蔗糖溶液辅助水剂法提取苦杏仁油的工艺研究

采用蔗糖溶液辅助水剂法提取苦杏仁油,以改善水剂法工艺中乳化严重的现象,降低苦杏仁油中氢氰酸的含量。在单因素试验的基础上,选取蔗糖溶液浓度、提取温度、液料比这3个对提油率影响显著的因素设计响应面试验并进行优化研究。结果表明:提取温度和蔗糖溶液浓度对提油率影响较大;最优工艺条件为蔗糖溶液浓度0.27 mol/L、提取温度94.5℃、液料比6∶1、提取时间3 h,此条件下苦杏仁提油率可达73.01%;与传统提油工艺相比,蔗糖溶液辅助水剂法提取的苦杏仁油中氢氰酸含量明显降低,为7.74 mg/kg,具有一定优越性;苦杏仁毛油酸值和过氧化值均符合国家质量标准,表明蔗糖溶液辅助水剂法的提油工艺可行,具有一定推广和应用前景。     

盐效应辅助水剂法提取南瓜籽油及其理化特性研究

为了改善水剂法提取的油乳化严重现象并且提高出油率。以南瓜籽为实验材料,碳酸钠溶液为萃取剂,采用盐效应辅助水剂法提取南瓜籽油。考察了碳酸钠浓度、液料比、提取时间、搅油温度四个因素对南瓜籽提油率的影响,并利用响应面分析对提油工艺进行了优化。结果表明,碳酸钠溶液浓度和液料比对提油率的影响较大;盐效应水剂法提取南瓜籽油在搅油温度为80℃条件下,最优工艺条件为:碳酸钠浓度1.8mol/L、液料比6.8∶1(mL∶g)、提取时间120.2min(实验实际提取时间选为120min),南瓜籽提油率为70.6%;南瓜籽油的酸值和过氧化值等均符合国家食用油质量标准,可以直接食用,表明盐效应辅助水剂法提取南瓜籽油工艺是可行的。     

超声波辅助提取栝楼籽油工艺优化

以嘉兴产栝楼为试验材料,采用索氏提取法研究不同溶剂对栝楼籽提油率的影响,并获得最佳的提取溶剂;通过单因素试验和正交试验研究超声波辅助提取栝楼籽油的最佳工艺条件,并获得最高提取率。试验结果表明:乙醚的提油率最高,超声波辅助提取时料液比为1∶6(g/mL)、浸提温度为50℃、浸提时间为20 min栝楼籽油提油率最高。     

水剂法提取腰果油工艺条件研究

采用水剂法研究腰果油的最佳提取工艺,分别以料液比、提取温度、提取时间和离心力为单因素研究其对提油率的影响,并通过正交设计试验确定腰果油的最佳提取工艺条件为料液比1:1 g/mL、提取时间4 h、离心力4 800 r/min,最佳条件下获得的提油率为74.39%。采用水剂法得到的腰果油色泽浅黄澄清透明,具有腰果固有的清香味。理化指标测定结果表明,油的酸价为0.65 mg/g,碘值为14.25 gI/100 g,皂化值为186 mg/g,符合国家食用油质量标准,过氧化值未检出。水剂法提取腰果油的脂肪酸分析表明其含有的脂肪酸主要有棕榈酸(质量分数为10.32%),油酸(62.87%),和亚油酸(25.36%)。     

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%。     

水剂法提取澳洲坚果油及其理化特性的研究

研究水剂法提取澳洲坚果油的工艺,采用单因素试验分别研究了料水比、浆液pH值、浸提温度、提取时间和离心转速对提油率的影响。在此基础上,采用正交试验确定最佳提取工艺为料水比1:3g/mL、自然pH 6.4、提取时间1 h,离心转速4 800 r/min,在此条件下提油率可达67.50%。采用水剂法得到的澳洲坚果油色泽浅黄透明,具有澳洲坚果香味。澳洲坚果油理化特性结果表明,pH条件对水剂法提取油品质有一定影响,水剂法提取油酸值和过氧化值均符合国家食用油质量标准。     

文冠果籽油的微波辅助提取工艺优化及组成分析

以文冠果籽为原料,研究了微波辅助提取文冠果籽油的工艺条件,通过单因素试验和正交试验,探讨了溶剂种类、微波功率、提取时间、温度、料液比对文冠果籽油提取率的影响;并采用气相色谱-质谱联用方法分析了文冠果籽油的组成。结果表明:最佳提取剂为石油醚(沸程60～90℃),最佳料液比1:16(g:mL)、提取时间20min、提取温度85℃、微波功率100W;文冠果籽油的主要组成成分为亚油酸、油酸、棕榈酸、二十二烯酸、11-二十烯酸、硬脂酸、二十四碳烯酸等。采用微波辅助提取时间短,效率高,微波萃取是一种高效省时的文冠果籽油提取方法。     

响应面分析法优化油茶籽油水剂法提取工艺

以油茶籽为材料,利用响应面分析法优化油茶籽油水剂法提取工艺条件,并对得到油茶籽油的品质进行分析。结果表明最佳工艺条件为:原料经150℃烘烤后自然pH值条件下,提取温度80.2℃、水料比3.8:1(mL/g)、提取时间3.4h,在此条件下提油率可达69.1%。油茶籽油的各项理化指标均符合压榨二级油茶籽油国家标准,表明水剂法提取油茶籽油工艺是可行的。     

超声波辅助提取牡丹籽油的工艺优化研究

研究了超声波辅助提取牡丹籽油。采用单因素试验研究提取次数、液料比、提取温度、提取时间对牡丹籽油提取率的影响;分别以牡丹籽油提取率和综合评分为指标,采用正交试验优化超声波辅助提取牡丹籽油的工艺条件。结果表明:以综合评分为评价指标更具优势,其兼顾了提取牡丹籽油的提取率和品质,更为全面和合理。以综合评分为指标,最优提取条件为液料比4∶1、提取温度40℃、提取时间50 min、提取次数2次。在最优条件下,牡丹籽油提取率、牡丹籽油中α-亚麻酸和亚油酸含量分别为93.1%、31.7%和26.8%。     

秋葵籽油提取工艺优化及脂肪酸组成与抗氧化分析

以黄秋葵籽为原料,利用超声波辅助提取黄秋葵籽油。分析几种溶剂对黄秋葵籽油提取率及品质的影响,以提油率为指标,利用单因素试验和正交试验对提取工艺进行优化,分析黄秋葵籽油的脂肪酸组成,分析了其清除DPPH自由基、OH自由基的能力。结果表明,最佳提取工艺为:提取溶剂采用正己烷,料液比1︰16 (g/mL)、提取温度60℃、超声波功率320 W、提取时间45 min,该条件下黄秋葵籽提油率达到24.88%±0.12%。主要含有亚油酸(44.1%)、棕榈酸(29.5%)、油酸(19.8%)和硬脂酸(3.8%)。黄秋葵籽油对DPPH自由基、OH自由基具有较好的清除作用。     

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.     

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.     

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.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

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.     

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.     

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.