新型中长链甘三酯的制备及其在人造奶油中的应用

以全氢化高芥酸菜籽油(HERO),中链甘三酯(MCT)和棕榈油(PO)的混合油样为原料油,化学法酯交换合成低热量中长链甘三酯(MLCT)。研究了化学酯交换前后混合油样的甘三酯组成、固体脂肪含量及热学性质的变化,并对酯交换产品进行应用测试分析。结果表明:酯交换改善了混合油样的甘三酯组成、固体脂肪含量及热学性质,该酯交换产品可用于人造奶油中。     

利用酯交换法制备零反式脂肪酸人造奶油基料油的研究

极度氢化大豆油为饱和甘三酯,几乎没有双键,故不存在反式酸,将大豆油与极度氢化大豆油按不同比例混合进行酯交换反应可以得到不同固体特征的油脂。利用酯交换油脂代替氢化油做基料,降低反式酸,开发健康营养型的人造奶油,对酯交换油脂的固体含量（SFC）、熔点以及融化和结晶特性进行了分析,为今后的新产品研究和开发提供参考。     

酶促酯交换对棕榈硬脂基塑性脂肪甘三酯组成及物理性能的影响

利用脂肪酶Lipozyme TLIM催化棕榈硬脂(PS)与大豆油(SO)(PS∶SO分别为9∶1,8∶2,7∶3,6∶4,5∶5,wt%)酯交换反应,研究酯交换反应前后混合油脂体系中甘三酯组成的变化及其与油脂物理性能的关系。结果发现,酯交换后油脂中PPP、LLL、POP、PPL、PLL、PLO六种甘三酯含量发生明显变化,其中PPP、LLL含量下降,PPL、PLL、PLO含量增加,而POP除9∶1外,其含量均下降;SSS(S代表饱和脂肪酸)和UUU(U代表饱和脂肪酸)型甘三酯含量下降,而SUU和SUS含量增大,导致油脂熔点和固体脂肪含量(SFC)均不同程度下降,从而可制备不同SFC要求的塑性脂肪。PS∶SO为7∶3、6∶4、5∶5时,酯交换后油脂β’晶型增多,可为人造奶油、速冻专用油脂等塑性脂肪提供理想晶型。      

棕榈油中间分提物在零/低反式脂肪酸人造奶油中的应用

为扩大棕榈油中间分提物(PMF)在零/低反式脂肪酸人造奶油中的应用,对PMF、棕榈油硬脂(PSt)和大豆油的甘三酯组成、结晶及熔化特性进行分析。结果表明:PMF的甘三酯主要由二饱和型及单饱和型甘三酯POP、PLP、POO组成;PSt的甘三酯主要由三饱和型及二饱和型甘三酯PPP、POP组成;大豆油主要由三不饱和型及二不饱和型甘三酯LLL、OLL、PLL等组成。以PMF为主,复配PSt和大豆油作为人造奶油的基料油,可使人造奶油以二饱和型POP等形成β'结晶倾向,一定量的三饱和型甘三酯PPP等提供人造奶油的骨架结构,三不饱和型甘三酯LLL、OLL等填充高熔点甘三酯形成的网格,提高人造奶油的营养特性。PMF、PSt和大豆油三者的质量比为50∶30∶20时表现出良好的相容特性,按照这一质量比制备的人造奶油中的晶型为β'和β共存,且以β'为主,符合人造奶油的结晶及熔化性能要求。     

富含亚油酸塑性脂肪的研制——酯酯交换

以非传统食用(non-traditional edible)羊脂及红花油按不同的比例用酯酯交换的方法研制富含亚油酸塑性脂肪的设想获得成功。羊脂与红花油以70:30的比例制取的起酥油(shortenings)及以45:55比例制取的人造奶油脂肪(margarine oil),其固体脂肪指数(SFI)曲线均符合要求,具有良好的塑性。前者含亚油酸25％以上,约为普通起酥油的四倍;后者含45％以上。多不饱和酸与饱和酸的比率(p/s)达1.4以上,在美国通用人造奶油脂肪的要求(p/s=1.2—1.6)的上限范围,极富营养,味感可口,无油腻感和羊气味。经酯酯交换,脂肪中的维生素E含量损耗殆尽、稳定度下降,但在加入微量的抗氧化剂后,其稳定度即有显著的增强。本文包括用胰脂酶水解方法对酯酯交换前后脂肪甘三酯组分变化的研究。     

不同硬度棕榈油基人造奶油组成及结晶行为研究

对比分析了两个不同硬度棕榈油基人造奶油的甘三酯组成、结晶特性及微观结构,试验表明人造奶油B中饱和脂肪酸含量较高,SUS型甘三酯(POP,PLP)含量偏大,同时含有少量的中碳链甘三酯;X-衍射观察到两个样品中均含有β和β′晶型,但是样品B中β′晶型占主导;SEM图像显示硬度较小的样品显微结构更疏松多孔.     

富含亚油酸塑性脂肪的研制——酯酯交换

以非传统食用(non-trditional edible)羊脂及红花油按不同的比例用酯酯交换的方法研制富含亚油酸塑性脂肪的设想获得成功。羊脂与红花油以70:30的比例制取的起酥油(Shortening)及以45:55比例制取的人造奶油脂肪(margarine oil),其固体脂肪指数(SFI)曲线均符合要求,具有良好的塑性(Plasticity)。前者含亚油酸25％以上约为普通起酥油的四倍。后者含45％以上,多不饱和酸与饱和酸的比率(P/S)达1.4以上,在美国通用人造奶油脂肪的要求(P/S=1.2～1.6)的上限范围,极富营养,味感可口,无油腻和羊膻气味。 经酯酯交换,脂肪中的维生素E含量损耗殆尽,稳定度下降,但在加入微量的抗氧化剂(antioxidant)后其稳定度即有显著的增强。本文包括用胰脂酶水解方法对酯酯交换前后脂肪甘三酯组份变化的研究。     

棉籽油硬脂和全氢化棉籽油硬脂的组成、热性质和微观结构分析

为扩大棉籽油用途，提高其附加值，采用气相色谱、高效液相色谱、低场脉冲核磁共振分析仪、差示扫描量热仪、X-射线衍射仪和偏光显微镜分析了棉籽油改性后的产物棉籽油硬脂(COS)和全氢化棉籽油硬脂(FHCOS)的脂肪酸组成、甘三酯组成、SFC含量、热性质和微观结构。结果表明：COS主要由不饱和脂肪酸和非三饱和的甘三酯组成，FHCOS几乎全部由饱和脂肪酸和三饱和甘三酯组成；随温度升高，COS的SFC不断降低，FHCOS的SFC在温度高于35℃时开始降低，相同温度下FHCOS的固体脂肪含量(SFC)均高于COS的，COS在结晶和熔化过程中均有2个峰，FHCOS有1个峰，FHCOS的熔化和结晶温度均高于COS的；COS在15℃时无明确的晶型及稳定的结构，FHCOS为二倍链长堆积的β′晶型，结晶体为针状或棒状，结晶聚集体为类似玫瑰花状。因此，以COS和FHCOS代替棕榈油作为生产起酥油、人造奶油、黄油等的基料油具有一定的开发和应用前景。     

乳化剂对富含甘油二酯的人造奶油乳化体系结晶行为的影响

以饱和单甘酯和棕榈油(24℃)为原料,采用脂肪酶Lipozyme TL IM催化酯交换反应制备含甘油二酯(31.2%)的人造奶油基料油。利用差示扫描量热仪(DSC)、核磁共振分析仪、偏光显微镜(PLM)和X-射线衍射仪(XRD)等研究不同乳化剂(单硬脂酸甘油酯、蔗糖酯、大豆卵磷脂)对甘油二酯基料油制备的人造奶油结晶行为的影响。结果表明:单硬脂酸甘油酯、大豆卵磷脂和蔗糖酯复配质量比为1∶1∶1(乳化剂含量为1%)时,制得的人造奶油熔点较低,固体脂肪含量满足食品工业人造奶油的要求,在45℃条件下可全部熔化,且晶体细腻均匀,能较好地包裹液油。     

DSC结合HPLC表征糖果人造奶油融化性质的研究

应用差式量热扫描技术(DSC)结合高效液相色谱法(HPLC)分析糖果人造奶油的融化性质,并与传统融化性质研究方法--核磁共振法(NMR)测定固体脂肪指数(SFC)进行比较.结果表明:对于甘三酯组成较为复杂的糖果人造奶油,DSC结合HPLC分析法能够更加直观和准确地分析其融化性质,得出理想的糖果人造奶油DSC融化曲线类型,为今后糖果人造奶油融化性质的研究提供参考.     

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.     

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.     

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.