低温连续相变萃取蓝圆 鱼油及其脂肪酸组成分析

采用新型萃取技术——低温连续相变萃取技术提取蓝圆鲹鱼油,考察物料水分含量、萃取温度、压力、时间、解析温度等因素对蓝圆鲹鱼油得率的影响,通过响应面设计确定最佳提取工艺条件,并对蓝圆鲹鱼油的理化性质和脂肪酸组成进行了分析。研究结果表明,低温连续相变萃取蓝圆鲹鱼油的最佳工艺为:物料水分含量11%,萃取温度52℃,萃取时间62 min,萃取压力0.6 MPa,解析温度为65℃,此工艺条件下鱼油得率为21.56%。鱼油外观为黄色至红棕色,有较淡的鱼腥味,其理化指标达到了粗鱼油标准SC/T3502-2000的一级要求。气相色谱-质谱法(GC-MS)分析鉴定出20种脂肪酸,多不饱和脂肪酸为59.57%,其中二十碳五烯酸(EPA)与二十二碳六烯酸(DHA)占总脂肪酸含量的24.62%。低温连续相变萃取技术应用于鱼油生产,具有萃取效率高、萃取温度低、对鱼油成分无破坏等特点,显示出良好的经济效益及应用前景。     

超临界CO_2萃取秋刀鱼内脏油和卵磷脂

采用超临界CO_2萃取技术从秋刀鱼加工废弃物内脏中先后萃取鱼油和卵磷脂。利用单因素和响应面分析法优化其工艺参数,得出最佳萃取条件。超临界CO_2一次萃取鱼油,选择萃取压力、萃取温度和萃取时间3个主要因素,以鱼油得率为响应值,经优化的最佳萃取工艺条件是:萃取压力45 MPa,萃取温度55℃,动态萃取3 h。由响应面模型预测的鱼油得率为21.66 g/100 g(湿样),实际值为22.0 g/100g(湿样)。以萃取过鱼油的内脏为原料进行二次萃取,选择萃取压力、萃取温度、夹带剂(无水乙醇)流速和萃取时间4个主要因素,以卵磷脂得率为响应值,优化的最佳条件是:萃取压力45 MPa、萃取温度50℃、夹带剂流速2.0 m L/min以及萃取时间2.5 h。由响应面模型预测的卵磷脂得率9.24 g/100 g(湿样),实际值为9.2 g/100 g(湿样)。     

蓝圆鲹鱼油微胶囊的制备工艺优化及其稳定性

以蓝圆鲹鱼油为原料,通过单因素及响应面优化实验,研究喷雾干燥法制备蓝圆鲹鱼油微胶囊的工艺条件,考察鱼油含量、固形物含量、进(出)风温度及进料速度四个因素对鱼油微胶囊化效率的影响,并测定微胶囊的微观结构及稳定性。结果表明,喷雾干燥法制备蓝圆鲹鱼油微胶囊的最佳工艺条件为鱼油含量30%,固形物含量37%,进(出)风温度为190℃(85℃),进料速度为480 mL/h。在此条件下微胶囊包埋率为91.56%;所制得的鱼油微胶囊外观为圆球形颗粒,表面光滑、致密、无裂痕,整个表面性状良好;经60℃加速氧化6 d后蓝圆鲹鱼油微胶囊的过氧化值(peroxide value,POV)显著低于未微胶囊化鱼油(p0.05),蓝圆鲹鱼油的稳定性在微胶囊化后得到显著提高(p0.05)。     

超临界CO2提取花椒精油的研究

为采用超临界CO2提取花椒精油,采用正交实验法对花椒精油的超临界CO2提取工艺进行优化,以精油的得率为指标,考察萃取压力、温度、时间对精油得率的影响.得到的最佳工艺条件为:萃取压力30 MPa, 萃取温度40℃,萃取时间130 min,花椒精油得率10.81%.超临界CO2提取花椒精油得率高,提取时间短,是提取花椒精油的适宜方法.     

菠萝皮中多酚的制备及其清除自由基研究

研究考察了超临界二氧化碳萃取菠萝皮多酚的工艺,采用单因素试验及响应面分析试验研究菠萝皮多酚超临界二氧化碳水萃取菠萝皮中多酚工艺中的超临界二氧化碳萃取压力,超临界二氧化碳萃取温度,超临界二氧化碳萃取时间,超临界二氧化碳萃取液固比值4个因素对多酚得率的影响,并在此基础上进一步响应面分析优化,从而确定最佳工艺条件。结果表明,最优工艺条件为:超临界二氧化碳萃取压力为23 MPa,超临界二氧化碳萃取温度为54℃,超临界二氧化碳萃取时间为1.90 h,超临界二氧化碳萃取液固比值为45 mL/g,在此条件下得到最高的理论得率为60.76 mg/g;采用上述最优提取条件进行菠萝皮多酚的提取试验,实际测得菠萝皮多酚得率为61.12 mg/g,理论预测值与实测值相比无显著差别;菠萝皮多酚清除羟自由基的试验表明其对·OH的抗氧化能力优于VC和柠檬酸。该工艺试验研究验证了超临界二氧化碳萃取方法的高效、节能的优势,这为菠萝皮多酚的产业化提供了有力的理论和工艺基础。     

罗勒子油的超临界CO_2提取工艺及其成分分析

研究萃取温度、萃取压力、萃取时间对超临界CO_2萃取罗勒子油得率的影响,进行了工艺的优化。结果表明,影响超临界CO_2萃取罗勒子油得率的因素主次顺序为A(压力)C(时间)B(温度),最佳工艺条件为萃取压力300 Pa,萃取温度45℃、萃取时间为3 h。在此工艺条件下,罗勒子油得率为17.05%。罗勒子油脂肪酸组成主要为亚麻酸(85.76%)、棕榈酸(8.54%)和硬脂酸(5.1%),其中不饱和脂肪酸含量为86.35%。     

翅果油超临界CO2流体萃取工艺优化及其不同提取方法的比较

对翅果油的超临界CO_2流体萃取工艺条件进行研究。在单因素试验的基础上,以萃取压力、萃取温度、萃取时间和原料粒度为影响因素,以翅果油得率为指标,采用正交试验优化工艺条件。比较了浸出法、超临界CO_2流体萃取法、冷榨法和热榨法4种不同提取方法对翅果油得率和微量活性成分的影响。结果表明:超临界CO_2流体萃取翅果油最优工艺条件为萃取压力30 MPa、萃取温度50℃、萃取时间150 min、原料粒度80目,此条件下翅果油得率为(28. 32±1. 15)%; 4种提取方法中,浸出法的翅果油得率、VE及甾醇含量最高,其次是超临界CO_2流体萃取法,除热榨法的翅果油角鲨烯含量最高外,压榨法的其他指标均最低。     

巴旦杏仁油脂的超临界二氧化碳萃取工艺及其成分分析

研究巴旦杏仁油的超临界CO2萃取工艺,通过单因素实验和正交实验设计探讨了萃取压力、温度、CO2流量和萃取时间对巴旦杏仁油超临界CO2萃取得率的影响。结果表明萃取压力35MPa ,萃取温度40℃,二氧化碳流量6L/min,萃取时间4h为最优条件,在此条件下巴旦杏仁油萃取得率达到43.10%;采用气相色谱-质谱(GC-MS)联用技术对巴旦杏仁油脂肪酸组成进行分析,结果表明巴旦杏仁油不饱和脂肪酸含量高达92.20%,以油酸(78.448%)、亚油酸(13.723%)为主,饱和脂肪酸以棕榈酸(6.018%)为主。     

超临界CO_2萃取紫苏油粕β-胡萝卜素的研究

以紫苏油粕为原料,采用超临界CO_2萃取技术提取紫苏油粕中的β-胡萝卜素。在单因素试验的基础上,采用Box-Behnken试验设计方法和响应面分析法对超临界CO_2萃取工艺条件进行优化,研究萃取压力、萃取温度、萃取时间及其交互作用对β-胡萝卜素得率的影响。结果表明,在各影响因素中,影响程度依次为:萃取压力萃取时间萃取温度,超临界CO_2萃取紫苏油粕β-胡萝卜素的最佳工艺条件为:萃取压力38 MPa、萃取温度43℃、萃取时间3 h。在此条件下β-胡萝卜素得率为91.57%,与模型预测值92.82%之间具有良好的拟合性。     

基于超临界CO_2萃取技术提取酿酒黄水中风味物质

采用超临界萃取技术从黄浆水中提取风味物质,系统研究萃取条件(萃取压力、乙醇夹带剂添加量、萃取温度)、分离条件(压力、温度、时间)等工艺参数对黄浆水中风味物质萃取物得率以及风味物质总量的影响。实验结果表明黄浆水含有丰富的风味物质,最优萃取工艺条件下黄浆水中风味物质最高萃取得率为7. 4%,超临界CO_2萃取技术提高了黄浆水的利用率及白酒行业的经济效益和社会效益。     

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。     

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.     

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.