Microchemical Journal 93 (2009) 73–77
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Microchemical Journal
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m i c r o c
Honey from Luso region (Portugal): Physicochemical characteristics
and mineral contents
Luís R. Silva a, Romeu Videira b, Andreia P. Monteiro b, Patrícia Valentão a, Paula B. Andrade a,⁎
a
b
REQUIMTE/Department of Pharmacognosy, Faculty of Pharmacy, Porto University, Rua Aníbal Cunha 164, 4050-047 Porto, Portugal
CI & DETS / Departamento de Ambiente, Escola Superior de Tecnologia do Instituto Politécnico de Viseu, Viseu, Portugal
a r t i c l e
i n f o
Article history:
Received 29 April 2009
Accepted 3 May 2009
Available online 13 May 2009
Keywords:
Luso honey
Pollen analysis
Physicochemical analysis
Mineral content
a b s t r a c t
This work was conducted to evaluate the quality of 38 honey samples from Luso region (Portugal), and to
study the relation between Eucalyptus pollen and chemical properties of honey. Mean values obtained for
physicochemical parameters were: pH 3.83; 16.65% moisture; 80.7 °Brix sugar; 0.35% ash; 419.6 μS cm− 1
electrical conductivity; 21.5 meq/kg free acidity; 9.6 meq/kg lactonic acidity; 31.2 meq/kg total acidity;
9.41 mg/kg HMF and 18.3° Gothe diastase activity. The mineral content was determined by atomic absorption
spectrometry, and in the analysed samples, potassium was the major element, being magnesium the minor
one. Mean values obtained were (mg/kg): Ca, 59.88; K, 1150.10; Mg, 35.57; Na, 261.43. Among the overall
determined parameters, only Mg, ash and electrical conductivity were influenced by the presence of Eucalyptus pollen in the honey samples: the values obtained for Mg, ash and electrical conductivity in multifloral
honey without Eucalyptus were lower than those of either monofloral or multifloral honey with Eucalyptus.
The results obtained for physicochemical characteristics of Luso honey indicate a good quality level, adequate
processing, good maturity and freshness.
Published by Elsevier B.V.
1. Introduction
Honey is the natural sweet product produced by Apis mellifera bees
from nectar of plants (nectar honey), from secretions of livings parts
of plants or excretions of plant-sucking insects of the living part of
plants (honeydew honey). This natural complex foodstuff is produced
in almost every country and largely used as food source. Honey cannot
be considered a complete food by human nutritional standards, but it
offers potential as a dietary supplement [1]. For infants, senior citizens
and invalids, honey can be a more easily digested and more palatable
carbohydrate food than saccharose by itself.
Honey mainly contains simple sugars or monosaccharides (of
which fructose and glucose are the main components (65%)) and 18%
of water, approximately [2]. Proteins, flavour and aroma, phenolic
compounds (phenolic acids and flavonoids), free amino acids,
organics acids, vitamins and minerals constitute minor components
of honeys [2]. Honey commercially available varies greatly in quality
all over the world. This is largely assessed on the basis of colour,
flavour and density. Honey composition is influenced by the plant
species, climate, environmental conditions and the contribution of the
beekeeper [3,4]. In general, monofloral honeys are more expensive
than multifloral ones [5]. In addition, some monofloral honeys are
⁎ Corresponding author. Tel.: +351 222078934; fax: +351 222003977.
E-mail address: [email protected] (P.B. Andrade).
0026-265X/$ – see front matter. Published by Elsevier B.V.
doi:10.1016/j.microc.2009.05.005
more appreciated than others due to their organoleptic properties or
their pharmacological attributes [6]. Honey has been reported to
contain about 200 substances and is considered as an important part
of traditional medicine [7]. It has been used in ethnomedicine since
the early humans, and in more recent times its role in the treatment of
burns, gastrointestinal disorders, asthma, infected wounds and skin
ulcers have also been reported [8,9].
Several types of honey are produced in Portugal, where honey
production is a traditional practice well implanted in several regions.
Luso region is located in the centre of Portugal, being one of the most
important region of honey production in this country, due to its
edafoclimatic conditions and plants diversity, were Eucalyptus pollen
predominates. The detailed characterization of the different honey
type's existent in Portugal is important, once it will allow the
establishment of technical specifications, avoiding occurrence of
adulterations. Due to adulteration possibility, honey quality must be
analytically controlled with the aim of guaranteeing its speculation.
On the other hand, as consumers have been incrementing their
interest in monofloral honeys in detriment of multifloral ones [10],
pollen analysis is important for the commercial valorisation of honey.
The work herein was conducted to investigate the quality of 38
different samples of honey proceeding from Luso region. For this
purpose, pollen analysis was performed and physicochemical characteristics (pH, moisture, sugar, ash content, electrical conductivity,
free, lactonic and total acidity, diastase activity and hydroxymethylfurfural) and mineral contents (K, Na, Ca and Mg) evaluated.
74
L.R. Silva et al. / Microchemical Journal 93 (2009) 73–77
2. Materials and methods
2.1. Sample collection
Honey samples were collected in Luso province (centre region of
Portugal). Sampling area covered the most important production
zones (Table 1). Samples were stored at 0 °C until analysis, which
occurred no longer than one month after extraction from the hives by
beekeepers.
2.2. Pollen analysis
The botanical origin of the samples was determined using
techniques described before [11]. For floral identification, 5 g of
diluted honey sample was centrifuged at 10,000 rpm for 15 min, to
separate the pollens. Samples of separated pollen grains were spread
with the help of a brush on a slide containing a drop of lactophenol.
The slides were examined microscopically at 45×, using a bright-field
microscope (Olympus, Tokyo).
2.3. Physicochemical characteristics
Honey were analysed according to methods previously reported
for pH, moisture, Brix, ash content, electrical conductivity, free,
lactonic and total acidity, diastase activity, hydroxymethylfurfural
determination [12]. Two replicate analyses were performed for each
sample.
Table 1
Classification of honey samples.
Sample
identification
Honey type
H1
H2
H3
H4
H5
H6
H7
H8
Multifloral (Erica, Rubus, Castanea sativa)
Multifloral (Erica, Rubus, Raphanus raphanistrium)
Multifloral (Echium plantagineum, Cytisus scoparius, Rubus)
Monofloral (Eucalyptus)
Multifloral (Eucalyptus, Erica, Rhamnus)
Monofloral (Eucalyptus)
Monofloral (Lavandula stoechas)
Multifloral (Raphanus raphanistrium, Rubus, Echium
plantagineum)
Multifloral (Cytisus scoparius, Lavandula stoechas, Rubus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Multifloral (Echium plantagineum, Cytisus scoparius, Rubus)
Multifloral (Erica, Eucalyptus, Rubus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Multifloral (Rubus, Erica, Eucalyptus)
Multifloral (Eucalyptus, Trifolium hybridum, Rubus)
Multifloral (Erica arborea, Eucalyptus, Castanea sativa)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Multifloral (Eucalyptus, Erica, Rhamnus)
Multifloral (Eucalyptus, Rubus, Echium plantagineum)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Monofloral (Eucalyptus)
Multifloral (Eucalyptus, Erica, Rubus)
Monofloral (Cytisus scoparius)
Monofloral (Erica)
H9
H10
H11
H12
H13
H14
H15
H16
H17
H18
H19
H20
H21
H22
H23
H24
H25
H26
H27
H28
H29
H30
H31
H32
H33
H34
H35
H36
H37
H38
2.3.1. pH
The pH was measured by a pH-meter Consort C831 (USA), with a
precision of ±0.002 pH units. The pH of the honey was measured in
solution of 10 g honey in 75 ml of CO2 free distilled water.
2.3.2. Moisture content
Moisture was determined by refractometry, using an Atago (Japan)
model lT Abbe refractometer. All measurements were performed at
25 °C.
2.3.3. Sugar
Sugar content was determined with a special refractometer with
direct reading display, and the results were expressed as °Brix.
2.3.4. Ash
Ash content was measured by calcination, overnight, in furnace at
550 °C, until constant mass.
2.3.5. Electrical conductivity
Electrical conductivity of a honey solution at 20% (dry matter basis)
in CO2-free deionised distilled water, was measured at 20 °C in a Consort
C831 conductimeter, and the results were expressed as μS cm− 1.
2.3.6. Free, lactonic and total acidity
Free, lactonic and total acidity were determined as follows, by
titrimetric method: the addition of 0.05 M NaOH was stopped at pH
8.50 (free acidity), immediately a volume of 10 ml 0.05 M NaOH was
added and, without delay, back-titrated with 0.05 M HCl to pH 8.30
(lactonic acidity). Total acidity results were obtained by adding free and
lactone acidities.
2.3.7. Diastase activity
Diastase activity was measured using a buffered soluble starch
solution and honey, which was incubated in the thermostatic bath at
40 °C. Absorption was followed using a Perkin Elmer 25 UV/VIS
spectrophotometer and a chronometer. Using regression (without
using the data point at 0 min), lines were fitted to the absorption data
and the diastase number was calculated from the time taken for the
absorbance to reach 0.235. For samples of low diastase activity, the
regression was made on the basis of the last three data points to
improve the linear correlation. In samples of high diastase activity the
time taken for the absorbance to reach 0.235 was determined with
absorbance at 5 and 10, or 5, 15, and 20 min, depending on the activity.
Results were expressed (as Gothe degrees) as ml of 1% starch
hydrolysed by enzyme in 1 g of honey, in 1 h.
2.3.8. Hydroxymethylfurfural content (HMF)
The Winkler method was used to determine the HMF content of
honey samples: 5 g of each sample was treated with a clarifying agent
(Carrez), the volume was completed to 50 ml and the solution was
filtered. The absorbance of the filtered solution was measured at 284
and 336 nm against an aliquot treated with NaHSO3.
2.4. Determination of mineral elements
Ash values were obtained by calcination, at 550 °C, of approximately 5 g honey sample, until constant weight [13]. Five milliliters of
nitric acid 0.1 M were added to the resultant ashes, and the mixture
was stirred on a heating plate to almost complete dryness. Then, 10 ml
of the same acid was added and the mixture was made up to 25 ml
with distilled water. Calcium, potassium, sodium and magnesium
were determined by atomic absorption spectrometry (Perkin Elmer
AAnalyst 300), using an air/acetylene flame. Quantitative determination of the elements by atomic absorption spectrometry was carried
out after calibrating the instrument, using Ca (1 to 5 mg/l), K (0.1 to
2 mg/l), Na (0.1 to 2 mg/l), Zn (0.05 to 1 mg/l) and Mg (1 to 10 mg/l)
L.R. Silva et al. / Microchemical Journal 93 (2009) 73–77
75
Table 2
Distribution data for physicochemical parameters in Luso (Portugal) honey samples.
Sample
pH
Moisture (%)
°Brix (%)
Ash (%)
Electrical conductivity
(μS cm− 1)
Free Acidity
(meq/kg)
Lactonic acidity (meq/kg)
Total acidity
(meq/kg)
HMF
(mg/kg)
Diastase activity (° Gothe)
H1
H2
H3
H4
H5
H6
H7
H8
H9
H10
H11
H12
H13
H14
H15
H16
H17
H18
H19
H20
H21
H22
H23
H24
H25
H26
H27
H28
H29
H30
H31
H32
H33
H34
H35
H36
H37
H38
Mean
SD
Minimum
Maximum
3.88
4.31
4.34
3.74
4.12
4.23
4.25
3.78
3.83
3.90
4.70
4.16
4.30
4.32
3.82
4.07
4.01
4.11
3.55
3.99
3.57
3.46
3.60
3.46
3.60
3.71
3.60
3.60
3.54
3.79
3.52
3.54
3.64
3.45
3.81
3.94
3.91
4.26
3.88
0.32
3.45
4.70
17.04
15.35
15.83
14.82
15.27
15.65
13.52
13.98
14.49
15.71
14.98
14.67
14.30
17.04
15.70
15.60
15.00
14.51
18.90
18.00
16.80
19.00
19.20
19.10
18.00
19.00
17.00
16.90
17.30
16.90
19.40
16.70
16.20
17.60
17.60
18.20
19.70
17.80
16.65
1.71
13.52
19.70
80.6
80.6
80.6
81.2
80.2
80.4
82.2
80.8
81.0
80.4
80.6
80.4
82.0
80.6
79.8
79.6
81.6
81.0
80.4
81.0
82.0
80.4
79.6
79.8
81.0
79.8
82.0
81.4
80.2
81.2
79.0
82.0
81.2
81.0
81.0
80.0
79.0
80.3
80.7
0.8
79.0
82.2
0.39
0.26
0.25
0.34
0.22
0.35
0.09
0.14
0.34
0.35
0.32
0.35
0.35
0.17
0.36
0.41
0.32
0.27
0.39
0.53
0.38
0.35
0.43
0.41
0.35
0.42
0.36
0.37
0.37
0.31
0.34
0.39
0.39
0.34
0.46
0.46
0.37
0.49
0.35
0.09
0.09
0.53
473.5
318.2
301.3
412.0
263.2
418.2
114.7
168.8
415.1
420.3
385.2
417.4
420.1
206.2
436.3
497.4
391.5
323.3
477.5
636.5
462.2
422.0
517.5
496.0
429.5
506.0
437.0
443.5
446.0
373.5
411.0
474.5
478.0
410.0
555.5
553.0
441.0
594.5
419.6
106.9
114.7
636.5
33.8
26.1
22.9
29.7
25.1
26.1
16.4
12.9
38.1
17.1
24.0
20.0
18.2
19.9
25.0
26.5
12.6
10.7
24.5
19.5
19.5
22.0
27.5
20.5
17.0
22.5
19.0
18.0
18.5
10.5
18.0
20.0
20.0
19.0
17.0
35.0
30.0
15.5
21.5
6.4
10.5
38.1
8.3
7.0
10.5
9.5
6.2
4.2
4.7
4.5
9.0
11.5
5.2
5.3
6.1
9.3
14.3
10.4
9.7
10.7
11.0
8.5
15.0
11.5
11.5
8.5
8.5
15.0
10.0
10.5
12.0
6.5
8.0
15.0
12.5
12.5
8.0
16.5
11.5
5.0
9.6
3.2
4.2
16.5
42.0
33.1
33.4
39.2
31.2
30.3
21.1
17.4
47.1
28.6
29.2
25.3
24.4
29.2
39.2
36.9
22.2
21.4
35.5
28.0
34.5
33.5
39.0
29.0
25.5
37.5
29.0
28.5
30.5
17.0
26.0
35.0
32.5
31.5
25.0
51.5
41.5
20.5
31.2
7.8
17.0
51.5
1.75
5.90
11.75
3.11
2.45
6.95
5.35
4.35
14.60
6.35
7.22
5.82
2.54
15.54
8.50
8.36
5.09
9.08
10.00
6.38
9.31
15.05
9.10
12.25
15.80
8.10
5.09
8.84
17.23
14.70
25.45
10.26
4.58
32.75
13.85
2.94
6.56
4.63
9.41
6.35
1.75
32.75
23
14
4
6
10
13
5
5
27
16
8
19
16
3
17
15
15
18
27
22
26
29
25
33
21
24
23
23
27
19
7
21
38
11
20
25
28
14
18.3
8.6
3
38
SD: standard deviation.
solutions dissolved in 0.1% lanthanum (La). La was utilized as a matrix
modifier in order to overcome the chemical interferences in the air/
acetylene flame. All samples were analysed in triplicate.
The results obtained for the several physicochemical parameters
determined are presented in Table 2. Honey pH is affected by the
conditions during extraction and storage, which also influences
texture, stability and shelf-life. pH is indeed a useful index of possible
2.5. Statistical analysis
Data are represented as mean ± standard deviation. The results
were statistically analysed by analysis of variance (ANOVA) methodology followed by Fisher's PLSD test. Differences were considered
significant for p b 0.05.
3. Results and discussion
Table 1 shows the floral origin of honey samples determined by
microscopy pollen analyses. Data indicate that 63% of honey samples
were monofloral and 37% were multifloral. Eucalyptus sp. was a
predominant source used by honeybees in the Luso region, once Eucalyptus pollen was detected in 79% of the total analysed samples.
Furthermore, 92% samples of monofloral honey were from Eucalyptus
sp., 4% were from Erica sp. and 4% from Cytisus scoparius. Multifloral
honeys contained several pollen types with a considerable percentage
of pollen grains from Eucalyptus sp., Erica sp., Rubus sp., Lavandula
stoechas, Castanea sativa and C. scoparius.
Fig. 1. Linear regression of ash content (% w/w) and conductivity (μS cm− 1).
76
L.R. Silva et al. / Microchemical Journal 93 (2009) 73–77
Table 3
Distribution data for cationic mineral content in Luso (Portugal) honey samples.
Sample
Ca (mg/kg)
K (mg/kg)
Mg (mg/kg)
Na (mg/kg)
H1
H2
H3
H4
H5
H6
H7
H8
H9
H10
H11
H12
H13
H14
H15
H16
H17
H18
H19
H20
H21
H22
H23
H24
H25
H26
H27
H28
H29
H30
H31
H32
H33
H34
H35
H36
H37
H38
Mean
SD
Minimum
Maximum
10.80
6.24
17.70
85.33
15.07
82.33
13.38
48.84
134.35
68.40
19.90
71.65
58.65
16.49
16.27
54.80
106.91
79.17
80.47
49.40
122.45
107.25
62.68
106.10
85.45
37.01
91.65
104.37
50.20
56.02
53.33
75.13
68.55
52.55
44.15
15.96
71.41
35.14
59.88
33.97
6.24
134.35
1196.30
1013.50
436.56
1520.60
653.02
397.17
117.55
188.98
798.48
1016.20
958.25
670.00
809.81
1645.00
1097.50
2040.50
1320.20
1200.00
891.04
1564.60
1115.40
1305.70
1813.10
1906.70
718.75
1732.30
1274.20
928.76
850.00
977.69
906.38
1324.60
966.25
1303.70
1187.50
2590.60
1600.60
1667.00
1150.10
513.26
117.55
2590.60
36.23
34.97
20.66
34.30
28.27
25.04
12.61
10.63
46.66
28.69
47.87
36.91
35.47
22.07
41.13
44.66
25.25
25.10
26.36
70.00
35.86
27.64
39.74
42.88
25.25
45.13
30.69
30.70
48.84
37.00
40.92
39.46
42.05
38.19
35.49
70.41
31.97
36.78
35.57
12.21
10.62
70.41
272.25
209.94
244.02
667.39
253.76
151.62
95.029
100.38
225.92
233.00
534.72
224.50
228.59
90.224
629.27
727.78
181.91
147.35
154.00
464.01
271.53
195.41
244.66
266.88
168.75
242.21
184.20
138.63
256.50
183.10
236.71
175.20
430.50
203.25
169.49
455.79
101.22
174.45
261.43
158.31
90.22
727.79
SD: standard deviation.
microbial growth, since most bacteria grow in a neutral and mildly
alkaline environment, while yeasts and moulds are capable of
developing in an acidic environment (pH = 4.0–4.5) and do not
grow well in alkaline media [14]. The pH values of the analysed honey
samples ranged from 3.45 to 4.70 (mean value = 3.88). These values
are in accordance with acceptable range for honey [15] and similar to
those obtained with others Portuguese honeys [5].
Percent moisture in the analysed honeys ranged from 13.53 to
19.70 (mean value = 16.65). The water content of honey depends on
various factors, like the harvesting season, the degree of maturity
reached in the hive and climatic factors. The maximum amount of
water contained by honey is regulated for safety against fermentation.
All the samples contained less than 20% water, the maximum amount
allowed by international and Portuguese legislations [16].
Moisture and sugar content are strictly correlated and anomalous
values of Brix degrees (directly related with sugar content) may be a
reliable index of adulteration [13,14]. The analysed samples presented
Brix degrees ranging from 79.0 to 82.2 (average = 80.7), which are
similar to those from others Portuguese honey samples [5].
Ash content is a parameter used for the determination of the botanical
origin (floral, mix or honeydew) [17]. The results found (0.09–0.53%) are
within the limit allowed for floral honeys (0.6%), indicating clearness of
honey samples and possibly lack of adulterations with molasses [1].
The electrical conductivity of honey is closely related to the concentration of mineral salts, organic acids and proteins. This parameter
shows great variability according to the floral origin and it is
important for the differentiation of honeys of different floral origins
[18]. The results obtained for the honey samples under study varied
between 114.7 and 636.5 μS cm− 1 (average = 419.6 μS cm− 1). These
values are below the maximum limit indicated by Portuguese
legislation for nectar honey (800 μS cm− 1).
The increase in ash content of the honey samples from Luso region
was accompanied by the increase of electrical conductivity, as previously reported by others [19,20]. This linear relationship is
characterised by a correlation coefficient R equal to 0.99 (Fig. 1).
Honey acidity is due to the presence of organic acids, mainly
gluconic acid, in equilibrium with their corresponding lactones or
internal esters, and to inorganic ions, such as phosphate, sulphate and
chloride [13,21]. The lactonic acidity is considered as the acidity
reserve when the honey becomes alkaline, while the total acidity is
the sum of free and lactonic acidities [18]. Free acidity was within the
limits of Portuguese and European legislations (below 50 meq/kg),
indicating the absence of undesirable fermentation. Lactonic acidity
ranged were from 4.2 to 16.5 meq/kg (average = 9.6 meq/kg). Total
acidity varied between 17.0 and 51.5 meq/kg, with a mean value of
31.2 meq/kg. The results obtained for acidity were in agreement with
data reported for other Portuguese honeys [1,5] as well as for samples
Fig. 2. Means of ash, electrical conductivity and magnesium values for three different honey groups, considering floral origin, particularly multifloral without Eucalyptus, monofloral
Eucalyptus and multifloral with Eucalyptus.
L.R. Silva et al. / Microchemical Journal 93 (2009) 73–77
from other geographical locations [13,18,22–24]. The variation of total
acidity has been attributed to harvest season [25].
HMF content is widely recognized as parameter of freshness for
honey samples. Several factors influence the formation of HMF, such
as storage conditions (e.g. temperature) and floral sources [18,26]. It is
well known that honey heating results in the formation of HMF, which
is produced during acid-catalysed dehydratation of hexoses, such as
fructose and glucose [27]. The amounts found fell within the European
legislation, corresponding to a high degree of freshness, which was
in agreement with the information provided by the producers: all
samples presented HMF levels below 40 mg/kg of honey, ranging
from 1.75 to 32.75 mg/kg (average = 9.41 mg/kg).
Diastase activity is a parameter used to determine if honey has
been extensively heated during processing, because the enzyme is
susceptible to heating and storage factors. The herein honey samples
exhibited very different values, ranging between 3 and 38° Gothe,
and only six samples presented an inappropriate diastase activity
(Table 2), with values below 8° Gothe [16], suggesting inadequate
storage or processing.
The mineral content is an important index of possible environmental pollution and a potential indicator of geographical origin of
honey [3]. The results of the cationic metals determined in Luso honey
samples are summarized in Table 3. Potassium was quantitatively the
most important mineral, since, in mean, it accounted for 76% of the
total mineral, with an average content of 1150.1 ppm. Studies from
other geographical locations also revealed potassium to be the most
abundant element [17,19,20,28]. Sodium, calcium and magnesium
were present in moderate amounts in the honey samples, with
average contents of 261.43, 59.88 and 35.57 ppm, respectively. Thus,
sodium accounted for 17%, calcium for 4% and magnesium represented
3% of total quantified minerals. The mineral contents are similar to
those described previously [20,29].
To evaluate the possible relationship between floral origin and
chemical contents of honey, the samples were segregated in three
different brands considering the floral pollen analysis, namely:
monofloral Eucalyptus honey, multifloral honey with Eucalyptus and
multifloral honey without Eucalyptus. Significant differences among
the honey brands were performed by variance analysis (ANOVA),
followed by Fisher's PLSD test. Fig. 2 plots the mean and standard
deviation of the chemical parameters that show significant differences
between monofloral Eucalyptus honey and multifloral honey with or
without Eucalyptus. Data of Fig. 2 revealed that the values found for
Mg, ash and electrical conductivity in multifloral honey without Eucalyptus are lower than those of monofloral or multifloral honey with
Eucalyptus. Thus, Mg, ash and electrical conductivity are chemical
parameters that can be used to discriminate the monofloral Eucalyptus honey samples from the multifloral, independently to have or not
Eucalyptus pollen. Additionally, the results obtained for the other
parameters analysed in the present work are important to characterise
the properties the honey samples from the Luso Portugal region, but
not to be used to differentiate the floral origin.
4. Conclusions
Honeys from Luso region present a good level of quality, once 32 of
the 38 analysed samples are in agreement with the European honey
directive [30] and Portuguese legislation [16], indicating adequate
processing, good maturity and freshness. Six samples did not fit
within European and Portuguese standards relative to the diastase
activity, reflecting inadequate sample manufacture and/or storage.
Potassium is the most abundant of the determined elements.
Magnesium and ash contents and electrical conductivity may be
used to discriminate the Eucalyptus monofloral from the multifloral
honey samples, independently to have or not Eucalyptus pollen,
suggesting that mineral content is highly dependent on the type of
flower used by bees.
77
Acknowledgment
This work was supported by Programa Apicola 2006. Luís R. Silva is
indebted to Eng. Nelson Miranda and to Eng. Andreia Chasqueira, from
Associação de Apicultores do Litoral Centro (Luso), for supplying
samples.
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