干制方式对大球盖菇滋味物质的影响

以新鲜大球盖菇为原料,研究热风干燥、微波干燥和冷冻干燥对大球盖菇滋味物质的影响。结果表明,热风干燥的大球盖菇中总游离氨基酸（73.57 mg/g）、甜味氨基酸（28.48 mg/g）和苦味氨基酸（19.13 mg/g）的含量最高;冷冻干燥的大球盖菇中有机酸（241.44 mg/g）、鲜味氨基酸（10.47 mg/g）、5'-核苷酸（10.66 mg/g）和呈味核苷酸（1.44 mg/g）的含量最高。不同大球盖菇样品的等鲜浓度值为热风干燥>冷冻干燥>微波干燥。电子舌分析显示三种干制大球盖菇的滋味具有明显差异。三种干燥方式影响大球盖菇滋味物质的含量,热风干燥和冷冻干燥有利于大球盖菇中滋味物质的保留,冷冻干燥的大球盖菇中滋味物质含量更多。     

不同干燥工艺对杏鲍菇品质和挥发性风味成分的影响

为研究不同干燥方式对杏鲍菇品质和挥发性风味的影响,优选杏鲍菇干燥模式,选用热泵、热风、真空冷冻和真空微波4 种干燥工艺对新鲜杏鲍菇进行干燥处理,分析不同干燥方式对杏鲍菇主要营养成分、色度、糖（糖醇）和挥发性风味成分的影响。结果表明：杏鲍菇总蛋白受干燥方式影响较小,总糖含量在真空微波干燥条件下最低（13.56%）,总酚含量（39.97 μg/g）和粗脂肪含量（1.27%）在真空冷冻干燥条件下最低,色度方面真空冷冻干燥能较好保持杏鲍菇色泽;杏鲍菇中含量丰富的海藻糖受干燥方式影响为：热泵＞真空冷冻＞热风＞真空微波干燥,主要的糖醇甘露醇含量变化为：热泵和真空冷冻＞热风和真空微波。杏鲍菇4 种干燥方式条件下共鉴定出68 种挥发性风味成分,热泵、热风和真空微波干燥后醛类物质相对含量均最高,主要风味成分为异戊醛、正己醛和2-甲基丁醛,真空冷冻干燥后醇类物质相对含量最高,主要为1-辛烯三醇,同时还检测出酯类、酮类、烃类、吡嗪类以及少量其他类物质,各风味成分相互作用形成不同的风味。对比不同干燥方式,真空冷冻干燥能较好保持杏鲍菇品质和风味,热泵干燥在经济性和稳定性方面可以做到较好的平衡。     

大球盖菇粉的热风干燥工艺研究

以大球盖菇为原料,对热风干燥制作大球盖菇粉的加工工艺和护色剂的护色效果进行研究。结果表明,热风干燥前,对大球盖菇进行护色处理可提高干制菇片的色泽,复合护色液的最佳配方为亚硫酸钠0.1%、50℃、柠檬酸0.3%。干燥温度、蘑菇切片厚度和装载量对大球盖菇粉的色泽有显著影响,其中干燥温度对色度影响最为显著。大球盖菇粉制备的最佳工艺条件为:干燥温度50℃、切片厚度4 mm、装载量2 kg/m^2、干燥时间8 h,按此工艺生产的大球盖菇粉的色泽接近冷冻干燥粉,且具有较好的功能特性。     

干燥方式对不同生长时期秋葵果实营养品质及挥发性风味物质的影响

以不同生长时期秋葵新鲜果实为原料,分别采用杀青后热风干燥、热风干燥、自然干燥和冷冻干燥处理,研究不同干燥方式对其灰分、水分、黄酮、氨基酸和挥发性风味物质的影响。结果发现:经杀青后热风干燥和热风干燥处理后的秋葵水分含量较低,冷冻干燥相对于其他干燥方式可更好保留黄酮物质;新鲜秋葵主要挥发性风味物质为二甲基硫醚,经4种干燥方式处理后,挥发性风味物质数量都有不同程度的增加,相对含量也有一定程度的增减,且对主要挥发性风味物质二甲基硫醚有一定影响;杀青后热风干燥的秋葵果实中醇类物质和醛类物质相对含量最高,热风干燥后主要挥发性风味物质为醛类物质,经自然干燥后醇类物质相对含量较高,冷冻干燥后醛类物质相对含量较高;经4种不同干燥方式处理后,新鲜秋葵果实的主要挥发性风味物质都有所保留,同时出现其他不同的挥发性风味物质,这些物质不同的比例赋予了不同干燥方式所得秋葵果实特殊香气。     

热风干燥和真空冷冻干燥对猴头菇不同部位风味物质的影响

为探究猴头菇干燥前后风味特征的变化,本研究以新鲜猴头菇为原料,利用高效液相色谱(HPLC)技术和气相离子迁移谱(GC-IMS)技术测定并比较了热风干燥和真空冷冻干燥对猴头菇菇盖和菇柄风味物质的影响.结果表明,新鲜猴头菇经两种方式干燥后,可溶性糖、5'-核苷酸、游离氨基酸的含量均显著降低(P<0.05),其中热风干燥样品...     

干燥方式对脱水桑叶品质的影响

以新鲜桑叶为原料,研究冷冻干燥、热泵干燥、微波真空干燥和自然晒干4种干燥方式对桑叶营养成分、复水比、色差、组织结构及风味等品质指标的影响。结果表明:干制后的桑叶营养成分流失严重,色泽由鲜绿转为深绿,酯类和烃类物质明显增多;其中冷冻干燥的桑叶品质最佳,对桑叶的叶绿素、酚类和蛋白保留率较高,色泽较为鲜亮,组织结构没有发现明显皱缩,复水率可达93%;微波真空干燥和热泵干燥的桑叶品质次之,自然晒干的桑叶品质最差;通过分析干燥方式与风味物质相对含量的关联程度发现,酯类和烃类在干制桑叶风味评价中具有重要作用。热泵干燥和冷冻干燥的风味物质相近,且主要体现在酯类含量上的差异;微波真空干燥和自然晒干的风味物质比较相近。综合来看,桑叶脱水干燥方式首选冷冻干燥,其次为微波真空干燥和热泵干燥,不宜选择自然晒干,而在脱水桑叶的工业化推广上应首选热泵干燥。     

干燥方式对滁菊抗氧化、抑菌活性和挥发性风味物质的影响

以新鲜滁菊为原料,研究真空冷冻干燥、热泵干燥、热风干燥对滁菊抗氧性、抑菌活性、挥发性风味物质和感官品质的影响。结果表明:真空冷冻干燥滁菊(T1)自由基清除能力和脂质过氧化抑制能力最高,对金黄色葡萄球菌和大肠杆菌抑制作用最强,同时具有最好的感官品质。各样品活性和感官评分顺序为真空冷冻干燥滁菊(T1)热泵干燥滁菊(T2)热风干燥滁菊(T3)。运用固相微萃取—气相色谱—质谱联用对3种干燥方式的滁菊挥发性风味物质进行分析,T1、T2和T3分别鉴定出71,88,56种物质。萜烯类是3种干制滁菊的主体风味物质,相对含量均达到45%以上。因此,真空冷冻干燥工艺是滁菊最佳的脱水工艺。     

不同干燥方法对香椿苗品质的影响

研究了真空微波干燥、热风干燥、真空冷冻干燥对香椿苗干燥时间、Vc、多酚、γ-氨基丁酸、色泽、复水性以及抗氧化性的影响。结果表明,经真空冷冻干燥的香椿苗Vc、多酚以及γ-氨基丁酸含量均最高,色泽与香椿苗的天然绿色最为接近,复水性最好,但是干燥时间最长。3种干燥方法所得香椿苗的还原力没有显著性差异,但是真空冷冻干燥对DPPH自由基和羟基自由基的清除能力最高,热风干燥香椿苗的清除能力最低。真空微波干燥的香椿苗品质介于真空冷冻干燥和热风干燥之间。香椿苗在50 ℃干燥所需时间大约为40 ℃干燥时的三分之一,但是对DPPH自由基和羟基自由基的清除能力高于40 ℃,色泽更接近于天然香椿苗。     

不同干燥方式对橄榄果粉品质的影响

比较微波干燥、热风干燥、真空干燥以及真空冷冻干燥对橄榄果粉外观色泽、物理特性、营养成分及微观结构等品质的影响。结果表明:真空冷冻干燥橄榄果粉色泽较佳,具有较高亮度和最低的红绿度,最接近鲜食橄榄绿色色泽;热风干燥和真空干燥所得果粉吸油性较低,吸湿性较高,热风干燥的果粉堆积密度和溶解度均最高,真空冷冻干燥的果粉堆积密度最低,吸湿率低,复水性、流动性、吸油性和溶解度均较高,微波干燥的果粉含水率最高,复水性、吸湿率、堆积密度、吸油性和溶解度均较低;微波干燥的还原糖、总酸含量损失较小,热风干燥的类黄酮损失较小,真空干燥的总糖和总酚含量损失较小,真空冷冻干燥的蛋白质含量损失较小。扫描电镜观察微观结构发现微波干燥和真空冷冻干燥果粉颗粒间空隙大,组织较光滑完整,皱缩少,热风干燥和真空干燥果粉颗粒间空隙小,部分皱缩。通过主成分分析品质综合得分结果为:真空冷冻干燥>真空干燥>热风干燥>微波干燥。     

不同风干工艺处理的武昌鱼鱼肉品质和风味的变化

以腌制武昌鱼为原料进行干制,通过测定热泵干燥、热风干燥、冷风干燥、联合干燥四种风干工艺处理下的武昌鱼鱼肉脂质氧化理化指标,感官,色泽,质构特性,电子鼻,挥发性风味成分变化,分析不同干燥工艺处理对武昌鱼品质特性和风味变化的影响。热泵干燥的武昌鱼脂质氧化程度更显著,初级产物氢过氧化物含量最高为4mmol/kg,脂质氧化二级产物丙二醛含量最高为0.68 mg/kg,感官评分结果最好（8.6分）、质构表现最好;冷风干燥处理的武昌鱼色泽表现最差,热风、热泵、联合干燥处理的武昌鱼差异较小;热风干燥处理的武昌鱼硬度最大53.96 N、热泵干燥处理的武昌鱼弹性最大;电子鼻检测表明四种干燥工艺处理武昌鱼风味呈现显著性差异（P<0.05）;挥发性风味物质检测发现联合干燥处理武昌鱼挥发性风味物质含量最多21种,热泵处理挥发性风味物质含量最低仅有6种。综上所述联合干燥处理的武昌鱼鱼肉,脂质氧化程度硬度低、弹性好、挥发性风味物质含量多种类丰富。     

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.     

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。     

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.     

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.     

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.     

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.