超声强化苯甲醛接枝壳聚糖的缩合反应

壳聚糖希夫碱具有优良的金属离子螯合能力,但传统方法制备的反应时间长,缩合率不高。为了缩短制备的时间和提高缩合率．本文引入超声场来强化该缩合反应,并通过正交设计实验优化反应条件．超声辅助反应的缩合度为92．99％,比传统方法提高了19．03％;超声辅助制备的优化条件为：反应物配比（n苯甲醛：n壳聚糖）为6,超声功率为180kw,超声处理时间为4h,反应温度为70℃,反应溶液pH为5．     

Self-assembled silver nanoprisms monolayers at the liquid/liquid interface

A crown ether derivative (4′-aminobenzo-15-crown-5 hydrotetrafluoroborate) can mediate the self-assembly of silver nanoprisms at the liquid/liquid interface in the form of a stable hybrid nanocomposite film. The metallic luster of the interfacial film results from the electronic coupling of Ag nanoprisms, suggesting the formation of closely packed nanoprism thin films. The interfacial film of nanoprisms could be transferred to solid substrates as a Langmuir–Blodgett film. The properties of films were studied by UV–vis spectroscopy and transmission electron microscopy.     

Controlling Salmonella infections in pig farms: A framework modelling approach

Human salmonellosis is an important food-borne disease and S. Typhimurium is the most common serotype attributed to pork products. Under a farm-to-fork strategy, reducing the levels of Salmonella-positive pigs entering the slaughterhouse is an important goal. A framework model was developed, where the effect of dynamic (infection characteristics) and non-dynamic (cleanness and disinfection, biosecurity measures, etc.) factors were considered. Four baseline scenarios were created, corresponding to different levels associated with national Salmonella monitoring programs, and sensitivity analyses were run for the non-dynamic factors. Moreover, the option of vaccination was incorporated into the model, in order to provide with a tool for the formulation of an optimum vaccination strategy depending on the characteristics of the vaccine.     

Validation of the sensitive and accurate quantitation of the fatty acid distribution in bovine milk

A method for the precise analysis of the complex mixture of fatty acids in milk has been developed and validated. The triacylglycerol of nonanoic acid was applied as the internal standard (ISTD) for absolute quantification. Milk lipids were extracted by miniaturised ultrasonication and methylated with trimethylsulfonium hydroxide. Resulting fatty acid methyl esters were determined by gas chromatography with flame ionisation detection giving excellent resolution, including separation of several 18:1 isomers. The low quantitation limit (0.01 mg mL⁻¹ milk) indicates that the sensitivity of the method is sufficient to quantify up to 50 fatty acids, from 4:0 to 23:0. Measurements of precision provided excellent results for different bovine milk samples of different fat content (coefficient of variance: 1.9% and 9.8% for intra- and interday precision, respectively). Recovery averaged 108 ± 3.5%. Evaluation of methods for determining the total fat content showed that gravimetry is no longer needed when using the ISTD.     

Controlled transglutaminase treatment in Edam cheese-making

Transglutaminase (TG) has been widely used in the dairy industry to increase product yield. However, it has not been used in the production of ripened cheeses because of the difficulty of controlling TG activity. It was observed that cross-linking of TG in ultrafiltration retentate could be controlled using a protein standardisation step. TG increased the cheese yield 4%, due to an increase in the moisture content of the cheeses. Traditionally, increased cheese moisture reduces hardness of cheese, but this was not observed in the cheese from TG-treated milk. Furthermore, the organoleptic properties of the TG-cheeses did not differ significantly from those of the control cheeses. No differences were observed in the protein profile of the whey fraction as a result of the TG treatment. The protein standardisation process thus makes it possible to use TG in the production of Edam cheese.     

Screening of adhesive lactobacilli with antagonistic activity against Campylobacter jejuni

In the present study, 78 lactic acid bacteria (LAB) strains were screened for the antagonistic activity against Campylobacter jejuni and 15 LAB strains with high bactericidal capacity were selected for further study through the analysis of the inhibition zone of LAB spent culture supernatant on the growth of C. jejuni. Among these strains, four isolates, Lactobacillus plantarum N8, N9, ZL5 and Lactobacillus casei ZL4 exhibited high adhesion ability to HT-29 cells. All the cell free supernatant (CFS) of these four strains contained high concentration of organic acid and their inhibition effects against C. jejuni were pH sensitive. Furthermore, these four strains could strongly antagonize the adhesion and invasion of C. jejuni to HT-29 cells and showed good tolerance to artificial gastric and small intestinal juices. This study suggests that Lactobacillus strains N8, N9, ZL4 and ZL5 could be used as potential probiotics in food applications against C. jejuni infection.     

Seasonal variation of aflatoxin M1 in raw milk from the Yangtze River Delta region of China

The objective of this study was to evaluate the occurrence of aflatoxin M₁ (AFM₁) in raw milk samples from 18 dairy farms in the Yangtze River Delta region during four different seasons. A total of 72 tank milk samples was collected with 18 samples for each season. Milk AFM₁ was detected using LC-MS/MS. The AFM₁ was detected in 43 milk samples (59.7%) ranging in concentration from 10 to 420 ng/L. The concentration of AFM₁ in raw milk was significantly higher during the winter (123 ng/L) than during other seasons (P < 0.05). There was no significant difference between the spring (29.1 ng/L), summer (31.9 ng/L), and autumn (31.6 ng/L) (P > 0.05) seasons. This indicates that raw milk collected during the winter is at high risk for AFM₁ and that seasonal factors should be considered for the management of aflatoxins in both the feed and milk.     

Identification of cellulolytic bacteria associated with tunic softness syndrome in the sea squirt, Halocynthia roretzi

The edible ascidian, sea squirt Halocynthia roretzi (Drasche) is marine invertebrate that is a valuable source of foods and bioactive compounds. A severe disease of the sea squirt characterized by degeneration of tunic fibers formed of bundled cellulose microfibrils has occurred. We hypothesized that bacteria lyse the cellulose fibril structure, cellulase activity may be a causative agent of the disease. Among the bacteria isolated from diseased sea squirt, Pseudoalteromonas sp. NO3 had cellulase activity based on a Congo red overlay assay and starch-reducing activity. Sea squirts exhibited 40–100% cumulative mortality after injection with Pseudoalteromonas sp. NO3 using doses of 2×10⁶?2×10⁸ colony forming unit (CFU)/individual. Dead sea squirts possess thinner and ruptured tunics, which were similar to natural outbreaks. These results suggest that Pseudoalteromonas sp. NO3 possessing cellulase activity is one of the causes of tunic softness syndrome in sea squirt.