| ObjectiveHoney is known as a natural food withmedicinal properties in Traditional Chinese Medicine.Honey has been used in Traditional Chinese Medicine to treat many diseases for morethan two thousand years.It possesses the ability ofdetoxification,pain relieve andmaintaining the immunity of humans.Honey is also a nutritive food and a kind of high quality sweetener.Even though China is the honey production leader,the honey quality is not the best,due to the frequent quality problems.Although China ranks the first in honey export,the average export selling price is comparatively low.There is a huge price difference when comparing to the imported honey from other countries.Therefore,the aim of this study is to compare the quality of local and overseas honey products by applying modern testing and analyzing technology,in order to provide a reference for further improvement of the quality of honey produced in China.Methods1.Analysis of standards of physical characteristics of local and overseashoney productsThe variation of moisture content in local and overseas honey products is determined by refractometer.The variation of ash content in local and overseas honey products is to be determined according to the "National Food Safety Standard:Determination of Ash in Food(GB 50094-2010)".The variation of activity of starch amylase in local and overseas honey products is to be determined by using the iodine-starch colorimetry.The determination of the variation of Hydroxymethylfurfural(HMF)content in local and overseas honey products is to be carried out by High-Performance Liquid Chromatography(HPLC).The determination of total phenolic acid in in local and overseas honey products by Folin phenol method,compare the difference of total phenolic acid content in local and overseas honey.2.Analysis of carbohydrates content in local and overseas honey productsThe estimation of total carbohydrates content in honey products is to be determined by sulphuric acid-phenol method.In order to compare the variations of glucose,fructose,sucrose and maltose content in local and overseas products,these four kinds of carbohydrates are to be determined by High Performance Liquid Chromatography-Evaporative Light Scattering Detector(HPLC-ELSD).3.Analysis of amino acids content in local and overseas honey productsIn order to compare the total amino acids content in local and overseashoney products,total amino acids are determined by ninhydrin reaction at wavelength of 570nm,with the use of leucine as the control.Amino acids in honey products are isolated by 732-cation exchange resin.Seventeen amino acids are then separated by pre-column derivatization and analyzed by the Reversed Phase-HPLC.Comparison of amino acids content in honey products is to be carried out.4.Comparative study of the fingerprint of amino acids content in local andoverseas honey productsThe fingerprints are established by the Reversed Phase-HPLC after pre-column derivatization of 32 batches of honey products.With the use of the fingerprint technology,comparative study on the amino acids profile of different honey samples is to be conducted.5.Comparative study of antioxidant activity(in vitro)of local and overseashoney productsComparison of the antioxidant activity(in vitro)of honey products is evaluated by DPPH free radical scavenging assay,scavenging ofsuperoxide cationand the inhibition of hydroxylradical tests.6.Determination of the residues of veterinary drugs in local and overseashoney productsAccording to the "Determination of the residues of Amitraz and its metabolites-HPLC(GBT21169-2007)",Amitraz and its metabolite(2,4-xylidine)residues in honey products are isolated and determined by extraction method and HPLC respectively.Variations of Amitraz and its metabolite in local and overseas honey productsare compared.Flumethrin residues are isolated and purified by the combination of extraction method and solid-phase extraction technology.They are then determined by UPLC.Flumethrin residues content in honey products are compared.7.Determination of metal elements content in local and overseas honeyproductsIron,zinc,copper,manganese,chromium contents are determined by Flame atomic absorption spectrometry after the wet digestion of honey products.Variations of content of these five metal elements in honey products are compared.Results1.Analysis of physical characteristics of local and overseas honey productsThe average moisture content in locally produced honey products was 20.08%,whereas that of overseas honey products was 18.99%.There was significant statistical difference in the moisture content in local and overseas honey products(p<0.05).The average ash content in locally produced honey products was 0.20 g/100g,whereas that of overseas honey products was 0.16 g/100g.There was significant statistical difference in the ash content in local and overseas honey products(p<0.05).The average activity of starch amylase in locally produced honey products was 135,82U/dl,whereas that of overseas honey products was 193.88U/dl.No significant statistical difference in the activity of starch amylase was found in local and overseas honey products(p>0.05).The average HMF content in locally produced honey products was 35.38 mg/kg,whereas that of overseas honey products was 29.89 mg/kg.No significant statistical difference in the HMF content was found in local and overseas honey products(p>0.05).The average phenolic acid content in locally produced honey products was 25.15 mg/kg,whereas that of overseas honey products was 36.21 mg/kg.There was significant statistical difference in the phenolic content in local and overseas honey products(p<0.05).2.Analysis of carbohydrate content inlocal and overseas honey productsThe average total carbohydrates content in locally produced honey products was 794.16 mg/g,whereas that of overseas honey products was 808.88 mg/g.No significant statistical difference in the total carbohydrates content was found in local and overseas honey products(p>0.05).The average glucose content in locally produced honey products was 388.74 mg/g,whereas that of overseas honey products was 406.33 mg/g.There was significant statistical difference in the glucose content in local and overseas honey products(p<0.05).The average fructose content in locally produced honey products was 356.11 mg/g,whereas that of overseas honey products was 341.83 mg/g.No significant statistical difference in the fructose content was found in local and overseas honey products(p>0.05).The average sucrose content in locally produced honey products was 15.54 mg/g,whereas that of overseas honey products was 18.46 mg/g.No significant statistical difference in thesucrose content was found in local and overseas honey products(p>0.05).The average maltose content in locally produced honey products was 33.77 mg/g,whereas that of overseas honey products was 42.26 mg/g.There was significant statistical difference in themaltose content in local and overseas honey products(p<0.05).3.Analysis of amino acids content in local and overseas honey productsThe average total amino acids content in locally produced honey products was 116.93 mg/g,whereas that of overseas honey products was 124.78 mg/g.No significant statistical difference in theamino acids content was found in local and overseas honey products(p>0.05).By comparing the seventeen amino acids in honey products,it was found that the average content of Asp、Gln,Ser,Gly,His,Arg,Thr,Ala,Pro,Tyr,Val,Met,Ile,Leu,Phe,Trp,Lys in locally produced honey products was in the order of2.70,0.58,1.70,1.60,1.24,0.51,0.87,2.03,42.41,3.99,1.72,1.90,0.32,1.32,1.16,22.08,2.74,1.81 mg/100g.On the other hand,the average content of Asp,Gln,Ser,Gly,His,Arg,Thr,Ala,Pro,Tyr,Val,Met,Ile,Leu,Phe,Trp,Lys in overseas produced honey products was in the order of3.49,0.99,1.94,1.69,2.00,0.64,1.23,2.49,74.22,3.90,1.90,0.25,1.30,1.23,16.66,3.12,2.47 mg/100g.Among these,there was significant statistical difference in His,Pro,Trp,Lys in local and overseas honey products(p<0.05).4.Comparative study of the fingerprint of amino acids content in local andoverseas honey productsIt was found that the recovery rate of amino acids was greater than 90%by using the 732-cation exchange resinfor isolation.This proved the adsorption properties of 732-cation exchange resin for amino acids was good.Regarding the establishment of the fingerprints of free amino acids by the use of PITC as thederivatizationagentin the Reversed Phase-HPLC analysis after pre-column derivatization,except for particular samples,the degree of similarity of the honey samples was greater than 0.900.Sixteen peaks were found in all 32 batches of honey samples.Except for samples A4 and A5,the degree of similarity of the locally produced honey samples was greater than 0.940,when compared to the control.On the other hand,except for sample B11,the degree of similarity of the overseas honey samples was greater than 0.960,when compared to the control.By undergoing cluster analysis,32 hoeny samples were classified into five categories.The first category includes samples A2,A6,A 9,A 10,A13,A15,B1,B2,B3,B10,B13,B14,B15,B16.The second category includes samples Al,A3,A5,A7,A8,All,A14,A16,B9,B12.The third category includes samples A12,B5,B6,B7,B8.The fourth category inclues samples A4、B11.While the fifth category inclues B4 sample.5.Comparative study of antioxidant activity(in vitro)of local and overseas honey productsBy using the DPPH free radical scavenging assay,it was found that the scavenging rate of DPPH free radical in locally produced honey products were 70.65%and 52.10%when the solution concentration of the samples was set at 200 mg/mL and 100 mg/mL respectively.Whereas the scavenging rate of DPPH free radical in overseas honey products were 88.95%and 70.49%when the solution concentration of the samples was set at 200 mg/mL and 100 mg/mL respectively.There was significant statistical difference in the DPPH free radical scavenging activity in local and overseas honey products(p<0.05).When comparing the superoxide cationscavenging ability,it was found that the average superoxide cationscavenging ability was 106.73 U/kg and 127.40 U/kg in local and overseas honey products respectively.There was significant statistical difference in the superoxide cationscavenging activityin local and overseas honey products(p<0.05).To the ability of inhibiting hydroxyl free radicals in honey products,it was found that the average inhibiting ability was 369.29 U/g and 410.14 U/g in locally produced and overseas honey products respectively.No significant statistical difference inthe ability of inhibiting hydroxyl free radicals was found in local and overseas honey products(p>0.05).6.Determination of the residues of veterinary drugs in local and overseas honey productsIt was found that no Amitraz was determined in the 32 batches of local and overseas honey products.However,its metabolite(2,4-xylidine)was determined at an average level at 107.99 μg/100g and 101.41 μg/100g in locally produced and overseas honey products respectively.No significant statistical difference inthe amount of Amitraz metabolites was found in local and overseas honey products(p>0.05).When compared to the flumethrin residues in local and overseas honey products,it was found that the amount of flumethrin residues in locally produced honey products and overseas honey products were 5.86 μg/100g and 5.05 μg/100g respectively.No significant statistical difference in theflumethrin residuescontent was found in local and overseas honey products(p>0.05).7.Determination of metal elements content in local and overseas honey productsThe average iron content was 5.01 mg/kg in both local and overseas honey products.No significant statistical difference in theiron content was found in local and overseas honey products(p>0.05).For the other metal elements,it was found that the average amount of copper,zinc,manganese and chromium in locally produced honey products were 0.53 mg/kg,3.01 mg/kg,0.53 mg/kg and 3.11 μg/kg,while that in overseas honey products were 0.41 mg/kg,2.18 mg/kg,0.38 mg/kg and 2.11 μg/kg respectively.There was significant statistical difference in the copper,zinc,manganese and chromiumcontent in local and overseas honey products(p<0.05).Conclusion1.The physical characteristics of overseas honey products were comparatively betterThe amount of the total phenolic acid and the activity of starch amylase were lowered in locally produced honey products,whereas the moisture content,the total ash content and average HMF level were higher in locally produced honey products.In conclusion,the physical characteristics of overseas honey products were better than that of locally produced honey products.2.Glucose and maltose content in overseas honey products were lower,whereas the total carbohydrates,fructose and sucrose content were similar in both local and ’overseas honey productsIt was concluded that the average amount of total carbohydrates,fructose and sucrose were the same in both local and overseas honey products.However,the average amount of glucose and maltose in locally produced honey products were lower than that in overseas honey products.It could be concluded that the total carbohydrates and sucrose content meet the national standards.3.Analysis of amino acids content inlocal and overseas honey productsThe average content of total amino acids in locally produced honey products was comparatively lower,but there was no significant statistical difference in the total amino acids in both sources of honey products.Sixteen common peaks were identified in the fingerprints of free amino acids in all 32 batches of honey samples.Among them,the degree of similarity of 29 samples was greater than 0.960,when compared to the control.The samples were classified into five categories by cluster analysis,overseas honey products were mainly classified in the first and the third categories,while the locally produced honey products were mainly classified in the second and the first categories.This indicated that there were certain variations in both locally produced and overseas honey products,for which further study was worth to be conducted.4.The antioxidant activity(in vitro)of overseas honey products was betterBy comparing the results of three different antioxidant activity tests,the antioxidant activity in overseas honey products was better that that in locally produced honey products.It was concluded that there were significant statistical difference in the DPPH free radical scavenging activity and the superoxide cationscavenging activity in local and overseas honey products(p<0.05).5.The residues of veterinary drugs content in local and overseas honey products meet the national standardsAlthough no Amitraz was determined in all honey samples,its metabolite(2,4-xylidine)was detected.The amount of Amitraz and its metabolite in all 32 batches of honey products meet the international criteria,and the level of 2,4-xylidine was the same in both local and overseas honey products.Most of the samples were found to have flumethrin residues.The amount of flumethrin residues meets national standards and the level was the same in both local and overseas honey products.6.Determination of metal elements content in local and overseas honey productsThe average amount of zinc,copper,manganese and chromium were comparatively higher in locally produced honey products.The average iron content in both local and overseas honey products was similar.The level of zinc content in both local and overseas honey products meets the national standards.In conclusion,there were significant differences in the standards of physical characteristics,glucose and maltose content,antioxidant activity(in vitro)in both local and overseas honey products.In order to improve the overall honey products produced in China,further systemic study was worth to be conducted to investigate the reasons of these variations. |
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