超声细胞破碎辅助提取江永香菇多糖工艺及其抗氧化活性研究

为优化江永香菇多糖提取工艺,采用超声波细胞破碎辅以热水浸提,通过单因素试验考察超声时间、超声功率、料液比、浸提时间、浸提温度5个因素对香菇多糖得率的影响,以香菇多糖得率为响应值,采用响应面设计优化工艺,同时对提取的香菇多糖进行抗氧化活性研究。结果表明,提取的最佳工艺条件为:超声时间6 min、浸提温度78℃、浸提时间51 min。在此条件下,江永香菇多糖的得率可达到29.71%。超声波细胞破碎法辅以热水浸提得到的江永香菇多糖体外清除DPPH自由基能力的IC_(50)值为0.35 mg/mL,清除ABTS+自由基能力的IC_(50)值为1.76 mg/mL,相同浓度下,其DPPH自由基清除能力和ABTS~+自由基清除能力均高于热水回流法提取得到的江永香菇多糖。     

超声辅助热水浸提双孢菇菇柄多糖工艺条件的优化

为提高双孢菇的综合利用率,以双孢菇菇柄为原料,在单因素试验的基础上,采用响应面分析法来优化超声辅助热水浸提双孢菇菇柄多糖的工艺条件。试验通过采用Box-Behnken中心组合设计原理研究了液料比、超声时间和超声温度对双孢菇菇柄多糖提取率的影响,利用Design-Expert 8.05b软件分析预测最佳提取工艺,优化得到的最佳提取条件为:液料比31∶1,浸提22min,温度47℃,粗多糖提取率为1.03%。经验证试验表明,菇柄多糖提取率的预测值与实际误差为5.4%,所以通过此方法优化的双孢菇菇柄多糖提取工艺条件可靠。     

牡丹籽多糖提取工艺及体外抗氧化活性研究

为确定从牡丹籽粕中提取牡丹籽多糖的工艺参数,以水浴温度、超声时间、料液比、提取次数为因素,在单因素试验的基础上,采用响应面法优化超声波辅助热水浸提多糖的最佳工艺,并通过DPPH自由基和ABTS+自由基清除能力对牡丹籽多糖的抗氧化活性进行初步研究.结果表明:牡丹籽多糖的最佳提取工艺为水浴温度85℃、超声时间40 min、...     

黔产多汁乳菇多糖的提取及抗氧化性研究

目的:研究多汁乳菇多糖的提取工艺以及抗氧化活性。方法:采用热水浸提法和正交实验优化多汁乳菇粗多糖的提取工艺;借助紫外分光光度法测定多汁乳菇粗多糖对羟自由基、1,1-二苯基-2-三硝基苯肼(DPPH)自由基、2,2-联氮基双(3-乙基苯并噻唑啉-6-磺酸)自由基(ABTS+·)的清除能力以及总抗氧化能力。结果:提取多汁乳菇多糖的最优工艺为:液料比30 m L/g,时间3 h,温度80℃,其提取率可达(3.12±0.15)%;多汁乳菇粗多糖清除羟自由基、ABTS+·自由基、DPPH自由基的半数效应浓度(IC_(50))值分别为1206.44、4602.22、96.68μg/m L,使FRAP值达到0.5时所需质量浓度为1833.38μg/m L。结论:说明多汁乳菇多糖有较强的抗氧化能力。     

超声波辅助提取霍山石斛多糖及其抗氧化活性研究

以霍山石斛为原料,利用超声波辅助法提取霍山石斛多糖,采用Box-Behnken设计和响应面分析对提取条件进行优化,同时比较了超声波辅助提取工艺和热水浸提工艺所得霍山石斛多糖的还原力和ABTS自由基清除率。结果表明,超声波辅助提取霍山石斛多糖的最优工艺条件为:液料比30:1,浸提温度81℃,浸提时间120 min,超声功率423 W,超声时间8 min,在此优化条件下多糖平均得率为19.96 mg/g,是传统热水浸提工艺的1.70倍。体外抗氧化结果显示,超声波辅助提取工艺所得霍山石斛多糖还原力和ABTS自由基清除率均优于热水浸提的多糖。该试验结果为后续霍山石斛多糖的提取和抗氧化活性研究提供了实验依据和技术支持。     

超声辅助提取秋葵粗多糖的工艺优化及其体外抗氧化性研究

秋葵多糖具有多种生理活性,是功能性食品开发的潜在原料。目前,主要采用酸法、碱法、酶法和热水浸提法提取秋葵多糖,提取过程中的化学、物理因素易对秋葵多糖活性产生不利影响。通过单因素、响应面实验优化超声辅助热水浸提秋葵多糖工艺参数,发现提取过程中各因素对提取率的影响大小为:提取时间提取温度水料比提取次数;超声辅助热水浸提最佳提取工艺参数为:水料比32:1、提取时间59 min、提取温度66℃,实际提取率30.23%,高于现有提取方法。进一步测定该优化工艺下秋葵多糖的抗氧化能力发现:在秋葵粗多糖浓度为8mg/mL时,对DPPH、ABTS、·OH清除率、脂质过氧化抑制率和还原力分别为88.8%、72.1%、68.3%、56.9%、0.724(OD_(700 nm)),且均表现出良好的量效关系。结果表明,优化后的超声辅助热水浸提秋葵多糖的新工艺,在提高多糖提取率的基础上,有效保护了秋葵多糖的抗氧化活性。     

响应面法优化黑果枸杞多糖的提取工艺研究

优化黑果枸杞果实多糖的提取工艺.采用单因素试验,考察了水浸提取温度、时间、料液比对多糖提取率的影响规律,依据Box-Behnken的中心组合设计,采用响应面法优化从黑果枸杞中提取粗多糖.最佳工艺条件为热水温度90℃,时间66min,料液比1∶25(g∶mL);在此条件下黑果枸杞多糖得率为29.36％.采用响应面法优化热水浸提黑果枸杞多糖的工艺条件稳定可行.     

木槿花多糖的超声波辅助热水浸提工艺优化及抗氧化活性研究

以木槿花为材料,在常规热水浸提基础上辅助超声波破碎提取木槿花多糖。通过单因素实验和Box-Behnken实验设计,采用响应曲面法研究超声波辅助热水浸提工艺对木槿花多糖提取率的影响,建立多糖提取率与提取因素之间的数学模型。结果表明:在常规热水辅助超声波破碎提取木槿花多糖时,在超声时间20min、超声功率473W、料液比为1∶25(g/mL)时木槿花多糖提取率达到(6.36±0.12)%。体外抗氧化实验初步验证了木槿花多糖对羟基自由基(·OH)和超氧阴离子(O2–)的清除能力较强。     

忧遁草多糖提取工艺优化及抗氧化活性研究

以提取温度、料液比和提取时间为影响因素,忧遁草多糖提取率为评价指标,采用Box-Behnken响应面法优化提取工艺。结果表明,忧遁草多糖的最佳提取工艺条件为料液比1:31 (g/mL),提取温度92℃,提取时间1.6h,此时多糖提取率为3.40%。抗氧化活性试验表明,忧遁草多糖具有良好的ABTS自由基和DPPH自由基清除效果,并具有一定的羟基自由基清除能力。     

响应面法优化山豆根多糖提取工艺及其分级醇沉组分的抗氧化活性

为研究山豆根多糖的提取工艺及其抗氧化性,采用热水浸提法提取山豆根粗多糖(SGP),研究提取温度、提取时间、液料比对多糖得率的影响,在单因素实验基础上采用响应面法对山豆根粗多糖的提取工艺进行条件优化。将提取得到的粗多糖分级醇沉,并分别采用清除DPPH、ABTS+自由基及还原能力的方法对各醇沉组分多糖的抗氧化活性进行评估。结果表明,山豆根粗多糖的最佳提取工艺条件为:提取温度83℃,提取时间133 min,液料比30:1 mL/g。在此工艺条件下,山豆根粗多糖得率为3.98%。粗多糖经分级醇沉共获得SGP50、SGP70、SGP80和SGP90 4个组分,且SGP90表现出最强的抗氧化能力,尤其是在清除DPPH自由基方面,显著高于其它组分(P<0.05)。     

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.     

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.     

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.     

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.     

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.     

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.