Natural polysaccharides experience physiochemical and functional changes during preparation: A review

Highlights

• Polysaccharides underwent physiochemical and functional changes during preparation.

• Their changes commonly occurred in extraction, isolation and dehydration procedures.

• Their changes were mainly due to degradation and interaction with other compounds.

• Their hydrothermal and ultrasonic degradations in preparation may be predictable.

Abstract

The preparation mainly composed of extraction, pre-purification and dehydration is essential for the research and development of natural polysaccharides. The methods or conditions used in the three procedures had significant effects on the composition, structure and function of the polysaccharides obtained. Temperature, pH, enzyme, ultrasound and microwave were the important factors associated with their physicochemical changes. Molecular degradation and intermolecular interaction were two of the main mechanisms responsible for the changes. The degradations of polysaccharides responding to hydrothermal and ultrasonic conditions could be partly descripted by multiple linear regression model, implying the possibility for the prediction and control of polysaccharide degradation. Moreover, the interactions between polysaccharide and other compounds, forming complexes natively or conditionally, could be selectively triggered or eliminated to obtain polysaccharides under certain functions. This work shows new insights into the preparation of polysaccharides, which could benefit the efficient utilization of their natural and modified properties.

Introduction

Polysaccharides are carbohydrate polymers consisting of at least ten monosaccharides linked by glycosidic linkages, which are known as one of the crucial biomacromolecules in the growth and development of living organism (Wang, Hu, Nie, Yu, & Xie, 2016; Yu, Shen, Song, & Xie, 2018). Owing to a broad array of bioactivities and special abilities forming food texture, functional polysaccharides have attracted increasing attention in the last two decades (Fig. 1A). Especially, some of them have been clinically applied for disease treatment and health improvement (Yu et al., 2018). The efficient preparation methods of polysaccharides, mostly focusing on extraction procedure, have been developed first and foremost for their potential applications. Their publication numbers in the topics of “extraction” and “activity” both increased steadily and had a Pearson’s correlation coefficient of 0.991 (P < 0.001) (Fig. 1A). It is suggested that the development of extraction technique greatly contributed to the activity-related studies on polysaccharides (such as pectin, chitosan and glucan), in return, their well-known functions attracted more attentions on the extraction from various resources (Fig. 1B). In short, preparation procedures play a key role in the research and utilization of natural polysaccharides.

To improve the functions of polysaccharides obtained, physical, chemical and biological methods have been widely used to modify their structures (Li et al., 2016). The well-known factors leading to the structural modification, such as high-temperature, acid, alkali, ultrasound, microwave and enzyme, commonly exist in the process of preparation (Table 1). It implies that natural polysaccharides may experience physiochemical changes during preparation, thus resulting in a significant effect on their functions. To obtain polysaccharides with improved functions, it is necessary to understand the effects of preparation method (condition) on them.

As seen in Table 1, the preparation of polysaccharides usually contains three key procedures, i.e. extraction, pre-purification and dehydration. In the present work, the physicochemical and functional variations of polysaccharides, responding to different methods or conditions used in the procedures, were systematically reviewed. Further, the leading factors, potential mechanisms and mathematical models associated with the variations were proposed reasonably. This work aims to fully understand on the changes of polysaccharides caused by preparation, which will benefit more accurate identification on their natural and modified properties, and more efficient preparation of them with enhanced functions.