水酶法提取杨梅核仁油的工艺优化

通过响应面法分析和全因子试验设计,探究单一酶和复合酶用于水酶法提取杨梅核仁油的效果,优选确定水酶法提取杨梅核仁油的酶制剂为纤维素酶。采用正交试验对酶法水解提取杨梅核仁油的工艺进行优化,获得其最佳工艺条件为纤维素酶添加量2%、酶解温度50 ℃、pH 4.8、酶解时间2.5 h、料液比1∶4（g/mL）,该条件下的得油率为33.95%,提取率为50.67%。采用气相色谱法对杨梅核仁油的脂肪酸组成进行了分析,结果表明：木洞杨梅核仁油富含不饱和脂肪酸,高达87.22%,其中油酸含量达50.31%,亚油酸含量达到36.64%,亚麻酸含量为0.27%。     

微波预处理水酶法提取杨梅核仁油的研究

以杨梅核仁为原料,先采用微波处理,再用纤维素酶和蛋白酶水解,通过正交试验考察制备杨梅核仁油的最佳条件。结果表明,微波处理的效果优于蒸汽处理和热水浸泡两种预处理方式;影响纤维素酶和蛋白酶酶解杨梅核仁提取杨梅核仁油的主次因素为：复合酶用量＞酶解温度＞酶解时间＞料液比;最佳条件为：复合酶用量3.5%、酶解时间90min、酶解温度50℃、料液比1:3,在此条件下总油提取率为53.79%;杨梅核仁油的理化指标符合食用油脂标准;其脂肪酸中不饱和脂肪酸占87.43%,特别是亚油酸含量达46.14%,杨梅核仁油具有较高的营养价值。     

水酶法提取文冠果油工艺的优化

以文冠果仁为原料,利用水酶法提取文冠果油。通过单因素试验及正交试验研究了酶解时间、料液比、酶添加量及酶解温度对文冠果油提取率的影响,并确定了最佳工艺条件。结果表明最佳的工艺条件为:选用碱性蛋白酶,酶解时间5 h,料液比1∶5,酶添加量0.75%,酶解温度50℃。在最佳条件下文冠果油提取率达81.6%。     

二次正交旋转组合设计优化水酶法提取牡丹籽油工艺

以牡丹籽为原料,采用水酶法提取牡丹籽油。通过单因素试验,研究酶解温度、酶解时间、酶添加量、液料比对牡丹籽油提取率的影响,在此基础上,采用二次正交旋转组合试验对提取工艺条件进行优化。结果表明,各因素对牡丹籽油提取率的影响强弱顺序依次为酶解温度、液料比、酶添加量、酶解时间,水酶法提取牡丹籽油的最优工艺条件为:酶解温度52℃、液料比3∶1、酶添加量3.6%(以牡丹籽质量计)、酶解时间4 h,在此条件下牡丹籽油提取率可达92.8%。     

水酶法提取番木瓜籽油工艺及其氧化稳定性分析

以番木瓜籽为原料,通过单因素试验和正交试验研究不同酶种类、酶解时间、料液比、酶添加量、酶解温度等因素对番木瓜籽油提取率的影响,确定番木瓜籽油提取的最佳工艺条件,并以番木瓜籽油过氧化值为评价指标,考察温度、光照、抗氧化剂对番木瓜籽油氧化稳定性的影响。结果表明,番木瓜籽油的最佳提取条件为：选用中性蛋白酶,酶添加量2.5%、酶解时间5 h、料液比1∶7、酶解温度45 ℃。在此条件下,番木瓜籽油的提取率为85.73%。温度、光照、氧气均会引起贮藏过程中番木瓜籽油过氧化值的升高。添加抗氧化剂可明显提高番木瓜籽油的氧化稳定性,其中叔丁基对苯二酚的抗氧化效果最好。     

果胶酶酶法提取亚麻籽油工艺条件优化北大核心CSCD

为提高亚麻籽油提取率,以亚麻籽为原料,采用果胶酶酶法提取亚麻籽油。采用单因素实验探讨了料液比、酶解温度、酶解时间对亚麻籽油提取率的影响,在此基础上采用响应面法对果胶酶酶法提取亚麻籽油的工艺条件进行了优化。结果表明,果胶酶酶法提取亚麻籽油的最佳工艺条件为料液比1∶5、果胶酶添加量3%、酶解温度56℃、酶解时间6 h,在此条件下亚麻籽油提取率为85.64%。采用果胶酶可以有效提取亚麻籽油。     

酶法提取绿豆淀粉工艺研究

以绿豆为原料,对酶法提取绿豆淀粉工艺进行研究。通过单因素试验,研究酶解温度、酶解时间、蛋白酶添加量、料液比对淀粉提取率影响;通过四因素三水平正交试验确定酶法提取绿豆淀粉工艺最佳参数为:酶解温度46℃、酶解时间4.5 h、蛋白酶添加量700 U/g、料液比1∶3;在此条件下,绿豆淀粉提取率为96.97%。     

超声波辅助酶法优化黄精多糖提取工艺的研究

该文主要以始兴黄精为原料,纯净水为提取溶剂,采用超声波辅助酶法提取黄精多糖,通过单因素试验研究复合酶添加量、酶解时间、酶解温度和料液比等因素对黄精多糖提取率的影响,并对其最佳工艺进行正交试验优化。结果表明,超声波辅助酶法提取黄精多糖的最佳工艺条件为:复合酶添加量6%、酶解温度65℃、酶解时间55 min、料液比1∶30(g/mL),在此工艺条件下得到黄精多糖的提取率为25.63%。     

酶法提取香芋淀粉工艺研究

以香芋为原料,对酶法提取香芋淀粉工艺进行研究。通过单因素试验,研究酶解温度、酶解时间、纤维素酶添加量、料液比对淀粉提取率影响;通过L9(34)正交试验确定香芋淀粉酶法提取最佳工艺参数为:酶解温度35℃、料液比1∶4、纤维素酶添加量0.6%、酶解时间4 h。在此工艺条件下,香芋淀粉提取率为90.23%。该法提取的香芋淀粉无二氧化硫残留,不存在碱液污染问题。     

海洋微藻藻油的提取工艺研究

对水酶法提取海洋微藻藻油的提取工艺进行了研究。通过比较,确定复合蛋白酶为水解酶,并考察了酶添加量、料液比、酶解时间以及提取温度对海洋微藻藻油提取率的影响,并确定最佳提取工艺为:酶添加量2.0%,料液比1∶25,酶解时间2.0 h,提取温度为45℃。在此最佳条件下,藻油提取率可达17.1%。     

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.     

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.     

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.     

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.     

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.