Invertase activity in fresh and processed honeys

The enzymatic activities of 147 samples of commercially produced Spanish polyfloral and monofloral honeys are reported. Important variations in invertase activity and peroxide accumulation were determined to obtain objective information related to honey quality. Variations from 4.04 (Robinia pseudoacacia) to 25.61 g sucrose hydrolysed per 100 g h⁻¹ (SN) (Castanea sativa) and from 11.31 (Erica vagans) to 45.25 µg H₂O₂ g⁻¹ h⁻¹ (Hedysarum coronarium) were detected, with a range from 10.57 to 46.2 SN in polyfloral honeys. Honeys from Erica spp had different invertase activities—high for E cinerea (18.3 SN) and low for E vagans (8.36 SN). The different heating processes of honey have been evaluated to determine the best treatment for preserving invertase activity. The hydroxymethylfurfural content is not a sufficiently good indicator of the degree of deterioration of honey. Another objective was to assess the use of invertase activity in honey quality legislation. © 2000 Society of Chemical Industry     

枣花蜜的热稳定性研究

热处理会造成蜂蜜中生物酶活性的损失,同时还会生成有害物质羟甲基糠醛(HMF)。本文研究不同温度、时间下枣花蜜的热稳定性。采用分光光度法、铁氰化钾滴定法、紫外分光光度法分别测定枣花蜜中淀粉酶活性、蔗糖转化酶活性、HMF含量在不同热处理温度下随热处理时间的变化。结果表明:不同热处理温度下,枣花蜜中淀粉酶相对酶活、蔗糖转化酶相对酶活、HMF含量随热处理时间变化的关系式分别为[RAA]=exp(-kat),[RAI]=exp(-kit),[HMF]=[HMF0]exp(kht)。ka、ki、kh与热处理温度有关。最适宜热处理条件为温度45～50℃、时间8.1～1.7h。     

Kinetics of 3-deoxy-D-erythro-hexos-2-ulose in unifloral honeys

In this study, for the first time, the amount of 3-deoxy-D-erythro-hexos-2-ulose (3-DG) in fresh citrus and chestnut honeys was determined. 3-DG was measured as the corresponding quinoxalines after derivatization with orthophenylenediamine using reverse-phase high-performance liquid chromatography (RP-HPLC). Notwithstanding the freshness of the samples, high levels of 3-DG were detected in both honeys. The comparison of 3-DG and 5-hydroxymethylfurfural (HMF) concentrations, which was also quantified by RP-HPLC, showed that citrus honeys had the lowest amount of 3-DG (107 mg/kg) and the highest of HMF (16.7 mg/kg), while chestnut honeys had the opposite (398 and 1.2 mg/kg, respectively). During thermal treatment, different 3-DG and HMF trends were highlighted between the citrus and chestnut honeys; at the end, 3-DG formation was more favored with respect to HMF formation. Moreover, in citrus honeys, a good correlation between 3-DG and HMF levels was observed, which was not found in chestnut honeys, suggesting a role of the high pH values of these honeys on the degradation routes. The kinetic analysis showed the highest k value for 3-DG and HMF formation in chestnut and citrus honeys, respectively. The lowest Ea values related to 3-DG formation and the highest to HMF formation, indicating that the key intermediate 3-DG is easily formed at low temperatures, whilst the formation of HMF requires higher temperatures. For this reason, 3-DG seems to be an aging index rather than a thermal index and its use, at least for honeys at high pH values, together with HMF, could improve their quality assessment.     

单花蜜中羟甲基糠醛生成反应动力学研究

羟甲基糠醛含量是评价蜂蜜质量的重要指标,研究羟甲基糠醛(HMF)生成反应的影响因素显得尤为重要。本论文在不同温度下对金银花蜜、枸杞蜜、椴树蜜恒温热处理2～10h,采用紫外分光光度计法测定这三种单花蜜中HMF含量随热处理时间的变化。结果表明:这三种单花蜜中HMF的生成反应表观上皆遵循一级反应动力学模型[HMF]t=[HMF]0exp(kt),其反应速度常数与热处理温度之间的关系表观上皆符合阿累尼乌斯方程k=kfexp(-Ea/RT)。结论:在蜂蜜热处理过程中,HMF的生成是必然的,蜂蜜质量的降低程度取决于HMF生成反应进行的速度和时间,温度越高,质量下降越快;但由于品种的不同,蜂蜜质量下降的速度与温度的关系并不相同。     

Characterization of honey amylase

ABSTRACT:  The major α-amylase in honey was characterized. The optimum pH range and temperature were determined for the enzyme as 4.6 to 5.3 and 55 °C, respectively. The enzyme was stable at pH values from 7 to 8. The half-lives of the purified enzyme at different temperatures were determined. The activation energy for heat inactivation of honey amylase was 114.6 kJ/mol. The enzyme exhibited Michaelis–Menten kinetics with soluble starch and gave K _M and V _max values of 0.72 mg/mL and 0.018 units/mL, respectively. The enzyme was inhibited by CuCl (34.3%), MgCl₂ (22.4%), and HgCl₂ (13.4%), while CaCl₂, MnCl₂, and ZnSO₄ did not have any effect. Starch had a protective effect on thermal stability of honey amylase. Therefore, it might be critical to process or control the amylase in honey before incorporation into starch-containing foods to aid in the preservation of starch functionality. One step could involve heat treating honey with other ingredients, especially those that dilute and acidify the honey environment.     

Quality of honeys influenced by thermal treatment

Honey producers have been heating honeys at mild temperatures below 100 °C chiefly in order to prevent post-bottling crystallization. In this study, we aimed to determine the effects of thermal treatment on the HMF content of honeydew and floral honey during the isothermal heating process at mild temperatures. Water content, formol number, total acidity, pH value and minerals were also determined in both honey types as their characteristics differ with composition, which is able to affect the rate of HMF formation. Potassium content and pH value were found as the distinguishing properties and both were greater in honeydew honey than in floral honey (p<0.01). Honeydew and floral honey samples were heated at 75, 90 and 100 °C for 15-90 min and analysed for HMF content by HPLC-RP. The Arrhenius model was used to calculate reaction rate constants and activation energies which were found to be different for each of the honey types. Heating at 90 °C for up to 90 min in floral honeys and up to 75 min in honeydew honeys did not cause a significant increase of HMF and not exceed the threshold level of 40 mg kg⁻¹. Our results show that the excessive HMF content might be related to primitive storage conditions rather than overheating.     

Quorum sensing inhibitory and antimicrobial activities of honeys and the relationship with individual phenolics

Quorum sensing (QS) inhibitory activity of 29 unifloral honeys was evaluated using the bacterial model Cromobacterium violaceum. The tested honeys were able to inhibit the production of acyl-homoserine lactones (AHLs) produced by C. violaceum at 0.1 g/ml. However, chestnut and linden honey samples showed the highest inhibitory activity, while orange and rosemary were less effective in inhibiting QS. When honey samples from the same floral origin obtained from different geographical regions were compared, they showed similar QS inhibitory activity. Thus, one of the factors which influence the inhibitory activity could be derived from the floral origin, independently of the geographic location. It was observed that unifloral honey samples showed “non-peroxide” anti-QS activity, which was not linearly correlated with total and individual phenolic compounds. The obtained results showed that the preservative properties of honey could be due to both the antimicrobial properties and the QS inhibitory capacity.     

Unifloral honeys of the province of Buenos Aires,Argentine

Samples of 63 unifloral honeys of the province of Buenos Aires, Argentina, from Eucalyptus spp, Lotus spp, Helianthus annuus, Melilotus albus, Brassicaceae, clovers other than Lotus and Melilotus, and Sagittaria montevidensis, were obtained by cold extraction at the laboratory. The frequencies of occurrence of pollen types, and the moisture, hydroxymethylfurfural, ash, acidity and proline contents were determined. Electrical conductivity, pH and colour were also analysed. Honey presented a high percentage (about 40%) of unifloral honey. The most frequent unifloral honeys were from Eucalyptus spp, Lotus spp and Helianthus annuus. Samples had a low pollen diversity with six to 19 pollen types, the most important nectariferous taxa being those that characterized the unifloral honeys. All samples presented moisture, hydroxymethylfurfural, ash and free acidity contents according to international standards. The colour of the honey was from water white to light amber, and all samples had a very low ash content. Significant differences at the 5% level in the hydroxymethylfurfural content, electrical conductivity, colour and proline content were observed among honeys from different floral origins. However, a high variability between samples from the same floral origin was observed, indicating that other factors such as accompanying pollen and geographical origin affect the physicochemical characteristics of honey. Copyright © 2005 Society of Chemical Industry     

Purification of Amylase from Honey

The major amylase in honey was concentrated by ultrafiltration, isolated by ultracentrifugation and gel filtration, and purified by ion‐exchange chromatography. The amylase activity was in the flow‐through fraction of the anion‐exchange column, suggesting a high isoelectric point (>7.4) for the enzyme. The enzyme fraction from the anion‐exchange chromatography was loaded onto a cation‐exchange column, and the amylase activity was eluted as a single band at 50 mM NaCl. The purification factor after this step was 531‐fold. The purified enzyme was an a‐amylase, as determined by thin‐layer chromatography, with a molecular weight of 57000 Da according to sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). The results supported the concept that amylase in honey had a high degree of similarity with bee amylase.     

Total phenolic content,antiradical, antioxidant and antimicrobial activities of Rhododendron honeys

Fifty Rhododendron honey samples obtained from Black Sea Region of Turkey were screened for total phenolic content by the modified Folin–Ciocalteu method, for potential antioxidant activity using phosphomolybdenum assay and by the 1,1-diphenyl-2-picryl hydrazyl (DPPH) method for antiradical activity. The antimicrobial activity was studied by the agar diffusion method, using eleven bacteria and two yeasts.     

Effects of honey types and heating treatment on the textural,thermal, microstructural,and chemical properties of glutinous rice flour gels

Hardening issue in starch-based products that arises during storage, is ascribed to the long-term starch retrogradation which involves the recrystallisation of amylopectin. Present study aimed to delay storage hardening with the addition of high diastase honey bee honey (HBH) and low diastase kelulut bee honey (KBH) into glutinous rice flour (GRF) gels. As compared to KBH, retardation of texture deterioration by HBH was more prominent as evidenced by the significantly (p < .05) lowest hardness and rate of hardening of GRF gel added with HBH (honeygel) throughout the 7-day storage. Heated honey and sugar solution did not reduce gel hardness that gel weakening was associated to the naturally occurring diastase in raw honey. Hence, only conventional GRF gel (congel), GRF gel added with KBH (kelugel) and honeygel were assessed for intrinsic viscosity, thermal, microstructural and chemical properties. The results were substantiated by the significantly (p < .05) lowest intrinsic viscosity (62.93 mL/g) and thermal enthalpy (333.7 J/g) of honeygel. A weak gel network structure was illustrated in honeygel with the significantly (p < .05) highest pore diameter (125.27 μm). In conclusion, the GRF gel has successfully demonstrated the potential of honey diastase in inhibiting the long-term retrogradation which could solve the industrial real problem.     

Honey Amylase Activity and Food Starch Degradation

ABSTRACT: Honey amylase was evaluated for potential to degrade food starch and cause viscosity loss. Honey was assayed for amylase activity with diastase number (DN). A viscosity assay, developed with unmodified waxy maize starch, measured honey amylase rate of viscosity decrease (RVD). The relationship between DN and RVD was linear (R²= 0.98). Modified waxy maize starches showed resistance to honey amylase. Honey heat treatment at 85 °C reduced amylase activity 2 to 5 DN, but confirmed enzyme heat resistance. Optimum pH for honey amylase was confirmed at pH 5.3 to 5.6. RVD activity declined as pH decreased. Preventing food viscosity loss involved selecting honey with lowered DN and/or using modified starches. Complete control of activity was achieved in barbecue sauce at pH < 3.9.     

Geographical discrimination of honeys by using mineral composition and common chemical quality parameters

Sixty honey samples from six different production zones of the provinces of Salamanca, Zamora and Cáceres (western Spain) were analysed for 13 common legal physicochemical parameters and 17 mineral elements (13 cations and four anions) in order to test for their geographical classification. Application of linear stepwise discriminant analysis to a number of variables made of a selection of analytical results and their simple mathematical functions allowed, firstly, discrimination between honeys from all six zones and, secondly, discrimination between honeys from the three zones of the province of Salamanca. The most discriminant variables selected for the six zones were 10 in number, a combination of three physicochemical parameters and nine elements, with a result of 91.38% of correctly classified samples; for the three zones of the province of Salamanca, regarded with special interest in our study, six variables were selected (made of eight elements) with a result of 97.07% of correctly classified samples. © 2000 Society of Chemical Industry     

Colour characterisation of thyme and avocado honeys by diffuse reflectance spectrophotometry and spectroradiometry

The colour of 23 thyme and 13 avocado honeys was assessed by tristimulus colorimetry based on their spectra, using diffuse reflectance spectrophotometry and spectroradiometry, with the application of the equations for the uniform colour space CIELAB proposed by the Commission Internationale de lEclairage. The best results for distinguishing between the two types of honey have been obtained from spectroradiometry rather than from spectrophotometry. With the discriminant analysis it has been revealed that the two honey types studied are better characterised when considering lightness, chroma ( ) and hue angle as variables (94% correct), with and the hue being the parameters with the highest discriminating power.     

Microbial Decontamination of Honey of Indian Origin Using Gamma Radiation and Its Biochemical and Organoleptic Properties

ABSTRACT:  Gamma radiation is known to inactivate microorganisms in various foods and thus ensures their microbial safety. In the present study, process parameters were standardized for achieving microbial decontamination of honey of Indian origin. Study was also carried out to examine the effect of gamma radiation treatment on the biochemical, antioxidant, antibacterial, and organoleptic attributes of the honey. A 15 kGy dose of gamma radiation was found to be sufficient for complete microbial decontamination of honey including spores, thus improving its microbial safety without affecting the quality attributes.     

Phenolic profile and antioxidant properties of Polish honeys

The phenolic components of honeys have great participation in their nutritional value and antioxidant activity. Moreover, phenolic components are promising markers for the determination of botanical and geographical origin of honey. The purpose of the present work was to study the antioxidant activity and profiles of phenolic acids and flavonoids of honeys of various origins. The total phenolic content of honeys varied from 4.46 to 15.04 mg of gallic acid equivalents per 100 g of product and the total phenolic acid content determined chromatographically varied from 201.05 to 2089.08 μg per 100 g of product. Buckwheat honey exhibited the highest antioxidant activity and contained the highest total phenolic amount, whereas rape honey exhibited the lowest values in this respect. Moreover, the buckwheat honey contained the highest amount of phenolic acids. There were significant linear correlations between total phenolic content and antioxidant activity of honey extracts in the reaction with DPPH^? (1,1‐diphenyl‐2‐picrylhydrazyl) and ABTS^{? +} (2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid)) free radicals. In most samples, p‐coumaric acid was the dominant phenolic acid (39.1–677.2 μg per 100 g). The honeys also contained considerable amount of gallic acid (6.0–913.8 μg per 100 g). Among flavonoids naringenin was predominant in the most studied honey samples.     

Using flavonoids, phenolic compounds and headspace volatile profile for botanical authentication of lemon and orange honeys

This study evaluates the usefulness of flavonoids (naringenin, hesperetin, chrysin, galangin, kaempferol, luteolin, pinocembrin, and quercetin) and phenolic acids (caffeic acid and p-coumaric acid) together with 37 volatile compounds in the differentiation between lemon blossom honey (Citrus limon) and orange blossom honey (Citrus spp.). The total content of flavonoids and phenolic acids is twice as high in lemon honey (6.20 mg/100 g) as in orange honey (3.64 mg/100 g); naringenin and caffeic acid were the main compounds in all cases. Hesperetin, a floral marker of citrus honey, was not significantly different for the two types of honey. A multivariate PLS2 analysis showed that some volatile compounds such as, 4 lilac aldehydes and bencenacetaldehyde (all abundant in orange honey) were negatively correlated with 4 flavonoids: pinocembrin, chrysin, naringenin and quercetin, and caffeic phenolic acid (all abundant in lemon honey). Moreover, the last 5 compounds were positively correlated with: 6 alcohols, 2 ketones, acetaldehyde and furanmethanol. This is a first approach to employ all of these compounds together with appropriate statistical techniques to differentiate between two varieties of citrus honey, and therefore it could be an interesting tool for their authentication.     

枣花蜜和荞麦蜜中葡萄糖氧化酶的活性及热稳定性研究

分别测定了不同地理源的枣花蜜和荞麦蜜中葡萄糖氧化酶(glucose oxidase,GOD)的活性。在测定的枣花蜜样品中陕西佳县枣花蜜GOD活性最高,为(0.161±0.002)U/g,山西吕梁枣花蜜GOD活性最低,为(0.007±0.001)U/g;荞麦蜜中四川西昌荞麦蜜GOD活性最高,为(0.112±0.001)U/g,山西晋北荞麦蜜GOD活性最低,为(0.007±0.001)U/g。结果表明,蜂蜜植物源不同,GOD活性不同;植物源相同时,地理源不同,蜂蜜中GOD活性差异也较大。对GOD的热稳定性研究表明,枣花蜜中的GOD在70℃加热90min活性完全损失,荞麦蜜GOD活性仍有部分残存,表明四川西昌荞麦蜜中的GOD热稳定性较陕西佳县枣花蜜高。