Moisture sorption isotherms and thermodynamic properties of walnut kernels

The moisture sorption isotherm data of walnut kernels stored in a chamber, the relative humidity (r.h.) of which is regulated by atomizing humidifier, were determined at three different temperatures (25, 35 and 45 °C) and r.h. ranging from 10% to 90%. Eight models, namely the GAB, BET, Henderson, Iglesias and Chirife, Oswin, Peleg, Smith and Caurie equations, were fitted to the sorption data. Several statistical tests were adopted as the criteria to evaluate the fitting performance of the models. Of the models tested, the Peleg model gave the best fit to experimental data. The surface area of a monolayer was calculated. The BET equation was applied to the monolayer moisture content and the corresponding a_w values at which a monolayer forms are presented. The experimental data were also used to determine the thermodynamic functions such as isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy. The sorption isosteric heats for walnut kernels were determined by the application of the Clausius-Clapeyron equation to sorption isotherms obtained from the best-fitting equation. Isosteric heats decreased with increase in moisture content and approached the latent heat of pure water. Adsorption entropy increased with increasing moisture content, and then it decreased sharply with increase in moisture content. The spreading pressures (adsorption and desorption) increased with increasing water activity. Net integral enthalpy of adsorption increased slightly with moisture content to a maximum value. Thereafter, it remained constant. Net integral entropy of adsorption was negative in value and it decreased with increase in moisture content to a minimum value, and then increased slightly with increase in moisture content.     

核桃仁发育过程中不同形态酚及其抗氧化活性的动态变化

阐明发育期核桃仁中3种不同形态酚（游离、酯化和结合）及其单体酚组成的变化,探究酚类成分与抗氧化能力的关系,为深入了解核桃功能性成分形成规律和深化功能性产品开发提供参考。以核桃品种‘寒丰’为对象,运用UPLC-MS/MS测定3种形态酚组成,分光光度计法测定核桃的羟自由基清除能力,皮尔逊相关分析用于研究酚类物质与羟自由基清除能力的相关性关系。在核桃仁发育过程中,酚形态中以游离态为主且占比大于58%;3种形态总酚含量最高值均出现在采前63 d,分别为10.47 mg/g（游离态）、2.76 mg/g（酯化态）、1.28 mg/g（结合态）;鞣花酸、咖啡酸、绿原酸等单体酚的3种形态含量随着核桃仁发育显著降低58.03%-88.83%;单体酚含量与抗氧化活性呈现显著相关性,相关系数为0.63-0.97。核桃仁3种形态总酚含量和抗氧化活性最大值均出现在未成熟早期,游离态是核桃仁中提供抗氧化活性的酚类物质主要形态,并且核桃仁发育过程中单体酚的抗氧化能力与成熟度、酚形态有关。这些发现将对核桃的适时采摘和营养管理以及核桃仁深度开发利用、产业提质增效等提供重要的基础数据和理论参考。     

Phenolics from walnut (Juglans regia L.) kernels: Antioxidant activity and interactions with proteins

Walnut (Juglans regia L.) kernels have important amounts of phenolic compounds. The objectives of the work were twofold: (a) to extract the phenolic fraction from hulls and walnut flour, and to examine its antioxidant capacity and (b) to evaluate the effect of hull removal on solubility of protein fractions from walnut flour. In accordance with their higher total phenolic content, hull extracts had stronger antioxidant activity than had flour extracts. The presence of phenolic compounds decreased protein solubility in walnut flour obtained from whole kernels. Dehulling of kernels significantly improved protein recovery but this result was strongly affected by the solvent system employed. Proteins from whole kernels, especially those extracted with water and NaCl solution, had a reduced solubility, indicating that phenolics bind to proteins when they are dispersed in aqueous media at neutral pH. The results are discussed in the light of the different complex-forming mechanisms that bind phenolics to proteins.     

Pressing and supercritical carbon dioxide extraction of walnut oil

The objective of this study was to evaluate the oil extraction process from walnut seeds by pressing followed by extraction with supercritical CO₂. In pressing experiments, a factorial arrangement was conducted in order to study the combined effects of seed moisture content (2.5%, 4.5% and 7.5%) and pressing temperature (25, 50 and 70 °C) on oil recovery and quality parameters. For all conditions tested, the oil quality compared well with that of cold-pressed walnut oil. Oil recovery increased significantly as moisture content raised. Highest oil recovery (89.3%) was obtained at 7.5% moisture content and 50 °C temperature. The cake resulting from pressing at these conditions was extracted with CO₂ in a high pressure pilot plant with single stage separation and solvent recycle. The effects of two different pressures (200 and 400 bar) and temperatures (50 and 70 °C) with regard to oil yield and quality, and time required for extraction were analyzed. At each condition, the extraction rate changed with the mass of solvent and extraction time. At first, the mass of oil extracted was determined by the oil solubility in CO₂ and a linear relationship was observed, where the slope results in the solubility of oil in CO₂ at the experiment conditions. After that, the extraction rate was governed by solubility and diffusion, and continuously decreased with time. The colour changed along the extraction from a whitish clear product to a yellow one. Tocopherol and carotenoid contents were significantly higher than those obtained by pressing. Extraction conditions did not affect significantly the fatty acid composition.     

Survey of aflatoxin M1 in milk and dairy products consumed in Burdur,Turkey

The aim of this study was to investigate the occurrence of aflatoxin M₁ (AFM₁) in dairy product samples in Burdur city. A total of 315 samples of dairy products were collected during 2008. Of the 315 samples analysed, AFM₁ in 246 samples (78.1%) was found to range from 5.5 to 800 ng/kg. In addition, AFM₁ levels of 16 raw milk, two pasteurised milk, only one milk powder and three white cheese samples were above the Turkish Food Codex. It is concluded that the occurrence of AFM₁ in dairy products may be considered as a possible hazard for public health.     

Mycoflora and Aflatoxin Content of Hazelnuts,Walnuts, Peanuts,Almonds and Roasted Chickpeas (LEBLEBI) Sold in Turkey

In this study, 28 hazelnuts, 24 walnuts, 18 peanuts, 13 almonds, and 11 roasted chickpeas (leblebi) were analyzed for aflatoxin contamination using thin layer chromatography (TLC). Aflatoxin was found in 26 of 94 samples (27.66%) at concentrations ranging from 1 to 113 ppb. Detectable levels of aflatoxin were 33.4 ppb in hazelnuts, 22.1 ppb in walnuts, 43.0 ppb in peanuts, 7.4 ppb in almonds, and 1.7 ppb in roasted chickpeas. The highest level of aflatoxin was 113 ppb in a single hazelnut sample. Aspergillus and Penicillium species were frequently determined in all the samples.     

Near-infrared reflectance spectroscopy for the prediction of chemical composition in walnut kernel

In the present work, 116 samples were collected and near-infrared reflectance spectroscopy prediction model for determination of moisture, protein, and fat contents of walnut meal were obtained and evaluated. All the samples were analyzed based on the chemical methods. Meanwhile, they were scanned to obtain their near-infrared reflectance spectrum in the wavelength range of 570–1840 nm. Several preprocess treatments including scattering pretreatments, mathematical pretreatments, and aggression methods were optimized to increase the accuracy of the calibration models according to the coefficient of determination for calibration (R_c²) and the cross-validation (one minus the variance ratio, 1-VR), and the standard error of calibration and cross-validation. The results showed modified partial least square loading was the better aggression method to predict the moisture, proteins, and fats in walnut kernel. The calibration equations obtained indicated that near-infrared reflectance spectroscopy had excellent predictive capacity for the three components with R_c² = 0.965, standard error of calibration = 0.052 for moisture, and R_c² = 0.967, standard error of calibration = 0.191 for proteins, and R_c² = 0.979, standard error of calibration = 0.171 for fats, respectively. The external validation further confirmed the robustness and reliability of the near-infrared reflectance spectroscopy prediction models with the correlation coefficient of actual and predicted values (R²) = 0.952, ratio of performance deviation = 4.14, the standard error of prediction =0.058 for moisture, and R² = 0.977, ratio of performance deviation = 5.55, standard error of prediction = 0.182 for proteins, and R² = 0.990, ratio of performance deviation = 8.64, standard error of prediction = 0.191 for fats, respectively. Near-infrared reflectance spectroscopy is a reliable technology to predict these constituents in walnuts.     

The effects of citrus oils and some spices on growth and aflatoxin production by Aspergillus parasiticus NRRL 2999

The inhibitory effect of various concentrations of mint, sage, bay leaves, thyme, aniseed, red pepper and citrus peel oils on the growth of an aflatoxin-producing strain of Aspergillus parasiticus and its production of aflatoxin was studied. Amongst the herbs used, thyme was found a highly effective antifungal agent. Growth and aflatoxin formation was depressed by orange and lemon oils at a concentration of 1.6% through 10 days incubation.     

Evaluation and validation of two fluorometric HPLC methods for the determination of aflatoxin B1 in olive oil

Two methods for the determination of aflatoxin B₁(AFB₁) in olive oil were tested and compared. In method A the oil sample was mixed with methanol + water (60 + 40), extracted with hexane and then with chloroform. Chloroform was evaporated and the residue was dissolved with dichloromethane which was then transferred for clean-up onto a silica 'Sep-Pak' cartridge. The cartridge was pre-washed with hexane, ethyl ether and dichloromethane. AFB₁ was eluted with chloroform + acetone (9 + 1) and evaporated to dryness. In method B, the oil sample was mixed with methanol + water (80 + 20), shaken and centrifuged. The supernatant was diluted 1:10 with water and 10ml of the diluted mixture transferred to an 'Aflaprep' immunoaffinity column for the clean-up step. AFB₁ was eluted with acetonitrile and evaporated to dryness. AFB₁ from both methods was derivatized to its hemiacetal (AFB_2a ) and then quantitated by HPLC using a C₁₈ (60 A 4.6 x 250 mm) column with fluorescence detection. Both methods are simple, reliable and efficient, but method A showed a lower detection limit (2.8 ng/kg) than method B (56 ng/kg). With a 95% confidence level there was no significant difference in recovery between the two methods, which was 87.2% for method A and 84.8% for method B. In addition, application of a two-tailed F-test to the variances within spiked samples at concentrations 1, 2, 5 and 10 mu g/kg separately showed that there was no significant difference in the precisions of the two methods. Fifty samples of olive oil of Greek origin produced between 1995 and 1998 were examined with both methods for the presence of AFB₁. When analysing the samples with method B, the presence of AFB₁ was not detected. The use of method A revealed the presence of AFB₁ in 72% of the samples. The range of contamination was generally found to be very low (2.8-15.7 ng/kg), however one sample was contaminated with 46.3 ng/kg.     

Comparison of nixtamalization and extrusion processes for a reduction in aflatoxin content

Traditional nixtamalization and an extrusion method for making the dough ( masa ) for corn tortillas that requires using lime and hydrogen peroxide were evaluated for the detoxification of aflatoxins. The traditional nixtamalization process reduced levels of aflatoxin B 1 (AFB 1 ) by 94%, aflatoxin M 1 (AFM 1 ) by 90% and aflatoxin B 1 -8,9-dihydrodiol (AFB 1 -dihydrodiol) by 93%. The extrusion process reduced levels of AFB 1 by 46%, AFM 1 by 20% and AFB 1 -dihydrodiol by 53%. Extrusion treatments with 0, 0.3 and 0.5% lime reduced AFB 1 levels by 46, 74 and 85%, respectively. The inactivation of AFB 1 , AFM 1 and AFB 1 -dihydrodiol in the extrusion process using lime together with hydrogen peroxide showed higher elimination of AFB 1 than treatments with lime or hydrogen peroxide alone. The extrusion process with 0.3% lime and 1.5% hydrogen peroxide was the most effective process to detoxify aflatoxins in corn tortillas, but a high level of those reagents negatively affected the taste and aroma of the corn tortilla as compared with tortillas elaborated by the traditional nixtamalization process.     

Reduction in aflatoxin M1 concentration during production and storage of selected fermented milks

This study focused on monitoring changes in aflatoxin M1 (AFM1) concentrations during production and storage of different fermented milks using selected probiotic and nonprobiotic combined cultures. Milk samples intended for fermentation were intentionally contaminated by adding a standard of AFM1. All of the tested cultures caused remarkable reductions in AFM1 concentrations during the fermentation process. Probiotic cultures were more effective than nonprobiotic cultures, with Lactobacillus caseiLC‐01 strain being the most efficient, achieving a reduction level of approximately 58%. Among the nonprobiotic cultures, yoghurt culture YC‐380 was the most efficient, with a reduction level of approximately 41%.     

Antifungal properties and inhibitory effects upon aflatoxin production by Zingiber officinale essential oil in Aspergillus flavus

In this study, the efficacy of ginger (Zingiber officinale Roscoe) essential oil (GEO) in reducing A. flavus growth and aflatoxin production was investigated. Gas chromatography coupled to mass spectrometry and nuclear magnetic resonance spectroscopy showed that the major components of GEO were α‐zingiberene (23.85%) and geranial (14.16%). Mycelial growth of Aspergillus flavus was reduced significantly at a GEO concentration of 150 μg mL^?1, and complete inhibition of conidial germination was observed at a concentration of 10 μg mL^?1. Statistically significant inhibition of ergosterol biosynthesis was detected at a GEO concentration of 10 μg mL^?1. GEO was capable of fully inhibiting aflatoxin production by A. flavus at a concentration of 15 μg mL^?1. The results suggest that low concentrations of GEO are capable of inhibiting aflatoxin production; such ability could be valuable in the upcoming future for agricultural companies to better control aflatoxigenic fungi in agricultural products.     

东北地区大豆主栽品种油份蛋白含量的关联分析

为探寻与大豆油份含量、蛋白含量相关的关键位点,本研究选取中国东北地区92份大豆主栽品种及常用种质资源品种群体基于蛋白含量和油份含量的Meta分析,进行基于数学模型的类群划分评价,估测样本群体的结构,应用简单线性模型分析与大豆油份含量、蛋白含量相关的的位点。结果表明,通过多次迭代测试,当K=5时,即该资源群体可以分为5个亚群时,为最稳定的分类结果,并在显著水平下（p〈0.05）贡献率大于1%的标记中,得到与大豆油份含量相关标记有Sat_412,Sat_195,Satt317,Sat_187,Sat_195,Satt255,Satt713,Satt468,Satt267,Satt686,Sat_294和AZ302047,对油分含量的总贡献率为39.54%。蛋白质含量相关标记有Satt683,Sat_311,Satt578,Satt181,Satt317,Satt700,Satt713,Satt255,Sat_242和Satt720对蛋白质含量总贡献率为48.39%。这些重要的标记位点为大豆油份含量和蛋白含量的分子辅助育种提供重要基础。     

Temperature,water activity and gas composition effects on the growth and aflatoxin production by Aspergillus flavus on paddy

The main aim of this study was to evaluate the combined effects of temperature with water activity (a_w) and CO₂ with a_w on the growth and aflatoxin production by Aspergillus flavus Link on paddy. The effects of temperature (20–30 °C) and a_w (0.92–0.98) on the relationship between colony diameter and aflatoxin production, and the influence of a_w (0.92–0.98) and CO₂ (20–80%) on the growth and toxin production were studied using full factorial design. Colony diameters were regularly measured and aflatoxins were periodically analyzed using HPLC with fluorescence detector. The growth and aflatoxin formation increased with a_w at the temperatures studied, and toxin production was positively correlated with the incubation time and colony diameter. Except at 0.92 a_w, as much as 80% CO₂ failed to inhibit the growth of fungi completely. However, at all a_w levels studied the growth parameters as estimated by Baranyi function and aflatoxin were affected by the increment in CO₂ where growth rates and aflatoxin were negatively correlated with CO₂ while the lag phase durations were positively correlated with CO₂. Under 0.98 a_w, the atmosphere enriched with 20% and 80% CO₂ lead to at least 59% and 88% reduction in growth and 47% and 97% in the toxin production, respectively. At 0.95 a_w, the lag phases of both isolates in average increased by a factor of 1.7–12 when the CO₂ levels in the headspace were between 20 and 80% compared to the control. The growth rate and lag phase durations under the modified atmospheres were successfully described using a polynomial equation (R² > 0.97). The results of the study could form a basis of indicative guidelines on the possible control of A. flavus and aflatoxin in paddy during temporary storage prior to drying.     

Isolation of methyl syringate as a specific aflatoxin production inhibitor from the essential oil of Betula alba and aflatoxin production inhibitory activities of its related compounds

Methyl syringate was isolated from the essential oil of Betula alba as an aflatoxin production inhibitor. It inhibited aflatoxin production of Aspergillus parasiticus and Aspergillus flavus with IC₅₀ values of 0.9 and 0.8 mM, respectively, without significantly inhibiting fungal growth. Methyl syringate reduced mRNA levels of genes (aflR, pksA, and omtA) encoding proteins required for aflatoxin biosynthesis. Methyl gallate, methyl 3,4,5-trimethoxybenzoate, and methyl 3-O-methylgallate inhibited both aflatoxin production and fungal growth of A. parasiticus and A. flavus. However, their acids and syringic acid did not inhibit aflatoxin production and growth of A. parasiticus significantly, although gallic acid inhibited aflatoxin production of A. flavus with selectivity. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of methyl syringate was much weaker than that of gallic acid. These results showed that methyl syringate has a unique inhibitory activity toward aflatoxin production with a different mode of action from that of gallic acid.     

国外燃料酒精和淀粉加工产品的生产和发展

为了减少对石油的依赖 ,把 12 %的无水酒精 (燃料酒精 )加入汽油 ,2 0 %于柴油中 ,此含氧汽油不再加入四甲基叔丁基醚 ,成为汽车排放废气污染环境少的绿色燃料。　　列举了北美 (美国和加拿大 )燃料酒精厂的规模 ,所用原料、厂址、原料和产品价格的变化。在世界范围内 ,主要产品 (如淀粉、果葡糖浆、酒精等化工产品 )的输出交易量     

2011-2012年食用植物油中黄曲霉毒素B1的调查

为调查我国市场食用植物油油中黄曲礞毒素B1是螽符合国家标准规定,本论义膈两年的时间,对988个传统烹调油样品、342个新兴功放类油样品中的黄曲霉毒素B1进行了检测。结果显示：2011年传统烹调油合格率为99．22％,新必功效类油样,铺及凋味汕合格宰为95．03％;2012年传统烹调油合格率为99．37％,新必功效类油样品及调味油合格半为96．90％。由此可见,食用油产品的合格牢征逐年提高。     

Inhibition of polymerase chain reaction for the detection of Escherichia coli O157:H7 and Salmonella enterica on walnut kernels

The aim of this study was to determine whether Escherichia coli O157:H7 can be reliably detected and isolated from walnut kernels using standard methods of analysis. The limit of detection approached 1 cell per analytical unit (25 g) for E. coli O157:H7 on walnut kernels enriched in modified tryptic soy broth with 20 μg/ml novobiocin and plating onto selective agar media. The presence of PCR inhibitors in walnut kernels was indicated by the failure to detect E. coli O157:H7 from culture positive enrichment broths analysed by PCR, with two separate polymerase and reagent compositions (Dupont BAX E. coli O157:H7 MP system, Promega GoTaq Green for stx) and three methods of template preparation (DuPont BAX, Qiagen DNeasy, Bio-Rad InstaGene). PCR inhibition was overcome by 1:100 dilution in TE buffer of the DNeasy or InstaGene template. PCR inhibition was not relieved by dilution of the BAX template. Similar results were observed for walnut kernels inoculated with Salmonella enterica and analysed for invA, indicating that PCR inhibition is not specific to the organism or primer/template. These results indicate that analysis of walnut kernels for pathogens should be with culture based methods or use protocols for DNA template preparation modified to remove or dilute inhibitors and the need for internal amplification controls in PCR methods.