Gui-Ran Kim

Applicability of different analytical methods for the identification of γ-irradiated fresh mushrooms during storage

Photostimulated luminescence (PSL), thermoluminescence (TL), and electron spin resonance (ESR) analyses were performed to identify γ-irradiated (0, 1,2, and 3 kGy) fresh mushrooms (oyster, king oyster, and shiitake mushrooms) during storage at 5°C. PSL analysis gave negative results [<700 photon counts (PCs)] for the nonirradiated and intermediate (700–5,000 PCs) or positive results (>5,000 PCs) for the irradiated samples. The shape, intensity, and occurrence of TL glow curve in a typical temperature range (150–250°C) along with TL ratio (TL1/TL2) provided sufficient information to confirm the irradiation history of samples. Storage resulted in a negligible fading effect on PSL and TL characteristics. X-ray diffraction analysis showed the abundance of feldspar and quartz minerals in the separated dust from mushrooms. In detailed ESR analysis employing different sample pre-treatments, all samples were silent for radiation-specific ESR signals giving only a central signal (g=2.005) that showed an increase in intensity upon irradiation.

Effect of Nuruk and Fermentation Method on Organic Acid and Volatile Compounds in Brown Rice Vinegar

The effects of different nuruk contents and fermentation methods (AV, vinegar fermented in an agitated culture; SV, vinegar fermented in a static culture) on organic acids and volatile compounds in brown rice vinegars were investigated. In the SV, the contents of acetic, oxalic, tartaric, and malic acids increased with hipher contents of nuruk. Acetic, tartaric, and malic acid contents were higher in the SV than those in the AV. Volatile compounds that can affect vinegar quality, including acetic acid, isoamyl acetate, phenethyl acetate, and phenethyl alcohol were present at high concentrations in the AV. With the increase in nuruk contents in the AV, acetic acid content decreased and isoamyl acetate and phenethyl acetate content increased. No significant differences in sensory scores were observed regarding the amount of nuruk and the type of fermentation. However, electronic-nose analysis showed its potential to effectively differentiate different samples.

Quality Comparison of Commercial Cider Vinegars by Their Acidity Levels

The quality of commercial cider vinegars was compared according to their acidity levels (low, general, double strength and triple strength). The pH, reducing sugar content and brown color intensity decreased, while the total acidity increased with the increasing acidity levels, which may be resulted from difference in formulation and manufacturing procedures. The free sugars were mainly composed of fructose and glucose, which were the highest in low acidity vinegar, followed by double strength, general, and triple strength acidity vinegars. Acetic acids and malic acids were identified as the major organic acids. The citric acid concentration was the highest in triple strength vinegars. The contents of total phenolics and flavonoids were the highest in low acidity vinegars, which indicated their dependence on the apple juice content. DPPH and ABTS radical scavenging abilities were the highest in low acidity vinegars, that showed high amounts of antioxidants.

Microbiological and Physicochemical Quality Characterization of Commercial Red Pepper Powders

Ten commercially available red pepper powders were investigated for their hygienic quality (total aerobic count, yeasts and molds, and coliforms) and physicochemical properties (moisture content, pH, Hunters color values, American Spice Trade Association (ASTA) color and particle size). Microbial analysis resulted in 10 3 -10 6 CFU/g of total aerobic count and same of yeasts & molds, where 2 samples were positive (10 3 CFU/g) for coliforms. The moisture contents (7.25% to 12.73%) were with in the range as described in the Korean Food Standards Codex. Noteworthy variations were observed in pH (4.97 to 5.15), Hunters ∆E values (47.19 to 58.04) and ASTA color values (89.31 to 98.61). Although the color differences were evident among the samples, but the Hunter values were not in good correlations with ASTA color values. The average particle sizes of the all samples were comparable ranging from 605 µm to 1251 µm with few exceptions. There was a great variation in the key quality attributes of commer- cially available red pepper powders that should be considered for their various uses in food products.

Effect of Nuruks and Crude Amylolytic Enzyme on Free Amino Acid and Volatile Components of Brown Rice Vinegar Prepared by Static Culture

The effect of nuruks and crude amylolytic enzyme on free amino acid and volatile components of brown rice vinegar prepared by static cultures was investigated. Five groups consisted of AV (100% nuruk without crude amylolytic enzyme), BV (75% nuruk; 25% crude amylolytic enzyme), CV (50% nuruk; 50% crude amylolytic enzyme), DV (25% nuruk; 75% crude amylolytic enzyme) and EV (100% crude amylolytic enzyme without nuruk). Free amino acid content in AV vinegar (132.06 mg%) was lower than the others (184.56-191.22 mg%). Acetic acid, 3-methyl butyl acetate, acetoin and isoamyl alcohol were major volatile components as analyzed using gas chromatography-mass spectrometry after headspace solid-phase microextraction. Acetic acid in AV and EV samples represented 67.56% and 55.53% of total GC peak area, respectively. E-nose provided different patterns in each case showing variation in sensory properties.The effect of nuruks and crude amylolytic enzyme on free amino acid and volatile components of brown rice vinegar prepared by static cultures was investigated. Five groups consisted of AV (100% nuruk without crude amylolytic enzyme), BV (75% nuruk; 25% crude amylolytic enzyme), CV (50% nuruk; 50% crude amylolytic enzyme), DV (25% nuruk; 75% crude amylolytic enzyme) and EV (100% crude amylolytic enzyme without nuruk). Free amino acid content in AV vinegar (132.06 mg%) was lower than the others (184.56-191.22 mg%). Acetic acid, 3-methyl butyl acetate, acetoin and isoamyl alcohol were major volatile components as analyzed using gas chromatography-mass spectrometry after headspace solid-phase microextraction. Acetic acid in AV and EV samples represented 67.56% and 55.53% of total GC peak area, respectively. E-nose provided different patterns in each case showing variation in sensory properties.

Analysis of aroma compounds of commercial cider vinegars with different acidities using SPME/GC-MS, electronic nose, and sensory evaluation

Aroma compounds of commercial cider vinegars according to their acidity (low, moderate, double-strength, and triple-strength) were comparatively investigated. SPME/GC-MS analysis revealed 8 types of aroma compounds commonly existing in the vinegar including acetic acid. A cider vinegar with moderate acidity showed the most volatile profiles. Electronic nose analysis suggested that the peak at 0.40 s was a component related to total acidity of vinegar. Principal component analysis enabled e-nose to discriminate easily by presenting the separated position depending on total acidity. Significant differences with the acidity were observed in the pungent odor intensity and odor preference. According to the results, the moderate acidity vinegar was revealed to retain most volatile profiles and sensory odor. Compared to sensory evaluation, the analysis using SPME/GC-MS and e-nose provided more distinct patterns on their volatile compounds depending on their acidity, which might be a potential tool in determining the volatile profiles of cider vinegars.

Monitoring of Commercial Red Pepper Powders for Their Irradiation Status

Ten commercially available red pepper powders were investigated using photostimulated-luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR) analyses to confirm their irradiation status. The application of PSL, TL, and ESR analyses was also confirmed by in-house irradiation. In PSL-based screening, all samples gave negative photon counts (<700 PCs). The PSL calibration dose (1 kGy) showed a low sensitivity of 4 samples, while the others provided reliable screening results. TL glow curves demonstrated maximum peaks after 250 o C for the 6 samples; however 4 samples gave complex TL glow curves with maximum peaks in the range of 185-260 o C (radiation-specific), which could be the effect of an irradiated component in low concentration as the TL ratios of all samples were <0.1. Radiation-specific ESR features were absent in the all commercial samples. Variable irradiation detection properties were found; where the TL analysis showed the possible presence of an irradiated component in 4 samples requiring further monitoring and investigation.

Comparison of electron spin resonance (ESR) spectra of irradiated standard materials using different ESR spectrometers

Identification of different irradiated foods containing cellulose, sugars, or bone is possible using electron spin resonance (ESR) spectroscopy. In the present study, ESR spectral characteristics of radiation-induced radicals in irradiated standard materials (cellulose, sugars, and hydroxyapatite) were compared using different ESR spectrometers, such as JES-300 (JEOL, Japan), Miniscope MS-400 (Magnettech, Germany), and e-scan™ Food analyzer (Bruker, USA). Upon irradiation (0–10 kGy), all standard materials showed typical radiation-specific ESR spectra. Instrumental variations in signal intensity, spectral shapes, and detection applicability were observed and should be taken into consideration from practical point of view.

Luminescence Detection Characteristics for Irradiated Dried Fishes Using PSL-TL System

Photostimulated luminescence (PSL) and thermoluminescence (TL) analyses were conducted for the detection of different irradiated dried fishes. All the non-irradiated samples provided PSL counts of lower than 700 (negative: T1). Clear identification of irradiated sample was only possible for irradiated anchovy with PSL counts >5000; however, the results were unsatisfactory (not positive) for irradiated cod, dried filefish, hairtail, and herring samples. The contaminating silicate minerals were obtained by density separation or acid hydrolysis to perform TL analysis, which resulted in a low intensity of TL glow curve with a maximum peak after 250 o C for the non-irradiated samples that are irrespective of their kinds and methods for the mineral separation. The TL glow curves of high intensity with maximum peak in the temperature range of 150-250 o C were observed for all the irradiated samples. However, better results of TL glow curves and particularly of the TL ratio (TL 1 /TL 2 ) were obtained when the minerals were separated by a acid hydrolysis method.

Luminescence characteristics for identifying irradiated black soybeans.

PURPOSE Considering the commercial use of food irradiation and the prevalence of international trade of irradiated food and agricultural commodities, black soybeans originating from China or Korea were irradiated at 0-5 kGy. Photostimulated luminescence (PSL) and thermoluminescence (TL) were investigated for their ability to identify characteristics that would distinguish irradiated from non-irradiated samples. MATERIALS AND METHODS Dried black soybeans [Glycine max (L.) Merr.] were irradiated using a Co-60 gamma irradiator or an electron-beam accelerator and then analysed by PSL and TL. RESULTS PSL photon counts were higher in irradiated samples than in non-irradiated ones and increased with applied doses, making it possible to distinguish irradiated from non-irradiated samples. The TL analysis revealed glow curves (TL₁) with low intensity for non-irradiated samples but a higher intensity (approximately 200°C) for irradiated samples, showing increased intensities with radiation dose. The minerals were re-irradiated at 1 kGy and the second TL glow curve (TL₂) was measured. Based on the calculated TL ratios (TL₁/TL₂) and the shape of TL₁ glow curves, the irradiated samples could be distinguished from non-irradiated ones. CONCLUSIONS PSL and TL are effective screening and reference methods for distinguishing gamma ray or electron beam irradiated black soybeans from non-irradiated black soybeans.