充CO_2气调储藏对青稞品质的影响

为了研究储藏过程中CO_2气调条件对青稞品质劣化进程的影响,研究在0、25、37℃条件下,分别充CO_2气调和常规储藏青稞300 d,比较不同储藏条件下青稞品质变化差异。结果表明在相同温度条件下,充CO_2气调组与常规组相比,其品质变化幅度小,气调储藏一定程度起到了延缓青稞品质下降的作用。青稞在储藏过程中,其含水量、游离巯基含量、可溶性蛋白含量、α-淀粉酶含量和过氧化氢酶含量均随着储藏时间延长呈下降趋势,温度上升促进这些指标下降。与其他储藏温度相比,青稞在37℃储藏条件下的含水量、色泽和过氧化氢酶活性的变化更大。青稞随储藏时间的延长,其值呈上升趋势,储藏温度越高,变化趋势越大。综合看来,低温条件下能更好保持青稞的品质,而高温下充CO_2气调储藏能起到了延缓青稞品质降低的作用。研究结果为青稞的合理、安全储藏提供参考。     

不同储藏方式对粳糙米储藏品质的影响

研究了不同储藏方式对粳糙米储藏品质的影响。结果表明:随着储藏时间的延长和储藏温度的升高,充氮气调和常规储藏粳糙米的发芽率、生活力均呈下降趋势,且温度越高,下降得越明显;常规储藏较气调下降较慢,气调储藏在保持糙米种用品质上并不占优势。气调组和常规组粳糙米的脂肪酸值和丙二醛含量随着储藏时间和温度的增加呈上升趋势,且温度越高,增加越明显;在低温区(20、25和30℃)这些指标随时间的增加幅度较之35℃要小一些,气调储藏能够缓解高温对粳糙米品质的不利影响。常规储藏和气调储藏的过氧化氢酶活动度均随储藏时间的延长而降低;低温区变化相对缓慢,35℃条件下变化幅度较大;但常规储藏降低得更明显,气调储藏的值要好于常规储藏。因此,低温储藏是保鲜粳糙米的最佳手段,在低温条件受限的地区,可考虑使用充氮气调储粮技术,既节约成本,又绿色环保。     

充氮气调对花生制油品质的影响研究

对不同温度、不同储藏方式下储藏花生仁提取油的品质进行对比。试验表明:随着温度升高和储藏时间延长,油的色泽变化不明显,酸值、过氧化值和羰基值上升趋势明显;与常规对照组比较,充氮98%气调组制油品质变化相对缓慢,充氮90%气调组效果不明显。在25℃以下储藏,各组试样的品质变化缓慢;在高温下储藏,充氮98%气调组在30℃下能延缓花生的酸败速度,但在35℃即使充氮效果亦不明显。因此,建议花生仁储藏温度不宜超过30℃,配以低温或气调效果更好。     

氮气气调储藏下不同温度对晚籼稻品质的影响

目的 探究氮气气调结合控温储藏对晚籼稻品质的影响。方法 本研究以广西桂林新收获的晚籼稻为对象,采用99%浓度的氮气包装,在高温(35℃)、常温(25℃)、低温(15℃)3个条件下的恒温培养箱中进行180 d的储藏。同时设立常规储藏条件作为对照,每30 d取一次样,进行加工、储藏品质及米饭蒸煮品质指标的测定。结果 在3个温度条件下,相比于常规储藏,氮气气调稻谷能够有效延缓出糙率和水分的下降。在35℃条件下,氮气气调稻谷的整精米率、品尝评分值下降幅度及黄粒米率、脂肪酸值、直链淀粉含量、米饭吸水率的上升幅度均较大。在15℃和25℃条件下,氮气气调稻谷则能够有效延缓整精米率和品尝评分值的下降,并抑制黄粒米率、脂肪酸值、直链淀粉含量和吸水率的上升。在25℃和35℃条件下,氮气气调能够抑制蒸煮后体积膨胀率的上升,但在15℃条件下的效果不明显。相关性分析显示,在种子储藏时应避免使用氮气气调。主成分分析结果表明,在25℃条件下,氮气气调比低温常规储藏效果更好,能够延缓稻谷品质劣变。而品质特征指标与储藏条件的相关性分析结果表明,储藏温度对稻谷品质的影响较小。结论 将温度控制在25℃的氮气气调储藏方式在经...     

糯性糙米气调储藏脂质变化的研究

实验研究三种储藏温度（15 ℃、25 ℃,35 ℃）和不同气调储藏（CO2、N2、真空）以及常规储藏方式条件下糯性糙米在不同储藏时间脂类物质的变化,发现储藏温度对糯性糙米脂肪酶活性、过氧化氢酶活性、脂肪含量、脂肪酸值、丙二醛和羰基值变化影响显著,同温度下气调组较常规组储藏对糯性糙米的储藏品质有较好的保护作用。研究表明,低温（15 ℃）条件下真空储藏可以减缓糯性糙米品质劣变。     

环境温度对油菜籽储藏品质的影响

采用不同温度(15、25、35℃)对不同水分含量(6.2％、7.9％、10.6％、12.3％)的国内普通双低油菜籽进行模拟储藏,系统研究了不同温度和水分含量对油菜籽储藏期间色泽及主要品质指标的影响.结果表明:油菜籽红度值a*和游离脂肪酸(FFA)含量均随着储藏时间延长而增加,储藏温度和水分含量愈高,增加速率越大;油菜籽过氧化氢酶活动度、氮可溶性指数均随着储藏时间延长而下降,其中在35℃条件下,高水分含量的油菜籽过氧化氢酶活动度、氮可溶性指数下降迅速.油菜籽红度值a*与FFA含量、过氧化氢酶活动度、氮可溶性指数等品质指标具有显著相关性,测定其色泽可有效表征油菜籽储藏过程中的品质变化.     

米发糕的储藏品质研究

以大米为原料,采用专用发酵剂制作米发糕,研究包装方式和温度对米发糕储藏品质的影响,为方便型米发糕的工业化生产提供技术参数。结果表明,储藏温度、包装方式对米发糕储藏品质有显著影响。储藏过程中米发糕菌落总数上升,结晶度、硬度、咀嚼度增加,弹性、黏聚性和水分含量降低,导致感官品质下降。CO2气调包装后低温度储藏有利于抑制水分损失和细菌繁殖,米发糕于-18℃储藏,菌落总数、水分变化缓慢。-18℃储藏米发糕的结晶度小于4℃储藏时的结晶度。气调包装有利于保持米发糕的质构特征。米发糕采用CO2气调包装后于-18℃储藏,使米发糕的保质期可达10天以上。     

糯米粉储藏特性的研究

研究了糯米粉在20℃、25℃、30℃及35℃温度下,以真空、CO2气体封入、N2气体封入、自然空气封入4种包装(气体)条件下,储藏6个月,分析糯米粉储藏品质的变化情况。结果表明,储藏温度越高,糯米粉品质劣变越严重,60d为最佳储藏期限。在高温35℃条件下气调储藏组(真空、CO2气体封入、N2气体封入)较常规储藏(自然空气封入)对糯米粉储藏品质的劣变起到抑制作用,但不同气调储藏方式对糯米粉储藏品质影响的差异不明显。     

青稞储藏过程中与脂质氧化相关的陈化分子机制研究

为探寻青稞储藏过程中脂质的变化,以西藏青稞为材料,研究在0、25、37℃时常规储藏和CO_2气调储藏对青稞脂肪酸值、过氧化值、脂肪酶活力的影响。结果表明:在青稞储藏过程中这3种指标的变化均呈先升高后降低的趋势。方差分析显示,储藏温度对青稞脂肪酸值、过氧化值有极显著影响(P0.01),0℃是储藏的最佳条件。相关性分析表明,脂肪酶活力对脂肪酸值影响极显著(P0.01)。     

高筋小麦粉储藏技术的研究

以高筋小麦粉为研究对象,通过模拟在不同温度(15、25、35℃)、不同储藏方式(充N2、脱氧剂脱氧、真空、对照)下储藏高筋小麦粉,研究了储藏期间高筋小麦粉脂肪酸值、降落数值、湿面筋、面筋指数的变化规律。结果表明:高筋小麦粉的脂肪酸值、降落数值、湿面筋以及面筋指数都能较好地反映出高筋小麦粉储藏品质的变化。总体变化趋势表现为:随着储藏时间的延长,脂肪酸值和降落数值升高,湿面筋含量和面筋指数下降。在储藏期间温度的变化是最主要的影响因素,低温有延缓品质劣变的优点;其次为储藏方式,但相互之间差别不明显;同时发现气调储藏在高温环境中效果较好,所以高筋小麦粉应尽量保存在低温气调储藏条件下。     

化学和物理精炼工艺对葡萄籽油氧化劣变品质的影响

为了研究化学和物理精炼工艺对葡萄籽油氧化裂变品质的影响,分别采用化学和物理工艺精炼葡萄籽原油,探讨反式脂肪酸的变化规律,以及不同精炼阶段油脂的酸价、过氧化值、p-茴香胺值和VE含量变化。结果表明:葡萄籽油经化学精炼酸价降至(0.20±0.016)mg KOH/g,葡萄籽油的过氧化值和p-茴香胺值降低,反式脂肪酸质量分数增加至(0.36±0.001 4)%,VE损失了37%~43%。对葡萄籽原油进行物理精炼,240℃条件下真空脱酸6 h,酸价降至(0.19±0.029)mg KOH/g,过氧化值降低、p-茴香胺值升高,反式脂肪酸质量分数增至(0.91±0.001 3)%,VE损失了50.69%。比较得知,物理精炼过程相对于化学精炼对葡萄籽油品质的影响较大。     

Thermoactivity and effects of organic solvents on digestive lipase from hepatopancreas of the green crab

Unlike classical digestive lipases, the crab digestive lipase (CDL) displayed its maximal activity at a high temperature. The CDL activity’s optimal temperature, when using emulsified or monomolecular film as substrate, was 60 °C. To our knowledge, this is the first report of an animal digestive lipase having such an optimal temperature. The maximum activity of CDL appeared at pH 8. Lipase activity was compatible with the presence of organic solvents, except for butanol. Furthermore, the hydrolysis was found to be specifically dependent on the presence of Ca²⁺ ions, since no significant CDL activity was detected in the presence of ion chelators such as EDTA. Nevertheless, the CDL does not require Ca²⁺ to trigger the hydrolysis of tributyrin emulsion. Interestingly, Zn²⁺ and Cu²⁺ ions acted as strong inhibitors of CDL activity when using tributyrin as substrate. Lipase stability in the presence of organic solvents, as well as at high temperatures, makes it a good candidate for application in non-aqueous catalysis.     

己烷体系中磷脂酶A1催化卵磷脂乙醇解制备溶血卵磷脂的研究

在己烷体系中,采用磷脂酶A1催化卵磷脂乙醇解制备溶血卵磷脂。首先通过单因素试验分别考察了加酶量、加水量、底物比、温度和溶剂比对卵磷脂乙醇解制备溶血卵磷脂的影响,并在此基础上利用响应面法对反应工艺进行了优化。最终确定最佳工艺条件为:卵磷脂1.5 g,加酶量40μL/g(磷脂酶A1/卵磷脂),加水量25μL/g(水/卵磷脂(PC)),底物比:1∶3(PC/无水乙醇,mol/mol),温度30℃,溶剂比:1∶2(PC/正己烷,W/V),反应时间3.55 h,溶血磷脂转化率达98.3%。结果表明,磷脂酶A1可以催化磷脂酰胆碱乙醇解反应制备溶血磷脂酰胆碱。     

Matrix effects on the bioavailability of resveratrol in humans

The pharmacokinetics of resveratrol in 11 healthy male volunteers has been assessed in a randomized, crossover, controlled clinical trial after the administration of three grape products: red wine (250 mL), grape juice (1/L), or tablets (red wine extracts enriched with trans-resveratrol). Doses of trans-resveratrol independently of the product administered, were about 14 μg/kg. Biological samples were collected and analysed by capillary gas chromatography–mass spectrometry. cis-Resveratrol, trans-resveratrol and dihydroresveratrol were determined in plasma and urine. Plasma concentration of trans-resveratrol after hydrolysis increased as a response to all grape products and that of cis-resveratrol after wine and grape juice. Free forms of these phenolic compounds were deemed undetectable in plasma. Despite similar trans-resveratrol doses being administered, its bioavailability from wine and grape juice was 6-fold higher, than that from tablets. Resveratrol was better absorbed from natural grape products than from tablets, pointing out the importance of the matrix in its bioavailability.     

新型W/O盐卤凝固剂对大豆蛋白凝胶中水分变化的影响

探讨新型油包水(W/O)盐卤凝固剂对大豆蛋白凝胶中水分变化的影响。利用差示量热扫描仪(DSC)和低场核磁共振(LF-NMR)来研究豆腐凝胶过程中水分的变化。结果表明,在豆腐凝固的过程中,总水分含量下降,自由水下降,结合水含量总体呈现上升趋势,豆腐凝胶结构中的水分自由度在不断减少。与传统盐卤凝固豆腐相比,新型W/O盐卤豆腐凝胶在同一阶段的自由水含量较高,弛豫时间较长,W/O凝固剂的缓释可以改善豆腐的质量。此外,WPI含量不仅对乳液稳定性起作用,而且会改善豆腐品质。在0.5%WPI W/O乳液作为凝固剂得到的豆腐样品核磁共振成像中氢质子的密度最大,说明WPI可以提高豆腐的持水性和品质,因此可将0.5%WPI制备的W/O乳液凝固剂作为豆腐生产用凝固剂。     

纳米Ag@TiO2、Fe@TiO2和Zn@TiO2的抑菌活性比较研究

探索常见金属离子掺杂对抑菌片的抑菌性能的影响,为新型纳米TiO₂抑菌片的制备与改善提供技术基础。选择固定质量分数的Ag⁺、Zn²⁺和Fe³⁺掺杂TiO₂,通过抑菌圈、MIC与MBC方法综合评价其抑菌性能,对微观结构进行表征分析,探讨抑菌性能差异的原因。结果表明:抑菌性能大小顺序为Ag@TiO₂> Zn@TiO₂> Fe@TiO₂,Zn@TiO2 的抑菌活性较好但抑菌稳定性差Ag@TiO2对大肠杆菌和金黄色葡萄球菌的MIC、MBC均是10、20 mg/L,Zn@TiO₂对大肠杆菌和金黄色葡萄球菌的MIC、MBC均是30、50 mg/L。表征发现抑菌活性强弱主要归因于纳米TiO₂表面与金属离子共同产生的活性位点数量及稳定性,与孔结构或表面宫能团的关联不大。     

Effect of acetylation,oxidation and annealing on physicochemical properties of bean starch

Black and Pinto bean starches were physically and chemically modified to investigate the effect of modification on digestibility and physicochemical properties of bean starch. The impact of acetylation, oxidation (ozonation) and annealing on the chemical composition, syneresis, swelling volume, pasting, thermal properties and digestibility of starches was evaluated. The physicochemical and estimated glycemic index (eGI) of the Black and Pinto bean starches treated with ozone were not significantly (P > 0.05) different than that of their respective control starches. Annealed starches had improved thermal and pasting properties compared to native starches. Acetylated starches presented reduced syneresis, good pasting properties and lower eGI. Also, all modified starches had increased levels of resistant starch (RS). Therefore, the digestibility and physicochemical properties of bean starch were affected by the type of modification but there were no significant (P > 0.05) differences between the Black and Pinto bean starches.     

Inhibitory effects of salicylic acid family compounds on the diphenolase activity of mushroom tyrosinase

Mushroom tyrosinase (EC 1.14.18.1) catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones that form brown or black pigments. In the present paper, inhibitory effects on the diphenolase activity of 10 compounds of the salicylic acid-family on the diphenolase activity of mushroom tyrosinase have been studied. The results show that some of these compounds behave as reversible inhibitors. Salicylic acid is a competitive inhibitor while 4-methoxysalicylic acid is non-competitive, 5-methoxysalicylic acid is mixed-I type and 4-methylsalicylic acid and 5-methylsalicylic acid are mixed-II type. The inhibition constants of these five compounds were evaluated. The inhibition strength follows the order: 4-methylsalicylic acid > 5-methylsalicylic acid > 4-methoxysalicylic acid > salicylic acid > 5-methoxysalicylic acid. Models of the interaction between the enzyme and the inhibitors are further discussed and compared.     

The effect of phytic acid on oxidative stability of raw and cooked meat

The effects of phytic acid addition (0.1, 1 and 5 mM) to pork and beef homogenates on TBARS and metmyoglobin levels in raw meat, and TBARS and heme iron contents in cooked meat during 3 days of storage at 4 °C were investigated. Also, the role of inositol as a potential synergist of IP₆ (phytic acid) was examined. IP₆ effectively decreased the TBARS accumulation in raw and cooked meat homogenates. The metmyoglobin formation was inhibited in raw beef by phytic acid in a dose-dependent manner. The effect of IP₆ was more pronounced in cooked meat than in raw and in cooked beef homogenates more than pork. Inositol did not enhance antioxidant action of phytic acid in minced meat.     

用于亚硒酸钠检测的近红外荧光探针的设计合成及其应用研究

目的 建立一种基于荧光探针的亚硒酸钠检测方法。方法 基于荧光探针的构建方法, 在近红外荧光团中引入乙酰丙氨酸基对荧光团结构中羟基进行保护并淬灭荧光, 设计并合成荧光增强型近红外探针SeP1, 通过核磁氢谱(1Hydrogen-nuclear magnetic resonance, 1H NMR)、碳谱(13Carbon-nuclear magnetic resonance, 13C NMR)和高分辨质谱(High resolution mass spectrum, HRMS)的确证其化学结构, 通过荧光光谱法研究探针SeP1对亚硒酸钠的识别效果。结果 在多种分析物种,探针SeP1对亚硒酸钠具有高效专一的荧光选择性, 其最大荧光发射在近红外区(657 nm), 能够克服基质中常见背景荧光干扰, 在其他常见阴离子存在的情况下,具有较强的抗干扰能力并能够对亚硒酸钠实现裸眼识别。该探针对亚硒酸钠的最低检测限为0.068 μmol?L-1。进一步研究了探针对亚硒酸根的识别机理：当亚硒酸根离子与探针结构中乙酰丙基基团发生特异性反应后,使得探针结构中羟基脱保护重新生成带有羟基的化合物1,释放出强烈的荧光,通过高分辨质谱进一步确证了上述识别机理。结论 该探针对亚硒酸钠具有高效专一的识别能力, 并成功的应用于饮用水中亚硒酸钠加标回收检测, 具备较强的实用价值。