IEC61850-9-2数据收发测试的探索

WinPcap网络开发包是一个免费的、基于Windows平台的、直接在链路层捕获和发送网络数据包的工具,文中设计了基于WinPcap的IEC 61850-9-2仿真测试软件。介绍了WinPcap软件包、IEC 61850-9-2的报文格式以及在数字化变电站中使用和自动化测试实际情况。通过MAC嗅探模块、CID文件读取模块、SNTP对时模块、IEC61850-9-2报文发送和接受模块的设计,该仿真测试软件在计算机WINDOWS环境下网卡介质上能够直接发送符合数字化变电站装置要求的IEC 61850-9-2报文与数字化变电站设备进行联调,并且能够接受IEC 61850-9-2报文进行自动化分析。提出了在发送过程中pcap_sendqueue_transmit函数和在接受过程中微秒定时器的重要作用。     

Combination of nisin and ε-polylysine with chitosan coating inhibits the white blush of fresh-cut carrots

Effects of the combination of nisin and ε-polylysine with chitosan coating on quality maintenance and white blush inhibition were investigated in fresh-cut carrots. Fresh-cut carrots were treated with 1% lactic acid solution (v/v), 1% chitosan solution (w/v), or 1% chitosan solution containing 64 μg/mL nisin and 250 μg/mL ε-polylysine (LA + CH + Nisin + ε-PL). The samples were packed in polyethylene plastic bags and stored at 4 °C for 9 days. Changes in sensory attributes, physicochemical indices, respiration rate, microbiological counts and white blush were measured. Results showed that LA + CH + Nisin + ε-PL significantly (P < 0.05) inhibited respiration rate, decline of ascorbic acid and growth of microorganism (yeast and mold, total viable counts, total coliforms counts, Staphylococcus aureus and Pseudomonas spp.), and increased total phenol content and phenylalanine ammonialyse (PAL) activity compared with the control after 9-day storage. It was also strongly effective in inhibiting the white blush of fresh-cut carrots. Furthermore, LA + CH + Nisin + ε-PL significantly (P < 0.05) reduced the lignin synthesis in fresh-cut carrots by inhibiting the cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL) activity, as well as Dc4CL and DcC4H gene expression. Our results may provide some basis for the use of the combination of nisin and ε-polylysine with chitosan coating as an alternative preservation method for fresh-cut carrots.     

Vegetable oil as fat replacer inhibits formation of heterocyclic amines and polycyclic aromatic hydrocarbons in reduced fat pork patties

Formation of heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) was examined to evaluate the impact of using vegetable oil as fat replacement on carcinogen formation in meat product. Pork patties were formulated with 40% fat replacement by olive oil, sunflower oil or grape seed oil, respectively and cooked at 180 °C or 220 °C. Control patties contained the highest amount of HCAs compared with all other patties at both temperatures. Olive oil and sunflower oil replacement completely inhibited formation of MeIQ (2-amino-3, 4-dimethylimidazo[4,5-f]quinoline), while grape seed oil completely inhibited MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline), 4,8-DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) in patties. Grape seed oil achieved the highest inhibition capacity compared with sunflower oil and olive oil. HCAs increased significantly with cooking temperature (p < 0.05), but no difference was observed in total PAHs for patties cooked at different temperature (p > 0.05). In conclusion, fat replacement with sunflower oil, olive oil or grape seed oil in pork patties could reduce the formation of HCAs without compromising eating quality.     

Histamine reduction by Maillard reaction with glucose

Histamine, well known as a toxic biogenic amine, is found in a variety of foods. Reducing its concentration and toxicity is desirable. In this study, the glucose/histamine Maillard reaction was proposed as a novel tool for histamine control. Effects of temperature, heating time, initial pH value, NaCl concentration, initial histamine concentration and initial glucose concentration on percentage removal of histamine in the glucose/histamine Maillard reaction model were investigated. The results showed that histamine reduction was affected by these variables, and could be almost eliminated under appropriate conditions. Fluorescence intensity and ultraviolet–visible spectroscopy analyses were used to characterize the glucose/histamine Maillard reaction. Cytotoxicity assay revealed that the glucose/histamine Maillard reaction significantly reduced the toxicity of histamine (P < 0.05). Furthermore, histamine concentrations in canned tuna samples were significantly reduced by thermal treatment with glucose (P < 0.05). This study demonstrates that the glucose/histamine Maillard reaction is a promising method for histamine control.     

Effects of Salmonella bacteriophage,nisin and potassium sorbate and their combination on safety and shelf life of fresh chilled pork

Salmonella is an important foodborne pathogen and a serious threat to human health worldwide. This study was to reduce Salmonella and the spoilage bacteria on fresh chilled pork using bacteriophage, nisin, and potassium sorbate (PS) along with their combinations. Microbial, chemical, and sensory qualities of the fresh chilled pork (artificially contaminated with Salmonella 3 log CFU/g) treated with bacteriophage (9 log PFU/g), nisin (5000 IU/g), PS (2 mg/g) and their combinations were evaluated. The result showed that all the samples treated with phage could significantly (P < 0.05) reduce Salmonella population on fresh chilled pork. The combination treatment of nisin, PS and phage (N-PS-P) could significantly lower total viable counts (TVC), TVB-N and TBARS of the chilled pork during the storage period. The TVC of sample treated by N-PS-P was reduced by 2.3 log CFU/g at 7th day. It was also found through the electronic nose detection that the N-PS-P treatment was able to significantly reduce odour and maintain good sensory of the chilled pork. Hence, the N-PS-P treatment extended the shelf life of fresh chilled pork up to 14 days. No adverse effect of the phage on the chilled pork was observed. In conclusion, this study suggests that the phage and its combination with nisin and PS have great potential to be used as a good preservative for fresh chilled pork.     

Latex bead and colloidal gold applied in a multiplex immunochromatographic assay for high-throughput detection of three classes of antibiotic residues in milk

Two rapid and sensitive high-throughput immunochromatographic assays were successfully developed for simultaneous determination of 12 sulfonamide, 18 quinolone and six tetracycline residues in milk. Under optimized conditions, residues from these three classes of antibiotics can be qualitatively and quantitatively determined on a single strip within 10 min. The detection limits were much lower than the maximum residue limits established by the European Union. Comparative evaluations of sensitivity, antibody consumption, coefficient of variation and user experience between these two immunochromatographic assays showed that latex beads have advantages over colloidal gold when employed as a label in the assay. Therefore, the latex bead-based high-throughput immunochromatographic assay has the best potential for on-site testing of a large number of samples as part of food safety applications.     

The incidence and distribution of ochratoxin A in Daqu,a Chinese traditional fermentation starter

Daqu, a traditional starter culture mainly used to produce Chinese liquor and vinegar, is spontaneously fermented by diverse bacteria, yeasts and filamentous fungi under thermophilic condition. Therefore, mycotoxins may exist in Daqu, resulting in the contamination of end-foods. Ochratoxin A (OTA), a mycotoxin produced by certain species of Aspergillus and Penicillium, is not known whether existing in Daqu. However, specific method to detect OTA as well as OTA occurrence in Daqu has not been reported so far. With this in mind, a new method was developed to detect OTA in Daqu by the combination of ultrasound-assisted solid-liquid extraction (USLE), solid phase extraction (SPE) cleanup and UPLC-MS/MS. The USLE conditions of OTA from Daqu were optimized using Plackett-Burman (PB) design coupled with Box-Behnken (BB) design. Under the optimized conditions, no matrix effects were found, and the external standard method can be used to determine OTA in Daqu. The recoveries for spiked samples were 87–106% with the relative standard deviations (RSD) < 15%. The limits of detection and quantification were respectively 0.33 and 0.41 ppb. This approach was then applied to analyze 133 Daqu samples from different geographical regions in China, including 26 low temperature-, 33 medium temperature- and 74 high temperature-type Daqu. The results showed that OTA was detected in 66 samples with a maximum concentration of 28.87 ppb in low temperature Daqu, and the OTA incidence was on increase in the order of high temperature-, medium temperature- and low temperature-type Daqu. This implied that fermentation temperature is the key factor influencing OTA occurrence in Daqu. Moreover, there may be some fungi possessing the biosynthesis ability of OTA under high temperature environment (more than 45 °C).     

Combination treatment of ohmic heating with various essential oil components for inactivation of food-borne pathogens in buffered peptone water and salsa

Consumer preference for minimally processed foods has steadily increased for several years, while foodborne outbreaks from under-processed foods continue to be reported worldwide. We investigated the combination effect of ohmic heating with various essential oil components for inactivation of foodborne pathogens in buffered peptone water and salsa. We choose carvone, eugenol, thymol, and citral to combine with ohmic heating, which are registered for use as flavorings in foodstuffs. Combination treatment of ohmic heating with citral showed the most synergistic bactericidal effect against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in buffered peptone water followed by thymol, eugenol, and carvone. When enumerated on selective media, the reductions were 4.8, 5.7, and 4.3 log CFU/ml for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively. Cell membrane destruction by combination treatment and the loss of cell membrane potential by essential oil components were proposed as the bactericidal mechanism. When applied in salsa, inactivation of bacterial pathogens was the greatest with the ohmic and thymol combination treatment followed by citral, eugenol, and carvone. A synergistic virucidal effect was observed for MS -2 bacteriophage, which was used as a norovirus surrogate. Color (b* values) of salsa were improved by combination treatment of ohmic heating and thymol compared to ohmic treated samples. Therefore, the combination treatment of ohmic heating and thymol could be used effectively to pasteurize salsa.     

Effect of sulfur dioxide and ethanol concentration on fungal profile and ochratoxin a production by Aspergillus carbonarius during wine making

Fungal profiles and ochratoxin A (OTA) accumulation during wine making were investigated using five different wine grape cultivars, Cabernet Sauvignon, Pinot Noir, Merlot, Syrah and Petit Verdot and the intrinsic influences caused by sulfur dioxide, ethanol and combine effect of ethanol and reducing sugar were analyzed using Cabernet Sauvignon and inoculation of Aspergillus carbonarius. Aspergillus spp. and Penicillium spp. were found as the major fungi in all winemaking processes and were highly correlated with OTA accumulation in wine. Most fungi died and OTA production decreased after 48 h of alcoholic fermentation, being consistent with the period when ethanol accumulation increased. The addition of SO₂ significantly inhibited the growth and OTA production of A. carbonarius with complete inhibition at 500 mg/L. When the ethanol concentration in the must increased to the range of 2–4%, growth and OTA production of A. carbonarius were significantly inhibited. Reducing sugar concentration had no significant effect on the growth and OTA production of A. carbonarius within the levels changing during the winemaking. Therefore, the increase of ethanol concentration played an important role in causing the decrease of fungal contamination and OTA accumulation during winemaking.     

Estimated daily intake of organochlorine pesticides from dairy products in Brazil

The estimated daily intake (EDI) of organochlorine (OC) pesticides (HCB, α-HCH, lindane, aldrin, p,p′-DDE, p,p′-DDD, and o,p′-DDT) through consumption of dairy products from Rio Grande do Sul State (Brazil) was investigated. Fluid milk and cheese had similar ΣOC levels (26.04 and 26.14 ng g⁻¹ fat, respectively), whereas milk powder had lower levels (2.23 ng g⁻¹ fat). OC levels in UHT milk exhibited a declining trend over time (ΣOC = 27.70 ng g⁻¹ fat in 2000 vs. 1.50 ng g⁻¹ fat in 2009/2010). The EDI of OC pesticides was remarkably higher for children (8.266 ng kg⁻¹ day⁻¹) than for adolescents, adults, and the elderly (ranging from 0.393 ng kg⁻¹ day⁻¹ to 0.614 ng kg⁻¹ day⁻¹). The average EDIs for OC pesticides were below the acceptable daily intakes (ADI), with the exception of aldrin, which greatly exceeded the ADI for children. In addition, some samples (8.8%) exceeded the maximum residue limit for the compounds evaluated.