紫苏油粉末制备工艺研究

以脱皮、低温压榨紫苏油为芯材,利用乳化和喷雾干燥相结合的方法制备紫苏油粉末.确定的最佳制备工艺条件为:壁材大豆分离蛋白与麦芽糖糊精的比例1:1.2,乳化温度70 ℃,固形物含量25%,芯材壁材比40:100;均质压力50 MPa,均质2次;喷雾干燥进风温度168 ℃,出风温度85℃.该条件下制备的紫苏油粉末微胶囊化效率达95%,表面油含量为1%左右.     

木薯微孔淀粉微胶囊化罗非鱼油技术研究

以自制木薯微孔淀粉和罗非鱼皮胶原蛋白为复合壁材、罗非鱼鱼油为芯材,研究罗非鱼油喷雾干燥制备微胶囊的最佳工艺。结果表明,喷雾干燥用罗非鱼油乳化液的工艺条件为乳化温度55℃、乳化体系pH6.0、均质时间6min、芯材壁材配比1:1.5、罗非鱼皮胶原蛋白质量分数1.1%、乳化剂用量0.15%、固形物质量分数20%、进风温度180℃。依此条件生产的产品,鱼油包埋率达92.1%,微胶囊化效果较满意。     

亚麻籽胶为壁材制备枸杞油微胶囊的研究

采用喷雾干燥法制备枸杞油为芯材、亚麻籽胶为壁材的微胶囊,并以微胶囊化效率和含油率为考察指标,考察了制备工艺。结果表明,最佳微胶囊原料配方为:壁材与芯材的比例为(m:m)2:3;最佳喷雾干燥工艺条件:进风温度为180℃,出风温度为70℃,雾化器转速24000r/min,进料速度为46.21mL/min。在此工艺条件下枸杞油的微胶囊化效率为93.29%,含油率为45.62%。     

乳脂微胶囊的制备

以乳脂包埋率为主要指标,采用单因素试验和响应面分析法研究壁材配比、芯壁比、固形物中乳化剂的添加量和固形物浓度对乳脂微胶囊化效果的影响,并确定了喷雾干燥法制备乳脂微胶囊产品的工艺条件。结果表明:乳脂微胶囊化的最佳配方为,壁材为乳清蛋白和麦芽糊精,二者质量比1∶2.6,芯壁质量比1∶3,乳化剂添加量为3%,固形物浓度为23.5%;喷雾干燥的最佳条件为,进风温度170℃,出风温度80℃,均质压力40 MPa,微胶囊化乳脂的包埋率93%以上。     

辛烯基琥珀酸淀粉酯包埋肉桂精油微胶囊的研究

以辛烯基琥珀酸淀粉酯为壁材,利用喷雾干燥法制备了肉桂精油微胶囊.探讨了固形物含量、芯壁比、均质时间、均质温度、进风温度、进料速度、出风温度对微胶囊化效果的影响,经过单因素实验,确定了最佳工艺条件.实验结果表明,均质时间180 s,芯壁比1:4,固形物含量30％,均质温度50℃.肉桂精油最佳微胶囊化的最佳喷雾干燥条件为进风温度198℃,出风口温度100℃,进料速度55 mL/min.所获得的肉桂精油微胶囊产品中精油的含量为92.76％.     

碳酸氢钠的微胶囊化

采用喷雾干燥法,研制了以乙基纤维素和单甘酯为壁材,以碳酸氢钠为芯材的微胶囊化产品.结果表明以乙基纤维素作为壁材制得的微胶囊化碳酸氢钠产品具有较高的产率和效率,其微胶囊化的工艺参数为喷雾干燥进风温度190℃,出风温度100℃,固形物含量25%,芯材与壁材的比例为83∶17.     

猕猴桃籽油微胶囊的制备及稳定性研究

以猕猴桃籽油为芯材,玉米肽为壁材,吐温-20为乳化剂,采用喷雾干燥法制备微胶囊。优化得到最佳工艺条件为:芯材与壁材配比1∶2(质量比),固形物浓度(质量分数) 15%,喷雾干燥温度160℃,高速乳化剪切转速6 000 r/min。在最佳工艺条件下,猕猴桃籽油微胶囊包埋率为94. 06%。对微胶囊产品进行了理化性质、电镜、红外光谱分析和稳定性研究,表明产品具有良好的溶解性和贮存稳定性。     

栝蒌子油微胶囊化研究

栝蒌子油中的多不饱和脂肪酸对光和热都比较敏感,极易氧化变质,油脂的氧化不仅会使其失去应有的功效性,而且还会产生对人体有害的物质。研究采用喷雾干燥法对栝蒌子油进行微胶囊化处理,保持和稳定其生理活性。研究结果表明,在微胶囊化生产过程研究中,选择麦芽糊精和阿拉伯胶作为复合壁材,对微胶囊包埋率影响大小为芯材与壁材配比>复合壁材配比>总固形物含量。正交试验所得微胶囊最佳配比为阿拉伯胶与麦芽糊精的配比1∶1,芯材与壁材比2∶3,总固形物质量分数30%。喷雾干燥的最佳工艺条件为进风温度180℃,出风温度80℃,均质压为35 MPa。     

以改性淀粉为壁材制备微胶囊化薄荷油

采用两种辛烯基琥珀酸酯化淀粉HI-CAP100和N—LOK为壁材，薄荷油为芯材，通过喷雾干燥法制备微胶囊化薄荷油，研究了不同壁材和不同薄荷油载量对微胶囊化产品的产率、效率和保留率的影响。通过正交试验优化了微胶囊化工艺条件，结果表明，以HI—CAP100为壁材、薄荷油栽量为质量分数40％的微胶囊化薄荷油产品的最佳工艺条件为：固形物质量分数45％。均质压力35MPa、喷雾干燥进风温度195℃。采用差示扫描量热分析法测定HI-CAP100为壁材的微胶囊化薄荷油产品的玻璃化转变温度为53℃，因此以辛烯基琥珀酸酯化淀粉为壁材制备的微胶囊化薄荷油产品在室温下具有良好的贮存稳定性。     

亚油酸的微胶囊化研究

研究了喷雾干燥法微胶囊化亚油酸的工艺。选用HI-CAP100为主要壁材,并以微胶囊化效率为响应值,用响应面分析法(RSA)对亚油酸微胶囊化工艺进行了优化,确定的最优工艺参数为:溶液固形物含量为40%,经一级均质(压力为26.5 MPa),在进风温度为190℃,出风温度为90℃的条件下进行喷雾干燥,产品中亚油酸的载量可达50%,微胶囊化效率为92.11%。     

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.     

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.     

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.     

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.