Hyun Ee Ok

Natural Occurrence of Aflatoxin B1 in Marketed Foods and Risk Estimates of Dietary Exposure in Koreans

Aflatoxin B1 (AFB1) is an unavoidable food contaminant. To evaluate the potential health risk of AFB1 to Koreans posed by food consumption, we determined the natural occurrence of AFB1 in food and estimated the excess risk for liver cancer through dietary exposure to AFB1. A total of 694 food samples collected from six different regions of South Korea were analyzed for their AFB, content. One hundred four of the 694 samples were found to give positive enzyme-linked immunosorbent assay (ELISA) readings for AFB1 and were further investigated with high-performance liquid chromatography. Thirty-two samples, including 2 maize samples, 3 soybean products, 20 peanut samples, nut samples, and their products, and 7 spices, were found to be contaminated with AFB1 (4.6% incidence), up to 48.6 microg kg(-1). The level of AFB1 contamination in 28 of the 32 food products was below 10 microg kg(-1), which is the legal tolerance limit in Korea. From data on daily food consumption, the exposure dose of AFB1 was estimated to be 6.42 x 10(-7) mg kg(-1) body weight (bw) day(-1). The major contributors to the dietary intake of AFB1 were soybean paste and soy sauce, which composed 91% of the total exposure to AFB1. The excess risk of liver cancer for those exposed to AFB1 through food intake was estimated to be 5.78 x 10(-6) for hepatitis B-negative individuals and 1.48 x 10(-4) for hepatitis B-positive individuals. These results suggest that special consideration is required to reduce the intake of AFB1 in hepatitis B-positive individuals.

Determination of deoxynivalenol in cereal-based foods and estimation of dietary exposure.

Deoxynivalenol (DON) is a trichothecene mycotoxin. DON contamination in agricultural food staples such as wheat, barley, and maize due to Fusarium colonization is an increasing problem. In order to provide risk managers with better guidance for regulatory measures, the concentration of DON in cereal-based foods (n = 689), collected from six cities between June 2005 and August 2008, was determined. Further, dietary exposure to DON was estimated by combining data on DON concentration in these foods with their consumption rates. Among 689 samples, 272 samples (39%) were contaminated with DON. Relatively high DON concentrations were found in dried corn, with a mean concentration of 109 μg/kg (n = 74). Daily intake of DON simulated by the @Risk program was estimated to between 0.066 and 0.142 μg/kg body weight (bw)/d for males and between 0.066 and 0.144 μg/kg bw/d for females. The major contributor to DON exposure in the 50th and 95th percentile intake groups was polished rice. For each age class, young children (3–6 yr) showed the highest relative intake, with a mean intake of 0.142 μg/kg bw/d for males and 0.144 μg/kg bw/d for females. However, the estimated daily DON intake did not exceed the provisional maximum tolerable daily intake (1 μg/kg bw/d) for any age group or gender. From our risk assessment, it was concluded that the current intake of DON in South Korea may not serve as a serious health hazard.

HPLC and UPLC methods for the determination of zearalenone in noodles, cereal snacks and infant formula.

High-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC) were compared to validate a method for determination of zearalenone (ZON) in noodles, cereal snacks, and infant formulas. The limits of detection and quantification in HPLC and UPLC were found to be 4.0 and 13.0 μg kg(-1) and 2.5 and 8.3 μg kg(-1), respectively. The average recoveries of ZON by HPLC and UPLC ranged from 79.1% to 105.3% and from 85.1% to 114.5%, respectively. The measurement uncertainties of the two methods for ZON determination were within the maximum standard uncertainty. The two methods showed that the levels of ZON in 163 naturally contaminated samples ranged from 4.3 to 8.3 μg kg(-1) by HPLC and 3.1 to 17.6 μg kg(-1) by UPLC. These findings indicate that either method is suitable for the determination of ZON in noodles, cereal snacks, and infant formulas, but UPLC gives faster results with better sensitivity.

Occurrence and intake of deoxynivalenol in cereal-based products marketed in Korea during 2007–2008

The occurrence of deoxynivalenol (DON) was investigated in 514 cereal-based products (corn-based, n = 125; barley-based, n = 96; wheat-based, n = 94; rice-based, n = 199) marketed in Korea during 2007−2008, and estimates of DON intake were determined. Samples were analysed by high-performance liquid chromatography (HPLC) with ultraviolet light (UV) detection after immunoaffinity clean-up. The limits of detection (LOD) and limits of quantification (LOQ) were 2.2 and 5.6 µg kg–1, respectively. Recoveries and repeatability expressed as coefficients of variation (CV) were 82.3–100% and 2.4–15.3% in beer, bread and dried corn. The incidences and mean levels of DON were 56% and 68.9 µg kg−1 for corn-based products, 49% and 24.1 µg kg−1 for wheat-based products, 43% and 7.5 µg kg−1 for barley-based products, and 16% and 3.4 µg kg−1 for rice-based products, respectively. The estimated daily intake of DON from the consumption of rice-based, wheat-based, barley-based and corn-based products were 0.0038 µg kg−1 bw day−1, 0.0032 µg kg−1 bw day−1, 0.0015 µg kg−1 bw day−1 and 0.0002 µg kg−1 bw day−1, respectively. These values represent 0.38%, 0.32%, 0.25% and 0.01% of the provisional maximum tolerable daily intake (PMTDI) of 1 µg kg−1 bw day−1. These results indicate that rice-based products are major contributors to DON exposure in Korea, even though the current exposure level is unlikely to cause adverse health effects.

Natural occurrence of type-B trichothecene mycotoxins in Korean cereal-based products

Type-B trichothecenes (deoxynivalenol (DON), nivalenol (NIV), fusarenone-X (FUS-X), 15-acetyldeoxynivalenol (15ADON), and 3-acetyldeoxynivalenol (3ADON)) were determined in 338 cereal-based products. Detection limit, quantification limit and mean recovery for five toxins were in the ranges 0.7–2.6 µg kg−1, 2.1–7.8 µg kg−1 and 73–110%, respectively. The range of occurrence and average level in samples were, respectively, 21–88% and 5.2–121.8 µg kg−1 for NIV, 10–96% and 1.7–109.5 µg kg−1 for DON, 2–39% and 0.4–3.6 µg kg−1 for FUS-X, 0–80% and 0–17.3 µg kg−1 for 15ADON, and 0–29% and 0–1.5 µg kg−1 for 3ADON. Regarding co-occurrence, 64% of samples had more than two type-B trichothecenes. The estimated daily intakes of NIV, DON, FUS-X, 15ADON, and 3ADON were 0.077, 0.048, 0.004, 0.006 and 0.002 µg kg−1 bw day−1, respectively. These results suggest that current exposure levels do not indicate the possibility of adverse effects, but consideration of the combined exposure of type-B trichothecenes may be required due to the high frequency of co-occurrence.

Simple high-performance liquid chromatography method for the simultaneous analysis of aflatoxins, ochratoxin A, and zearalenone in dried and ground red pepper.

Aflatoxins B1, B2, G1, G2 (AFB1, AFB2, AFG1, AFG2), ochratoxin A (OTA), and zearalenone (ZEA) in dried and ground red pepper (Capsicum annuum) were simultaneously analyzed with high-performance liquid chromatography coupled to fluorescence detection after post-column derivatization. The analytical method was validated for specificity, selectivity, linearity, limits of detection and quantification, recovery, precision, and measurement of uncertainty. The limits of detection and quantification were 0.10 and 0.25 μg/kg for AFB1, 0.04 and 0.06 μg/kg for AFB2, 0.14 and 0.50 μg/kg for AFG1, 0.05 and 0.10 μg/kg for AFG2, 0.12 and 0.45 μg/kg for OTA, and 4.00 and 13.25 μg/kg for ZEA, respectively. The average recoveries ranged from 80.4 to 98.5% for different concentrations of AFB1, AFB2, AFG1, AFG2, OTA, and ZEA in spiked samples. The measurement uncertainties were 0.64 to 1.62 μg/kg for AFB1, 0.24 to 0.45 μg/kg for AFB2, 0.79 to 2.19 μg/kg for AFG1, 0.32 to 0.61 μg/kg for AFG2, 0.81 to 2.31 μg/kg for OTA, and 8.48 to 26.25 μg/kg for ZEA. This method was successfully applied for the simultaneous determination of mycotoxins for 78 red peppers collected from Korean and Indian markets. Aflatoxins (sum of AFB1, AFB2, AFG1, and AFG2) were detected in 2% of nonpacked samples (n = 23) and 43% of packed samples (n = 55), at levels of 0.04 to 38.03 μg/kg. OTA was detected in 4% of nonpacked samples and 48% of packed samples, at levels of 0.15 to 56.30 μg/kg. ZEA was not detected in any samples. These findings indicate that the analytical method described here is suitable for the routine determination of the amounts of AFs, OTA, and ZEA in dried and ground red pepper.

Estimate of zearalenone exposure through the intake of white and brown rice in the Korean population

Rice samples (n = 482) harvested for 2010–2012 in South Korea were analyzed for zearalenone content by high-performance liquid chromatography and fluorescence detection. The exposure of the Korean populations was assessed by a deterministic approach. Because the proportion of non-detectable results was >80% in white rice but less than <60% in brown rice, the zearalenone levels for white rice were reported as 0.52 µg kg−1 as lower bound and 2.54 µg kg−1 as upper bound, while for brown rice the middle bound value was 13.9 µg kg−1. The average dietary intake of zearalenone from white and brown rice by the Korean population was estimated to be 1.5 ng kg−1 body weight (bw) day−1 each. For heavy consumers, the average intakes were 18.5 and 10.1 ng kg−1 bw day−1, respectively. The age groups with the highest zearalenone intake were 1–2-year-old children for white rice and 3–6-year-old children for brown rice. Overall, the dietary exposure of the Korean population to zearalenone from white and brown rice was found to be lower than the provisional maximum tolerable daily intake of 0.5 μg kg−1 bw day−1.

T-2 and HT-2 toxins in cereals and cereal-based products in South Korea

A total of 214 samples, consisting of brown rice, barley, mixed grains, corn, wheat and wheat flour were analysed for T-2 and HT-2 toxins using high-performance liquid chromatography with fluorescence detection. Recovery and repeatability were 79.9%–107.5% and 4.9%–14.5% for T-2, and 74.0%–106.1% and 5.0%–17.9% for HT-2, respectively. T-2 toxin was detected in 11 (5.1%) of all samples. The highest incidence was found in corn (21.7%) followed by mixed grains and brown rice. Mean of all samples was 1.5–4.1 µg kg−1, the maximum level being 41.5 µg kg−1 in corn. HT-2 toxin was detected in 126 (58.9%) of all samples, and the mean values were 26.4–59.2 µg kg−1. The estimated daily intakes for the sum of T-2 and HT-2 toxins were 2.56, 3.22, 2.53, 0.03, 0.01 and 2.45 ng (kg bw)−1 day−1 in brown rice, barley, mixed grains, corn, wheat and wheat flour, respectively.

Detection of Foodborne Pathogens and Mycotoxins in Eggs and Chicken Feeds from Farms to Retail Markets.

Contamination by foodborne pathogens and mycotoxins was examined in 475 eggs and 20 feed samples collected from three egg layer farms, three egg-processing units, and five retail markets in Korea. Microbial contamination with Salmonella species, Escherichia coli, and Arcobacter species was examined by bacterial culture and multiplex polymerase chain reaction (PCR). The contamination levels of aflatoxins, ochratoxins, and zearalenone in eggs and chicken feeds were simultaneously analyzed with high-performance liquid chromatography coupled with fluorescence detection after the post-derivatization. While E. coli was isolated from 9.1% of eggs, Salmonella species were not isolated. Arcobacter species were detected in 0.8% of eggs collected from egg layers by PCR only. While aflatoxins, ochratoxins, and zearalenone were found in 100%, 100%, and 85% of chicken feeds, their contamination levels were below the maximum acceptable levels (1.86, 2.24, and 147.53 μg/kg, respectively). However, no eggs were contaminated with aflatoxins, ochratoxins, or zearalenone. Therefore, the risk of contamination by mycotoxins and microbes in eggs and chicken feeds is considered negligible and unlikely to pose a threat to human health.