Direct potentiometric determination of diastase activity in honey

A novel method for the determination of diastase activity is reported. The method is based on a direct potentiometric measurement of triiodide ion that is released when a starch-triiodide complex is hydrolysed by honey diastase. The increase of free triiodide ion concentration in a sample is found to be directly proportional to the diastase activity of the sample. A response mechanism of the platinum redox electrode is proposed, allowing a calculation of the diastase activity factor (F). The sensor and analyte parameters, including F, were obtained by least squares fitting of potentiometric data using the optimisation function of the Solver add-in of Microsoft Excel. The values of F obtained by the new direct potentiometric method were compared with those obtained using the standard Phadebas method (DN values), and the two values were found to agree within experimental error. Finally, the diastase activity of nine varieties of honey was determined using the novel method developed here.     

Effects of prolonged heating on antioxidant activity and colour of honey

The kinetics of changes in total antioxidant activity as assessed by DPPH radical and brown pigment formation (BPF) in honey heated at different temperatures (50, 60 and 70 °C) for up to 12 days were studied. Antioxidant activity and BPF increased with treatment temperature and time. BPF increased following zero-order kinetics with the activation energy value of 122 kJ/mol⁻¹ at 50–70 °C. However, antioxidant activity variation showed different trends according to heating temperatures following second-order, first-order and zero-order kinetics at 50, 60 and 70 °C, respectively. Heating of honey at 70 °C was found to be more effective than 50 and 60 °C for both two parameters. The results demonstrated that antioxidant activity was correlated with increased browning of the samples.     

Physico-chemical properties in honey from different regions of Turkey

The present study was undertaken to determine the physico-chemical parameters of honey samples obtained from retailers in Marmara Region (Site 1) and East Anatolia (Site 2) of Turkey. The 70 samples were analysed for parameters including moisture, total acidity, diastase activity, hydroxymethylfurfural (HMF), invert sugar, sucrose, ash, commercial glucose and starch. 10 of 70 (14.3%) honey samples were of unacceptable quality based on recommended criteria of moisture (3 of 70, 4.29%), diastase activity (3 of 70, 4.29%), HMF (2 of 70, 2.86%), invert sugar (4 of 70, 5.71%) and sucrose (2 of 70, 2.86%) by Turkish Food Codex and European Commission Regulation. The results of study indicated that 85.7% of honey samples were at good quality. It is important that the essential precautions should be taken to ensure standardisation and rationalisation of beekeeping techniques, manufacturing procedures and storing processes to improve honey quality.     

Honey Flavonoids,Natural Antifungal Agents Against Candida Albicans

Candida albicans is the most prevalent fungal pathogen in humans. In this study, flavonoids from unprocessed multifloral honey were extracted and investigated their anticandidal activity in vitro. These results indicated that honey flavonoids inhibited Candida growth; however, they did not kill the yeasts and did not directly affect the cytoplasmic membrane. The viability tests of cells yeast with the fluorescent probe Sybr green I in combination with propidium iodide suggested that antifungal activity of honey flavonoids depended on their relative lipophilic properties and that they may reach a possible intracellular site of action without compromising membrane-associated functions.     

Simulation of heating uniformity in a heating block system modified for controlled atmosphere treatments

Reliable and repeatable insect thermal mortality data rely on the performance of a heating device. Computer simulation has been widely used to optimize structures, design parameters and process conditions. To improve the temperature uniformity of a heating block system (HBS), a computer model was developed using finite element software COMSOL. Good agreement was obtained between the simulated and experimental block surface temperatures at three positions of the HBS and three heating rates. The validated computer model was further used to predict the effects of heating rates, the position of test insects and the addition of gases on the block and air temperature distributions. Simulation results showed that increasing heating rate reduced heating uniformity. The position of test insects in the treatment chamber largely affected their heating rate, with a position closer to the surface of the heat block providing a better temperature match between test insects and the HBS. When gas was added, block temperatures within the treatment chamber, particularly near the gas inlet, were influenced by gas speeds, temperatures and the gas channel design. The heating uniformity in the treatment chamber of the HBS was improved by heating the gas before adding it to the HBS, by routing the gas channel through the heating block to preheat the gas, and by using a relatively slow gas speed. The simulation results demonstrated that the validated computer model could be a reliable tool to evaluate the heating performance of the HBS for studying insect thermal death kinetics and optimize treatment conditions for the HBS when modified to include controlled atmospheres.     

Amaranth starch-rich fraction properties modified by extrusion and fluidized bed heating

Today amaranth is a promising food source yet its technological properties are not well known. The modification of some properties of an amaranth starch-rich fraction by a controlled heating is studied. This fraction was obtained by the differential milling of Amaranthus cruentus grains.Tests were performed by both fluidized bed and extrusion heating, according to a factorial experimental design of two variables: temperature and moisture, at three levels 150-170-200 °C and 120-160-200 g/kg wb, respectively. Effects were evaluated by the ANOVA method. As responses, solubility and water absorption, amylographic and dynamic rheological properties, crystallinity, granular integrity and resistant starch content were evaluated. Flours obtained from samples heated by fluidized bed gave aqueous dispersions with high consistencies when cooked, and they had low solubility in water and preserved part of the starch crystalline structure. Flours obtained from extrusion-heated samples gave very high solubility in water but had lower consistency of the aqueous dispersions when cooked, and they showed a complete loss of the crystalline and granular structure.By applying each of the two heating processes, it was possible to modify, according to selected targets, the amaranth starch-rich fraction, what would allow to obtain pre-cooked amaranth flours with a wide range of hydration and rheological properties.     

Effect of honey high-temperature short-time heating on parameters related to quality, crystallisation phenomena and fungal inhibition

The effect of a unique high-temperature short-time heating treatment on natural honeys to produce both a fungi inhibition and a crystallisation delay simultaneously was evaluated. As responses to treatments, hydroxymethylfurfural content, diastase activity, fungi and yeast development, and crystallisation starting time were measured. Besides, moisture, fructose, glucose and acidity were determined.Heating can produce a decrease in honey quality, which is made evident by a simultaneous reduction in the diastase activity, referred to as diastase number, and an increase in the hydroxymethylfurfural content. Considering the minimum admissible diastase number and the maximum admissible hydroxymethylfurfural content values, according to honey present regulations, several thermal treatment tests were performed on selected honey samples without exceeding those values. Tested conditions were: heating between 140°C and 80°C at times between 60 to 15 s and 30 to 10 s during both transient and isothermal heating stages, respectively. In all tests the diastase number was the most heat-sensitive parameter. The boundary thermal treatment, assumed as the most severe conditions able to produce a permissible quality loss, was found to be 140°C, during 15 s in the transient stage and 30 s in the isothermal stage. Beyond those values, an unacceptable diastase number reduction was produced. On the other hand, it was found that a 80°C heating, during 60 and 30 s in transient and in isothermal stages, respectively, destroyed all microorganisms responsible for quality damage without spoiling honey. This was considered to be the mild or more suitable treatment condition. Twenty-six naturally contaminated honey samples heated at such conditions showed a null capacity to develop fungi and yeast. Besides, according to the storing temperature, and moisture and glucose contents, a crystallisation beginning delay between 4 and 9 weeks was obtained on four selected honeys, according to the thermal treatment applied. Several parameters previously proposed that characterise honey crystallisation tendency as fructose/glucose, glucose/moisture and (glucose-moisture)/fructose ratios were related to the time in which crystallisation starts. A new parameter, (fructose/glucose)·moisture was proposed.     

Antibiotic Residues in Iranian Honey by Elisa

The aim of this study was to determine antibiotic residues in honey collected from northern part of Iran. The presence of antibiotic residues in honey may be harmful to human health. In this study, the enzyme linked immune assay method was used to investigate of antibiotic residues in honey samples (n = 135) collected randomly from Qazvin Province, Iran. The analyzed antibiotics included enrofloxacin, penicilin, chloramphenicol, gentamicin, tylosin, tetracycline, and sulfonamide. Result show that the range of antibiotic radiuses value was 0.0–72.1 ng/g, besides; the highest percentage of antibiotic residues in honey samples was the enrofloxacin (20.7%). The highest and lowest mean contamination (ng/g) belonged to enrofloxacin (10.8 ± 1.6) followed by Penicillin (4.4 ± 2.9), and chloramphenicol (0.1 ± 0.1). The highest level of antibiotic residues (71.85%) was seen in honey samples collected during the autumn season (P < 0.05).     

淀粉酶在真假蜂蜜中的区别

针对蜂蜜掺假和造假的问题,文中对真、假蜂蜜中的蛋白质含量、淀粉酶活性及淀粉酶同工酶谱带差异进行测定分析。结果表明,天然蜂蜜在低温条件下可以在近1个月的时间内保持其蛋白质含量和酶值基本不变,但是在高温的条件下,随着贮存时间的延长,其蛋白质含量和酶值就会明显下降。而假蜂蜜其蛋白质含量和酶值均没有明显的变化。同工酶凝胶电泳结果也表明,真、假蜂蜜中淀粉酶同工酶谱带明显不同。因此,通过跟踪测定蜂蜜中蛋白质含量、淀粉酶值变化、淀粉同工酶谱带可以检测蜂蜜的真假及其质量变化。     

Effect of heating conditions of grape seeds on the antioxidant activity of grape seed extracts

This study was carried out to evaluate the effect of heating and physical conditions of grape seeds on the antioxidant activity of their extracts. Two forms of grape seeds, whole and powdered forms, were heated at four different temperatures −50, 100, 150 and 200 °C. After heating, grape seeds were extracted with 70% ethanol (0.1 g grape seed/10 mL of 70% ethanol), and total phenol contents (TPC), radical scavenging activity (RSA) and reducing power of the extracts were determined. Thermal treatment of grape seed increased the antioxidant activity of extracts. The maximum TPC and RSA of whole grape seed extract (WGSE) were achieved when the seeds were heat-treated at 150 °C for 40 min, while that of powdered grape seed extract (PGSE) were at 100 °C for 10 min, and were greater than that of the non-treated control. Also, the reducing powers of WGSE and PGSE slightly increased at the conditions. According to the GC-MS analysis, several low-molecular-weight phenolic compounds such as azelaic acid, 3,4-dihydroxy benzoic acid, and o-cinnamic acid were newly formed in the WGSE heated at 150 °C for 40 min. There were slight differences in the kinds of phenolic compounds between non-heated and heated GSE. In HPLC analysis, the contents of gallocatechin gallate and caffeine in GSE significantly increased by heat treatment. These results indicated that antioxidant activity of GSE was affected by heating conditions (temperature and time) and physical conditions of grape seeds at the time of heat treatments.     

蜜柚叶黄酮的提取及其抗氧化与降尿酸活性研究

研究蜜柚叶总黄酮的提取工艺、抗氧化活性及其对黄嘌呤氧化酶的抑制活性。采用正交实验对蜜柚叶黄酮的提取工艺进行优化,探究蜜柚叶黄酮的最佳提取工艺条件。并通过DPPH自由基、羟自由基及超氧阴离子清除实验探究蜜柚叶黄酮对自由基离子的清除活性;通过黄嘌呤氧化酶活性抑制实验初步判断其降尿酸功效。结果表明:蜜柚叶黄酮的最佳提取条件为料液比1:30（g/mL）、乙醇浓度80%、浸提时间6 h、浸提温度80℃,黄酮得率为12.41 mg/g。蜜柚叶黄酮对DPPH自由基、羟自由基及超氧阴离子均表现出较强的清除活性,IC50值分别为:1.47、1.04、1.49 mg/mL。同时,蜜柚叶黄酮对黄嘌呤氧化酶抑制活性的IC₅₀值为4.8 mg/mL。      

蜂蜜中铅原子荧光光谱测定方法的改进

为改进蜂蜜中的铅的检测方法，用酸性活性炭吸附分离铁氰化钾试剂中铅，以pH计控制消化液的酸度。在最佳的条件下，铅在0．00—40．00μg/L范围内线性良好（r=0．9994）；方法检出限为0．21μg／L；相对标准偏差为4．1％-5．0％；样品加标回收率为93．2％-109．4％。该方法简单，快速，重现性好，灵敏度高，检出限低，结果令人满意。     

HPLC法测定蜂蜜中槲皮素和山奈酚

目的建立同时测定蜂蜜中槲皮素和山奈酚含量的方法。方法以Hpersil BDS C18(250 mm×4.6 mm,5μm)为分析柱,流动相为甲醇 0.4%磷酸水溶液(45 55)并用三乙胺调节pH至4.2,流速为1.0 ml/min,检测波长为375 nm。结果槲皮素的线性范围为0.045-2.25μg,山奈酚的线性范围为0.052-2.600μg,相关系数均为0.999 1;平均回收率分别为95.9%,97.6%。5种蜂蜜中均含微量槲皮素(18.62-189.26μg/g)和山奈酚(5.97-22.54μg/g),其含量与蜜源有关,桉树蜜中槲皮素含量最高(189.26μg/g),红树林蜜中山奈酚含量最大(22.54μg/g)。结论该方法简便、准确,可以用于同时测定蜂蜜中槲皮素和山奈酚的含量。     

流加法发酵生产较高酒精度蜂蜜酒

为生产较高酒精度的纯发酵蜂蜜酒,对流加法发酵蜂蜜酒的工艺进行了研究。以市售天然纯蜂蜜为主要原料,经稀释、巴氏灭菌、调整发酵液成分后,采用活性干酵母混合发酵,得到了酒精度较高,口感、色泽、风味都较好的纯发酵蜂蜜酒。通过正交试验确定其最佳工艺参数为:酵母菌接种量1.2‰,分别在发酵第5d、6d共流加蜂蜜20mL,发酵14d得到16.8%vol以上的蜂蜜酒。     

Honey melanoidins: Analysis of the compositions of the high molecular weight melanoidins exhibiting radical-scavenging activity

Size-exclusion chromatography (SEC) and activity-guided fractionation of honeys allowed the isolation of high molecular weight brown compounds, ranging in size from 66 to 235 kDa that exhibited peroxyl radical-scavenging activity. Their concentrations, antioxidant activity and degree of browning increased after heat-treatment of honeys, suggesting that they represent melanoidins. Chemical analysis of melanoidins demonstrated the presence of proteins, polyphenols and oligosaccharides. Heat-treatment caused an increased incorporation of phenolics into high molecular weight melanoidins and drastically decreased the protein content in these fractions with a concomitant appearance of high molecular weight protein–polyphenol complexes of reduced solubility. LC–ESI–MS demonstrated the presence of oligosaccharide moieties, supporting the postulated origin of melanoidins. The changes in the phenolic content of melanoidins from heated honeys were strongly correlated with their oxygen radical absorbance capacity (ORAC) values (R = 0.75, p < 0.0001), indicating that polyphenols contribute to the antioxidant activity of melanoidins. In summary, honey melanoidins are multi-component polymers consisting of protein–polyphenol–oligosaccharide complexes. A direct interaction between polyphenols and melanoidins resulted in a loss or gain of function for melanoidin antioxidant activity.     

液液萃取-液相色谱-串联质谱法测定蜂蜜中氯霉素

目的建立液相色谱-串联质谱法检测蜂蜜中氯霉素残留量的方法。方法试样前处理采用液液萃取,以甲醇 水(71 29体积分数)为流动相,用Zorbax Eclipse XDB C18柱进行分离,以氘代氯霉素作为内标,采用负离子方式,液相色谱-电喷雾串联质谱法进行测定。结果平均回收率为93.0%-98.2%,相对标准偏差小于8%。采用空白蜂蜜基质制作校正曲线,蜂蜜中氯霉素检测的线性范围为0.01-1.00μg/kg,定量检测下限为0.01μg/kg。结论方法灵敏、准确、快速,能满足蜂蜜中氯霉素的监督检测。     

高效毛细管电泳法测定蜂蜜中单糖的含量

采用高效毛细管电泳技术，经α－萘胺衍生化，以鼠李糖作内标物，分别对五种蜂蜜中葡萄糖和果糖的含量进行了测定，获得满意结果。     

Evolution of acid phosphatase activity of honeys from different climates

Acid phosphatase is an enzyme of honey whose values have been related to honey’s fermentation. In this work, we have studied the evolution, throughout thirty months, of acid phosphatase activity on honey samples originating in continental and oceanic areas. We have also researched the influence of induced granulation and pH on acid phosphatase activity evolution. Acid phosphatase activity has been determined by measuring, at 400 nm, 4-nitrophenol formed after the hydrolysis, at acid pH, of 4-nitrophenylphosphate in the presence of acid phosphatase. From the start, acid phosphatase activities have been higher in honeys from oceanic climate. Similar trends of evolution of acid phosphatase activity have been found in both honeys from continental and oceanic climates. In the end of the study, 100% samples showed a decrease of acid phosphatase activity. Induced granulation does not modify the trend of acid phosphatase activity evolution, although this technological process has an influence on the time at which changes within the evolution occurs. pH of samples has demonstrated to have a strong influence on the activity of acid phosphatase, so that the higher the pH, the lower the decrease of acid phosphatase activity. In honeys originated from continental climate area, pH and acid phosphatase activity have been correlated throughout the study.     

Antibacterial activity of hen egg white lysozyme modified by thermochemical technique

Lysozyme is an important component of egg white with antibacterial properties especially against Gram-positive bacteria. Research indicates that the range of lysozyme activity may be extended thanks to chemical or physical modifications. The purpose of the study was to determine the effectiveness of antibacterial action against selected strains of bacteria of lysozyme modified by the thermochemical technique. Our investigations indicated a possibility of extending the range of lysozyme activity using modification. We found that under the adopted conditions modification promotes an increased polymerisation of lysozyme. It was observed that the temperature and time of modification have an effect on the content of the forming polymers. It was found that the application of lysozyme modification leads to an increase in its antibacterial activity in comparison to the activity of lysozyme monomer. The experiments have shown that the used lysozyme preparations demonstrate different activity in relation to different types of bacteria. The observed increase in antibacterial activity of modified lysozyme preparations against Gram-negative bacteria were not associated with a decrease of that activity against Gram-positive bacteria. The greatest reduction of growth of the examined Gram-negative bacteria species was recorded for the preparation which contained the highest quantity of dimer (34–37.6%). A more effective action against bacteria Staphylococcus epidermidis was observed for preparations containing 25–27% of dimer.