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Pulse incorporation and microencapsulation strategies to enhance the nutritional attributes of Asian noodle products

J. Harvey and D.M. Small

School of Applied Sciences, RMIT University, Melbourne Victoria

Introduction

Asian noodles have become increasingly popular around the world as a product distinct from the popular pasta foods of southern Europe. One of the most common yellow noodles selling in Australian supermarkets and stored under refrigeration is “Hokkien” noodles and these are partially cooked.

Hokkien noodles have the potential to provide enhanced nutrition. As noodles are a staple in the diet of many consumers it is relevant that issues of good dietary balance be addressed. A combination of wheat and pulses provide a full range of amino acids as wheat is low in some amino acids including lysine and tryptophan (Aguilera 1993). A further strategy is the microencapsulation of vitamins (Augustin et al 2001) which may overcome the relatively high losses of these essential nutrients during processing. The aims of this investigation have been to establish and develop the incorporation of pulse flours and microencapsulated B group vitamins in Hokkien noodles whilst maintaining the overall consumer appeal.

Materials and methods

Preparations of microencapsulation by spray drying

Gum solutions were prepared using 1-2% of gum with stirring for an hour. Starch (20%) was added to an equal volume of water with thorough mixing to ensure uniform suspension of the granules at a temperature of 40-50C. This was then added to the gum solution along with 0.5% of the vitamin. The final pH was adjusted to 4.0 and the solution spray dried. A Niro Atomiser minor (Niro, Copenhagen) unit was used and the drying conditions were: flow rate 7-10mL/min, air pressure of 5kg/in2, inlet temperature of 120C and outlet of 80-90C (Trindade and Grosso 2000).

Noodle Formulation

100g of wheat and legume flour, 1mL cooking oil, 10g of capsules, 1% salt solution, was then kneaded and mixed for 15 min. The dough was sheeted and then rested for 30 min. After cutting, noodles were steamed for 8 min. Samples were stored in vacuum packed bags under refrigeration (4C).

Vitamin analysis by HPLC

Samples were taken after the noodles were cooked and analysed in triplicate. Noodles (10g) were homogenized in 1L of 0.01M HCl and autoclaved. The solutions were analysed by HPLC (Esteve et al 2001). Potassium ferricyanide solution was used to oxidise thiamin to thiochrome and o-phosphoric acid was added to reduce the interference when measuring riboflavin simultaneously.

DSC of flour samples

A sample was prepared using 1.00g flour and 2.00mL water, a paste formed and 2.0mg weighed and sealed in a DSC container. This was heated at 10C per minute from 20 to 130C using a Perkin Elmer DSC7 system.

Measurement of pH and protein analysis by Kjeldahl

The pH was tested using 10g of sample and homogenised with 100 mL of distilled water. The protein content of noodles, pulses and wheat were determined using a Kjeltec system with copper catalyst, standardized HCl (0.1M) and an N factor of 5.7.

Results and discussion

Different types of legume flours in various proportions were trialled with wheat flour in producing noodles to obtain acceptable attributes and eating quality. In this study, the overall evaluation was based upon assessments of taste, colour, flavour and textural quality. Of the various pulses studied, mungbean in combination with wheat gave the most acceptable product (Table 1), particularly in terms of colour. The starch characteristics were assessed using DSC (Table 2). These indicate that mungbean starch gelatinizes at a much higher temperature than the others tested.

Table 1 The attributes and quality of noodles prepared with added pulse flour

Type of noodle

Cutting stress (N)

pH

L value

a value

b value

Mungbean/wheat

5.5

6.57

97.09

-0.33

4.86

Lentils/wheat

2.7

6.30

74.28

0.49

19.36

Chickpeas/wheat

2.8

6.40

81.01

-1.57

22.81

Soya/wheat

4.3

6.54

84.11

-1.14

23.08

Commercial 1

4.1

7.80

99.08

-.0.23

4.33

Commercial 2

5.0

7.50

98.01

-0.11

4.54

Table 2 Peak temperatures of gelatinsation of flour samples measured by DSC

Sample starch

Mungbean

Lentil

Chickpea

Wheat

Peak temperature (C)

73.3

67.8

65.9

57.4

Protein was lost from noodles during boiling. This probably reflects the relative solubility of the legume proteins. Several cooking methods were compared to obtain and maintain the food quality value in the noodles and steaming for 8-10 min at approx 80C was found to be optimum.

A number of hydrocolloid gums were used for microencasulation in this study. Different percentages of rice starch were incorporated into the composition of capsules. Riboflavin was mixed into the solution before spray drying. Recovery of the riboflavin was close to 100% for xanthan, guar gum and pectin during production of noodles (Figure 1).

Figure. 1 The proportion of microencapsulated riboflavin recovered for different microencapsulation agents following incorporation into noodles made from mungbean and wheat flours

The noodles prepared here appeared to have a longer shelf-life. Normally, the “Hokkien” noodles have a shelf-life of 7-8 days. Here, the process and cooking methods used have extended the shelf-life to 18-21 days under refrigeration in sealed plastic bag.

Conclusions

The end product prepared using mungbean and wheat flour gave appealing qualities. The observation of shelving-life extension from normal 8 days to 21 days warrants further study. Typically, the incorporation of both mungbean and wheat flour as well as the addition of riboflavin gave the most appealing colour to the noodles and in terms of nutritional value, the noodles possessed good overall characteristics. In addition, the effective use of the capsules as a protectant while maintaining other quality attributes in noodles were achieved by appropriate formulation. Further nutritional aspects including supplementation of other nutrients requires additional studies. For now, the quality of noodles produced using the methods described here show considerable promise.

References

Aguilera, J.M. (1993) Pulses. In: Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson R.K. and Sadler M.J., Academic Press Limited, London, Pages 3841-3845.

Augustin, M. A., Sanguansri, L., Margetts, C. and Young, B. (2001) Food Australia 53:220-223.

Esteve, M-J., Farre, R., Frigola, A. and Garcia-Cantabella, J-M. (2001) Journal of Agricultural and Food Chemistry 49:1450-1454.

Trindade, M. A., Grosso, C. R. (2000) Journal of Microencapsulation 17: 169-176.

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