超声波辅助与溶剂萃取枇杷仁油的对比研究

以枇杷仁为原料,对两种提取枇杷仁油的工艺和效果进行比较。通过正交试验得到溶剂法提取枇杷仁油的最佳工艺条件为：溶剂选用石油醚,料液比1：8(g:mL),提取时间2 h,提取温度80 ℃,枇杷仁油提取率为10.3%;超声波辅助法提取枇杷仁油的最佳工艺条件为：溶剂选用石油醚,料液比1：5(g:mL),超声温度60 ℃,超声时间25 min,超声功率180 W,枇杷仁油提取率为12.9%。结果表明,超声波辅助法提取的枇杷仁油得率比溶剂法高,并且超声波辅助法比溶剂法提取的时间短、温度要低,是一种短时高效的提取方法。     

超声波辅助提取枇杷仁油最佳工艺的研究

本试验对超声波辅助提取枇杷仁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,影响枇杷仁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∶5(g∶m L),超声温度60℃,超声时间25 min,超声功率180 W,枇杷仁油提取率为12.8%。枇杷仁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72.7%,特别是亚油酸的质量分数高达58.8%,具有较高的保健价值。     

超声波辅助提取南瓜籽油及其脂肪酸组成研究

采用超声波辅助提取南瓜籽油,并用单因素试验和正交试验筛选最佳提取条件。结果表明：超声波辅助提取南瓜籽油的最佳工艺条件为料液比1:8(g/mL)、超声时间20min、超声功率90W、超声温度30℃,在此条件下油脂提取率高达94.22%,各因素对提取率的影响依次为料液比、超声时间、超声功率和超声温度。气相色谱分析南瓜籽油表明,南瓜籽油中主要含有5 种脂肪酸,分别是棕榈酸、油酸、硬脂酸、亚油酸和亚麻酸。     

三文鱼油超声波辅助提取工艺及脂肪酸组成分析

利用超声波辅助提取三文鱼油,采用气质联用(GC-MS)测定其脂肪酸组成。以提取率为指标,通过单因素实验确定液料比、提取温度、超声功率和超声时间的适宜范围,通过L9(34)正交实验确定三文鱼油超声波辅助提取的最佳工艺条件。结果表明:液料比、提取温度、超声功率和超声时间对三文鱼油的提取效果有不同程度的影响,最佳提取工艺条件为液料比3∶1、提取温度65℃、超声功率250 W、超声时间10 min,在此条件下三文鱼油提取率达92. 6%;三文鱼油以不饱和脂肪酸为主,营养价值高,酸价、过氧化值均符合SC/T 3502—2016《鱼油》标准要求。     

野生桃种仁油的超声波辅助提取及GC-MS分析

采用超声波辅助法研究了超声功率、提取时间、溶剂种类、料液比对野生桃种仁油提取率的影响。在单因素试验的基础上,进行了正交试验。结果表明,各因素对超声波辅助提取野生桃种仁油的影响次序为:溶剂种类提取时间超声功率料液比;最佳工艺条件参数是:提取剂为正己烷,超声功率200 W,超声时间15 min,料液比1∶11,野生桃种仁油的提取率为45.97%。气相色谱-质谱分析表明,野生桃种仁油的油脂组成主要是油酸(65.21%)、亚油酸(19.08%)、棕榈酸(11.06%)、硬脂酸(3.39%)。     

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。     

超声波辅助与溶剂萃取枇杷仁油方法比较研究

以枇杷仁为原料,对2种提取枇杷仁油的工艺和效果进行比较。通过正交实验得到溶剂法提取枇杷仁油的最佳工艺条件为:溶剂选用石油醚(b.p 60~90℃),料液比1∶8(g∶mL),提取时间2 h,提取温度80℃,枇杷仁油收率为10.3%;超声波辅助法提取枇杷仁油的最佳工艺条件为:溶剂选用石油醚,料液比1∶5(g∶mL),超声温度60℃,超声时间25 min,超声功率180 W,枇杷仁油收率为12.9%。结果表明,超声波辅助法提取的枇杷仁油得率比溶剂法高,并且超声波辅助法比溶剂法提取的时间短、温度要低,是一种短时高效的提取方法。     

超声波与溶剂萃取西瓜籽油的对比研究

以西瓜籽为原料,对2种提取西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西瓜籽油的最佳工艺条件为:溶剂选用石油醚(b.p.60～90℃),料液比1∶8(g∶mL),提取时间2 h,提取温度80℃,西瓜籽油提取率为48.2%;超声波辅助法提取西瓜籽油的最佳工艺条件为:溶剂选用石油醚,料液比1∶6(g∶mL),超声温度50℃,超声时间50 min,超声功率150 W,西瓜籽油提取率为50.8%。结果表明,超声波辅助法提取的西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。     

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.