豆浆中抗营养因子的去除方法

采用碱液浸泡、微波处理、加热处理、去皮等方法,对去除豆浆中抗营养因子的效果进行比较。其中,88℃恒温热处理10min可将豆浆中脂肪氧化酶活性降至常温下的14.20%,100℃恒温热处理20min可将豆浆中的胰蛋白酶抑制剂降低到9.96%。微波处理(2450MHz,800W)2min可以将脂肪氧化酶活性降至8.86%,处理8min可以将胰蛋白酶抑制剂活性降低到11.24%,处理4min即可将尿素酶活性降低至1%。相比于常规的热处理,微波处理可以更快速地破坏豆浆中的抗营养因子,缩短处理时间。此外,采用0.5%NaHCO3溶液浸泡、去皮等措施也可去除豆浆中的抗营养因子,可结合常规热处理、微波处理应用,以缩短加工时间。     

响应面法优化未浸泡脱皮大豆湿热灭酶工艺

为改善豆浆风味,采用湿热(热烫)处理对未浸泡脱皮大豆脂肪氧化酶(LOX)进行灭活。讨论了热烫温度、时间和pH值对脱皮大豆LOX酶活以及豆浆蛋白含量的影响,在此基础上设计响应面试验,通过分析得出最佳工艺：加热温度(94±2)℃、加热时间4min、pH(8±0.5),可以在保证较高蛋白含量(3.60%)的基础上使脂肪氧化酶失活。     

豆浆制备过程中大豆脂肪氧化酶的抑制与豆腥味量的关系

探讨大豆加工制备豆浆的过程中,有效抑制大豆脂肪氧化酶对降低豆腥味量的影响,为生产低含量豆腥味的豆浆提供理论与技术支持.通过抑制大豆脂肪氧化酶实验,即热水研磨大豆、热处理或化学处理大豆原料后再沸水研磨、大豆脱皮后隔氧研磨,对得到的豆浆样品采用静态顶空气相色谱质谱法测定13种豆腥味物质,比较定量数据获得最佳抑制脂肪氧化酶的...     

大豆萌发期脂肪氧化酶与脲酶活性变化及钝化方法效果评价

为探究大豆萌发期抗营养因子含量变化规律及钝化方式,以黑龙江地区的黑科56、黑农71为原料,测定此两种萌发大豆在不同萌发时间阶段中脂肪氧化酶和脲酶两种抗营养因子的活性变化,并在萌发20 h酶活性至最低时,分别以烘烤、微波、沸水漂烫3种方法处理萌发豆,比较对脂肪氧化酶与脲酶的钝化效果,筛选出适宜的钝化方式并确定其工艺参数。结果表明,萌发20 h黑科56与黑农71脂肪氧化酶活性分别为100.8 U和99 U,脲酶活性分别为4.73 U/g和4.82 U/g;钝化方式效果最佳为沸水漂烫,其工艺参数为:沸水漂烫40 s,两个品种与未漂烫的大豆相比,脂肪氧化酶活性均降低至10.9 U;脲酶活性分别降低至0.18 U/g(黑科56)和0.13 U/g(黑农71)。通过顶空固相微萃取-气相色谱-质谱联用法对钝化后的两种萌发大豆主要豆腥味物质进行了定性、定量分析,且得出脂肪氧化酶活性与豆腥味物质含量呈极显著正相关。     

大豆脂肪氧化酶酶活性变化研究

采用分光光度法对大豆中三种脂肪氧化酶（同工酶）进行检测并测定脂肪氧化酶活性,研究表明：大豆粉碎后随着贮存时间的延长,脂肪氧化酶活性逐渐降低,大豆发芽后脂肪氧化酶活性降低了43%.     

微波和热力处理对莲藕多酚氧化酶活性的影响

以莲藕多酚氧化酶为材料,研究莲藕多酚氧化酶经微波和热力处理后,其酶活力的变化。结果表明:(1)当微波的功率一定时,处理时间越长,酶活性降低得越明显。(2)当微波的功率改变时,微波处理功率越大,莲藕多酚氧化酶活性抑制效果越好。(3)当热处理温度一定时,延长作用的时间,酶活性下降趋势越显著。(4)当热处理温度变化时,温度越高,酶活性钝化所需时间越短。     

豆浆的通电加热

研究了温度和固形物含量对豆浆电导率的影响，以及固形物含量和施加电压对豆浆通电加热速率的影响。实验证明：豆浆电导率随温度和固形物含量的增高而增大，且电导率与温度为线性关系；加热速率随施加电压和固形物含量增大而加快，豆浆的温度与时间为指数关系。     

豆腥味的去除技术探讨

据国外资料报道,脂肪氧化酶是造成豆腥味的主要原因,因而种种防止豆腥味的方法是钝化脂肪氧化酶。下面介绍十四种除去豆腥味的方法:1.把去皮大豆浸泡在pH 7.5-9.5的水中,再换以pH7.5-9.5的水加热,滤水后接种纳豆菌入室繁殖,加pH7.5-9.5的水磨碎、过滤、杀菌得豆浆。2.将大豆在90-120℃的温度下加热5分钟,浸泡后在pH9以上的碱性条件下磨碎而成原浆,从中分离出豆浆。     

欧姆加热的电参数对杀菌效果的影响

采用欧姆加热杀菌与水浴加热杀菌对比的方法。以豆浆的总菌数为试验菌群,通过改变电源的电压和频率,得出电源的电压和频率与杀菌效果的关系。对比水浴加热杀菌的效果可知:当电压超过60V时,欧姆加热方法的杀菌效果明显好于水浴加热方法的杀菌效果,残菌率随处理电压的增加以指数规律减少;随着频率的增加,欧姆加热的杀菌好,但当频率超过一定值时杀菌效果降低;频率在30～300Hz时其杀菌效果明显优于水浴加热方法的杀菌。     

大豆脂肪氧化酶的化学法抑制的探讨

根据大豆脂肪氧化酶的分子结构、组成,利用巯基还原性物质、铁离子络合剂和这两种物质的联用,改变酶分子的空间结构,络合铁离子,干扰氧化还原反应过程中电子的传递,以达到钝化酶的目的。含有家基的强还原性物质可有效地钝化大豆脂肪氧化酶,只用络合剂对酶的影响不大,而当与含硫基的还原性物质联用时可显著提高钝化酶的能力。利用半胱氨酸和柠檬酸联用抑制大豆脂肪氧化酶,在试剂与酶的作用过程中,由于酶处于钝化状态没有附肪酸氢过氧化物产生,因而具有实际使用价值。利用统计学原理建立了半胱酸和柠檬联用抑制大豆脂肪氧化酶的动力学方程。反应曲线和动力学方程均表明酶活性随作用时间呈指数曲线降低;Er=N_0e－(1/7)t     

Effect of Ohmic Heating of Soymilk on Urease Inactivation and Kinetic Analysis in Holding Time

To verify the effect of the ohmic heating on the urease activity in the soymilk, the ohmic heating methods with the different electrical field conditions (the frequency and the voltage ranging from 50 to 10 kHz and from 160 to 220 V, respectively) were employed. The results showed that if the value of the urease activity measured with the quantitative spectrophotometry method was lower than 16.8 IU, the urease activity measured with the qualitative method was negative. The urease activity of the sample ohmically heated was significantly lower than that of the sample conventionally heated (P < 0.01) at the same target temperature. It was concluded that the electrical field enhanced the urease inactivation. In addition, the inactivation kinetics of the urease in the soymilk could be described with a biphasic model during holding time at a target temperature. Thus, it was concluded that the urease in the soymilk would contain 2 isoenzymes, one is the thermolabile fraction, the other the thermostable fraction, and that the thermostable isoenzyme could not be completely inactivated when the holding time increased, whether the soymilk was cooked with the conventional method or with the ohmic heating method. Therefore, the electric field had no effect on the inactivation of the thermostable isoenzyme of the urease.     

欧姆加热杀菌对豆浆中微生物菌落总数的影响

利用响应面法分析方法,优化了欧姆加热技术对豆浆的杀菌工艺参数。在单因素实验的基础上,选择加热温度、电压和电场频率为影响因素,以豆浆中微生物的杀灭率为响应值,利用Box-Behnken实验设计建立数学模型,进行响应面分析。结果表明:3个因素对豆浆中微生物菌群杀菌效果的影响大小次序为:加热温度>电压>电场频率。当欧姆加热的加热温度为82℃,电压为200 V,电场频率为190 Hz时,对豆浆中微生物菌群的杀灭效果最佳,该条件下欧姆加热对豆浆中微生物的杀灭率可达100%,与模型预测值相近;所得方程显著,拟合情况良好。杀菌后豆浆中的微生物残留量远小于1500 CFU/g,符合食品安全的相关规定。研究结果可为欧姆加热杀菌技术在豆浆加工业中的应用提供理论依据。     

高静压技术对豆浆中脂肪氧合酶的钝化效果及其动力学分析

研究了高静压技术(HHP)对豆浆中脂肪氧合酶(LOX)活性的钝化作用,并进行失活动力学分析。结果表明:HHP处理能显著钝化豆浆中LOX活性。用300～600MPa压力处理5～20min,对LOX活性有显著的钝化效果(P<0.05),并且随处理压力和处理时间的增加,酶的失活率提高。当压力500MPa,保压时间0min时也有一定的钝化LOX效果;当压力600MPa处理10min以上,豆浆LOX活性被完全抑制。用500MPa处理5min,可以达到与传统巴氏杀菌相同的钝酶效果(P>0.05)。HHP技术钝化豆浆LOX的过程可用一级动力学模型拟合(R2>0.900)。随着压力的升高和处理时间的延长,k值逐渐升高,D值逐渐减小;动力学参数ZP和Va分别为125.94MPa和-45.290cm3/mol。HHP技术在钝化豆浆中脂肪氧合酶活性方面比传统巴氏杀菌彻底,效果更好。其在改善豆浆品质方面具有良好的应用前景。     

Ohmic Tempering of Frozen Potato Puree

Frozen potato puree samples were tempered using an ohmic heating technique. Three salt concentrations (0.50, 0.75, and 1.00 %) and three frequency levels (10, 20, and 30 kHz) were used as experimental variables, and the effects of salt concentration and frequency on ohmic tempering were investigated. Temperature, electrical current, and voltage were measured during the ohmic tempering. Electrical conductivities were evaluated based on the sample geometry and the ohmic heating principle. Increasing the salt concentration and/or frequency increased the electrical conductivity and heating rate, and hence contributed to decreasing the tempering time for the frozen potato puree samples. The tempering time was lowest with the highest salt concentration employed, and longest for the lowest salt concentration and frequency. Temperature differences within the sample during ohmic heating were found to be lowest when employing 0.50 % salt concentration and 10 kHz frequency.     

Milk fouling at direct ohmic heating

Direct ohmic heating (Joule’s heating) is a technology to warm up the food using an electric energy where electric current is passed through a material which gets heated by virtue of its electrical resistance. Advantages over conventional indirect heating methods are speed and uniformity of heating. On the other side, the direct ohmic heating of liquid foods has some problems, for example corrosion and deposits creation on electrodes (fouling). The present research on fouling concentrates upon the effects of material and surface properties of electrodes, and upon the effect of power frequency. This work evaluates influence of material (stainless steel, TiN and graphite electrodes), flow rate, electric current density (at constant frequency 50 Hz) and temperature (in a limited temperature range 65–75 °C), upon the fouling of skimmed milk. Results prove that the stainless steel electrodes are the worst while the graphite electrodes, where no fouling was observed, are the best, thus confirming the significant role of corrosion and electrochemical phenomena. The paper analyzes also another phenomenon typical for direct ohmic heating and it is an inner overheating of the formed fouling layer, representing a risk of overburning. Theoretical results show that the most intensive overheating occurs at relatively very thin deposit layers, depending upon the specific electrical conductivity of deposits.     

番茄酱欧姆加热杀菌工艺参数的研究

采用欧姆加热技术对番茄酱的杀菌工艺进行初步研究。选取处理电压、加热温度和保温时间为主要工艺参数,应用三元二次回归正交旋转试验和响应面分析方法并经SPSS11.5和Matlab7.1软件的分析,建立并分析番茄酱杀菌条件的数学模型。结果表明,3个因素对番茄酱杀菌效果的影响大小次序为:处理电压X1>加热温度X2>保温时间X3;最优组合为处理电压60.6V、加热温度60.2℃、保温时间123.5s,此时酵母菌残菌率为0.02%,所得回归方程显著,拟合情况良好。     

液态食品连续欧姆加热的数值模拟

为研究液态食品欧姆加热过程的温度场和速度场分布,实验采用有限元数值计算的方法,对圆柱状加热室中自来水和豆浆的连续欧姆加热过程进行三维稳态数值模拟,分析不同截面加热室速度场和温度场,以及不同流速对加热室的温度分布的影响。加热室中心温度模拟计算结果与参考文献值对比,自来水和豆浆的误差分别为2.32℃和2.65℃,数值模拟很好地预测了自来水和豆浆加热过程中的速度场和温度场。     

Rheological Characteristics of Quince Nectar During Ohmic Heating

Electrical heating of food products provides rapid and uniform heating, resulting in less thermal damage to the product. In this study, ohmic heating as an electrical heating method was applied to the quince nectar by matching the same heating curve of conventional method by changing voltage gradient (10–40 V/cm) at 50 Hz. The change of rheological constants of quince nectar was determined for different holding times (0, 10, 15, 20, and 30 minutes) in the temperature range of 65–75ºC by using concentric type viscosimeter. Shear stress–shear rate data were fitted to the Newtonian, Bingham, Herschel Bulkley, Power law and Casson Models. It was found that Herschel-Bulkley model was the best model to fit the experimental rheogram adequately since higher regression coefficients (R²; 0.9997) and low standard errors (SE; 0.054) were obtained by Herschel-Bulkley equation compared to other model equations. It was concluded that quince nectar showed time independent non-Newtonian pseudoplastic character during heating in the range of 20–75ºC, independent on heating method. The activation energy values were 9.88 ± 3.24 kJ/mol and 10.08 ± 2.53 kJ/mol for ohmic heating and conventional heating respectively. Results showed that there was no electrical effect rather than thermal effects of ohmic heating since similar rheological constants were obtained with both methods statistically (p < 0.05). Ohmic heating could be recommended as an alternative fas heating method for fruit nectars.     

Effect of ohmic heating on electrochemical-thermal parameters and inactivation of Escherichia coli of well water drinkable

The effect of voltage gradient (15–30 V/cm) and holding time (45–150 s) were evaluated on electrode corrosion, energy consumption, thermal performance, pH change, electrical conductivity and inactivation of Escherichia coli in the well water during ohmic heating process. Results showed that the specific energy consumption increased with an increasing voltage gradient. The thermal performance and electrode corrosion were obtained between 67.16 and 75.12% and 0.06–8.32 mg/L, respectively. The pH of treatment samples was higher than the initial samples. The changes of electrical conductivity values were modeled as function of voltage gradient and sample temperature. No survived E. coli was observed at heating condition of 30 V/cm - 150 s.     

欧姆加热对嗜酸耐热菌的杀灭作用研究

本实验探讨了欧姆加热对嗜酸耐热菌的杀灭作用。利用自行设计的批式欧姆加热装置,对苹果汁中嗜酸耐热菌进行处理,分析了欧姆加热的电压、pH值、时间及加热体积等对杀菌效果的影响,并利用扫描电镜观察微生物细胞壁膜结构的变化,利用电导率仪和紫外吸收分光光度计测定菌悬液的成分变化。结果表明欧姆加热可以有效的杀灭苹果汁中的嗜酸耐热菌,杀菌率随电压、加热体积的升高而增大,随pH值的降低而增大。通过环境扫描电镜可观察到嗜酸耐热菌的表面出现凹陷和破损,电导率仪和紫外吸收分光光度计测定细胞内容物的溢出,据此推测欧姆加热造成了嗜酸耐热菌的"电穿孔"。