| Livestock Research for Rural Development 23 (9) 2011 | Notes to Authors | LRRD Newsletter | Citation of this paper |
This study was designed to evaluate different honey samples obtained from local market and beekeepers for their quality parameters at Gomma woredas, south west Ethiopia. Sixty samples were collected to evaluate their moisture, pH, acidity, ash, Estimation of Hydroxymethyl Furfural (HMF), water insoluble solids, total reducing sugar and sucrose content.
The result showed locally produced honey had moisture, ash, acid, and pH contents ranged between 15.66 to 23.45%, 0.05-0.60, 0.30 and 57.30 meq kg-1 ,3.45 and 4.18, respectively, which is within the standard limits. Similarly, the HMF and reducing sugar contents of locally produced honeys ranged from 0.05 to 17.70 mg kg-1 and 61.15 and 77.41%, respectively. The water insoluble material content of the honey samples ranged between 0.01 and 23.82 gm/100gm while the sucrose content ranged between 0.75-6.96 for the tested samples of locally produced honey. The result indicated that moisture content of honey at farmer level is increasing due to harvesting of un ripened honey and improper storage condition, which increases the hygroscopic of honey. Generally, the mean of all samples were found to be in acceptable range of international standards for all of the tested parameters except for water insoluble material indicating its potential for export with few management interventions.
Key words: composition, farmers, market
Honeybee honey contains a complex mixture of carbohydrates, mainly glucose and fructose; other sugars are present as traces, depending on floral origin. It also contains small quantities of organic acids, lactones, amino acids, minerals, vitamins, enzymes, phenolic compounds, volatile compounds, pollen, wax and pigments (Crane 1980). The contents of these components in honey are the most important quality criteria of honey and indicate some important deterministic quality properties of the honey (Sahinler and Gul 2004).
Chemical composition of honey varies depending on plant source, season and production methods. Storage conditions may also influence final composition, with the proportion of disaccharides increasing overtime (White et al 1964). Careless handling of honey can reduce its quality. Amongst the factors that most influence quality is high temperature, length of storage and moisture content greater than 21%. They lead to fermentation, high levels of Hydroxymethylfurfural (HMF), loss of enzymatic activity, changes in flavor, darkening and microbial growth (Moguel et al 2005).
As a food, honey is easily digestible and a more palatable food. It supplies substantial energy since it is 75 to 85 % fructose and glucose. Albanese et al. (1952) suggested that rapid assimilation of fructose may be associated with increased nitrogen retention and also the presence of invertase enzyme in honey is good for old and sick people. Honey also proved useful in the treatment of burns, wounds, and gastroenteritis stomach and skin ulcers because of its antibacterial properties (McCarthy 1995). Emarah et al (1997) reported the use of bee honey in the treatment of external eye disease. The variation in the composition of honey constituents is due to various physiological factors such as climate, soil, flora, bee species, etc. Such variation in composition directly or indirectly affects both the local price and difference in preference as well as export earnings of the country. However, little information is known about the quality and marketing system of honey in Ethiopian in general and Gomma woreda in particular. Therefore this research was initiated to analyze the quality of honey produced in Goma woreda, Southwestern Ethiopia.
The study was conducted from September to December 2009 at Gomma district, located in mid-altitude sub-humid zone of the south western part of Ethiopia. It is one of the administrative regions under Jimma zone of Oromiya regional national State. The rainy season extends from May to September with highest rainfall usually recorded in August. The mean annual rainfall varies between 1400 and 1650 millimeters with average maximum and minimum temperatures of 29.9 OC and 13.4 OC, respectively and the altitude is 1400 to 2270 meters above sea level (IPMS 2007).
Honey samples were obtained directly from Local market and producers in Gomma woreda. Eighteen samples of locally produced honey( 0.5 kg each) were collected from local market and were named as HS-1 through HS-18, whereas 18 samples ( 0.5 kg each) were collected from beekeeper farmer and were named HS-19 through HS-36 where HS refers to Honey Sample and the number shows the sample number. Each sample was mixed thoroughly and kept in glass containers at room temperature till final analysis was carried out.
The collected samples were analyzed at Quality Standard Authority of Ethiopia following the procedure of Codex Alimentarius Commission Standards (2001). Furthermore, analysis of total reducing sugar and sucrose content were seen at Ethiopian Health and Nutrition Research Institute (Pasteur) laboratory for its quality evaluation as shown below.
The moisture content of honey sample was estimated by determining the refractive index of the sample with the use of refractometer. The sample was directly covered on the surface of the prism evenly; after two minutes the reading of refractive index were recorded. Each sample was measured twice and averages of two readings were recorded and corresponding value for moisture content was recorded.
The pH of honey was determined by using Tashniwal digital pH meter. 10 g of honey sample was dissolved in 75 ml of distilled water in 250 ml beaker. The solution was stirred and pH electrode was immersed in the solution and pH was recorded.
Fifty ml of one percent honey sample (prepared by dissolving 2g of honey solution in 200 ml distilled water) was taken in the burette and 10 ml of Fehling A and 10 ml of Fehling B with 7 to 8 ml of distilled water was taken in 250 ml conical flask and heated until it starts boiling. 1 ml of 0.2 % of methylene blue indicator was added and titration was completed during boiling only. The change in the color of the solution from blue to colorless was taken as the end point of the reaction.
The percentage of T.R.S was calculated by the following formula:
Where:
Glucose factor = 10.2
Ten milliliter of 6.34 N brick solution (56 ml of hydrochloric acid was dissolved in 100 ml of distilled water) and 50 ml of one percent honey was taken in conical flask and kept in water bath at 60 OC for about 20 to 30 minutes. Then the sample was cooled and neutralized by adding sodium hydroxide solution. Neutralization of the solution was confirmed by using litmus paper and the sample was taken in a burette. Ten milliliter of Fehling A, 10 ml of Fehling B and 7 - 8 ml of distilled water was taken in a 250 ml conical flask and heated till it starts boiling. After boiling, 1 ml of 0.2 % of methylene blue indicator was added to the flask. The titration was completed while the solution is boiling. The end point of the reaction was recorded as the blue color changed to colorless.
The percentage of TRS was calculated by the following formula.
Where, Glucose factor = 10.2
T.V = Titer value
The percentage of sucrose was worked out as follows:
Sucrose (%) = TRS after inversion – TRS before inversion x 0.95.
Where: 0.95 = Constant
Ten grams of honey was weighed with the help of electronic balance and poured in conical flask and 75 ml of distilled water was added by rinsing the utensil. The solution is titrated against 0.1 N NaOH solutions in burette using phenolphthalein as indicator. The titration was carried out till the solution turns to pink from colorless. The acidity was determined by using the formula:
Two grams of honey were weighed and taken in a silica crucible and 3-4 drops of olive oil were added to avoid fluttering and kept in muffle furnace at 600 OC for 3-4 hours. The weight of the ash was determined by deducting the weight of empty crucible from the total weight of empty crucible and ash. The percentage of ash was calculated by using the following formula.
The reagents enlisted below, required for estimate the HMF content in honey samples were prepared as follows:
Carrez solution I -15 g of potassium hexacyanoferrate K2Fe (CN) 6 3H2O was dissolved in distilled water and volume was made to 100 ml. Carrez solution II – 30 g of zinc acetate, Zn (CH3.Coo) 2 3 H2O was dissolved in distilled water and volume was made to 100 ml. Sodium bisulphate solution 0.20 g /100 g (0.2 %)-0.20 g of solid sodium bisulphate (NaHSO3) was dissolved in distilled water and volume made to 100 ml. approximately 5g of honey sample was taken and diluted in 25 ml water and then poured in to volumetric flask. Then 0.5 ml of Carrez solution I was mixed with 0.5 ml of Carrez solution II and made up the volume. Then the solution was filtered through the filter paper and first 10 ml of filtrate was rejected. 5 ml of sample was pipetted out in two test tubes and 5 ml of water was added to the one test tube and mixed well. Five ml of 0.2 % sodium bisulphate solution was added to the second test tube and mixed well for reference solution. The absorbance of the sample was determined against the reference solution with UV Spectrophotometer at wavelength 284 and 336 nm by using 1cm-quartz cells within one hour. Sample and reference solution was diluted with water and sodium bisulphate, if the absorbance exceeds 0.6 at 284 nm.
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Table 1. Dilution of sample and reference solutions carried for estimation of HMF. |
||
|
Addition to test-tubes |
Sample Solution (in ml) |
Reference Solution (in ml) |
|
Initial solution |
5.00 |
5.00 |
|
Water solution |
5.00 |
- |
|
Sodium bisulphate (0.3%) |
- |
5.00 |
HMF expressed as mg/kg = (A284 – A336) x 149.7 x 5 x D/W.
A284 = Absorbance at 284 nm; A336 = Absorbance at 336 nm.
149.7 = 126 x 1000 x 1000/16830 x 10 x 5; 126 = molecular weight of HMF.
16830 = molar absorptive and HMF at 284 nm; 10 = Conversion of g into mg.
1000 = Conversion of g into kg.
5 = Theoretical nominal sample weight.
D = Dilution factor (in case dilution is required).
W = Weight in g of honey sample.
Twenty gm of honey was weighed to the nearest 0.01g and dissolved in a suitable quantity of distilled water at 80 oC and mixed well. The test sample was filtered through a previously dried and weighed fine sintered glass crucible and washed thoroughly with hot water (80 oC) until free from sugar. The crucible was dried for one hour at 130 oC, cooled and weighed to the nearest 0.1 mg. Finally the result was expressed as percent water-insoluble solids.
Where,
M1=mass of the residue and the crucible
M= mass of the crucible
W= mass of the test portion
The results of moisture, pH, acidity, ash, Estimation of Hydroxymethyl furfural (HMF) and Water insoluble solids, total reducing sugar and sucrose content of locally produced honey are presented in Tables 2 and 3.
The moisture content of locally produced honey was in the range of 15.66 to 23.45%. All of the samples examined contained moisture content within the standard limits. According to the present results, the difference between moisture content of different locally produced honey samples were non-significant (P>0.05). Present results are similar with Nuru (1999) where the mean result of Ethiopian honey was 20.5% but higher than those of Latif et al (1956) who have reported the moisture content of Pakistani honey to be within the range of 14.3 and 18.6%. Similarly, Duthil (1983) has also assessed different honey samples for their moisture content and reported their moisture content to be within the standard limits. The moisture content of honey is related to its degree of fermentation. The control of the water content is an important requirement of proposed Codex Alimentarius Commission Standards for honey (2001), which sets an upper limit for moisture of 21 percent for honey in general.
The honey samples contained a pH from 3.45 to 4.18, with an average of 3.81. The low pH of honey inhibits the presence and growth of micro-organisms and makes honey compatible with many food products in terms of pH and acidity. This parameter is of great importance during the extraction and storage of honey as it influences the texture, stability and shelf life of honey. Published reports indicate that pH should be between 3.2 and 4.5. Present results are similar with that of Jose et al (2009) who has reported the pH value of 3.47 to 4.24, with an average of 3.91.
In nearly all honey samples, two important monosaccharide glucose and fructose predominate, which are defined as reducing sugars and accounts for around 75% of honey. According to proposed Codex Alimentarius Commission Standards (2001), a minimum reducing sugar content of 65% is required. The results of the analysis showed that the reducing sugar content of honey ranged between 61.2%-77.4% for the tested samples of locally produced honey. Comparison between honey samples showed that all of the locally produced honeys met the quality standard for reducing sugar except the three samples having 61.2, 62.2 and 64.7 which were lower than the standard permissible limit. These results are in agreement with that of Nuru (1999) Ethiopian honey means test result of 65.6% moisture and Nauta (1983) who also reported that reducing sugars in honey were in the range of 60 to 65%.
The test result mean percentage of apparent sucrose is 7.55 % which is a little higher than national standard and lower than the world standard permissible limit. This result has also some variation with Nuru (1999) who indicated Ethiopian honey mean test result of 3.6% sucrose .however, which is inacceptable range of world market.
The free acidity of honey samples is 28.2meq kg−1 (average) with a range of 0.30–57.3. Variation in free acidity among different honeys can be attributed to floral origin or to variation because of the harvest season. When the acidity becomes high, the honey becomes sour. The free acidity of honey maybe explained by taking into account the presence of organic acids in equilibrium with their corresponding lactones, or internal esters, and some inorganic ions, such as phosphate, 77. 8% of the investigated samples met the demands imposed by the regulations, which requires not more than 40 meq kg−1 and the remaining 22.2% of samples are more than the requirement (40 meq kg-1). This may be due to the origin of the flora from which the honey is made. The majority of the results are endorsed by those of Nuru (1999) Ethiopian honey mean test result of 39.9 meq kg−1 and Latif et al (1956) who also reported formic acid content of Pakistani honey to be within the permissible limits of international standards. Similarly, Stinson et al (1960) evaluated honey samples for their acid components and found these to contain butyric, acetic, formic, lactic, succinic, pyrogutamic, malic and citric acids.
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Table 2. Mean results of honey quality in the study areas compared to national and international standards |
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|
Parameters |
Study Area Test Result |
National Standards |
World Honey Standards* |
|
Moisture content (% ) |
18.5 |
17.5 - 21 |
18 - 23 |
|
Total Ash, (%) |
0.23 |
<0.6 |
0.25 - 1.0 |
|
Total reducing sugars (%) |
67.9 |
>65 |
60 - 70 |
|
Sucrose (%) |
7.6 |
<5 |
<10 |
|
Acidity (mequiv/kg ) |
28.2 |
<40 |
<50 |
|
Hydroxy methyl furfural (mg/kg) |
6.32 |
<40 |
<80 |
|
pH |
3.81 |
- |
3.2 - 4.5 |
|
Water insoluble material(g/kg) |
3.20 |
- |
<0.1 |
| *Source: Quality and Standards Authority of Ethiopia (2005) | |||
Certain nitrogen compounds, minerals, vitamins, pigments and aromatic substances contribute to the ash content of honey. The ash content of honey averages about 0.212% of its weight, but varies widely from 0.02 to over 1.0%. Codex Alimentarius Commission Standards (2001) for honey, proposed ash content not more than 0.6% for normal honey. The ash content of locally produced honey samples ranged between 0.05 – 0.60 which is within the standard limits. These results are in line with those of Nuru (1999) and Crane (1976) who reported ash content of honey samples to be within the range of 0.1-1.0%. Similarly, Mclellan (1975) evaluated honey samples for their ash content and different minerals.
Hydroxy methyl furfural (HMF) is formed by the decomposition of fructose in the presence of acid. Small amount of HMF (0.06-0.2 mg kg-1) is present naturally even in fresh honeys. Codex Alimentarius Commission Standards (2001) of honey proposed a limit of 40 mg kg-1 as an indication of heated honeys and content more than 150 mg kg-1 is taken to indicate adulteration with invert sugar. The HMF contents of locally produced honeys ranged between 0.05 and 17.70 mg kg-1. Hence, all of the samples meet the HMF standard for quality. Previously Nuru (1999) observed that Ethiopian honey mean test result of 32.4 mg/kg and Jose et al (2009) analyzed the honey samples its HMF content ranged from 0.9 to 22.8mg kg−1 (mean value ± standard deviation=7.0 ± 6.8mg kg−1). Similarly, Duthil (1983) have also reported that mean HMF content of different honey samples ranged from 5.47 to 5.95 mg kg-1.
For most consumers, good quality honey is expected to be visually free of defect, clean and clear. Honey which has a very high pollen content appears cloudy, and the presence of many other contaminations such as particles of wax, dead bees, splinters of wood, and dust certainly does make it look unappetizing and unappealing for anyone to buy and consume, and hence it appears as if it's of very low value. The water insoluble mater content of locally produced honey sample ranged between 0.01 to 23.82 gm /100gm. When the result was compared with the international quality standard maximum of 0.1 gm/100gm, only 16 samples was fit the standard from 36 samples, the remaining 20 honey samples were score above the standard. That shows the way in which the farmers handling and storing the product (in jar made from clay, ‘kil’ container made of cucumber, small ‘tasa’, plastic bag (sack of fertilizer), plastic jar and animal skin bag) after harvesting is very poor, so that the product is simply contaminated.
Significant differences (p < 0.05) were observed in moisture content and free acidity of honey samples in the district when sample from farmers compared to market samples, but no significance difference (p>0.05) is observed with the remaining parameters (Table 3).This result indicates that moisture content of honey at farmer level is probably increasing due to harvesting of un ripened honey and improper storage condition which increase the hygroscopic nature of honey.
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Table 3. Least square means and standard errors for honey quality parameters which are collected from farmer and local market. |
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|
Composition |
S ample from Farmers |
Sample from Market |
Average |
SEM |
|
Moisture |
22.65a |
17.38b |
18.52 |
0.33 |
|
Water insoluble |
4.64 |
1.57 |
3.2 |
2.17 |
|
Ash |
0.20 |
0.25 |
0.23 |
0.05 |
|
Free acidity |
20.44a |
36.03b |
28.24 |
3.47 |
|
HMF |
6.56 |
1.16 |
6.32 |
4.90 |
|
pH |
3.80 |
3.82 |
3.81 |
0.60 |
|
Reducing sugar |
67.83 |
68.02 |
67.92 |
0.96 |
|
Sucrose |
5.68 |
9.43 |
7.55 |
4.03 |
|
Means in a row having different superscript are statistically different at P<0.05; SF = Sample from farmer; SM = Sample from market; HMF = Hydroxyl methyl furfural ; SEM = standard error of mean |
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The majority of the samples were found to be in acceptable range of international standards for all of the tested parameters except for water insoluble materials which was above the standard limit by 55.6% of the tested samples. These samples were marked to be safe for human consumption. This shows the potential of the honey in this area for export as well as local consumption is very high. The range of water insoluble material could easily be brought to standard range by awareness creation/training of farmers on honey management.
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Received 14 March 2011; Accepted 3 July 2011; Published 1 September 2011