【作者】 刘成海；

【导师】 郑先哲；

【作者基本信息】 东北农业大学 ， 农业机械化工程， 2010， 博士

【摘要】 黑加仑果实富含多种营养成分,风味独特,黑加仑制品是市场潜力很大商品。采用微波真空膨化方法加工的黑加仑脆片是一种新型的浆果制品,营养成分保留率高,口感酥脆。本研究通过单因素试验,分析了不同因素对黑加仑微波真空膨化特性的影响规律,并利用计算机仿真技术构建出膨化过程中果片温度、水分及形状变化的数学模型,得到以下结论:1.在膨化时间方面:随着微波强度及微波功率的增加,果片膨化时间减少;随着真空压强的增加,膨化时间先增加后减少;而随着初始含水率的增加,膨化时间增加。2.在果片水分变化方面:在膨化过程的前10 s,果片处于加速脱水阶段。此后,初始条件不同,脱水速率也不相同。当初始含水率为25%或真空压强为15 kPa时,果片处于恒速脱水阶段;当初始含水率为35%,或真空压强为30 kPa,或微波功率为0.93 kW,或全部微波强度水平时,果片先恒速脱水,而后降速脱水;当微波功率为1.57 kW和2.48 kW时,果片先处于加速脱水阶段,而后变为降速脱水阶段;当初始含水率为45%时,果片先降速脱水,而后恒速脱水;而当真空压强为45 kPa时,果片先处于加速脱水阶段,之后进入恒速脱水阶段,最后变为降速脱水阶段。3.在果片温度变化方面:随着膨化时间的增加,果片的温度不断上升,而温度上升速率逐渐减小。4.在果片形态变化方面:除微波功率为2.48 kW时,果片膨化过程分为前期的体积迅速膨胀和后期的体积恒定两个阶段外,在其他因素水平下,果片的膨化过程均可分为三个阶段:第一阶段,在膨化过程的初期,果片体积不变,但形状发生变化,果片直径增加,厚度减少,而45 kPa的真空压强在此阶段则出现果片厚度和直径减小,体积收缩的现象;第二阶段,果片体积急剧膨胀,膨化率迅速增加,果片的直径迅速减小,厚度迅速增加;第三阶段:在膨化过程的中后期,果片直径、厚度和体积无明显变化,而真空压强较高或较低时,果片在此阶段均出现体积收缩现象。5.计算机模拟仿真:根据傅里叶传热方程,模拟出果片的温度变化规律,得出:随着时间的增加,果片的温度逐渐增加,并且前期温升较快,后期较慢;对于同一时刻来说,果片的温度由内到外逐渐升高。根据水分扩散方程,模拟出果片水分的变化规律,得出:随着时间的增加,果片含水率下降;在任意时刻,果片各处的水分扩散速度相同,含水率没有差异。根据应力-应变的形变方程,模拟出果片形状的变化过程,得出:果片在前10 s时,轴向发生收缩,之后开始膨胀。对比研究了微波膨化和微波真空膨化两种方式加工出黑加仑脆片的品质,结果表明:与微波膨化相比,微波真空膨化后的脆片体积大,膨化率高,脆片微观组织由许多小分子颗粒组成,结构疏松,层次感强,脆片内部出现中空现象,脆片硬度小,脆性大,色泽明亮,花青素损失少,整体品质明显优于微波膨化后的脆片。本研究通过试验方法确定出黑加仑鲜片的最佳配制方案为绵白糖添加10%,小苏打添加1%。在此基础上,利用中心组合试验方法进行响应曲面分析,得出各因素与膨化后脆片品质的回归模型,并优化出最佳的微波真空膨化工艺参数。1.各因素交互作用对脆片品质指标的影响:在膨化率方面,单因素对其影响程度依次为,初始含水率>微波功率>真空压强>膨化时间,在回归模型中,初始含水率一次项和二次项、及初始含水率与其余三个因素的交互项对膨化率影响显著,其余均不显著;在色泽方面,单因素对其作用顺序为,膨化时间>微波功率>初始含水率>真空压强,在回归模型中,膨化时间一次项,微波功率和真空压强与初始含水率的交互项、及微波功率与膨化时间的交互项,真空压强、初始含水率及膨化时间二次项对色泽的影响显著;在花青素含量方面,单因素对其的影响程度依次为,初始含水率>微波功率>膨化时间>真空压强,在回归模型中,真空压强与初始含水率和膨化时间的交互项,以及初始含水率的二次项对花青素影响达到显著水平;在最终含水率方面和感官分数方面,只有微波功率,初始含水率及膨化时间的一次项对二者的回归模型影响显著,在单因素作用顺序中,对最终含水率的作用大小为,初始含水率>微波功率>膨化时间>真空压强,而对感官分数的作用依次是,微波功率>膨化时间>初始含水率>真空压强;在质构特性指数方面,单因素对其作用顺序为,膨化时间>初始含水率>微波功率>真空压强,在回归模型中,微波功率一次项、初始含水率和膨化时间的一次项与二次项,以及微波功率和初始含水率与膨化时间的交互项对质构特性指数影响显著。2.黑加仑脆片微波真空膨化的最佳工艺参数:微波功率3.35 kW,真空压强23 kPa,初始含水率35.59%和膨化时间100 s,所得结果为:膨化率200%,色泽31.44,花青素47.73,最终含水率10.62%,感官分数9.08,质构特性指数2.51。与理论预测值相比,验证结果最大相对误差小于10%,表明优化参数合理。本文得到的黑加仑果片微波真空膨化机理及最佳工艺参数,可为实际加工提供理论依据和指导,膨化后的脆片可丰富浆果深加工种类。更多还原

【Abstract】 As a kind of berry fruit with rich nutritionous ingredient and special flavor, blackcurrant berry has the great potential market for its products. The blackcurrant snack puffed subjected to microwave vacuum method is a new type of berry’s product. There is high retention rate of nutrition, and the flavor of blackcurrant.In this research, according to the single factor experiment, the influences of the different factors on the characteristics of blackcurrant subjected to microwave vacuum puffing were analysed. And the mathematic models of the temperature, moisture content and shape were developed in the puffing process using computer simulation method. The conclusions were obtained as follows:1. The puffing time of blackcurrant snack decreased with the increase of microwave intensity and microwave power. As the vacuum pressure increasing, puffing time first increased, and then decreased. And the puffing time increased with initial moisture content increasing.2. The moisture content of the blackcurrant snacks were in the period of accelerating dehydration during the first 10 s of puffing process. Thereafter, the dehydration rates were different for the different initial conditions. When the initial moisture content was 25% or vacuum pressure was 15 kPa, the dehydration rate is constant. Under the 35% initial moisture content, or 30 kPa vacuum pressure, or 0.93 kW microwave power, or all levels of microwave intensity, the snacks firstly remained constant dehydration and afterwards were in the decelerating dehydration. When the microwave power of 1.57 kW or 2.48 kW, the dehydration rate was increasing firstly, and then decreasing. Under 45% initial moisture content, the snacks were in the period of decelerating dehydration, and then converted into the constant dehydration. While the dehydration rate was firstly increasing, and then remained the contant up to the decrease at last period under 45 kPa vacuum pressure.3. As the increase of puffing time, the temperature of blackcurrant snack was gradually arising at a slow trend.4. Subjected to the microwave power was 2.48 kW, the puffing process of blackcurrant snack was divided into two periods, the period of volume puffing rapidly and the period of constant volume. For the other factors and levels, the puffing process can be divided into three periods based on the shape change of snack. In the first period, there were no changed in the volume of snack, but the shape was changed, where the diameter was increase and the thickness was decrease. Under 45 kPa vacuum pressure, in this period the thickness and diameter of snack were decreasing, and the volume shrank. In the second period, the volume of blackcurrant snack rapidly puffed, the thickness increased and diameter decreased. In the third period, no significant change of diameter, thickness and volume of blackcurrant snack were found. When the vacuum pressure was in 15 kPa or 45 kPa, the volume shrank.5. During computer simulation, the temperature change of blackcurrant snack can be simulated according to Fourier’s equations of heat conduction. The conclusions were that the temperature increased gradually with the increase of puffing time, and the rising rate was faster in the early stage and then was slower in the late stage, accompied with the temperature increasing from inner to outer. The moisture change of snack can be simulated using moisture diffusion equation. The result was that the moisture content of snack was decreasing with time increase. At any time, the moisture diffusion rate is the same in any point of snack, and there was no significant difference. The shape change of snack can be simulated according to stress-strain the deformation equation. It was found that the thickness shrank in the first 10 s before its increasing.A contrasting experiment on the qualities of snack between microwave puffing and microwave vacuum puffing blackcurrant chip was conducted. The results suggested that the the snack producted by microwave vacuum method was superior to that by the microwave method in the quality attributes in terms of volume, expansion ratio, the micro-structure of small molecules, loose and mult-layer structure, the cavity in the inner of chip. The hardness of snack was decreased and its crispness was increased, and the color was lighter, the loss of anthocyanin was decreased subjected to the microwave vacuum puffing.In this research, the optimization prescription, with the addition content of 10% soft sugar and 1% saleratus at weight ratio, respectively, to the blackcurrant fresh slice was obtained. On the basis of the optimization prescription, the regression models between the different factors and puffing qualities were obtained by responding surface methodology, and the optimization process parameters were developed.1. The interaction influence of every factor on quality of chip: The sequence of the effect of single factor on expansion ratio was that initial moisture content >microwave power >vacuum pressure >puffing time. In the regression model, the influences of the monimial and quadratic term of initial moisture content, and the interaction between initial moisture content and the other factors were significant, while the effect of the other terms was not significant on the expansion ratio. For the color, the relation of the single factors showed that the puffing time is the most important factor, followed by microwave power and initial moisture content, and the vacuum pressure is the least important. The results of regression analysis found the significant effects of monimial term of puffing time, the interaction of microwave power and initial moisture content, between vacuum pressure and initial moisture content, as well as between microwave power and puffing time, and the quadratic terms of vacuum pressure, initial moisture content and puffing time. For the anthocyanin content, the initial moisture content is the most important factor, followed by microwave power and puffing time, and the vacuum pressure is the least important. In the regression model, the interaction of vacuum pressure and initial moisture content, between vacuum pressure and puffing time, as well as the quadratic term of initial moisture content had significant influence on anthocyanin content. For finial moisture content and sensory score, the monimial and quadratic term of microwave power, initial moisture content and puffing time had significant effect. Accordint to the relation between single factors and finial moisture content, the initial moisture content is the most important factor, followed by microwave power and puffing time, and the vacuum pressure is the least important. While the sequence on the sensory score showed that microwave power >puffing time >initial moisture content >vacuum pressure. For the texture characteristics index, the sequence of the single factors was that puffing time >initial moisture content >microwave power >vacuum pressure. In the regression model, the effect of the monimial term of microwave power, the monimial and quadratic term of initial moisture content and puffing time, and the interaction between microwave power and puffing time, as well as between initial moisture content and puffing time was significant.2. The optimization process parameters of blackcurrant chip by microwave vacuum puffing were as follow: the microwave power of 3.35 kW, the vacuum pressure of 23 kPa, the initial moisture content of 35.59% and puffing time was 100 s. On the basis of optimization process parameters, the quality results of snack puffed from a verified experiment were that expansion ratio was 200%, the color value was 31.44, the anthocyanin content was 47.73, the finial moisture content was 10.62%, the sensory score was 9.08, and the texture characteristics index was 2.51. Comparing with the predicted values, the maximum relative error was less than 10%. It suggested that the optimization parameters were acceptable.In this research, the mechanism and the optimization process parameters of blackcurrant puffing by microwave vacuum method can be used to guide the practical production. The puffing crips can enrich the kind of berry’s futher processing.更多还原