双酶酶解鸽胸肉工艺优化及抗氧化性评价

目的:根据鸽肉酶解产物的水解度与抗氧化性,探究最佳酶解工艺条件。方法:以水解度与ABTS自由基清除率为评价指标,探讨酶种类、加酶量、pH值、酶解温度、酶解时间、料液比和酶配比等因素对鸽胸肉酶解物抗氧化活性的影响,并对最优条件下制备的鸽肉酶解物进行总氨基酸含量测定。结果:中性蛋白酶与碱性蛋白酶为最佳复配用酶,m_{中性蛋白酶}∶m_{碱性蛋白酶}为3∶1、加酶量800 U/g、料液比(m_鸽肉∶m_复合酶)为1∶1.5、pH值7.5、酶解温度50℃、酶解时间3 h,所得样品在1 mg/mL质量浓度下对ABTS自由基清除率为36.10%,与预测值相近。最佳工艺所制得的肽中共检出16种氨基酸,总氨基酸含量的47.97%为必需氨基酸,抗氧化活性氨基酸的占比为29.27%。结论:该条件下制备的鸽肉肽具有一定的抗氧化活性与营养价值。     

姬松茸抗氧化酶解液的制备

目的:研究制备姬松茸抗氧化酶解液的工艺条件,并分析酶解液的营养成分。方法:将木瓜蛋白酶、纤维素酶、果胶酶按m_{木瓜蛋白酶}∶m_纤维素酶∶m_果胶酶为3∶4∶4制备复合酶,酶解姬松茸子实体;采用响应面试验优化姬松茸酶解工艺。结果:复合酶水解姬松茸的最佳工艺为复合酶添加量0.5%,酶解pH 6.2,酶解温度49℃,酶解时间147 min,该条件下,当姬松茸酶解液质量浓度为2.0 mg/mL时,其对DPPH自由基的清除率为69.15%,表现出很强的抗氧化活性。酶解液中蛋白质含量为(1 013.83±25.11) mg/100 mL,粗脂肪含量为(150.17±1.21) mg/100 mL,总糖含量为(721.41±8.74) mg/100 mL,多糖含量为(138.83±1.66) mg/100 mL,游离氨基酸含量为(800.94±12.36)mg/100 mL,其中必需氨基酸占40.22%。结论:采用复合酶法制备的姬松茸酶解液具有较强的抗氧化活性和较高的营养价值,可开发为功能性食品。     

有色米乳酸饮料发酵工艺优化及抗氧化和降血糖活性研究

目的:开发具有较好抗氧化及降血糖活性的有色米乳酸饮料产品。方法:以黑米和紫米为主要原料,考察有色米比例构成、乳酸菌发酵粉添加量、发酵时间、料液比对有色米乳酸饮料感官评分值、总酚含量、铁离子还原能力、ABTS自由基清除能力、α-葡萄糖苷酶抑制率的影响。结果:有色米乳酸饮料最佳发酵工艺条件为紫米和黑米质量比(m_紫米∶m_黑米)1∶5,料液比1∶8 (g/mL),乳酸菌发酵粉添加量5%,发酵时间40 h,此条件下有色米乳酸饮料感官评分值为83.6±2.51,ABTS自由基清除能力为(145.02±7.88) mmol TE/g·DW,铁离子还原能力(FRAP)为(33.41±1.70) mmol Fe²⁺/g·DW,总酚含量为(4 208.78±281.26)μg GAE/g·DW,α-葡萄糖苷酶抑制率为(13.94±0.01)%。结论:有色米乳酸饮料呈紫红色,口感柔和,酸甜味适中,具有较好的抗氧化活性和α-葡萄糖苷酶抑制活性。     

低共熔溶剂提取绿茶总黄酮及其抗氧化活性

目的:优化低共熔溶剂提取绿茶总黄酮工艺,并评价其抗氧化活性。方法:以总黄酮提取率为考察指标,以低共熔溶剂种类、液料比、提取温度和提取时间为影响因素,采用正交试验优化低共熔溶剂提取绿茶总黄酮工艺参数,并对其抗氧化活性进行评价。结果:绿茶总黄酮的最优提取工艺为以80%乙酰胆碱—乳酸(n_乙酰胆碱∶n_乳酸=1∶1)水溶液为低共熔溶剂,液料比(V_溶剂∶m_绿茶)30∶1(mL/g),提取温度90℃,提取时间75 min,此条件下绿茶总黄酮提取率为1.84%,总黄酮质量浓度为65.8 mg/mL。一定质量浓度范围内,绿茶总黄酮提取液对DPPH自由基和OH自由基的清除能力强于维生素C。结论:以80%乙酰胆碱—乳酸(n_乙酰胆碱∶n_乳酸=1∶1)水溶液为低共熔溶剂提取的绿茶总黄酮具有一定的抗氧化活性。     

基于熵权法和灰色关联度法优选人参—酸枣仁抗氧化活性最佳配比

目的:开发以人参—酸枣仁为原料的相关保健品。方法:应用HPLC、紫外分光光度计对人参、酸枣仁不同配伍比例进行化学成分研究；应用DPPH自由基、ABTS自由基、羟自由基和超氧阴离子自由基清除率分析样品的体外抗氧化活性；同时采用灰色关联度法，以熵权法所得权重为分辨系数进行统计分析，结合性状进行综合评价优选出最佳配伍比例。结果:人参—酸枣仁不同配比的样品的抗氧化活性与总酚酸、酸枣仁皂苷A、斯皮诺素含量呈显著相关关系；m_人参∶m_酸枣仁为1∶1的样品的总酚酸、酸枣仁皂苷A、斯皮诺素含量高于其他配比的，且其抗氧化活性强于其他配比的，说明抗氧化活性的药效物质基础是总酚酸、酸枣仁皂苷A、斯皮诺素。结论:人参—酸枣仁抗氧化活性最佳配比(m_人参∶m_酸枣仁)为1∶1。     

青叶苎麻叶多酚超声辅助提取工艺优化及抗氧化活性研究

优化了青叶苎麻叶多酚的提取工艺参数,并以没食子酸为对照评价了青叶苎麻叶多酚的抗氧化活性。结果表明:优化出的多酚提取工艺参数分别为料液比(m_苎麻∶V_乙醇)1∶33 (g/mL)、乙醇体积分数40%、提取温度42℃,在此条件下青叶苎麻多酚提取量为47.97 mg/g。青叶苎麻叶多酚清除DPPH自由基和ABTS+自由基的IC₅₀值分别为(0.15±0.00),(2.28±0.03)μg/mL,氧自由基吸收能力为(42.41±0.01)g Trolox/g多酚,均明显优于没食子酸,具有良好的抗氧化效果。     

麻糖水发酵工艺优化及抗氧化活性分析

以红薯为原料,感官评分和产酸量为评价指标,经发酵制备麻糖水。通过正交试验优化麻糖水料液比、酒曲接种量、发酵时间、发酵初始pH等工艺条件,比较优化麻糖水与市售麻糖水营养成分、抗氧化活性。结果表明：麻糖水最佳发酵工艺条件为料液比1:3（g/mL）,红薯浆糖度23 °Brix,60 ℃糖液化3 h,酒曲0.19%,pH=4.5,30 ℃发酵9 d。发酵后麻糖水感官综合评分为90分,还原糖含量6.85 g/100 g,总糖7.20 g/100 g,粗蛋白6.65 g/100 g,黄酮0.92 mg/100 g,总游离氨基酸0.27 mg/100 g,DPPH自由基清除率64.60%,总抗氧化力365.47 mmol/L,羟自由基清除率89.99%;市售麻糖水还原糖含量7.84 g/100 g,总糖8.00 g/100 g,粗蛋白1.43 g/100 g,黄酮0.41 mg/100 g,总游离氨基酸0.18 mg/100 g,DPPH清除率80.25%,总抗氧化力446.80 mmol/L,羟自由基清除率41.25%。实验优化麻糖水还原糖、总糖含量、DPPH自由基清除率及总抗氧化力较市售麻糖水低,而粗蛋白、黄酮、总游离氨基酸含量及羟自由基清除率均较市售麻糖水高。综合分析,麻糖水经最佳发酵工艺优化后羟自由基清除率、黄酮含量及总游离氨基酸均高于市售麻糖水,符合中老年人对低糖、高营养产品的选择,因此,选择优化麻糖水更适宜饮用。     

滨海白首乌酸乳的制备及其抗氧化能力

该文以滨海白首乌粉和全脂乳粉为主要原料,通过单因素试验研究白首乌粉添加量、发酵剂接种量、蔗糖添加量及发酵温度对滨海白首乌酸乳的品质和总抗氧化能力的影响,并利用正交试验对其制备条件进行优化,同时研究其贮藏特性。结果表明,全脂乳粉中添加2.0%的滨海白首乌粉和5.0%的蔗糖,接种0.015 U/kg Y450A 发酵剂,40.0 ℃发酵5 h,制备的滨海白首乌酸乳总抗氧化能力为0.129 2 mmol/L,显著高于未发酵和不含滨海白首乌粉的酸乳（P<0.05）,且酸甜适中,风味和口感良好。异丙醇、2,3-丁二酮、正己醇、2-庚酮、仲丁基亚硝酸酯及三乙二醇单乙醚为其主要的风味物质。4 ℃贮藏9 d 后,滨海白首乌酸乳的总抗氧化能力为0.103 5 mmol/L,乳酸菌活菌数为1.57×108 CFU/mL,并保持了良好的感官品质。     

水酶法提取樱桃籽油的工艺及理化性质

目的:优化水酶法提取樱桃籽油工艺,提高樱桃籽利用率。方法:在单因素试验基础上,运用混料设计对混合酶的混合比例进行优化,以确定最佳提取工艺条件,再对樱桃籽油的理化性质进行检测。结果:混合酶法提取樱桃籽油的最优酶解条件为：混合酶(m_维素酶∶m_果胶酶∶m_{酸性蛋白酶}为0.67∶0.10∶0.23)添加量2.0%,液料比(V_蒸馏水∶m_樱桃籽粉)10∶1 (mL/g),酶解温度45℃,pH 4.0,酶解4.0 h,樱桃籽油回收率达到93.18%,实际提取率为28.66%。所得樱桃籽油符合食用油安全标准。结论:混料设计辅助水酶法提取樱桃籽油的工艺具有可行性。     

鲜品香菇柄中多糖闪式提取工艺优化及抗氧化活性研究

目的:开发香菇柄多糖的工业化生产。方法:以多糖得率为指标,采用均匀设计试验优化提取工艺,采用4种方法测定多糖抗氧化活性并与传统的热水浸提法进行比较。结果:闪式辅助热水浸提法提取香菇柄多糖最优工艺条件为闪式提取时间120 s,液料比(V_去离子水∶m_香菇柄)40∶1 (mL/g),热水浸提时间105 min,温度50℃,提取两次,此条件下多糖得率为(5.03±0.22)%,与模型预测值基本一致,是传统热水浸提法的1.82倍;香菇柄多糖具有较强的Fe³⁺还原能力、总抗氧化能力、羟自由基和DPPH自由基清除能力,且呈量效关系;闪式辅助热水浸提法所得多糖抗氧化活性强于传统热水浸提法。结论:闪式辅助热水浸提有利于香菇柄多糖提取,且能保持其抗氧化活性。     

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.