Application of a potentiometric electronic tongue as a classification tool in food analysis

This paper reports on the application of a potentiometric sensor array to the food analysis field, in order to distinguish simple tastes and to classify food samples. This array is formed by a set of non-specific all-solid-state potentiometric sensors and has been used in combination with principal component analysis (PCA) for the classification of food samples in batch and in flow injection mode. First attempt was to classify synthetic samples prepared with controlled variability. Once this ability is proven, satisfactory classification results are presented for commercial waters, orange-based drinks and tea samples. An interesting correlation is achieved between the natural juice content and its first calculated component, which allows for a very simple tool for screening purposes.     

Determination of beauvericin and four other enniatins in grain by liquid chromatography-mass spectrometry

A method is described using LC-MS-MS for the detection of five different enniatins in grain. The method involves extraction of the fungal secondary metabolites using acetonitrile-water and quantification using LC-MS-MS with atmospheric pressure chemical ionisation, without further treatment of sample extracts. The selected ion reaction of [M + NH4]+ to [M + H]+ was utilised in the specific detection of the compounds. Mean recoveries (n = 5-12) of enniatins from spiked grain samples over a period of six months were 99-115%, 86-131%, 97-113%, 73-100% and 78-114% for beauvericin, enniatin A, A1, B and B1, respectively. The limits of detection were 3.0 microg/kg for beauvericin, enniatin A, B and B1 and 4.0 microg/kg for enniatin A1, which corresponds to on-column detection limits of 7.5 pg and 10 pg, respectively.     

Sensorial analysis evaluation in cereal bars preserved by ionizing radiation processing

Gamma-rays utilized as a food-processing treatment to eliminate insect contamination is well established in food industries. Recent troubles in Brazilian cereal bars commercialization require a special consumer's attention because some products were contaminated by insects. To solve the problem, food-irradiation treatment was utilized as a safe and effective solution. The final product was free of insect contamination. The aim of this study was to determine the best radiation dose processing utilized to disinfestations and detect some change on sensorial characteristic by sensorial analysis in cereal bars. In this study, three different kinds of cereal bars were purchased in São Paulo (Brazil) in supermarkets and irradiated with 1.0, 2.0 and 3.0 kGy at “Instituto de Pesquisas Energéticas e Nucleares” (IPEN-CNEN/SP). The samples were treated with ionizing radiation using a ⁶⁰Co gamma-ray facility (Gammacell 220, A.E.C.L.). That radiation doses were used successfully as an anti-insect treatment in the cereal bars, since in some food industries doses up to 3.0 kGy are used to guarantee at least a dose of 1.0 kGy in internal cereal bars package. Sensorial analysis was necessary since cereal bars contain ingredients very sensitive to ionizing radiation process.     

微量元素与环境

根据近年环境科学研究的进展，概述了微量元素在环境系统中迁移、转化的条件与物理化学作用，形成微量元素在环境系统中的分布规律与区域地理特征。比较了环境背景值与污染物在环境中含量值的差异，经历了生物系统对微量元素的富集、遗传、积累，并通过食物链摄入人体，形成生命元素。由于某些生命元素值的异常，引起人体相关的疾病．由此可见，人体微量元素与环境有极密切的关系．     

Fluorimetric determination of pantothenic acid in foods by liquid chromatography with post-column derivatization

A method to determine the content of free pantothenic acid in various foods by reverse phase liquid chromatography-fluorimetry is reported. It includes a purification of the samples by successive passages through anion and cation exchange cartridges and a post-column derivatization of pantothenic acid as the fluorescent 1-alkylthio-2-alkylisoindole (reaction of beta-alanin, formed by hot alkaline hydrolysis of pantothenic acid, with orthophthaldialdehyde in the presence of 3-mercaptopropionic acid). An enzymatic hydrolysis prior to the purification step (pepsin at 50 degrees C for 3 h, then pantetheinase and alkaline phosphatase at 20 degrees C for 18 h) made it possible to release the bound pantothenic acid and thus to obtain the total Vitamin B5 content of these foodstuffs. The method proposed for the determination of free and bound pantothenic acid gives a good recovery rate (96-101%) and a satisfactory repeatability (R.S.D.r less than 8%). Owing to its low detection limit (0.65 microg g(-1)) and the good resolution of the pantothenic acid peak, it could most probably be applied to the determination of this vitamin in any foodstuff.     

Food irradiation—US regulatory considerations

The use of ionizing radiation in food processing has received increased interest as a means of reducing the level of foodborne pathogens. This overview discusses the regulatory issues connected with the use of this technology in the United States. Several recent changes in the FDA's review process are discussed. These include the current policy that utilizes an expedited review process for petitions seeking approval of additives and technologies intended to reduce pathogen levels in food, and the recent USDA rule that eliminates the need for a separate rulemaking process by USDA for irradiation of meat and poultry. Recently promulgated rules and pending petitions before the FDA associated with the use of ionizing radiation for the treatment of foods are also discussed along with the current FDA labeling requirements for irradiated foods and the 1999 advanced notice of proposed rule on labeling. Another issue that is presented is the current status of the approval of packaging materials intended for food contact during irradiation treatment of foods.     

Pesticide residue analysis in foodstuffs applying capillary gas chromatography with atomic emission detection State-of-the-art use of modified multimethod S19 of the Deutsche Forschungsgemeinschaft and automated large-volume injection with programmed-temperature vaporization and solvent venting

Atomic emission detection (AED) provides high element-specific detection of all compounds amenable to gas chromatography (GC). The heteroatoms nitrogen, chlorine, phosphorus, sulfur, bromine and fluorine, which are important elements in pesticide residue analysis, are of major interest. A main drawback of AED is its lower sensitivity with respect to other selective detection methods used in pesticide residue analysis such as electron-capture and nitrogen-phosphorus detection. This holds true especially for the important nitrogen trace. For this reason, more sensitive detection can be achieved by injection of larger volumes or higher concentrations of sample extracts, because matrix compounds were usually registered only in the carbon, hydrogen and oxygen traces. This paper focuses on recent developments from the authors' laboratory in order to demonstrate the feasibility of screening analyses with the identification of pesticide residues down to the 0.01 ppm concentration level in plant foodstuffs. This has been achieved by means of automated large volume injection with programmed-temperature vaporization and solvent venting as well as careful optimization of make-up and reactant gases with AED. Clean up follows the principle of multimethod S19 of the Deutsche Forschungsgemeinschaft in a reduced procedure. After elimination of lipids and waxes by gel permeation chromatography, extracts from 10 g of the food samples were concentrated to 200 μl, of which 12.5 μl were introduced into the GC-AED system. Two analyses were usually performed with the element traces of sulfur, phosphorus, nitrogen and carbon in the first run and chlorine and bromine in the second run. Fluorine and oxygen were not detected in any screening analyses. The method has proved to be of great value especially with “problem foodstuffs”. The limits of detection were determined for 385 pesticides and are presented together with their retention data.     

Development of a standard for the organization of the interlaboratory comparisons in microbiology of food

The ILAC G13 Guide and the ISO IEC Guide 43-1 are the common, general and horizontal bases for accreditation of providers of proficiency testing and interlaboratory comparisons used by several accreditation bodies. Despite their widespread use, these guides omit specific technical requirements, and sometimes even elements of quality management, clearly defined for the organization of proficiency-testing schemes for microbiology of food. The Sub-Committee 9 “Microbiology of food” of ISO TC34 has created a working group (WG4) to establish a standard detailing such specific requirements for microbiology of food. This technical standard will describe those specific requirements of proficiency testing which organizers of proficiency-testing schemes and any subcontractors must satisfy in addition to the requirements of the ILAC G13 Guide and the ISO IEC Guide 43-1 to achieve accreditation or other recognition.     

Enzymatic assay technique for the determination of aspartame

An enzymatic assay technique was developed for the determination of the artificial sweetener aspartame. The peptide bond of aspartame was first cleaved by peptidase to release aspartic acid. In the presence of α-ketoglutarate, aspartic acid was then transaminated by aspartate aminotransferase to glutamate. The reaction was monitored by following the oxygen consumption during the enzymatic oxidation of glutamate by glutamate oxidase. A linear relationship between oxygen consumption and aspartame concentration up to 200 μM was obtained. The assay technique was applicable to the determination of aspartame in a variety of dietary food products. The results obtained agreed well with those determined by liquid chromatography and those reported by the product manufacturers.     

Development of methods for testing barriers in food packaging materials

In some countries recycled materials are not allowed to come into contact with food without a protective layer such as plastic or virgin fiber. The purpose of this kind of barrier is to reduce migration of substances form beyond the barrier to the food. Two methods for studying a functional barrier are described. Both utilize migration cells in which one surface of the test specimen (for example a paper plate) is exposed to the food simulant. The first method involves the addition of indidcatsor substances to the non-food contact layer. The second method is to measure the migration of substances originally present in the layers beyond the functional barrier layer. Several kinds of barrier used in commercial papaer plates were studied and differences between them were found.