Effect of NaCl on rheological properties of dough and noodle quality

Highlights

• Addition of NaCl had different effects on the rheological characteristics of different varieties of wheat flour.

• NaCl had no obvious effects on the hardness, springiness, gumminess, chewiness and resilience of noodles.

• Gluten network structure of noodles became more and more dense with the increase of NaCl.

Abstract

To assess the effect of NaCl on processing properties of different varieties of wheat flour and noodle quality, the rheological properties of dough, and the quality of white salted noodles made from three different varieties of wheat flour were evaluated. The results showed that the addition of NaCl had different effects on the rheological properties of different varieties of wheat flour. As NaCl concentration increased, the stability time of both intermediate-gluten and weak-gluten wheat flour increased, while that of strong-gluten wheat flour increased initially and then remained stable. The developing time of strong-gluten wheat flour increased, while those of both intermediate-gluten and weak-gluten wheat flour did not change significantly. The energy values of intermediate- and weak-gluten wheat flour did not change significantly while that of strong-gluten wheat flour increased. NaCl had no apparent effects on the hardness, springiness, gumminess, chewiness and resilience of noodles. The cooking loss of fresh noodles increased positively with increasing NaCl concentration. Microstructure of noodles showed that gluten network structure of noodles became more and more dense with increasing NaCl concentration. The effect of NaCl on gluten protein contributed to the change of rheological properties and noodle quality.

Introduction

For several thousand years, wheat-based noodles have been an important part of human diet in many oriental countries. With the growing interest in ready-to-eat meals, noodles gain popularity outside of Asia (Fu, 2008). Noodles are staple food for more than 12% populations worldwide (Choy et al., 2012) and up to 50% of Asian populations (Rombouts et al., 2014). Depending on the regional preference, noodles differ widely in compositions, preparation methods, and appearance. Common ingredients in oriental noodles include sodium chloride (NaCl), kansui (mixture of sodium and potassium carbonates), and occasionally NaOH, in combination with flour and water (Edwards et al., 1996). Among the varieties, white salted noodles have the most desirable qualities such as taste, color and texture (Ye et al., 2016). White salt noodles are prepared in various formulations and shapes, and the dough is a mixture of wheat flour, water and salt. Noodle quality is typically evaluated based on color, surface appearance, texture, taste and cooking loss. Noodle firmness, cohesiveness, tensile strength and sensory evaluation are considered as the main discriminating factors (Zhou et al., 2013; Rombouts et al., 2014).

NaCl, a major source of sodium in manufactured foods, is added to cereal based food not only to enhance the sensory properties, but also for its impact on the functional properties of cereal constituents (e.g. protein and starch). These constituents contribute to appropriate processing handling and final texture characteristics of food (McCann et al., 2013). Many studies have shown that NaCl could increase the mixing tolerance of wheat flour dough, extend dough development time, and increase dough resistance, elasticity and extensibility (He et al., 1992; Uthayakumaran et al., 2011). Wu et al. (2006) found that NaCl decreased water absorption but increased optimal dough development time and fresh noodle elasticity. McCann et al. (2013) found that dough strengthening effect was partially due to the decrease in water absorption of wheat flour with the addition of NaCl. Furthermore, it improves flavor, color and textural properties of cooked noodles (Fu, 2008; Rombouts et al., 2014).

Wheat proteins have the ability of developing a viscoelastic network when the flour is mechanically blended with water. In turn, the viscoelastic network allows an easy manipulation of dough for fabrication of a wide diversity of specialties (Guadarrama-Lezama et al., 2016). Characterization of dough rheological properties is effective in predicting the processing behavior and in controlling end-products quality. Farinograph, mixograph, and extensograph are the most common empirical instruments used for characterizing dough rheology. Farinograph discloses dough mixing properties; while extensograph explores dough extensional properties (Ding et al., 2013). Tuhumury et al. (2014) found that the presence of NaCl during dough mixing resulted in different molecular conformation and network structure of gluten proteins which contributed to the differences in the rheological properties.

Although there are a lot of research about the components of wheat and their effects on the qualities of wheat flour products, the mechanism of NaCl on the quality of white salted noodle remain largely unexplored. In this study, dough rheological properties and noodle qualities of three different varieties of wheat flour, strong-gluten wheat, intermediate-gluten wheat and weak-gluten wheat, were assessed after adding different amount of NaCl in order to evaluate the effects of NaCl on rheological characteristics of dough, noodle processing properties and noodles quality.