微波加热与常规加热对植物油温度和氧化稳定性影响的对比

鉴于微波加热和常规外加热方式作用的内要机理完全不同,研究了两种加热方式对植物油温度和氧化稳定性影响的情况,发现植物油的温升速率受加热方式的影响较大,而其品质方面却没有太显著的关别。     

微波辐射与常规加热方式作用下植物油品质变化的对比试验

系统地研究了一定输出功率下 ,微波辐射法和常规外加热法对植物油品质影响的差异。发现在微波辐射下 ,植物油的PV值及TBA值随处理时间而增大的幅度均略高于常规外加热方法 ,但对植物油中α—VE 含量的减少幅度则略低于常规外加热方法。     

淀粉溶液的通电加热研究

本文研究了食盐浓度、淀粉浓度和电压对淀粉溶液的电导率和通电加热速率的影响;研究了通电加热对淀粉糊化特性的影响。结果表明:淀粉溶液在通电加热过程中,加热速率和电导率随食盐浓度的增大而增大;随电压的升高而增大;随淀粉浓度的增大而减小。而电导率在达到糊化温度之前随温度的升高而增大,在糊化温度之后随温度的升高而降低。淀粉溶液在通电加热时其糊化特性无明显变化。     

微波处理淀粉自由基的生长和衰减

研究在微波加热方式下大米淀粉自由基的生长以及储存过程中的衰减。运用电子顺磁共振的检测手段和图谱拟合软件,对微波处理淀粉的自由基相对数量和结构进行分析。结果表明：微波处理淀粉产生在室温下能够较长时间存在的自由基;淀粉在微波处理后会产生以碳为中心的自由基;在1 600 W（160 W/g）功率下自由基数量的增长速率大于800 W（80 W/g）功率下的增长;在停止微波处理后,自由基信号在衰减之前有一段短时间的增长期;实验从微波处理淀粉中分离出3 种自由基成分,主要成分为以葡萄糖环C1为中心的自由基。     

EPR Studies of Thermally Treated Oxidized Corn Starch

The formation of radicals in oxidized corn starch at 20–250°C in air was investigated by quantitative EPR spectroscopy. It was found that the presence of carboxyl groups in the oxidized starch increases the starch's ability to generate radical species. Introducing Cu²⁺ ions into the starch, as a catalyst or as an EPR probe, leads to the formation of copper‐carboxyl complexes containing two carboxyl ligands. Drastic increase in the number of radical species at about 250°C is accompanied by a decrease in the intensity of EPR signal of Cu²⁺‐carboxyl complexes, indicating that the thermal degradation of oxidized corn starch occurs with the formation of radicals, probably via breaking the chemical bonds in the carboxyl groups.     

微波及超声-微波协同加热对大米淀粉回生特性的影响

研究了传统加热、微波加热和超声-微波协同加热对粳米淀粉和糯米淀粉回生特性的影响。结果表明:粳米淀粉对热作用的敏感性更高,在相同的贮存时间下,微波加热和超声-微波协同加热的粳米淀粉凝胶较传统加热的样品回生速率慢,凝胶强度增加和酶解力下降较小,并且微观结构上更致密平整。原因在于微波加热和超声-微波协同加热方式下淀粉颗粒膨胀破裂不充分,直链淀粉浸出的量相对较少,导致淀粉凝胶重结晶有序化程度较低,从而抑制淀粉回生过程。     

Development of Linear Heating Rates Using Conventional Baths and Computer Simulation

ABSTRACT: A conventional cooking method to obtain linear heating was developed by heating sequentially in multiple baths set at different temperatures. The time and temperature in each rate were determined using computer simulation. Two heating media (water and ethylene glycol) were employed. Gelation properties of whey protein concentrate (WPC) slurry (15% protein and 2% salt) were evaluated at 3 different heating rates (1, 8, and 15°C/min). Failure shear stress and strain values were significantly affected by heating rates. Failure shear stress and strain at 1°C/min were significantly higher compared to higher heating rates (8 and 15°C/min).     

微波加热法测定调味料中的水分

采用微波加热法测定调味料中的水分，通过正交设计实验确定了测定条件，微波加热时间4-5min，样品质量3－4g，微波输出功率720W。对同一样品平行测定7次，S＝0。37，CV＝0．036，与蒸馏法比较，无明显差异。     

脂肪氧合酶催化亚油酸氧化与大豆蛋白相互作用过程中自由基迁移的电子顺磁共振研究（Ⅱ）自由基类型的确定

模拟大豆蛋白制取过程,建立由亚油酸(LA)、脂肪氧合酶(LOX)和低脂质含量的大豆蛋白(LRSP,lipid reduced soybean protein)所组成的模拟体系并制各大豆蛋白,应用电子顺磁共振(EPR)比较研究了不同微波功率下的大豆蛋白EPR波谱,探讨了制各方法对自由基浓度和种类的影响,确定了四种类型的自由基.g值范围在2.0041～2.0054之间的碳自由基源于蛋白质肽链骨架α-碳原子或其侧链其他碳原子,其中场信号或称自由基浓度随微波功率的增加而降低.g值范围在2.019～2.028之间的硫自由基源于蛋白质中甲硫氨酸、半胱氨酸等含硫氨基酸残基侧链,它在室温下稳定,在不同微波功率下检测,在两个样品中均可观察到.羟基自由基·OH在两个样品中均可观察到,它源于自由基链反应和水分子,与前述大豆蛋白氧化性修饰的二酪氨酸形成有关.醛自由基一定源于大豆蛋白与LOX催化LA氧化产生的降解产物的酶促反应.它包含在中场碳自由基信号中,但稍稍偏向高场区.     

脂肪氧合酶催化亚油酸氧化与大豆蛋白相互作用过程中自由基迁移的电子顺磁共振研究(I)自由基的检测

应用电子顺磁共振(EPR)波谱研究了模拟体系中导致大豆蛋白聚集体形成的自由基由氧化亚油酸到大豆蛋白的迁移.经脂肪氧合酶催化亚油酸的诱导,在大豆蛋白EPR波谱中检测到一个很强的源于肽链骨架α-碳原子或其侧链其它碳原子的自由基信号,其g值范围在2.0041～2.0054之间.此外,在碳自由基中场信号的低场区尚有一个额外的肩峰,它是硫自由基信号,其g值范围在2.019～2.028之间.在大豆蛋白与脂肪氧合酶和亚油酸混合反应前,添加天然抗氧化剂如VC和α-生育酚或人工合成的抗氧化剂2,6-二叔丁基对甲酚(BHT)均能抑制自由基信号和荧光的发展,可使中场碳自由基信号降低35%～65%.     

An EPR study of free radical generation during maceration of uncooked vegetables

Electron paramagnetic resonance (EPR) spectroscopy has been used to study free radicals formed in a range of plant tissues as a result of physical damage, with the objective of gaining some insight into the free radical chemistry that is initiated when uncooked vegetable products (eg salads) are eaten. Chemical spin traps were used to aid the detection of unstable free radicals; more stable radicals were detected directly. Commonly observed ‘stable’ species were the monodehydroascorbate radical, which has a characteristic doublet spectrum, and a single‐peak resonance, which is presumed to come from free radical centres stabilised in macromolecules. In mushrooms (Agaricus spp), spin‐trapping experiments using either α‐(4‐pyridyl‐1‐oxide)‐N‐t‐butyl‐nitrone (4‐POBN) or phenyl‐t‐butyl‐nitrone (PBN) showed the formation of large quantities of adducts of the radical from 4‐hydroxymethylbenzene diazonium salts. Pleurotus species, in contrast, gave signals consistent with the formation of unidentified C‐centred radicals. With other foodstuffs, reaction with 4‐POBN was complex and signals from 4 ? POBN· and adducts were observed along with the t‐butylhydronitroxide radical (an adduct breakdown product). Investigation of carrot hypocotyl rootstock in the presence of 5‐(diethoxyphosphoryl),5‐methyl‐1‐pyrroline‐N‐oxide (DEPMPO) revealed adducts of ·OH and unidentified C‐centred radicals. Free radical interactions between food components were demonstrated by the suppression of the signal from the 4‐POBN adducts of lettuce by onion, garlic, satsuma or vinaigrette, but not by olive oil. In addition, an appreciable decrease in spectral intensity of the 4‐POBN adduct from lettuce was observed in the presence of saliva, which suggests that saliva contains free radical scavengers which are able to compete successfully with the spin trap. © 2002 Society of Chemical Industry     

微波加热稳定米糠研究

本文探讨影响微波加热稳定米糠的有关因素，对微波加热后米糠温度，水分蒸发和过氧化物酶残余活力进行测定，结果表明，米糠水分含量在微波加热稳定过程中起着重要作用，适当提高米糠含水率和微波功率有利于米糠稳定处理，经微波稳定处理的米糠于25℃储藏8周，酸值上升幅度远低于未处理米糠。     

Accelerated texture softening of some root vegetables by Ohmic heating

Effects of different thermal processing methods (Ohmic heating, high and low power, microwave and conventional heating) on textural properties of cylindrical pieces of root vegetables of carrot, red beet and golden carrot were investigated and compared with conventional and microwave processes. The samples were subjected to different processing methods and textural parameters of the processed samples were analyzed using texture profile analysis (TPA) at different processing times. Texture parameters-processing time data were fitted into a previously suggested equation and texture softening rate (K) and residual constant (A) values were calculated. From the K and A values it can be concluded that not only Ohmic heating resulted in greater softening rates but also the final hardness of the samples treated by Ohmic heating was significantly lower than those of other samples treated by either conventional or microwave methods. Negative correlations were found between texture hardness and weight loss of all samples undergone different processing methods.     

Detection of irradiated frog (Limnonectes macrodon) leg bones by multifrequency EPR spectroscopy

The free radicals of irradiated frog Limnonectes macrodon leg bones tissue were studied by electron paramagnetic resonance in both X and Q bands. The kinetic behaviour, the activation energy as well as the thermal stability of the radiation-induced radicals in bone tissue were investigated by means of both isothermal and isochronal annealing. Unirradiated bone tissue displayed the presence of Mn²⁺ ions at both frequencies, while a week EPR singlet was evidenced only at 34 GHz. When irradiated with ⁶⁰Co gamma ray, the EPR spectra completely changed their patterns and intensity, the overall spectra provin, at both frequencies, to be typical axial ones. The 100 °C isothermal annealing studies attested the existence of two different free radical species, significantly more labile than in the case of mammal bone tissues. At the same time, the Arrhenius plot of 15 kGy irradiated bones evidenced two different kinetic regimes with two different activation energies.     

An Electron Spin Resonance Study of Evolution of Organic Free Radicals in Irradiated Pepper During Heat Treatment

ABSTRACT: The thermal evolution behavior of the organic free radicals induced in irradiated black pepper was studied by electron spin resonance spectroscopy. To analyze the time-dependent evolution process, we used the theory of transient phenomena, that is, an ordinal differential equation, as well as the nonlinear least squares numerical method. We found that the radical evolution that occurred in the irradiated pepper obeys a single exponential function and yields a unique time constant. The evolution of the organic free radical undergoes a simple reaction process of a single radical species.     

微波加热对马铃薯淀粉颗粒内部水状态及分布的影响

为了明确微波在淀粉物料加热过程中的机制,本实验选取典型B型淀粉-马铃薯淀粉作为研究对象,根据微波加热的升温规律,建立和评价可对照的加热模型,运用低场核磁共振技术,以Carr-Purcell-Meiboom-Gill(CPMG)脉冲序列为手段,通过对微波加热、快速加热和慢速加热等三种加热方式下样品的横向弛豫时间(T2)衰减曲线进行PCA分析,利用多指数回归拟合计算得到T2,从而分析样品内部水分的变化信息,研究微波加热对马铃薯淀粉颗粒内部水状态及分布的影响。结果表明三种加热方式对样品T2的影响具有显著性差异,具体表现为在糊化前期及糊化刚开始阶段,微波加热对马铃薯淀粉颗粒内水分分布有显著影响,本实验一定程度上证明了微波的特殊效应在该阶段对马铃薯淀粉内氢键的破坏有促进作用。     

胡萝卜、油菜的通电加热烫漂研究

研究了通电加热烫漂对胡萝卜、油菜中维生素含量的影响,并与普通电炉加热进行了比较;研究了胡萝卜、油菜通电加热烫漂的最佳工艺条件。实验证明,随着烫漂时间的延长,胡萝卜中的β-胡萝卜素含量明显降低,油菜中VC的含量也明显降低;通电加热烫漂后的维生素含量明显高于电炉加热;而胡萝卜通电加热的最佳烫漂工艺为,烫漂时间3 min,颗粒尺寸10 mm,料液比(g:mL)1∶4,电压220 V;油菜通电加热烫漂的适宜工艺条件为料液比(g:mL)1∶4,烫漂时间0.5 min,电压220 V。     

源于不同加工条件下大豆分离蛋白的电子顺磁共振分析

分析比较几种不同来源的大豆分离蛋白的电子顺磁共振波谱(EPR)。结果表明:制备工艺条件不同,大豆分离蛋白EPR波谱中场碳自由基信号存在差异。降低蛋白提取过程中豆粕浸提的温度或减少原料脱脂豆粕的残留脂质含量、钝化原料脱脂豆粕中脂肪氧合酶活力,可使大豆分离蛋白中场碳自由基信号显著减弱。     

食品胶协同干热处理对马铃薯淀粉理化特性的影响

为了改善马铃薯淀粉加工特性,选用瓜尔胶、羧甲基纤维素钠和黄原胶3种食品胶分别与马铃薯淀粉复配后进行干热处理,研究食品胶协同干热处理对马铃薯淀粉糊化、老化和流变特性的影响.研究发现,中3种食品胶协同干热处理均能够降低糊化温度与糊化焓,并且均能增强淀粉体系稳定性,使其呈现出弹性流体性质,不仅如此还均能提高淀粉糊热稳定性以及...     

利用光谱技术分析加热温度对肌红蛋白结构的影响

以肌红蛋白纯溶液体系为研究对象,利用紫外-可见吸收光谱、荧光光谱、圆二色(CD)光谱为分析手段,研究了60~80℃的加热处理对肌红蛋白结构的影响。结果表明,80℃加热时,肌红蛋白的紫外-可见吸收光谱特征峰吸光值发生显著降低(p<0.05),荧光光谱最大发射峰的荧光强度显著增加(p<0.05),表面疏水性显著增高(p<0.05),二级结构中的α-螺旋含量显著降低(p<0.05)。而60、70℃加热处理对肌红蛋白二、三结构的影响较小。肌红蛋白对于70℃及以下的加热具有一定的耐受性,但随着加热温度由60℃升高至80℃,肌红蛋白的变性程度、血红素脱离程度、三级结构展开程度以及二级结构的无序化均呈增大趋势。表明70℃以上的加热会严重影响肌红蛋白的结构。