ЕXPERIMENTAL DETECTION OF HONEY ADULTERATION WITH ISOSWEET P USING A MODIFICATION OF THE WINKLER S METHOD

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1 ЕXPERIMENTAL DETECTION OF HONEY ADULTERATION WITH ISOSWEET P USING A MODIFICATION OF THE WINKLER S METHOD D.H. DINKOV Faculty of Veterinary Medicine Department of Hygiene, Technology and Control of Animal Foodstuffs, Veterinary legislation and Management, Trakia University, 6000 Stara Zagora, BULGARIA dinkodinkov@yahoo.com Abstract A quick method for demonstration of Robinia and multifloral adulteration with Isosweet P, based on the routine Winkler's method [1, 2, 4, 13], is described. The study was performed on 10 Robinia and 10 multifloral samples from various regions of Bulgaria. The differences in the content of 2hydroxymethyl5furfuraldehide (HMF), prior to and following the Winkler were statistically significant. The modification of the procedure consisted in determination of HMF content in samples prior to the standard test for adulteration. When the differences in HMF values are bigger than 0.9 mg% in Robinia and 1.5 mg% in multifloral, it is adulterated with no less than 10% Isosweet P. Key words : Robinia /multifloral /adulteration/isosweet P. Introduction One of the properties of monosaccharides is their dehydratation in the presence of mineral acids and the formation of cyclic compounds. The hexoses (disaccharides as well) form 2hydroxymethyl5 furfuraldehyde (HMF) that is further decomposed to levulinic and formic acids [7, 10]. Similar processes are observed in, as a product rich in carbohydrates. Under the influence of the multiple organic acids (citric, gluconic, oxalic, succinic, tartaric, lactic, butyric, maleic, malic, pyroglutamic, benzoic, valerianic, formic) and some higher fatty acids, the HMF content is progressively increasing [8]. The HMF content depends on the temperature, the duration of storage or heating, the content of various sugars, ph, the mineral content (especially that of iron) and the water content of [6, 7, 10]. According to some authors [3], fresh contains practically no HMF but its concentrations increase during storage. Many studies [8, 10, 11, 12], have shown that HMF levels in natural nonheated is almost always under 1 mg%. For 12 years, the HMF content could increase up to 34 mg% or more depending on the temperature of storage. The high HMF content in s is related to its longterm storage or to its overheating for liquidification of crystallized [12]. The heating of, as part of its industrial technology, leads to decrease in the content of monosaccharides and especially that of fructose, the enzymes are inactivated and the HMF content increased. For instance, the accumulation of 3 mg% HMF requires days at 30 o C, 2050 days at 40 o C, 4.59 days in 50 o C, 12.5 days at 60 o C and 514 hours at 70 o C [8]. At 1214 o C, HMF content in increases insignificantly for one year by about mg%. During the heating of crystallized to about 40 o C, HMF content does not change while at 60 o C it increases 45 times. It is also found out that HMF content in depends on its initial concentrations [10, 11, 12], and on its botanical origin. For instance, in rape, heated to 60 o C, the HMF content increases from 0.4 to 1.4 mg% for 24 h while in multifloral from 0.75 to 2.7 mg% [11]. It is proved that the heat processing of at 5060 o C could elevate the HMF levels up to 34 mg%. The widely used pasteurization of bee at 56 o C results in the formation of 3 mg% HMF for 1836 h [7, 12]. Some authors [11], performed experiments with various types of (rape, meadow and wood ) that were liquidified at various temperatures and overheated in a microwave oven. It was found out that the HMF content in rape and meadow increased by about 0.1 mg% after staying in a 40 and 50 o C water bath for 24 h. A weak elevation of HMF up to mg% from an baseline value of mg% occurred at heating to 60 o C. The same was valid for wood too HMF content increased by mg% after 6 h at 40 o C; by mg% after a 24hour stay at 50 o C compared to the baseline content (0.250 mg%). A more considerable increase was noticed only after the stay of wood for 24 h at 60 o C: up to mg% vs the initial value of mg%. Isosweet P is a purified and concentrated aqueous solution of saccharides, intended for feed purposes, obtained via enzymatic hydrolysis of corn starch, isomerization of dextrine syrup and chromatographic separation of fructose. It is produced by Amylium Bulgaria LTD, Razgrad.

2 The most significant changes in occurred following heating in a microwave oven. Thus, only after 2.5 min at 76.9 o C (measured in ) the initial HMF value (0.749 mg%) of meadow reached mg% while at a inner temperature of o C, HMF became mg% for 3.5 min. For wood, the initial HMF content of mg% became mg% after 2 min at 76.9 o C. According to this study, HMF content is not a suitable criterion for detection of heatprovoked changes in s. The maturity and the naturalness of could be evaluated through of the enzyme activities of invertase, glucosoxidase and diastase [11]. In most standards (including the Bulgarian state standards [1, 2] ), and the newest proposals of the European Honey Commission [4], the upper limit of HMF content is 4 mg% (40 mg/kg). This upper limit is suitable for technologically processed but is high for nonheated [7, 8]. Thus, in Bulgaria, the upper allowed limit of HMF content in nonheated is 2 mg% [1]. Some European bee federations (Germany, Belgium, Italy, Austria, Spain) market a part of their as "quality ", having no more than 1.5 mg%. In international trade, the maximum value of 4 mg% has proven satisfactory [1, 4, 5, 7, 8]. On the basis of reviewed bibliography it could be concluded that until now HMF is used as a parameter for control of the conditions for obtaining and processing as well as for marker of adulteration with commercial glucose, inverted sugar and product subjected to continuous overheating or longterm storage. It must be emphasized that there are no data about the use of HMF for detection of the addition of Isosweet P for detection of sugaradulterated bee. Because of the experimentally obtained low HMF content in Isosweet P (1.01 mg% see Material and methods) and the practical impossibility for its detection as adulterant by the current routine methods of (in Bulgaria the Bulgarian State Standards [1, 2] ). The lack of a maximum reducing sugars content in Bulgarian bee [2}, however allows the noncontrolled addition of Isosweet P (that is included Dglucose and Dfructose) as a cheaper product and creates prerequisites for adulteration of s from companies occupied with purchasing, processing and trading of that product. All those facts necessitated the performance of more detailed studies on Winkler's method [2, 4, 13], and its modification by adding 10% citric acid and heating the samples in a boiling water bath for 20 min, enhancing the destruction of fructose in Isosweet P. This modification of the standard method was performed in order to detect the presence of Isosweet P in Robinia and multifloral as adulterant. Materials and methods The experiment was performed on 10 Robinia and 10 multifloral natural samples according to Bulgarian regulations [1, 2], obtained from Palhutev Honey Co. Stara Zagora ( processing factory). The samples originated from different regions and phytogeographic areas of Bulgaria. The existing adulteration with Isosweet P was excluded by sampling from different beekeepers, pollen for determination of the botanical origin and by a complete physicochemical according standard methods [1, 2, 4]. The detection of eventually added Isosweet P (with HMF content 1.01 mg% before the experiment and 5.97% after it) to, the following procedures were performed. From all samples of Robinia and multifloral (n=10 each), 20% solutions were prepared. Twenty percentage Isosweet P solutions were prepared as well. The HMF content of solutions was analyzed by the standard Winkler's method [2, 4, 13] see Tables IIIV. Afterwards, increasing amounts of 20% Isosweet P solution (equal to 10, 20, 30, 40 and 50% Isosweet P) and 10% citric acid (C 3 H 4 (OH)(CO 2 H 3 ) 3, molecular weight ; d=1.594; this acid was chosen because of its natural presence in bee [8] ), were added to 20% solutions (Table I). Preparation of samples for detection of Isosweet P in multifloral and Robinia Honey type Sample No 20% solution Robinia sp. and ml Amount of added 20% Isosweet P 0.2 ml (10%) 0.4 ml (20%) 0.6 ml (30%) 0.8 ml (40%) 1.0 ml (50%) Amount of added 10% citric acid 2.2 ml 2.4 ml 2.6 ml 2.8 ml 3.0 ml Total volume 4.4 ml 4.8 ml 5.2 ml 5.6 ml 6.0 ml Table I

3 The test tubes were put into a boiling water bath for 20 min, then cooled at running water to room temperature and the HMF was immediately determined by the Winkler's method. The results are presented in mg%. All results were statistically processed with the Student's ttest. Results and discussion Our results for the of HMF content in Robinia and multifloral with the addition of 10, 20, 30, 40 and 50% Isosweet P are presented in Table II. Honey type Prior to the experiment Content of HMF (mg%) in Robinia (n=10) and multifloral (n=10) with addition of 10, 20, and 50% Isosweet P HMF content Added Isosweet P, % After the experiment HMF content in after the addition of Isosweet P and performance of the R O B I N I A sp Table II M U L T I F L O R A L It is seen that after the performance of the, HMF content was elevated by about 0.3 mg% vs the initial one. Those values are similar to data obtained by others authors after heating bee [7, 8, 11]. In all samples where various percentages of Isosweet P were added, HMF values were higher by 12 mg% compared to baseline levels. For multifloral specimens, the tendency towards a considerable difference in HMF concentrations prior to the experiment and following the addition of Isosweet P, observed in Robinia, was also present. Thus, the HMF content after the performance of the was higher by mg% vs the initial values in all studied samples. After the addition of Isosweet P (10%50%), this parameter was elevated by 1.6 mg% and 2.5 mg% vs baseline (in case of added 10% and 50% fructose, respectively). The average HMF values in Robinia samples (Table III) were 1.52 ± 0.27 mg% prior to the experiment. The differences after the performance of the were statistically significant (p=0.0316). After the addition of 10% Isosweet P however and the performance of the, the average HMF content increased up to 2.48 ± 0.27 mg% (p0.0001). Those values were significantly higher compared to nonadulterated Robinia (1.83 ± 0.29 mg%).

4 Table III Statistical significance of results for HMF content (mg%) in prior to and after the as well as after the addition of 10% Isosweet P and performance of the Honey type Robinia sp. Statistical significance X (HMF mg%) P* X (HMF mg%) P* Statistically significant difference (at P 0,05 ) Prior to the 1,52 1,15 2,07 1,68 1,2 2,15 0,0316 0,0690 After the 1,83 0,29 1,44 2,43 2,0 0,39 1,48 2,68 After the addition of 10% Isosweet P and performance of the 2,48 2,11 3,03 3,27 2,8 3,74 In multifloral the average HMF values were 1.68 ± 0.33 mg% prior to the study and 2.0 ± 0.39 mg% after the experiment with level of significance p= Similarly, the differences between HMF levels in nonadulterated samples and samples with 10% Isosweet P (3.27 ± 0.33 mg%) were significant (p0.0001). The comparison of the results for HMF content prior to the performance of the experiment and the data obtained after the addition of 10% Isosweet P and performance of the (Table IV), showed statistically significant differences in both kinds of p The average HMF values in Robinia specimens prior to the were by 0.96 mg% lower than the average content Honey type Robinia sp. Statistical significance of results for HMF content (mg%) in prior to the as well as after the addition of 10% Isosweet P and performance of the Statistically significant difference ( at P 0,05 ) Statistical significance X (HMF mg%) Р* X (HMF mg%) Р* Prior to the 1,52 1,15 2,07 1,68 1,20 2,15 Table IV After the addition of 10% Isosweet P and performance of the 2,48 2,11 3,07 3,27 2, in specimens with Isosweet P after the. In multifloral samples the same tendency was observed: the average HMF concentrations prior to the experiment were 1.68 ± 0.33 mg% while in specimens with 10% Isosweet P after the experiment 3.27 ± 0.33 mg% or by 1.59 mg% higher. Conclusion On the basis of our data we propose to controlling organs a modification of the standard Winkler's method [2, 4, 13], for determination of HMF in, consisting in addition of 10% citric acid and staying for 20 min in a boiling water bath in order to detect adulteration of natural Robinia and multifloral bee with Isosweet P. For this purpose, the HMF content of studied samples have to be determined according to the standard Winkler's method [2, 4, 13], prior to and following the performance of the modification. When the resulting differences are higher than 0.9 mg% in Robinia and 1.5 mg% in multifloral, then the product is adulterated with at least 10% Isosweet P.

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