Investigations of the connection between structure and ice recrystallization inhibition activity of carrageenans

冰重结晶是造成冻品储存过程中品质损失的主要原因之一。这主要与冷冻食品有关，但也与细胞和器官的储存等其他过程有关。因此，使用抑制冰重结晶的物质是非常有意义的。已经证明，卡拉胶是一种通常用于凝胶化的水胶，能够抑制冰的重结晶。然而，以前的研究是通过使用结构未表征的卡拉胶样品进行的。因此，对于负责的结构元素和其他类型的卡拉胶对冰重结晶的抑制作用，我们一无所知。卡拉胶是来自不同藻类的结构复杂的多糖，通常被简单地描述。因此，详细的结构表征是推导结构-功能关系所必需的。为了研究单一结构元素的影响，并在测定冰重结晶抑制活性时获得可比较的条件，还需要对卡拉胶进行化学和酶修饰。本研究的目的是系统地研究结构不同的卡拉胶的再结晶抑制活性。首先，将使用现代色谱和光谱方法来表征各种商业上可用的卡拉胶的多糖结构。根据结果，选择不同的卡拉胶样品用于天然存在的结构元素的改性和卡拉胶制剂中存在的阳离子的改性。此外，还将分离和鉴定重组卡拉胶降解酶，以便对结构复杂的卡拉胶进行更详细的研究，并选择性地修饰单个结构元件。最终，在相同条件下，我们将在所建立的模型体系中考察所有改性卡拉胶样品的冰重结晶抑制活性。这些研究的目的是了解基于卡拉胶结构的冰重结晶抑制活性。分子机理的深入研究将有助于理解其他化合物抑制冰再结晶的机理。此外，结构-功能关系将允许特定使用卡拉胶来抑制冰重结晶，并改进卡拉胶的制造工艺，以获得具有高冰重结晶抑制活性的卡拉胶。

Ice recrystallization is one of the main reasons for quality losses during storage of frozen goods. This is mostly relevant for frozen food, but also for other processes such as storage of cells and organs. Therefore, the use of substances which inhibit ice recrystallization is of great interest. It has already been demonstrated that kappa-carrageenan, a hydrocolloid which is commonly used for gelation, is able to suppress ice recrystallization. However, previous investigations were carried out by using structurally uncharacterized kappa-carrageenan samples. Therefore, nothing is known about the responsible structural elements and the inhibition of ice recrystallization by other carrageenan types. Carrageenans are structurally complex polysaccharides from different algae which are often described in a simplified way. Consequently, a detailed structural characterization is necessary to derive structure-function relationships. To investigate the influence of single structural elements and to obtain comparable conditions during the determination of the ice recrystallization inhibition activity, it is also necessary to chemically and enzymatically modify carrageenans. The aim of this study is to systematically investigate the recrystallization inhibition activity of structurally different carrageenans. Initially, the polysaccharide structures of various commercially available carrageenans will be characterized by using modern chromatographic and spectroscopic methods. Based on the results, different carrageenan samples are selected for a modification of naturally occurring structural elements and for a modification of the cations present in the carrageenan preparations. In addition, recombinant carrageenan degrading enzymes will be isolated and characterized for a more detailed investigation of structurally complex carrageenans and to selectively modify single structural elements. Eventually the ice recrystallization inhibition activity of all modified carrageenan samples will be investigated in an established model system under identical conditions.The goal of these investigations is to understand the ice recrystallization inhibition activity based on the carrageenan structures. It is expected that the insights into the molecular mechanism will contribute to the understanding of the ice recrystallization inhibition mechanism of other compounds. In addition, the structure-function relationship will allow for a specific use of carrageenans to inhibit ice recrystallization and an improvement of carrageenan manufacturing processes to obtain carrageenans with a high ice recrystallization inhibition activity.