老化纸张液相脱酸实验

介绍了国内外纸张老化的现状以及近代各种脱酸方法,并在实验室条件下采用液相脱酸法对老化纸张进行脱酸实验,对脱酸前后纸张的抗张强度、耐折度、pH值进行了比较。结果表明：Ca（OH）2水溶液法在质量浓度0.20%、温度70℃、反应30min时脱酸效果最优,有机溶液法在浓度0.20mol/L、喷淋量165g/m2时脱酸效果最优。严重老化的纸样宜选用水溶液法,轻微老化的纸样宜选用有机溶液法。     

硼砂/PVA对酸化老化纸张的脱酸增强作用研究

选取硼砂作为脱酸剂,聚乙烯醇(PVA)作为增强剂,将二者以一定比例配制的硼砂/PVA复合液作为酸化老化纸脱酸增强剂,研究了硼砂与PVA配比、硼砂/PVA在纸张中的用量对纸张性能的影响;并通过加速老化实验,研究了处理后纸张的耐老化性能。研究结果表明,当W硼砂:WP VA为2:1,用量为2 g/m~2时,对处理的纸张脱酸增强效果相对最好,处理后纸张pH由6.53提高到8.12,同时纸张的抗张指数和撕裂指数比原纸(未处理的纸)分别增加了15.9%和72.93%,且白度与原纸相差不大;对各纸样进行加速老化实验,硼砂/PVA处理后纸张的pH仍保持较高,为7.78,而原纸为5.75;抗张指数为57.80 N·m/g,高于原纸的45.28 N·m/g;撕裂指数为2.85 mN·m~2/g,高于原纸1.78 mN·m~2/g;硼砂/PVA处理后的纸张耐久性得也到改善,表现为纸张纤维素降解受到抑制,TG分析半衰期温度T50%明显提高,由338.49℃上升到346.86℃。     

四硼酸锂用于纸张脱酸研究

在25℃下采用四硼酸锂对两种纸张进行脱酸处理及脱酸后的老化实验,观察了脱酸剂浓度、处理时间对脱酸效果的影响,并与硼砂脱酸效果进行了比较。结果表明,纸张在质量浓度5.0 mg/mL的四硼酸锂中浸泡30 min后的强度性能较好,且脱酸后纸张的pH值控制在理想范围。老化实验后,四硼酸锂脱酸的纸张强度性能下降幅度要明显低于未脱酸处理纸张。在最佳脱酸剂质量浓度和处理时间条件下,与硼砂脱酸相比,四硼酸锂脱酸纸张的强度性能更好,四硼酸锂是一种较好的纸张脱酸剂。     

油酸改性纳米Mg(OH)2 用于纸张脱酸

利用油酸对纳米Mg(OH)2粒子进行改性,使其均匀分散在六甲基二硅醚中,制备成稳定的脱酸液;并将该脱酸液喷涂在老旧纸张上进行纸张脱酸。结果表明,采用0.1 g油酸、1g纳米Mg(OH)_2、100mL六甲基二硅醚,在反应温度50℃、反应时间1h的条件下获得的改性纳米Mg(OH)_2在六甲基二硅醚中具有良好的分散性,可作为脱酸液用于纸张的脱酸。当脱酸液涂布量为2.7 g/m~2时,相对于未脱酸纸,脱酸纸的表面pH值得到了明显提高(从4.00提高到7.92),纸张抗张指数和撕裂指数基本没有变化;经加速老化处理后,脱酸纸表面pH值为7.60左右,抗张指数和撕裂指数稍有下降,但远低于未脱酸纸;加速老化后,脱酸纸的色差为0.64,符合纸张文物"修旧如旧"的原则。     

多功能复配液应用于纸质文物保护

将纳米氧化镁、羟乙基纤维素、聚氧化乙烯和纳米二氧化钛复配制备具有脱酸、加固和抗菌功能的多功能复配液,并将其应用在纸质文物的脱酸和修复方面。结果表明,经过复配液处理后,纸张表面pH值从3.69提升至8.75,碱残留达到0.620 mol/kg,纸张抗张强度由421 N/m提升至546 N/m;再经热老化后,纸张表面pH值仍能达到8.21,碱残留达到0.600 mol/kg,抗张强度仍能保持在521 N/m,从而起到了持续保护的作用。复配液处理后的纸张具有一定的抑菌效果,抑菌圈直径达到28 mm。     

滑石粉加填纸的老化特性及脱酸增强研究

本研究在酸性条件下抄造滑石粉加填纸,通过湿热加速老化实验,研究了滑石粉在纸张老化过程中对纸张性能的影响。再以滑石粉加填酸化老化纸为研究对象,以硼砂为脱酸剂,聚酰胺多胺环氧氯丙烷(PAE)为增强剂,制备了硼砂/PAE脱酸增强剂。通过改变硼砂/PAE配比研究了其作为纸张脱酸增强剂对滑石粉加填酸化老化纸性能的影响。结果表明,酸性施胶下的滑石粉加填纸经加速老化后,随着滑石粉加填量的增加,其抗张指数下降率逐渐增大,但pH值下降率减小;当硼砂/PAE用量为2 g/m~2且硼砂和PAE的配比为1.5∶1时,其对滑石粉加填酸化老化纸脱酸增强作用效果最好。处理后纸张的pH值由5.10提高至8.28,抗张指数由17.5 N·m/g提高至24.4 N·m/g。该脱酸增强剂有效提高了纸张性能,并延缓了纸张的酸化老化,且对实验文献的字迹无不良影响。     

阳离子纳米纤维素与瓜尔胶双元体系对烟草浆料滤水留着性能的研究

利用阳离子纳米纤维素与瓜尔胶组成双元体系,研究其对烟草浆料的滤水留着性能。结果表明,在单元体系中,单独添加0.18%阳离子纳米纤维素时较好,浆料的滤水时间为23.8 s,填料留着率为19.3%,滤液阳离子需求量82.2μmol/L;单独添加0.1%瓜尔胶时较好,浆料的滤水时间为19.3 s,填料留着率为31.7%,滤液阳离子需求量84.8μmol/L。在用量为0.18%的阳离子纳米纤维素与用量0.1%的瓜尔胶组成的双元体系下,浆料滤水时间为18.6 s,填料的留着率为40.1%,滤液的阳离子需求量为73.8μmol/L。另外,在造纸法烟草薄片的实验中,阳离子纳米纤维素与瓜尔胶组成的双元体系较单独使用瓜尔胶或阳离子纳米纤维素可明显改善烟草浆料的滤水留着性能,有效降低滤液对阳离子的需求量。     

抑制和延缓旧书籍纸酸化老化的研究

选用三种碱性金属离子螯合剂硼砂、硅酸钠、三聚磷酸钠作为纸张脱酸剂,研究其处理后纸张性能变化及延缓纸张老化的作用。研究结果表明,三种脱酸剂处理后的纸张性能得到改善,其中硅酸钠脱酸效果最好,处理后纸张pH达9.87,硼砂对纸张的强度提升效果最好,处理后纸张抗张指数提高23.78%,且pH提高至8.67;经加速老化后,处理后纸张性能下降均有所减缓,其中硼砂处理纸张延缓老化作用效果最好,老化20天后pH为7.89,与原纸(未处理)比较,pH高55.01%,抗张指数高42.38%,白度高30.37%。此外,处理后纸质文献的文字油墨保持良好,无明显变化。     

纸质文献保存的合适pH值范围研究

本研究利用超声雾化法改变纸张的初始pH值,对预处理后的纸张进行湿热老化,通过评估其色差、机械性能、热稳定性及纤维素聚合度、结晶度和官能团变化来探究保存纸张的合适pH值范围。结果表明,适合纸张长时间保存的pH值范围在8.0～8.5之间,对于已酸化的纸质文献应使脱酸终点保持在此范围内。纸张pH值碱性过高或酸性,都会导致纤维素发生水解,纸张机械性能下降、热稳定性变差、纤维素结晶度和聚合度降低,并加速纸张返黄。纸质文献脱酸时,为避免碱性过高pH值条件下的纤维素碱性水解,纸质文献脱酸保护中选用的脱酸剂pH值也不宜过高。     

纳米氢氧化镁应用于纸质文物的脱酸

通过不同工艺制备纳米氢氧化镁(Mg(OH)2),探讨了工艺条件对纳米粒径及其分布的影响。将制备的纳米Mg(OH)2用于纸质文物的脱酸处理,通过加速热老化探讨纸张的pH值及抗张强度随时间的变化关系。结果表明,在超声波(40 kHz)和加温(90℃)的条件下可以制备纳米粒径分布窄(17.9～86.6 nm)、平均粒径在44.2 nm左右的粒子;脱酸处理后纸张的pH值得到了明显的提高(从4.5提高到8.5);热老化实验表明,脱酸处理后纸张pH值(7.5左右)和抗张强度(715N/m左右)比较稳定,从而能够长时间保存。     

Arsenic content of some edible mushroom species

The arsenic contents of 162 fruit body samples of 37 common edible mushroom taxa were analyzed. The samples were gathered from different habitats of Hungary (mainly from mountains) between 1984 and 1999. The arsenic content of the samples was measured by the inductively coupled plasma spectrometry method. Very low [lower than 0.05 mg/kg dry matter (DM)] concentrations were found in the samples of 13 taxa, while higher (or very high) contents were quantified in other common taxa (the highest arsenic content was recorded in the fruit body of Laccaria amethysthea at 146.9 mg/kg DM). The species of eight genera (Agaricus, Calvatia, Collybia, Laccaria, Langermannia, Lepista, Lycoperdon, Macrolepiota) belong to the so-called accumulating taxa, and this tendency is evident on all habitats. This arsenic accumulation capability is found in two orders of Basidiomycetes (Agaricales and Gasteromycetales), which is to say this phenomenon occurs in the families Agaricaceae, Tricholomataceae and Gasteromycetaceae. The accumulating taxa found all have a saprotrophic type of nutrition; arsenic accumulation is not detectable in xilophagous or in mycorrhizal species. The consumption of the accumulating species found has only a low toxicological risk for three reasons: the consumed fresh fruit bodies contain about a tenfold lower arsenic level than the dried ones, the majority of arsenic occurs not in poisonous inorganic, but in less dangerous (or not poisonous) organic forms, and the frequency of consumption is low.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Feeding deterrent activity of terpenoid lactones with a p-menthane system against stored-product pests

Feeding deterrent activity of eight enantiomeric pairs and one optically inactive terpenoid lactone with a p-menthane system against three storage pests was determined. The lactones were tested on adults of Sitophilus granarius, adults and larvae of Tribolium confusum and larvae of Trogoderma granarium. The isomeric starting natural compounds, (+) and (−) pulegones and (+) and (−) isopulegols, were also tested. The results showed that the introduction of the lactone moiety into the p-menthane system produced antifeedant activity in the lactones obtained. The lactones with a spiro arrangement of lactone and cyclohexane rings were more active than those with condensed rings. The configuration of chiral centres present in the molecule significantly influenced the activity of the compounds studied. In most cases, lactones obtained from R-(+)-pulegone were more active antifeedants than those obtained from S-(−)-pulegone.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.