Journal of Apicultural Science

Attempt to assay maltodextrins occurring in starch syrup and in winter stores made by bees from that syrup

Journal of Apicultural Science. Volume 50, Issue 2, Pages 127-135, ISSN (Print) 1643-4439
A method was developed to make quantitative assays of maltodextrins: maltotetraose (Dp4), maltopentaose (Dp5), maltohexaoze (Dp6) and maltoheptaose (Dp7). The maltodextrins occur in starch syrup and in the winter stores processed by bees from that syrup. The method was checked for its suitability to detect honey adulteration with starch syrup additions. The precision and repeatability of the method when used for maltodextrins assays was satisfactory. The detectability threshold for the maltodextrins was 0.05%. Additionally, the tests of carbohydrate composition of crystallized winter store samples processed by bees from starch syrup were aimed at explaining substantial losses of colonies in apiaries fed with that syrup under the conditions of long winter of 2005/2006.
The HPLC device manufactured by Shimadzu with a refractometric detector and a column recommended to assay oligosaccharides Luna 5'ľm NH2 100D 250 x 4.60 mm (Phenomenex) was used to assay maltodextrins. The 65 : 35 acetonitrile-water system was used as an eluent, flow rate 3 ml/min, analysis time - 10 min, temperature 40°C. Maltodextrin contents (%) were assayed based on the comparing peak areas obtained in the examined samples with those from the reference solution (external standard method). The method described above is not used to identify oligosaccharides characteristic of honey. It can be used to assess the extent to which honey was adulterated with centrifuged stores hoarded by the bees in the combs following their feeding with syrup or with the syrup itself. Using that method it is possible to detect as small an addition as 10% of starch syrup inverted by bees.
Following the analysis of carbohydrate composition of crystallized winter store samples it was established that high glucose content of the winter stores in apiaries which were fed that syrup was the major cause of substantial bee colony losses sustained under the conditions of the long winter of 2005/2006. The glucose content was as high as 38.0% with a relatively low fructose content (22.1%), what explains the crystallization of glucose in the honeycomb cells. An excessive load of maltodextrins in the bee rectum can also be a hazard for the wintering bees. In the samples an average maltodextrine content was ca. 2%, the method being used to assay only a part of those compounds: associations of 4 to 7 glucose molecules.
Honey, starch syrup, maltodextrins, adulteration, method, HPLC, bee wintering
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