Vol. 50 No. 1 2006 Journal of Apicultural Science 5 THE QUALITY OF SYRUPS USED FOR BEE FEEDING BEFORE WINTER AND THEIR SUITABILITY FOR BEE WINTERING Violeta Ceksteryte, Jurgis Racys Lithuanian Institute of Agriculture, Instituto Aleja 1, Akademija, 58344 Kedainiai distr. Received 31 March 2005; accepted 07 March 2006 Summary The quality of several inverted syrups was assessed: Bioinwert, Apiinvert, HI, GF56, GF85, GF56+GF85 and Pchelit. Variations in the quality of the syrups Bioinwert, Apiinvert and HI were determined in the experiments carried out in summer in the isolators after bees had deposi- ted the food in the nucleus combs. Our tests showed that bees purified syrups. The sugar syrups Bioinwert A, Apiinvert A from 1999 and HI from 2001 had content of hydroxymethylfurfural (HMF) 85.9, 32.7 and 1.43 mg/kg, respectively. HMF declined when bees processed those syrups and deposited in the combs. The content of HMF in syrups Bioinwert B, Apiinvert B, HI amounted to 16.1, 2.64 and 0, respectively. The content of HMF in sugar syrups GF 85, GF 56, GF 85+GF 56 used for feeding wintering bees was 5.8, 48.0, 27.7 mg/kg. No HMF was identi- fied in Pchelit. The food deposited in the nucleus combs by bees had more biological active components compared with the food fed to bees. Diastase activity does not exist in Bioinwert A from 1999 and 2000 nor does it in Apiinvert A from 1999. This component appears in Bioinwert B – 3.88 and 6.07 Gothe units and Apiinvert B – 6.69 Gothe units. Saccharose present in the syrups S (A) from 2000 and 2001 was 47.0% and 47.8%. Due to the effect of invertase present in the bee se- cretion, the syrups S (B) contained only 11.6 and 6.75 % of saccharose. Low invertase activity 2.18 and 16.9 IU was determined in Bioinwert A from 1999 and 2000, however the activity of this enzyme increased after processing of the syrups by bees – in the Bioinwert B from 1999 it amounted to 64.6 and 53.6 IU and in Apiinvert B to 41.9 UI. The sugar syrups GF 56, GF 85, GF 56+GF 85 and Pchelit were used for feeding wintering bees. The highest food consumption 1.9 kg/comb was identified for bees fed on GF 56, however those colonies reared fewer brood. In spring crystallisation of GF 56 syrup was observed in few cells of the comb. The strength of the bee colonies after wintering on this syrup slightly de- clined from 5 points estimated in the autumn to 4.5 estimated in the spring. The best wintering of bee colonies was observed on syrups Pchelit and GF 56+GF 85. The number of brood after wintering in those bee colonies in spring was 220 and 162 in hundred cells; the food consump- tion in those colonies was 1.4 and 1.5 kg/comb, respectively. All bee colonies survivied through winter. Keywords: inverted sugar syrup, diastase, invertase, hydroxymethylfurfural, wintering of bee colonies. INTRODUCTION lisation in combs (Ohe andSchönberger During the honey flow bees provide 2000). themselves with food and accumulate win- When melezitose content in honeydew ter food supplies. Rape honey is not suita- honey is 8.0 – 12.0% or more, such honey ble for bee wintering due to the high glu- crystallises in the combs. During winter cose concentration – fructose/glucose ratio bees are not able to consume such honey from 0.86 to 1.0, which causes its crystal- because they are short of water to dissolve 6 the crystals and consequently, bees die of wheat starch was detrimental to bees since thirst (Ga³uszka et al 1996). it contained undigested polysaccharides, In the autumn, when honey is removed especially starch (Doull 1974). from hives, food reserves in the bee colo- Sugar syrups low in saccharose, but con- nies are replenished with sugar syrup. taining galactose, arabinose, xylose, When transferring sugar syrup to combs mannose, raffinose, and lactose were not bees break down saccharose present in the suitable for bee feeding (Barker and syrup into glucose and fructose, for this Lehner 1974b). The highest quality syrup they use their biological resources and up is achieved using the enzyme invertase for to 23.0% of the sugar syrup fed. These pro- the breakdown of saccharose. This enzyme cesses exhaust bees and they start wintering present in honey breaks down saccharose in a weakened condition. In order to pre- to glucose and fructose. Therefore, using vent bee exhaustion resulting from syrup natural honey it is possible to produce in- processing, it is expedient before winter to verted syrup. The Russian Institute of Api- supply bees with ready made food, i.e. with culture in Rybnoje uses such sugar inver- syrup in which sugar has already been in- sion: 72.5 kg of sugar, 7.5 kg of honey, 20 verted. In inverted sugar saccharose is bro- litres of water and 24 g of concentrated ken down into glucose and fructose, there- acetic acid (adjusted to 100%). The inver- fore the use of such food for bee feeding sion of saccharose lasts for5–6days at 34 before winter exhausts bees less – 36°C (Strojkov 1990). In different (Zaboenko 2000). Jachimowicz honey types invertase activity is diverse (1976) is of different opinion. According to and lower compared with that of commer- this author, the bees must use up their cially produced invertase, therefore pro- hypopharyngeal glands secretion transfer- duction of inverted sugar with honey addi- ring the inverted syrup to the combs ex- tion is time consuming. When pure actly the same as transferring the syrup invertase enzyme isolated from yeast is made of refined sugar (saccharose). used for saccharose breakdown, Sugar syrups produced from refined microbiologically clean inverted sugar free beet sugar and cane sugar are suitable for of bee disease causal agents (pathogenic bee feeding. Impurities present in non-re- microorganisms) as well as noxious sub- fined sugar are noxious to bees (Bailey stances, is obtained (Strojkov 1990). En- 1966). It is suggested that refined sugar zymatic yeast agent Pchelit is currently be- syrups are more suitable for bee feeding ing recommended for the production of in- before winter compared with honey. The verted sugar syrup in Russia. This agent German factory Südzucker produces high has been tested at the Institute of Apicul- quality inverted sugar syrup, which con- ture in Rybnoje. According to producer’s tains 72.7% of sugar and 27.3% of water. description Pchelit enriches inverted syrup The sugar content is composed of 30.0% with amino acids, lipids, B-group vitamins, sucrose, 31.0% glucose, 39.0% fructose, and microelements. Wintering bees fed on (Kammerer 1989). sugar syrup inverted by Pchelit, consume It is convenient for beekeepers to use in- less pollen (by 40%) and sugar (by 20- verted sugar syrup since it involves lower -30%) compared with the bees fed on sugar labour input. Some authors report that in- syrup (Bilash 2005). verted syrup is less attractive to foraging Sugar syrup should be acidified with or- bees, therefore robbing is not a problem ganic acids (citric, oxalic, acetic, lactic). with inverted sugar (Barker and Lehner The best wintering results were obtained 1974a). Inverted syrup produced from when 0.3 g acetic acid was added per kilo- Vol. 50 No. 1 2006 Journal of Apicultural Science 7 gram of sugar to the sugar syrup, prepeared El Sherbiny 1975). for feeding of wintering bees. The fecula Experimental objectives: mass in spring bees was lower when they — to assess the quality of differently pre- were fed on sugar syrup, acidified with ace- pared food for bee wintering; tic acid, compared to those, fed on non — to estimate the quality of syrups before acidified sugar syrup (Taranov 1986). feeding the bees and those stored in Old honey (Jachimowicz and El combs (after transferring them by the Sherbiny 1975) or poorly inverted syrup bees to the combs). high in HMF is not suitable for autumn — to compare the effects of various foods feeding of bees, since this substance is on wintering of honey bee colonies. toxic to bees. Jachimowicz and El Sherbiny 1975 found, that HMF is the MATERIAL AND METHODS factor that causes bee mortality. They re- port that the HMF content of 15 mg/100 g Laboratory and outdoor experiments on in commercially acid hydrolyzed invert bee winter feeding were performed at the sugar syrup significantly increased mortal- Lithuania Institute of Agriculture, Depart- ity of bees. After feeding sugar syrup with ment of Apiculture during the period 2000 a HMF content of 15 mg/100 g, in average – 2004. 58% of bees died within 20 days from the The details on the characteristics of start of feeding. HMF concentrations sugar syrups, used for feeding bees in nu- 3 mg/100 g and 6 mg/100 g were harmless cleus and for bees wintering are shown in to the bees. As a result, many specialists Table1. recommend the proper concentration of PRODUCTION OF INVERTED this compound in inverted syrups not to ex- SUGAR SYRUP WITH HONEY (HI) ceed 2 mg/100 g as it is in most honeys Three kilograms of sugar were added (Kammerer 1989). The inverted sugar into2lofboiling water and the solution syrup should be used for bees only after was stirred until sugar dissolved. When the checking HMF content in it (Jachimo- syrup’s temperature had dropped to 35°C, wicz 1976). 0.38 kg of honey was added and the syrup When saccharose is inverted with or- was well mixed. The syrup was kept for five ganic acids, HMF formation is lower com- days at 38 – 40°C and mixed twice a day.