Delivery systems for liquid food products

One of the present challenges of the food industry is to deliver nutrition and health benefits to the consumer while keeping, or improving the taste and aroma impact. Adding active ingredients to liquid food products for fortification is in most cases not possible or not sufficient to achieve the desired goal, due to the fact that many interesting micronutrients are only hardly soluble in aqueous systems and show (i) a limited stability against chemical or physical degradation, (ii) an incompatibility between the active ingredient and the food matrix, or (iii) reveal an uncontrolled release or bioavailability. Therefore, encapsulation systems, also denoted as ‘delivery systems’, are typically used to solve these formulation problems. The task to find the appropriate delivery system is especially challenging for the food industry compared to other fields such as pharmacy, medical products or cosmetics, since only a limited amount of ingredients can be used as encapsulation and stabilization material. In the present review we will discuss the delivery systems available for (semi)-liquid foods and comment on existing advantages and limitations. The remaining technical challenges to solve in the future concern mainly the facts that (i) most of the available delivery systems for aqueous products do not yet allow to significantly stabilize degradation sensitive ‘encapsulated’ active ingredients against e.g. oxidation, (ii) the ‘encapsulation’ (solubilization) capacity of some delivery systems is still quite poor and (iii) off-taste generation is possible above certain concentrations of added delivery systems.     

Determination of methylcellulose and hydroxypropyl methylcellulose food gums in food and food products: collaborative study

A collaborative study was performed to determine the reproducibility of a method for the determination of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) in food. These widely used food gums possess unusual solubility characteristics and cannot accurately be determined by existing dietary fiber methods. The new method uses the enzyme-digestion procedure of AOAC Official Method 991.43. Digestate solutions must be refrigerated to fully hydrate MC or HPMC. The chilled solutions are filtered and analyzed by size-exclusion liquid chromatography. Collaborating laboratories received 28 samples containing MC or HPMC in the range of 0-100%. The sample set included blind duplicates of 5 food matrixes (bread, milk, fish, potato, and powdered juice drink). Cochran and Grubbs tests were used to eliminate outliers. For food samples containing MC, values for within-laboratory precision, repeatability relative standard deviation (RSDr), ranged from 4.2 to 16%, and values for among-laboratories precision, reproducibility relative standard deviation (RSDR), ranged from 11 to 20%. For HPMC samples, RSDr values ranged from 6.4 to 27%, and RSDR values ranged from 17 to 39%. Recoveries of MC and HPMC from the food matrixes ranged from 78 to 101%. These results show acceptable precision and reproducibility for the determination of MC and HPMC, for which no Official AOAC Methods exist. It is recommended that this method be adopted as AOAC Official First Action.     

Determination of aflatoxins in food products by chromatography.

Several chromatographic methods for the determination of aflatoxins in agricultural and food products are reviewed. During the past two decades, identification and determination of aflatoxins were done by thin-layer chromatography (TLC) because it was easy, fast and inexpensive. However, high-performance liquid chromatography (HPLC) using fluorescence detection is now the method of choice for determining aflatoxins and is also growing in popularity for their identification. The reasons for selecting HPLC over TLC can be summarized as the ability to analyze for a wide variety of compounds, including compounds that are easily degraded by heat, light or air, the ease of adaptation to confirmatory procedures, the potential for automation and the dramatic improvement in instrumentation, including the development of increasingly sensitive fluorescence and electrochemical detectors and short, high-resolution, reversed-phase columns.     

Chemometric methods in NMR spectroscopic analysis of food products

The main achievements of high-resolution NMR spectroscopy in combination with different chemometric methods in the analysis of food products in the last 40 years are reviewed. The essence of chemometric methods used for the analysis and interpretation of NMR spectra is briefly described. Sample preparation for NMR-spectroscopic analysis is characterized. Methods for the mathematical treatment of NMR spectra (smoothing, Fourier transformation, bucketing, normalization, and selection of spectral ranges) are considered. Currently available methods for the suppression of the signals of macrocomponents, including those for the simultaneous suppression of several signals, are described. The results are illustrated based on examples of analysis of different classes of foodstuffs and beverages with the use of NMR spectroscopy and chemometric methods for classification and discrimination (geographical and botanical origin as well as validating checking the brand authenticity).     

催化荧光动力学法测定食品中痕量甲醛

基于在酸性条件中,甲醛催化KBrO3氧化吡口罗红B的褪色反应,使其荧光猝灭,建立了荧光动力学法测定痕量甲醛的新方法。反应在沸水浴中进行8 min,测定甲醛的线性范围为0.016~0.14 mg/L,检出限为8.6×10-6g/L。该方法用于水发食品中甲醛的测定,并进行了加标回收试验,回收率在96.0%~104.2%之间,相对标准偏差为1.7%~3.5%。     

Chromatographic methods for the determination of mycotoxins in food products

Chromatographic methods for the determination of mycotoxins from different classes in food products of plant and animal origins are surveyed. The procedures of sample preparation and extract purification and the use of various chromatographic analysis techniques are considered.     

Determination of hydroxycarboxylic acids in food products by capillary electrophoresis

A procedure for the capillary-electrophoretic determination of lactic, malic, tartaric, and citric acids in food products was developed. The use of 3-nitrobenzoic acid as a light-absorbing component of the running buffer was proposed for the indirect photometric detection of these substances. This considerably increased the determination sensitivity (up to n × 10 ??g/L), as compared with currently available analogs. The composition of the running buffer was optimized: 3-nitrobenzoic acid, 10 mM; cetyltrimethylammonium bromide, 0.5 mM; EDTA, 0.1 mM; and monoethanolamine, to pH 5.3. The procedure was tested with the samples of food products: fruits, juices, nectars, wines, beer, etc. The accuracy of the analytical results was confirmed by the standard addition method.     

Determination of egg proteins in food products by enzyme immunoassay

An enzyme-linked immunosorbent assay (ELISA) was developed to determine the presence of egg proteins in foods. The polyclonal antibodies developed were specific to whole egg proteins and did not cross-react with any of the 38 nuts, legumes, or other common food ingredients tested. The concentrations of egg proteins that will inhibit 50% of antibody-antigen binding, IC50, were 3-7 ng/mL, and the linear range was 0.5-62.5 ng/mL. The detection limit was 0.2 ppm for various foods. Recoveries ranged from 67 to 96%. The intra- and inter-assay coefficients of variation in this procedure were 10-13% for ice cream spiked at 0.8 and 1.6 ppm. The ELISA has been applied to ice creams, noodles, pasta, and breads. Egg proteins were identified in all declared egg products, and no false positives were found.     

Solid phase microextraction associated with microwave assisted extraction of food products

Veltol® (2-methyl 3-hydroxy 4-pyrone) and Veltol-Plus® (2-ethyl 3-hydroxy 4-pyrone) are patented flavor ingredients in food products. Only Veltol® can occur naturally, but both Veltol® and Veltol-Plus® are often added to food products. In order to monitor the use of these compounds in food products, lower detection limits were needed. The Solid Phase Microextraction (SPME) technique for beverages and SPME coupled with Microwave Assisted Extraction (MAE) for solid food samples were studied. The influence of the pH, salt content, SPME adsorption time, GC inlet conditions, and the conditioning of the SPME fiber were investigated. Different food products were tested including coffee, beverages, chewing gums and potato chips. The coupled MAE and SPME shows good results for solid food samples. The reproducibility of the technique was less than 13%RSD and the detection limit was 10 ppb for Veltol® and 2 ppb for Veltol-Plus® using the SIM mode in GC/MS. The technique also shows good selectivity for the target compounds investigated in different food samples.     

Microfluidic based impedance biosensor for pathogens detection in food products

A MEMS‐based impedance biosensor was designed, fabricated, and tested to effectively detect the presence of bacterial cells including E. coli O157:H7 and Salmonella typhimurium in raw chicken products using detection region made of multiple interdigitated electrode arrays. A positive dielectrophoresis based focusing electrode was used in order to focus and concentrate the bacterial cells at the centerline of the fluidic microchannel and direct them toward the detection microchannel. The biosensor was fabricated using surface micromachining technology on a glass substrate. The results demonstrate that the device can detect Salmonella with concentrations as low as 10 cells/mL in less than 1 h. The device sensitivity was improved by the addition of the focusing electrodes, which increased the signal response by a factor between 6 and 18 times higher than without the use of the focusing electrodes. The biosensor is selective and can detect other types of pathogen by changing the type of the antibody immobilized on the detection electrodes. The device was able to differentiate live from dead bacteria.     

Rapid phase-compositional assessment of lipid-based food products by time domain NMR

In food science and technology, assessment of phase-compositional behaviour of lipids is critical for understanding many product properties and for effective process control. Time Domain NMR is a rapid and easy-to-handle technique, and is already well appreciated as a tool for phase-compositional assessment in foods. The phase-compositional detail that can be obtained with the established methodology is limited, however. In this work, we set out to obtain more phase-compositional details of lipids as currently feasible with the already established 'classical' NMR methods. We deployed a combined FID-CPMG experiment, and analyzed the Transversal Relaxation Decays by Deconvolution (TRDD) with semi-empirical mathematical functions for solid, semi-solid and liquid components. Within the solid component, different lipid crystal polymorphs can be discerned in a quantitative manner, i.e. alpha, beta and beta'. The TRDD method was validated against established NMR SFC methods, in terms of accuracy ('trueness') and precision. The solid fat content (SFC) of a large collection of fat blends was measured by the commonly employed NMR Direct and Indirect SFC methods and a good correlation with the results of the TRDD was observed, thereby demonstrating accuracy. Furthermore, TRDD was found to be equally precise as the established NMR SFC methods.     

Determination of Alachlor in food products by a fluorescence polarization immunoassay

A procedure for the determination of Alachlor in liquid media using a fluorescence polarization immunoassay (FPIA) was developed. The effects of the structure and purification degree of a tracer (analyte with a fluorescent label) on the analytical signals, sensitivity, and selectivity in the determination of Alachlor were studied. The tracer-antibody binding constants (K _T) and antigen-antibody binding constants (affinity constants K _Af) were calculated, and optimum immunoreagent pairs for the determination of Alachlor were chosen. The calibration graph was linear over the Alachlor concentration range 0.01–1.0 μg/mL; the detection limit was 8 ng/mL. The procedure was tested in the analysis of model solutions and soy-containing food products (sausages). Original Russian Text ? Yu.V. Nartova, T.N. Ermolaeva, M.R. Fleisher, R. Abuknesha, S.A. Eremin, 2008, published in Zhurnal Analiticheskoi Khimii, 2008, Vol. 63, No. 5, pp. 546–552.     

食品中反式脂肪酸分析方法的研究进展

食品中反式脂肪酸(TFAs)对人体健康有重要影响,因此日益受到人们的关注。针对TFAs的分析方法较多,包括光谱分析、色谱分析、质谱分析和电泳分析等。本文就目前报道的TFAs检测方法进行了综述,并详细介绍了各种方法的优缺点及其在相关食品分析中的应用。     

System of piezosensors for prognostication of the storage life of food products

System of sensors operating on the piezoquartz microweighing principle was employed to forecast the storage life of food products based on milk serum. Signals from the sensors are integrated into an output signal forming a recognizable “visual pattern” of an odor.     

Rapid analysis of food products by means of high speed gas chromatography

Since the invention of GC, there has been an ever increasing interest within the chromatographic community for faster GC methods. This is obviously related to the fact that the number of samples subjected to GC analysis has risen greatly. Nowadays, in routine analytical applications, sample throughput is often the most important aspect considered when choosing an analytical method. Gas chromatographic instrumentation, especially in the last decade, has been subjected to continuous and considerable improvement. High-speed injection systems, electronic gas pressure control, rapid oven heating/cooling and fast detection are currently available in a variety of commercial gas chromatographs. The main consequence of this favourable aspect is that high-speed GC is being increasingly employed for routine analysis in different fields. Furthermore, the employment of dedicated software makes the passage from a conventional to a fast GC method a rather simple step. The present review provides an overview of the employment of fast GC techniques for the analysis of food constituents and contaminants. A brief historical and theoretical background is also provided for the approaches described.