Buyel Johannes F, Gruchow Hannah M, Wehner Martin
Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.; Institute for Molecular Biotechnology, RWTH Aachen University;
Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.
J Vis Exp. 2017 Jan 7(119):54835. doi: 10.3791/54835.
Plants can produce valuable substances such as secondary metabolites and recombinant proteins. The purification of the latter from plant biomass can be streamlined by heat treatment (blanching). A blanching apparatus can be designed more precisely if the thermal properties of the leaves are known in detail, i.e., the specific heat capacity and thermal conductivity. The measurement of these properties is time consuming and labor intensive, and usually requires invasive methods that contact the sample directly. This can reduce the product yield and may be incompatible with containment requirements, e.g., in the context of good manufacturing practice. To address these issues, a non-invasive, contact-free method was developed that determines the specific heat capacity and thermal conductivity of an intact plant leaf in about one minute. The method involves the application of a short laser pulse of defined length and intensity to a small area of the leaf sample, causing a temperature increase that is measured using a near infrared sensor. The temperature increase is combined with known leaf properties (thickness and density) to determine the specific heat capacity. The thermal conductivity is then calculated based on the profile of the subsequent temperature decline, taking thermal radiation and convective heat transfer into account. The associated calculations and critical aspects of sample handling are discussed.
植物能够产生诸如次生代谢产物和重组蛋白等有价值的物质。通过热处理（烫漂）可以简化从植物生物质中纯化后者的过程。如果详细了解叶片的热性质，即比热容和热导率，就可以更精确地设计烫漂设备。这些性质的测量既耗时又费力，并且通常需要直接接触样品的侵入性方法。这可能会降低产品产量，并且可能不符合诸如良好生产规范等的控制要求。为了解决这些问题，开发了一种非侵入性、非接触式方法，该方法能在大约一分钟内测定完整植物叶片的比热容和热导率。该方法包括向叶片样品的一小区域施加一个具有确定长度和强度的短激光脉冲，从而引起温度升高，使用近红外传感器对该温度升高进行测量。将温度升高与已知的叶片性质（厚度和密度）相结合来确定比热容。然后，在考虑热辐射和对流热传递的情况下，根据随后温度下降的曲线计算热导率。文中还讨论了相关的计算以及样品处理的关键方面。
