卡拉胶海藻多糖硫酸酯化技术研究

多糖的抗病毒活性与多糖的分子量大小、硫酸根含量以及空间构象有较大联系,本文对微波辐射制备不同分子量卡拉胶多糖及硫酸酯化修饰技术进行了研究. 1材料与方法 1.1材料 标准多糖(Dextran Standard 270000、80000、12000、5000、1000和DextranBlue),卡拉胶,真空反应器,纳滤系统,凝胶色谱柱. 1.2实验方法 1.2.1微波辐射制备卡拉胶多糖 取一定量卡拉胶加水搅匀,80℃保温15min,使其充分溶解:然后加入一定量H2SO4,750W微波处理10～30min;料液先用碱调节至pH4.5,冷却后调至pH6.0.     

硫酸酯化洋葱多糖的制备及其抗氧化活性的研究

以洋葱为原料,采用水提醇沉法制备洋葱多糖。用浓硫酸法对洋葱多糖进行硫酸酯法修饰,采用硫酸酯取代度为指标,对硫酸酯化反应的浓硫酸与正丁醇的体积比和反应时间进行优化,并对不同浓度的硫酸酯化洋葱多糖进行体外抗氧化实验。结果表明,制备硫酸酯化洋葱多糖的较佳工艺为浓硫酸和正丁醇体积比3∶1,反应时间20min和反应温度0℃,在此条件下多糖硫酸根取代度为0.51。同时,洋葱多糖硫酸酯化改性后可显著提高抗氧化性。     

戊二酸酐酯化κ-卡拉胶的制备及理化性质

以κ-卡拉胶为原料,戊二酸酐为酯化剂,探讨了戊二酸酐酯化卡拉胶（GC）的制备过程中戊二酸酐浓度、反应pH、反应温度、卡拉胶浓度和反应时间对产物取代度的影响,得到制备GC的工艺条件:戊二酸酐浓度4%,反应pH8～8.5,反应温度30 ℃,卡拉胶浓度7.50%,反应时间2 h,取代度为0.077。利用红外光谱、白度仪、粘度仪、扫描电镜和热重分析仪对产物进行表征。结果表明:GC在红外光谱1734 cm?1和在1576 cm?1处峰具有明显的酯羰基和羧基吸收特性,峰值随着取代度的增加更加明显;与原卡拉胶相比,酯化卡拉胶粉末白度略微增加,颗粒表面变得粗糙,表层出现一定凹陷和孔洞,而热稳定性影响不明显;酯化卡拉胶溶液粘度降低,但乳化性及乳化稳定性均得到显著提升（P<0.05）。κ-卡拉胶经戊二酸酐酯化后,改变了其结构与性质,拓宽了κ-卡拉胶的应用范围。     

微波条件对淀粉磷酸单酯取代度的影响及糊化性质研究

微波酯化技术用于淀粉变性反应制备磷酸单酯淀粉。探讨微波加热功率及处理时间对取代度的影响并进行方差分析，结果表明：实验条件下随着反应时间和微波功率的增加，样品DS增大，当工艺参数反应时间为9min，微波加热功率为900W时酯化产物DS最高。影响磷酸单酯取代度的因素主次关系为反应时间〉微波功率，反应时间、微波功率对DS的影响均具有极显著性。酯化淀粉糊化特性分析结果显示：糊透光率、黏度、冻融稳定性及抗凝沉性较原淀粉有显著提高，而抗剪切特性、抗电解质特性与原淀粉相比无明显优势。与传统干热酯化法产物相比较，发现微波技术应用于磷酸单酯的生产，能大大提高反应效率，反应条件更为温和。同等条件下900W，9min微波处理所得制品与传统140℃，120min干热法所得制品DS接近，糊特性相似。     

发酵液中硫酸酯化茯苓多糖(SP)的制备及其结构改性的研究

茯苓菌株HD06-10进行液态发酵培养,获得的茯苓多糖进行硫酸酯化结构改性处理,制备硫酸酯化茯苓多糖(SP),并采用正交设计法优化其制备条件。采用柱层析纯化得到SP精制品,并通过紫外光谱、琼脂糖凝胶电泳和红外光谱对SP进行纯度和理化、结构性质鉴定,结果表明:SP为多糖纯品,符合多糖及其硫酸根反应特征,分子量大约为5000～6000u;SP特性黏数降低,水溶性增加,IR分析有硫酸根的特征吸收峰,说明茯苓多糖的硫酸酯化成功。     

微波辅助合成硫酸化发酵灵芝胞外多糖的研究

多糖的硫酸化修饰能提高多糖的生物活性。从灵芝深层发酵液中获取灵芝胞外多糖,以二甲基甲酰胺为反应溶剂,采用氨基磺酸为酯化剂,探讨了微波辅助加热合成多糖的途径。结果表明,将尿素作为催化剂微波辅助合成硫酸酯化多糖,反应条件温和,取代度可高达2.67。因此微波辅助合成法为获取高取代度硫酸化灵芝多糖开辟了一条新途径。     

机械活化协同微波法制备高取代度柠檬酸酯淀粉

在微波辐射条件下,以不同机械活化时间的木薯淀粉为原料,柠檬酸为酯化剂,氢氧化钠为催化剂制备柠檬酸酯淀粉。以取代度和反应效率为指标,分别探讨机械活化时间、微波功率、微波辐射时间、淀粉含水量、柠檬酸用量及氢氧化钠用量对木薯淀粉柠檬酸酯化反应的影响,并对影响因素进行了正交优化。结果表明,木薯淀粉经机械活化后,对微波功率、微波辐射时间、酯化剂用量、催化剂用量、淀粉含水量的依赖性明显降低,取代度和反应效率均为原木薯淀粉的2倍多。通过正交试验确定了制备柠檬酸酯淀粉的最佳工艺条件:微波功率800 W、微波辐射5.0 min、淀粉含水量35%、柠檬酸质量分数50%、氢氧化钠质量分数6%,所得产品的取代度为0.399 8,反应效率为88.84%。并采用红外光谱和X-射线衍射对木薯淀粉、活化淀粉及高取代度柠檬酸酯淀粉进行了表征。     

均匀设计优化党参多糖硫酸酯合成工艺

用氨基磺酸法对党参多糖进行硫酸化修饰,采用均匀设计U8(43)对党参多糖硫酸酯化工艺进行优化设计,并用氯化钡-明胶法测定硫酸根的取代度。确定了党参多糖硫酸酯化最佳工艺条件:温度为60℃、时间15min、投料比为1:0.04(g/mol)。此种方法能够为多糖硫酸化的进一步研究提供研究参数。     

微波法硫酸酯化枸杞多糖的研究

采用微波辅助的方法对枸杞多糖的硫酸酯化进行研究,改进了枸杞多糖硫酸酯硫酸根含量的测定方法。通过对反应溶剂的种类、多糖残基与酯化试剂的摩尔比、反应温度和时间等因素的正交实验,确定了较佳的硫酸酯化反应条件;在对枸杞多糖硫酸酯硫酸根含量测定方法的研究中,以醋酸钡替代氯化钡,其标准曲线回归性比氯化钡的好,且精密度较高、稳定性较好、安全可靠,是多糖硫酸根含量测定的较理想的方法。     

微波法制备羟丙基多孔玉米淀粉工艺优化

采用微波法对玉米多孔淀粉原料进行处理,经过正交试验优化工艺,制备具有不同取代度的羟丙基玉米多孔淀粉。研究在微波作用下,淀粉乳质量分数、微波处理时间、微波功率以及环氧丙烷用量对产品取代度的影响。结果表明,用微波法制备羟丙基玉米多孔淀粉的最佳反应条件为微波功率300W、环氧丙烷用量(质量分数)6.90%、微波时间3min、淀粉乳质量分数30%,在该条件下制备的羟丙基多孔淀粉的摩尔取代度为0.0103。     

Heat‐induced denaturation impairs digestibility of legume (Phaseolus vulgaris L and Vicia faba L) 7S and 11S globulins in the small intestine of rat

7S globulin from common bean (Phaseolus vulgaris L) and 11S globulin from faba bean (Vicia faba L) were isolated to over 90% purity and the digestibility of the proteins, either in native or denatured (120 °C, 20 min, 1 atm) state, was tested in the small intestine of growing rats in acute (1 h) experiments. Native globulins were well digested (92 and 95% for 7S and 11S proteins, respectively). However, after thermal denaturation, protein digestibility of 7S globulin was reduced to 88%, while that of 11S globulin to only 79%. SDS‐PAGE revealed that high amounts of the intermediate proteolytic products of phaseolin (MW 22 000–27 000 Da) were present in the small intestine of rats after 1 h digestion of the denatured 7S globulin, while protein material in the high MW range (>55 000 Da) were recovered from the 11S globulin. The overall negative charge of unavailable proteins from the 7S globulin was found by anion exchange–FPLC separation to be higher than that of products from the 11S globulin. MALDI‐MS analysis of proteins in the small intestine confirmed the presence of half‐size phaseolin subunits (MW 23 700 Da) as breakdown products from the denatured 7S globulin, and of highly hydrophobic basic subunits (MW 20 000 Da) from the 11S globulin. Copyright © 2004 Society of Chemical Industry     

荔枝果干蛋白质组成及其抗氧化性研究

分析荔枝干果肉蛋白组成并比较不同组份蛋白质的抗氧化性。采用等电点法提取不同组份蛋白质,利用氨基酸自动分析仪测定不同组份蛋白及总蛋白的氨基酸组成,用超高压液相质谱联用系统Q1扫描测定不同等电点组份中小分子蛋白分子量分布,用抗氧化试剂盒测定不同等电点组份蛋白质的抗氧化性。试验结果表明荔枝浆浸泡2 h为蛋白质的最佳提取时间,测得pH 3.5、pH 5.5、pH 6.5和pH 7.5为荔枝蛋白的4个等电点,且4个等电点组份蛋白含量分别占果肉总蛋白的12.03%、14.37%、17.18%、9.45%;不同组份蛋白氨基酸种类相同、含量不同;pI 3.5和pI 5.5组份中含量较高的小分子蛋白集中在5000 Da附近,pI6.5和pI7.5组份中含量较高的小分子蛋白主要集中在1000 Da和5000 Da附近。说明不同组份荔枝蛋白抗氧化性不同。荔枝蛋白四个等电点组份的蛋白氨基酸含量、分子量分布及抗氧化性不同。     

Determination of the molecular weight distribution of non‐enzymatic browning products formed by roasting of glucose and glycine and studies on their effects on NADPH‐cytochrome c‐reductase and glutathione‐S‐transferase in Caco‐2 cells

After thermal treatment of a mixture of glucose and glycine for 2 h at 125°C, about 60% of the starting material was converted into non‐soluble, black pigments, whereas 40% of the mixture was still water‐soluble. Dialysis of the latter fraction revealed 30.4% of low molecular weight compounds (LMWs; MW < 10 000 Da) and 10.0% high‐molecular weight products (HMWs; MW ⪈ 10 000 Da). The water‐soluble Maillard reaction products (MRPs) were separated by gel permeation chromatography and ultrafiltration, revealing that 60% of the water‐soluble products of the total carbohydrate/amino acid mixture had MWs < 1 000 Da and consisted mainly of non‐coloured reaction products. MRPs with MWs between 1 000 and 30 000 Da were found in comparatively low yields (about 1.3%). In contrast, about 31.1% of the MRPs exhibited MWs > 30 000 Da, amongst which 14.5% showed MWs > 100 000 Da, thus indicating an oligomerisation of LMWs to melanoidins under roasting conditions. To investigate the physiological effects of these MRPs, xenobiotic enzyme activities were analysed in intestinal Caco‐2 cells. For Phase‐I NADPH‐cytochrome c‐reductase, the activity in the presence of the LMW and HMW fraction was decreased by 13% and 22%, respectively. Phase‐II glutathione‐S‐transferase activity decreased by 15% and 18%, respectively, after incubation with the LMW and the HMW fractions. Considering the different yields, 30% and 10%, respectively, of the LMW and the HMW fractions, the total amount of the LMW fraction present in the glucose‐glycine mixture is more active in modulating these enzyme activities than that of the HMW fraction.     

STUDIES ON THE MECHANISM OF ACTION OF COPPER FINING AGENTS (κ CARRAGEENAN)

Carrageenan mediated clarification of brewers' wort comprises two reactions: interaction between carrageenan and soluble wort polypeptides and flocculation of particulate material. The dose/response characteristics of interaction between carrageenan and soluble polypeptide material suggested that carrageenan exhibits selectivity with respect to specific polypeptide fractions. Size exclusion chromatography of worts demonstrated that carrageenan treatment resulted in reductions in fractions of relative molecular mass Mr 70 000, 40 000 and 12 000. Fining trials demonstrated that the reactivity towards soluble polypeptides is independent of the presence of insoluble particulate material. Furthermore, both interaction with soluble polypeptides and flocculation of particulate material occurred in systems fined under high (80°C) and low (20–25°C) initial temperatures and this suggested that the presence of carrageenan in a helical conformation is essential to fining action rather than conformational transitions in polysaccharide structure. Additionally, carrageenan has no effect on the levels of low molecular mass wort solutes such as nucleic acid derivatives, aromatic and heterocyclic amino acids.     

Antioxidant activity of protein hydrolysates and purified peptides from Zizyphus jujuba fruits

In recent years, there has been a considerable interest in bioactive peptides derived from food proteins which might have beneficial effects on human health. Zizyphus jujuba is a medicinal plant with well-demonstrated biological functions for which various bioactive compounds except antioxidant peptides have been reported. Therefore, the aim of this study was to determine the antioxidant activity of Z. jujuba-derived protein hydrolysates and the purified peptides. Based upon this study, it was revealed that the hydrolysates prepared from Z. jujuba fruit possessed antioxidant effects. Among the prepared hydrolysates, trypsin hydrolysate with the highest antioxidant activity was fractionated using reverse-phase high-performance liquid chromatography (RP-HPLC). The most potent antioxidant peptides, named fractions F3 and F6, identified as VGQHTR (MW: 678.36 ± 0.3 Da) and GWLK (MW: 482.27 ± 0.3 Da), respectively, using tandem mass spectrometry. This study demonstrated that the derived hydrolysates and the purified peptides from Z. jujuba proteins can prevent oxidative reactions and might be underutilised for food preservation and medicinal purposes. However, more detailed studies are required to explore their antioxidant abilities in vivo.     

Improvement of microwave treatment with immersion of fruit in water to control brown rot in stone fruit

Monilinia spp. are the most important cause of brown rot in stone fruit. Currently, no chemical fungicides are allowed in the European Union to be applied in stone fruit after harvest. Microwave (MW) treatments at 20 kW with fruit immersed in water at 40 °C for 50 or 60 s were selected as effective conditions to control brown rot without affecting the appearance of the fruit. The efficacy of the treatments was analyzed on fruit with different weights and at various infection times and inoculum concentrations. When the MW treatment was applied for 50 s, brown rot control was significantly higher for smaller fruit in comparison with larger fruit and MW efficacy decreased with increasing time between inoculation and treatment from 0 or 24 h to 48 h and inoculum concentration from 10³ to 10⁵ conidia mL^− 1. When the treatment time was increased to 60 s, a better control of brown rot was observed and, in general, none of the studied factors had a significant effect on the efficacy of the treatment. MW treatments were also evaluated on naturally infected fruit; brown rot incidence was significantly reduced to less than 43% when MW treatment was applied for 50 s and to less than 7% when applied for 60 s.Industrial relevanceThis study demonstrated the efficacy of MW treatment to control brown rot in postharvest of stone fruit. A relationship between brown rot reduction and the applied MW energy was also provided, which could be useful for designing specific equipment to process large quantities of fruit in less time without affecting the efficacy of the treatment or the quality of the fruit.     

Antioxidative properties of peptides prepared from tuna cooking juice hydrolysates with orientase (Bacillus subtilis)

The antioxidative activity of isolated peptides from of tuna cooking juice hydrolysates by orientase was determined. The results showed that, among the hydrolysates obtained under different hydrolysis time, the highest antioxidative activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity were presented at 60 min. Then, the protein hydrolysate was subjected to a Sephadex G-25 gel filtration chromatography, and five major fractions were obtained. Peptide fractions ranging from 400 to 1500 Da showed the highest antioxidative activity among all fractions. The peptide fractions were further isolated using the two-step high performance liquid chromatography (HPLC-1 and HPLC-2), and six and three fractions were obtained, respectively. The final three antioxidative peptides comprised 4–10 amino acids sequences were observed, and the structures of the peptides were Pro-Val-Ser-His-Asp-His-Ala-Pro-Glu-Tyr (1305 Da), Pro-Ser-Asp-His-Asp-His-Glu (938 Da), and Val-His-Asp-Tyr (584 Da), respectively. We thus conclude that antioxidative hydrolysates from tuna cooking juice may be useful ingredients in food and nutraceutical applications.     

A novel antioxidant and antimicrobial peptide from hen egg white lysozyme hydrolysates

Hen egg white lysozyme (HEWL) was hydrolyzed with papain, trypsin and a combination of the two to isolate antioxidant peptides. The prepared hydrolysates were evaluated for antioxidant activity using DPPH and ABTS radical scavenging, metal ion chelation and lipid peroxidation inhibition. The obtained hydrolysate by a combination of the two enzymes exhibited the highest antioxidant activity compared to other hydrolysates and elected for isolation of antioxidant peptides by reverse-phase high-performance liquid chromatography (RP-HPLC). A most potent fraction namely F2 fraction, identified to be NTDGSTDYGILQINSR (MW: 1753.98 ± 0.5 Da) using tandem mass spectrometry. The antimicrobial activity of the F2 peptide was tested using radial diffusion assay (RDA). Our results showed that this peptide has inhibitory effects on both Gram-negative and Gram-positive bacteria. Minimum inhibition concentration (MIC) values of the F2 peptide against Escherichia coli and Leuconostoc mesenteroides bacteria were 355.64 (±2.2) and 442.25 (±2.8) μg/ml, respectively.     

Profile of non-volatiles in whisky with regard to superoxide dismutase activity

SOD (Superoxide dismutase)-like activities of 23 kinds of single malt whisky (Scotch and Japanese) were evaluated. There was a positive correlation between SOD-like activity and the maturation age of whisky that exceeded the difference resulting from the manufacturing region. The SOD-like activity of Yamazaki 18, a typical single malt whisky in Japan, was approximately 1333 U/ml and that of non-volatile components in the whisky was 388U/mg, indicating that single malt whisky generally has a very strong SOD-like activity. To elucidate their contribution to SOD-like activity, the non-volatile components of whisky (Yamazaki 18) were ultrafiltered and separated with a Diaion HP20/water-EtOH system. Elution of the fraction less than 5000 molecular weight (<5000 MW fraction) with 60% (v/v) EtOH contributed most to SOD-like activity of the whisky. As this elution contained a considerable amount of polyphenolics, the content and SOD-like specific activity of ellagic acid, gallic acid, and lyoniresinol--the main whisky polyphenolics--were evaluated. The contribution of these compounds to the SOD-like activity of whisky was approximately 15%. Polyphenolics in whisky were relatively distributed to a higher MW fraction compared to carbohydrates in whisky, and specific activity (SOD-like activity per weight) of the >10,000 MW fraction was greater than that of the <5000 MW fraction, although the content of this fraction was low. These results indicate that various polyphenolics with higher molecular weights also contribute to the SOD-like activity of whisky together with main whisky polyphenolics.     

Aspergillus ficuum菊粉酶的分离纯化与鉴定

Aspergillus ficuum菊粉酶系经硫酸铵分级沉淀、透析脱盐、DEAE-Cellulose离子交换色谱、Sepharose CL-6B凝胶过滤色谱和制备电泳技术分离纯化,获得五个电泳纯酶:三个外切菊粉酶组分Exo-I、Exo-II、Exo-III和两个内切菊粉酶组分Endo-I、Endo-II。SDS-PAGE分析测得五种酶的分子量分别为:Exo-I:69961Da,Exo-II:39973Da,Exo-III:45561Da,Endo-I:33574Da,Endo-II:30769Da。