PHYSICOCHEMICAL PARAMETERS OF ...

Proceedings of the 10th International Symposium Modern Trends in Livestock Production, October 2-4, 2013

PHYSICOCHEMICAL PARAMETERS OF BULGARIAN RAPE HONEY (Brassica spp.) AND CORIANDER HONEY (Coriandrum sativum L.) R. Balkanska, M. Ignatova Institute of Animal Science, Spirka “Pochivka” 1, 2232 Kostinbrod, Bulgaria Corresponding author: [email protected] Original scientific paper

Abstract: Honey has been essentially used as a food all over the world since ancient times. Honey contains sugars, organic acids, enzymes, amino acids, mineral elements, pollen. The composition of honey varies greatly depending on the honey floral source. The purpose of this study was to verify and compare some physicochemical parameters of rape honey (Brassica spp.) and coriander honey (Coriandrum sativum L.) samples collected from Bulgaria and to increase the data for these unifloral honey types. Seven rape honey samples and six coriander honey samples were analyzed. The quality criteria of honey are specified by the International Honey Commission (IHC) and physicochemical parameters such as colour, water content, electrical conductivity, pH, free acidity, specific rotation, diastase activity and hydroxymethylfurfural (HMF) were determined in this study. The values obtained from rape honey samples were in the range: water content 15.60 – 18.40%, electrical conductivity 0.16 – 0.27 mS/cm, pH 3.75 – 4.15, free acidity 13.23 – 16.17 meq/kg. For coriander honey samples the following values were defined: water content 15.60 – 17.00%, electrical conductivity 0.37 – 0.58 mS/cm, pH 3.70 – 4.25, free acidity 14.70 – 19.60 meq/kg. The specific rotation in both honey types was negative. Colour, diastase activity and HMF were also discussed. Key words: rape honey, coriander honey, physicochemical parameters, unifloral honeys.

Introduction Honey is a natural product which has been used as a food since ancient times. It is an important and unique food product containing bioactive compounds. The main ingredients of honey are sugars (fructose and glucose). The amount of water should be up to 20% (Council directive, 2001). Honey also contains a wide variety of other substances in small concentrations such as organic and inorganic


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acids, vitamins, enzymes, amino acids, mineral elements, flavonoides (Golob and Plestenjak, 1999). According to botanical origin, the main types of honey are blossom or nectar honey, obtained from the nectar of plants, and honeydew honey. Their characteristic properties are depending on the floral source of the nectar (Persano Oddo et al.,2004). The determination of the botanical origin is part of the quality analysis of honey. Recently, there is an increasing commercial interest to produce unifloral honeys. Actually, many consumers prefer unifloral to multifloral honeys and appreciate the possibility to choose between different honey types. Unifloral honeys have also a higher commercial value for the producers than multifloral honeys. Thus, they can be considered as premium products. Moreover, the increasing interest in the therapeutic or technological uses of certain honey varieties may also contribute to the demand of a reliable determination of their botanical origin (Ruoff et al., 2007). In Bulgaria it is produced mainly multifloral honey and some types of unifloral (acacia, lime) honey and honeydew honey. The same honey types are commercially available on the market. Very scarce data is available regarding physicochemical parameters of Bulgarian rape honey (Brassica spp.) and coriander honey (Coriandrum sativum L.). Physicochemical parameters of the coriander honey have not been described in European unifloral honeys (Persano Oddo and Piro, 2004). Until now there has been no full research that determines the physicochemical parameters of Bulgarian coriander honey, except for Atanassova et al. (2012), Dinkov and Ivanov (2010), Ivanov (1973). Though, these authors presented only few physicochemical parameters. The goal of the present work was, first, to verify and compare some of the qualitative parameters such as water content, electrical conductivity, specific rotation, pH, free acidity, diastase activity and hydroxymethylfurfural (HMF) colour. Second, it aimed to increase the data for these unifloral honey types in Bulgaria.

Material and Methods Seven rape honey samples and six coriander honey samples were analyzed. These samples were obtained from beekeepers. All samples were examined after being stored for one year at 25 ± 5 oC. The following chemical parameters were determined according to the harmonized methods of the International Honey Commission (IHC) (Bogdanov et al., 1997) and the methods described in BDS 3050-80: colour, water content, electrical conductivity, pH, free acidity, hydroxymethylfurfural (HMF) after White, diastase activity according to BDS 3050-80. Honey samples were heated up to 40 °C to dissolve the crystals, and the colour was determined by Lovibond® Honey

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ColorPod. The results were expressed in the Pfund scale (mm Pfund). Declared botanical origin of honey samples was verified by pollen analysis in the Central Laboratory for Veterinary Sanitary Expertise and Ecology, Sofia, Bulgaria. Analysis was performed by counting of pollen grains, according the method of Bulgarian regulation (BDS 3050-80). Statistical analysis was performed using MS Excel 2007. All results are presented as means ± standard deviation.

Results and Discussion According to the obtained results, Brassica spp. pollen grains are in all analyzed samples represented as predominant pollen (>60% in total pollen). Coriandrum sativum pollen grains in all samples varied from 28% up to 59% giving the average of 48%. Afterwards, samples were subjected to the analysis of physicochemical parameters. In addition, Dinkov and Ivanov (2010) found in Coriander honey above 45% Coriandrum sativum pollen. This value is in agreement with our average pollen content. The physicochemical parameters of honey are rather varying and primarily depend on the floral source. However, certain external factors also play a role such as seasonal and environmental factors. Tables 1 and 2 report the physicochemical parameters of Bulgarian rape and coriander honey. Table 1. Physicochemical parameters of rape honey Parameters

Mean±SD

Min

Max

Colour, mm Pfund Water content, %

25±6 17.34±1.00

17 15.60

33 18.40

pH

3.91±0.16

3.75

4.15

Free acidity, meq/kg Electrical conductivity, mS/cm

14.98±1.16 0.21±0.04

13.23 0.16

16.17 0.27

Specific rotation, [α]D20

-16.57±1.99

-19.00

-12.50

Diastase activity, Gothe units

23.09±3.00

19.19

26.30

HMF, mg/kg

15.13±2.70

11.68

19.16

Colour is useful criterion for the classification of unifloral honeys (Krell, 1996; Gonzales et al.,1999). Visually, colour of rape honey samples is light and varies from 17 to 33 mm Pfund. According to Szczesna et al. (2011) the colour of Rape honey ranged from 8 to 59 mm Pfund. In comparison to rape honey, coriander honey samples have light amber colour (from 41 to 68 mm Pfund) (Table 2).


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Water content is one of the parameters which provide information on the resistance of honey to spoilage by fermentation. The water content of honey depends on various factors, for example: the harvesting season, the degree of maturity reached in the hive, and environmental factors (Acquarone et al., 2007; Feás et al., 2010). The small variation observed in the water contents of these samples may be due to the similar practices for honey production applied by the beekeepers. The lower the water content, the lower the probability that honey ferments during storage. All samples have low water content, while electrical conductivity, pH value and acidity are inherent for blossom honey. As can be seen from Tables 1 and 2, water content, pH and free acidity values show good maturity and absence of undesirable fermentation in all the samples. The low pH of honey inhibits the presence and growth of microorganisms. This parameter is of great importance during the extraction and storage of honey as it influences its texture, stability and shelf life (Terrab et al., 2004). pH values for the two honey types are almost identical. The average values for pH in rape honey samples are fairly similar to those reported by Popek (2002). Atanassova et al. (2012) found higher pH values for coriander honey. The same authors noticed that pH was slightly lower in rape honey than in our research. Free acidity of coriander honey samples are, however, slightly higher, 16.09±1.87 meq/kg compared to 14.98±1.16 meq/kg in rape honey. Table 2. Physicochemical parameters of coriander honey Parameters

Mean±SD

Min

Max

Colour, mm Pfund Water content, %

58±10 16.27±0.59

41 15.60

68 17.00

pH

3.96±0.22

3.70

4.25

Free acidity, meq/kg Electrical conductivity, mS/cm

16.09±1.87 0.44±0.08

14.70 0.37

19.60 0.58

Specific rotation, [α]D20

-12.25±3.97

-18.50

-8.75

Diastase activity, Gothe units

15.02±1.46

12.43

16.50

HMF, mg/kg

17.38±1.41

15.87

19.92

Electrical conductivity values varied from 0.16 mS/cm to 0.27 mS/cm (Table 1) for the rape honey and from 0.37 to 0.58 mS/cm for the coriander honey (Table 2). The average values for the two honey types are similar to those reported by Atanassova et al. (2012). The results for electrical conductivity in rape honey are concurrent with the results of Szczesna et al. (2011).


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Negative values of specific rotation are typical for nectar honey (Bogdanov et al., 2004). The values of the specific optical rotation for all samples were negative which is consistent with other results for unifloral honeys (Persano Oddo et al., 1995). Our values for specific rotation (see Table 2) for Coriander honey are considerably higher than values reported by Dinkov and Ivanov (2010). Diastase activity 30

Gothe units

25 20 15 10 5 0

Rape honey

Coriander honey

Fig.1. Diastase activity of rape and coriander honey

Storage has a remarkable influence on the increase in HMF content and the decrease in diastase number of the honeys collected. According to Persano Oddo and Piro (2004) the concentration of HMF (≤ 40 mg/kg) and the diastase activity values (≥ 8 in units of Schade) recorded are those of honeys of high quality. In honey, HMF is related to its quality and heat processing but opposite is not true – the latter two are not related to the honey type. Mean HMF contents in the rape and coriander honey are 15.13±2.70 and 17.38±1.41 mg/kg, respectively one year after the honey harvesting. After one year storage Thrasyvoulou (1986) found that the average HMF contents increased from 0.0 to 8.8 mg/kg. Sancho et al. (1992) found that the average amount of HMF increased from 4.7 to 13.1 mg/kg for the same storage period. Similar data is reported by Yilmaz and Küfrevioglu (2001). After one year storage the average HMF content is 19.1 mg/kg. The rates of HMF in all honey samples in our study showed similarity to those mentioned above. Furthermore, HMF content for all samples (11.68 – 19.92 mg/kg, average 16.19 mg/kg) purports the fact that the samples were not fresh. But these samples are


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representative and very often the honey production could not be sold at the same year of harvesting. However, it was found that HMF contents in all honey samples were lower than 40 mg/kg (Tables 1 and 2). Rape honeys showed the highest average value of diastase activity (23.09 Gothe units). The diastase activity of Coriander honey ranged from 12.43 to 16.50 Gothe units. These results are comparable to the results reported by Ivanov (1973) for this honey type. As can be seen from Fig. 1 rape honey has higher diastase activity that coriander honey.

Conclusion Considering physicochemical parameters, coriander honey and rape honey are similar to the same honey types produced in other countries. The physicochemical parameters such as water content, diastase activity and HMF showed values in agreement with the legal limits. The mean values of electrical conductivity, colour, free acidity for coriander honey are: 0.44±0.08 mS/cm, 58±10 mm Pfund and 16.09±1.87 meq/kg, respectively. For rape honey the following mean values were obtained: electrical conductivity 0.21±0.04 mS/cm, colour 25±6 mm Pfund, free acidity 14.98±1.16 meq/kg. These parameters related to the floral origin of honey. Taking into account all the results that we have reported in this paper, we suggest that physicochemical parameters of the coriander honey should be described in European unifloral honeys.

Acknowledgment Research was financed by Project BG051PO001-3.3.06-0033 "Support for the development of doctoral graduate students and young researchers" OP "Human resorses development" Ministry of Labour and social policy European Social Fund (ESF) Project BG051PO001-3.3.06-0033 “Support for the development of doctoral graduate students and young researchers" Funded by: Operational Program "Human resorses development" Ministry of Labour and social policy European Social Fund (ESF)

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Fizičko-hemijski parametri bugarskog meda od repice (Brassica spp.) i korijandera (Coriandrum sativum l.) R. Balkanska, M. Ignatova

Rezime Med se u suštini koristi kao hrana u celom svetu još od davnina. Med sadrži šećere, organske kiseline, enzime, aminokiseline, mineralne elemente, polen. Sastav meda varira u zavisnosti od izvora cvetnog meda. Cilj ove studije je bio da se provere i uporede neki fizičko-hemijski parametri meda od repice (Brassica spp.) i korijandera (Coriandrum sativum L.) u uzorcima iz Bugarske i da se obogati baza podataka za ove tipove jednocvetnog meda. Sedam uzoraka meda od repice i šest uzoraka meda od korijandera su analizirani. Kriterijumi kvaliteta meda određeni su od strane Međunarodne komisiji za med (IHC) a fizičko-hemijski parametri, kao što su boja, sadržaj vode, elektroprovodljivost, pH, slobodna kiselosti, specifična rotacija, aktivnost dijastaze i hidrokimethilfurfural (HMF), su utvrđeni u ovoj studiji. Vrednosti dobijene od uzoraka meda repice bili su u opsegu: sadržaj vode 15,60 - 18,40%, električna provodljivost 0,16 - 0,27 mS / cm, pH 3,75 - 4,15, slobodna kiselost 13.23 - 16.17 mEk / kg. Za uzorke meda korijandera sledeće vrednosti su definisane: sadržaj vode 15.60 - 17,00%, električna provodljivost 0,37 - 0,58 mS / cm, pH 3,70 - 4,25, slobodna kiselost 14,70 - 19,60 mEk / kg. Specifična rotacija u obe vrste meda je bila negativna. Boja, aktivnost dijastaze i HMF su takođe razmatrani.

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