Quality and antioxidant properties of instant noodles enhanced with common buckwheat flour

Abstract

The objective of this study was to investigate the feasibility of incorporating common buckwheat (Fagopyrum esculentum Moench) into instant noodle formulations. Australian Soft (AS) and Baker's flours were used to evaluate the effects of varying buckwheat contents (0–40%) on noodle quality. The results of texture analysis indicate that noodles made using AS flour produced softer texture whereas there was minimal effect for Baker's flour when buckwheat was incorporated. The colour, measured by L* values, decreased with increased addition of buckwheat for both flours. Fat uptake for noodle samples made from AS flour was only marginally affected, but increased for Baker's flour, when higher levels of buckwheat flour were added. The antioxidant rutin was detected in noodles made from both wheat flours, generally increasing with % buckwheat flour added. These findings indicate that the incorporation of 20% buckwheat into the formulation can be used to enhance the quality of instant noodles.

Introduction

The pseudocereal, common buckwheat (Fagopyrum esculentum Moench), is a member of the Polygonaceae. The crop originated in China and is now widely cultivated for its value as a food ingredient. Buckwheat proteins are known for their well-balanced amino acid content (Ikeda and Asami, 2000) and are particularly rich in essential types (e.g., lysine and arginine). In addition, buckwheat proteins have high globulin and albumin contents, and are low in glutelin and prolamin (Pomeranz and Robbins, 1972). Based on chemical and immunological studies, buckwheat protein is a valuable dietary component for gluten sensitive individuals including those with coeliac disease.

Several flavonoids have been identified in buckwheat, i.e. rutin, quercetin, quercitin, kaempferol, orientin/isoorientin, and vitexin/isovitexin (Cai et al., 2004). The flavonoids from buckwheat were found to be effective in reducing blood cholesterol levels, keeping capillaries and arteries strong and flexible, improving blood microcirculation as well as protecting blood vessels from rupturing or forming clots (Cai et al., 2004; Griffith et al., 1994). These flavonoids also demonstrated antioxidant, antimicrobial and anti-inflammatory activities (Cai et al., 2004).

Of these flavonoids, rutin (vitamin P) is the major and most important flavonoid component in buckwheat, and is not found in the cereal grains (Holasova et al., 2002; Oomah and Mazza, 1996). Different cultivars of buckwheat may have varying contents of rutin (Ohsawa and Tsutsumi, 1995). According to Lin et al. (2009), buckwheat enriched food can provide beneficial health effects while preventing oxidation during processing. This is due to the natural antioxidant properties of rutin which may inhibit lipid peroxidation within the food.

With these therapeutic and functional benefits, a variety of food incorporating buckwheat have been produced and are widely consumed in China, Japan, Korea and Bhutan. For example, in Japan, soba noodles made with buckwheat flour are popular (Ikeda and Asami, 2000). Other products in which buckwheat has been blended with grains include multigrain pasta, bread, pancakes and cereal flakes, and research has been carried out to determine its suitability for use in such products.

Past studies found that spaghetti containing dark buckwheat and amaranth had significantly lower firmness values compared with that made with durum flour only (Rayas-Duarte et al., 1996). In a later study, Chillo et al. (2008) demonstrated that spaghetti colour changed with the addition of buckwheat flour, while the spaghetti cooking properties (cooking loss and cooking resistance) were similar to those of control samples. In another study, Lin et al. (2009) found that white bread enhanced with buckwheat was rated higher for flavour and mouth feel. The enhanced product also contained more rutin and quercetin which increased antioxidant activity.

Research on food production methods indicates that rutin retention is affected by the activity of the rutin degrading enzyme, flavonol 3-glucosidase as well as certain processing parameters (Kreft et al., 2006). Rutin degrading enzyme has been found in common buckwheat grain, particularly in the testa (Suzuki et al., 2002). Kreft et al. (2006) reported that hydrothermal treatment of buckwheat grain during the production of groats reduced rutin content. Their research indicated that rutin may have been degraded or combined with some other molecules, rendering it insoluble in the solvent used for analysis.

We have recently reported upon the addition of various ingredients (including microbial transglutaminase, emulsifier, water, acetylated potato starch and gum) into instant noodle formulations (Choy et al., 2010, Choy et al., 2012). It was found that the additional ingredients had a major impact on the textural and physical attributes of instant noodles particularly those made from lower protein wheat flour. However, there appear to have been no published studies on the addition of buckwheat into the formulations for this increasingly popular food. Accordingly, this study investigated the suitability of incorporating buckwheat flour into instant noodles. The eating quality (textural, colour and cooking attributes) and the presence of key antioxidant components were investigated to determine the influence of buckwheat in instant noodles.