Elsevier

Journal of Food Engineering

Volume 186, October 2016, Pages 1-9
Journal of Food Engineering

Physicochemical properties of hydrothermally treated glutinous rice flour and xanthan gum mixture and its application in gluten-free noodles

https://doi.org/10.1016/j.jfoodeng.2016.03.033Get rights and content

Highlights

  • Hydrothermally treated polysaccharide mixtures (HTT-PSM) were prepared.

  • Lower gelatinisation temperature and higher peak viscosity of HTT-PSM were observed.

  • Rice dough incorporated with HTT-PSM exhibited higher extensibility.

  • Similar tensile strength and texture profile for gluten-free and wheat noodles.

  • Overall texture acceptance in gluten-free noodles in sensory evaluation.

Abstract

This study reported a quality improver of gluten-free food formulated using hydrothermally treated polysaccharide mixtures (HTT-PSM) of glutinous rice flour and xanthan gum at different concentrations. The pasting and viscoelastic properties were determined by rapid visco analyser and rheometer respectively. The results showed that HTT-PSM had a lower gelatinisation temperature, higher peak viscosity and weaker gel strength than native glutinous rice flour. The incorporation of HTT-PSM into rice dough decreased the dough development time and stability significantly; and increased its extensibility from 2.8 mm to 11.9 mm. Its high extensibility attribute enabled the dough to make gluten-free noodles with higher tensile strength and similar texture profile as compared to wheat noodles. Sensory evaluation showed that the overall texture of the gluten-free noodles was acceptable, but not as comparable to wheat noodles. Positive correlations were observed between xanthan gum content and peak viscosity, gel strength, noodle tensile strength, hardness and chewiness.

Introduction

The prevalence of coeliac patients and consumers' perceptions of gluten-free products as healthier alternatives have resulted in an increasing demand for a wider range of gluten-free products. Gluten confers elasticity and extensibility to the dough, and contributes to the retention of shapes of many food products such as noodles and baked confectioneries. The lack of gluten leads to a fragile and crumbly dough with poor processibility, and therefore, poses a big problem to the food industry. Moreover, gluten-free products often lack resilience and other textural attributes which are desirable to consumers.

Pregelatinised starch-based flour has been widely used as a texture improver in many food products. Cham and Suwannaporn (2010) and Hormdok and Noomborm (2007) used pregelatinised rice flour to improve the textural properties of rice noodles. Hydrothermal treatment, one of the most common methods to produce pregelatinised starch-based flour, has been widely studied. It was reported that hydrothermal treatment changed the X-ray pattern, swelling factor, crystallinity, starch chain associations, acid and enzymatic hydrolysis of various starches (Hoover and Manuel, 1996, Ozcan and Jackson, 2003). These changes affect the granular rigidity, gelatinisation and retrogradation, as well as gel structure, stability and hardness of starch (Takaya et al., 2000).

Several studies had conducted to prove that non-starch polysaccharides (NSP) can be incorporated into gluten-free flours to improve the textural properties of food products. Inglett et al. (2005) used an oat hydrocolloidal fibre to improve the binding qualities of noodles made with rice flour. Modified starch, xanthan gum (XG) and locust bean gum had also been used to improve texture and reduce changes of flavour in pasta made from pea flour (Gallagher et al., 2004). Lazaridou et al. (2007) used NSP such as pectin, carboxymethylcellulose (CMC), agarose, XG and oat β-glucan to improve the storage modulus and elasticity of rice flour dough for gluten-free bread.

Different types of NSP and starch-based flours are mixed to improve the characteristics of starch-based products. Lim et al. (2002) found that dry heating with sodium alginate, CMC or XG changed the paste viscosity of waxy maize and potato starches. XG provided the most substantial changes among these three gums. Chung et al. (2007) claimed a continuous increase in pasting viscosity of waxy rice starch when heated with phosphate salts and XG. Li et al. (2013) reported that crosslinking between starch granules was formed by xanthan polymers when XG and waxy rice starch were mixed and dry-heated.

Starches with varying amylose/amylopectin ratios and from different sources bring about different physical, textural and pasting properties during and after cooking (Champagne, 1996). According to a comprehensive review written by BeMiller (2011), many works have been done on the mixtures of hydrocolloids and starch-based flours from different sources including corn, wheat, potato, sweet potato, rice and etc. However, glutinous rice, with its unique sticky texture upon gelatinisation (due to high amylopectin content), has not been widely reported. The aim of this study was to manipulate the physicochemical properties of hydrothermally treated polysaccharide mixtures (i.e. glutinous rice flour and XG) in order to improve the textural and sensory quality of gluten-free food. XG was incorporated at different concentrations to study the effect of XG on the properties of HTT-PSM.

Section snippets

Materials

Glutinous rice flour and rice flour (White Elephant Brand, Thailand) used in this experiment was provided by D'Cake Pte Ltd, Singapore. Xanthan gum (XG) (Versagum 200, Cargill) was obtained from a local distributor, Tosu Supplies Trading, Singapore.

Preparation of hydrothermally treated glutinous rice flour and polysaccharides mixtures

Hydrothermally treated glutinous rice flour (HTT-GRF) was prepared according to Bielskis et al. (1989) with modifications. Native glutinous rice flour (NGRF) and water were mixed in a cooking mixer (UM-SK5, Stephan, Germany) at powder to water ratio

Effect of hydrothermal treatment on pasting properties of glutinous rice flour

As seen in Fig. 1, NGRF exhibited increase in apparent viscosity at 67.5 °C. It was reported that during gelatinisation, water was absorbed into the amorphous region and the starch granules swelled upon heating. The swollen starch granules ruptured as the temperature increased further, and more soluble amylose leached out of the solution. Water then continued to enter the tightly bound amorphous regions of double helical structures causing the amylopectin to swell and resulting in crystalline

Conclusions

HTT and XG incorporation greatly altered the physicochemical properties of NGRF, making it capable to improve the texture of gluten-free dough and foods. HTT changed the pasting properties of NGRF, where HTT samples exhibited its cold water swelling capability. The addition of XG caused an apparent increase in peak viscosity, and increasing XG concentrations caused the PV to increase significantly. HTT samples formed weaker gels as compared to NGRF under oscillatory test. The addition of XG

Acknowledgement

The authors would like to express their gratitude to Singapore Polytechnic as the hosting institute, as well as the Ministry of Education, Singapore (Grant No: MOE2012-TIF-2-G-014) for the financial support for this research work. The authors would like to thank Associate Professor Kelvin Goh for sharing his expertise and technical knowledge on this work; and also thank Dr. Ken Lee for his professional suggestions and kind help.

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