食品添加剂—红曲米(粉)中色价的不确定度评定

以GB 4926-2008规定的方法,建立不确定度的数学模型,系统分析、计算不确定度各分量,充分分析了操作过程中的不确定来源,较为全面地评定了红曲米粉中色价测量过程的不确定度.建立了一种简单、实用的测定食品添加剂中色价的不确定度评定方法.     

Ethyl carbamate formation regulated by ornithine transcarbamylase and urea metabolism in the processing of Chinese yellow rice wine

Ethyl carbamate (EC) is a potential carcinogenic compound present in most of the fermented foods. In this work, EC was inhibited through different strategies during vinification of Chinese yellow rice wine. EC can be inhibited by the use of ornithine in contrast to the control at peak point. However, the utilisation of urease resulted in little inhibitive effect on EC. The comparative data of intracellular ornithine transcarbamylase (OTCase) and arginine deiminase (ADI) among four experiments showed that EC was positively regulated by intracellular OTCase, but ADI was not determined. Extracellular urea and citrulline content was significantly increased by adding ornithine (P < 0.05), whereas ethanol played a minor role in EC formation. The correlation analysis between EC and OTCase or urea revealed a linear association (correlation coefficients above 0.8). These findings suggested that OTCase may be a required factor regulating EC formation during the brewing of Chinese yellow rice wine.     

Modeling Growth Rate and Assessing Aflatoxins Production by Aspergillus flavus as a Function of Water Activity and Temperature on Polished and Brown Rice

Abstract: The aim of this study was to model the radial growth rate and to assess aflatoxin production by Aspergillus flavus as a function of water activity (a_w 0.82 to 0.92) and temperature (12 to 42 °C) on polished and brown rice. The growth of the fungi, expressed as colony diameter (mm) was measured daily, and the aflatoxins were analyzed using HPLC with a fluorescence detector. The growth rates were estimated using the primary model of Baranyi, which describes the change in colony radius as a function of time. Total of 2 secondary models were used to describe the combined effects of a_w and temperature on the growth rates. The models were validated using independent experimental data. Linear Arrhenius–Davey model proved to be the best predictor of A. flavus growth rates on polished and brown rice followed by polynomial model. The estimated optimal growth temperature was around 30 °C. A. flavus growth and aflatoxins were not detected at 0.82 a_w on polished rice while growth and aflatoxins were detected at this a_w between 25 and 35 °C on brown rice. The highest amounts of toxins were formed at the highest a_w values (0.90 to 0.92) at a temperature of 20 °C after 21 d of incubation on both types of rice. Nevertheless, the consistencies of toxin production within a wider range of a_w values occurred between 25 to 30 °C. Brown rice seems to support A. flavus growth and aflatoxin production more than the polished rice. Practical Application: The developed models can be used to estimate to what extent the change in grain ecosystem conditions affect the storage stability and safety of grains without the need for running long‐standing storage study. By monitoring the intergranular relative humidity and temperature at different locations in the storage facility and inputting these data into the models, it is directly possible to assess either the conditions are conductive for the growth of A. flavus or aflatoxin production.     

Dynamic changes of the content of biogenic amines in Chinese rice wine during the brewing process

This study examined the biogenic amine content of the brewing raw material (wheat Qu, seed starter, mash or liquid) during fermentation and during the maturation and storage process. Pre‐column derivatization and high‐performance liquid chromatography were employed to analyse the dynamic changes in biogenic amines during the Chinese rice wine brewing process. Some aliphatic amines (putrescine, cadaverine, spermine) were already found to be present in the glutinous rice and wheat Qu, but the content was below 2.88 mg/kg. None of the amines were detected in the brewing water. The biogenic amine content in the seed starter exhibited a large variation range (16.43–87.72 mg/L), which could influence the total content of biogenic amines prior to fermentation. A much more obvious increase in biogenic amines stemmed from the fermentation process, with the presence of a biogenic amine‐producing bacteria and precursor amino amines. In the first 2 days, the biogenic amine content increased sharply, followed by a slow increase over the next 4 days, and the content reached a maximum value on day 6; subsequently there was a decrease or fluctuation in the concentration. After clarification and cooking, the biogenic amine content increased significantly; however, a slight decrease was observed during storage, especially for putrescine and histamine. Putrescine and tyramine were the most prevalent amines in all of the samples. Overall, the content of biogenic amines was found to be within the safe level for human health, ranging from 54.52 to 146. 35 mg/L. Copyright © 2013 The Institute of Brewing & Distilling     

Mycotoxins,trace elements,and phthalates in marketed rice of different origin and exposure assessment

ABSTRACT

The aim of this study was to determine levels of 11 mycotoxins, 10 trace elements, and 6 phthalates in rice samples from Serbian and Chinese market. Mycotoxins were not detected in any of the analysed rice samples. Results revealed similar median levels for following elements: Mn, 17.5 and 15.7 mg kg^?1; Fe, 2.47 and 2.12 mg kg^?1; Cu, 1.95 and 1.59 mg kg^?1 in marketed samples from Serbia and China, respectively. Median concentration of Ni in Serbian marketed samples was 1.9 times higher than in Chinese ones. The median levels (µg kg^?1) of phthalates ranged from 1.2 (benzylbutyl phthalate [BBP]) – 566 (di(2-ethyl-hexyl) phthalate [DEHP]) and 1.7 (BBP) – 348 (DEHP) in Serbian and Chinese marketed samples, respectively. The results were used to assess daily exposure of Serbian and Chinese adult consumers. The calculated target hazard quotients indicated that the potential risk attributable to the analysed contaminants in rice samples should not be of concern neither for the Serbian nor the Chinese consumers.     

Comparison of extraction solvents and conditions for herbicide residues in milled rice with liquid chromatography-diode array detection analysis (LC-DAD)

Different extraction procedures and clean-up methods were compared in order to develop a sample preparation procedure for the multi-residue analysis of six post-emergence herbicides (metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium and cyhalofop butyl) in rice grains followed by liquid chromatography-diode array detection (LC-DAD). Optimum results were obtained dispersing milled rice grain in water, followed by the addition of 1% acetic acid in acetonitrile, MgSO₄ and sodium acetate as a modification of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method but no primary and secondary amine (PSA) sorbent was added due to the acidic nature of the herbicides. The method was further expanded to other post-emergence herbicides (quinclorac, clomazone and propanil). Except for quinclorac, which cannot be analysed with this method, the recoveries of the other eight herbicides were in the range 73–111%, with relative standard deviations lower than 12%. Limits of detection (LODs) ranged from 0.03 to 0.08 mg kg^?1. A single analyst can extract twelve samples in 4 h. The method presented here allows the simultaneous residue determination of the most common post-emergence herbicides employed in cultivating rice. It is simple, rapid, sensitive, and can be applied routinely to polished rice grain herbicide residue analysis.     

Dietary intake of arsenic by children and adults from Jinhu area of China

The aim of this study was to estimate the dietary intake of arsenic (As) by children and adults from Jinhu area of China. A duplicate diet approach was used to collect diet samples in November and December 2007. The As content was measured by hydride generation atomic fluorescence spectrometry. The As intakes (median) for different group were: children: 0.6 µg kg^?1 bw day^?1 or 6.7 µg kg^?1 bw week^?1; adults: 0.5 µg kg ^?1 bw day^?1 or 3.8 µg kg ^?1 bw week^?1, none of which exceeded the provisional tolerable weekly intake (PTWI) of 15 µg kg ^?1 bw week^?1 for As proposed by the World Health Organization (WHO). The median and maximum of the children group amounted to 44.7% and 125.3% of the PTWI; the values for adults were 25.3% and 118.7%, respectively. There were 3.3% of children whose weekly As intake exceeded the PTWI, and there were 6.7% of adults whose weekly As intake exceeded the PTWI. It is concluded that dietary As intake was safe for most people in Jinhu area, but the high dietary As intake for a minority of people in this area deserves attention.     

Survey of aflatoxins in rice from Iran using immunoaffinity column clean-up and HPLC with fluorescence detection

A study was undertaken to determine levels of aflatoxins in rice. A total of 261 rice samples were analyzed by HPLC using a method was based on the extraction of 50?g of finely ground rice plus 5?g?NaCl with 200?ml of 80% methanol. After filtration and immunoaffinity clean-up, 20?µl was injected onto the HPLC. HPLC analysis was carried out using a Genesis RP C₁₈ column (250?×?4.6, 4?µm I.D.) and a mobile phase with a linear gradient of water/methanol/acetonitrile (6?:?2?:?2?v/v) over 16?min. Aflatoxins were determined after post-column derivatisation with iodine by fluorescence detection at excitation and emission wavelengths of 365 and 445?nm, respectively. It was found that 68.9% of the rice samples contained aflatoxin B₁ at levels greater than 0.2?ng?g^?1.