Plant Foods for Human Nutrition 59: 129–132, 2004. C 2004 Springer Science+Business Media, Inc.
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Quality Evaluation of Honey Harvested From Selected Areas in Tanzania With Special Emphasis on Hydroxymethyl Furfural (HMF) Levels ANDREW B. GIDAMIS,1 BERNARD E. CHOVE,2,∗ NICHOLAS B. SHAYO,2 SIPHUEL A. NNKO2 & NICHOLAS T. BANGU3 1 African
Institute for Capacity Development (AICAD), P.O. Box 46179, GPO 00100, Nairobi, Kenya; 2 Department of Food Science and Technology, Sokoine University of Agriculture, P.O. Box 3006, Chuo Kikuu, Morogoro, Tanzania; 3 Tumaini University, P.O. Box 200, Iringa, Tanzania (∗ author for correspondence; e-mail:
[email protected] or
[email protected])
Abstract. The physicochemical properties of honey harvested from popular honey-producing areas in Tanzania were investigated. Honey from Shibe-Dodoma had the highest values of specific gravity, total acidity, free fatty acid content, diastatic number, overall acceptability, and lowest hydroxymethyl-furfural (HMF) level as compared to honey samples from other areas. There was no significant difference ( p > 0.05) in terms of HMF in the other honey samples from Tanga, Morogoro, Same, Arusha, and Tabora. HMF levels in all honey samples were far below the maximum acceptable level of 40 mg/kg as recommended by the Codex Alimentarius Commission Standards before storage for 6 months. No traces of streptomycin and phenol were detected in all honey samples. It was concluded that according to the values of the studied quality parameters, the types of Tanzanian honey obtained from the popular honey producing areas may be judged to be of high quality. Key words: Apis dorsate, Apis mellifica, bee honey, diastatic number, honey quality, hydroxymethyl-furfural (HMF)
Introduction Honey is the natural food of the honeybees, Apis mellifica and Apis dorsata. Honey is the nectar and saccharine exudation of plants gathered, modified, and stored in combs by honeybees [1]. The composition and properties of honey is dependent on floral origins utilized by the bees and the climatic conditions of the area from which honey is harvested [2, 3]. Honey is a complex mixture, mainly composed of water, sugars (glucose, fructose, saccharose, maltose, higher sugars), gluconic acid, lactone, nitrogenous compounds, minerals, and some vitamins [4]. Case studies on physical and chemical properties of the types of honey produced in different countries have been reported by many scientists [1, 5–7]. Tanzanian honey can be described as either being monoflora or polyflora depending on geographical location. In this respect a lot of variations in its physicochemical properties is to be expected. Honey undergoes changes during storage, leading to darkening and loss of aroma and flavour [8]. It is therefore important to monitor its quality attributes from time to time. Hydroxymethyl-furfural (HMF) is a cyclic aldehyde that is produced by degradation of sugars [4]. HMF and diastatic number have been widely used both to predict honey freshness and to evaluate its quality upon treatments such as overheating, storage abuse, and adulteration with syrup [9].
The present study was undertaken to investigate the physicochemical properties of honey obtained from most popular honey-producing areas in Tanzania. Materials and Methods Sample Collection The fresh ripe honey samples were collected from beekeepers in Central (Tabora and Shibe-Dodoma), Eastern (Tanga and Morogoro), and Northern Tanzania (Same and Arusha). These areas are regarded as the most popular honey-producing areas in the country. The vegetation in these areas can be described as being composed of a mixture of various natural plants, making the honey to be mostly of polyflora in nature. Extraction The extraction of honey was carried out by filtering and squeezing the honey through muslin cloth. It was stored in airtight dark plastic jars for analysis. The extracted honey was then heated to 60 ◦ C for 30 min [10]. The heating procedure after extraction is also practiced by beekeepers in harvesting honey. It also facilitates the separation of any beeswax remaining in the extracted honey. Analysis The physicochemical properties of collected honey samples assessed include specific gravity, total suspended colloids, HMF, total acidity, free fatty acids, diastase activity, pH, color, moisture, and general acceptability. The levels of phenol and streptomycin were also assessed. The specific gravity of honey and colloids were determined as described by Singh and Bath [1]. Total acidity was quantified by volumetry, titrating a honey sample against a 0.1 M NaOH solution and expressing the result in milliequivalents of acid at 100 g of honey; color was quantified by optical density measurements, and moisture by refractometry. HMF and diastastic number were determined by spectrophotometry
130 Table 1. Physical properties and acceptability of honey samples harvested from different areas Geographical origin of honey
Specific gravity (g cm−3)
Suspended colloids (mg/100 g)
Diastatic number
Moisture (%)
Color (OD) at 420 nm
Acceptability
Tanga Arusha Same Tabora Shibe-Dodoma Morogoro
1.43a 1.40a 1.45b 1.42a 1.52c 1.41a
100a 100a 200b 150b 200b 100a
22.8b 22.2a 23.3b 22.6a 32.6c 22.1a
22.7b 22.6b 22.6b 22.8b 21.6a 22.7b
1.6a 1.6a 1.6a 1.7b 2.0b 1.6a
7.0b 6.2a 7.6c 6.7b 8.2c 6.2a
Note. Data in the same column followed by identical superscript do not differ significantly ( p < 0.05). High-ranked letters are significantly different from lower ones in this order c > b > a. (n = 5).
using the methods suggested by Ramirez Cervantes et al. [4], as described in the A.O.A.C. [11]. Organoleptic assessment of honey samples was conducted by a team of eight food scientists using a 9-point hedonic scale testing for taste, flavor, color, and mouth feel. Average of scores for attributes was reported as overall acceptability [12]. In all cases the experiment was carried out in triplicate and the data obtained was analyzed using Minitab Statistical Software [13]. Results and Discussion Table 1 contains the physical properties of the honey samples collected from the areas. Physical properties analyzed include specific gravity (1.40–1.52 g cm−3 ), suspended colloids (100–200 mg/100 g), diastatic number (22.1–32.6), moisture (21.6–22.8% wet basis), color at 420 nm (1.6– 2.0 OD), and acceptability (6.2–8.2). In Table 2 chemical properties of honey samples are given. The chemical analyses included total acidity (29.1– 41.6 meq/kg), pH (4.2–4.87), streptomycin was not detectable (ND), free fatty acid (10.6–26.6 meq/kg), and phenol was not detectable (ND). Figure 1 indicates levels of HMF in different samples of honey stored over a period of 7 months. Honey samples were Table 2. Chemical properties of honey samples collected from different areas
Geographical origin of honey
Total acidity (meq/kg) pH
Free fatty Streptomycin acid Phenol (meq/kg) (meq/kg) (%)
Tanga Same Arusha Tabora Shibe-Dodoma Morogoro
41.6c 33.8b 34.4b 32.4b 29.1a 31.5a
ND ND ND ND ND ND
4.20a 4.63b 4.41b 4.72c 4.87c 4.40b
10.6a 14.2a 10.4a 14.5b 26.6c 10.8a
ND ND ND ND ND ND
Note. Data in the same column followed by identical superscript do not differ significantly ( p < 0.05). High-ranked letters are significantly different from lower ones in this order c > b > a. (n = 5). ND = Not Detectable.
kept in a room with average temperature of 28 ◦ C. Overall, there was gradual increase in HMF levels with time with Tabora sample reaching the highest level of over 40 mg/kg. Honey from Shibe-Dodoma showed the highest specific gravity and diastic number of 1.52 g cm−3 and 32.6, respectively, followed by 1.45 g cm−3 and 23.3 of honey from Same and 1.43 g cm−3 and 22.8 of honey from Tanga (Table 1). The variation observed in specific gravity may be due to differences in moisture contents. Variation in the diastase activity may be related to source of honey as well as the climatic conditions in the areas. Honeys produced from warmer climates have been reported to have naturally low levels of diastase activity [9, 14]. Moisture contents of honey samples analyzed varied from 21.6% in ShibeDodoma sample to 22.8% in Tabora sample (Table 1). These values are higher than the range of 13.4–18.2% reported in Indian honey [15], and 20% recommended by the Council of the European Union directive [16]. The moisture contents of honey showed to have a direct correlation to specific gravity. The honey samples having higher moisture content had lower specific gravity and vice versa. Similar observations were made by other authors [1, 17]. It was further observed that the moisture content of honey is an important factor contributing to honey stability against fermentation and granulation during storage [1]. In terms of color and suspended colloids, the ShibeDodoma honey showed the highest color measured as OD at 420 nm. The color of honey and its colloids is known to affect its general acceptability. The data for organoleptic evaluation showed a significant variation ( p < 0.05) in honey samples from different areas. The Shibe-Dodoma sample showed highest overall acceptability scores of 8.2, followed by 7.6 for Same, and 7.0 for Tanga samples (Table 1). These results show that low HMF values, high specific gravity, and high optical density increased the general acceptability of honey. Total acidity of honey samples obtained from Tanga was significantly higher ( p < 0.05) than the samples from other areas. Total acidity values of honey samples from Same, Arusha, Tabora, Shibe-Dodoma, and Morogoro did not differ significantly ( p < 0.05) (Table 2). Honey sample from
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Figure 1. Levels of hydroxymethylfurfural (HMF) in miligram per kilogram during storage at 28 ◦ C.
Shibe-Dodoma had the highest free fatty acid content of 26.6 meq/kg against lowest value of 10.4 meq/kg in the Arusha sample. Lower values were of 10.6 meq/kg and 10.8 meq/kg were also obtained for Tanga and Morogoro samples respectively. The acidity of honey is attributed to the presence of organic acids, particularly the gluconic acid, which is found in equilibrium with their lactones or esters and inorganic ions such as phosphates and chlorides [18]. These constituents contribute to the variation in acidity amongst different types of honey. It is reported that total acidity was found to be higher in cotton honey than clover, which indicate the influence of floral types in total acidity [7]. In all honey samples, no traces of streptomycin as an antibiotic and phenol were detected (Table 2). This may be due to the fact that the beekeepers in the areas were keeping bees naturally without any treatment of using antibiotics and that the hives are located in isolated areas far from residential areas. The initial HMF content (Figure 1) in all honey samples was lower than the allowed maximum limit of 40 mg/kg as recommended by Codex Alimentarius [19], and Council of the European Union directive [16], for honey in general. These results contradict the observation made by some authors that the types of honey produced in subtropical climates have high HMF exceeding 40 mg/kg [14]. However, the European Union council directive also allows for a maximum of 80 mg/kg for honey from tropical climates. The HMF level in honey is said to depend on the type of sugar present in honey and the fructose: glucose ratio [20]. The
HMF formation results from the acid catalyzed dehydration of hexose sugars with fructose being particularly susceptible. Fructose has been reported to be unstable at pH 4.6 and is five times more reactive than glucose [21]. Low levels of initial HMF observed in all honey samples may also be attributed to low pH values, ranging from 4.20–4.87 (Table 2). Upon storage for up to 7 months at 28 ◦ C, the HMF in all honey samples increased progressively with Shibe-Dodoma sample showing the least HMF level (Figure 1). With the exception of Shibe-Dodoma sample, all other honey samples were either very close or have exceeded the maximum allowed level of HMF of 40 mg/kg in the new European Council draft. However, the new Codex Alimentarius draft specifies a 60 mg/kg limit [22]. This is a clear indication that at such a high storage temperature, honey should not be kept for more than 6 months. It could be concluded that the honey produced in the popular honey-producing areas in Tanzania is of acceptable quality standards as most of the quality parameters fall within the recommended limits. The storage temperature of honey should be carefully controlled to preserve its quality. At its best, honey should be consumed within 6 months following its harvesting. Acknowledgments The authors are indebted to Sokoine University of Agriculture for the financial support and to the beekeepers for providing honey samples.
132 References 1. Singh N, Bath PK (1997) Quality evaluation of different types of Indian honey. Food Chem 58(1): 129–133. 2. Anass T, Diez MJ, Heredia, JF (2003) Palynological, physicochemical and color characterization of Moroccan honeys: III. Other unifloral honey types. Int J Food Sci Technol 38(4): 395–402. 3. Perez-Arquillue C, Concello P, Arino A, Juan J, Herresa A (1994) Quality evaluation of Spanish rosemary (Rosomarimus officinalis) honey. Food Chem 51: 207–210. 4. Ramirez Cervantes MA, Gonz´alez Novelo SA, Sauri Duch E (2000) Effect of the temporary thermic treatment of honey on variation of the quality of the same during storage. Apiacta 35(4): 162–170. 5. Kamal A, Raza S, Rashid N, Hameed T, Gilani M, Quaresh A, Nasim K (2002) Comparative study of Honey collected from different Flora of Pakistan. OnLine J Biol Sci 2(9): 626–627. 6. Gupta JK, Kaushik R, Josh VK (1992) Influence of different treatments, storage temperature and period on some physico-chemical characteristics and sensory quality of Indian honey. J Food Sci Technol 29: 84–8. 7. El-Sherbiny GA, Rizk SS (1979) Chemical composition of both clovers and cotton honey produced in A.R.E. Egypt. J Food Sci 7: 69–75. 8. Samko MT, Minafequi S, Huidobro JF, Lozano JS (1992) Aging of Honey. J Agric Food Chem 40: 134–138. 9. Karabournioti S, Zervalaki P (2001) The effect of heating on honey HMF and invertase. Apiacta 36(4): 177–181. 10. Vinas P, Campillo N, Cordoba H, Candela ME (1992). Simultaneous liquid chromatographic analysis of 5-(hydroxymethyl)-2furaldehyde and methyl anthranitate in honey. Food Chem 44: 67– 72.
11. AOAC (1995) Official Methods of Analysis, 16th edn. Arlington, VA. Association of Official Analytical Chemists. 12. Larmond E. (1977) Laboratory Methods for Sensory Evaluation of Foods. Publication 1637. Ottawa, Canada. Canada Department of Agriculture, pp. 57–59. 13. Minitab Inc. (2000) Minitab 13 for Windows (Version 13.2). State College, Pennsylvania. 14. Lagrange V, Sanders SW (1988) Honey in cereal-based new food products, Cereal Foods World 33: 833–838. 15. Abu-Tarboush HM, Kahtani HA, El-Sarrange MS (1993) Floral types identification and quality evaluation of some hone types. Food Chem 46: 13–17. 16. The Council of the European Union (2002) Council Directive 2001/110/EC of December 2001 relating to honey. Off J Eur Communities L10/47–52. 17. Rodriguez-Otero JL, Pasero P, Simal J, Cepeda A (1994) Mineral content of the honeys produced in Galicia (North-West Spain). Food Chem 51: 169–171. 18. Echigo T, Takenaka T (1974) Production of organic acids in honey by honey bees. Agricultural Chem Soc Japan 48: 225–230. 19. Codex Alimentarius Commission Standards (1981) Codex Standards for sugars, Standard 12-1981. Codex Standard for honey (European Regional Standards) Vol III. FAO, Rome. 20. Doner LW (1977) The sugars of honey; A review. J Sci Food and Agric 28: 443–456. 21. Lee HS, Nagy S (1990) Relative reactivities of sugars in the formation of 5-hydroxymethy furfural. J Food Process Preservation 14: 121– 178. 22. Honey Quality and International Standards (1998) Review by the International Honey Commission, Draft CL 1998/12-S of the Codex Alimentarius and Draft 96/0114 (CNS) of the EU.
