Advances in Studies Using Vegetable Wastes to Obtain Pectic Substances: A Review

Abstract

Vegetable waste represents a serious environmental problem for industries; however, it is also a valuable source of pectic substances. This paper aims to highlight the advances that have been made through studies regarding pectic substances from vegetable wastes, as well as providing an overview of the chemical structure of pectin, extraction and characterisation techniques, and potential applications for pectin in relation to the areas of food and health. Pectin is mainly composed of galacturonic acid and it is one of the most complex polysaccharides in nature. A wide range of vegetable wastes contain a high pectin yield that can be industrially utilised. However, factors such as the type of raw material, the maturation stage of that raw material, and the extraction techniques that are used, affect the structural and functional properties of the pectin, as well as influencing its potential application. This study outlines the different environmentally-friendly techniques that are used to extract pectin, such as microwave, ultrasound, enzymatic and other methods, highlighting their advantages and disadvantages compared with the conventional extraction method. Some techniques are advantageous for industrial use; however, it is necessary to optimise the extraction conditions and to make a financial investment in order to obtain a high yield of pectin in a short amount of time. Characteristics such as galacturonic acid content, the degree of methyl esterification, the degree of acetylation, molar mass and the chemical structure are essential parameters required to define possible applications of pectic substances. In vitro and in vivo studies regarding the properties of pectic substances have shown that these substances can be beneficial to health, with antimicrobial, antitumoral, anti-inflammatory and analgesic effects. Nevertheless, further studies are required to examine the mechanisms of action for these effects to be applied in humans. Consequently, greater understanding about the chemical structure of pectin and its extraction techniques are crucial for the development of new foods and drug formulations.