has been used to sterilize the material (19).

The Storage & Packaging of Honey Studies have been carried out on the effects of storage on honey (20), including chemical effects (21), and the effects of storage for two years at 140°C and at 20°C (22). Data has been produced on the influence of tem­perature, time and storage in light on the activity of invertase and inhibine of honey (23), and it has been established that changes do occur in the composition and biochemical activity when the material is stored even at 26 ± 3° there can be a conversion of about 9% per year of monosacharides to the more complex dis-acharides and high sugar and also that there is an inrease in the fructose to glucose ratio (24). Honey which is required to remain liquid for three or four months can be improved in its storage properties by heating to 60°C for 4/6 hrs or at 65°C for 2/4 hrs (25). The storage life of honey has also been improved by includ-

HON ITS PROPERTIE

PAR by EDGAR SCO

ing sorbic acid in it immediately after extraction and then treating with ultrasonic waves, or by chilling to ( - ) 40°F and storing at this temperature (26). Honey can be very slightly acidic and care is advocated in packing in metal, only lacquered tins being advisable. Honey Powder In a continuous process for dehydrating honey, the material, @ 128°F, containing 30 ppm food grade sili­cone anti-foam has been dehydrated under 27 inches vacuum in a mechanically agitated thin film evaporator @ 240°F, and the nearly anhydrous molten product is fed to a pair of chilled (35°F) steel rolls and squeezed and cooled to a thin brittle sheet which is removed in small pieces and ground to a free flowing powder. The powder is then packed into sealed containers with a desciccant, retaining its flavour for over a year at room temperature (27). Honey has also been mixed with 10% pre-gelatinized starch, dried and ground to produce a free flowing non-hydroscopic powder (29), also a mixture of one kilogram of honey, 400 gr. starch, in 5 litres water, plus 300 grams aluminium silicate (Al2 Si O5) and 20 grams methyl cellulose has been spray dried at 110°C to give 1.4kg free flowing honey powder (29). Silica has also been used as an anti-caking agent in dehydrated honey (30). A candy-like product containing < 2% water has been prepared from honey by concen­trating it under partial vacuum @ < 85°C resulting syrup being allowed to solidify in a dry atmosphere (31). Honey has also been freeze-dried (32).

60 BRITISH FOOD JOURNAL May/June 1987

NEY ES AND USES OTT LOWER*

Artificial Honey Honey substitutes have been produced from time to time (33) and the properties of eleven samples of such material have been analysed (34), such materials usually having a base of starch syrup (35) sucrose and honey. Examples of synthetic honey consist of (A) clarified sugar (10 lbs), pure honey (3 lbs), water (3 pints), cream of tartar (1dr) essence of peppermint (10 drops) and (B) 75 parts invert sugar syrup, 10 parts malt extract syrup and 14 parts water.

Toxicity and Honey A review has been published on the toxicity to humans of substances naturally present in some honeys, as well as of honeys collected by bees from plants treated with pesticides (36) and reference has recently been made to an association of honey with infant deaths (37). Honey

not sufficiently purified has caused allergic and sensi­tising reactions in guinea pigs, but material freed of proteins does not do this (38). Ingestion of honey and pollen collected by bees from Atropa Belladonna has caused dizziness In two people and serious poisoning in another (39). A cholinergic effect from honey has been found to be due to the presence of acetylcholine (40). The effect of honey on the tonus of healthy persons has been investigated (41).

Some Components of Honey The composition of honey has been reviewed previously (42). The material consists essentially of sucrose and its hydrolysis products and is principally a concentrated solution of sugars e.g. glucose, fructose, sucrose, etc (95/99% solids) of which the main components are levulose (38%), and dextrose (31%) plus minor compo­nents (3%) and water (17/18%) (43), and the sugar contents of honeys from various flowers, fruits, etc, have been studied (44). Honeys can also contain wax, pollen grains, mould colonies, cocci and yeast cells (45), and also proteins, volatile oils and lipids etc. Organic acids found sometimes include malic, citric, succinic, acetic (46), (47) formic, phosphoric (48), tartaric (49) and boric acid (50).

Acetylcholine and choline have also been detected in some samples (51) e.g. to the extent of 0.06/5.0 mgms per 100, in American samples. Honeydew, heather flower and sugar honeys have all been found to contain

the amino acids — leucine, phenylamine, valine, tyro­sine, proline, alanine, serine, histidine, arginine, lysine, ornithine, glutamic acid and aspartic acid and occa­sionally threonine (54). The chemical composition and properties of honey from honeydew bees have been compared with flower honey and its use as a human food and manufacture has been discussed (56). Honey also contains precious flavours derived from the nectar of the flowers from which it is obtained, and these aromatic components have been identified by the use of gas chromatography (55).

Lactones have been identified (57) and trace lipids (58), and the proteins content of honey has been examined, and said to be important for estimating honey quality (59). Yeast growth in honey has also been studied (60). Provitamin A (carotene) has been separa­ted as a colouring matter how honey (61), and vitamins E12 (62), and vitamin C (63), has been found in the material.

Honey has been found to contain hydrogen peroxide (inhibine), orginating in a glucose oxidase system, and giving honey an anti-bacterial property (52) (64). (If honey is diluted with water its glucose oxidase enzyme becomes active, producing hydrogen peroxide) (80). The effect of ageing on the inhibitory substances in various honeys (i.e. inhibine) has been studied, where honey stored for a year in a dark chamber at room temperature has shown no drastic reduction in the inhibine value (anti-bacterial action) when tested on streptococcus racalis and shigella dysenterial (unless it has suffered appreciable exposure to air during storage (65). The stability of inhibine in honey under the absence of ultra­violet light has been examined (66). Hydroxymethyl furfural has been found to be a component of honey and the main volatile component where the material has a good odour (67). Honey can contain this ingredient in amounts below 1mg/100 gms, such a quantity increas­ing if the honey is heated to 45°C for 2/2½ hrs (indicat­ing that the presence of this chemical in honey does not always mean andulteration) (68). Heating honey even at low temperatures as 30/35°C can increase the hydroxy methyl furfural content, thus honey from subtropical regions may have a high hydroxylmethyl furfural con­tent naturally (69).

Major and trace amounts of various elements in honey have been noted, more than 25 of these having been found (70), e.g.

Boron (76) Calcium (oxalate) (72) Cadmium (73) Iodine (77) Lead (73) Magnesium (71) Manganese (73) (74) (75) Phosphorous (71) (75) Sodium (79) Silica (71) Potassium (79)

Boron has been found in some 100 (German) samples of honey to the extent of 0.012% (76), and iodine has been found in (Russian) honey to the extent of 20/26% per kg, dry weight (77). Sodium and potassium have been found in European, North American and Australian honeys, where they show a wide variation (78). Ash from blossom honey has given the analysis:- (79).

Potassium Oxide 30/50% Sodium Oxide 5.54/10.03% Calcium Oxide 2.12/8.00% Magnesium Oxide 1.50/2.17% Phosphorous Pertoxide 1.60/12.5%

BRITISH FOOD JOURNAL May/June 1987 61

HONEY — ITS PROPERTIES AND USE continued

The enzymes of honey have been examined (81), such materials being inactivated by heat (82). The activity of amylase (and invertase) in forty eight samples of (Polish) honey has been determined (83), and catalase has been found in some honeys, arising from pollen grains and fermentation yeasts, but it is rapidly des­troyed by heating a 50% honey solution @ 75°C (84). The activities of this enzyme (and of diastase and inver­tase) have been tabulated for 72 samples of honey from 26 plant species (85). The sugar-splitting enzyme diastase has been found in honey (86) (90b) (90c), the activity of which is said to depend on the amount of pollen present in the honey (87), and it has also been reported that its activity in honey increases as does the darkness of the honey (88). Excessive heating of honey containing diastase can destroy the enzyme (89). The enzyme invertase has also been identified in honey (90), e.g. in 100 samples (90d), and to the extent of 0.05% (91). Honey made by feeding bees with dry crystal sugar has been found to contain three times as much invertase (and twice as much diastase) as does normal natural honey (92). In enzyme/biological studies in honey it has been established that invertase undergoes a progres­sive irreversible diminuition of activity as the honey ages, with light and excessive water accelerating the process, and low temperature retarding the same (93). Phosphotases have also been isolated from honey (94). Oligosaccharides etc, that have been identified in honey, besides sucrose, include maltose (100), kozibose (99), isomaltose (98), gentiobiose, laminaribose and turmanose (95), and also arabinose (96), centose (97), and melezitose (101).

Some Chemical & Physical Properties of Honey Chemical and physical properties for honey have been investigated (102), including a suggested specification for the product after examination of some 1600 samples (Swiss) (103), and a study of 1573 different samples and from the latter the following figures being suggested as limiting requirements:-

Sucrose number : 6.5 Diastase number : 14 Hydroxymethyl-furfuraldehyde content : 1.5%

Other test figures for honey taken from the literature are:-

pH Value : 3.16/4.87 Density : 1.352/1.361 @ 20°C Specific Heat : 0.54 (with 17% water) Specific Volume : 0.691 (81.4% mgms) Ash : 0.3% (∞) 2D : : (+k)0.6/( )3.0°(@ 20°C

in a 20% w/v Solution)

ium permanganate (106), and its reaction to ultraviolet light (107). Fructose in honey can give rise to hygros-

The hygroscopicity of honey has been studied, and its electrical conductivity (105), its oxidation with potass-copicity, the material absorbing water whilst standing uncovered and during handling and packaging (109). Factors affecting the colour of honey have been consi­dered (110). The effects of heat on honey have also been determined (111), showing that if it is heated for any length of time at above 60°C, it may be slightly burnt (caramilised), and also lose some of its natural aroma and darken because of the presence of amino acids and the sugars become glucosans (112). Certain changes that can occur when honey is heated to 48°C and to 43°C, in order to melt it for can fill ing, have also been studied, by following the invertase, diastase and hyd-roxymethyl furfural contents, showing that at 48°C after 5 days the invertase and diastase values can decrease by 35/50% being unaffected at 43°C. Honey exhibits a light blue flouresence on non-flourescent paper, topped by a white zone especially when honey has a low water content and is very viscous. The viscosity and thixot-ropy of honey have been studied, some materials (ling heather and calluna) having a thixotropic nature. Study of the thixotropy of honey has shown that in some, apparent fluidity increases with shearing force (115).

Part II of this article will appear in the July/August issue

* EDGAR SCOTT LOWER

Mr E S Lower started working for Croda when the com­pany was in its infancy, in 1932, and retired at his own wish in 1974, at the age of 57.

He started work at the company's first factory in Raw-cliffe Bridge, Goole, Yorkshire as a boy of 14, when the number of employees was only seven and left when the company's workforce was over 6,000.

Edgar Lower lives in Goole, Yorkshire, England, and although he has retired from the main board of directors of Croda International he retains a connection with the company as a consultant.

He did much work of an original nature on lanolin and woolgrease derivatives, which were the main products of Croda at that time, and gradually became an internatio­nal authority on these products, re-establishing these materials as important products of commerce.

At the outbreak of the 1939-1945 war he was promoted to chief chemist at the factory and was responsible for Croda producing many entirely new products required for the war effort. After the war, Mr Lower set up Croda's first specific research laboratory at the Rawcliffe Bridge fac­tory, and was made a director of the company in 1949. He continued as a board member throughout Croda's rapid growth and at the time of his retirement was the longest serving director of the company, and had a position on the main board of directors.

During his career Dr Lower has published over 85 technical papers and many patent specifications, and in his retirement continues writing for the technical press, on a wide range of chemical products.

62 BRITISH FOOD JOURNAL May/June 1987