超声波辅助与溶剂萃取番木瓜籽油的比较研究

以番木瓜籽为原料,对2种提取番木瓜籽油的工艺和效果进行比较。通过正交试验得到溶剂法提取番木瓜籽油的最佳工艺条件为:溶剂选用石油醚,料液比1∶8(g∶m L),提取时间2 h,提取温度80℃,番木瓜籽油提取率为35.8%;超声波辅助法提取番木瓜籽油的最佳工艺条件为:溶剂选用石油醚,料液比1∶4(g∶m L),超声温度50℃,超声时间20 min,超声功率120 W,番木瓜籽油提取率为38.8%。结果表明,超声波辅助法提取的番木瓜籽油得率比溶剂法高,并且超声波辅助法比溶剂法提取的时间短、温度低,是一种短时高效的提取方法。     

超声辅助水酶法提取黄秋葵籽油的研究

为提高黄秋葵籽油的提取率,采用超声波辅助水酶法提取黄秋葵籽油,通过单因素试验和正交试验对超声波预处理条件、酶解条件进行优化.结果表明:超声波预处理条件为料液比1:7(g/mL)、超声时间35 min、超声功率70％(总功率为500 W)、超声温度45℃,在此条件下黄秋葵籽油提取率为46.46％;最佳酶解条件为加酶量2....     

苹果籽油的超声波辅助提取及成分分析

以液料比、超声时间、超声功率3个因素对超声波辅助提取苹果籽油进行二次通用旋转优化设计试验,得到了苹果籽油提取率的回归方程,并确定最佳提取条件为:液料比8.13:1,超声时间31.3 min,超声功率165.2 W.最佳条件下苹果籽油提取率24.40%.经GC-MS分析,苹果籽油中不饱和脂肪酸含量为85.31%,其中油酸35.05%、亚油酸49.19%.     

超声波辅助提取牡丹籽毛油的工艺优化及脂肪酸组成分析

以油用牡丹籽为原料,利用超声波辅助提取牡丹籽毛油,通过单因素及正交试验,研究提取试剂、超声时间、超声温度、超声功率和料液比对牡丹籽毛油提取率的影响,确定超声波辅助提取牡丹籽毛油的最佳工艺条件,并用气相色谱仪分析牡丹籽毛油的脂肪酸组成。结果表明,超声波辅助提取牡丹籽毛油的最佳提取条件为:以正己烷作为提取试剂,超声温度为50℃,超声时间为50 min,超声功率为140 W,料液比为1∶15(g∶m L)。在此条件下,牡丹籽毛油的提取率为(26.11±0.01)%。气相色谱分析显示,牡丹籽毛油的主要成分为棕榈酸、硬脂酸、油酸、亚油酸和亚麻酸,其中不饱和脂肪酸含量高达(92.35±0.51)%,亚油酸和亚麻酸的含量分别为(28.80±0.24)%和(41.13±0.09)%,说明牡丹籽油是一种营养价值很高的食用油脂。     

响应面法优化超声辅助水酶法提取辣木籽油

以辣木籽为原料,通过超声辅助水酶法提取辣木籽油。以辣木籽油提取率为指标,利用单因素试验考察pH值、果胶酶添加量、提取时间、提取温度、超声功率对辣木籽油提取率的影响,在此基础上采用响应面法确定提取辣木籽油的最佳工艺条件。结果表明,最佳提取工艺为果胶酶添加量0.50%、pH3.5、提取温度54℃、提取时间12 h、超声功率84 W,此时辣木籽油提取率为30.56%。     

超声波辅助提取番木瓜籽油最佳工艺的研究

本试验对超声波辅助提取番木瓜籽油的最佳工艺进行了研究,利用正交试验探讨了影响提取率的主要因素。结果表明,影响番木瓜籽油提取率的因素主次顺序依次为:料液比超声温度超声时间超声功率;最佳提取条件为:石油醚为提取剂,料液比为1:4(g:mL),超声温度50℃,超声时间20 min,超声功率120 W,番木瓜籽油提取率为35.1%,番木瓜籽油的脂肪酸主要由棕榈酸和不饱和脂肪酸组成,不饱和脂肪酸占80.7%,特别是油酸的质量分数高达72.7%,具有较高的保健价值。     

超声波辅助提取苏籽油工艺优化

采用超声波辅助提取苏籽油,在单因素试验基础上通过正交试验对提油工艺进行优化,并采用气相色谱法对最优工艺下提取的苏籽油中α-亚麻酸的含量进行测定。结果表明,超声液辅助提取苏籽油的最佳工艺条件为:以正己烷为提取溶剂,料液比l∶55,超声功率50 W,超声波提取时间125 min,超声波提取温度55℃,在此条件下苏籽油得油率为34.88%。气相色谱法测定最佳提取工艺下所得苏籽油中α-亚麻酸含量为0.121 3 mg/μL,占总油量的15.2%。     

超声波辅助提取新疆打瓜籽油脂的工艺研究

以新疆打瓜籽为研究对象,通过超声波辅助溶剂法提取打瓜籽油。以打瓜籽油的提取率为评价指标,在单因素的基础上,选取超声温度、提浸提时间、超声功率和液料比进行Box-Behnken响应面法试验设计,对其提取工艺参数进行优化。研究表明,打瓜籽油提取工艺的最佳条件为液料比为7∶1(mL/g),浸提时间为4 h,超声时间30 min,超声温度为50℃,超声功率为180 W,此条件下,打瓜籽油的提取率最高达27.88%。气相色谱法测定结果表明超声波提取的打瓜籽油中含有73.51%的亚油酸。     

超声波提取火棘籽油的工艺研究

利用超声波从火棘籽中提取火棘籽油,此法有良好的提取率。正交试验考察了超声波功率、提取时间、料液比以及提取温度对提取率的影响,得出最佳提取条件为超声波功率250 W,提取时间40 min,提取温度45℃,料液比1∶8(g∶mL),在此条件下火棘籽油的提取率为7.66%。     

光皮梾木籽油的提取及其品质的研究

优化光皮梾木籽油的提取工艺及其品质的测定。采用正交试验法,考察超声波提取功率、超声温度、超声时间、料液比对提取率的影响;同时考察了光皮梾木籽油的品质。所考察因素中,对光皮梾木籽油提取率的影响程度是料液比超声波提取温度超声波提取功率超声波提取时间。最佳条件是料液比为1:10(g/mL),超声波提取时间为60 min,超声波提取功率为300 W,超声波提取温度为60℃,此时光皮梾木籽油得率最高,为(18.19±0.03)%;光皮梾木籽油的油脂品质符合食用植物原油的国家标准。采用正交试验对光皮梾木籽油提取条件进行优化可行;其各项性质表明光皮梾木籽油在食品加工领域有一定的应用价值和理想的前景。     

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.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.     

鸡源大肠埃希氏菌mcr-1基因携带及分析

目的 了解在农业农村部禁止使用多黏菌素作为动物促生长使用后四川部分地区鸡源大肠埃希氏菌（E.coli）mcr-1基因的携带情况,为制定进一步防控措施提供依据。方法 采集四川部分地区市场售卖点肉鸡直肠拭子,用含有多黏菌素（终浓度4 μg/mL）的EC肉汤增菌接种含多黏菌素（终浓度4 μg/mL）的麦康凯平板,挑取可疑菌落,采用PCR方法鉴定菌株并检测mcr-1基因;微量肉汤稀释法测定mcr-1基因阳性菌株对临床常见抗菌药物耐药情况。脉冲场凝胶电泳（PFGE）对mcr-1基因阳性菌株进行同源分析。耐药基因质粒结合实验验证mcr-1基因传播途径。结果 从70份肉鸡样本中的13份检出mcr-1基因阳性大肠埃希氏菌,检出率18.57%（13/70）,对实验的13种抗生素,除13株mcr-1阳性菌株对头孢西丁有12株敏感以外,对其他抗生素都表现出不同程度的耐药,其中四环素和甲氧苄啶/磺胺甲恶唑耐药率最高,达到了100%（13/13）;其次是氨苄西林和氯霉素,耐药率为84.62%（11/13）。PFGE显示13株mcr-1阳性大肠埃希氏菌分属13个不同的型别;质粒结合实验显示mcr-1基因能够通过质粒传播。结论 mcr-1基因在鸡大肠内大肠杆菌中检测率比较高,且鸡大肠中mcr-1阳性大肠埃希氏菌的耐药情况比较严重。     

Comparison of the most odour-active volatiles in different hop varieties by application of a comparative aroma extract dilution analysis

Application of a comparative aroma extract dilution analysis on the volatiles isolated from five different hops (Hallertau Perle, Hallertau Hersbrucker Spät, Slowenian Golding, Hallertau Smaragd, US Cascade) revealed linalool and myrcene with the highest Flavour Dilution (FD)-factors in all varieties, followed by 2-isopropyl-3-methoxypyrazine, 3-methylbutanoic acid and geraniol. Some odourants, however, showed high FD-factors only in certain varieties, for example, (5Z)-octa-1,5-dien-3-one and germacrene B in Hersbrucker Spät, (3E,5Z)-undeca-1,3,5-triene in Hersbrucker Spät and Cascade and nonanal in Cascade. The overall odour profile of the Cascade sample clearly differed from the other varietes, and was dominated by a black currant like odour note. The identification experiments revealed 4-methyl-4-sulfanylpentan-2-one, so far unknown as hop constituent, as key contributor to this odour. In addition, an odour-active undecatetraene was present, in particular, in Perle and Cascade. Synthesis and structural assignment of the four stereoisomers of (3E)-undeca-1,3,5,9-tetraene allowed the identification of the fresh, pineapple-like smelling compound as (3E,5Z,9E)-undeca-1,3,5,9-tetraene. Among the four isomers synthesised, this compound showed by far the lowest odour threshold of 0.01 ng/L in air.     

Developmental and population growth rates of phosphine-resistant and -susceptible populations of stored-product insect pests

Phosphine resistance positively contributes towards an individual's fitness under phosphine fumigation. However, phosphine resistance may place resistant individuals at a fitness disadvantage in the absence of this fumigant, which can be exploited to halt or slow down the spread of resistance. This study aimed to determine if there is a fitness cost associated with phosphine resistance in populations of the red flour beetle (Tribolium castaneum (Herbst)), the lesser grain borer (Rhyzopertha dominica (F.)) and the sawtoothed grain beetle (Oryzaephilus surinamensis (L.)). The developmental rate and population growth of phosphine-resistant and -susceptible populations of these three species of stored-product insects were therefore determined under phosphine-free environment. The majority of the phosphine-resistant populations exhibited lower developmental and population growth rates than the susceptible populations indicating that phosphine resistance is associated with fitness cost in all three species, which can potentially compromise the fixation and dispersal of the resistant genotypes. Nonetheless, some phosphine-resistant populations did not show a fitness cost. Therefore, resistance management strategies based on suppression of phosphine use aiming at eventual reestablishment of phosphine susceptibility and subsequent reintroduction of this fumigant will be useful only for insect populations exhibiting a fitness cost associated with phosphine resistance. Therefore recognition of the prevailing phosphine-resistant genotypes in a region is important to direct the management tactics to be adopted.     

Cloning and expression analysis of two catalase genes from Aspergillus oryzae

Fungi contain distinct genes encoding the same class of enzyme that are differentially regulated according to conditions. We cloned two catalase genes, catA and catB, from Aspergillus oryzae. The catA gene predicts a 747-amino-acid polypeptide sharing 81% identity with Aspergillus fumigatus catalase (catA) and 77% with Aspergillus nidulans catalase (catA). The catB gene predicts a 725-amino-acid polypeptide sharing 82% identity with A. fumigatus catalase (catB) and 75% with A. nidulans catalase (catB). However, the catA and catB genes share little homology (41%) with one another, suggesting that each gene belongs to a distinct gene family. Overexpression studies demonstrated that both genes encode a functional catalase. Promoter assays indicated that the catA gene is developmentally regulated as it was preferentially expressed in solid-state cultures undergoing sporulation. However, its expression was not affected by hydrogen peroxide treatment. Conversely, the catB gene was highly expressed under all culture conditions tested, and it was induced by hydrogen peroxide treatment. These results suggest that the catB gene may be mainly used for detoxification of oxidative stress while the catA gene may have another role such as chaperoning proteins in the spore.