Emerging Natural Hydrocolloids

12 Gum Tragacanth (Astragalus gummifer Labillardiere)

Zahra Emam‐Djomeh^*Morteza Fathi and Gholamreza Askari

Transfer Phenomena Laboratory (TPL), Control Release Center, Department of Food Science, Engineering and Technology, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran

12.1 Introduction

Natural polymers are broadly applied in food, cosmetic, and pharmaceutical systems as edible coating, emulsifying, stabilizing, flavor encapsulating, and viscosifying agents. There is an ever‐growing demand for plant gum exudates due to their structural diversity and metabolic functions. Furthermore, they are non‐poisonous, biocompatible, sustainable, eco‐friendly, and easily accessed [1].

Tragacanth plants belong to the genus Astragalus and are extensively distributed in Southwest Asia (from Greece to Pakistan), especially in the Anatolian region in Turkey and the mountainous regions of Iran [2]. Tragacanth plants have a tap root along with branches characteristic of low bushy perennial shrubs (Figure 12.1). Historically, gum tragacanth (GT) was first introduced by Theophrastus several centuries before Christ. Before the 1970s, Iran exported about 4000 tonnes of GT annually, but in the following years, for some reason, this quantity began decreasing [3]. It has been documented that Astragalus microcephalus is the main source of GT, whereas Astragalus gummifer is the principle gum‐yielding species [4,5]. For well over 2000 years, GT has been applied ...