In the present research, tomato juice was concentrated via Ohmic heating with two modes of operation, namely atmospheric condition (OHAC) and vacuum condition (OHVC), and conventional vacuum heating (CVH) as the control mode. The effect of heating conditions on the quality of tomato concentration (lycopene, turbidity, pH and acidity) and electrical conductivity were evaluated. The OHVC reduced the concentration time in the range of 10–30%, compared with the OHAC. The comparison of the mean value of the heating rate indicated that the vacuum application reduced the heating rate by 0.8%. The electrical conductivity of OHAC changed from 0.68 S/m at initiate point to 1.25 S/m at the boiling point then decreased to 1.05 S/m at the end of the process, the corresponding values for OHVC was 0.7, 1.13 and 1.11 S/m. The mean percentage change of pH, acidity, lycopene, and turbidity for OHVC were 0.47, 24.03, 7.99, and −30.77 respectively which were lower to the corresponding value for OHAC and CVH. It appears that the application of vacuum condition in the ohmic heating treatment of tomato juice can preserve juice quality.

Industrial relevance

Due to the high energy consumption of heating in the conventional processing methods, energy efficient systems are demanded for thermal concentration of juices. Ohmic heating is an emerging technology and a very promising in food industries. Comparing with conventional heating processes, ohmic heating can save energy and provide a rapid and uniform heating of pumpable food, resulting a product with a higher quality. The results showed that vacuum coupled with ohmic heating had a significant effect on quality. One of the keys to reducing the thermal damage to products during manufacture is the shortening of the heating time and reducing the boiling point, ohmic-vacuum heating required a lower time and boil at lower temperature, thereby is more advisable for thermal processing from the point of view of energy saving and quality aspects.

中文翻译：

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欧姆真空，欧姆和常规真空加热方法对番茄浓缩汁品质的比较研究

在本研究中，番茄汁通过欧姆加热以两种操作模式进行浓缩，这两种操作模式分别为大气条件（OHAC）和真空条件（OHVC），以及传统的真空加热（CVH）作为控制模式。评估了加热条件对番茄浓度（番茄红素，浊度，pH和酸度）和电导率质量的影响。与OHAC相比，OHVC减少了10-30％的浓缩时间。加热速率平均值的比较表明，施加真空使加热速率降低了0.8％。OHAC的电导率从起始点的0.68 S / m更改为沸点的1.25 S / m，然后在过程结束时降低至1.05 S / m，相应的OHVC值为0.7、1.13和1.11 S / m米 pH，酸度，番茄红素和OHVC的浊度分别为0.47、24.03、7.99和-30.77，低于OHAC和CVH的相应值。看来真空条件在番茄汁的欧姆加热处理中的应用可以保持汁液的质量。

行业相关性

由于常规加工方法中加热的高能耗，因此需要能量高效的系统来对果汁进行热浓缩。欧姆加热是一种新兴技术，在食品工业中非常有前途。与传统的加热工艺相比，欧姆加热可以节省能源并为可泵送食品提供快速，均匀的加热，从而获得更高质量的产品。结果表明，真空加欧姆加热对质量有显着影响。减少制造过程中对产品的热损害的关键之一是缩短加热时间并降低沸点，欧姆-真空加热需要更短的时间并在更低的温度下沸腾，因此从这一点出发，更适合进行热处理节能和质量方面的观点。