Survey and risk assessment of trace elements in foods from Taiwan containing red mould rice (Monascus) by ICP-MS.

The concentrations of seven trace elements (As, Cd, Cr, Pb, Se, Cu and Zn) in 93 red mould rice (Monascus) food samples in Taipei, Taiwan, were determined by inductively coupled plasma-mass spectrometry (ICP-MS) after wet digestion. The results, calculated in mg kg(-1) (wet weight) for each sample, revealed the general scenario of food safety in Taiwan: As (0.005-12.04), Cd (<0.0005-2.22), Cr (0.014-6.95), Cu (0.012-8.70), Pb (0.001-0.64), Se (<0.001-1.29) and Zn (0.020-67.02). Three food samples were identified with As concentrations higher than regulatory limits: a dietary supplement sample and a seaweed sample with As concentrations that exceeded the limit of Taiwan's health food standard of 2 mg kg(-1), and a canned eel sample with an As concentration that exceeded the limit of Canada's fish standard of 3.5 mg kg(-1). This study suggests that the estimated intakes of these seven trace elements from the consumption of foods containing Monascus pose little risk, as the trace element contents in the majority of samples were lower than the permissible/tolerable intakes per week according to the guidelines recommended by the Food and Agricultural Organization/World Health Organization (FAO/WHO). Moreover, their concentrations in foods containing Monascus differ widely for different food varieties, suggesting that external contaminants and raw materials are the main sources of trace elements. This study shows that ICP-MS is a simple method proposed for the determination of As, Cd, Cr, Pb, Se, Cu, and Zn in foods containing Monascus.

Survey of total mercury in foods from Taiwan containing red mould rice (Monascus) using a direct mercury analyser (DMA).

Total mercury concentrations in 69 red mould rice (Monascus) food samples purchased in Taipei, Taiwan, were determined using the direct mercury analyser (DMA) method. The highest mean levels of total mercury in these samples were observed in samples of canned roast eel (20 µg kg(-1)), soy fibrous product (14 µg kg(-1)), red mould rice (8.5 µg kg(-1)), cereal (7.6 µg kg(-1)), dried pork fibre (7.5 µg kg(-1)), and dietary supplement (7.2 µg kg(-1)). All samples analysed had mercury levels below the limit of 50 µg kg(-1) for food standards in rice, edible oil, and fat of Taiwan. The mercury concentration in the Monascus foods differed widely between different food varieties, suggesting that external contamination and raw materials are the main sources of mercury. This study shows that DMA is a simple method proposed for the determination of total mercury in foods containing Monascus. The method requires no sample pre-treatment, and it minimizes potential sources of contamination. The data (42±2 µg kg(-1)) obtained from five analyses of a standard reference material (apple leaves, NIST-1515) showed good agreement with the certified reference value (44±4 µg kg(-1)) provided by the US National Institute of Standards and Technology (NIST). The precision based on the analysis of standard reference material was 4.1%; the average recovery was 95%.

Simultaneous determination of sweeteners and preservatives in preserved fruits by micellar electrokinetic capillary chromatography.

A micellar electrokinetic capillary method for the simultaneous determination of the sweeteners dulcin, aspartame, saccharin, and acesulfame-K and the preservatives sorbic acid; benzoic acid; sodium dehydroacetate; and methyl-, ethyl-, propyl-, isopropyl-, butyl-, and isobutyl-p-hydroxybenzoate in preserved fruits is developed. These additives are ion-paired and extracted using sonication followed by solid-phase extraction from the sample. Separation is achieved using a 57-cm fused-silica capillary with a buffer comprised of 0.05 M sodium deoxycholate, 0.02 M borate-phosphate buffer (pH 8.6), and 5% acetonitrile, and the wavelength for detection is 214 nm. The average recovery rate for all sweeteners and preservatives is approximately 90% with good reproducibility, and the detection limits range from 10 to 25 microg/g. Fifty preserved fruit samples are analyzed for the content of sweeteners and preservatives. The sweeteners found in 28 samples was aspartame (0.17-11.59 g/kg) or saccharin (0.09-5.64 g/kg). Benzoic acid (0.02-1.72 g/kg) and sorbic acid (0.27-1.15 g/kg) were found as preservatives in 29 samples.

Analysis of patulin in apple juice by diphasic dialysis extraction with in situ acylation and mass spectrometric determination.

A procedure combining diphasic dialysis extraction with in situ acylation and gas chromatography/mass spectrometry (GC/MS) determination was developed for detection and quantification of the mycotoxin patulin in apple juice. Apple juice samples spiked with 4-N,N-dimethylaminopyridine were dialyzed using methane chloride and acetic anhydride inside dialysis tubing. Patulin was derivatized into its acetate and collected in the tubing after diphasic dialysis and was directly determined using GC/MS with the selective ion monitoring mode without further concentration and cleanup steps. Quantification was carried out by a calibration curve with an internal standard of correlation. The appropriate parameters of both dialysis and derivatization were examined. The linear range of the calibration curve was found to be 10-250 microg/L for patulin, and the limit of quantification was 10 microg/L. Levels of patulin ranging from 0 to 107.2 microg/L with 77-109% recovery were found in 10 apple samples. The technique combining diphasic dialysis extraction and acylation was demonstrated and showed potential for other applications.

The interaction between Bacillus subtilis sigma-A (sigma A) factor and RNA polymerase with promoters.

The P2 promoter from Bacillus subtilis sigma-A (sigma A) operon and the strong phi 29 phage G3b promoter were used to study their interactions with free sigma A and with RNA polymerase holoenzymes (E sigma A and E sigma 70). No binding of free sigma A to the tested promoters was observed, suggesting that the B subtilis free sigma A does not bind promoter by itself for the initiation of RNA transcription. Different footprints of B subtilis RNA polymerase holoenzyme (E sigma A) on the P2 and G3b promoters were detected. The footprint on the P2 promoter is mainly in the -10 downstream region of the bottom strand (noncoding strand) DNA and limited on the top strand (coding strand), whereas the footprints on both strands of the G3b promoter are very clear. These results suggest that the footprint regions of RNA polymerase on a promoter and the strength of its binding to the promoter depend on the properties of the specific promoter DNA sequence. It also suggests that the -10 and its downstream regions are more important than the -35 region for the formation of the E sigma A-P2 promoter open complex. Footprints of B subtilis E sigma A and E coli E sigma 70 on the same G3b promoter are very similar on the top strand but different on the bottom strand, with the footprint being about 17 bases wider (-4 to +13) in the case of E coli E sigma 70. Since this region contains most of the bases involved in promoter DNA melting, we suggest that E coli and B subtilis RNA polymerases have different efficiency in forming the open complex with heterologous promoter DNA during initiation of transcription.

Purification and some characteristics of a calcium-binding protein from Bacillus cereus spores.

A novel calcium-binding protein has been purified from the dormant spores of Bacillus cereus T. Purity of this protein was verified by SDS-PAGE and reversed-phase HPLC. Its calcium-binding ability was verified by a competitive calcium-binding assay using Chelex-100 resin and 45Ca autoradiography. The protein is heat-stable and is retained by hydrophobic matrices (phenyl-Sepharose) in a calcium-dependent manner. SDS-PAGE and amino acid composition indicate the molecular mass of the protein to be 24 kDa.