Evaluation of 2-dodecylcyclobutanone as an irradiation dose indicator in fresh irradiated ground beef

Alkylcyclobutanones (2-ACBs) are radiolytic products formed when fatty acids are irradiated. These cyclobutanones are unique irradiation byproducts and therefore may serve as indicators of irradiation exposure. As only limited information exists about 2-ACB formation in retail meat products, reliable methods that can quantify 2-ACBs and thus estimate irradiation dose in commercial meat products are desired. The cyclobutanone studied in this experiment was 2-dodecylcyclobutanone (2-DCB), which is formed from palmitic acid. The formation of 2-DCB was evaluated in fresh irradiated ground beef patties at two fat levels. Patties containing 15% and 25% fat were irradiated by electron beam at 1.0, 2.0, 3.0, and 4.5 kGy. Commercially available 1-lb irradiated ground beef chubs with different fat levels were analyzed in order to estimate dose absorbed by these samples. The 2-DCB was extracted using supercritical fluid extraction (SFE) and analyzed by gas chromatography-mass spectroscopy (GC-MS) and was detected in all the irradiated samples. The concentration of 2-DCB increased linearly with dose with R2 = 0.9646 for 25% fat samples and R2 = 0.9444 for 15% fat samples. Further, there was no significant difference in 2-DCB concentrations between the two fat levels. The estimated doses applied to the commercial samples ranged between 1.38 and 1.55 kGy, values consistent with doses normally used in the industry (1.0-2.0 kGy). Our results show that 2-DCB can be used to monitor fresh irradiated beef and approximate the absorbed dose.     

2-alkylcyclobutanones as irradiation dose indicators in irradiated ground beef patties

Alkylcyclobutanones have been recognized as chemical markers of irradiated lipid-containing foods since 1970. They are important because they are produced solely as a result of irradiation and not any other processing method. This study investigated the formation of 2-dodecylcyclobutanone (2-DCB) and 2-tetradec-5'-enylcyclobutanone (2-TDCB) in irradiated ground beef patties from commercial and noncommercial sources. Patties were irradiated using a (60)C source (gamma-irradiation) and electron beam irradiation, at five targeted absorbed doses of 0.5, 1.0, 2.5, 5.0, and 7.0 kGy. Commercially available irradiated patties were also studied. A supercritical fluid extraction (SFE) procedure was optimized and used for the extraction and isolation of the alkylcyclobutanones. Samples can be used for extraction without a prior cleanup step, which makes this procedure rapid and convenient to use. Identification and quantitation of the cyclobutanones were done by gas chromatography-mass spectroscopy. 2-DCB was detected in all of the irradiated samples (including commercial patties), and its concentration increased linearly with the irradiation dose. Electron beam irradiation produced a greater amount of 2-DCB compared to gamma-irradiation at dose levels >2.5 kGy. 2-TDCB was detected only at the two higher irradiation doses, whereas both marker compounds were not detected in the non-irradiated samples.     

Metabolism of theanine, gamma-glutamylethylamide, in rats

The metabolism of theanine, one of the major amino acid components in tea (Camellia sinensis), was studied in rats. High-performance liquid chromatography (HPLC) with fluorometric detection was used to evaluate the nature of theanine's metabolites in plasma, urine, and tissues. In the urine samples collected after administration of 100, 200, and 400 mg each of theanine, intact theanine, L-glutamic acid, and ethylamine, these compounds were detected in a dose-dependent manner. When 200 mg of theanine was orally administered to rats, the plasma concentrations of theanine and ethylamine reached their highest levels about 0.5 and 2 h after administration, respectively. It seems most likely that the enzymatic hydrolysis of theanine to glutamic acid and ethylamine was accomplished in the kidney. These results indicate that orally administered theanine is absorbed through the intestinal tract and hydrolyzed to glutamic acid and ethylamine in the rat kidney.     

Metabolism of oak leaf ellagitannins and urolithin production in beef cattle

Oak leaves have a high concentration of ellagitannins. These phytochemicals can be beneficial or poisonous to animals. Beef cattle are often intoxicated by oak leaf consumption, particularly after suffering feed restriction. The severity of the poisoning has recently been associated with the ruminal microbiota, as different bacterial populations were found in animals that tolerated oak leaves and in those that showed clinical and pathological signs of toxicity. Intoxication has previously been linked to the production of phenolic metabolites, particularly catechol, phloroglucinol, and resorcinol. This suggested that the microbial metabolism of ellagitannins could also be associated with its tolerance or intoxication in different animals. Therefore, it is essential to understand the metabolism of ellagitannins in cattle. Here we show that ellagitannins are metabolized in the cattle rumen to urolithins. Different urolithins were detected in ruminal fluid, feces, urine, and plasma. Oak leaf ellagitannins declined as they were converted to urolithins, mainly isourolithin A and urolithin B, by the ruminal and fecal microbiota. Urolithin aglycons were observed in rumen and feces, and glucuronide and sulfate derivatives were detected in plasma and urine. Sulfate derivatives were the main metabolites detected in plasma, while glucuronide derivatives were the main ones in urine. The main urolithins produced in cattle were isourolithin A and urolithin B. This is a relevant difference from the monogastric mammals studied previously in which urolithin A was the main metabolite produced. Low molecular weight phenolics of the benzoic, phenylacetic, and phenylpropionic groups and metabolites such as catechol, resorcinol, and related compounds were also detected. There was a large variability in the kinetics of production of these metabolites in individual animals, although they produced similar metabolites in all cases. This large variability could be associated with the large variability in the rumen and intestine microbiota that has previously been observed. Further studies are needed to demonstrate if the efficiency in the metabolism of ellagitannins by the microbiota could explain the differences observed in susceptibility to intoxication by the different animals.     

Pharmacokinetics of cycloalliin, an organosulfur compound found in garlic and onion, in rats

Cycloalliin, an organosulfur compound found in garlic and onion, has been reported to exert several biological activities and also to remain stable during storage and processing. In this study, we investigated the pharmacokinetics of cycloalliin in rats after intravenous or oral administration. Cycloalliin and its metabolite, (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid, in plasma, urine, feces, and organs was determined by a validated liquid chromatography-mass spectrometry method. When administered intravenously at 50 mg/kg, cycloalliin was rapidly eliminated from blood and excreted into urine, and its total recovery in urine was 97.8% +/- 1.3% in 48 h. After oral administration, cycloalliin appeared rapidly in plasma, with a tmax of 0.47 +/- 0.03 h at 25 mg/kg and 0.67 +/- 0.14 h at 50 mg/kg. Orally administered cycloalliin was distributed in heart, lung, liver, spleen, and especially kidney. The Cmax and AUC0-inf values of cycloalliin at 50 mg/kg were approximately 5 times those at 25 mg/kg. When administered orally at 50 mg/kg, cycloalliin was excreted into urine (17.6% +/- 4.2%) but not feces. However, the total fecal excretion of (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid was 67.3% +/- 5.9% (value corrected for cycloalliin equivalents). In addition, no (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid was detected in plasma (<0.1 microg/mL), and negligible amounts (1.0% +/- 0.3%) were excreted into urine. In in vitro experiments, cycloalliin was reduced to (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid during anaerobic incubation with cecal contents of rats. These data indicated that the low bioavailability (3.73% and 9.65% at 25 and 50 mg/kg, respectively) of cycloalliin was due mainly to reduction to (3R,5S)-5-methyl-1,4-thiazane-3-carboxylic acid by the intestinal flora and also poor absorption in the upper gastrointestinal tract. These findings are helpful for understanding the biological effects of cycloalliin.     

3-Mercapto-2-methylpentan-1-ol, a new powerful aroma compound

3-Mercapto-2-methylpentan-1-ol was first detected in a complex thermally processed flavor and finally isolated from raw onions. The chemical structure of this new compound was identified by MS and (1)H NMR measurement and synthesis of the proposed structure. Sensory evaluation at different concentrations indicated that the flavor quality is strongly dependent on concentration. At low concentration (0.5 ppb) a pleasant meat broth, sweaty, onion, and leek-like odor can be perceived. On the basis of some isolation experiments and volatiles occurring in raw onions, a formation pathway is proposed. As one intermediate 3-mercapto-2-methylpentanal, another new strong flavor compound, was suggested. The presence of this compound in raw onions was confirmed by synthesis and comparison of MS and chromatographic data.     

Identification and synthesis of 2-heptanethiol, a new flavor compound found in bell peppers

2-Heptanethiol was identified for the first time as a constituent of red and green bell pepper extracts. The chemical structure of this new aroma compound was proposed on the basis of mass spectra and retention indices and confirmed by chemical synthesis and nuclear magnetic resonance spectroscopy measurements. Its aroma properties were described as sulfury, onion-like, and vegetable-like, reminiscent of bell pepper at lower concentrations, with an orthonasal detection threshold of 10 microg/L of water. No differences in odor note and threshold value were observed for the enantiomeric forms, which were prepared from enantiopure 2-heptanol by tosylation, followed by thioacetylation and reduction, giving the target thiol enantiomers.     

Metabolism of furametpyr. 2. (14)C excretion, (14)C concentrations in tissues, and amounts of metabolites in rats

14C-Labeled furametpyr [N-(1,3-dihydro-1,1, 3-trimethylisobenzofuran-4-yl)-5-chloro-1, 3-dimethylpyrazole-4-carboxamide, Limber] was dosed to male and female rats at 1 (low dose) and 200 or 300 mg/kg (high dose). Elimination of furametpyr was rapid, and the dosed (14)C was substantially excreted within 7 days (45.5-53.3% in feces, 44.1-53. 8% in urine, and 0.01% in expired air). However, (14)C excretion rate showed sex- and dose-related differences, more rapid in males at low dose. (14)C concentrations in tissues decreased rapidly to generally low levels at 7 days (<0.004 ppm with the low dose and <1. 1 ppm with the high dose). Forty metabolites were detected, and 13 metabolites and 4 glucuronides were identified. A small amount of unchanged furametpyr was detected in feces (0.1-0.5% of the dose). The major metabolites in tissues were N-demethylated metabolites. In a bile study, 52.5-54.2% of the dosed (14)C was rapidly excreted into bile within 2 days. The absorption ratio was estimated to be >93.7% for the low dose (1 mg/kg). Major metabolites in bile were glucuronic acid conjugates of furametpyr hydroxides. On the basis of the results, furametpyr is substantially absorbed from the gastrointestinal tract after oral administration, rapidly distributed to tissues, extensively metabolized, and excreted into urine and bile or feces.     

Bioaccessibility and transport by Caco-2 cells of organoarsenical species present in seafood

Organoarsenical standards and raw and cooked seafood (DORM-2, sole, and Greenland halibut) were subjected to in vitro gastrointestinal digestion to estimate arsenic bioaccessibility (maximum soluble concentration in gastrointestinal medium). The in vitro digestion did not modify the chemical form of the organoarsenic species standards. In seafood, bioaccessibility was 67.5-100% for arsenobetaine (AB), 30% for dimethylarsinic acid (DMA), 45% for tetramethylarsonium ion (TETRA), and >50% for trimethylarsine oxide (TMAO). Cooking induced no changes in bioaccessible contents. In addition, transport by Caco-2 cells, an intestinal epithelia model, was evaluated from organoarsenical standards and DORM-2. For standards, transport ranged from 1.7% for AB to 15.5% for TETRA. In DORM-2, transport was observed for only AB (12%), with far higher efficiency than in the case of the standard solution, thus illustrating the interest of using whole foods for studying bioavailability.     

电子鼻在牦牛肉和牛肉猪肉识别中的应用

为了探索电子鼻对肉类掺假识别的可行性,利用电子鼻对牦牛肉、牛肉和猪肉样品进行了分析。通过对所获得的数据进行主成分分析（principal component analysis,PCA）、判别因子分析（discriminant factor analysis,DFA）和偏最小二乘回归分析（partial least-squares analysis,PLS）。结果表明：几种肉类在电子鼻传感器上有不同的特征性响应图谱,电子鼻能够有效识别猪、牛肉;同时电子鼻能够识别不同部位的牦牛肉和普通牛肉;但不能识别不同部位的猪肉。在牛肉馅中掺入不同比例的猪肉馅时,电子鼻也能进行识别。采用偏最小二乘回归分析对数据进行处理,电子鼻响应信号和猪肉馅掺入比例之间有很好的相关性（决定系数R2为0.9762）,PLS模型预测误差在1.27%～7.00%之间。试验证明电子鼻可用于肉类的识别。     

Metabolism of the olive oil phenols hydroxytyrosol, tyrosol, and hydroxytyrosyl acetate by human hepatoma HepG2 cells

To study the potential hepatic metabolism of olive oil phenols, human hepatoma HepG2 cells were incubated for 2 and 18 h with hydroxytyrosol, tyrosol, and hydroxytyrosyl acetate, three phenolic constituents of olive oil. After incubation, culture media and cell lysates were hydrolyzed with beta-glucuronidase and sulfatase and analyzed by LC-MS. In vitro methylation, glucuronidation, and sulfation of pure phenols were also performed. Methylated and glucuronidated forms of hydroxytyrosol were detected at 18 h of incubation, together with methylglucuronidated metabolites. Hydroxytyrosyl acetate was largely converted into free hydroxytyrosol and subsequently metabolized, yet small amounts of glucuronidated hydroxytyrosyl acetate were detected. Tyrosol was poorly metabolized, with <10% of the phenol glucuronidated after 18 h. Minor amounts of free or conjugated phenols were detected in cell lysates. No sulfated metabolites were found. In conclusion, olive oil phenols can be metabolized by the liver as suggested by the results obtained using HepG2 cells as a hepatic model system.     

Aroma compound sorption by oak wood in a model wine

Oak wood used for wine barrels was immersed into a model wine containing eight aroma compounds (e.g., aromatic and terpene alcohols, ethyl esters, and aldehyde), for which activity coefficients in water and model wine were determined using the mutual solubility measurement. A mass balance of these volatiles considering their reactivity in model wine was established. For most of the studied aroma compounds, and mainly for linalool and ethyl octanoate, a sorption behavior into wood was reported for the first time. This phenomenon was selective and could not be related to the solubilities in model wine and hydrophobicities of the studied aroma compounds, suggesting that acid-base and polar characteristics of wood were more involved in this sorption mechanism. This study has also shown that the level of sorption is a function of the ratio of wood surface area/solution volume.     

Precursors of 2-acetyl-1-pyrroline, a potent flavor compound of an aromatic rice variety

The biological formation of a potent flavor compound, 2-acetyl-1-pyrroline, in the aromatic rice variety (Khao Dawk Mali 105) was studied in seedlings and callus of the rice. Concentrations of 2-acetyl-1-pyrroline were determined by GC-MS-SIM using an isotope dilution method. Increases in concentration occurred when proline, ornithine, and glutamate were present in solution, with proline increasing the concentration by more than 3-fold compared to that of the control. Results of tracer experiments using (15)N-proline, (15)N-glycine, and proline-1-(13)C indicated that the nitrogen source of 2-acetyl-1-pyrroline was proline, whereas the carbon source of the acetyl group was not the carboxyl group of proline. 2-acetyl-1-pyrroline was formed in the aromatic rice at temperatures below that of thermal generation in bread baking, and formed in the aerial part of aromatic rice from proline as the nitrogen precursor.     

Isolation and identification of 2-methoxy-3,5-dimethylpyrazine, a potent musty compound from wine corks

The compound responsible for a "fungal must" taint evident in industry assessments of wine corks was identified as 2-methoxy-3,5-dimethylpyrazine. The identification was made on the basis of gas chromatography/odor analyses, collection of material using micropreparative techniques, determination of chemical properties of collected material, and comparison by gas chromatography/mass spectrometry with an authentic sample, synthesized from 2-hydroxy-3,5-dimethylpyrazine. 2-Methoxy-3,5-dimethylpyrazine is an extremely potent compound with an unpleasant, musty, moldy aroma and an aroma threshold in a white wine of 2.1 ng/L. While its contribution to the frequency and intensity of cork taint in bottled wine is yet to be established, it has been assessed by some wine industry personnel as second only to 2,4,6-trichloroanisole as a cause of cork taint in Australian wine.