超临界萃取技术及其在食品工业中的应用进展

本文概述了超临界二氧化碳萃取技术,简要介绍了其在食品工业中的最新运用动态,并对超临界二氧化碳萃取技术作了展望。     

超临界二氧化碳法萃取桑叶中总黄酮工艺研究

为了探索超临界二氧化碳法萃取桑叶中总黄酮提取的最佳方案,利用超临界二氧化碳萃取技术,依次用响应面法考查萃取压强、萃取温度、萃取时间以及夹带剂无水乙醇的流速对桑叶中总黄酮得率的影响,优选出桑叶黄酮类化合物在使用超临界萃取装置时提取的最佳工艺。结果显示:响应面法的最佳萃取条件为:压力26 MPa,温度50℃,时间3 h,流速2.5 m L/min,最佳条件下总黄酮得率为6.21%±0.05%。     

超临界CO2萃取烟叶中茄尼醇的工艺研究

采用超临界二氧化碳萃取烟叶中的茄尼醇,考察了萃取过程温度、压力、二氧化碳流量、萃取方式、夹带剂种类及其用量对萃取过程的影响。采用四因素三水平的正交设计,以茄尼醇的提取率为指标,对萃取条件进行了优化。并建立了能较准确测定烟叶中游离茄尼醇含量的方法,采用高效液相色谱对萃取产物进行了分析。以探索提高提取率的方法,为其工业化生产提供参考。结果表明:最佳萃取工艺条件为:甲醇为夹带剂,萃取温度45℃,萃取压力25MPa,CO2流量15kg·h-1。在最佳工艺条件下茄尼醇的提取率为:92.1%。     

超临界二氧化碳连续萃取脱水奶油的填充柱性能研究

奶油通常用以制造白脱和其他乳制品,由于某些限制,需要把奶油分级。超临界液体萃取可为脱水奶油的分级和降低胆固醇起到积极的作用。超临界液体萃取不涉及添加剂、表面活性剂和有机溶剂;二氧化碳自身无毒、价廉、不易燃烧。除此之外,超临界液体萃取在低温下进行分离,传质快速、溶剂残留量低。因此,超临界二氧化碳萃取是食品工业中的一种理想方法。     

正交实验法优化超临界二氧化碳萃取桑叶总黄酮

探索采用超临界CO_2法萃取桑叶中总黄酮提取的最佳方案。利用超临界二氧化碳萃取技术,依次用正交实验方法考查萃取压强、萃取温度、萃取时间以及夹带剂流速对于桑叶中总黄酮得率的影响,优选提取桑叶黄酮类化合物提取的最佳工艺条件。结果显示,正交实验的最佳萃取条件为:萃取压强为25 MPa,萃取温度为40℃,萃取时间为3 h,夹带剂无水乙醇流速为2.5 mL/min,该条件下,总黄酮得率为6.19%±0.26%,可重复性良好。采用超临界二氧化碳萃取桑叶中黄酮类物质的总黄酮提取率较高,为进一步开发桑叶实验提供了理论和实验依据。     

超临界CO2萃取烟叶中茄尼醇的工艺研究

采用超临界二氧化碳萃取烟叶中的茄尼醇,考察了萃取过程温度、压力、二氧化碳流量、萃取方式、夹带剂种类及其用量对萃取过程的影响。采用四因素三水平的正交设计,以茄尼醇的提取率为指标,对萃取条件进行了优化。并建立了能较准确测定烟叶中游离茄尼醇含量的方法,采用高效液相色谱对萃取产物进行了分析。以探索提高提取率的方法,为其工业化生产提供参考。结果表明：最佳萃取工艺条件为：甲醇为夹带剂,萃取温度45℃,萃取压力25 MPa,CO₂流量15 kg·h^-1。在最佳工艺条件下茄尼醇的提取率为：92.1%。     

秋橄榄果实中番茄红素的超临界萃取技术研究

秋橄榄果实中番茄红素含量丰富。利用超临界二氧化碳技术萃取秋橄榄中的番茄红素,对影响萃取的诸因素,如萃取压力、萃取温度、萃取时间、夹带剂等进行研究,并进一步用响应曲面法优化萃取工艺条件。结果表明：丙酮作为夹带剂效果最佳,优化后的最佳萃取工艺条件是萃取压力37MPa,萃取温度52℃,萃取时间3．8h。     

陕西野生啤酒花染色体形态的研究

作者观察了陕西野生啤酒花的染色体数目和形态,分析了这种野生啤酒花及栽培啤酒花的核型,为植物分类及啤酒花育种工作提供了资料。     

超临界二氧化碳萃取鸢尾油的工艺条件研究

本文采用L9（3^4）正交实验考察了二氧化碳超临界萃取中萃取压力、萃取温度和萃取时间对鸢尾精油提取率的影响。结果表明各影响因子的影响顺序为：压力〉时间〉温度;当原料的颗粒度为60-80目、CO2流量为20．0m^3/h时,用超临界二氧化碳萃取鸢尾精油的最佳工艺条件为：萃取压力26．0MPa,萃取温度55．0℃,萃取完成时间为2．5h,此条件下鸢尾香根中鸢尾油的萃取率高达12．71％,得到的精油中鸢尾酮的含量为39．95％,与索氏法和微波提取法相比,超临界萃取具有提取率高和产品质量好的优点。     

超临界CO2提取甘草地上部分总黄酮

采用单因素试验对甘草地上部分(茎叶)的超临界CO2提取工艺进行了研究。实验考察了压力、萃取时间、温度及CO2流量对甘草地上部分总黄酮提取率的影响,以总黄酮提取率和含量为指标,系统的研究了超临界二氧化碳萃取法提取甘草地上部分总黄酮的提取效果。得出的最佳工艺参数为:采用40-60目原料,80%乙醇为夹带剂,萃取时间:1.5 h;萃取压力:30.0 MPa;萃取温度:50℃;CO2流量:10 kg.h-1;分离压力:5.8 MPa;分离温度:40℃。实验结果表明超临界二氧化碳萃取甘草总黄酮的提取率2.09%,含量5.42%,工艺具有提取率高,纯度高的特点,为规模化生产甘草总黄酮的提取提供了研究基础。     

Characterization of a highly hop-resistant Lactobacillus brevis strain lacking hop transport

Resistance to hops is a prerequisite for lactic acid bacteria to spoil beer. In this study we analyzed mechanisms of hop resistance of Lactobacillus brevis at the metabolism, membrane physiology, and cell wall composition levels. The beer-spoiling organism L. brevis TMW 1.465 was adapted to high concentrations of hop compounds and compared to a nonadapted strain. Upon adaptation to hops the metabolism changed to minimize ethanol stress. Fructose was used predominantly as a carbon source by the nonadapted strain but served as an electron acceptor upon adaptation to hops, with concomitant formation of acetate instead of ethanol. Furthermore, hop adaptation resulted in higher levels of lipoteichoic acids (LTA) incorporated into the cell wall and altered composition and fluidity of the cytoplasmic membrane. The putative transport protein HitA and enzymes of the arginine deiminase pathway were overexpressed upon hop adaptation. HorA was not expressed, and the transport of hop compounds from the membrane to the extracellular space did not account for increased resistance to hops upon adaptation. Accordingly, hop resistance is a multifactorial dynamic property, which can develop during adaptation. During hop adaptation, arginine catabolism contributes to energy and generation of the proton motive force until a small fraction of the population has established structural improvements. This acquired hop resistance is energy independent and involves an altered cell wall composition. LTA shields the organism from accompanying stresses and provides a reservoir of divalent cations, which are otherwise scarce as a result of their complexation by hop acids. Some of the mechanisms involved in hop resistance overlap with mechanisms of pH resistance and ethanol tolerance and as a result enable beer spoilage by L. brevis.     

Characterization of a Highly Hop-Resistant Lactobacillus brevis Strain Lacking Hop Transport

Resistance to hops is a prerequisite for lactic acid bacteria to spoil beer. In this study we analyzed mechanisms of hop resistance of Lactobacillus brevis at the metabolism, membrane physiology, and cell wall composition levels. The beer-spoiling organism L. brevis TMW 1.465 was adapted to high concentrations of hop compounds and compared to a nonadapted strain. Upon adaptation to hops the metabolism changed to minimize ethanol stress. Fructose was used predominantly as a carbon source by the nonadapted strain but served as an electron acceptor upon adaptation to hops, with concomitant formation of acetate instead of ethanol. Furthermore, hop adaptation resulted in higher levels of lipoteichoic acids (LTA) incorporated into the cell wall and altered composition and fluidity of the cytoplasmic membrane. The putative transport protein HitA and enzymes of the arginine deiminase pathway were overexpressed upon hop adaptation. HorA was not expressed, and the transport of hop compounds from the membrane to the extracellular space did not account for increased resistance to hops upon adaptation. Accordingly, hop resistance is a multifactorial dynamic property, which can develop during adaptation. During hop adaptation, arginine catabolism contributes to energy and generation of the proton motive force until a small fraction of the population has established structural improvements. This acquired hop resistance is energy independent and involves an altered cell wall composition. LTA shields the organism from accompanying stresses and provides a reservoir of divalent cations, which are otherwise scarce as a result of their complexation by hop acids. Some of the mechanisms involved in hop resistance overlap with mechanisms of pH resistance and ethanol tolerance and as a result enable beer spoilage by L. brevis.     

Test-retest reliability of 4 single-leg horizontal hop tests

The purpose of this study was to determine the test-retest reliability of 4 single-leg horizontal hop tests (i.e., single hop for distance, triple hop for distance, crossover hop for distance, and 6-m hop for time), with a time interval of approximately 4 weeks separating the 2 testing sessions. Eighteen healthy, young, adult men, all cadets enrolled at the U.S. Air Force Academy, Colorado, performed the single hop for distance, the triple hop for distance, the crossover hop for distance, and the 6-m hop for time during 2 testing sessions separated by 31.2 +/- 0.4 days. Reliability data for each of the single-leg hop tests were studied through a repeated measures analysis of variance, intraclass correlation coefficients (ICCs), and standard errors of measurement (SEMs). The ICCs ranged from 0.92 to 0.97 for the 4 single-leg hop tests. The SEMs for the single-leg hop tests that assessed the distance hopped ranged from 4.61 to 17.74 cm. The SEM for the 6-m hop for time test was 0.06 seconds. No significant differences were noted when the mean scores of the 2 test trials were compared by a repeated measures analysis of variance for any of the single-leg hop tests. These results indicate that the single-leg hop tests examined in this study offer strength and conditioning professionals a reliable method to assess the single-leg horizontal hopping capabilities of healthy, young, adult men, with intervals of approximately 4 weeks between testing sessions.     

Developmental Morphology of Hop Stunt Viroid-infected Hop Plants and Analysis of Their Cone Yield1)

Infection of hop plants with hop stunt viroid (HSV) results in the retardation of the growth rate except for the rate of leaf emergence and the disappearance of the fold-like structure over the epidermal cell. Mature cones from HSV-infected hop plants remained small-sized and the content of α-acid was half to one third of that of HSV–free hop cones. In HSV-infected hop cones, the lupulin glands are distributed most abundantly on the bracteoles and the perianths and their numbers are reduced by at least 60% of that in the HSV-free control. Scanning electron micrographs confirm that most of the lupulin glands on bracteoles from HSV-infected hop cones shrivel severely, but not those from HSV-free hop cones. They also reveal that the lupulin glands on the perianths from both, HSV-free and HSV–infected hop cones become withered. Moreover, spherical granules (1.2 to 1.9μm in diameter) were not observed on the surface of the lupulin glands from HSV-infected hop cones.     

Survival of Hop Stunt Viroid in the Hop Garden1)

A lot of 105 specimens from 25 families including weeds or wild plants which had grown naturally in the severely infested hop garden were tested for detecting reservoir plants for hop stunt viroid (HSV). HSV was detected in hop plants only. Susceptibility tests with various cultivated plants including 14 families indicated that hop and Humulus japonicus developed visible symptoms, while tomato was symptomless. When infected hop plant residues, leaves and cones, were left to be weather-beaten, infectivity of HSV was completely lost within 3 months. No transmission through the pollen or the ovule was demonstrated. HSV could survice in root systems of hop plants during the winter months. Based on these results, the route of HSV survival in the hop garden was discussed.     

啤酒花抗性机制的研究进展

酒花苦味酸是构成啤酒风味的重要组分,也是啤酒生产过程中的天然抑菌剂,酒花苦味酸通过降低pH梯度而抑制啤酒花敏感菌生长。研究发现,啤酒花抗性菌是通过膜上转运蛋白将酒花苦味酸泵出细胞外,以降低膜上的质子流速,维持了细胞内的pH梯度。结合近年来酒花抗性相关研究结果,讨论了细胞膜上酒花抗性相关组分与酒花抗性间的关系,提出了酒花抗性机制的模型。     

Development of novel EST-derived resistance gene markers in hop (Humulus lupulus L.)

Although sources of resistance to major pathogens exist in cultivated hop germplasm, little effort has been invested to date in developing resistance-linked markers. The aim of this study was to design and evaluate resistance gene analogs (RGAs) potentially useful for marker-assisted selection towards novel resistant hop cultivars. A set of 34 putative hop RGAs was retrieved by screening publicly available hop expressed sequence tags (ESTs) for conserved sequence motifs of common resistance protein domains. Seventeen of these were identified as putative RGAs by BLAST analyses. Exon/intron boundary prediction enabled re-sequencing of 24 EST-RGAs, allowing the acquisition of approximately 5 kbp of novel intronic sequence and 8 kbp of re-sequenced exons. Fifteen EST-RGAs exhibited polymorphisms and were added to a framework linkage map of hop. In addition to providing EST-derived markers potentially useful for resistant hop cultivar development, this study provides valuable insights into the utility of targeting hop introns for marker development.     

VIP provides cellular protection through a specific splice variant of the PACAP receptor: a new neuroprotection target

Vasoactive intestinal peptide (VIP) was known to provide neuroprotection. Three VIP receptors have been cloned: VPAC1, VPAC2 and PAC1. A specific splice variant of PAC1 in the third cytoplasmatic loop, hop2, was implicated in VIP-related neuroprotection. We aimed to clone the hop2 splice variant, examine its affinity to VIP and investigate whether it mediates the VIP-related neuroprotective activity. The PAC1 cDNA was cloned from rat cerebral astrocytes. Using genetic manipulation the hop2 splice variant was obtained, then inserted into an expression vector and transfected into COS-7 cells that were used for binding assays. Results showed that VIP bound the cloned hop2 splice variant. Stearyl-neurotensin(6-11) VIP(7-28) (SNH), an antagonist for VIP, was also found to bind hop2. In addition, VIP protected COS-7 cells expressing hop2 from oxidative stress. Parallel assays demonstrated that VIP increased cAMP accumulation in COS-7 cells expressing hop2. These results support the hypothesis that hop2 mediates the cytoprotective effects attributed to VIP.