Persian gum: A comprehensive review on its physicochemical and functional properties

Highlights

• Persian gum is a plant exudate of diverse food applications.

• Molecular structure and physicochemical features of Persian gum are presented.

• Assorted important functional properties of Persian gum are discussed.

• Potential applications of Persian gum in food processing are appraised.

Abstract

Persian gum is an exudate polysaccharide from the trunk and branches of wild almond tree which has recently attracted the attention of many researchers owing to its unique properties and the diverse possible applications it may find in the food industry. This article provides a comprehensive review on the physicochemical, structural and functional characteristics (e.g., emulsifying properties) of the gum and introduces a number of attempts made with the view to use it for improving the flow behavior, texture or shelf life stability of food products.

Introduction

Gums are a group of polysaccharides which are categorized amongst the most popular ingredients commonly used in the food industry for a wide range of applications including viscosity enhancement, texture improvement, foam and emulsion stabilization, film formation and coating purposes. This along with the great attention of consumers towards healthier and natural foods in the recent decades has led to an increasing global demand for natural gums of appropriate functional properties and thus has encouraged the researchers to seek new resources of gums. Of the various potential resources, the plant kingdom owing to the great diversity of its species has often been considered as one of the most important choices to meet this goal. A large number of natural gums have been studied over the last decades (Balaghi et al., 2010, Dakia et al., 2008, Dhami et al., 1995, Funami et al., 2009, Kang et al., 2015, Osman et al., 1995, Rinaudo, 2006, Thrimawithana et al., 2010) but only a few have successfully been commercialized and launched on to the market (Katzbauer, 1998, Osman et al., 1993, Ramaswamy and Basak, 1992).

Persian gum (PG) as implied by its name is a natural polysaccharide obtained from wild almond trees that are mainly native to Iran. Also known as Mountain almond, Prunus scoparia Spach (Amygdalus scoparia Spach), it is one of the most important shrubs of Zagros forests which are scattered throughout the vast areas of natural arid and semi-arid woodlands of Iran (Heidari et al., 2008, Salarian et al., 2008). The seeds of P. scoparia are consumed by locals as a cheap and high quality protein supplement (Heidari et al., 2008). The Prunus genus of the Rosacea family consists of peach, plum, apricot, cherry, and almond trees. They all secrete a viscous substance in response to environmental stimulations or when cut or scratched. The exudate gum from the trunk or branches of wild almond tree is called PG (the main source). The exudate from the other genus of the Rosacea family, Amigdalus reuyterie, is also known as PG but commercially it is of unimportance (Abbasi & Rahimi, 2015).

PG has also been introduced as Zedo or Angum gum in some scientific publications and may even be known by the local names of Shirazi, Jedo, Zed and Ozdu (Rahimi & Abbasi, 2014). This gum is a transparent, semi cloudy odorless exudate which can be found in different shapes such as large granules, sugar crystals and powder with diverse colours varying from white to brownish red (Fig. 1). The exudates obtained from thin incisions on the trunk that are usually in the form of striated nodules or tears are rather of higher quality than those secreted naturally as a protection against mechanical damages, beetle attacks and changes in climate. The gum is harvested manually over June–September and dried under direct sunlight. Each square meter of canopy of mountain almond tree can produce about 20–50 g of dried PG. Iran’s annual production exceeds 400 metric tons (Abbasi & Rahimi, 2015).