Stability of Bisphenol A (BPA) in Oil-In Water Emulsions under Riboflavin Photosensitization

Effects of riboflavin photosensitization on the degradation of bisphenol A (BPA) were determined in oil-in-water (O/W) emulsions containing ethylenediaminetetraacetic acid (EDTA) or sodium azide, which are a metal chelator or a singlet oxygen quencher, respectively. Also, the distribution of BPA between the continuous and dispersed phases in O/W emulsions was analyzed by high-performance liquid chromatography (HPLC). The concentration of BPA in O/W emulsions significantly decreased by 38.6% after 2 h under visible light irradiation and in the presence of riboflavin (P < 0.05). Addition of EDTA and sodium azide protected the decomposition of BPA significantly in a concentration dependent manner (P < 0.05), which implies both transition metals and singlet oxygen accelerate the photodegradation of BPA in O/W emulsions. Approximately 21.7% of the BPA was distributed in the 2.5% (w/v) dispersed lipid particles and 78.3% was in the continuous aqueous phase of the emulsions. The amount of BPA in aqueous phase decreased faster than the amount of BPA in the lipid phase during riboflavin photosensitization (P < 0.05). Thus, the BPA in the aqueous phase was the major target of riboflavin photodegradation in O/W emulsions. Practical Application: Concentration of BPA, an endocrine disrupting chemical, was decreased significantly in oil-in-water emulsions under riboflavin and visible light irradiation. BPA in continuous aqueous phase was major target of riboflavin photosensitization. However, BPA was distributed more densely in lipid phase and more protected from riboflavin photosensitized O/W emulsions. This study can help to decrease the level of BPA in foods made of O/W emulsions containing riboflavin, which could be displayed under visible light irradiation.     

Kinetics for Singlet Oxygen Formation by Riboflavin Photosensitization and the Reaction between Riboflavin and Singlet Oxygen

ABSTRACT: The formation of singlet oxygen by riboflavin and the kinetics and mechanisms of riboflavin degradation in aqueous solution under light were determined. The singlet oxygen formation rate by riboflavin was 2.31 μmole oxygen/mL headspace/h of serum bottle. The degradations of riboflavin were 66% in D₂O and 40% in H₂O, respectively, under light after 24 h. The results indicate that singlet oxygen is involved in riboflavin destruction under light. The riboflavin destructions were 94.0% and 15.7% with 0 mM or 160 mM ascorbic acid, respectively, under light after 96 h. The reaction rate between riboflavin and singlet oxygen was 1.01 × 10¹⁰/M/s, which is a diffusion-controlled reaction rate. This explains the extremely fast degradation of riboflavin in foods under light. Ascorbic acid and sodium azide reduce the degradation of riboflavin under light with different quenching mechanisms. Ascorbic acid quenched both singlet oxygen and excited triplet riboflavin. Sodium azide quenched only the singlet oxygen in riboflavin solution with a quenching rate of 1.547 × 10⁷/M/s. With the involvement of both the Type-I and Type-II mechanisms in the riboflavin degradation under light, singlet oxygen quencher alone could not protect the riboflavin from degradation completely. Addition of ascorbic acid can protect riboflavin oxidation in foods exposed to light.     

Changes of Headspace Volatiles in Milk with Riboflavin Photosensitization

ABSTRACT:  Effects of fluorescent light, riboflavin, ascorbic acid, sodium azide, and butylated hydroxyanisole (BHA) on the volatiles in milk at 4 °C were determined using a combination of headspace-solid phase microextraction (HS-SPME), gas chromatography (GC), and mass spectrometry (MS). Pentanal, hexanal, heptanal, and dimethyl disulfide were formed only in the milk stored under light and increased significantly as the duration of light exposure increased from 0 to 8 h and the concentration of added riboflavin increased from 5 to 50 ppm ( P  < 0.05). As fat content in milk increased, peak areas of pentanal, hexanal, and heptanal increased significantly ( P  < 0.05) while those of dimethyl disulfide did not change significantly ( P  > 0.05). Sodium azide prevented the formation of dimethyl disulfide in milk, implying that dimethyl disulfide can be formed through singlet oxygen oxidation (type II pathway). Addition of ascorbic acid and BHA reduced the formation of hexanal, heptanal, and dimethyl disulfide significantly ( P  < 0.05). Generation mechanisms of pentanal seem to be different from those of hexanal and heptanal in milk. Both singlet oxygen oxidation (type II pathway) and free radicals (type I pathway) play important roles in the formation of light-induced volatiles in milk.     

Effects of Riboflavin Photosensitized Oxidation on the Volatile Compounds of Soymilk

ABSTRACT: Soymilks with or without added riboflavin in serum bottles were stored under light or in dark at 20 °C. The headspace oxygen and volatile compounds were determined by gas chromatography. Riboflavin had significant effects on the headspace oxygen depletion and volatile compounds formation in soymilk under light ( P < 0.05). Riboflavin did not have significant effects on the formation of volatile compounds and the depletion of headspace oxygen in dark ( P > 0.05). The volatile compounds increased under light, but not in dark as the added riboflavin increased. Storage temperature at 4 °C or 20 °C did not have significant difference in the effect of riboflavin on the headspace oxygen depletion in soymilk under light. Hexanal, an important beany flavor compound, was identified as the major volatile compound in the riboflavin photosensitized soymilk. Singlet oxygen oxidation was involved in the formation of volatile compounds in soymilk under light. Hexanal could be formed by singlet oxygen oxidation. Ascorbic acid, a quencher for singlet oxygen and the excited triplet sensitizer, significantly inhibited the formation of hexanal and total volatiles in soymilk under light.     

ESR Study of the Singlet Oxygen Quenching and Protective Activity of Trolox on the Photodecomposition of Riboflavin and Lumiflavin in Aqueous Buffer Solutions

ABSTRACT:  Singlet oxygen quenching activity of Trolox, a water-soluble derivative of tocopherol, was studied by electron spin resonance (ESR) spectroscopy in a buffer solution (pH 7.4) containing methylene blue (MB), 2,2,6,6-tetramethyl-4-piperidone (TMPD) after light illumination for 30 min. Trolox at the concentration of 125 μM quenched 89.1% singlet oxygen in the system. Trolox showed significantly higher singlet oxygen quenching activity than ascorbic acid in the buffer solution ( P  < 0.05). Riboflavin in phosphate buffer solutions was degraded very fast under fluorescent light illumination. The photodegradation rate of riboflavin at pH 8.5 was significantly higher than pHs 4.5 and 6.5 ( P  < 0.05). Lumiflavin was also degraded under the fluorescent light illumination, but its degradation rate was much lower than that of riboflavin under the same light intensity. Unlike riboflavin, the rate of lumiflavin photodegradation was the greatest at pH 4.5 and followed by pHs 6.5 and 8.5, in a decreasing order. Trolox greatly protected the photodegradation of riboflavin and lumiflavin. The protective activities of Trolox against the photodegradation of riboflavin and lumiflavin were also pH dependent. The treatments of 5 mM Trolox in the buffer solutions of pHs 8.5 and 6.5 exhibited 56.1% and 31.7% protection of riboflavin against degradation during 120 min light illumination, respectively. The treatments of Trolox at the concentrations of 1, 3, and 5 mM in the buffer of 6.5 exhibited 14.8%, 58.4%, and 81.4% protection of lumiflavin against degradation during 24 h light illumination, respectively.     

Effects of riboflavin photosensitization on daidzein and its photosensitized derivatives

Photosensitized compounds from daidzein were studied in a riboflavin model system under visible light irradiation by high-performance liquid chromatography (HPLC). As the period of light irradiation increased, concentration of daidzein decreased significantly (P < 0.05) and new peaks of daidzein derivatives were observed and changed during photosensitization. Three new peaks from photosensitized daidzein were tentatively identified as 7-, 3', 4'-trihydroxyisoflavone (or 3'-hydroxydaidzein) and 2 dimmers of daidzein by a combination of HPLC-mass spectrometry (MS) and retention times of standard compounds by HPLC. Addition of sodium azide and removal of headspace oxygen treatment affected the formation of newly formed peaks. The type I pathway of riboflavin photosensitization played more important roles than type II pathways on the formation of daidzein derivatives. Practical Application: Isoflavones are important phytochemicals found in soy foods. Generally, many foods containing soy ingredients are displayed under visible light irradiation. Also, riboflavin can be found in many foods containing vegetables. The results of this study can be used to understand the stability and changes of isoflavone aglycones in soy and soy-based foods under visible light irradiation.     

Malondialdehyde Oxidation by Hydrogen Peroxide and by Light-Excited Riboflavin in Model Systems

Oxidation of malondialdchyde (MDA) by H₂O₂ was affected by concentrations of MDA or H₂O₂, pH and solvent. The reaction displayed an approximate 1:1 ratio of H₂O₂/MDA consumption and probably produced malonaldehyde as the oxidation product in moderate conditions. Oxidation of MDA by light-excited riboflavin produced superoxide anion, and the amount of superoxide anion generated was MDA concentration-dependent.     

Bisphenol A (BPA) and its source in foods in Japanese markets

The determination of bisphenol A (BPA) and/or bisphenol A diglycidyl ether (BADGE) in foods sold in Japanese markets and in water leached from six epoxy resin cans with similar diameters was carried out using high-performance liquid chromatography (HPLC) with electrochemical detection (LC/ECD), LC-mass spectrometric detection (LC/MS) and LC-tandem mass spectrometric detection (LC/MS/MS). BPA concentrations were 0-842 ng g^-1 for 48 canned foods, 0-14 ng g^-1 for 23 foods in plastic containers, and 0-1 ng g^-1 for 16 foods in paper containers. No BADGE was detected in three canned foods. There was no difference in leaching concentrations of BPA into glycine buffers at pHs 8 and 11, and water. The amounts of BPA leached into water from six epoxy resin cans held at 121°C for 20 min were almost the same as the cans' contents and were much higher than the amounts leached from cans held at or below 80°C for 60 min. The amount leached depended on the type of can, but not on the amount of BADGE leached from the cans. Considerably more BPA than BADGE leached to water from six cans. Two cans whose contents had high concentrations of BPA showed no BADGE leaching even at 121°C, suggesting the different kinds of epoxy resin can linings from others. The results imply that the main source of human exposure to BPA is food from cans with linings that contain high percentages of BPA as an additive or an unforeseen contaminant.     

Effects of riboflavin photosensitization on the changes of isoflavones in soymilk

Effects of riboflavin photosensitization on the distribution of isoflavones in commercially available soymilk were analyzed using high-performance liquid chromatography (HPLC). Total isoflavones (TI) in soymilk with riboflavin (1000 ppm, w/v) under light were significantly different from those stored in the dark for 24 h (P < 0.05), while TI in samples with 0 and 1000 ppm added riboflavin were not significant from each other in dark conditions (P > 0.05). To test the effects of the concentration of riboflavin on TI, soymilk was mixed with riboflavin to make 0, 100, 250, and 500 ppm (w/v) and stored under light at 25 degrees C for 24 h. TI in soymilk with 100 ppm riboflavin under light significantly decreased by 13.5% for 24 h (P < 0.05) compared to control samples and were not significantly different from those with 250 or 500 ppm samples (P > 0.05). Daidzin and genistin were predominant isoflavones in soymilk, and the rate of photo degradation of genistin was higher than that of daidzin for 24 h in soymilk under riboflavin photosensitization.     

Chemical Reactions and Stability of Riboflavin in Foods

ABSTRACT: Riboflavin is relatively stable during thermal and nonthermal food processing and storage but is very sensitive to light. It can accept or donate a pair of hydrogen atoms. It can act as a photosensitizer (through either Type I or Type II mechanism) or a prooxidant for food components under light. Photosensitization of riboflavin causes production of reactive oxygen species such as superoxide anion, singlet oxygen, hydroxy radical, and hydrogen peroxide. Radicals and reactive oxygen species accelerate the decomposition of proteins, lipids, carbohydrates, and vitamins, and could cause significant nutrient loss in foods. Carbohydrates are less sensitive to riboflavinphotosensitized oxidation than proteins, lipids, or vitamins. Riboflavin is an excellent photosensitizer for singlet oxygen formation and a superb reactant for singlet oxygen, with the reaction rate of 1.01 ± 10¹⁰/M/s.     

木质素基双酚A型环氧树脂的合成研究进展

当前,从制浆造纸工业黑液中回收的木质素主要用于生产混凝土减水剂、石油开采助剂、农药增效剂、分散剂等,但产品附加值不高。本文介绍了将工业木质素用于生产木质素基双酚A型环氧树脂的研究进展。主要生产方法包括木质素及其衍生物与环氧树脂直接共混固化、木质素及其衍生物环氧化合成环氧树脂和木质素及其衍生物官能化改性后合成环氧树脂。     

高效液相色谱-串联质谱法测定饮料、牛奶和奶粉中双酚A和15种邻苯二甲酸酯

目的建立了饮料、牛奶和奶粉中双酚A及15种邻苯二甲酸酯的高效液相色谱-串联质谱分析方法。方法样品经甲醇提取,C_(18)色谱柱分离后,采用串联四极杆质谱电喷雾电离源正负离子切换多反应离子监测模式检测。结果双酚A及15种邻苯二甲酸酯在各自的线性范围内线性关系良好,相关系数均不低于0.9900,定量下限为10μg/kg,低、中、高3个加标水平下平均回收率为61.1%~129.5%,相对标准偏差为1.13%~22.12%。结论该方法具有前处理简单、灵敏度高的优点,适用于饮料、牛奶及奶粉中双酚A及15种邻苯二甲酸酯残留的确证和定量检测。     

食品罐内涂料中双酚A环氧衍生物的迁移及其检测

食品罐内涂料中残留的双酚-A环氧衍生物是一种环境激素,通过罐头食品进入体内,造成内分泌失衡及遗传基因变异,欧盟食品科学委员会已严令限制其使用。本文介绍了该类物质在罐头食品中的产生、迁移及检测方法。     

Hot topic: Bisphenol A in cow milk and dietary exposure at the farm level

Chemical hazards may enter the milk chain during primary production. The study, for the first time, investigated the occurrence of bisphenol A (BPA) levels in cow milk samples collected on the farm following manual or mechanical milking and from the cooling tank. We applied a new monitoring model based on the identification of the hazards at each stage of the milk chain to identify potential pathways for contamination along the milk chain. We evaluated exposure to BPA through milk consumption based on detected contamination levels and the temporary tolerable daily intake established by the European Food Safety Authority (EFSA). Milk samples (n = 72) were analyzed using liquid chromatography with fluorescence detection. The mean BPA concentrations were 0.757 µg/L in manually milked samples, 0.580 µg/L in mechanically milked samples, and 0.797 µg/L in milk from the cooling tank. Bisphenol A occurred in the milk chain as a result of different stages of milking, and reached the highest levels at the end of the milk chain. Although the dietary intake of BPA was below the EFSA's temporary tolerable daily intake, exposure to BPA, even at low doses, through milk consumption represents a public health concern. Therefore, to ensure milk safety, new monitoring plans should be applied based on the identification of hazards at each stage of the milk chain.     

碳基复合材料修饰电化学传感器检测双酚A研究进展

双酚A作为一种应用最广泛的增塑剂,常用于食品的各类包装中。然而,食物和水源中双酚A的浸出以及在制造过程中双酚A的排放会危害人类健康。近年来,碳基复合材料因其独特的物理化学性质,在双酚A检测中展现出优异的性能,基于碳基复合材料修饰的电化学传感器快速检测双酚A已成为当前的研究热点。文章综述了双酚A以及碳基材料修饰电化学传感器在双酚A检测中的应用,并对双酚A电化学检测的发展方向进行了展望。     

双酚A单克隆抗体的制备及酶联免疫分析方法的建立

采用活泼酯法将双酚A的结构类似物双酚酸与载体蛋白偶联制备人工抗原,用制备的人工抗原免疫BALB/c小鼠,采用聚乙二醇法进行细胞融合制备双酚A单克隆抗体,成功获得一株分泌抗双酚A单克隆抗体的细胞株3H1,经鉴定抗体属于IgG1亚型,轻链为κ,并建立了间接竞争酶联免疫分析法。线性范围为1～50 ng/mL,最低检测限为0.43 ng/mL,半数抑制浓度为6.56 ng/mL。回收率为82.83%～101.94%,变异系数为2.94%～12.95%。该方法具有较高的灵敏度和特异性,具有良好的应用前景。     

双酚A荧光检测方法的建立及应用

双酚A是一种重要的工业原料,在生产制造业中应用广泛,因其具有典型的内分泌干扰作用,对人体健康相关的安全性问题引发社会密切关注,各种双酚A检测方法也纷纷建立.荧光检测由于灵敏度高、选择性好、操作简单、样品用量少、响应速度快等优势备受青睐,在众多检测方法中脱颖而出得以迅速发展.该文介绍双酚A荧光检测方法研究进展,并对其发展...     

杭州市场罐头类食品的双酚A污染调查及其膳食风险评估

目的:调查检测市场上罐头类食品的双酚A含量,明确其膳食暴露风险。方法:在杭州超市采集各类罐头食品样品93个,采用高效液相色谱法测定双酚A含量,采用点评估方法评估其膳食暴露风险。结果:罐头样品双酚A的检出率为29%,平均值为121.7μg/kg,最大值为2 840μg/kg,其中油性的鱼、肉和蔬菜类罐头双酚A含量较高;一般人群来源于罐头食品的双酚A膳食暴露量为0.04—0.20μg/(kg·bw)/d,占TDI的0.4%—2.0%。结论:油性的鱼、肉和蔬菜类罐头食品双酚A含量显著高于饮料和粥类罐头食品;在没有其他重大的暴露来源时,各类人群以罐头类食品为主的双酚A膳食暴露均在可接受的范围内。     

聚碳酸酯中双酚A向乙醇溶液中迁移规律和扩散系数研究

选取聚碳酸酯塑料为研究对象,分析双酚A单体在不同体积分数乙醇溶液中溶出情况,考察其在75、60、40、20 ℃下的迁移行为,在此基础上,计算相应的扩散系数,并对材料基体特征参数Ap值进行估算。结果表明：在相同的加热时间和温度下,乙醇体积分数越高双酚A的迁移率越大;相同体积分数乙醇溶液中,双酚A迁移率随着接触时间的延长、接触温度的升高而增加;双酚A向溶液中的扩散系数（DP）大小依次为95%乙醇＞65%乙醇＞15%乙醇＞蒸馏水,根据DP从而估算聚碳酸酯的基体特征参数Ap值范围为－1.02～7.54。