气相色谱--质谱法测定XO酱中BHA、BHT和TBHQ

采用气相色谱—质谱(全扫描方式)测定XO酱中丁基羟基茴香醚(BHA)、二丁基羟基甲苯(BHT)和叔丁基对苯二酚(TBHQ)。样品用甲醇振荡萃取，以DB—5MS为分析柱。3种组分的回收率在85％～99％之间，相对标准偏差小于8．4％；样品中BHA、BHT和TBHQ的检测限分别为0．05、0．05和0．10(mg／kg)。该法简单、快速、准确，可用于XO酱等基质复杂的富油食品中BHA、BHT和TBHQ的检测和确证。     

黄曲霉毒素B_1标准替代物的制备及其在花生样品检测中的应用

以抗黄曲霉毒素B1（AFB1）单克隆抗体的F（ab＇）2片段为抗原免疫兔子,得到AFB1抗独特型抗体。经过酶联免疫吸附法（ELISA）条件的优化,建立AFB1抗独特型抗体最佳竞争抑制曲线。该曲线与AFB1竞争抑制曲线相比较可知,AFB1抗独特型抗体与AFB1之间存在指数增长关系,且相关性系数R为0.999 8。以AFB1抗独特型抗体浓度与其相应的抑制率作标准曲线,ELISA法测定花生中AFB1添加回收率,范围在90.4%～100.2%之间。综上,AFB1抗独特型抗体可以作为AFB1无毒替代标准品。     

Determination of aflatoxins in eggs,milk, meat and meat products using HPLC fluorescent and UV detectors

Raw and pasteurised sheep’s, cow’s and goat’s milk, eggs, and beef samples from different local markets in Jordan were collected during a period of 5 months (January through May 2007) and examined for aflatoxins B1(AFB1), B2(AFB2), G1(AFG1), G2(AFG2), M1(AFM1) and M2(AFM2). The samples were analysed with high performance liquid chromatography (HPLC) using UV and Fluorescent detectors. The analysed samples of milk collected in January were found to contain 0.56 μg L⁻¹ AFM1 and 0.1 μg L⁻¹ AFM2 whilst, the concentration of AFM1 and AFM2 was < 0.05 μg L⁻¹ for milk samples collected between March and May. The AFB1, AFB2, AFG1 and AFG2 contents in the analysed food products ranged from 1.10 to 8.32 μg L⁻¹ and 0.15 to 6.36 μg L⁻¹ in imported and fresh meat samples collected during March, respectively. The mean recovery for the HPLC method was 92% to 109% and the quantification levels were 50 ng L⁻¹ for AFM1 and AFM2. The AFM1 was found in 10% of the tested samples with concentrations between 0.08 and 1.1 μg kg⁻¹ and AFM2 was only found in 1.82% of the tested samples with a level of 0.1 μg kg⁻¹. The AFM1 levels in the examined foods were higher than the maximum level of AFM1 in liquid milk set by the European Community and Codex Alimentarius of 50 ng L⁻¹.     

Natural co-occurrence of aflatoxin B1, fumonisin B1 and ochratoxin A in barley and corn foods from Korea

A survey for aflatoxin B₁ (AFB₁), fumonisin B₁ and ochratoxin A (OTA) was conducted on 127 samples that included 30 food-grade barley, 32 barley foods, 18 food-grade corn and 47 corn foods, randomly collected during 1998-99 in Seoul, Korea. The presence of mycotoxins was analysed by direct competitive enzyme-linked immunosorbent assay (ELISA), and most of the positive samples from ELISA were confirmed using high-performance liquid chromatography (HPLC). Recoveries of AFB₁ and OTA spiked at 10 ng g -1 and FB₁ spiked at 50 ng g^-1 were 106, 87 and 105% by ELISA, whereas those by HPLC were 80, 79 and 84%, respectively. Detection limits by ELISA for AFB₁, FB₁ and OTA were 1, 5 and 5 ng g^-1, and those by HPLC were 0.6, 35 and 1 ng g^-1. Naturally occurring AFB₁, FB₁ and OTA were found in 4/32 (12%), 2/32(6%) and 4/32 (12%) samples of barley foods with an average of 26, 16 and 9 ng g^-1, respectively. AFB₁ and FB₁ in corn foods were detected in 4/47 (8%) and 9/47 (19%) samples with the average being 20 and 74 ng g^-1, while no OTA was found in any corn foods samples. No AFB₁, FB₁ or OTA was detected in any of food-grade barley and corn samples. This is the first report on the natural co-occurrence of AFB₁ and FB₁ in barley and corn foods as well as on surveillance of OTA in Korea.     

Effect of gamma irradiation and heat treatment on the artificial contamination of maize grains by Aspergillus flavus Link NRRL 5906

Maize (Zea mays L.) is one of the main crops, which is easily susceptable to Aspergillus flavus infection resulting in huge losses worldwide. This study was carried out to investigate the effect of combining heat and irradiation treatments in controlling the fungal growth in maize grains. Surface disinfected maize grains were artificially contaminated with spores of Aspergillus flavus Link NRRL 5906, and then exposed to gamma radiation with doses of 3.0, 4.0 and 5.0 kGy. The samples were additionally heat treated at 60 °C for 30 min. The heat and irradiation treatments showed a synergistic effect on controlling Aspergillus flavus growth. The heat treatment reduced the required radiation dose of about 0.5–1.0 kGy when 4.0 kGy or 5.0 kGy irradiation was used. The combined heat and irradiation treatment of moisture reduced the average CFU by 8 log cycles when 4 kGy or 5 kGy irradiation was used and by 7 log cycles when 3 kGy irradiation was used. The heat treatment of moisture alone reduced the average CFU by only by 0.8 log cycles. Combining irradiation with heat treatment to reduce the required radiation dose is very useful especially when there is a concern over biological side effects of irradiation.     

Evaluation of antioxidant and inhibitory activities for different subclasses flavonoids on enzymes for rheumatoid arthritis

Antioxidant activities of flavonoids were decreased in the order of flavonols > flavanones > flavones. Inhibitory intensities for hyaluronidase and collagenase reaction differed clearly according to flavonoid subclasses. Kaempferol, quercetin, myricetin, and rutin in flavonols inhibited hyaluronidase reaction specifically, while apigenin, luteolin, baicalin, and baicalein in flavones showed specific inhibition to collagenase reaction. In addition, the flavonoids, except baicalin and catechin, inhibited potently LPS-induced nitrite production in a dose-dependent manner, which might be mainly due to the suppression of inducible nitric oxide (NO) synthase. Quercetin and luteolin showed the strongest inhibitory activities on 15-lipoxygenase (LOX), and quercetin showed relatively potent inhibition on cyclooxygenase-1 (COX-1) reaction. Otherwise, all tested flavonoids possessed the inhibitory activity to COX-2 reaction, and especially luteolin, kaempferol, hesperetin, and naringin showed relatively the potent inhibition on COX-2 reaction. This report elucidated the anti-inflammatory activities, such as the antioxidant property, inhibition of NO production, and inhibition of inflammatory enzymes (hyaluronidase, collagenase, LOX, and COXs) of several subclass flavonoids.     

抗AFB_1单域重链抗体文库淘选方法的研究

比较两种从噬菌体展示文库中淘选抗黄曲霉毒素B1单域重链抗体的方法,并为淘选针对小分子物质的单域重链抗体提供参考.采用固相淘选技术,以黄曲霉毒素B1人工抗原为靶分子,淘选天然单域重链抗体库,分别采用Gly-HCl法和AFB1竞争法洗脱结合噬菌体,对洗脱物进行滴度测定,以回收率和富集度为指标,对两种洗脱方法进行比较.采用phage-ELISA法鉴定噬菌体克隆,并对阳性克隆进行交叉反应分析以及序列测定.滴度测定结果显示,Gly-HCl法回收率比竞争法高5～10倍.分别随机挑取20个单克隆进行phage-ELISA鉴定,其中,Gly-HCl洗脱法未获得阳性克隆,AFB1竞争洗脱法得到8个阳性克隆.序列测定结果显示,这8个克隆均编码单域重链抗体.     

Investigation on sequential extraction of peanut allergens for subsequent analysis by ELISA and 2D gel electrophoresis

A two-step sequential extraction method of peanut proteins was proposed with the aim to investigate the protein composition and allergen content of peanut samples. The extraction procedure reported is fully compatible with subsequent analysis by enzyme-linked immunosorbent assays (ELISA) as well as 2D gel electrophoresis (2D PAGE). This sequential extraction method was used to study three different peanut varieties and three different types of food processing. Peanuts were analysed for total protein content and the extraction efficiency of raw and processed peanuts was determined. The total protein content of the three peanut varieties was found to be comparable, but their extraction efficiency varies. The peanut extracts were characterised by employing three different ELISA test kits specific to either the allergens Ara h 1 or Ara h 2, or to soluble peanut proteins. The content of both Ara h 1 and Ara h 2 differed in the raw peanut extracts of the three varieties. However, thermal processing resulted in much larger changes in detectability. Blanching significantly increases the detectability of Ara h 2, whereas Ara h 1 detection remains almost unchanged. After roasting a clear decrease of detectability was observed for both Ara h 1 and Ara h 2, although the effect is more severe for Ara h 1. 2D PAGE was employed to compare the protein profiles and abundances of peanut extracts. Statistically relevant differences were observed for the two different protein fractions obtained by using the described method, showing the relevance of this two-step sequential extraction method.     

Effect of heating rate at different moisture contents on starch retrogradation and starch–water interactions during gelatinization

The objective of this research was to investigate the effect of heating rate at different moisture contents on starch retrogradation and gelatinization process. Starch retrogradation was not influenced by either moisture content (water/starch ratio of 0.7 or 2.0) or heating rate (5°C/min, 20°C/min, or 40°C/min). In order to further understand the effects of heating rate on starch–water interactions, starch suspensions at a water/starch ratio ranging from 0.7 to 3.0 were heated at 5, 15, or 25°C/min by using a DSC to different final temperatures and rescanned. The deconvoluted G and M1 endotherms and the corresponding additional unfrozen water (AUW) were determined. The results showed that the G and M1 endotherms merged at higher heating rates and at higher moisture contents as expected. A significant interaction was observed between moisture content and heating rate. The results suggest that the gelatinization process is governed by moisture content at the lower heating rate (5°C/min) and by heating rate at the higher heating rates (15 or 25°C/min). Results from the AUW data suggest that the M1 component of gelatinization dominated at moisture content below water/starch ratio of 1.5 and at 5°C/min heating rate. However, at moisture contents above water/starch ratio 1.0, an interaction was observed between moisture content and heating rate. The data suggest that at higher moisture content (>1.5 water/starch ratio) and at higher heating rate (≥15°C/min), there is still a kinetic limitation to the complete melting of the M1 endotherm.     

Phenolic acids composition and antioxidant activity of canola extracts in cooked beef,chicken and pork

Crude polyphenol extracts (15 or 100 mg gallic acid equivalents (GAE)/kg meat) from canola meal reduced the formation of 2-thiobarbituric acid-reactive substances (TBARS) in pre-cooked beef (66–92%), pork (43–75%) and chicken (36–70%). The canola extract contained sinapic (99.7%), ferulic (0.28%) and p-hydroxybenzoic acids (0.07%).     

Effect of 1-methylcyclopropene on shelf life,visual quality,antioxidant enzymes and health-promoting compounds in broccoli florets

The effect of 1-methylcyclopropene (1-MCP) on quality, antioxidant enzymes and glucosinolate contents in broccoli (Brassica oleracea var. italica) florets was investigated in the present study. Broccoli florets were treated with air (control) and 2.5 μl/l 1-MCP for 6 h at 20 °C, and were then stored at 20 °C for 5 days. 1-MCP treatment markedly extended shelf life, reduced postharvest deterioration, retarded chlorophyll degradation and inhibited the increase of malondialdehyde amount and activities of polyphenol oxidase and lipoxygenase in florets. The activities of superoxide dismutase, peroxidase and catalase in florets treated with 1-MCP were higher than those in control florets. 1-MCP treatment reduced the rate of decrease of total carotenoids, ascorbic acid and glucosinolates in florets when compared to those in the control. These results indicated that 1-MCP treatment could be a good candidate for extending shelf life, maintaining visual quality and reducing loss of health-promoting compounds, particularly glucosinolates in broccoli.     

Purification and characterization of an antioxidant protein (∼16 kDa) from Terminalia chebula fruit

Terminalia chebula fruit is used as folk medicine in India and Southeast Asia. An antioxidant protein was isolated by bioassay guided fractionation of T.chebula fruit by homogenizing in the citrate phosphate buffer. The isolated protein (TCP-III) obtained from fruit was purified by gel chromatography and preparative HPLC, showed apparent molecular weight of 16 kDa by SDS-PAGE and MALDI-TOF/MS analyses. Amino acid sequence obtained by LC-MS^E analysis showed homology with the predicted protein fragments of Populus trichocarpa, putative uncharacterized protein fragments from Oryza sativa and with fragments of 17 kDa thylakoid lumenal protein from Spinacia oleracea. TCP-III exhibited significant radical scavenging in DPPH, NO, H₂O₂ and ABTS assays. In addition, TCP-III inhibited oxidation of linoleic acid in β-carotene bleaching assay, reduced ferric ions and chelated ferrous ions. The present finding demonstrates uniquely, for the first time, characterization of an antioxidant protein from T. chebula fruit.     

The influence of organ,season and drying method on chemical composition and antioxidant and antimicrobial activities of Juniperus phoenicea L. essential oils

BACKGROUND: Juniperus phoenicea is an important medicinal plant. In the present study, essential oils (18 samples) from leaves and berries of Juniperus phoenicea L. (Cupressaceae), obtained by various drying methods and in different collection months, were analysed by gas chromatography–mass spectrometry and also evaluated for in vitro antimicrobial and antioxidant activities. Correlations were studied between antimicrobial activity and the chemical composition of essential oils. RESULTS: Sixty‐seven compounds were identified in essential oils, representing 97.7–100%. Essential oils were dominated by monoterpenes and sesquiterpenes, which presented 35.0–93.3% and 6.7–62.0%, respectively, depending of organ, season and drying method. Antimicrobial tests showed that essential oils strongly inhibited the growth of Gram‐positive microorganisms and Mucor ramamnianus, but was inactive against Gram‐negative strains. Antioxidant activity was tested using the ABTS radical‐scavenging assay. Most samples showed good activity (the best IC₅₀ = 41.7 ± 1.5 mg L^?1). CONCLUSIONS: It could be concluded that drying of leaves of J. phoenicea in the sun and berries in oven‐drying was more suitable and was recommended for obtaining higher essential oil yield, but for a higher percentage of some special components such as α‐pinene and δ‐3‐carene shade‐drying was more suitable. Copyright © 2009 Society of Chemical Industry     

Effects of chitosan coating combined with essential oils on quality and antioxidant enzyme activities of grass carp (Ctenopharyngodon idellus) fillets stored at 4 °C

Effects of chitosan coating combined with essential oils from clove, cinnamon and lemon grass on quality and antioxidant enzyme activities of grass carp fillets stored at 4 ± 0.5 °C were evaluated. The quality parameters (including pH, total volatile basic nitrogen (TVB‐N), K value, thiobarbituric acid (TBA) value, shear force and total viable count (TVC)) and antioxidant enzyme activities were analysed periodically. The results indicated that composite chitosan coatings presented better preservation effects than chitosan coating alone. In addition, chitosan–clove essential oil coating had the best quality enhancement effects among treatments by inhibiting deterioration of physicochemical quality and microbial growth and maintaining antioxidant enzyme activities of fillets during refrigerated storage. The negative correlation was observed between the changes in TBA values and antioxidant enzyme activities in fillets. Based on these findings, chitosan–essential oil coatings effectively mitigated oxidative stress and extended shelf life of refrigerated grass carp fillets.     

The effects of ethanol treatment on the metabolism,shelf life and quality of stored tomatoes at different maturities and temperatures

Two maturity stages of commercially grown tomatoes (breaker and mature green) were exposed to ethanol vapour (2 ml ethanol kg⁻¹ fruit) for 6 h at 20 °C prior to storage at 5 °C and 20 °C. During storage the colour, firmness and composition changes were examined every 3 and 7 days. The results showed that ethanol vapour treatment could significantly slow down the colour changes and softening of both mature green and breaker tomatoes with greater effects when stored at 5 °C. There was no difference between the two maturity stages in retardation of softening during storage; in contrast the maturity stage had a highly significant effect in the colour development of stored tomatoes. When the fruit stored at 5 °C was then held at 20 °C for 7 days the ripening process was accelerated but the fruit did not reach the same level of colour development as the fruit stored at 20 °C continuously. The results suggest that ethanol vapour pretreatment could be used as a cheap and easy method to extend the storage life of tomatoes. © 1999 Society of Chemical Industry     

基于石墨烯/离子液体构建免疫传感器快速测定食品中黄曲霉毒素B1

采用壳聚糖、石墨烯和1-丁基-3-甲基咪唑基四氟硼酸盐复合膜修饰玻碳电极,包埋固定黄曲霉毒素B1（aflatoxin B1,AFB1）抗体,构建了一种免疫传感器,用于快速测定食品中的AFB1。在pH值为7.0含1 mmol/LK3[Fe(CN)6]和0.1 mmol/L KCl的磷酸盐缓冲溶液中,基于AFB1抗体与抗原之间的特异性免疫反应,以K3[Fe(CN)6]为探针,运用循环伏安法和差分脉冲伏安法研究免疫反应对传感器响应电流的影响。在优化实验条件下,免疫传感器峰电流的降低值随溶液中AFB1质量浓度对数的增大而增大,且二者在0.1～8.1 ng/mL范围内呈线性关系,其检出限为0.04 ng/mL（RSN=3）。该免疫传感器的稳定性和重复性较好,利用该法对花生和玉米油样品中AFB1进行检测,回收率为94.73%～104.41%,检测结果与高效液相色谱法基本一致,用于食品中AFB1的快速检测是可行的。     

Effects of binary solvent extraction system,extraction time and extraction temperature on phenolic antioxidants and antioxidant capacity from mengkudu (Morinda citrifolia)

An investigation into the effects of ethanol concentration (0–100%, v/v), extraction time (20–120 min) and extraction temperature (25–65 °C) on the extraction of phenolic antioxidants from mengkudu (Morinda citrifolia) was performed using a single-factor experiment. Total phenolic content (TPC) and total flavonoid content (TFC) assays were used for determination of phenolic compounds. Antioxidant capacity was evaluated by measuring the scavenging effect on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radicals. Experimental results showed that extraction conditions had significant effect on extraction of phenolic compounds and antioxidant capacities. The optimised conditions were 40% ethanol for 80 min at 65 °C, with values of 919.95 mg GAE/100 g DW for TPC, 472.73 mg CE/100 g DW for TFC, 791.71 μmol TEAC/100 g DW for ABTS and 1928.5 μmol TEAC/100 g DW for DPPH. TPC was significantly correlated with DPPH under the effects of ethanol concentration (r = 0.932) and extraction time (r = −0.938).     

Chitosan nanoencapsulation of Pogostemon cablin (Blanco) Benth. essential oil and its novel preservative effect for enhanced shelf life of stored Maize kernels during storage: Evaluation of its enhanced antifungal,antimycotoxin, antioxidant activities and possible mode of action

The present evaluation aimed to synthesis and characterise the Pogostemon cablin essential oil encapsulated chitosan nanoemulsion (PCEO-CN) and evaluated its antifungal antimycotoxin and antioxidant activities. A total of twenty-six different chemical compounds were identified from P. cablin essential oil (PCEO), among which patchoulol (34.93%), α-bulnesene (17.76%) and α-guaiene (15.44%) were recorded as major components. The average size of PCEO-CN was 18.20 nm. The PCEO-CN showed concentration-dependent broad-spectrum antifungal and antimycotoxin activities. The in vivo evaluation showed that PCEO-CN significantly protected maize seeds from mould-induced biodeterioration and aflatoxin B₁ biosynthesis for up to 30 days. The PCEO-CN significantly inhibits ergosterol biosynthesis and cellular integrities of A. flavus. Based on the present study, PCEO-CN could be used as a food preservative to control mould and mycotoxin contamination in stored maize.     

In vitro and in vivo studies on the antioxidant activities of the aqueous extracts of Douchi (a traditional Chinese salt-fermented soybean food)

The aqueous extracts of Douchi were obtained and evaluated for their antioxidant properties. The isoflavones and peptides contents of extracts were determined. Antioxidant activities in vitro of extracts were conducted by determining the α,α-diphenyl-β-pricrylhydrazyl (DPPH) and 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activities, and the chelating ability of ferrous ions, of which IC₅₀ values were found to be 0.658, 0.204 and 206 mg/mL, respectively. Antioxidant enzymatic activities of extracts in cholesterol-fed rats and an index of lipid peroxidation (thiobarbituric acid reactive substances (TBARS)) were determined, and hepatic tissue ultramicrostructure was also observed under transmission electron microscope (TEM). These results showed that, in Douchi extracts groups, superoxide dismutase (SOD) activities in liver and kidney, catalase (CAT) activity in liver, and glutathione peroxidase (GSH-Px) activity in kidney increased significantly compared with the negative control group (p < 0.05). TBARS in liver and kidney of extracts groups decreased significantly (p < 0.05). Less fatty degeneration in hepatocytes of extracts groups was found on TEM photos. The percentage of total isoflavones and peptides contents in aqueous extracts were 0.087% and 40.7%, respectively. These results showed that Douchi extracts had excellent antioxidant activities, might affect the activities of antioxidant enzymes and lipid peroxidation, and mitigate the lipidosis of hepatocytes.     

Effect of thermal processing on phenolics, antioxidant activity and health-relevant functionality of select grain sprouts and seedlings

The effect of thermal processing via autoclaving on modifications of total phenolics, antioxidant activity and functionality of wheat, buckwheat, corn and oats sprouts and seedlings were investigated. Functionality for type 2 diabetes related α-amylase, α-glucosidase inhibition and levo-dihydroxy phenylalanine (l-DOPA) content, hypertension related angiotensin converting enzyme 1 (ACE) inhibition and ulcer related Helicobacter pylori inhibition were evaluated using in vitro assays. Thermal processing in general resulted in tissue browning leading to higher total phenolic content and free radical scavenging-linked antioxidant activity. It increased α-amylase inhibitory activity in buckwheat and oats but decreased in wheat and corn sprouts and seedlings. It increased α-glucosidase inhibitory activity in wheat, buckwheat and oats but decreased in corn sprouts. It reduced the cognitive function/diabetes related l-DOPA content in all grains sprouts and seedlings tested. It increased ACE inhibitory activity in buckwheat and oats, but decreased in wheat and corn sprouts. It also improved the ulcer related H. pylori inhibitory activity in all grain sprouts and seedlings studied. These changes in functionality are suggested to be due to modifications in the total phenolic content and profile by phenolic oxidation or polymerization caused by thermal processing. Therefore, diet designs for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles.

Industrial relevance

Thermal processing altered the total phenolic content and antioxidant activity in winter wheat, buckwheat, corn and oats sprouts and seedlings. It modified the α-amylase inhibitory activity, α-glucosidase inhibitory activity, l-DOPA content, ACE inhibitory activity and H. pylori inhibitory activity of samples. Therefore, the food processing industry and diet design for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles for more effective health benefits.