Detection of genetically modified organisms obtained from food samples

Genetially modified organisms (GMOs) were explored in food samples obtained from November 2000 to March 2003 in the Tokyo area by using PCR and real-time PCR techniques. The existence of Roundup Ready Soybean (RRS) was surveyed in processed foods derived from soybeans, such as tofu, boiled soybean, kinako, nama-age, abura-age, natto, miso, soymilk and yuba. RRS was detected in 3 of 37 tofu, 2 of 3 nama-age, 2 of 3 yuba and 3 of 3 abura-age samples. The CBH351 in 70 processed corn foods, NewLeaf Plus and NewLeaf Y in 50 processed potato foods, and 55-1 papaya in 16 papayas were surveyed. These GMOs were not detected among the samples. Qualitative and quantitative analyses of RRS and genetically modified (GM) corn were performed in soybean, corn and semi-processed corn products such as corn meal, corn flour and corn grits. RRS was detected in 42 of 178 soybean samples, and the amount of RRS in RRS-positive samples was determined. The content was in the range of 0.1-1.4% in identity-preserved soybeans (non-GMO), and 49.8-78.8% in non-segregated soybeans. On the other hand, GM corns were detected in 8 of 26 samples. The amount of GM corn in GM corn-positive samples was in the range of 0.1-2.0%.     

A method for the determination of acrylamide in a broad variety of processed foods by GC-MS using xanthydrol derivatization

A novel GC-MS method was developed for the determination of acrylamide, which is applicable to a variety of processed foods, including potato snacks, corn snacks, biscuits, instant noodles, coffee, soy sauces and miso (fermented soy bean paste). The method involves the derivatization of acrylamide with xanthydrol instead of a bromine compound. Isotopically labelled acrylamide (d?-acrylamide) was used as the internal standard. The aqueous extract from samples was purified using Sep-Pak? C?? and Sep-Pak? AC-2 columns. For amino acid-rich samples, such as miso or soy sauce, an Extrelut? column was used for purification or extraction. After reaction with xanthydrol, the resultant N-xanthyl acrylamide was determined by GC-MS. The method was validated for various food matrices and showed good linearity, precision and trueness. The limit of detection and limit of quantification ranged 0.5-5 and 5-20?μg?kg?1), respectively. The developed method was applied as an exploratory survey of acrylamide in Japanese foods and the method was shown to be applicable for all samples tested.     

A method for the determination of acrylamide in a broad variety of processed foods by GC–MS using xanthydrol derivatization

A novel GC–MS method was developed for the determination of acrylamide, which is applicable to a variety of processed foods, including potato snacks, corn snacks, biscuits, instant noodles, coffee, soy sauces and miso (fermented soy bean paste). The method involves the derivatization of acrylamide with xanthydrol instead of a bromine compound. Isotopically labelled acrylamide (d ₃-acrylamide) was used as the internal standard. The aqueous extract from samples was purified using Sep-Pak? C₁₈ and Sep-Pak? AC-2 columns. For amino acid-rich samples, such as miso or soy sauce, an Extrelut? column was used for purification or extraction. After reaction with xanthydrol, the resultant N-xanthyl acrylamide was determined by GC–MS. The method was validated for various food matrices and showed good linearity, precision and trueness. The limit of detection and limit of quantification ranged 0.5–5 and 5–20?µg?kg^?1, respectively. The developed method was applied as an exploratory survey of acrylamide in Japanese foods and the method was shown to be applicable for all samples tested.     

Carbon-centered radicals in isolated soy proteins

ABSTRACT:  Solid-state electron paramagnetic resonance (EPR) spectroscopy of commercial samples of isolated soy proteins (ISP) revealed a symmetrical free-radical signal typical of carbon-centered radicals ( g = 2.005) ranging from 2.96 × 10¹⁴ to 6.42 × 10¹⁴ spins/g. The level of free radicals in ISP was 14 times greater than similar radicals in sodium caseinate, 29 times greater than egg albumin, and about 100 times greater levels than casein. Nine soy protein powdered drink mixes contained similar types of free radicals up to 4.10 × 10¹⁵ spins/g of drink mix, or up to 6.4 times greater than the highest free-radical content found in commercial ISP. ISP samples prepared in the laboratory contained trapped radicals similar to the levels in commercial ISP samples. When ISP was hydrated in 2.3 mM sodium erythorbate or 8.3 mM L-cysteine, frozen and dried, the level of trapped free radicals increased by about 17- and 19-fold, respectively. The ESR spectrum of defatted soybean flakes contained overlapping signals from the primary free-radical peak ( g = 2.005) and a sextet pattern typical of manganese-II. The manganese signal was reduced in the laboratory ISP and very weak in the commercial ISP.     

Effect of moisture, lipids, and select amino acid blocking agents on the formation and stability of metastable radicals in powdered soy proteins

Incremental increases in the moisture content of powdered soy protein products from 4.4% to 13.4% produced an inverse effect on the ability of soy proteins to maintain metastable free radicals. The corresponding reduction in electron paramagnetic resonance signal was not due to dielectric loss in the range of moisture contents examined. Subsequent evaluations of various treatments were conducted after drying soy proteins with molecular sieve to a water activity below 0.085 in order to minimize the influence from variations in moisture. Isolated soy protein (ISP) samples, prepared with "defatted flour" that had been further extracted with chloroform/methanol (2 : 1), had a 96% reduction in total lipids compared to the control ISP samples. The initial rate of radical accumulation in the "reduced-lipid" ISP for the first 3 wk was not significantly different from the initial rate of radical increases in the control ISP. After 3 wk, radical accumulation in the "reduced-lipid" ISP continued to increase, but at a rate that was less than the control. These findings indicate that the initial reactions contributing to the formation of metastable radicals in the powdered ISP are not strongly dependent on associated lipids. Blocking sulfhydryl groups during ISP preparation with N-ethylmaleimide did not significantly slow the rate of radical accumulation compared to the control ISP. Blocking arginine residues in ISP samples with phenylglyoxal caused an increased rate of radical accumulation for the first 4 wk. PRACTICAL APPLICATION: Levels of metastable radicals in powdered soy protein products typically range from 10 to 100 times greater than the free radicals in other food protein sources. This current research examines various compositional and treatment parameters that might be used to minimize the content of free radicals in foods containing soy proteins.     

Vitamin B12 Activity in Miso and Tempeh

The USP microbiological assay with L. leichmannii, ATCC 7830, was used to determine vitamin B₁₂ activity in light rice miso, dark rice miso, barley miso, tempeh and tempeh burger. Unpasteurized misos were found to have the highest B₁₂ content, averaging 0.21 μg/ 100g. Vitamin B₁₂ activity in miso ranged from a high of 0.25 μg/ 100g in barley miso to a low of 0.15 μg/100g in light rice miso. Pasteurized tempeh contained 0.12 μg vitamin B₁₂ per 100g food. Tempeh burger contained 0.06 to 0.11 μg vitamin B₁₂ per 100g food. The variation in vitamin B₁₂ activity found in these products may be due to different conditions used or produced during fermentation. Collaborative studies are needed and assessment of vitamin B₁₂ pseudoform activity before these foods can be considered a source of vitamin B₁₂.     

Determination of bisphenol A in foods using GC/MS

An analytical method using GC/MS was developed for bisphenol A (BPA) in foods and BPA was determined in canned foods and fresh foods such as vegetables, fruit and meat. BPA was extracted with acetone from the samples and the extract was concentrated at under 40 degrees C in vacuo to afford an aqueous solution, which was washed with hexane after alkalization and extracted with 50% diethyl ether-hexane after acidification. Extracts were cleaned up on a PSA and/or a C18 cartridge column, and BPA was derivatized with heptafluorobutyric anhydride and determined by GC/MS (SIM). This method was applicable to the detection and determination of BPA residues in food samples at the level of 1 ng/g. Among canned foods, BPA was found in 6 corned beef, 1 chicken, 9 sweet corn and 3 bean samples at the levels of 17-602 ng/g, 212 ng/g, 2.3-75 ng/g and 3.5-26 ng/g, respectively. BPA was also detected in 1 retort soup and 1 retort pack product at the levels of 11 ng/g and 86 ng/g, respectively. As for dairy products, BPA was not detected in butter and milk. Among fresh foods, BPA was detected in 2 fish and 3 liver samples at the levels of trace (tr)-6.2 ng/g and tr-2.2 ng/g, respectively. In vegetables, fruits and chocolates, a trace level of BPA was detected in only 1 chocolate. Traces of BPA were also detected in 3 samples of 6 boxed lunches.     

Effect of Soybean Cooking Temperature on the Texture and Protein Digestibility of Miso

Miso samples were prepared with soybeans cooked for 10 min at different temperatures (up to 100°C). Appreciable changes in the amount of 0.2 M trichloroacetic acid-soluble nitrogen (TCA-soluble N) and the pattern of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of fermented miso samples were observed in the temperature range between 90°C and 100°C. No further changes in the TCA-soluble N and SDS-PAGE pattern of miso were observed when the cooking time was prolonged up to 3 hr at 100°C. On the other hand, a 2 hr cooking period at 100°C was required to achieve a level of softness for cooked soybeans to give an acceptable texture of miso.     

Lunasin and Bowman-Birk protease inhibitor (BBI) in US commercial soy foods

The inverse association between the intake of soybean foods and cancer incidence and mortality rates supported by published literature has led to studies on identifying bioactive components. The cancer preventive properties of the soybean peptides lunasin and Bowman-Birk protease inhibitor (BBI) have been demonstrated by in vitro and in vivo assays. Since there is no comprehensive information on the concentrations of these two peptides, US commercially available soy foods, including soy milk, soy-based infant formula, tofu, bean curd, soybean cake, tempeh, natto, miso and su-jae samples, were analyzed for lunasin and BBI. Both peptides were present in most of the products, in varying concentrations, depending mainly on the soybean variety and the manufacturing process. Lunasin and BBI were absent in the fermentation products natto and miso, suggesting that fermentation destroys both peptides. To study the bioavailability of lunasin and BBI, three soy milk samples with different concentrations of these peptides were subjected to an enzymatic hydrolysis process simulating physiological digestion. The results confirm the important role BBI plays in the protection of lunasin from digestion by pepsin and pancreatin.     

Angiotensin I-Converting Enzyme Inhibitory Activity of Soy Protein Digests in a Dynamic Model System Simulating the Upper Gastrointestinal Tract

ABSTRACT: The objective of this study was to investigate whether peptides with inhibitory activity against angiotensin I-converting enzyme (ACE) would be produced by digestion of isolated soy protein (ISP) in a dynamic model system simulating gastrointestinal conditions. Using the model system, 5% ISP solution was pumped into the stomach reactor containing pepsin and HCl. The peptic digest was continuously pumped into the duodenum reactor containing pancreatin and Oxgall bile. The effects of blanching (100°C, 10 min) followed by pasteurization (75°C, 15 s) or sterilization (121°C, 20 min) of ISP before digestion on the inhibitory activity were also investigated. During the first 30 min of digestion, significantly higher ( P < 0.05) ACE-inhibitory activity was generated from unheated ISP after sequential digestion in both reactors compared with after peptic digestion only in the stomach reactor. However, at 90 min, subsequent digestion by pancreatin of unheated and blanched-sterilized ISP decreased ACE-inhibitory activity compared with peptic digestion alone. The IC₅₀ values at the end of 90 min digestion in both reactors were 0.38 ±0.01, 0.37 ± 0.02, and 0.44 ± 0.02 mg/mL for unheated, blanched-pasteurized, and blanched-sterilized ISP, respectively. The results suggest the potential production of peptides with ACE-inhibitory activity upon physiological digestion of soy protein, including products that have been subjected to heat processing. Although clinical trials would be required to provide final evidence of efficacy of the soy peptides, the present findings support the application of soy protein as an ingredient for functional foods.     

Freezing and Ice Recrystallization Properties of Sucrose Solutions Containing Ice Structuring Proteins from Cold-Acclimated Winter Wheat Grass Extract

ABSTRACT: The freezing properties of sucrose solutions containing ice structuring proteins (ISPs) from cold-acclimated winter wheat grass extract (AWWE) were evaluated. Neither significant ice nucleation nor thermal hysteresis activity in unpurified AWWE were detected ( P > 0.05). Ice recrystallization in sucrose solutions was assessed by bright field microscopy. Ice crystal growth was significantly reduced with the addition of more than 0.05% total protein from AWWE in 23% sucrose solutions frozen under static conditions and temperature cycled under long periods of time (60 min). Ice recrystallization inhibition was not evident when the samples were temperature cycled for shorter periods of time (10 min), indicating that an adsorption time may be required for the ISPs to be significantly active. The ice recrystallization was reduced with the increased on ISP concentration until reaching a plateau after adding 0.13% total protein from AWWE, representing a surface coverage of 9 mg protein/m² ice (assuming 100% adsorption). The reduction of ice crystal growth was as high as 74% compared with the control. This ice recrystallization inhibition offers significant opportunity for the use of ISPs from AWWE in frozen foods.     

Occurrence of zearalenone in Korean barley and corn foods

The presence of zearalenone (ZEN) in Korean foods such as barley, barley-based foods, corn, corn-based foods, fruits and vegetables was investigated by direct competitive enzyme-linked immunosorbent assay (dcELISA) and the liquid chromatography (LC) method. A total of 164 samples was collected from Seoul, Korea, in 1998 and 1999 including 30 barley, 32 barley-based foods, 18 corn, 47 corn-based foods, 19 dried red pepper, nine dried jujube, and nine dried persimmon. Average recoveries of ZEN from barley and corn by dcELISA were 138 and 145%, and by LC were 91 and 83% respectively at spiking levels of 5- 500ngg -1 . The detection limit for ZEN was 3ngg -1 by dcELISA and 4ngg -1 by LC. From 164 samples analysed, ZEN was found by dcELISA in 35 samples (21%) with a mean level of 30ngg -1 . Barley-based foods had the highest incidence of ZEN (38%) followed by barley (33%), corn-based foods (26%) and corn (22%). No ZEN was detected in any red pepper, jujube or persimmon samples. A high degree of correlation (r 2 = 0.86) was observed between the 35 positive samples detected by dcELISA and 31 samples by LC.     

Determination of benzo[a]pyrene in some Spanish commercial smoked products by HPLC-FL

In order to investigate the levels of the potently carcinogenic benzo[a]pyrene (BP), 31 samples of smoke foods were analysed. The samples tested included five samples of meat products, three samples of cheese and 22 samples of fish. A liquid chromatographic method was developed using a fluorescence detector. BP was found in 74% of the samples analysed. The levels varied from not detected to 2.46 mug/kg. Only one sample showed a BP level above 1 mug/kg, the maximum level that the EU intends to set for smoked foods.     

2017年深圳市家禽类食品兽药残留监测结果分析

目的 对深圳市家禽类食品中兽药残留水平进行测定和分析。方法 在深圳市10个行政区的商场超市、农贸市场及餐厅随机抽取鸡肉、鸭肉及鸡胃样品共计240份, 采用液相色谱-质谱/质谱法(liquid chromatography tandem mass spectrometry, LC-MS/MS)测定家禽类食品中11种喹诺酮类抗生素、4种四环素族抗生素、氯霉素及五氯酚酸钠的含量。结果 240份家禽类食品兽药残留的总体检出率为3.75%(9/240), 检出项目及其检出率分别为恩诺沙星2.08%(5/240)、环丙沙星0.83%(2/240)、沙拉沙星0.42%(1/240)、氧氟沙星0.42%(1/240)。其他7种喹诺酮类抗生素、四环素族抗生素、氯霉素及五氯酚酸钠均未检出。240份家禽类食品总体超标率为0.42%(1/240), 仅有1份鸡肉样品恩诺沙星超标。结论 2017年深圳市家禽类食品中兽药残留水平较低,氯霉素和五氯酚酸钠达到我国《动物性食品中兽药最高残留限量》中规定的在所有食品动物、所有可食组织中不得检出的要求。     

Twin-screw extrusion of cassava starch and isolated soybean protein blends

The effects of the extrusion parameters on isolated soybean protein (ISP) and cassava starch (CS) blends were studied. Extruded samples were prepared by using a ZSK-30 Werner and Pfleiderer twin-screw extruder. The study was carried out using Response Surface Methodology. The ISP followed by the moisture content were the most important linear variables significantly affecting axial expansion, specific volume, water solubility index and colour difference. The radial and axial expansion ranged from 2.30 to 3.77 and from 1.02 to 2.62, respectively. The highest ISP concentrations in the blends resulted in the highest specific volumes of the extrudates. Simultaneous increases of the barrel temperature and ISP level increased the water absorption index and lowered the water solubility index of the extrudates. Extruded products were softer at higher barrel temperature. The greatest difference in colour values was for the blends with the highest ISP concentration.     

Twin‐screw extrusion of cassava starch and isolated soybean protein blends

The effects of the extrusion parameters on isolated soybean protein (ISP) and cassava starch (CS) blends were studied. Extruded samples were prepared by using a ZSK‐30 Werner and Pfleiderer twin‐screw extruder. The study was carried out using Response Surface Methodology. The ISP followed by the moisture content were the most important linear variables significantly affecting axial expansion, specific volume, water solubility index and colour difference. The radial and axial expansion ranged from 2.30 to 3.77 and from 1.02 to 2.62, respectively. The highest ISP concentrations in the blends resulted in the highest specific volumes of the extrudates. Simultaneous increases of the barrel temperature and ISP level increased the water absorption index and lowered the water solubility index of the extrudates. Extruded products were softer at higher barrel temperature. The greatest difference in colour values was for the blends with the highest ISP concentration.     

Effect of Sequestering Intrinsic Iron on the Electron Paramagnetic Resonance Signals in Powdered Soy Proteins

This investigation examined iron in powdered soy protein products using electron paramagnetic resonance (EPR) spectroscopy, and the effect that selectively binding free iron in isolated soy protein (ISP) had on the occurrence of metastable radicals in powdered soy proteins. EPR analyses of soybean defatted flour, commercial ISP and laboratory ISP samples revealed a peak at g = 4.3 characteristic of high‐spin ferric iron in a rhombic‐coordinated environment. Commercial ISP samples examined contained higher levels of the rhombic ferric iron than laboratory‐prepared ISP samples. During the first 6 wk of storage the primary singlet EPR signal at g = 2.0049 in the commercial ISP samples approximately doubled, and the laboratory prepared samples increased by about 9‐fold. The EPR signal was initially about 4‐times higher in the freshly prepared commercial samples compared to the corresponding laboratory ISP. Laboratory ISP samples prepared with added deferoxamine to sequester endogenous iron exhibited a large increase in the high‐spin ferric iron EPR signal at g = 4.3. ISP treated with deferoxamine also exhibited a multiple‐line EPR signal at about g = 2.007, instead of the typical singlet signal at g = 2.0049. The power at which the signal amplitude was half‐saturated also changed from about 1 mW in the control ISP to about 20 mW in the deferoxamine treated ISP. The multiple‐line EPR spectrum from the ISP treated with deferoxamine increased during storage over a 6‐wk period by about 6‐fold. The observed changes in EPR line‐shape, g‐value, and power saturation with the deferoxamine treatment indicate that the primary free‐radical signal in powdered ISP samples may be from stabilized tyrosine radicals with spin densities distributed over the aromatic ring.     

Headspace volatiles along with other instrumental and sensory analyses as indices of maturation of horse mackerel miso

Development of aroma-active compounds during fermentation in the preparation of fermented fish-meat paste product (fish miso) from horse mackerel meat was quantitatively determined and characterized by olfactometric and organoleptic assessments. The critical ripening time was estimated by quantitative and/or qualitative analyses of volatile compounds, peptides, amino acids, product color, and total phenolics of the fish miso matrix throughout fermentation. The results confirmed that the application of koji for the fermentation of horse mackerel meat to produce fish miso significantly reduced the fishy off odor and promoted the development of highly acceptable fish miso with a nutty, cheesy, and fruity aroma. Ethyl acetate, ethyl heptanoate, ethyl decanoate, 2-methylpropanal, 3-methylbutanal, 2,3-butanedione, dimethyl trisulfide, and 3-(methylthio) propanal were identified as key odor-active compounds in fish miso prepared from horse mackerel meat. Among the volatiles, 2-methylpropanal, 3-methylbutanal, and 2,3-butanedione were identified to serve as potential indicators of the maturation of fish miso. Amino acid content could also be a potential indicator of maturation of protein-rich, fermented products such as fish miso. In addition, surface color analysis of fish miso revealed a high correlation between sensory attributes and color components. Specifically, r and b values were considered potential indicators of maturation. Practical Application: Variability is a major drawback in fermented products such as fish miso and it requires establishing the optimum ripening time, defined as that providing the aroma attributes qualitatively and quantitatively mostly appreciated by consumers. We have carried out this work for comprehensive determination of the critical ripening time by applying several instrumental and sensory tools including quantitative and/or qualitative analysis of volatile compounds, peptides, amino acids, product color, and total phenolics of the fish miso matrix throughout the fermentation period. The outcome of the present study can be efficiently applied for detection of maturation in similar types of fermented product for large-scale production.     

大理州地方特色食品食源性致病菌污染状况及相关危险因素分析

目的 了解大理州地方特色食品中食源性致病菌污染状况和相关危险因素。方法 按照GB/T 4789-2016《食品微生物检验标准》对2016~2017年采集的2种特色食品(生皮、乳扇)共153件进行金黄色葡萄球菌和沙门氏菌的检测。检测结果按照不同年度、不同来源、不同种类、不同季度进行分析比较。结果 153件样品中, 共有35件检出致病菌, 阳性率为22.88%。2016~2017年阳性率分别为34.72%和12.35%。采自餐饮环节和农贸市场的样品阳性率分别为21.51%和25.00%。2种特色食品均检出致病菌, 生皮(凉拌生猪皮)阳性率较高为24.24%, 乳扇阳性率为20.37%。在检出的35株致病菌中, 主要是金黄色葡萄球菌(85.71%)。各季度间食源性致病菌的检出率差异有统计学意义(P<0.05)。结论 大理州地区特色食品致病菌污染存在潜在风险, 应加强食品安全风险监测, 提高人群健康教育水平。     

Determination of epoxidized soybean oil in bottled foods

A determination method for epoxidized soybean oil (ESBO) in bottled foods was developed and used to survey bottled foods on the Japanese market. The amount of sample required was decreased to 20 g and the standard addition method was adopted for the quantification, because lipid in foods interrupted the hydrolysis of ESBO. The recoveries were 87.1 and 98.9% and the determination limit was 5.0 microg/g for a 20 g sample, be cause lipid in foods interupted the hydrolysis of ESBO. The recoveries using the internal standard method varied widely, because hydrolysis of the internal standard, cis-11,14-eicosadienoic acid ethyl ester, was affected more than that of ESBO by coexisting lipid in the sample. ESBO was not detected in any of the bottled baby food samples examined (14 samples), though it had been frequently detected in previous European surveys. This difference may be related to the low fat content and low fluidity of the bottled baby foods retailed in Japan. On the other hand, ESBO was detected at levels of 25.7-494.0 microg/g in liver paste, pasta sauce, Sungan in spicy oil, and spicy oil. These foods had higher fat content and higher fluidity. However, ESBO intake from these foods appears unlikely to exceed the TDI in the EU (1 mg/kg bw/day).