Analysis of corn and sorghum flour mixtures using laser-induced breakdown spectroscopy.

BACKGROUND: In a world constantly challenged by climate change, corn and sorghum are two important grains because of their high productivity and adaptability, and their multifunctional use for different purposes such as human food, animal feed, and feedstock for many industrial products and biofuels. Corn and sorghum can be utilized interchangeably in certain applications; one grain may be preferred over the other for several reasons. The determination of the composition corn and sorghum flour mixtures may be necessary for economic, regulatory, environmental, functional, or nutritional reasons. RESULTS: Laser-induced breakdown spectroscopy (LIBS) in combination with chemometrics, was used for the classification of flour samples based on the LIBS spectra of flour types and mixtures using partial least squares discriminant analysis (PLS-DA) and the determination of the sorghum ratio in sorghum / corn flour mixture based on their elemental composition using partial least squares (PLS) regression. Laser-induced breakdown spectroscopy with PLS-DA successfully identified the samples as either pure corn, pure sorghum, or corn-sorghum mixtures. Moreover, the addition of various levels of sorghum flour to mixtures of corn-sorghum flour were used for PLS analysis. The coefficient of determination values of calibration and validation PLS models are 0.979 and 0.965, respectively. The limit of detection of the PLS models is 4.36%. CONCLUSION: This study offers a rapid method for the determination of the sorghum level in corn-sorghum flour mixtures and the classification of flour samples with high accuracy, a short analysis time, and no requirement for time-consuming sample preparation procedures. © 2020 Society of Chemical Industry.

Discrimination of milk species using Raman spectroscopy coupled with partial least squares discriminant analysis in raw and pasteurized milk.

BACKGROUND: Heat treatment is the most common practice for the microbiological safety of milk; hence, determination of the heat treatment of milk is essential. Also, mislabeling or adulteration of expensive milk samples, like ewe or goat milk, with cow's milk is a growing problem in the dairy market. Thus, the determination of the authenticity of milk samples has crucial importance for both producers and consumers. The aim of this study was to discriminate milk samples using Raman spectroscopy with partial least squares discriminant analysis (PLS-DA), first with regard to whether the milk was heat-treated or not, and second with regard to species (cow, goat, ewe, mixture (adulterated)) in both raw and pasteurized milk. RESULTS: First, discrimination of milk samples as raw or pasteurized was achieved using PLS-DA. Both in calibration and prediction models, high sensitivity and specificity values were obtained for raw and pasteurized milk samples. Second, the proposed method also discriminated milk samples according to their species (cow, goat, ewe, and mixture) for both raw and pasteurized milk. In both calibration and prediction models, the sensitivity and specificity values were above 0.857 and 0.897 respectively. Also, the accuracy values were above 0.915. The results obtained denote satisfactory accurate classification of the samples. CONCLUSION: The results suggest that Raman spectroscopy coupled with PLS-DA can be successfully used to discriminate milk samples according to heat treatment (raw/pasteurized) and their species within 20 s per sample. It was seen that Raman spectra provide valuable information to be used especially for discrimination of milk samples according to their origin. © 2020 Society of Chemical Industry.

Determination of liquid egg composition using attenuated total reflectance Fourier transform infrared spectroscopy and chemometrics.

BACKGROUND: The use of liquid whole egg (LWE) in the food industry as a substitute for shell eggs has been on the increase lately. Since the composition of LWE can easily be changed, determination of protein, lipid, moisture and total soluble solid (TSS) contents of LWE has also gained importance. Traditional methods usually require more time and effort, and the use of toxic chemicals for sample preparation; hence more efficient techniques (faster, cheaper and more reliable) are needed. In this regard, a novel technique that determines LWE components using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy with partial least squares regression (PLS) is presented in this study. RESULTS: The actual values of LWE components were determined by applying reference methods. The accuracy of the PLS model was demonstrated by comparing the obtained predictions with the actual values of the components. High coefficients of determination values, which are 0.950, 0.992, 0.994 and 0.972, were achieved for protein, lipid, moisture, and TSS validation datasets, respectively. The error values, namely RMSEC, RMSECV and RMSEP, were obtained in the ranges 0.404-0.978, 0.57-1.82 and 0.83-1.84, respectively. CONCLUSIONS: ATR-FTIR spectroscopy coupled with chemometrics can provide a rapid and sensitive method for quality control of liquid egg composition. © 2019 Society of Chemical Industry.

Detection of Pistacia vera adulteration by using laser induced breakdown spectroscopy.

BACKGROUND: Pistachio has high economic value because of its high consumption rate and consumer demand. Therefore, it has become an important target for adulteration. Green pea and spinach are the most frequently used foods for pistachio adulteration as a result of their kernel color. The present study aimed to detect pistachio adulteration with green pea and spinach samples using laser induced breakdown spectroscopy (LIBS) combined with chemometric methods. RESULTS: In the first step of the study, principal component analysis was employed for qualitative analysis of pure pistachio, green pea, spinach and adulterated pistachio samples, and discrimination was achieved successfully. A score plot clearly discriminating pure pistachio, green pea and spinach samples, as well as their blind samples, was drawn using principle component (PC)1 and PC2 which explained 86.86% and 12.16% of the variance, respectively. The results showed that the calibration curve for green pea adulterated pistachio provides successful determination of adulteration level and had an R2 of 0.995 and a limit of detection (LOD) of 2.04%, whereas the calibration curve for spinach adulterated pistachio had an R2 of 0.993 and a LOD of 1.64%. CONCLUSION: The results of the present study demonstrate that LIBS with the chemometric methods showed a good performance based on the high value of prediction accuracy for pistachio adulteration. This technique has high potential as a rapid method for pistachio identification and detection of adulteration. © 2018 Society of Chemical Industry.

Quantitative Characterization of Magnetic Mobility of Nanoparticle in Solution-Based Condition.

Magnetic nanoparticles are considered as the ideal substrate to selectively isolate target molecules or organisms from sample solutions in a wide variety of applications including bioassays, bioimaging and environmental chemistry. The broad array of these applications in fields requires the accurate magnetic characterization of nanoparticles for a variety of solution based-conditions. Because the freshly synthesized magnetic nanoparticles demonstrated a perfect magnetization value in solid form, they exhibited a different magnetic behavior in solution. Here, we present simple quantitative method for the measurement of magnetic mobility of nanoparticles in solution-based condition. Magnetic mobility of the nanoparticles was quantified with initial mobility of the particles using UV-vis absorbance spectroscopy in water, ethanol and MES buffer. We demonstrated the efficacy of this method through a systematic characterization of four different core-shell structures magnetic nanoparticles over three different surface modifications. The solid nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and saturation magnetization (Ms). The surfaces of the nanoparticles were functionalized with 11-mercaptoundecanoic acid and bovine serum albumin BSA was selected as biomaterial. The effect of the surface modification and solution media on the stability of the nanoparticles was monitored by zeta potentials and hydrodynamic diameters of the nanoparticles. Results obtained from the mobility experiments indicate that the initial mobility was altered with solution media, surface functionalization, size and shape of the magnetic nanoparticle. The proposed method easily determines the interactions between the magnetic nanoparticles and their surrounding biological media, the magnetophoretic responsiveness of nanoparticles and the initial mobilities of the nanoparticles.

Ultrasensitive and selective homogeneous sandwich immunoassay detection by Surface Enhanced Raman Scattering (SERS).

In this report, a simple and highly selective homogeneous sandwich immunoassay was developed for ultrasensitive detection of Staphylococcal Enterotoxin B (SEB) using Surface Enhanced Raman Scattering (SERS). The assay uses polyclonal-antibody functionalized magnetic gold nanorod particles as capture probes for SEB, which can be collected via a simple magnet. After separating SEB from the sample matrix, they are sandwiched by using binding-specific antibody-antigen pairs with the help of gold nanorod particles. Gold nanorod particles are bifunctional by design and contain self-assembled monolayers (SAMs) of a SERS tag molecule (5,5-dithiobis (2-nitrobenzoic acid), DTNB) and carboxylic functionalities of DTNB for coupling with a suitable antibody. The correlation between the SEB concentration and SERS signal was found to be linear within the range of 3 fM to 0.3 µM. The limit of detection for the assay was determined to be 768 aM (ca., 9250 SEB molecules per 20 µL sample volume). The gold heterogeneous assay system for SEB detection was also compared with the same SERS probes and gold-coated surfaces as capture substrates. The developed method was further evaluated for detecting SEB in artificially contaminated milk. Finally, the method was used for investigating the SEB specificity on bovine serum albumin (BSA) and avidin.

Detoxification of aflatoxin B1 and patulin by Enterococcus faecium strains.

Aim of the present study was to investigate the detoxification of aflatoxin B(1) and patulin from aqueous solution by probiotic culture of Enterococcus faecium M74 and commercial culture of E. faecium EF031. The effect of the bacterial viability, incubation time and pH of the medium on the binding ability was tested. Also, binding stability was determined by washing the bacteria-mycotoxin complexes with phosphate buffer saline. Both M74 and EF031 strains have the ability to remove aflatoxin B(1) and patulin. While M74 removes 19.3 to 30.5% of aflatoxin B(1) and 15.8 to 41.6% of patulin, EF031 removes 23.4 to 37.5% of aflatoxin B(1) and 19.5 to 45.3% of patulin throughout a 48 h incubation period. The removal of aflatoxin B(1) and patulin was highest at pH 7.0 and 4.0, respectively. The stability of the aflatoxin B(1) and patulin complexes formed with the bacterial strains was found to be high. The viability of the bacteria did not have any significant effect on the detoxification of aflatoxin B(1) and patulin. Detoxification properties of E. faecium could represent new strategies for a possible application in the human diet and animal feed.

Determination of viable Escherichia coli using antibody-coated paramagnetic beads with fluorescence detection.

A rapid and convenient assay system was developed to detect viable Escherichia coli in water. The target bacteria were recovered from solution by immunomagnetic separation and incubated in tryptic soy broth with isopropyl-beta-D-thiogalactopyranoside, which induces formation of beta-galactosidase in viable bacteria. Lysozyme was used to lyse E. coli cells and release the beta-galactosidase. Beta-galactosidase converted 4-methylumbelliferyl-beta-D-galactoside to 4-methylumbelliferone (4-MU), which was measured by fluorescence spectrophotometry using excitation and emission wavelengths of 355 and 460 nm, respectively. Calibration graphs of 4-MU fluorescence intensity versus E. coli concentration showed a detection range between 8 x 10(4) and 1.6 x 10(7) cfu mL(-1), with a total analysis time of less than 3 h. The advantage of this method is that it detects viable cells because it is based on the activity of the enzyme intrinsic to live E. coli.

Amperometric determination of live Escherichia coli using antibody-coated paramagnetic beads.

Detecting and enumerating fecal coliforms, especially Escherichia coli, as indicators of fecal contamination, are essential for the quality control of supplied and recreational waters. We have developed a sensitive, inexpensive, and small-volume amperometric detection method for E. coli beta-galactosidase by bead-based immunoassay. The technique uses biotin-labeled capture antibodies (Ab) immobilized on paramagnetic microbeads that have been functionalized with streptavidin (bead-Ab). The bead-Ab conjugate captures E. coli from solution. The captured E. coli is incubated in Luria Bertani (LB) broth medium with the added inducer isopropyl beta-D: -thiogalactopyranoside (IPTG). The induced beta-galactosidase converts p-aminophenyl beta-D: -galactopyranoside (PAPG) into p-aminophenol (PAP), which is measured by amperometry using a gold rotating disc electrode. A good linear correlation (R2 = 0.989) was obtained between log cfu mL(-1) E. coli and the time necessary to product a specific concentration of PAP. Amperometric detection enabled determination of 2x10(6) cfu mL(-1) E. coli within a 30 min incubation period, and the total analysis time was less than 1 h. It was also possible to determine as few as 20 cfu mL(-1) E. coli under optimized conditions within 6-7 h. This process may be easily adapted as an automated portable bioanalytical device for the rapid detection of live E. coli.