In situ dynamic rheological analysis of raw yam tubers: a potential phenotyping tool for quality evaluation

Abstract

BackgroundMost rheological analyses in yam have been done on starch gels, which requires starch extraction from the tubers. In situ rheology bypasses the need of starch extraction and relies on the original cell structure and complex matrix organization under stress or strain. Dynamic rheological properties of tuber from 16 accessions belonging to four yam species (Dioscorea rotundata, D. alata. D. bulbifera and D. dumetorum) were investigated for potential use as a medium throughput phenotyping screening tool that can indicate the quality of yam food products or their industrial potentials.ResultsRheographs of the tubers illustrated differences in the structure of D. bulbifera compared to other yam species. High initial storage modulus (G′) of yam parenchyma indicated tubers with strong and rigid structure which do not lose their structural integrity easily on heating. Dioscorea rotundata and D. alata varieties exhibited a lower temperature at which gelatinization took place (Tgel) equivalent to the irreversible transition during starch gelatinization (75.3 and 79.8 °C) and took shorter time (867 and 958 s, respectively) to reach the G′ maximum, compared to other species. The stress relaxation test showed that the higher the dry matter of the tubers, the higher the work to rupture the structure.ConclusionRheological characteristics G′, loss modulus (G″), swelling capacity and Tgel showed potential as suitable quality indicators for yam products. In situ rheological characterization of yam tubers could be used as an instrumental screening tool to phenotype for quality in yam products. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Thermal Properties and Dynamic Rheological Characterization of Dioscorea Starch Gels

“…The frequency-dependent characteristics of starch gels have been reported as typical of weak gels [28]. The lower frequency-dependent characteristic exhibited by D. bulbifera starch gels was probably a result of the formation of a rigid structure [13], which may be more resistant to deformation due to the stress increase or mechanical fragmentation or shear during processing. Previous authors [8,29] reported that the frequency dependence of a starch can provide important information on the structure of the gel.…”

“…Characterizing the dynamic rheological properties of yam starch can thus give an insight into its potential utilization and the scope of its industrial utilization, thus adding value to yam. The pasting characteristics of yam tubers have been characterized [4,12], and the dynamic oscillatory characteristics of raw yam tubers have also been reported [13]. Thermal properties, starch transition temperature and gelatinization enthalpies usually indicate the order-disorder transition that takes place during the heating of aqueous suspension of starch granules.…”

“…Hence, this study was focused on determining the dynamic oscillatory and thermal properties of starch gels from sixteen varieties of four yam species (D. rotundata, D. alata, D. bulbifera and one variety of D. dumetorum) in order to determine their potential utilization for food and non-food applications. Other physicochemical characteristics of these yam starches such as in situ dynamic oscillatory properties, pasting characteristics, digestibility, granule morphology, and particle size analysis have been reported [13,14].…”

“…Differences in the viscoelastic properties of the starch gels or different responses to dynamic moduli may be attributed to their starch granule properties (rigidity and integrity), intergranular interaction such as entanglement between surface molecules of adjacent granules in gelatinized starches and biological origin of the starches and amylose contents [13,34,35].…”

“…T potential of yam starch. Hence, this stud latory and thermal properties of starch rotundata, D. alata, D. bulbifera and one v potential utilization for food and non-f teristics of these yam starches such as in acteristics, digestibility, granule morph ported [13,14].…”