The derivation of the GAB adsorption equation from the BDDT adsorption theory

The BET‐like adsorption equation, popularly known as the GAB equation, was derived from the BDDT adsorption equation without changes to the bulk liquid properties of multilayer molecules. Without these changes the third parameter K in the GAB equation cannot be said to measure changes in the bulk liquid properties of the multilayer molecules. Instead K measures the range of application of the GAB equation and differentiates multilayer adsorption, when K > 0.5, from singular layer adsorption, when K ≤ 0.5. The GAB equation, derived from and based on the BDDT theory is argued, in this paper, to provide a greater insight into the mechanism of water adsorption than the same equation derived from and based on the BET theory.     

菊花化学成分、药理作用的研究进展及质量标志物预测分析

为探讨干制菊花吸湿特性与其结构、水分活度（A_w）、贮藏温度的关系,本文以2种菊花粉末（小黄菊和贡菊王）为对象,采用扫描电子显微镜（SEM）、傅里叶变换红外光谱（FT-IR）、X射线电子能谱（XPS）对其结构特征进行分析,结果显示菊花粉末表面粗糙,含有大量凹陷和孔洞;与小黄菊相比,贡菊王粉末粒径较小且表面含有更多的亲水基团,如-OH,O-C-O等。采用静态称量法在20、30和40 ℃和A_w=0.112～0.976下研究了2种菊花粉末的水分吸附行为,并通过模型拟合和热力学分析阐明了物料的水分吸附机制。菊花粉末的平衡干基含水率（X_e）随水分活度（A_w）增加而升高,但在同一A_w下,温度越高X_e值越低。Peleg模型是描述水分吸附等温线的最佳模型。热力学分析表明,净等量吸附热（q_st）随平衡干基含水率升高而降低,其中小黄菊和贡菊王粉末的q_st值分别于X_e>0.14 g/g和X_e>0.24 g/g时趋于恒定。小黄菊在20、30和40 ℃下的单分子层干基含水率（X_m）分别为0.0690、0.0525、0.0505 g/g（干基）,而贡菊王为0.0645、0.0591和0.0584 g/g（干基）。有效孔径（r_p）随温度和水分含量增加而增大,其中当X_e>0.09 g/g（干基）时小黄菊粉末呈现介孔特性,而贡菊王粉末则当X_e>0.11 g/g（干基）时内部孔隙才由微孔转变成介孔。研究结果可为菊花的干燥工艺优化与贮藏条件选择提供参考。

     

Physical Stability of Octenyl Succinate–Modified Polysaccharides and Whey Proteins for Potential Use as Bioactive Carriers in Food Systems

The high cost and potential toxicity of biodegradable polymers like poly(lactic‐co‐glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate–modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α‐lactalbumin (α‐L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim–Andersen–de Boer model indicated that native waxy corn had significantly (P < 0.05) higher water monolayer capacity followed by 3%‐OSA‐modified DWxCn, WPI, 3%‐OSA‐modified DWxRc, α‐L, and native phytoglycogen. WPC had significantly lower water monolayer capacity. All Tg values matched with the solid‐like appearance of the biopolymers. Native polysaccharides and whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%‐OSA modification had a “melted” appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA‐modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications.     

水分子相态转变对花桥板栗淀粉凝胶结构的影响

水分子相态转变会导致淀粉基制品的品质发生劣变,这主要是由水分子相态转变引起淀粉凝胶特性改变所致。而淀粉基食品在冻融处理过程中经常会涉及到水分子的相态转变。本文以花桥板栗淀粉为研究对象,采用SEM、XRD、FT-IR研究了水分子相态转变处理次数对花桥板栗淀粉凝胶的微观结构、晶体特性等方面的影响。结果显示,水分子相态转变使得花桥板栗淀粉凝胶结构发生失水收缩现象。随着相态转变次数增加,凝胶结构中的孔径逐渐变大并发生淀粉分子重排。水分子相态转变对其形成新的晶体结构贡献不大,后者晶体结构大多为CB型。随着相态转变处理次数的增加,结晶度从2.97%增加到了12.78%,相态转变7次后,结晶度下降为5.71%。随着相态转变的增加,羟基(-OH)发生红移;而醇羟基、C-O-C中的C-O发生蓝移且分别在转变3次、4次后峰位不发生偏移,但峰高增加。     

盐湖卤水提锂过程中析盐规律的研究

以Na^ ，K^ ，Mg^2 /／Cl^-，SO4^2-——H2O五元交互体系相图分析和试验，对青海某盐湖卤水提锂过程的自然蒸发阶段的蒸发析盐规律进行研究。蒸发过程中，使镁离子以镁复盐及镁的水合盐的形式，分阶段结晶析出加以分离，获得镁锂比低，锂离子浓度高的富锂卤水。同时副产氯化钠，钾盐，镁盐等有价值的副产品．使提锂成本降低，资源利用率提高。     

气相色谱法测定保健食品中二十碳五烯酸的不确定度评定

目的评定气相色谱法测定保健食品中二十碳五烯酸的不确定度。方法样品用正己烷溶解,经皂化、甲酯化后用气相色谱法检测,外标法定量,对保健食品中的二十碳五烯酸进行测定。建立数学模型对测量不确定度的来源进行分析和评定,合成不确定度。结果二十碳五烯酸含量测定的合成不确定度为4.2%,扩展不确定度为19 mg/g,测量结果为(2.2±0.2)×10~2 mg/g,k=2,置信区间为95%。通过对各不确定度分量进行分析,不确定度主要由标准系列溶液配制和样品制备过程引入。结论对气相色谱法测定保健食品中二十碳五烯酸的过程进行不确定度评定与分析,有利于检测结果准确性的提高和实验室的质量控制。     

The glassy state phenomenon in applications for the food industry: Application of the food polymer science approach to structure–function relationships of sucrose in cookie and cracker systems

This review of the glassy state phenomenon in applications for the food industry comprises two main parts. The first is a broad but brief overview of the so-called ‘food polymer science’ approach and its importance to food R&D studies of glassy solid and rubbery liquid states and glass transitions in food products and processes. The following elements of this approach are discussed: (i) the glass transition temperature (T_g) and methods for its measurement in foods; (ii) plasticization by water and its effect on T_g; (iii) the concepts of ‘water dynamics’ and ‘glass dynamics’ in non-equilibrium food systems; (iv) Williams–Landel–Ferry kinetics in the rubbery state above T_g, (v) state diagrams; and (vi) the effect of molecular weight on T_g. A comprehensive and up-to-date listing of more than 400 literature references on the glassy state phenomenon and glass transitions in food materials and systems is featured in that part of the paper, and these references are also compiled and tabulated according to specific subject headings. The second part of this review highlights the application of the food polymer science approach in recently reported studies on the structure–function relationships of sucrose in cookie and cracker systems. This part describes (i) the sucrose–water state diagram as a tool in understanding cookie and cracker baking; (ii) shortcomings of the traditional AACC sugar-snap cookie method as a test-baking system, in contrast to a new test system based on a model commercial-type wire-cut cookie formula; and (iii) a revealing illustration of sucrose functionality in cookie baking. The review concludes with a word about future prospects.     

A critical analysis of mathematical procedures for the evaluation and design of in‐container thermal processes for foods

Kinetic data on thermal destruction of spoilage and quality factors coupled with the temperature history of a product during a heat sterilization cycle are the basic information needed for the evaluation and the design of thermal processes through a physical‐mathematical approach. A critical review on the available physical‐mathematical procedures used for thermal process calculations of in‐container processed foods is presented. The origin and the limitations of each method are discussed. The equations associated with each method, for internal product temperature predictions, are explicitly given. The relative performance of selected methods under identical processing conditions is illustrated. Several problems associated with thermal process calculations are discussed.     

Solid phase extraction as sample treatment for the determination of Ochratoxin A in foods: A review

Ochratoxin A (OTA) is a mycotoxin produced by two main types of fungi, Aspergillus and Penicillium species. OTA is a natural contaminant found in a large number of different matrices and is considered as a possible carcinogen for humans. Hence, low maximum permitted levels in foods have been established by competent authorities around the world, making essential the use of very sensitive analytical methods for OTA detection. Sample treatment is a crucial step of analytical methodology to get clean and concentrated extracts, and therefore low limits of quantification. Solid phase extraction (SPE) is a useful technique for rapid and selective sample preparation. This sample treatment enables the concentration and purification of analytes from the sample solution or extract by sorption on a solid sorbent. This review is focused on sample treatment procedures based on SPE prior to the determination of OTA in food matrices, published from 2010.     

Optimization of a One‐Step Method for the Multiresidue Determination of Organophosphorous Pesticides in Camellia Oil

Due to the widespread use and potential toxicity of organophosphorous pesticides (OPs), multiresidue monitoring of OPs in camellia oil has become increasingly important. A simple, rapid, and effective matrix solid‐phase dispersion extraction for the determination of 15 organophosphorous pesticides in camellia oil is described. Related important factors influencing the extraction efficiency, such as type of sorbent material, eluting solvent, and ratio of sample/sorbent were studied and optimized. The best results were obtained using 0.5 g of camellia oil, 1.5 g of white carbon black as dispersant sorbent, and 5 mL of acetonitrile: ethyl acetate (2:1, V/V) as eluting solvent. Method validation was performed in order to study sensitivity, linearity, precision, and accuracy. Average recoveries ranged between 76.7% and 102.9% with relative standard deviation values from 2.9% to 13.7% at 2 concentration levels (10 and 100 μg/kg). The method limit of detection at or below the regulatory maximum residue limits for the pesticides was achieved. Practical Application: A simple, rapid, and effective method for multiresidue determination of organophosphorous pesticides in camellia oil was developed. The sample preparation could finish in 5 min.     

An improved LC-MS/MS method for the quantitation of acrylamide in processed foods

An improved liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of acrylamide in processed foods. The homogenized samples, spiked with ¹³C₃-acrylamide as an internal standard, were extracted with water and centrifuged. D₅-3-chloropropanediol as a recovery standard was added to 1-ml aliquots, and the sample was purified with a C₁₈-cartridge column. The extract was directly analyzed using LC-MS/MS without derivatization. The ion transitions of 72–55 m/z (acrylamide), 75–58 m/z (¹³C₃-acrylamide), and 116–98 m/z (d₅-3-chloropropanediol) were found to be the most reliable for the identification and quantification of acrylamide in multiple reaction monitoring. The limit of quantification for acrylamide, defined as a signal-to-noise ratio of 10:1, was 2 μg/kg. The use of d₅-3-chloropropanediol minimized the effects of variation in the sample matrixes and increased the quality of analysis. This method could be applied to the quantification of acrylamide in processed foods.     

Optimization of solid‐phase microextraction methods for GC‐MS determination of terpenes in wine

Solid‐phase microextraction using a 100 µm poly(dimethylsiloxane) fiber, followed by gas chromatography–mass spectrometry determination, has been optimized for the analysis of some terpenes in wine samples. The best results were obtained by direct immersion of the fiber using a sampling period of 15 min with constant magnetic stirring (1100 rpm) and an extraction temperature of 20 °C. The sample volume was 7 ml with 25% NaCl, in a 15 ml capped vial. Desorption was performed directly in the gas chromatograph injector port over 5 min at 250 °C using the splitless mode. The method is sensitive, with detection limits between 11 and 25 µg l^?1, precise, with variation coefficients in the range 1.28–3.71%, and linear over more than one order of magnitude. The related conditions were used for wine sample analyses with recoveries between 71.8 and 90.9%. Solid‐phase microextraction remains an attractive alternative technique due to its rapidity and because it is a solvent‐free extraction. Copyright © 2005 Society of Chemical Industry     

Elemental content of commercial ‘ready to-feed’ poultry and fish based infant foods in the UK

The study reported herein was conducted in order to establish the concentration of 20 essential and non-essential elements in a representative range of commercial infant foods in the UK targeted for infants aged between 6–12 months. The primary objective of this study was to examine the nutritive values and safety of such complementary infant foods on the UK market in relation to dietary and safety guidelines. Quantitative analyses were conducted on eight different products representing four popular brands (poultry and fish based) of ready to-feed infant foods currently on sale in the UK. Six essential elements, namely: calcium, iron, magnesium, potassium, sodium and zinc were determined by ICP-OES. The concentrations of six essential trace elements (selenium, molybdenum, cobalt, copper, chromium, manganese) and eight non-essential, potentially toxic, elements (arsenic, barium, nickel, cadmium, antimony, lead, mercury, aluminium) were determined by ICP-MS due to the higher sensitivity required. The total daily intakes of essential and trace elements from the consumption of such products were then estimated, based on the results of this study, and were referenced to the Recommended Nutrient Intake (RNI) values and safety guidelines for 6–9 months old children. Based on these comparisons the concentration of essential, except for potassium, and trace elements were found to be inadequate in meeting the RNI. In terms of the risk of exposure to toxicity, the concentration of toxic elements in ready to feed products analysed in this study, were not considered to be of concern. These results suggest that commercial complementary infant foods on the UK market may not contain minimum levels of minerals required for labelling declaration of micronutrient content (Commission Directive 2006/125/EC). This provides opportunities and scope for product optimisation to improve their nutritive value.     

Response surface optimization of SPME extraction conditions for the analysis of volatile compounds in Brazilian sugar cane spirits by HS‐SPME‐GC–MS

The extraction of volatile compounds from distilled sugarcane spirits was investigated using central composite design associated with response surface methodology. The parameters evaluated were the extraction temperature, extraction time and desorption time. All of the parameters analysed, as well as their interactions, were significant for the process at a 95% confidence level. Although the extraction time and extraction temperature exhibited positive effects, the desorption time showed a negative effect. The second‐order polynomial model was adjusted appropriately for the response surface analysis. The optimized conditions were extraction temperature equal to 45°C, extraction time of 50 min and the desorption time corresponding to 100 s. Copyright © 2017 The Institute of Brewing & Distilling     

Efficacy of neutral electrolyzed water for sanitization of cutting boards used in the preparation of foods

The effectiveness of neutral electrolyzed water (NEW) to sanitize cutting boards used for food preparation was investigated. Cutting boards made of hardwood and bamboo were inoculated with Escherichia coli K12 and Listeria innocua, dried for 1 h, washed, rinsed and sanitized with NEW, sodium hypochlorite (NaClO) solution, or tap water (control). After each washing protocol, surviving bacterial populations were determined. Results showed that both NEW and NaClO sanitizing solutions produced similar levels of bacterial reductions. In manual washing, the population reductions by NEW and NaClO were 3.4 and 3.6 log₁₀ CFU/100 cm² for E. coli, and 4.1 and 3.9 log₁₀ CFU/100 cm² for L. innocua, respectively. In the automatic washing, the reductions by NEW and NaClO were 4.0 and 4.0 log₁₀ CFU/100 cm² for E. coli, and 4.2 and 3.6 log₁₀ CFU/100 cm² for L. innocua, respectively. No significant differences (P > 0.05) were observed in surviving bacteria counts when comparing board material types.     

An improved method for the measurement of 3‐monochloropropanediol esters by matrix solid‐phase dispersion supported liquid–liquid extraction

3‐Monochloropropanediol (3‐MCPD) esters are contaminants produced from the high‐temperature processing of edible oils. The accurate measurement of 3‐MCPD using an easy‐to‐follow and reliable method that uses a readily available instrument is important. Here, we report an acid transesterification heptafluorobutyrylimidazole (HFBI) derivatisation method for the accurate measurement of 3‐MCPD esters in edible oils. We developed a dispersed matrix solid‐phase supported liquid–liquid extraction (DMSP‐SLE) system to remove impurities. Both the transesterification and DMSP‐SLE conditions were optimised. A good linear relationship was obtained within the range of 0.05–10 mg kg^?1 (R² ≥ 0.999) in both blank solvent and an oil sample. The limit of detection was 20.36 μg kg^?1. The average recovery of the 3‐MCPD esters spiked at 0.5, 1.0 and 2.0 mg kg^?1 into a blank oil matrix was in a range from 105.09 ± 2.77% to 120.16 ± 10.88%. The method we developed was further confirmed by performing detection on a Food Analysis Performance Assessment Scheme (FAPAS) sample.     

Existing and potential applications of ultraviolet light in the food industry – a critical review

Short‐wave ultraviolet light (UVC, 254 nm) can reduce dramatically the microbial load in air or on hard surfaces free from food residues, and can eliminate pathogens from potable water filtered to remove organic residues and ‘clumps’ of bacteria. More recently, approval of the Food and Drug Administration (USA) has been sought for a system for the destruction of pathogenic bacteria in fruit juices using UVC, and the same approach could perhaps be applied to remove spoilage organisms from cider or wines. In contrast, long‐wave UV light (UVA, >320 nm) has limited microbiocidal properties, and for practical applications its effectiveness has to be enhanced by the presence of photosensitive compounds (eg furocoumarins) that will diffuse into a microbial cell prior to irradiation. The penetration of UVA into water is better than that of UVC, and its bacteriocidal action in the presence of photosensitisers can be rapid. However, pure furocoumarins are expensive and their addition to foodstuffs might be questioned on safety grounds. © 2000 Society of Chemical Industry     

不断完善预合金粉末的性能,满足金刚石工具的应用（上）

随着预合金粉末在金刚石工具中使用量的增加,使用范围的不断扩大,不断完善预合金粉末的性能,进一步满足金刚石工具应用的需求,具有重大作用与意义。在预合金粉末生产方法中：湿法冶金方法生产的预合金粉,广泛并成功地应用在国外,但成本高,在国内市场应用较少。机械合金化方法多用于科研中,批量生产能耗大。在国内主要采用气雾化、水雾化、多金属化学共沉积法等生产预合金粉末。文章探讨了氧含量对金刚石工具性能的影响;介绍了国内不同生产设备条件下的还原工艺,进一步提出不断完善预合金粉性能的各种途径,以满足金刚石工具应用的需求。