Incidence of citrinin in red yeast rice and various commercial Monascus products in Taiwan from 2009 to 2012

Red yeast rice, produced by the fermentation of red yeast (Monascus purpureus) with white rice, has long been used in food colouring and meat preservation in Asia. Recently, powdered red yeast rice and its formulated products, used worldwide as dietary supplements, have the ability of reducing blood-lipid levels in humans. However, some Monascus strains could produce the mycotoxin citrinin as a secondary toxic metabolite so that commercial Monascus products are of a serious concern to the public now. The aim of this study was to obtain information about the occurrence of citrinin in red yeast rice and various commercial Monascus products in Taiwan from 2009 to 2012. A simple and rapid HPLC-fluorescence method was developed to detect citrinin in red yeast rice and Monascus products. The method's performance was acceptable in terms of recoveries, which ranged from 81.2% to 94.3% for citrinin-spiked samples at levels of 0.1, 1 and 10 mg/kg, and the relative standard deviation ranged from 2.5% to 5.7%. The limit of quantification of 0.05 mg/kg was achieved. The survey results showed that among total 302 samples, the incidences of citrinin contamination were 69.0%, 35.1% and 5.7% for red yeast rice (raw material), dietary supplements and red yeast rice processed products, respectively. The mean contamination levels were 13.3, 1.2 and 0.1 mg/kg for red yeast rice (raw material), dietary supplements and red yeast rice processed products, respectively. Such high citrinin contamination rate and level is worthy of note.     

Characterisation of zero‐trans margarine fats produced from camellia seed oil,palm stearin and coconut oil using enzymatic interesterification strategy

Zero‐trans interesterified fats were produced from camellia seed oil (CSO), palm stearin (PS) and coconut oil (CO) with three weight ratios (CSO/PS/CO, 50:50:10, 40:60:10 and 30:70:10) using Lipozyme TL IM. Results showed that the interesterified products contained palmitic acid (34.28–42.96%), stearic acid (3.96–4.72%), oleic acid (38.73–47.95%), linoleic acid (5.92–6.36%) and total medium‐chain fatty acids (MCFA)s (∑MCFAs, 5.03–5.50%). Compared with physical blends, triacylglycerols of OOO and PPP were decreased and formed new peaks of equivalent carbon number (ECN) 44 in the interesterified products. The product CPC3′ showed a slip melting point of 36.8 °C and a wide plastic range of solid fat content (SFC) (45.8–0.4%) at 20–40 °C. Also, the major β′ form was determined. These data indicated that the zero‐trans interesterified fats would have a potential functionality for margarine fats. Subsequently, the antioxidative stabilities of interesterified products with the addition of α‐tocopherol (α‐TOH) and ascorbyl palmitate (AP) were investigated. The results indicated that AP had a dose‐dependent effect at concentrations of 100, 200 and 400 ppm.     

求解旅行商问题的多样化搜索帝国竞争算法

帝国竞争算法是一种局部搜索能力较强的群智能优化算法，但过度的局部搜索会导致多样性丢失并陷入局部最优。针对这一问题提出基于多样化搜索的帝国竞争算法（MSSICA）。将国家定义为一条可行解，将王国定义成四种特性不同的组合人造解方式。在搜索时使用区块机制保留各自的优势解片段，并对不同的帝国使用差异化的组合人造解方式以搜索不同解空间的有效可行解信息。在陷入局部最优时，使用多样化搜索策略注入均匀分布的可行解替换较无优势的解以提升多样性。实验结果显示，多样化搜索策略可以有效地改善帝国算法的求解多样性，并提升求解质量与稳定性。     

A simple and sensitive aptasensor with rolling circle amplification for viable Cronobacter sakazakii detection in powdered infant formula

Cronobacter sakazakii is a foodborne, emerging opportunistic pathogen that causes severe bacteremia, necrotizing enterocolitis, and sepsis with a mortality rate of up to 80%. In this study, we developed a simple and sensitive fluorescent turn-off aptasensor with rolling circle amplification assay for viable C. sakazakii detection in powdered infant formula. The results showed that the proposed aptasensor has good performance and specificity for detecting viable C. sakazakii in pure culture and powdered infant formula samples within 3 h. Under the optimal reaction conditions, there is a linear relationship between fluorescent intensity at 490 nm and logarithmic concentration of C. sakazakii in the range of 2.7 × 10⁵ to 2.7 × 10² cfu/mL, with a limit of detection of 2.7 × 10² cfu/mL in pure culture. The proposed aptasensor achieved a recovery of 104 to 111% in pure culture, and 96 to 107% in spiked powdered infant formula samples. The proposed aptasensor does not require complicated DNA extraction steps or antibodies, and can be performed at 37°C, making it a convenient and sensitive strategy for C. sakazakii detection.     

A modified lateral flow immunoassay for the detection of trace aflatoxin M1 based on immunomagnetic nanobeads with different antibody concentrations

A modified lateral flow immunoassay (two-step assay) was developed to detect trace aflatoxin M1 (AFM1) in raw milk. In contrast to conventional LFIA, two kinds of immunomagnetic nanobeads (IMNBs) were used. One IMNB with high antibody concentration was used to capture AFM1 in the test sample, whereas the other IMNB with low antibody concentration was used to elucidate the results of the test. Critical factors, such as antibody concentration of IMNBs and size of IMNBs, were investigated. The two-step assay exhibited an ideal sensitivity to screen trace AFM1 in milk samples without extra sample pretreatment. The cutoff value of the naked eye was 0.02 μg/L and satisfied the European Union's maximum limit of AFM1 in raw milk, heat-treated milk, and milk used to manufacture milk-based products and even in baby foods. With the same antibody, sensitivity was enhanced approximately 25 and 50 times when compared with conventional IMNB-based LFIA and gold-based LFIA, respectively. Corresponding results of 13 raw milk samples were obtained between this two-step assay and referenced enzyme-linked immunosorbent assay.     

Enzymatic synthesis of medium‐ and long‐chain triacylglycerols–enriched structured lipid from Cinnamomum camphora seed oil and camellia oil by Lipozyme RM IM

Medium‐ and long‐chain triacylglycerols (MLCTs)–enriched structured lipid (SL) was synthesised through enzymatic interesterification from Cinnamomum camphora seed oil (CCSO) and camellia oil (CO) using Lipozyme RM IM from Rhizomucor miehei as a biocatalyst. Effects of different reaction conditions including substrate molar ratio, reaction time and reaction temperature were investigated. Results showed that 55.81% of total MLCT species (CCO/LaCL, LaCO/LCL, COO/OCO and LaOO/OLaO) was obtained in the interesterified product under the optimal conditions of substrate molar ratio of 1:1.5 (CCSO/CO) at 60 °C for 3 h. Thereafter, fatty acid profiles, tocopherol contents and physiochemical characteristics of the interesterified product and physical blend were comparatively investigated. The fatty acid composition of the interesterified product consisted of capric acid (26.33%), lauric acid (21.29%) and oleic acid (42.33%). It should be mentioned that the interesterified product contained predominantly oleic acid (88.69%) at Sn‐2 position, while MCFAs (68.05%) at Sn‐1,3 positions. Compared with physical blend, the reduction in tocopherol contents and changes of physiochemical characteristics occurred in SL. The smoke point of the interesterified product was much higher than that of the physical blend, which meant that such MLCTs‐enriched SL could be better for cooking purpose.     

Comparison of NIR and MIR spectroscopic methods for determination of individual sugars,organic acids and carotenoids in passion fruit

In this work, NIR and MIR spectroscopy was investigated and compared for predicting passion fruit ripening parameters as sugars, organic acids and carotenoids. Spectra of 56 samples of the lyophilized passion fruit were collected using an integrating sphere in NIR range and attenuated total reflectance accessory in MIR range. Individual sugars (sucrose, glucose and fructose), organic acids (malic and citric acids) and carotenoids (β-carotene) contents were determined by reference methods. Spectral and reference data were analyzed by principal component analysis. Partial least square regression (PLSR) was used to establish calibration models. MIR technique was better than the NIR technique for glucose (R²_v = 0.942), fructose (R²_v = 0.855), sucrose (R²_v = 0.818), total sugar (R²_v = 0.914) and citric acid (R²_v = 0.913) content determination. On the other hand, NIR was superior for total acids (R²_v = 0.903) content determination. For malic acid and β-carotene contents both methods were unsatisfactory due to low concentrations of these constituents in the passion fruits.     

Substratum attachment location and biofilm formation by Bacillus cereus strains isolated from different sources: Effect on total biomass production and sporulation in different growth conditions

Bacillus cereus, an endospore forming human pathogen associated with foodborne diseases, can form biofilms and attach to surfaces of processing equipment in the food industry. It is a consistent source of contamination and/or cross contamination of processed food products. The objective of this study was to understand substratum attachment location and biofilm formation behavior of B. cereus strains under different growth conditions. A total of 60 strains isolated from food, human, or farm and a number of reference strains were used in this study. Substratum attachment locations of these strains in 96-well microtiter plates were highly diversified among these strains. Strains isolated from food showed higher preference to attach at the air-liquid interface during early stage of biofilm formation. To the best of our knowledge, this is the first report showing the level of substratum attachment location and biofilm formation of B. cereus strains isolated from different sources. Substratum properties did not affect biofilm formation location when a number of selected strains were grown on stainless steel coupon, indicating that biofilm formation location might be independent of the type of substratum. Substratum attachment location and biofilm formation related phenotypes such as total biomass production, number of sessile cells, and sporulation were closely correlated. Substratum attachment location and sporulation behavior were strongly affected during biofilm formation under nutrient stress condition. The number of spores was significantly increased in biofilms grown under nutrient stress condition even though total biomass formation was lower. Our results on substratum attachment location and related biofilm formation behavior are substantially important for food industries where different surfaces are prone to B. cereus attachment, particularly for setting up and implementing clean in place (CIP) protocols.     

GaN材料的高速生长对其C污染以及光致发光光谱的影响

利用金属有机化学气相沉积对GaN的高速生长进行了研究.结果表明,随着GaN生长速率的提高,其非故意掺杂的C含量也在提高,并且呈现出良好的线性关系.当生长速率由2μm/h增加至7.2μm/h时,利用SIMS测量发现其GaN中的C含量由2.9×1017增加至5.7×1018 cm-3 .研究表明,N空位的存在与C浓度之间存在紧密的联系。在高氨气分压生长条件下,N空位的浓度也在急剧下降。此时,与具有相近生长速率的常规样品相比,其C含量几乎下降了一个数量级。.光致发光光谱表明,黄带以及蓝带的强度与C污染存在线性关系.这个结果也证实了与C相关的缺陷是导致黄带以及蓝带发光的主要来源。     

A reliable and sensitive time-resolved fluorescent immunochromatographic assay (TRFICA) for ochratoxin A in agro-products

Immunochromatographic assays (ICAs) are considered as a suitable diagnostic tool for the detection of mycotoxins. Mycotoxins and especially, ochratoxin A are analytes with more demanding sensitivity requirements. To enhance the sensitivity of current immunochromatographic assays for ochratoxin A (OTA), a novel sensitive ICA was developed in this study. In the assay, microspheres enclosing fluorescent europium (III) [Eu(III)] nanoparticles (EuNPs) were used as a label for OTA monoclonal antibody (OTA-mAb) conjugation. Accordingly, assay was called time-resolved fluorescent immunochromatographic assay (TRFICA). The test strip was composed of three parts: a sample pad, nitrocellulose membrane and an absorbent pad. As for detection, a proper concentration of conjugated microspheres was pipetted into the microtube and sample extract was added to it. Then the strip was inserted into the tube and the fluid flow along the strip. The TRFICA results were obtained in 8 min and read by a portable TRFICA strip reader. The established method allows quantitative determination of OTA with limit of detection as low as 1.0 μg kg⁻¹ in the samples. For validation, spiked samples including wheat, maize, soybean and rice were respectively assayed by TRFICA and a standard high performance liquid chromatography equipped with a fluorescence detector (HPLC-FLD), and good agreement of results was obtained between two methods.