Composition, morphology and pasting properties of Orchis anatolica tuber gum

Abstract

Orchis anatolica (O. anatolica) tuber is commonly used in the production of Salep gum or O. anatolica tuber gum (OaG) for use as a thickener, flavouring agent, gelling agent, film former and emulsifier in the food industry. The aim of this study was to investigate the chemical composition, physical, morphological and pasting properties of OaG. Physical and morphological analyses, and pasting properties of OaG were analysed using static light scattering, scanning electron microscopy, light microscopy and rotational rheometry, respectively. Volume-weighted mean particle diameter (D [4,3]) value of OaG was 180 ± 1.25 μm. OaG was composed mainly of starch (41.6%), dietary fiber (32.3%) and glucomannan (18.5%). The powder of OaG had irregular shaped particles with smooth surfaces and round edges. After pasting treatment, the initial and final viscosity values of the OaG dispersions at a concentration of 0.5% OaG were 33.7 ± 0.24 and 34.3 ± 0.45 mPa.s, whereas, the corresponding values at a concentration of 2.5% OaG were 1193 ± 92.0 and 1437 ± 83.3 mPa.s, respectively. The glucomannan and dietary fiber components and their possible interactions with starch, in OaG appear to have influenced the peak temperature and viscosity on pasting, due to limitation of the leaching of amylose and amylopectin from starch granules. Therefore, O. anatolica tuber gum, a complex biopolymer, can provide interesting and unique functionality to the food industry in the development of novel food structures.