Structure and rheology of the κ-carrageenan/locust bean gum gels

The structure and interaction of κ-carrageenan and locust bean gum (LBG) has been studied using rheology, cryo-SEM, conductivity and syneresis characterization. The rheological behaviour of the binary system has been characterized using both compression and shear measurements. Elimination of slip in the shear measurements yields G′ values of the order 10,000–30,000 Pa for a 1% κ-carrageenan gel in 0–0.2 M added KCl. These values are higher than previously reported. No synergistic peak was found with the addition of LBG as has been previously reported. The measured modulii for these gels yields a Poisson's ratio of 0.5. Compression rupture stress and strain were also monitored. The rupture measurements do show a synergistic peak indicating that the interaction does occur and is important at high strain amplitudes. The gel points as determined by conductivity for these systems show a decrease in temperature with increasing LBG concentration, which is consistent with rheological measurements. Syneresis results are reported for the range of κ-carrageenan/LBG ratios. The syneresis shown by the mixtures is the same as that shown by the same concentration of κ-carrageenan. Structures of the gels as determined by cryo-SEM are also reported. Characteristic length scales in these systems are of the order of tens of microns and show little change with LBG concentration. The reduction in the characteristic length scale with increasing LBG concentration is discussed in terms of the rheological behaviour.     

凝胶珠造粒机旋流分离槽的设计计算

旋流分离槽是分离密度小于凝固液的凝胶珠的设备。本文结合实例介绍了这种旋流分离槽设计中有关的计算方法。     

模糊数学法在稻米增香效果评定中的应用

应用模糊数学理论建立了一套大米增香剂对普粳米增香效果的评定方法，并用ＧＣ－ＭＳ方法验证。该评定方法成为大米增香剂研究和检测的重要手段之一。     

Effect of ripening stage on thiamin and riboflavin levels in lupin, pea and faba bean seeds

 Seeds of yellow pea lupin (Lupinus luteus L., cv. Juno), pea (Pisum sativum L., cv. Ergo) and faba bean (Vicia faba sp. minor Harz., cv. Tibo) were harvested at different stages of seed maturity. Changes in thiamin and riboflavin levels during growth and maturation were studied. The results obtained showed that thiamin and riboflavin were found in high abundance early in the development of lupins and peas, but that their content decreased during maturation. The thiamin content of faba bean seeds increased from 33 to 47 days after flowering (DAF), then a decrease was observed until 61 DAF; however, no significant differences between these levels in faba bean seeds harvested from 61 to 89 DAF were found. The riboflavin content of faba beans increased after 54 DAF, and no significant changes were observed between then and 89 DAF. The thiamin and riboflavin contents in lupin, pea and faba bean seeds during development were fitted to modelling curves in order to predict the vitamin content at different stages of maturity. Received: 17 July 1997     

水源水质标准中嗅味标准的研究

在我国现有的《生活饮用水水源水质标准》(CJ3020-93)标准中并未对嗅味做定性和定量的规定。嗅味层次分析方法能够对水样中的嗅味种类以及嗅味强度做出定性和定量化的判断,通过嗅味层次分析方法以及SPME-GC/MS化学分析的结果,给出了饮用水嗅味的推荐值。按不同水源地类型对二甲基异莰醇(2-MIB)的标准进行了研究,综合考虑感官分析和化学分析结果,水厂可处理程度以及消费者可接受情况,给出2-MIB标准的推荐值,一级、二级水源地的标准推荐值为10 ng/L,三级水源地的标准推荐值为50 ng/L。二甲基异莰醇(2-MIB)嗅味标准推荐值的给出在一定程度上对水源地的划分又提供了一个参考依据,开辟了水质感官分析的新思路,为我国城市水源中2-MIB含量的划分提供了参考。     

生活污水对蚕豆根尖细胞致畸效应的研究

以蚕豆根尖为材料,采用蚕豆根尖细胞的微核试验和染色体畸变试验方法,研究不同取样点生活污水对蚕豆根尖细胞的致畸效应.结果表明:生活污水能诱发微核率升高,而且在一定范围内,其微核率随污染物浓度升高而增加,但高于一定浓度后有下降趋势;不同取样点的污水均使蚕豆根尖细胞有丝分裂指数下降;生活污水还能诱导蚕豆根尖细胞产生较高频率的染色体畸变.所以生活污水蚕豆根尖细胞具有明显的致畸效应.     

Physicochemical,nutritional and functional properties of marama bean flour

Marama bean is a protein-rich, underutilised, drought-tolerant legume in sub-Saharan Africa. Its utilisation may be increased through value addition into protein-rich flours. Defatted flour from unheated and dry-heated (150 °C/20 min) whole marama beans (UMF and HMF) were analysed for physicochemical and protein-based functional properties. Heating significantly increased in vitro protein digestibility of marama bean flour. Of functional importance are the high levels of tyrosine present in marama bean flours. Heating significantly reduced protein solubility and emulsifying capacity of marama bean flours whilst water absorption capacity was improved. Foaming capacity was not affected by heating. UMF could be useful in food systems requiring high emulsifying capacity, but would not be suitable for applications requiring high water absorption and foaming capacity. Due to its high protein contents, marama bean flour could be used to increase the protein quality of cereal-based foods to help alleviate protein-energy nutrition in the region.     

Effects of lipase,lipoxygenase, peroxidase and free fatty acids on volatile compound found in boiled buckwheat noodles

BACKGROUND: Relationships between buckwheat (Fagopyrum esculentum Moench) flour lipase, lipoxygenase and peroxidase activity, along with levels of individual free fatty acids (FFAs) and levels of headspace volatile compounds of boiled buckwheat noodles, were investigated for 12 different buckwheat varieties. Enzyme activities and FFA levels in flour were correlated with their respective varietal arrays of boiled noodle headspace volatile compounds, measured by gas chromatography–mass spectrometry. RESULTS: The volatiles hexanal, tentative butanal, tentative 3‐methylbutanal and tentative 2‐methylbutanal showed significant positive correlation with one another, indicating that they may be generated through similar mechanisms. These important volatile components of buckwheat flavor were also positively correlated with lipase and/or peroxidase activity, indicating that enzymatic reactions are important in flavor generation in boiled buckwheat noodles. On the other hand, pentanal, which showed no significant correlation with any enzyme activity, showed a significant positive correlation to the levels of C18:2 and C18:3 FFAs, suggesting the existence of a ‘non‐enzymatic’ and/or ‘uncertain enzymatic pathway’ for flavor generation in boiled buckwheat noodles. CONCLUSION: Lipase and peroxidase in buckwheat flour are important for flavor generation of boiled buckwheat noodles. This information is important for increasing desirable flavor of buckwheat products as well as for selecting varieties with improved flavor. Copyright © 2010 Society of Chemical Industry     

Hanseniaspora opuntiae, Saccharomyces cerevisiae, Lactobacillus fermentum, and Acetobacter pasteurianus predominate during well-performed Malaysian cocoa bean box fermentations,underlining the importance of these microbial species for a successful cocoa bean fermentation process

Two spontaneous Malaysian cocoa bean box fermentations (one farm, two plantation plots) were investigated. Physical parameters, microbial community dynamics, yeast and bacterial species diversity [mainly lactic acid bacteria (LAB) and acetic acid bacteria (AAB)], and metabolite kinetics were monitored, and chocolates were produced from the respective fermented dry cocoa beans. Similar microbial growth and metabolite profiles were obtained for the two fermentations. Low concentrations of citric acid were found in the fresh pulp, revealing low acidity of the raw material. The main end-products of the catabolism of the pulp substrates glucose, fructose, and citric acid by yeasts, LAB, and AAB were ethanol, lactic acid, acetic acid, and/or mannitol. Hanseniaspora opuntiae, Lactobacillus fermentum, and Acetobacter pasteurianus were the prevalent species of the two fermentations. Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus pentosus, and Acetobacter ghanensis were also found during the mid-phase of the fermentation processes. Leuconostoc pseudomesenteroides and Acetobacter senegalensis were among the prevailing species during the initial phase of the fermentations. Tatumella saanichensis and Enterobacter sp. were present in the beginning of the fermentations and they could be responsible for the degradation of citric acid and/or the production of gluconic acid and lactic acid, respectively. The presence of facultative heterofermentative LAB during the fermentations caused a high production of lactic acid. Finally, as these fermentations were carried out with high-quality raw material and were characterised by a restricted microbial species diversity, resulting in successfully fermented dry cocoa beans and good chocolates produced thereof, it is likely that the prevailing species H. opuntiae, S. cerevisiae, Lb. fermentum, and A. pasteurianus were responsible for it.     

热反应牛肉香精

采用氨基酸、多肽(特别是含硫物)与还原糖进行美拉德反应制备牛肉香精，并对反应条件的各因素如反应时间、反应温度等进行了研究。