香芹酚-酪蛋白纳米颗粒制备及其对枇杷果实炭疽病的抑制作用

通过制备香芹酚(carvacrol,CL)-酪蛋白(casein,CS)的纳米颗粒(nanoparticles,NPs),分析并比较CL-CS纳米颗粒(CL-CS-NPs)与游离CL、酪蛋白+CL混合物在固体培养基上的留存差异性,以及三者对离体培养炭疽菌(Colletotrichum acutatum)菌丝生长的抑制作用和接种在枇杷果实上炭疽菌诱发枇杷病斑的抑制作用,考察CL-CS-NPs对枇杷果实炭疽病的抑制效果。结果表明,12 mg/mL CL和20 mg/mL酪蛋白溶液经超声处理可制备稳定的CL-CS-NPs(152.6 nm),CL-CS-NPs组的缓释时间较游离CL组和酪蛋白+CL混合物组分别延长4 d和2 d,表明纳米化CL缓释效果明显,应用CL-CS-NPs可以延长CL对病菌的作用时间;枇杷炭疽菌离体培养实验结果表明,CL-CS-NPs完全抑菌时间达到5 d,酪蛋白+CL混合物组与游离CL组均为3 d;枇杷果实接种炭疽菌实验结果表明,接种5 d后,喷涂CL-CS-NPs分散液的枇杷果实基本没有出现腐烂,接种7 d后CL-CS-NPs的平均病斑直径仅为1.5 mm、发病率仅为10%;而喷涂酪蛋白+CL混合物的枇杷果实接种5 d后病斑直径虽相对较小,但发病率高达80%,接种7 d后的病斑平均直径达到4.8 mm,腐烂比较严重。综上,将CL-CS-NPs分散液直接喷涂在枇杷果实上,能够取得良好的抑制由炭疽菌引起的枇杷果实腐烂的效果。     

美极梅奇酵母抑制芒果炭疽菌的拮抗机理初探

通过体内体外实验,评价了美极梅奇酵母(Metschnikowia pulcherrima,M. pulcherrima)对芒果炭疽菌(Colletotrichum gloeosporioides,C. gloeosporioides)的抑菌效果。结果表明:在YPD培养基中美极梅奇酵母对胶孢炭疽菌有明显的抑菌效果;在15℃和25℃贮藏条件下,在芒果果实上美极梅奇酵母对病原菌的抑菌率达到了57.81%和40.87%。同时对抑菌机理做了初步探索:扫描电镜显示,酵母菌能够产生物膜,抑制胶孢炭疽菌的入侵;美极梅奇酵母分泌胞外裂解酶-几丁质酶和β-1,3-葡聚糖酶,能有效抑制胶孢炭疽菌繁殖;拮抗酵母微量吸收周围环境中的铁元素,增强了抑菌效果。     

植物精油抑制炭疽菌及对枇杷采后炭疽病与品质的影响

为探讨植物精油对枇杷采后炭疽菌抑制的效果及其机理,分别用丁香酚、柠檬醛和香芹酚对尖孢炭疽菌进行体外处理,筛选出丁香酚为最优抑制剂并研究了其对尖孢炭疽菌外渗率、核酸泄漏及蛋白质的影响。以枇杷为供试材料,接种尖孢炭疽菌后分别用0.5、1.0、2.5、5.0μL/L的丁香酚熏蒸处理,统计病害发生率及病斑直径,并研究了丁香酚对枇杷品质的影响。结果表明:在体外实验中,3种供试精油对尖孢炭疽菌均有明显的抑制作用,48μL/L丁香酚可以完全抑制尖孢炭疽菌的生长,且在一定程度上造成了菌内细胞内容物的渗出。在丁香酚对枇杷果实采后炭疽病抑制效果实验中发现,贮藏6 d时,1μL/L丁香酚处理组病斑直径及病害发生率显著低于对照组,病斑直径仅为6.41 mm,病害发生率为66.67%。丁香酚对枇杷品质影响方面,其能够显著抑制采后枇杷质量损失率的上升及VC含量下降(P0.05),但对枇杷的颜色、硬度、可溶性固形物及可滴定酸等品质指标影响不显著(P0.05)。     

一株桃褐腐病生防酵母菌活性冻干粉的制备及保鲜应用

为研究出一种能有效防治水蜜桃采后褐腐病的生防制剂,以一株间型假丝酵母菌Y-17为研究对象,通过单因素实验和响应面中心组合设计对间型假丝酵母菌Y-17冷冻干燥保护剂的配方进行筛选和优化,考察了所制备的活性冻干粉的生防效力和存放效力,并研究了其对水蜜桃的蜜桃采后贮藏的保鲜效果。结果表明,山梨醇5.43 g/100 mL、海藻糖12.45 g/100 mL、谷氨酸钠13.56 g/100 mL时,组合保护效果最好,酵母菌存活率可达84.21%±0.87%,且冻干后的菌粉仍具有较高的生防效力,-20 ℃贮藏180 d酵母存活率为34.66%。保鲜应用实验表明,酵母菌Y-17活性冻干粉能够有效抑制水蜜桃腐烂,25 ℃贮藏至第9 d时,腐烂指数仅为6.28%。酵母冻干粉还能减少桃果实贮藏期间水分流失,减缓果实软化速度,25 ℃贮藏7 d后,桃果实可溶性固形物含量、维生素C含量、可滴定酸含量分别为10.67%、2.15 mg/100 g、0.17%,均高于对照组,且能有效维持果皮细胞膜完整性,对水蜜桃采后的贮藏保鲜具有积极作用。     

具有拮抗胶孢炭疽菌活性酵母菌的分离和筛选

从芒果果皮、叶片和芒果园土壤中分离筛选得到具有拮抗胶孢炭疽菌(Colletotrichum gloeosporioides)活性的酵母菌,研究其对芒果中胶孢炭疽菌的抑制作用。采用平板对峙法和活体实验进行筛选,采用形态学及r DNA-ITS序列分析等方法进行鉴定。通过平板对峙和活体实验筛选发现,菌株T18对芒果炭疽病病原菌胶孢炭疽菌的拮抗作用明显。抑菌实验表明,当T18菌悬液浓度为1×108cfu/m L时,对胶孢炭疽菌的抑菌半径为14.33mm。活体实验中,经T18处理的芒果果实炭疽病病斑直径仅为1.58mm,具有较强抑菌效果。通过菌落和菌体形态、生理生化、ITS序列分析对菌株T18进行鉴定,最终确定为尼泊尔德巴利酵母(Debaryomyces nepalensis)。     

纳米乳涂膜和1-甲基环丙烯处理对枇杷果实保鲜效果的影响

以‘白砂’枇杷果实为实验材料,以清水处理为对照,研究了纳米涂膜保鲜剂（nanoemulsion coating,NC）-1处理、1-甲基环丙烯（1-methylcyclopropene,1-MCP）处理、NC-1＋1-MCP处理对枇杷在低温（4 ℃）贮藏30 d过程中品质和生理代谢的影响。结果表明：NC-1＋1-MCP处理对枇杷的贮藏品质保持效果最佳,除VC含量外,贮藏结束时,该组果实硬度、腐烂率、质量损失率都显著低于其他处理组,且NC-1＋1-MCP处理更显著抑制了枇杷在贮藏过程中苯丙氨酸解氨酶的活力,从而抑制了木质素的积累;同时抑制了多酚氧化酶和过氧化物酶的活力,从而延缓了果实的褐变衰老。研究结果表明,相比于单一的NC-1或1-MCP处理,NC-1＋1-MCP处理对枇杷保鲜效果更好。     

黄瓜炭疽病病原的分子识别及其采后发病对

目的 为提高黄瓜采后炭疽病病原菌葫芦科刺盘孢Colletotrichum orbiculare的识别效率, 探究该病原菌的侵染对黄瓜采后贮藏品质的影响。方法 本文针对黄瓜炭疽病病原葫芦科刺盘孢Colletotrichum orbiculare的ITS序列设计特异性引物, 以黄瓜自然发病状态下分离的疑似黄瓜炭疽病病原菌DNA为模板, 利用PCR反应进行基因克隆, 并将所得的目的片段进行测序后, 确定为黄瓜炭疽病病原菌葫芦科刺盘孢Colletotrichum orbiculare。将病原菌反接于黄瓜, 取发病腐烂组织, 测定硬度、可滴定酸含量、可溶性固形物含量指标。结果 结果表明, 黄瓜炭疽病病原会造成黄瓜硬度降低, 可滴定酸含量升高, 可溶性固形物含量降低, 严重影响黄瓜的采后贮藏品质。结论 本文为黄瓜采后炭疽病病原菌的分子识别提供参考方法, 并未针对黄瓜采后炭疽病病原菌Colletotrichum orbiculare的控制措施提供研究基础。     

桑椹采后致腐真菌的分离鉴定及其内生酵母保鲜效果

从腐烂桑椹中分离致腐真菌，通过形态学观察及内转录间隔区（internal transcribed spacer，ITS）序列分析进行种属鉴定，初步研究桑椹内生酵母对桑椹致腐真菌的体内外拮抗效果。结果表明，从腐烂桑椹中分离得到3 株真菌，分别鉴定为链格孢菌（Alternaria alternata）、黑曲霉（Aspergillus niger）和富克尔核盘菌（Botryotinia fuckeliana），它们对桑椹均有致腐性。体外拮抗实验显示，拟粉红锁掷孢酵母对链格孢菌（Alternaria alternata） 和富克尔核盘菌（Botryotinia fuckeliana）具有较好的抑制活性；葡萄汁有孢汉逊酵母和异常威克汉姆酵母对3 种致腐真菌具有较好的抑制活性。体内拮抗实验表明，拟粉红锁掷孢酵母和葡萄汁有孢汉逊酵母对桑椹具有较好的保鲜作用。     

采后柑橘与胶孢炭疽菌互作过程中果皮成分的动态变化

目的：探究柑橘胶孢炭疽菌（Colletotrichum gloeosporioides）侵染过程中柑橘果皮细胞壁降解相关酶（cellwall degrading enzymes,CWDEs）、细胞壁成分和防御相关酶活性的动态变化,为进一步研究胶孢炭疽菌致病机理提供理论参考。方法：柑橘果实接种胶孢炭疽菌后,不同培养时间取样测定,并比较分析果皮成分变化。结果：胶孢炭疽菌侵染的柑橘组织中均能产生多聚半乳糖醛酸酶（PG）、果胶甲基半乳糖醛酸酶（PMG）、纤维素酶（Cx）、β-葡萄糖苷酶（β-Glu）、角质酶,且均在侵染前期（1～3 d）达到峰值。纤维素、半纤维素、果胶等细胞壁组分含量随胶孢炭疽菌的侵染而降低,木质素含量随胶孢炭疽菌的侵染而升高。胶孢炭疽菌侵染后,柑橘组织中的过氧化物酶（POD）活性、过氧化氢酶（CAT）活性、丙二醛（MDA）含量总体呈上升趋势。结论：CWDEs和角质酶在炭疽病发病前期起到重要的致病作用,其对果皮细胞壁组分的降解加速了胶孢炭疽菌的侵入;另外胶孢炭疽菌的侵染加速了寄主细胞质膜的过氧化。     

印度梨形孢诱导烟草的抗病性分析

内生真菌印度梨形孢(Piriformospora indica)能够增强植物体抗生物和非生物胁迫能力.为了明确印度梨形孢对诱导烟草抗病性的作用,分别进行了接种病原菌长柄链格孢、胶孢炭疽菌、终极腐霉和茄丝核菌后印度梨形孢定殖的烟草对赤星病、炭疽病、猝倒病和立枯病害的抗性试验,同时分析了接种长柄链格孢后烟叶中丙二醛(MDA)和脯氨酸(Pro)含量、抗氧化酶活性以及病程相关蛋白基因表达水平.结果表明:印度梨形孢定殖的烟草,接种长柄链格孢后,烟叶病斑显著减小,烟叶中MDA含量显著降低,Pro含量显著升高,病程相关蛋白基因PR-1a,PR2,PR3和PR5的表达量明显提高;接种胶孢炭疽菌后,烟叶病斑减小;终极腐霉和茄丝核菌对烟草的危害症状显著减轻.印度梨形孢能诱导烟草产生抗病性,是通过维持生物膜系统的完整性、稳定细胞内渗透压以及膜脂过氧化在较低水平、并调控病程相关蛋白基因的表达来实现的.     

芡实超微粉的体内降血脂功效

采用不同剂量的芡实超微粉对高脂模型小鼠进行灌胃,研究芡实超微粉对高脂模型小鼠血脂四项指标及血清和肝组织中相关酶类的影响。结果发现,与高脂模型组相比,灌胃芡实超微粉组小鼠体重明显降低,肝脏指数和动脉粥样硬化指数也明显降低;小鼠血清总胆固醇(total cholesterol,TC)、甘油三脂(triglyceride,TG)、低密度脂蛋白胆固醇(low density lipoprotein cholesterol,LDL-C)水平均明显降低,高密度脂蛋白胆固醇(high density lipoprotein cholesterol,HDL-C)水平则显著升高;灌胃芡实超微粉低、中、高剂量组小鼠的总超氧化物歧化酶(total superoxide dismutase,T-SOD)和肝酯酶(hepatic lipase,HL)活力均高于高脂模型组,而丙二醛(malondialdehyde,MDA)含量要低于高脂模型组。由此可知,芡实超微粉可降低高血脂症小鼠血脂水平,改善其因摄入过多脂质而导致的肝脏脂肪堆积和动脉粥样硬化,并对高血脂症引起的脂质过氧化损伤具有防护作用。     

Effect of Pomace Drying on Apple Pectin

The effect of temperature used for drying apple pomace on apple pectin characteristics, including chemical composition, color and gelpoint temperature (T_g) was determined. Pomace was obtained from commercial Granny Smith apples and dried in a rotary drier at different air temperatures (T_dr = 60, 70, 80 and 105 °C). Pectin was extracted from dried pomace in nitric acid solution (pH = 2.5) at 80 °C. Major minerals in apple pectin were Ca>Na>Mg. Galacturonic acid content (% AGA=60.6±1.8) was practically unaffected by drying temperature. Conversely, T_dr affected both the degree of methoxylation (DM) and the molecular weight (M_w) of extracted pectin. M_w was estimated by applying the Mark Houwink - Sakurada equation, through determination of intrinsic viscosity of pectin solutions. M_w reduced withT_dr from approximately 122,000 (60°C) to 57,000 (105°C). Pectin color, as Hunter ΔE, was also affected by T_dr. A lighter color was obtained at 80°C. The higher gelpoint value (T_g= 80°C) was obtained with pectin from pomace dried at 80°C. Gelpoint was shown to be more sensitive to T_dr than other quality parameters: while DM had the same value both at 80 and 105°C, minimumT_g occurred at the higher temperature. T_g was also very sensitive to pH.     

Effect of dephosphorylation on bovine casein

Bovine whole casein, α- and β-casein were dephosphorylated by potato acid phosphatase (EC 3.1.3.2); the extents of dephosphorylation were as follows: whole casein 71.6%, α-casein 89.2% and β-casein 73.7%. SDS-PAGE, urea-PAGE, RP-HPLC and ESI-MS demonstrated effects of dephosphorylation on the caseins; α- and β-casein showed both proteolysis and dephosphorylation while whole casein showed only dephosphorylation. Urea-PAGE and ESI-MS confirmed the identities of the individual fractions. ESI-MS established (a) the MW for α- and β-casein as 23 612 and 24 017 kDa, respectively, (b) random removal of 1, 2, 4, 6, 7 and 8 phosphate groups during dephosphorylation of α-casein, (c) random removal of 1, 2, 3, 4 and 5 phosphate groups during dephosphorylation of β-casein and (d) limited dephosphorylation of both α-casein (1 and 2 phosphates) and β-casein (1 phosphate) in the absence of the phosphatase.     

黑菊芋多糖的润肠通便和调节肠道菌群作用

该研究旨在探索黑菊芋多糖对便秘小鼠肠道功能及菌群多样性的影响。将KM小鼠随机分为空白组、模型组和黑菊芋多糖低（2.5 g/kg·bw）、中（5.0 g/kg·bw）、高（10.0 g/kg·bw）剂量组。连续14 d利用复方地芬诺酯诱导便秘小鼠模型,并从第8 d起开始多糖干预。计算小鼠6 h内排便粒数和肠墨汁推进率,采用Illumina MiSeq高通量测序技术对其肠道菌群16S rDNA基因进行分析。结果显示,与模型组相比,低、中、高剂量黑菊芋多糖能够增加小鼠黑便粒数（分别增加48.21%、98.21%和78.57%）和小肠墨汁推进率（分别增加67.34%、107.05%和87.08%）,其中以中剂量效果最佳。中剂量组干预后,微生物多样性、丰富度以及厚壁菌门/拟杆菌比例和变形菌门丰度显著增加（p<0.05）,并促进肠道有益菌乳酸菌属和栖粪杆菌属增殖（p<0.05）。因此,适量食用黑菊芋多糖有助于逆转便秘造成的肠道菌群紊乱,改善便秘症状。     

Effect of acarbose on acute acidosis

A challenge model was used to evaluate a new approach to controlling acute acidosis. Acute acidosis reduces performance in both dairy and beef cattle and most often occurs as a consequence of ingestion of large amounts of readily fermentable starch, resulting in increased production of volatile fatty acids (VFA) and lactic acid and a reduction in ruminal pH. Acarbose is an α-amylase and glucosidase inhibitor that slows the rate of degradation of starch to glucose, thereby reducing the rate of VFA production and maintaining rumen pH at a more stable level. It is commercially available (Glucobay, Bayer, Wuppertal, Germany) and indicated for the control of blood glucose in diabetic patients. The ability of acarbose to reduce the incidence of acidosis and the comparative efficacies of acarbose, sodium bicarbonate, and monensin were tested in 3 acute acidosis challenge experiments in cattle. Rumen-cannulated Holstein steers were challenged with a mixture of 48.4% cornstarch, 48.4% ground corn, 2.1% sodium caseinate, and 1.1% urea with or without test substance. The challenge was administered at a rate of 12.5 g/kg of body weight (BW) as a slurry through the cannula directly into the rumen. Ruminal pH was monitored at 10-min intervals throughout the study. Animals were removed from study and rumen contents replaced if they exhibited acute acidosis as defined as pH <4.5. If acidosis was not observed within 24 h, animals were subjected to a second challenge. Ruminal fluid samples were taken for measurement of VFA and lactate concentrations at various intervals after the challenge. In experiment 1, the carbohydrate challenge induced acidosis in 4 of 4 control animals and 0 of 4 animals treated with 2.14 or 21.4 mg of acarbose/kg of BW in the challenge based on the criterion of pH <4.5. In experiment 2, the carbohydrate challenge induced acidosis in 4 of 7 control animals and 1 of 7 animals when 1.07 mg of acarbose/kg of BW was included in the challenge. In experiment 3, acidosis was induced in 7 of 7 animals in the control, 1% sodium bicarbonate, and 12 mg of monensin/kg of dry matter intake groups and in 3 of 8 steers administered 1.07 mg of acarbose/kg of BW in the challenge. Increases in lactate concentrations and decreases in total VFA associated with acute acidosis were mitigated by acarbose. Thus, acarbose, an amylase and glucosidase inhibitor, prevented or reduced the incidence of acidosis in an acute challenge model in steers and was more effective than monensin or sodium bicarbonate.     

牛乳铁素对几种免疫细胞因子的影响

通过对灌胃牛乳铁素(LfcinB)后小鼠血清中细胞因子IL-2、IL-4、IL-6、IL-10 和TNF-α水平的变化,评价其免疫调节作用。结果表明,灌胃牛乳铁素后3h 采血,分离其血清,用ELISA 试剂盒检测细胞因子,与阴性对照组相比,对细胞因子IL-2 和TNF- α产生极显著促进作用(P ≤ 0.01),对抗炎细胞因子IL-4 有极显著的抑制作用(P ≤ 0.01),对IL-6 有显著的抑制作用(P ≤ 0.05),对抗炎细胞因子IL-10 的分泌影响也极显著(P ≤ 0.01),并且IL-10 随TNF-α的增强而增强,起到平衡作用。因此,口服牛乳铁素对实验小鼠具有免疫增强和调节作用。     

Effect of fat replacers on kefir quality

The purpose of the study was to determine the effects of fat replacers on the quality of non‐fat kefir. Skim milk fortified with Dairy Lo^® (DL) and inulin (INU) was fermented with kefir grains to manufacture kefir. The results of compositional, microbiological, rheological and sensorial analyses were compared with whole kefir (WK) and non‐fat kefir (NFK) controls. Results for dry matter, pH and lactic acid ranged between 82.4 and 109.1 g kg^?1, 4.26 and 4.40, and 7.0 and 9.2 g L^?1, respectively. Acetaldehyde and ethanol contents of samples were between 2.89 and 7.28 mg L^?1, and 151.46 and 323.89 mg L^?1, respectively. In all samples, Lactobacillus spp., Streptococcus spp. and yeast counts were between 9.1 and 9.9, 9.3 and 9.9, and 5.2 and 5.6 log cfu mL^?1, respectively. Kefir samples had non‐Newtonian behaviour and pseudoplastic fluid with thixotropy. At the first day, DL had the highest apparent viscosity (3.119 Pa s) while NFK had the lowest value (1.830 Pa s). In the sensory evaluation, odour and taste scores of samples were not different. Dairy Lo^® and inulin could be used without any adverse effect for the production of non‐fat kefir. Copyright © 2009 Society of Chemical Industry     

Effect of supercritical Carbon Dioxide on proteins

Summary Commercial ribonuclease was treated with wet supercritical carbon dioxide at 300 bars at room temperature and at 80°C. Amino acid composition and trinitrobenzene sulfonic acid-reactive lysine content were unaltered by this treatment. Disc electrophoresis with sodium dodecyl sulfate demonstrates a slight oligomerisation. This is mainly due to intermolecular linkages by disulfide bridges as indicated by disc electrophoresis after reduction with 2-mercaptoethanol. At the same time this technique indicates the cleavage of some peptide bonds within the disulfide loops of the ribonuclease molecule. Ribonuclease exposed to wet nitrogen under the same conditions shows the same alterations. They are obviously unrelated to the kind of gas used. The observed fragmentation is related to the presence of water. As indicated by tryptic digest these alterations do not decrease the digestibility by proteolytic enzymes. On the contrary the treated samples are split better than untreated ribonuclease. This is undoubtedly due to an unfolding of the protein molecule. The extent of this unfolding is definitely influenced by the presence of water. Ribonuclease samples treated with wet supercritical carbon dioxide only exhibit alterations that can be observed after heating at 80°C with water at normal pressure. In particular no chemical reactions with carbon dioxide can be demonstrated. Pressure in the range used here at best influences the alterations observed to a minor degree.

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Einfluß überkritischen Kohlendioxids auf Proteine

Zusammenfassung Käufliche Ribonuclease wurde feuchtem Kohlendioxid von 300 bar bei Raumtemperatur und bei 80°C ausgesetzt. Die Bestimmung der Aminosäurezusammensetzung und des Gehaltes an Trinitrobenzolsulfonsäure-reaktiven Lysin zeigt keinen Unterschied zu unbehandelter Ribonuclease. Durch Discelektrophorese in einem Natriumdodecylsulfat-haltigen System kann eine leichte Oligomerisierung nachgewiesen werden. Diese beruht zum größten Teil auf interchenaren Verknüpfungen über Disulfibrücken, wie aus der Discelektrophorese nach der Reduktion mit -Mercaptoäthanol hervorgeht. Gleichzeitig wird dabei die Spaltung einiger Peptidbindungen erkennbar, die innerhalb der Disulfidschleifen des Ribonucleasemoleküls liegen. Ribonuclease, die feuchtem Stickstoff unter den gleichen Bedingungen ausgesetzt wurde, zeigt die gleichen Veränderungen. Diese sind somit unabhängig von der Art des verwendeten Gases. Die beobachtete Fragmentierung ist auf die Anwesenheit des Wassers zurückzuführen. Wie die Abbauversuche mit Trypsin zeigen, schädigen these Veränderungen nicht die Spaltbarkeit durch proteolytische Enzyme. Die so behandelten Proben sind vielmehr besser spaltbar als unbehandelte Ribonuclease. Dies ist sicher auf eine Auffaltung des Proteinmoleküls zurückzuführen, deren Umfang entscheidend durch den Wassergehalt beeinflußt wird. Insgesamt zeigen die mit feuchtem überkritischen Kohlendioxid behandelten Ribonucleaseproben keine Veränderungen, die nicht auch nach der Erhitzung auf 80°C mit Wasser unter Normaldruck beobachtet werden konnen. Insbesondere können keine Einwirkungen des Kohlendioxids nachgewiesen werden. Der Druck in dem hier verwendeten Bereich trägt höchstens unwesentlich zu den beobachteten Veranderungen bei.

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I thank the Fonds der Chemischen Industrie for supporting this work, Miss Marie-Luise Kern for skilful technical assistence, and Mrs. Anneliese Mödl and Mrs. Angelika Langwieser for performing the amino acid analyses     

Effect of high pressure treatment on ovotransferrin

High pressure processing of ovotransferrin was carried out to study the structural and physiochemical changes of ovotransferrin under various pressure levels. At pH 8 and pressures higher than 200 MPa, a decrease in total sulfhydryl groups and an increase in surface hydrophobicity were observed along with a partial aggregation. A gradual shift of denaturation peak towards higher temperature was noticed up to 500 MPa, leading to a total loss of the enthalpy of denaturation at pressures of 600 and 700 MPa, where a significant decrease in intrinsic fluorescence was also observed. At pH 3, the ovotransferrin adopted a molten globule state, associated with a significant increase in surface hydrophobicity and reactive sulfhydryl content; structurally, no clear denaturation peaks in differential scanning calorimetry (DSC) were detected at any level of pressure treatment whereas a noticeable decrease in intrinsic fluorescence was evidenced up to 600 MPa and then increased at 700 MPa pressure treatment. Fourier transform infrared spectroscopy (FT-IR) revealed that the conformational structure were changed from helices, sheets, turns, and aggregated strand to mostly intermolecular β-sheets or aggregated strands at pH 8 at 200 MPa but switched back to original structure at higher pressures.     

Effect of flour heating on dough rheology

Heating soft wheat flour at 80°C for 15 min has already been shown to improve its bread-making potential. In this study, flour was fractionated to determine the specific effect of heating on its constituents (gluten, starch, lipid, water-soluble). While gluten was easier to extract and its texture was slacker after heating, it significantly increased dough-mixing stability and development time (P<0.01). Heated water-soluble fraction containing pentosans partly decreased stability (P=0.06).