Introduction

Hand stretched Asian noodles are considered to have superior texture properties to those made by mechanical sheeting. The improvement to noodle texture is considered to be due to the combination of higher water addition and a more fully developed gluten network. It has been found that the application of vacuum during dough mixing allows increased water addition for the production of udon noodles (Nakai, 1988). Wu et al (1998) described improved noodle quality from the combination of vacuum mixing and higher water addition.

There does not appear to be any publications describing the interaction of flour quality with vacuum mixing or information quantifying the improvement achieved with vacuum mixing. Given the significant investment in the development of new noodle wheat varieties it is important to determine what influence vacuum mixing will have on the wheat and flour specifications for noodle production.

Materials and methods

Flour samples

Three flours (A, B and C) were used for this work. Their analytical data were presented in Table 1.

Table 1. Flour data

^aProtein content is calculated as N x 5.7,
^bWater absorption
^cDough development time
^dExtensibility

Noodle Manufacture

Flour (1kg, 13.5% moisture), water (320g for conventional mixing and 400g for vacuum mixing) and 20g salt was mixed in a New Tokyo Menki vacuum mixer fitted with a one kg mixing bowl on low speed (40 r.p.m.) for 3 minutes without vacuum. It was then mixed for 15minutes either with no vacuum or with a vacuum of 45 kpa. The final dough temperature varied between 16^oC to 20^oC. The noodle sheet was prepared according to the method described by Konic et al. (1993) The final thickness of dough sheet was 1.25 ± 0.05mm. A piece of noodle sheet (approximately 40cm long) was cut off and placed in a plastic bag and sealed. This sample was used for colour measurement at 0.5 and 24 hr using a Minolta Chroma Meter. The rest of noodle sheet was cut into noodles for texture analyses. The stickiness of noodle sheet during sheeting and after noodle cutting was recorded.

Sensory Evaluation

The eating quality of cooked noodles was evaluated by a trained panel with 6 panelists. A descriptive test was carried out using 15cm line scale ballot. Three noodle quality characteristics - softness, smoothness and elasticity were evaluated for their intensity in comparison with control noodles. In this trial the control noodles were produced from flour B using conventional mixing and a water addition of 32%. The noodle sensory test was at least duplicated.

Establishment of Optimum Cooking Time

Noodles were cooked under the same conditions as that for noodle sensory test. Four noodle samples each weighing 300g) were placed in 4 stainless steel baskets. These baskets were simultaneously plunged into a 15L pot containing 15L of boiling water. Every 30 seconds two strands of noodles from each sample were removed from each cooking basket and placed into a Corningware bowl with 150 ml water (20°C). This operation was repeated until noodles were clearly overcooked. One noodle strand from each bowl was sampled and cut to 3cm in length. These noodle samples were placed on the surface of a light box (Kodak x-ray illuminator, Model 2, Kodak (Australasia) Pty. Ltd. Melbourne Australia). Noodles were considered under cooked if there was a dark core in the middle of noodle strands. Noodles were considered fully cooked when they became totally translucent. Cooking time was selected as the time required for the noodle to first become fully translucent. This optimum cooking time was used to prepare the noodles for texture evaluation.

Results and discussion

Noodles made from flour A were the softest, smoothest and most elastic, whilst noodles made from flour C were the least soft, smooth and elastic under conventional mixing. There was similar quality trend of noodles made from flours A, B and C under vacuum mixing. The softness, smoothness and elasticity of noodles made from A, B and C were all improved by vacuum mixing (Figure 1).

Figure 1. Comparison of textural properties of noodles made from flours A, B and C under conventional and vacuum mixing

Figure 2. Relationship between FSV and noodle texture under conventional and vacuum mixing

The quality parameters for Udon noodles have been relatively well documented (Oda et al., 1980; Toyokawa et al., 1989a and b; Konik et al., 1993; Yun et al., 1997). These parameters are based on starch and protein composition and may be measured using biochemical or instrumental analyses (Oda et al., 1980; Zhao and Sharp, 1995; Crosbie, 1991). Crosbie et al (1992) pointed out that flour swelling volume (FSV) was significantly (p<0.01) correlated with total texture score and its components, namely the balance of softness and hardness, elasticity and smoothness. In the present study, FSV was correlated with noodle texture under both conventional and vacuum mixing conditions. The close relationship between FSV of flour and noodle texture is shown in Figure 2.

Conclusion

The starch properties of flour as measured using the FSV test were shown to have a more significant impact on noodle quality than vacuum mixing with increased water addition. This result demonstrates that to optimise noodle quality, the correct flour choice is critical. Flour with a high FSV is required for the production of soft, smooth and elastic noodles. Once the correct flour has been selected, further improvements in noodle texture can be achieved through the use of vacuum mixing and higher water addition levels. In general the higher water addition reduced cooking time and increased noodle softness, smoothness and elasticity.

Acknowledgements

This project is funded by the Grains Research and Development Corporation and BRI Australia.

References

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