Elsevier

Food Structure

Volume 25, July 2020, 100148
Food Structure

Structural, physicochemical and rheological properties of a novel native starch obtained from Rhizoma Gastrodiae

https://doi.org/10.1016/j.foostr.2020.100148Get rights and content

Highlights

  • The Rhizoma Gastrodiae (RG) starch can be a new source of high amylopectin starch.

  • RG starch displays a characteristic of B-type and had a crystallinity of 45.60 %.

  • RG starch granules presents small size with a median particle size of 1.19 μm.

  • RG starch shows its low pasting temperature and high digestibility.

  • RG starch owns a good capability of swelling power, solubility, anti-aging.

Abstract

Rhizoma Gastrodiae (RG) is traditional medicine and food, widely used in many Asian countries. Extracting starch from RG is a supplementary for the exploitation of new starch sources. The present work aimed to characterize the extracted starch from RG residues concerning its composition, physicochemical, structural and rheological characteristics. The isolated RG starch had notably high amylopectin (AP) content of 92.75 % with a purity of 94.9 %. The RG starch displayed a characteristic of B-type and had a crystallinity of 45.60 %. Color analysis of RG starch indicated its acceptable color characteristics. Particle size and morphology analysis revealed its small size (0.62–1.48 μm). Compared to maize, sweet potato and peas starches, the RG starch exhibited higher swelling power, solubility, digestibility, and lower pasting temperature. The lower setback viscosity and final viscosity suggested its better anti-aging capability. Besides, static rheological measurements of RG starch pastes presented a pseudo-plastic behavior under the measured shear rates (1–500 s−1); dynamic rheological measurements showed that RG starch gels were typical weak gel system and had better long-term stability in a lower concentration. With small granule size, high AP content and low gelatinization temperature, the RG starch showed the unique potential in the food industry.

Introduction

Starch remains a major source of energy in the human diet and is the most common functional ingredient in the food industry (e.g. as thickener, stabilizer, gelling agent). With increasing people’s emphasis on a diversified and healthy diet, the global trend toward developing more bio-based or green-chemical products is raised in recent years. Therefore, there is an increasing interest in exploiting and studying novel starch resources word-wide to meet new consumer and processor market demands. Introducing new starch material sources with interesting characteristics has been attracting the attention of researchers. Researchers have extracted starches from various botanical sources other than traditional cereals, such as bamboo culm (Felisberto et al., 2019), aroid (Zhu, 2016), lotus (Zhu, 2017), lotus seed (Guo et al., 2015), ginger starch (Madeneni, Faiza, Ramaswamy, Guha, & Pullabhatla, 2011), etc. Although few of them is on large-scale industrial application, it still makes sense to cognize available natural resources around us.

Rhizoma Gastrodiae (called Tianma in Chinese) is the tuber of Gastrodiaelata Blume (Orchidaceae). As a traditional medicine and food, it is widely used in many Asian countries for the treatments of diverse diseases, such as convulsion, neurasthenia, headache, ischemia, vertigo, and hemiplegia (Ahn, Jeon, Lim, Jung, & Park, 2007; Chen & Sheen, 2011; Chen et al., 2016). Being a promising food resource, RG could be used in the processing of food products. Kim, Morita, Lee, and Moon (2003) found that the bread baked with RG exhibited a better loaf volume. The fresh RG is always used as the source to obtain phenolic compounds, such as gastrodin, 4-hydroxy benzyl alcohol and parishin B, however, the RG residues are generally discarded without comprehensive utilization. Being a crop residue, the RG is rich in starches with a content approximately about 70 % (On a dry basis) and worthy of a promising but underutilized source (Hoover, 2001). Although RG has been studied and utilized for food and non-food applications for a long history (Jung et al., 2006; Lee, Hwang, Kang, Kim, & Lee, 2009), the starch derived from RG has been overlooked. Furthermore, increasing new and available starch resources from crop residues is desirable under the tendency of sustainable development. Therefore, it would be ideal if the starch in RG could be isolated and used in food processing. Besides, an understanding of structural and physicochemical properties is a prerequisite for using starches from RG. However, to our best knowledge, there is still no reported research on the extraction and properties of RG starch at present, which limits the further application of RG in the food industry. As a result, it’s necessary and beneficial for the comprehensive utilization of RG to extract starch from RG residues and to investigate its physicochemical properties.

Hence, the objective of the present study was to isolate the starch from the non-conventional source of RG residues, and to investigate its structural, physicochemical and functional properties to explore the possibility of its application as a food ingredient.

Section snippets

Materials

RG residues were collected from a Gastrodiae factory located in Bijie, China. Maize starch, sweet potato starch, and peas starch were purchased from Henan Zhengzhou Enmiao Food Co., Ltd. (Zhengzhou, China). All solvents and chemicals used were of AR/HPLC grade and purchased from Kelong Chemical Reagent Factory (Chengdu, China). Glucoamylase (200 U/mL) was purchased from Genencor (Wuxi, China) and porcine pancreatic α-amylase (275 U/mL) was obtained from Sigma-Aldrich.

Starch isolation

RG residues were selected

Starch composition and color analysis

The proximate composition and color parameters of RG starches are presented in Table 1, corresponding values for maize, sweet potato and pea starches determined simultaneously are shown for comparison. Although the total starch content obtained from RG was relatively lower than those of other commercial varieties purchased from the market, the RG starch could be used for further study with a purity of 94.9 % (On a dry basis). It can be calculated that there is a 3 % unknown component, which may

Conclusions

A novel native starch with a notably high AP content (92.75 %) was isolated from RG residues using a simple procedure, suggesting that RG residues can be a new source of the low cost and environment friendly to obtain high amylopectin starch. Compared to starches from other botanical sources, the size of RG starch granules was smaller (0.62–1.48 μm). The high AP content and small granule size of RG starch may be an explanation for its higher swelling power, solubility, better digestibility and

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was supported by ‘Science and Technology Innovation for Social Welfare and People's livelihood in Chongqing’ (grant number: cstc2015shms-ztzx0113).

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