Hoonsoo Lee

Detection and quantification of adulterants in milk powder using a high-throughput Raman chemical imaging technique

ABSTRACT Milk is a vulnerable target for economically motivated adulteration. In this study, a line-scan high-throughput Raman imaging system was used to authenticate milk powder. A 5 W 785 nm line laser (240 mm long and 1 mm wide) was used as a Raman excitation source. The system was used to acquire hyperspectral Raman images in a wave number range of 103–2881 cm–1 from the skimmed milk powder mixed with two nitrogen-rich adulterants (i.e., melamine and urea) at eight concentrations (w/w) from 50 to 10,000 ppm. The powdered samples were put in sample holders with a surface area of 150 ×100 mm and a depth of 2 mm for push-broom image acquisition. Varying fluorescence signals from the milk powder were removed using a correction method based on adaptive iteratively reweighted penalised least squares. Image classifications were conducted using a simple thresholding method applied to single-band fluorescence-corrected images at unique Raman peaks selected for melamine (673 cm–1) and urea (1009 cm–1). Chemical images were generated by combining individual binary images of melamine and urea to visualise identification, spatial distribution and morphological features of the two adulterant particles in the milk powder. Limits of detection for both melamine and urea were estimated in the order of 50 ppm. High correlations were found between pixel concentrations (i.e., percentages of the adulterant pixels in the chemical images) and mass concentrations of melamine and urea, demonstrating the potential of the high-throughput Raman chemical imaging method for the detection and quantification of adulterants in the milk powder. GRAPHICAL ABSTRACT

Quantitative analysis of Sudan dye adulteration in paprika powder using FTIR spectroscopy

ABSTRACT As adulteration of foodstuffs with Sudan dye, especially paprika- and chilli-containing products, has been reported with some frequency, this issue has become one focal point for addressing food safety. FTIR spectroscopy has been used extensively as an analytical method for quality control and safety determination for food products. Thus, the use of FTIR spectroscopy for rapid determination of Sudan dye in paprika powder was investigated in this study. A net analyte signal (NAS)-based methodology, named HLA/GO (hybrid linear analysis in the literature), was applied to FTIR spectral data to predict Sudan dye concentration. The calibration and validation sets were designed to evaluate the performance of the multivariate method. The obtained results had a high determination coefficient (R2) of 0.98 and low root mean square error (RMSE) of 0.026% for the calibration set, and an R2 of 0.97 and RMSE of 0.05% for the validation set. The model was further validated using a second validation set and through the figures of merit, such as sensitivity, selectivity, and limits of detection and quantification. The proposed technique of FTIR combined with HLA/GO is rapid, simple and low cost, making this approach advantageous when compared with the main alternative methods based on liquid chromatography (LC) techniques. GRAPHICAL ABSTRACT

Non‐destructive technique for determining the viability of soybean (Glycine max) seeds using FT‐NIR spectroscopy

BACKGROUND The viability of seeds is important for determining their quality. A high-quality seed is one that has a high capability of germination that is necessary to ensure high productivity. Hence, developing technology for the detection of seed viability is a high priority in agriculture. Fourier transform near-infrared (FT-NIR) spectroscopy is one of the most popular devices among other vibrational spectroscopies. This study aims to use FT-NIR spectroscopy to determine the viability of soybean seeds. RESULTS Viable and artificial ageing seeds as non-viable soybeans were used in this research. The FT-NIR spectra of soybean seeds were collected and analysed using a partial least-squares discriminant analysis (PLS-DA) to classify viable and non-viable soybean seeds. Moreover, the variable importance in projection (VIP) method for variable selection combined with the PLS-DA was employed. The most effective wavelengths were selected by the VIP method, which selected 146 optimal variables from the full set of 1557 variables. CONCLUSIONS The results demonstrated that the FT-NIR spectral analysis with the PLS-DA method that uses all variables or the selected variables showed good performance based on the high value of prediction accuracy for soybean viability with an accuracy close to 100%. Hence, FT-NIR techniques with a chemometric analysis have the potential for rapidly measuring soybean seed viability.

MCT-based shortwave infrared hyperspectral imaging system for the detection and quantification of adulterants in powder samples (Conference Presentation)

Although many studies have been conducted to detect melamine in milk powder using near-infrared hyperspectral imaging system, the reproducibility due to moisture content in powder sample and detection limit have not been addressed appropriately. The objective of this study is to develop, based on shortwave infrared (SWIR) hyperspectral imaging, optimal model which is less sensitive to change of moisture content in sample powder. The hyperspectral imaging system consists of a MCT-based camera capable of measuring wavelengths from 1000nm to 2500nm. A halogen-based light source module was used to illuminated samples. The results showed a mixture concentration as low as 50 ppm of melamine in milk could be detected. The detection accuracy using the wavelength region from 1700nm to 2500nm was higher than that of using the wavelength from 1000nm to 1700nm. The MCT-based SWIR hyperspectral imaging system has a good potential for the detection and quantification of adulterants in powder sample.

Determination of total volatile basic nitrogen (TVB-N) content in pork meat using hyperspectral imaging technique (Conference Presentation)

Total volatile basic nitrogen (TVB-N) content is one of the important factors to measure the quality of meat. However, conventional chemical analysis methods for measuring TVB-N contents are time-consuming and labor-intensive, and are destructive procedures. The objective of this study is to investigate the possibility of fluorescence hyperspectral imaging techniques for determination of total volatile basic nitrogen (TVB-N) in beef meat. High intensity LED lights at 365 nm and 405 nm were used as the excitation for acquiring fluorescence images. Prediction algorithms based on simple band-ratio, partial least square discriminant analysis (PLS-DA) have been developed. This study shows that fluorescence hyperspectral imaging system has a good potential for rapid measurement of TVB-N content in meat.

Analysis of pork and poultry meat and bone meal mixture using hyperspectral imaging

Meat and bone meal (MBM) has been banned as animal feed for ruminants since 2001 because it is the source of bovine spongiform encephalopathy (BSE). Moreover, many countries have banned the use of MBM as animal feed for not only ruminants but other farm animals as well, to prevent potential outbreak of BSE. Recently, the EU has introduced use of some MBM in feeds for different animal species, such as poultry MBM for swine feed and pork MBM for poultry feed, for economic reasons. In order to authenticate the MBM species origin, species-specific MBM identification methods are needed. Various spectroscopic and spectral imaging techniques have allowed rapid and non-destructive quality assessments of foods and animal feeds. The objective of this study was to develop rapid and accurate methods to differentiate pork MBM from poultry MBM using short-wave infrared (SWIR) hyperspectral imaging techniques. Results from a preliminary investigation of hyperspectral imaging for assessing pork and poultry MBM characteristics and quantitative analysis of poultry-pork MBM mixtures are presented in this paper.

Rapid detection of parasite in muscle fibers of fishes using a portable microscope imaging technique (Conference Presentation)

Fishes are a widely used food material in the world. Recently about 4% of the fishes are infected with Kudoa thyrsites in Asian ocean. Kudoa thyrsites is a parasite that is found within the muscle fibers of fishes. The infected fishes can be a reason of food poisoning, which should be sorted out before distribution and consumption. Although Kudoa thyrsites is visible to the naked eye, it could be easily overlooked due to the micro-scale size and similar color with fish tissue. In addition, the visual inspection is labor intensive works resulting in loss of money and time. In this study, a portable microscopic camera was utilized to obtain images of raw fish slices. The optimized image processing techniques with polarized transmittance images provided reliable performance. The result shows that the portable microscopic imaging method can be used to detect parasites rapidly and non-destructively, which could be an alternative to manual inspections.

Characterization of E coli biofim formations on baby spinach leaf surfaces using hyperspectral fluorescence imaging

Bacterial biofilm formed by pathogens on fresh produce surfaces is a food safety concern because the complex extracellular matrix in the biofilm structure reduces the reduction and removal efficacies of washing and sanitizing processes such as chemical or irradiation treatments. Therefore, a rapid and nondestructive method to identify pathogenic biofilm on produce surfaces is needed to ensure safe consumption of fresh, raw produce. This research aimed to evaluate the feasibility of hyperspectral fluorescence imaging for detecting Escherichia.coli (ATCC 25922) biofilms on baby spinach leaf surfaces. Samples of baby spinach leaves were immersed and inoculated with five different levels (from 2.6x104 to 2.6x108 CFU/mL) of E.coli and stored at 4°C for 24 h and 48 h to induce biofilm formation. Following the two treatment days, individual leaves were gently washed to remove excess liquid inoculums from the leaf surfaces and imaged with a hyperspectral fluorescence imaging system equipped with UV-A (365 nm) and violet (405 nm) excitation sources to evaluate a spectral-image-based method for biofilm detection. The imaging results with the UV-A excitation showed that leaves even at early stages of biofilm formations could be differentiated from the control leaf surfaces. This preliminary investigation demonstrated the potential of fluorescence imaging techniques for detection of biofilms on leafy green surfaces.

Machine Vision Technique for Rapid Measurement of Soybean Seed Vigor

Improving crop yield and production stability is important in satisfying the rising demand of human consumption due to the current increasing world population and rapid economic growth of developing countries. Seed quality is one of the most important factors in crop production and should be considered at the first stage of crop cultivation. Germination testing, which is defined by the International Seed Testing Association (ISTA), is one of the primary means of evaluating seed quality and reflects a seed’s ability to produce normal seedlings. A germination test is a common method of determining the percent germination, dormancy, and overall viability of seeds. It is the most consistent way to assess viability. It is important to monitor viability, since non-viable seeds may not be apparent at other stages of processing. The seed germination rate of a specific seed lot is a key indicator as to how that seed will perform in the field. The vigor test is an important step of seed quality testing. Seed vigor directly determines the emergence Machine Vision Technique for Rapid Measurement of Soybean Seed Vigor

Whole-surface round object imaging method using line-scan hyperspectral imaging system

To achieve comprehensive online quality and safety inspection of fruits, whole-surface sample presentation and imaging regimes must be considered. Specifically, sample presentation method for round objects is under development to achieve effective whole-surface sample evaluation based on the use of a single hyperspectral line-scan imaging device. In this paper, a whole-surface round-object imaging method using hyperspectral line-scan imaging techniques is presented.