We developed a novel substrate for the collection of volatile organic compounds (VOCs) emitted fr... more We developed a novel substrate for the collection of volatile organic compounds (VOCs) emitted from either living or dried plant material to be analyzed by surface-enhanced Raman spectroscopy (SERS). We demonstrated that this substrate can be utilized to differentiate emissions from blends of three teas, and to differentiate emissions from healthy cotton plants versus caterpillar-infested cotton plants. The substrate we developed can adsorb VOCs in static headspace sampling environments, and VOCs naturally evaporated from three standards were successfully identified by our SERS substrate, showing its ability to differentiate three VOCs and to detect quantitative differences according to collection times. In addition, volatile profiles from plant materials that were either qualitatively different among three teas or quantitatively different in abundance between healthy and infested cotton plants were confirmed by collections on Super-Q resin for dynamic headspace and solid-phase microextraction for static headspace sampling, respectively, followed by gas chromatography to mass spectrometry. Our results indicate that both qualitative and quantitative differences can also be detected by our SERS substrate although we find that the detection of quantitative differences could be improved.
This study evaluated distillers grain (DG) by-products produced in different ethanol plants and s... more This study evaluated distillers grain (DG) by-products produced in different ethanol plants and supplemented in animal diets in Texas, based on samples analyzed from 2008 to 2014. The samples were assessed for concentration, occurrence, and prevalence of selected nutrients and contaminants. Protein and sulfur contents of DG were largely different between corn and sorghum by-products as well as wet distillers grain with solubles and dry distillers grain with solubles (DDGS), indicating a significant effect of grain feedstock and dry-grind process stream on DG composition and quality. Salmonella was isolated in 4 DDGS samples out of a total of 157 DG samples, a percentage (2.5%) that is much lower than the percentage of Salmonella-positive samples found in other feed samples analyzed during the same period. A small amount of virginiamycin residue was found in 24 corn DDGS, 1 corn wet distillers grain with solubles, and 2 sorghum DDGS samples out of 242 samples in total. One sorghum DD...
Salmonella species (spp.) are zoonotic pathogens that contaminate animal ingredients and finished... more Salmonella species (spp.) are zoonotic pathogens that contaminate animal ingredients and finished feed and represent a significant human food safety hazard as identified by the Codex Animal Feed Taskforce. The United States (US) Food and Drug Administration (FDA) has promulgated regulations prohibiting Salmonella contamination in feed and has published a guidance document expressing their current strategy involving regulatory oversight of Salmonella contamination in feed. The Office of the Texas State Chemist (OTSC) initiated the broad surveillance of Salmonella spp. in 2007, in response to a Salmonella enterica serotype Typhimurium outbreak in frozen rodents, which are subject to the agency’s regulatory oversight as defined by the Texas Commercial Feed Control Act. From calendar years of 2007-2011, 2622 total feed samples were collected and subsequently evaluated for Salmonella contamination using multiple screening methods, including polymerase chain reaction (PCR) and automated i...
In this work, novel ultrathin electrospun fibers from different blends of amaranth protein 17 iso... more In this work, novel ultrathin electrospun fibers from different blends of amaranth protein 17 isolate (API) and the carbohydrate polymer pullulan, with or without the surfactant 18 Tween80, have been developed and characterized. The solution properties and molecular 19 organization of the electrospun structures were studied and correlated with the morphology 20 of the obtained fibers. The presence of pullulan in the blends resulted in increased viscosity 21 and lower conductivity of the solutions, related to a better chain entanglement and decrease 22 in the polyelectrolyte protein character, respectively, both factors needed for fiber 23 formation. Infrared spectral changes indicated that defect-free fibers were correlated with 24 extended α-helical protein structures, which for the blends with greater protein contents, 25 was only obtained upon surfactant addition. The thermal stability of the hybrid fibers was 26 better than that of pure API and slightly increased upon surfactant addition, while the water 27 stability of the blends was highly dependent on fiber composition. These structures have a 28 great potential for the encapsulation of bioactives for functional food applications.
The spectroscopic method based on surface-enhanced Raman spectroscopy (SERS) technique combined w... more The spectroscopic method based on surface-enhanced Raman spectroscopy (SERS) technique combined with chemometric methods was developed for simple, cost-effective, and efficient analysis of chlorpyrifos (CPF) and aldicarb (ALD) pesticide residues in animal feed. Animal feeds free from the pesticides were spiked at different concentrations of CPF (0-20 mg/kg) and aldicarb (0-100 µg/kg). Gold nanoparticles were mixed with sample extract for SERS measurement. A significant spectral difference induced by the presence and different level of CPF and ALD concentration in animal feed was observed between the pesticide spiking groups. Different chemometric models applied on training datasets showed excellent classification rates (100 percent) while the models on external validation dataset exhibited lower correct classification rates (50.0-76.7 percent) with no false-negative error. The selected chemometric models for CPF and ALD quantification also showed a high predictive ability and performance. The developed models displayed no statistical significant difference between model predicted and reference values in the external validation dataset (p < 0.01). The study results indicate that the SERS spectroscopic method could be an effective and efficient analytical tool for pesticide analysis in highly complex animal feed matrices for screening at a point of sampling to improve food and feed safety.
Aflatoxin contamination in maize represents a significant food safety hazard in Kenya. To manage ... more Aflatoxin contamination in maize represents a significant food safety hazard in Kenya. To manage this risk, millers need to properly sample incoming bags of maize. In this study, three firms allowed researchers access to sample three incoming trucks each to quantify sources of variability using a hierarchical sampling design. A total of 180 samples consisting of two samples per bag, 10 bags per truck, three trucks per mill, and three mills were sampled in April of 2014 and analyzed for aflatoxins using the Romer-FluorQuant test method. Samples from three trucks were analyzed twice for aflatoxin to define intra-bag variability, and extracts were analyzed in duplicate to quantify analytical variability. The variance was partitioned as follows: mill (1.9%), truck (4.1%), bag (60.8%), in-bag (26.6%), analytical error (6.3%) and residual error (0.3%). Using these data, a power study was conducted to optimize the number of bags per truck that should be sampled. The power test, depicted using a power curve, indicated that 20 bags provided a statistical probability of 0.83. This study characterizes the sources of variability in sampling, and the inclusion of a power study highlights the tradeoffs in the number of bags sampled and the ability to detect small effects in estimating the level of aflatoxin contamination in maize.
Surface-enhanced Raman spectroscopy (SERS) was examined to explore the feasibility of SERS techni... more Surface-enhanced Raman spectroscopy (SERS) was examined to explore the feasibility of SERS technique to develop a rapid, non-destructive, and reliable spectroscopic method for qualitative and quantitative analysis of chlortetracycline (CTC) and oxytetracycline (OTC) in animal feed. Study samples were prepared by spiking tetracycline-free animal feed at different concentration ranges. In several Raman shift regions including characteristic peaks, spectral variation and Raman intensity difference among CTC and OTC groups at different concentrations were clearly visualized, depending on the type of tetracycline. The k-nearest neighbor (KNN) and linear discriminant analysis (LDA) models yielded excellent correct classification rates while showing no or only one misclassification of spiked samples as false-negative. The first two canonical variables in the chemometric modes for classification accounted for more than 95% variation in SERS spectra. Of the models developed for predicting CTC and OTC concentrations, multiple linear regression (MLR) and partial least squares regression (PLSR) models for CTC quantification showed outstanding model performance and ability, with coefficient of determination (r 2 ) (> 0.94), low predictive error rate (< 10.0 mg/kg), and acceptable linear regression slope (close to 1.0). The slightly lower predictive power and model performance were observed in MLR and PLSR models for OTC quantification. The findings and implications from this study indicate that SERS can be an alternative or supplementary analytical technique with acceptable sensitivity and accuracy to existing standard chemical methods for rapid determination of select tetracyclines in animal feeds, serving as an excellent screening system for real-time monitoring of tetracycline contaminated feed samples.
The surface-enhanced activities of size-and shape-controlled gold nanoparticles (AuNPs) with supe... more The surface-enhanced activities of size-and shape-controlled gold nanoparticles (AuNPs) with superior chemical stability were investigated to explore a possible development of a simple and non-destructive spectroscopic method to help the regulatory agency's analytical services for rapid detection and characterization of selected antimicrobials in animal feeds. Feed samples spiked at different concentration ranges of antimicrobials were evaluated using AuNPs as a surface-enhanced Raman spectroscopy (SERS) agent. The collected SERS spectra were mathematically preprocessed for further analysis. The classification models obtained 100% predictive accuracy with zero or little misclassification. The first two canonical variables (p = 0.001) could explain >95% of the variability in preprocessed spectral data. Most chemometric models for predicting MON, DEC, and LAS concentrations showed a high predictive accuracy (r 2 > 0.90), lower predictive error (<20 mg/kg), and satisfactory regression quality (slope close to 1.0). The statistical results showed no statistically significant difference between the reference and SERS predicted values (p > 0.05). The findings and implications from the study indicate that SERS would be a powerful and efficient technique possessing a great potential serving as an excellent monitoring and screening tool for antimicrobial contaminated samples in the on-site analysis.
Surface-enhanced Raman spectroscopy (SERS) has been widely investigated in many applications. How... more Surface-enhanced Raman spectroscopy (SERS) has been widely investigated in many applications. However, only little work has been done on using SERS for the detection of volatile organic compounds (VOCs), primarily due to the challenges associated with fabricating SERS substrates with sufficient hotspots for signal enhancement and with the surface interfacially compatible for the VOCs. This study investigated the phase transfer of Ag-nanospheres (AgNSs) from the aqueous phase to the non-aqueous phase by electrostatic interaction induced by cationic surfactants, and the feasibility of the transferred AgNSs as SERS substrates for the determination of methyl salicylate VOC. Results indicated that one of three cationic surfactants, tetraoctylammonium bromide (TOAB) dissolved in organic solvent showed successful phase transfer of the AgNSs confirmed by several characterization analyses. The complex formed by hydrophobic interaction between the transferred AgNSs and Tenax-TA adsorbent poly...
Five commercially available quantitative test kits were evaluated for their capability to measure... more Five commercially available quantitative test kits were evaluated for their capability to measure naturally contaminated maize samples at 59 µg/kg, 306 µg/kg, and 901 µg/kg aflatoxin levels. The aflatoxin contaminated maize samples, collected during the 2010 Texas corn harvest, were measured using high performance liquid chromatography (HPLC) following Association of Analytical Communities (AOAC) official method 2005.08. Five aflatoxin quantitative test kits approved for measuring aflatoxin contaminated maize containing <100 µg/kg by the United States Department of Agriculture (USDA) Grain Inspection Packers and Stockyard Administration (GIPSA) were evaluated by three analysts who analyzed seven 50 gram samples for each of the three sources of aflatoxin contaminated grain. The relative difference between the HPLC measurements and test kit results were analyzed using an analysis of variance. Significant two-way interactions were observed among the three explanatory variables inclu...
Salmonella has been recognized as a major and important foodborne pathogen for humans and animals... more Salmonella has been recognized as a major and important foodborne pathogen for humans and animals over more than a century, causing human foodborne illness as well as high medical and economical cost. Accordingly, the effort to develop efficient and reliable Salmonella detection methods continues. This paper reviews and describes the development and application of commercially available Salmonella detection methods. These are categorized into several groups based on the principle applied: conventional culture methods, immunology-based assays, nucleic acid-based assays, miniaturized biochemical assays, and biosensors. Conventional culture methods serve as the basis in food testing laboratories despite rather laborious and time-consuming protocols. Considerable progress in rapid methods using emerging technologies yield faster answers and higher throughput of samples. This paper also shows and analyzes Salmonella test results and summarizes the features and limitations of the studies involving Salmonella detection methods developed for emergency response, mainly by food emergency response laboratories participating during recent fiscal years. The emergency response laboratories utilize Salmonella detection methods possessing properties that include simplicity, versatility, high sensitivity, good specificity, and cost efficiency. Collaboration of the food emergency response laboratories in the development of these technologies is important essentially to compare for the purpose of continually improving Salmonella detection methods.
Maize kernel hardness and proximate constituents were evaluated by several methods. Proximate con... more Maize kernel hardness and proximate constituents were evaluated by several methods. Proximate constituents and hardness-associated properties were significantly correlated, and their correlation coefficients were improved when moisture, protein, and oil contents ...
The applicability of Raman spectroscopy combined with chemometrics using different preprocessed s... more The applicability of Raman spectroscopy combined with chemometrics using different preprocessed spectra data was examined to develop fast, low-cost, and non-destructive spectroscopic methods for classification and quantification of aflatoxin-contaminated maize samples within the aflatoxin concentration range of 0e1206 mg/kg. This technique will find useful application in evaluating large numbers (e.g. >2000) of samples from maize hybrid performance trials and breeding programs. The best discriminant models were obtained from the linear discriminant analysis (LDA). The LDA models on validation samples showed correct classification rates in the range of 94e100% and did not misclassify any aflatoxin contaminated samples as aflatoxin negative. Of the models for predicting aflatoxin concentration, the partial least squares regression (PLSR) models showed the best quality of regression (slopes of 0.939e0.990) and highest coefficient of determination (r 2 ¼ 0.941e0.957). The models provide limited applicability to quantify aflatoxin concentration below 20 mg/kg. No significant difference was observed between predicted values using Raman spectroscopy and reference values using highperformance liquid chromatography (HPLC) (p > 0.05), indicating the suitability of Raman spectroscopy to rapidly screen large numbers of maize samples for aflatoxin contamination.
A corroborative study was conducted on the maize quality properties of test weight, pycnometer de... more A corroborative study was conducted on the maize quality properties of test weight, pycnometer density, tangential abrasive dehulling device (TADD), time-to-grind on the Stenvert hardness tester (SHT), 100-kernel weight, kernel size distribution, and proximate composition as well as maize dry-and wet-millability by six participating laboratories. Suggested operating procedures were given to compare their measurements and provide the variance structure within and between laboratories and hybrids. Partial correlation coefficient among maize quality properties varied among laboratories. The repeatability and reproducibility precision values were acceptably low for the physical quality tests, except for TADD and SHT time-to-grind measurements. The yields of dry-and wet-milled products and their correlation with maize quality properties were dependent on the collaborating laboratory. This paper highlights the importance of laboratory variation when considering which maize hybrids are best suited for dry-milling and wet-milling.
Two-dimensional Data Matrix (DM) barcode printed on a food-grade tracer to carry simulated identi... more Two-dimensional Data Matrix (DM) barcode printed on a food-grade tracer to carry simulated identifying information about grain in a prospective grain traceability system was evaluated for its ruggedness on different formulations, coating materials, and order of coating and printing. The key factor in evaluating the tracers was their ability to be read with a code scanner after being removed from a batch of grain at any point in the grain supply chain. After printing, the tracers were measured for initial readability, subjected to ruggedness tests involving abrasion and impact and the effect of moisture conditioning, and measured for final readability. Fourteen treatments involving two tracer types (sugar-based and cellulose-based), two coating materials (edible shellac and hydroxypropyl methylcellulose, or HPMC), and four coateprint procedures were considered. One particular treatment performed very well, whereas most others did not, having either low initial readability rates or low final readability rates after they were subjected to ruggedness testing. The treatment of interest consisted of cellulose-based tracers, printed in DM code with food-grade ink, and coated with HPMC after printing. Initial readability of this treatment averaged 98%, and final readability after ruggedness testing ranged from 89 to 99%, depending on the ruggedness test applied. These readability rates are considered acceptable for intended application. Since barcode printing on information-carrying tracers was an essential part of requirements for implementing the proposed grain traceability system, most major tracing system and technological components are now available in prototype form for the next phase of research and development for practical application of the system in the grain supply chain.
Small, coded, pill sized tracers embedded in grains are proposed as a method to store a historica... more Small, coded, pill sized tracers embedded in grains are proposed as a method to store a historical record of grains and retrieve coded information for grain traceability. This study aimed to develop and validate a statistical sampling procedure to securely collect sample sizes (kg) and number of tracers since the sampling accuracy is critical in the proposed traceability system for capturing information and data related to grain lots to trace the grain back through the route in a grain supply chain. The statistical results and observations showed similar concentrations and insignificant segregation of tracers in bin and truck operations. The number of tracers required for identification of grain sources fell within the confidence intervals and sample sizes (kg) estimated by statistical probability methods. Truck sampling appeared more feasible in collecting the secure number of tracers over bin sampling. The designed sampling process was empirically proven to be practically applicable and provide better scientific assurance of sampling accuracy, which may reduce economic risks and their consequent costs caused by unfavorable sampling in the propose traceability system.
Abstract Two hard white wheats (Triticum aestivum L.),&#x27;Betty&#x27;with high protein ... more Abstract Two hard white wheats (Triticum aestivum L.),&#x27;Betty&#x27;with high protein and good processing quality and &#x27;Trego&#x27;with good yield potential, were blended at percentages of 0, 10, 30, 50, 70, 90, and 100% Betty and planted at three locations in western Kansas ...
Cereal Chem. 84(2):152-161 A genetically and environmentally diverse collection of maize (Zea mai... more Cereal Chem. 84(2):152-161 A genetically and environmentally diverse collection of maize (Zea maize L.) samples was evaluated for physical properties and grit yield to help develop a standard set of criteria to identify grain best suited for drymilling. Application of principal component analysis (PCA) reduced a set of approximately 500 samples collected from six states to 154 maize hybrids. Selected maize hybrids were placed into seven groups according to their dry-milled grit yields. Regression analysis explained only 50% of the variability in dry-milling grit yield. Patterns of differences in the physical properties for the seven grit yield groups implied that the seven yield groups could be placed into two or three groups. Using two pattern recognition techniques for improving classification accuracy, quadratic discriminant analysis and the classification and regression tree (CART) model, dry-milled grit yield groups were predicted. The estimated correct classification rates were 69-80% when the samples were divided into three yield groups and 81-90% when samples were divided into two yield groups. The results indicated the comparable success of both techniques and the superiority of the decision tree algorithm to quadratic discriminant analysis by offering higher accuracy and clearer classification rules in differentiating among dry-milled grit yield groups. Corn dry-milling separates maize kernels into three main components (endosperm, germ, and pericarp), producing numerous product streams for use in food, animal feeds, and industrial products (Duensing et al 2003). Corn grits, meals, and flour are the primary products obtained from the endosperm. Of these, higher recovery of larger grits is desirable for dry-millers because of the greater economic value. Dry-milled products are different in proximate composition and physical properties (Duensing et al 2003). Previous research indicates that dry-milling yield determinants include maize genetics, bulk and kernel density, hardness, breakage susceptibility, protein content, drying temperature, weather, postharvest conditions, and other influencing factors (Kirleis and Stroshine 1990; Wu and Bergquist 1991; Peplinski et al 1992; Duensing et al 2003). Maize producers and corn dry-millers often use unofficial grades and tests to predict maize hybrid end-use processing performance because maize hybrids ranked with higher official grade do not always guarantee better suitability for the customers' use (Paulsen et al 2003). This means that in certain cases the intended end-use performance of maize determines the traits and tests that are important for the evaluation of maize quality. The early segregation of maize using quality-associated properties will increase its economic value. Little standardization exists among such unofficial physical kernel tests, analytical techniques, and "reference" processing methods. For example, the strength of various relationships (correlations) between hardness measurements and end-use processing performance reported in scientific literature varies tremendously (
Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of com... more Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of commonly grown hybrids and diverse physical attributes were analyzed for alkaline cooking performance. The influence of kernel characteristics including hardness, density, starch properties (thermal, pasting, and crystallinity), starch content, protein content, and prolamin content on alkaline cooking performance was also determined. Corn nixtamal moisture content was lower for hard, dense kernels with high protein contents; sorghum nixtamal moisture content was lower for kernels with low moisture contents and low starch relative crystallinities. Statistically significant (P < 0.05) regression equations showed that corn nixtamal moisture content was influenced by TADD (tangential abrasive dehulling device) index, kernel moisture content, starch content, and protein content; sorghum nixtamal moisture content was influenced by starch relative crystallinity, kernel moisture content, and abrasive hardness index. Pericarp removal was not strongly correlated with kernel characterization tests. Location (environmental) and hybrid (genetic) factors influenced most kernel characteristics and nixtamalization processing variables.
Aflatoxin is a group I carcinogen and represents a significant public health and food safety risk... more Aflatoxin is a group I carcinogen and represents a significant public health and food safety risk throughout the world. Aflatoxin contaminated cereals and oilseeds that contain greater than 20 μg/kg of the toxin (B1, B2, G1, G2) are defined as adulterated by the Texas Commercial Feed Rules and are regulated by the Texas Feed and Fertilizer Control Service. This study was performed to assess sampling and testing of maize for aflatoxin contamination. During 2010, 87 Texas grain elevators’ samples with respect to their sampling procedures were assessed and a second investigation documented aflatoxin analysis procedures at 41 grain elevator establishments. The average sample size was 1.8 kg (4 pounds) and fewer than 20% of the grain elevators collected samples using an official (prescribed) sampling pattern by the grain inspection, crop insurance or regulatory authorities within the United States. Proficiency materials were analyzed by 39 cooperating grain elevators and 7 firms accurate...
We developed a novel substrate for the collection of volatile organic compounds (VOCs) emitted fr... more We developed a novel substrate for the collection of volatile organic compounds (VOCs) emitted from either living or dried plant material to be analyzed by surface-enhanced Raman spectroscopy (SERS). We demonstrated that this substrate can be utilized to differentiate emissions from blends of three teas, and to differentiate emissions from healthy cotton plants versus caterpillar-infested cotton plants. The substrate we developed can adsorb VOCs in static headspace sampling environments, and VOCs naturally evaporated from three standards were successfully identified by our SERS substrate, showing its ability to differentiate three VOCs and to detect quantitative differences according to collection times. In addition, volatile profiles from plant materials that were either qualitatively different among three teas or quantitatively different in abundance between healthy and infested cotton plants were confirmed by collections on Super-Q resin for dynamic headspace and solid-phase microextraction for static headspace sampling, respectively, followed by gas chromatography to mass spectrometry. Our results indicate that both qualitative and quantitative differences can also be detected by our SERS substrate although we find that the detection of quantitative differences could be improved.
This study evaluated distillers grain (DG) by-products produced in different ethanol plants and s... more This study evaluated distillers grain (DG) by-products produced in different ethanol plants and supplemented in animal diets in Texas, based on samples analyzed from 2008 to 2014. The samples were assessed for concentration, occurrence, and prevalence of selected nutrients and contaminants. Protein and sulfur contents of DG were largely different between corn and sorghum by-products as well as wet distillers grain with solubles and dry distillers grain with solubles (DDGS), indicating a significant effect of grain feedstock and dry-grind process stream on DG composition and quality. Salmonella was isolated in 4 DDGS samples out of a total of 157 DG samples, a percentage (2.5%) that is much lower than the percentage of Salmonella-positive samples found in other feed samples analyzed during the same period. A small amount of virginiamycin residue was found in 24 corn DDGS, 1 corn wet distillers grain with solubles, and 2 sorghum DDGS samples out of 242 samples in total. One sorghum DD...
Salmonella species (spp.) are zoonotic pathogens that contaminate animal ingredients and finished... more Salmonella species (spp.) are zoonotic pathogens that contaminate animal ingredients and finished feed and represent a significant human food safety hazard as identified by the Codex Animal Feed Taskforce. The United States (US) Food and Drug Administration (FDA) has promulgated regulations prohibiting Salmonella contamination in feed and has published a guidance document expressing their current strategy involving regulatory oversight of Salmonella contamination in feed. The Office of the Texas State Chemist (OTSC) initiated the broad surveillance of Salmonella spp. in 2007, in response to a Salmonella enterica serotype Typhimurium outbreak in frozen rodents, which are subject to the agency’s regulatory oversight as defined by the Texas Commercial Feed Control Act. From calendar years of 2007-2011, 2622 total feed samples were collected and subsequently evaluated for Salmonella contamination using multiple screening methods, including polymerase chain reaction (PCR) and automated i...
In this work, novel ultrathin electrospun fibers from different blends of amaranth protein 17 iso... more In this work, novel ultrathin electrospun fibers from different blends of amaranth protein 17 isolate (API) and the carbohydrate polymer pullulan, with or without the surfactant 18 Tween80, have been developed and characterized. The solution properties and molecular 19 organization of the electrospun structures were studied and correlated with the morphology 20 of the obtained fibers. The presence of pullulan in the blends resulted in increased viscosity 21 and lower conductivity of the solutions, related to a better chain entanglement and decrease 22 in the polyelectrolyte protein character, respectively, both factors needed for fiber 23 formation. Infrared spectral changes indicated that defect-free fibers were correlated with 24 extended α-helical protein structures, which for the blends with greater protein contents, 25 was only obtained upon surfactant addition. The thermal stability of the hybrid fibers was 26 better than that of pure API and slightly increased upon surfactant addition, while the water 27 stability of the blends was highly dependent on fiber composition. These structures have a 28 great potential for the encapsulation of bioactives for functional food applications.
The spectroscopic method based on surface-enhanced Raman spectroscopy (SERS) technique combined w... more The spectroscopic method based on surface-enhanced Raman spectroscopy (SERS) technique combined with chemometric methods was developed for simple, cost-effective, and efficient analysis of chlorpyrifos (CPF) and aldicarb (ALD) pesticide residues in animal feed. Animal feeds free from the pesticides were spiked at different concentrations of CPF (0-20 mg/kg) and aldicarb (0-100 µg/kg). Gold nanoparticles were mixed with sample extract for SERS measurement. A significant spectral difference induced by the presence and different level of CPF and ALD concentration in animal feed was observed between the pesticide spiking groups. Different chemometric models applied on training datasets showed excellent classification rates (100 percent) while the models on external validation dataset exhibited lower correct classification rates (50.0-76.7 percent) with no false-negative error. The selected chemometric models for CPF and ALD quantification also showed a high predictive ability and performance. The developed models displayed no statistical significant difference between model predicted and reference values in the external validation dataset (p < 0.01). The study results indicate that the SERS spectroscopic method could be an effective and efficient analytical tool for pesticide analysis in highly complex animal feed matrices for screening at a point of sampling to improve food and feed safety.
Aflatoxin contamination in maize represents a significant food safety hazard in Kenya. To manage ... more Aflatoxin contamination in maize represents a significant food safety hazard in Kenya. To manage this risk, millers need to properly sample incoming bags of maize. In this study, three firms allowed researchers access to sample three incoming trucks each to quantify sources of variability using a hierarchical sampling design. A total of 180 samples consisting of two samples per bag, 10 bags per truck, three trucks per mill, and three mills were sampled in April of 2014 and analyzed for aflatoxins using the Romer-FluorQuant test method. Samples from three trucks were analyzed twice for aflatoxin to define intra-bag variability, and extracts were analyzed in duplicate to quantify analytical variability. The variance was partitioned as follows: mill (1.9%), truck (4.1%), bag (60.8%), in-bag (26.6%), analytical error (6.3%) and residual error (0.3%). Using these data, a power study was conducted to optimize the number of bags per truck that should be sampled. The power test, depicted using a power curve, indicated that 20 bags provided a statistical probability of 0.83. This study characterizes the sources of variability in sampling, and the inclusion of a power study highlights the tradeoffs in the number of bags sampled and the ability to detect small effects in estimating the level of aflatoxin contamination in maize.
Surface-enhanced Raman spectroscopy (SERS) was examined to explore the feasibility of SERS techni... more Surface-enhanced Raman spectroscopy (SERS) was examined to explore the feasibility of SERS technique to develop a rapid, non-destructive, and reliable spectroscopic method for qualitative and quantitative analysis of chlortetracycline (CTC) and oxytetracycline (OTC) in animal feed. Study samples were prepared by spiking tetracycline-free animal feed at different concentration ranges. In several Raman shift regions including characteristic peaks, spectral variation and Raman intensity difference among CTC and OTC groups at different concentrations were clearly visualized, depending on the type of tetracycline. The k-nearest neighbor (KNN) and linear discriminant analysis (LDA) models yielded excellent correct classification rates while showing no or only one misclassification of spiked samples as false-negative. The first two canonical variables in the chemometric modes for classification accounted for more than 95% variation in SERS spectra. Of the models developed for predicting CTC and OTC concentrations, multiple linear regression (MLR) and partial least squares regression (PLSR) models for CTC quantification showed outstanding model performance and ability, with coefficient of determination (r 2 ) (> 0.94), low predictive error rate (< 10.0 mg/kg), and acceptable linear regression slope (close to 1.0). The slightly lower predictive power and model performance were observed in MLR and PLSR models for OTC quantification. The findings and implications from this study indicate that SERS can be an alternative or supplementary analytical technique with acceptable sensitivity and accuracy to existing standard chemical methods for rapid determination of select tetracyclines in animal feeds, serving as an excellent screening system for real-time monitoring of tetracycline contaminated feed samples.
The surface-enhanced activities of size-and shape-controlled gold nanoparticles (AuNPs) with supe... more The surface-enhanced activities of size-and shape-controlled gold nanoparticles (AuNPs) with superior chemical stability were investigated to explore a possible development of a simple and non-destructive spectroscopic method to help the regulatory agency's analytical services for rapid detection and characterization of selected antimicrobials in animal feeds. Feed samples spiked at different concentration ranges of antimicrobials were evaluated using AuNPs as a surface-enhanced Raman spectroscopy (SERS) agent. The collected SERS spectra were mathematically preprocessed for further analysis. The classification models obtained 100% predictive accuracy with zero or little misclassification. The first two canonical variables (p = 0.001) could explain >95% of the variability in preprocessed spectral data. Most chemometric models for predicting MON, DEC, and LAS concentrations showed a high predictive accuracy (r 2 > 0.90), lower predictive error (<20 mg/kg), and satisfactory regression quality (slope close to 1.0). The statistical results showed no statistically significant difference between the reference and SERS predicted values (p > 0.05). The findings and implications from the study indicate that SERS would be a powerful and efficient technique possessing a great potential serving as an excellent monitoring and screening tool for antimicrobial contaminated samples in the on-site analysis.
Surface-enhanced Raman spectroscopy (SERS) has been widely investigated in many applications. How... more Surface-enhanced Raman spectroscopy (SERS) has been widely investigated in many applications. However, only little work has been done on using SERS for the detection of volatile organic compounds (VOCs), primarily due to the challenges associated with fabricating SERS substrates with sufficient hotspots for signal enhancement and with the surface interfacially compatible for the VOCs. This study investigated the phase transfer of Ag-nanospheres (AgNSs) from the aqueous phase to the non-aqueous phase by electrostatic interaction induced by cationic surfactants, and the feasibility of the transferred AgNSs as SERS substrates for the determination of methyl salicylate VOC. Results indicated that one of three cationic surfactants, tetraoctylammonium bromide (TOAB) dissolved in organic solvent showed successful phase transfer of the AgNSs confirmed by several characterization analyses. The complex formed by hydrophobic interaction between the transferred AgNSs and Tenax-TA adsorbent poly...
Five commercially available quantitative test kits were evaluated for their capability to measure... more Five commercially available quantitative test kits were evaluated for their capability to measure naturally contaminated maize samples at 59 µg/kg, 306 µg/kg, and 901 µg/kg aflatoxin levels. The aflatoxin contaminated maize samples, collected during the 2010 Texas corn harvest, were measured using high performance liquid chromatography (HPLC) following Association of Analytical Communities (AOAC) official method 2005.08. Five aflatoxin quantitative test kits approved for measuring aflatoxin contaminated maize containing <100 µg/kg by the United States Department of Agriculture (USDA) Grain Inspection Packers and Stockyard Administration (GIPSA) were evaluated by three analysts who analyzed seven 50 gram samples for each of the three sources of aflatoxin contaminated grain. The relative difference between the HPLC measurements and test kit results were analyzed using an analysis of variance. Significant two-way interactions were observed among the three explanatory variables inclu...
Salmonella has been recognized as a major and important foodborne pathogen for humans and animals... more Salmonella has been recognized as a major and important foodborne pathogen for humans and animals over more than a century, causing human foodborne illness as well as high medical and economical cost. Accordingly, the effort to develop efficient and reliable Salmonella detection methods continues. This paper reviews and describes the development and application of commercially available Salmonella detection methods. These are categorized into several groups based on the principle applied: conventional culture methods, immunology-based assays, nucleic acid-based assays, miniaturized biochemical assays, and biosensors. Conventional culture methods serve as the basis in food testing laboratories despite rather laborious and time-consuming protocols. Considerable progress in rapid methods using emerging technologies yield faster answers and higher throughput of samples. This paper also shows and analyzes Salmonella test results and summarizes the features and limitations of the studies involving Salmonella detection methods developed for emergency response, mainly by food emergency response laboratories participating during recent fiscal years. The emergency response laboratories utilize Salmonella detection methods possessing properties that include simplicity, versatility, high sensitivity, good specificity, and cost efficiency. Collaboration of the food emergency response laboratories in the development of these technologies is important essentially to compare for the purpose of continually improving Salmonella detection methods.
Maize kernel hardness and proximate constituents were evaluated by several methods. Proximate con... more Maize kernel hardness and proximate constituents were evaluated by several methods. Proximate constituents and hardness-associated properties were significantly correlated, and their correlation coefficients were improved when moisture, protein, and oil contents ...
The applicability of Raman spectroscopy combined with chemometrics using different preprocessed s... more The applicability of Raman spectroscopy combined with chemometrics using different preprocessed spectra data was examined to develop fast, low-cost, and non-destructive spectroscopic methods for classification and quantification of aflatoxin-contaminated maize samples within the aflatoxin concentration range of 0e1206 mg/kg. This technique will find useful application in evaluating large numbers (e.g. >2000) of samples from maize hybrid performance trials and breeding programs. The best discriminant models were obtained from the linear discriminant analysis (LDA). The LDA models on validation samples showed correct classification rates in the range of 94e100% and did not misclassify any aflatoxin contaminated samples as aflatoxin negative. Of the models for predicting aflatoxin concentration, the partial least squares regression (PLSR) models showed the best quality of regression (slopes of 0.939e0.990) and highest coefficient of determination (r 2 ¼ 0.941e0.957). The models provide limited applicability to quantify aflatoxin concentration below 20 mg/kg. No significant difference was observed between predicted values using Raman spectroscopy and reference values using highperformance liquid chromatography (HPLC) (p > 0.05), indicating the suitability of Raman spectroscopy to rapidly screen large numbers of maize samples for aflatoxin contamination.
A corroborative study was conducted on the maize quality properties of test weight, pycnometer de... more A corroborative study was conducted on the maize quality properties of test weight, pycnometer density, tangential abrasive dehulling device (TADD), time-to-grind on the Stenvert hardness tester (SHT), 100-kernel weight, kernel size distribution, and proximate composition as well as maize dry-and wet-millability by six participating laboratories. Suggested operating procedures were given to compare their measurements and provide the variance structure within and between laboratories and hybrids. Partial correlation coefficient among maize quality properties varied among laboratories. The repeatability and reproducibility precision values were acceptably low for the physical quality tests, except for TADD and SHT time-to-grind measurements. The yields of dry-and wet-milled products and their correlation with maize quality properties were dependent on the collaborating laboratory. This paper highlights the importance of laboratory variation when considering which maize hybrids are best suited for dry-milling and wet-milling.
Two-dimensional Data Matrix (DM) barcode printed on a food-grade tracer to carry simulated identi... more Two-dimensional Data Matrix (DM) barcode printed on a food-grade tracer to carry simulated identifying information about grain in a prospective grain traceability system was evaluated for its ruggedness on different formulations, coating materials, and order of coating and printing. The key factor in evaluating the tracers was their ability to be read with a code scanner after being removed from a batch of grain at any point in the grain supply chain. After printing, the tracers were measured for initial readability, subjected to ruggedness tests involving abrasion and impact and the effect of moisture conditioning, and measured for final readability. Fourteen treatments involving two tracer types (sugar-based and cellulose-based), two coating materials (edible shellac and hydroxypropyl methylcellulose, or HPMC), and four coateprint procedures were considered. One particular treatment performed very well, whereas most others did not, having either low initial readability rates or low final readability rates after they were subjected to ruggedness testing. The treatment of interest consisted of cellulose-based tracers, printed in DM code with food-grade ink, and coated with HPMC after printing. Initial readability of this treatment averaged 98%, and final readability after ruggedness testing ranged from 89 to 99%, depending on the ruggedness test applied. These readability rates are considered acceptable for intended application. Since barcode printing on information-carrying tracers was an essential part of requirements for implementing the proposed grain traceability system, most major tracing system and technological components are now available in prototype form for the next phase of research and development for practical application of the system in the grain supply chain.
Small, coded, pill sized tracers embedded in grains are proposed as a method to store a historica... more Small, coded, pill sized tracers embedded in grains are proposed as a method to store a historical record of grains and retrieve coded information for grain traceability. This study aimed to develop and validate a statistical sampling procedure to securely collect sample sizes (kg) and number of tracers since the sampling accuracy is critical in the proposed traceability system for capturing information and data related to grain lots to trace the grain back through the route in a grain supply chain. The statistical results and observations showed similar concentrations and insignificant segregation of tracers in bin and truck operations. The number of tracers required for identification of grain sources fell within the confidence intervals and sample sizes (kg) estimated by statistical probability methods. Truck sampling appeared more feasible in collecting the secure number of tracers over bin sampling. The designed sampling process was empirically proven to be practically applicable and provide better scientific assurance of sampling accuracy, which may reduce economic risks and their consequent costs caused by unfavorable sampling in the propose traceability system.
Abstract Two hard white wheats (Triticum aestivum L.),&#x27;Betty&#x27;with high protein ... more Abstract Two hard white wheats (Triticum aestivum L.),&#x27;Betty&#x27;with high protein and good processing quality and &#x27;Trego&#x27;with good yield potential, were blended at percentages of 0, 10, 30, 50, 70, 90, and 100% Betty and planted at three locations in western Kansas ...
Cereal Chem. 84(2):152-161 A genetically and environmentally diverse collection of maize (Zea mai... more Cereal Chem. 84(2):152-161 A genetically and environmentally diverse collection of maize (Zea maize L.) samples was evaluated for physical properties and grit yield to help develop a standard set of criteria to identify grain best suited for drymilling. Application of principal component analysis (PCA) reduced a set of approximately 500 samples collected from six states to 154 maize hybrids. Selected maize hybrids were placed into seven groups according to their dry-milled grit yields. Regression analysis explained only 50% of the variability in dry-milling grit yield. Patterns of differences in the physical properties for the seven grit yield groups implied that the seven yield groups could be placed into two or three groups. Using two pattern recognition techniques for improving classification accuracy, quadratic discriminant analysis and the classification and regression tree (CART) model, dry-milled grit yield groups were predicted. The estimated correct classification rates were 69-80% when the samples were divided into three yield groups and 81-90% when samples were divided into two yield groups. The results indicated the comparable success of both techniques and the superiority of the decision tree algorithm to quadratic discriminant analysis by offering higher accuracy and clearer classification rules in differentiating among dry-milled grit yield groups. Corn dry-milling separates maize kernels into three main components (endosperm, germ, and pericarp), producing numerous product streams for use in food, animal feeds, and industrial products (Duensing et al 2003). Corn grits, meals, and flour are the primary products obtained from the endosperm. Of these, higher recovery of larger grits is desirable for dry-millers because of the greater economic value. Dry-milled products are different in proximate composition and physical properties (Duensing et al 2003). Previous research indicates that dry-milling yield determinants include maize genetics, bulk and kernel density, hardness, breakage susceptibility, protein content, drying temperature, weather, postharvest conditions, and other influencing factors (Kirleis and Stroshine 1990; Wu and Bergquist 1991; Peplinski et al 1992; Duensing et al 2003). Maize producers and corn dry-millers often use unofficial grades and tests to predict maize hybrid end-use processing performance because maize hybrids ranked with higher official grade do not always guarantee better suitability for the customers' use (Paulsen et al 2003). This means that in certain cases the intended end-use performance of maize determines the traits and tests that are important for the evaluation of maize quality. The early segregation of maize using quality-associated properties will increase its economic value. Little standardization exists among such unofficial physical kernel tests, analytical techniques, and "reference" processing methods. For example, the strength of various relationships (correlations) between hardness measurements and end-use processing performance reported in scientific literature varies tremendously (
Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of com... more Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of commonly grown hybrids and diverse physical attributes were analyzed for alkaline cooking performance. The influence of kernel characteristics including hardness, density, starch properties (thermal, pasting, and crystallinity), starch content, protein content, and prolamin content on alkaline cooking performance was also determined. Corn nixtamal moisture content was lower for hard, dense kernels with high protein contents; sorghum nixtamal moisture content was lower for kernels with low moisture contents and low starch relative crystallinities. Statistically significant (P < 0.05) regression equations showed that corn nixtamal moisture content was influenced by TADD (tangential abrasive dehulling device) index, kernel moisture content, starch content, and protein content; sorghum nixtamal moisture content was influenced by starch relative crystallinity, kernel moisture content, and abrasive hardness index. Pericarp removal was not strongly correlated with kernel characterization tests. Location (environmental) and hybrid (genetic) factors influenced most kernel characteristics and nixtamalization processing variables.
Aflatoxin is a group I carcinogen and represents a significant public health and food safety risk... more Aflatoxin is a group I carcinogen and represents a significant public health and food safety risk throughout the world. Aflatoxin contaminated cereals and oilseeds that contain greater than 20 μg/kg of the toxin (B1, B2, G1, G2) are defined as adulterated by the Texas Commercial Feed Rules and are regulated by the Texas Feed and Fertilizer Control Service. This study was performed to assess sampling and testing of maize for aflatoxin contamination. During 2010, 87 Texas grain elevators’ samples with respect to their sampling procedures were assessed and a second investigation documented aflatoxin analysis procedures at 41 grain elevator establishments. The average sample size was 1.8 kg (4 pounds) and fewer than 20% of the grain elevators collected samples using an official (prescribed) sampling pattern by the grain inspection, crop insurance or regulatory authorities within the United States. Proficiency materials were analyzed by 39 cooperating grain elevators and 7 firms accurate...
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Papers by Kyung-Min Lee