响应面法优化超声波辅助提取黄秋葵籽油工艺研究

以正己烷为提取溶剂,采用超声波辅助提取黄秋葵籽油。在单因素试验的基础上,以黄秋葵籽油得率为响应值,利用响应面法优化超声波辅助提取工艺条件。结果表明:黄秋葵籽油的最佳工艺条件为物料粒度80目、料液比1∶8、超声功率120 W、提取时间45 min、提取温度60℃、提取次数2次;对优化的工艺条件进行验证,黄秋葵籽油的得率为17.27%,与预测值接近。     

超声波辅助提取玫瑰茄籽油工艺的研究

本试验以玫瑰茄籽为原料,以石油醚为提取溶剂,采用超声波辅助法对玫瑰茄籽油脂的提取工艺进行研究。利用正交试验探讨超声时间、超声温度、料液比、超声功率对玫瑰茄籽油得率的影响。结果表明影响玫瑰茄籽油得率的因素主次顺序为：料液比〉功率〉温度〉时间;最佳提取工艺条件为：料液比1∶10、超声功率120W、温度50℃、提取时间40min,得率为11.77%。     

超声波—微波协同萃取黄秋葵籽油的工艺研究

以黄秋葵籽为原料,采用超声波-微波协同萃取法萃取黄秋葵籽油。在单因素试验考察萃取溶剂、料液比、萃取功率、萃取时间4个因素对黄秋葵籽油萃取率影响的基础上,选用料液比、萃取功率和萃取时间采用Box-Behnken响应曲面优化设计试验确定了最佳提取工艺条件。结果表明:黄秋葵籽油的最佳萃取工艺条件为:以正己烷做为萃取溶剂,料液比1:10(g/m L)、萃取时间10.1 min、萃取功率68 W,在此工艺条件下黄秋葵籽油的萃取率可达27.21%。     

黄秋葵籽油的提取工艺优化及脂肪酸组成分析

研究了溶剂浸提法提取黄秋葵籽油的最佳工艺条件,并采用GC-MS分析其脂肪酸组成。通过单因素试验重点探讨浸提溶剂、料液比、浸提温度、浸提时间对黄秋葵籽出油率的影响,并采用正交试验确定最佳浸提工艺条件。结果表明,以石油醚(沸程60～90℃)作为浸提溶剂提取黄秋葵籽油的最佳工艺条件为：料液比（g/mL）1∶10,浸提温度60℃,浸提时间5 h;在最佳工艺条件下,黄秋葵籽出油率为16.22%;黄秋葵籽油脂肪酸组成主要为亚油酸(41.13%)、棕榈酸(37.27%)和油酸(17.19%)。     

超声波辅助提取花椒籽油的工艺研究

为了提高花椒的经济价值,充分利用花椒籽中的花椒籽油,以脱蜡花椒籽为原材料,利用超声波辅助提取花椒籽油.首先,通过预处理试验确定最佳提取溶剂,然后,通过单因素试验对影响花椒籽油得率的因素(液料比、提取时间、提取温度、超声波功率)进行探讨.最后,采用Box-Behnken中心组合试验设计原理,以油脂得率为考察指标,对液料比、超声功率、提取时间进行3因素3水平响应面分析,确定了在该试验中超声波辅助处理提取花椒籽油最佳工艺参数:液料比:21.5∶1 (mL/g),提取时间:25 min,提取温度:60℃,超声功率350 W.在此条件下,花椒籽油得率为27.25％.     

超声波辅助提取猕猴桃籽油的工艺优化

研究超声波辅助提取猕猴桃籽油的最佳工艺条件,并分析其脂肪酸组成。采用单因素试验和正交试验,探讨了物料粒度、提取溶剂、料液比以及提取温度、提取时间、超声功率等对猕猴桃籽油提取率的影响,并对提取工艺条件进行了优化。结果表明,最佳工艺条件为:以石油醚为提取溶剂,物料粒度40目,料液比1∶10,超声功率360 W,提取温度45℃,提取2次,每次30 m in;在此条件下提取率为31.26%。GC-MS分析表明,猕猴桃籽油主要脂肪酸组成为亚麻酸(65.3%)、油酸(14.5%)、亚油酸(13.3%)、棕榈酸(5.6%)、硬脂酸(1.3%)。     

超声辅助提取黑莓籽油及其脂肪酸成分分析

以黑莓籽为原料,采用超声波辅助法提取黑莓籽油,通过单因素试验及正交试验,研究了提取剂、料液比、超声提取时间、超声提取功率对黑莓籽油得率的影响,确定了黑莓籽油提取的最佳工艺条件,并采用气相色谱-质谱法(GC-MS)分析了黑莓籽油的脂肪酸组成。结果表明,黑莓籽油提取的最佳工艺参数为:提取剂为石油醚(30～60℃),超声功率400 W,超声时间10 min,料液比1∶10,在该工艺条件下黑莓籽油的得率为17.06%。气相色谱-质谱分析表明,黑莓籽油的脂肪酸组成是亚油酸(76.00%)、亚麻酸(15.48%)、棕榈酸(5.81%)和硬脂酸(2.70%)。     

基于PB设计和BBD响应面法优化牡丹籽饼中油脂的超声辅助提取工艺

优化牡丹籽饼中油脂的超声辅助提取工艺。在单因素试验的基础上,采用Plackett-Burman(PB)设计对影响牡丹籽饼中油脂提取的7个因素(粒度、液料比、浸提时间、浸提温度、超声温度、超声时间、超声功率)进行筛选。根据PB试验结果,选择粒度、浸提温度、液料比、超声温度为考察因素,运用BBD响应面法对牡丹籽饼中油脂的超声辅助提取工艺进行优化。结果表明:牡丹籽饼中油脂的最佳提取工艺条件为粒度80目、液料比27∶1、浸提温度45℃、浸提时间4 h、超声温度42℃、超声功率320 W、超声时间35 min,在此条件下,牡丹籽油得率为11.15%。     

苹果籽油的超声波辅助提取条件优化

以苹果籽为原料,以传统的索氏提取法为参照,采用超声波法辅助提取苹果籽油,研究超声功率、超声时间、超声温度、溶剂用量和物料粒度等单因素对苹果籽出油率和提取率的影响,在单因素的基础上,优化超声波辅助提取条件,并分析苹果籽油的脂肪酸组成,结果表明在粉碎粒度为50目、超声温度45℃、溶剂液料比7:1(mL:g)、超声功率为400 W、超声时间为30 min的条件下苹果籽油的出油率和提取率最高.GC-MS分析表明苹果籽油主要含不饱和脂肪酸,以亚油酸、油酸、棕榈酸为主,三者的含量总和占总脂肪酸总量的93%,索氏法和超声辅助法获得的油的成分没有明显差异.     

石榴籽油提取工艺的研究

以石榴籽为原料,利用超声波辅助有机溶剂提取石榴籽油,在单因素试验的基础上,通过正交试验研究了料液比、提取时间、提取温度、超声波功率对石榴籽油得率的影响,确定了超声波辅助提取石榴籽油的最佳工艺条件。结果表明,石榴籽油的最佳提取工艺条件为:料液比1∶20,提取时间40 min,提取温度50℃,超声波功率400 W。在该条件下石榴籽油得率为21.77%。     

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.     

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.     

Investigations of the natural microflora of poppy seeds (<Emphasis Type="Italic">Papaver somniferum</Emphasis>) and hazelnut kernels (<Emphasis Type="Italic">Corylus avellana</Emphasis>) including microbiological decomposition

Fatty seeds of Papaver somniferum and Corylus avellana undergo a rapid microbial degradation after being ground. Those bacteria and fungi which are mainly responsible for the microbial decay were identified, and the most important growth and death processes were documented using crucial indicator-organisms. Additionally, an aflatoxin-screening was carried out in order to assess the possible risk-potential of food intoxication. The acid value (indicator for free fatty acids) of poppy seeds and hazelnut kernels was determined during their fermentation in order to document the decomposition of triglycerides.In this study it could be proved that initially a natural decay of oil seeds is caused by bacteria, yeasts and mould fungi. After the bacteria died in the course of time, yeasts and mould fungi dominated the germ spectrum. Bacteria taking part in the degradation were identified as varieties of Staphylococcus xylosus, Enterobacteriaceae and coliforms. Yeasts were identified as Pichia burtonii, and the mould fungi are associated with the genus Alternaria.On account of the absence of the genus Aspergillus in the spectrum of mould fungi, no aflatoxin was produced.