CHAPTER 4 FORMULA OPTIMIZATION OF INSTANT NOODLES. 4.1 Abstract

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1 CHAPTER 4 FORMULA OPTIMIZATION OF INSTANT NOODLES 4.1 Abstract The effect of major ingredients including water (30-35%), alkaline salt ( %), guar gum (0.-0.6%) and salt (1-%) on the quality of instant noodles has been studied. Response surface methodology (RSM) tool was used to assess factor interactions and models taking into account five response variables (i.e. oil uptake, cooked weight, cooking loss, hardness and overall acceptability) for instant fried noodles. Higher addition of water was found to be positively associated with oil uptake and cooked weight while negatively affected the cooking loss, textural attributes and overall acceptability of noodles. Guar gum up to a level of 0.3% was found efficient in improving the noodle quality. Alkaline salt were effective in improving firmness, cooking quality and overall acceptability of noodles besides reducing the oil uptake. The optimum level of the ingredients i.e. water, alkaline salt, guar gum and salt were observed to be 30.97, 0.3, 0.8 and 1.54% respectively while attempting to minimize the oil uptake and retain good noodle quality attributes. The results suggested that even varying the formulation can be effective in controlling the quality of instant noodles especially oil uptake during frying. 4. Introduction Instant noodles represent a fast growing product with expanding demands in Asian countries (WINA 011; Yu and Ngadi 004) due to their characteristics such as convenience, ease of production, widely acceptable taste, texture and affordable price. Noodle quality apart from flavourings and seasonings plays an important role in determining the acceptability of the product, and is generally assessed in terms of colour, appearance, cooking quality, textural attributes and sensory characteristics (Hou 001). Ingredients are one of the important determinants of final quality of instant noodles. The main ingredients for instant noodles are wheat flour, salt or kansui (alkaline salt mixture of sodium carbonate and potassium carbonate) and water (Kim 1996b). Other ingredients like starch, gums, emulsifiers, 56

2 stabilizers, antioxidants, colouring and flavouring agents are often added to improve the texture, eating quality and shelf life of instant noodles (Hou 001). The water absorption level generally used for noodle processing is about 30-38% based on flour weight. Water absorption level influences the amount of work required during sheeting as well as colour of the noodles. Insufficient water leads to the formation of noncohesive stiff dough thereby resulting in less extensible noodle sheet while too much water causes dough stickiness creating handling problems during noodle processing (Hatcher et al. 1999). Textural characteristics have been observed to be negatively associated with increasing water absorption in oriental noodles (Hatcher et al. 1999; Park and Baik 00; Edwards et al. 1996). The amount of salt added in noodles is usually 1 3% of flour weight. Salt has been found to have a strengthening or tightening effect on the gluten proteins and also improves and enhances the taste as well as flavour of noodles. The most commonly used alkaline salts in instant noodles are sodium and potassium carbonates. However, other alkaline reagents such as sodium hydroxide and bicarbonates may also be used. The type of alkaline salt used has also been associated with quality of noodles (Hatcher et al. 008c). Addition rate of alkaline salts in instant noodle is 0.1 to 0.3% as a quality improver. At an alkaline ph, dough characteristics are influenced including the behaviour of the gluten proteins thus, resulting in tougher, tighter, and less extensible dough (Ong et al. 010; Shiau and Yeh 001; Moss et al. 1986). Hydrocolloids have been viewed as multifunctional ingredients that provide flexibility, act as fat replacers and water binders, improve rehydration characteristics of noodles during cooking, modify texture and enhances the overall mouth-feel of finished product. While extensive research has been reported and focused on the effect of ingredients in relation to yellow alkaline noodles, dried noodles, and white salted noodles but there are relatively few studies that concerned instant noodles (Moss et al. 1987; Yu and Ngadi 004, 006). Recently, some researchers have focused on the studies related to instant noodle quality. Wu et al. (006) reported the effects of wheat flour composition, protein and starch quality characteristics on oil content of steamed-and-fried instant noodles. Some other researchers have also studied the textural and other quality properties of noodles (Park and Baik 004a; Park and Baik 00). The aim of this study has been to investigate the impact of varying the levels of major ingredients i.e. water, alkaline salt, guar gum and salt (NaCl) on the final attributes (oil uptake, texture, cooking quality and overall acceptability) of instant- 57

3 fried noodles. Response surface methodology was used to evaluate and determine the optimum level of these ingredients. 4.3 Flour Analysis The commercial flour analysis (Table 4.1) revealed that flour used for preparation of instant noodles was of intermediate gluten strength as indicated by the SDS sedimentation volume, protein content, gluten content, gluten index, C, dough development time and stability (Fig. 4.1). The falling number was also observed to be higher indicating that flour was obtained from sound grains free from sprout damage which has been further justified by a lower difference between the C3 and C4 values. Ash content of 0.58% shows that flour extraction rate was apt for noodle preparation with lower contamination of bran. Chemical as well as rheological parameters support that the flour was suitable for instant noodle preparation. Table 4.1 Characteristics of flour used Flour Characteristics Values ± S.D Moisture (%) 14.5 ± 0.10 Protein (%) 10.9 ± 0.0 Ash (%) 0.58 ± 0.0 Falling No. (sec.) ± 5.00 SDS Sedimentation volume (ml) 41.0 ± 0.50 Gluten content (% dry gluten) 9. ± 0.30 Gluten Index 79.8 ± 0.50 Water Absorption (%) 58.5 ± 0.10 Development time (min) 4.0 ± 0.10 Stability (min) 4.0 ± 0.10 Softening (FU) 76.0 ±.00 C1 (Nm) 1.11 ± 0.01 C (Nm) 0.49 ± 0.01 C3 (Nm) 1.79 ± 0.01 C4 (Nm) 1.75 ± 0.01 C5 (Nm) 3.0 ± Model Fitness The experimental design sheet and response values obtained have been shown in Table 4.. To evaluate the fitness of model, F-values were determined (Table 4.3). The F-values for models of oil uptake, cooked weight, cooking loss, hardness and overall acceptability (5.09, 33.9, 1.88, 1.17 and 3.09 respectively) were found to be highly significant (p<0.001). On the other hand, the lack of fit for all the models was found to be non-significant even at the 58

4 DP PCP P and Formula optimization of instant noodles 95% level suggesting that the selected models adequately represented the data for responses studied. Backward regression was used to eliminate the insignificant (p>0.1) model terms and derive the prediction equations for different responses studied (Table 4.4). Fig. 4.1 Mixolab profile of the wheat flour 4.5 Effect of Ingredients on Oil Uptake of Instant Noodles Frying of instant noodles results in removal of water from the strands imparting porous structure and unique flavour due to fat/oil. However, higher oil uptake during the frying process is undesirable due to potential health concerns and an increase in operating cost. A quadratic model (RP P= 0.96) was obtained for oil uptake with A, B, C, AB, AP P, BP P,P Pbeing the significant model terms. It was observed that water absorption, alkaline salt and guar gum are the main factors which significantly influence the oil uptake in instant noodles (Table 4.3). The variation in oil uptake with water absorption and alkaline salt is shown in Fig. 4.a. As evident from the response surface graph, the oil uptake decreased steeply with the incorporation of alkaline salt as well as water. However, it can be noted that increase in oil uptake was more pronounced at higher levels of water absorption than alkaline salt. 59

5 Similar observations for effect of water addition on oil uptake were reported by Yu & Ngadi (004). Table 4. Experimental design for varying formula ingredients and response values obtained S. No. A B C D OU CW CL HD OA A= Water absorption, B=Alkaline salt, C=Guar gum, D=Salt, OU= Oil Uptake (% o.d.b), CW= Cooked Weight (g/100g), CL= Cooking Loss (%), HD= Hardness (N) and OA= Overall Acceptability Score Lower water content in the formulation results in crumbly and less cohesive dough consequently forming noodles with rough surface which is responsible for higher oil uptake. Saguy et al. (1998) has also mentioned that surface roughness increases the oil uptake as it impairs oil drainage as well as increases overall surface area. A slightly higher water addition will favour the formation of gluten network and contribute to increased starch gelatinization 60

6 AP BP CP DP RP P P A= Formula optimization of instant noodles which may be responsible for the reduced oil uptake but much higher water content will result in increased moisture content in noodles which need to be removed by frying and eventually get replaced by oil. Table 4.3 Analysis of variance for different response models a SourceP Oil uptake Cooked Cooking Overall Hardness weight loss acceptability Model fitted Quadratic Linear Linear Quadratic Quadratic F- value Model 5.09*** 33.9*** 1.88*** 1.17*** 3.09*** A 1.35** 94.69*** 6.01*** *** 51.70*** B 16.91** 18.71*** 48.17*** 45.95*** 50.7*** C 9.45** 8.90** 5.69* 0.7 NS 17.66*** D 1.50 NS 5.66* 5.39* 1.4*** 0.7 NS AB 3.05*** ** 0.34 NS AC 1.4 NS NS 5.69* AD 0.00 NS NS. NS BC 3.64 NS * 1.88*** BD.11 NS NS 7.45* CD 0.53 NS NS 3.80 NS 69.91*** *** 66.88*** *** NS 3.61NS 61.97*** *** 6.0*** Lack of Fit Adjusted RP Predicted RP *** 1.83 NS NS NS 10.76** 4.05 NS 0.79 NS 1.65 NS *significant at p<0.05; **significant at p<0.01; ***significant at p<0.001; NS- not significant a Water absorption, B=Alkaline salt, C=Guar gum, D=Salt In contrast, alkaline salt increases the water absorption and increases the proportion of solid like behaviour of dough (Shiau and Yeh 001) contributing to lower oil uptake. Bouchon and Pyle (004) also reported that a stronger and more elastic network can result in a less permeable outer layer that may serve as an effective barrier against absorption of oil. It can be depicted from Fig. 4.b that incorporation of guar gum up to a level of 0.3% decreased the oil uptake, while higher levels enhanced the oil uptake and were not desirable. Guar gum has previously also been stated to reduce the oil uptake in instant noodles due to its ability to bind water (Yu and Ngadi 004). In addition, present results also indicated that higher guar gum incorporation at lower alkaline salt content corresponds to a noticeable increase in the oil uptake of noodles and thus not favourable. 61

7 (a) (b) Fig. 4. Effect of (a) alkaline salt and water absorption (b) guar gum and alkaline salt on oil uptake of instant noodles 4.6 Effect of Ingredients on Cooking Quality of Instant Noodles A linear model suggested for cooked weight of instant noodles was significant at p<0.001 (RP P= 0.847). All the linear terms for water absorption, alkaline salt, guar gum and salt were highly significant (Table 4.3). Water absorption and guar gum positively influenced cooked weight while alkaline salt and salt (NaCl) negatively affected the cooked weight of noodles (Table 4.4). Guar gum being a hydrocolloid favoured increase in cooked weight during cooking. Similar findings for guar gum and water addition were reported by Yu and Ngadi (004). Fig. 4.3a depicts a decrease in cooked weight with addition of alkaline salt, whereas a reverse trend was observed with increase in water absorption in the formulation of instant noodles. Linear model for cooking loss was significant at p<0.001 (RP P= 0.785) with water absorption and alkaline salt as significant linear terms at p<0.001, while linear terms for guar gum and salt were significant at p<0.05 (Table 4.3). Cooking loss reflects the surface characteristics of cooked noodles. Higher cooking loss is associated with poor noodle surface which hampers the appearance as well acceptability of noodles. Salt slightly reduced the cooking loss while guar gum increased the same (Fig. 4.3b). Guar gum competes with the 6

8 P P A= RP Formula optimization of instant noodles protein for water due to its hydrophilic property, thus, weakening the protein network and also reduces the starch paste viscosity on gelatinization thereby leading to higher cooking loss. Table 4.4 Predicted equation for different responses Predicted equation for the responses in terms of coded factors P a Oil Uptake = A 0.46 B C 0.14 D AB 0.37 BC A B C D Cooked Weight = A 3.78 B +.61 C.08 D Cooking Loss = A 1.11 B C 0.37 D Hardness = A B 0.44 C +.10 D +.96 AB 1.74 BC A C D Overall Acceptability = A B 3. C D 3.50 AC BC 3.50 BD +.50 CD 9.7 A.00 B C a Water absorption, B=Alkaline salt, C=Guar gum, D=Salt (a) (b) Fig. 4.3 Response surface plot for the effect of (a) water absorption and alkaline salt on cooked weight (b) salt and guar gum on the cooking loss of cooked instant noodles It was also observed that cooked noodles with higher added water and guar gum had a higher cooked weight due to more rehydration during cooking, poor cooked noodle surface as well as higher cooking loss. Whereas, incorporation of salt and alkaline salt made the dough stronger/firmer and elastic, thus, contributing to the reduction in cooked weight and cooking loss. Choy et al. (010) have also reported that a stronger and tighter protein network between 63

9 starch granules limits the excessive water uptake during cooking thereby decreasing the cooked weight and cooking loss. 4.7 Effect of Ingredients on Texture of Instant Noodles Texture of instant noodles is a very important characteristic and ingredients used play important role in defining the textural properties. In general, consumers prefer the texture of instant noodles to be firm with a good chewy bite (Kubomura 1998; Kim 1996b). The data in Table 4.3 indicates that water absorption, alkaline salt and salt significantly affected (p<0.01) the hardness of cooked instant noodles in linear terms. (a) (b) 4.4 Effect of (a) alkaline salt and water absorption (b) guar gum and alkaline salt on the hardness of cooked instant noodles Alkaline salt in interaction with guar gum decreased hardness but increased it with water absorption significantly. Fig. 4.4a shows the effect of water absorption and alkaline salt on cooked noodle hardness which increased considerably with increase in alkaline salt, while decreased with increase in water addition. Furthermore, the noodles were observed to become softer and thus unacceptable at higher water absorption level of 35% and lower alkaline salt. However, by adding alkaline salt, the hardness improved, even at higher water absorption level. Hatcher et al. (1999) also reported a significant decline in textural properties of oriental noodles at higher water content. Interaction of alkaline salt and flour results in toughening of 64

10 dough and confers gum like texture to it (Terada et al. 1981) which is responsible for an increase in hardness of cooked instant noodles. Alkaline salt were also reported to increase the breaking and cutting force of noodles (Sung and Sung 1993). Effect of alkaline salt and guar gum on hardness of noodles has been shown in Fig. 4.4b. It was noticed that alkaline salt increased the cooked noodle hardness. Addition of guar gum decreased the cooked noodle hardness upto 0.4% incorporation level, whereas increased it when incorporated above 0.4%. Shiau and Yeh (001) observed that alkaline salt induces the interchange of sulphydryl group and disulphide bond, which increases the G (storage modulus), apparent viscosity of dough as well as tensile and cutting force in extruded noodles. 4.8 Effect of Ingredients on Overall Acceptability of Instant Noodles ANOVA analysis indicates that overall acceptability of instant noodles was significantly affected by the linear (p<0.01) and quadratic (p<0.01) effect of the water absorption and guar gum respectively (Table 4.3). Alkaline salt affected the overall acceptability of noodles in linear term and also in interaction with guar gum and salt. Fig. 4.5a shows that overall acceptability of noodles was higher at 31.0 to 33. % water addition and lower guar gum i.e. 0.3% with higher levels of both deteriorating the noodle quality to a significant level. (a) (b) Fig. 4.5 Effect of (a) guar gum and water absorption (b) salt and alkaline salt on overall acceptability score of instant noodles 65

11 This is as might have been expected because guar gum provides viscosity, improve firmness, mouthfeel and rehydration characteristics of the product (Hou 001) but higher levels may result in protein network weakening as explained earlier. Fig. 4.5b on the other hand affirmed that overall acceptability increased with the incorporation of alkaline salt and salt. The alkaline conditions provided to dough by the alkaline salts confers unique flavour and yellow colour; modifies pasting and dough properties; and improves the cooking, textural and surface properties of the noodles. Therefore, alkaline salts improve the appearance, eating quality as well as overall acceptability of the instant noodles. Table 4.4 indicates that water absorption has a negative impact on the overall acceptability of noodles while alkaline salt and guar gum have a positive effect. This may be attributed to the fact that higher water absorption as mentioned above not only hampers the textural properties but also has a significant effect on colour (Hatcher et al. 1999). 4.9 Optimization of Formula Ingredients To obtain the optimal level of formula ingredients, numerical optimization was carried out. The selection criteria for responses oil uptake and cooking loss was set to minimum because higher values of oil uptake is not desirable as it increases the production cost and health concerns. Higher cooking loss is associated with poor surface characteristics of noodles and therefore reduces the acceptability of product. Overall acceptability was set to maximum. Hardness and cooked weight of noodles was set towards higher range but not maximum as noodles with maximum hardness or extra firm texture are not preferred by the consumers. After applying these constraints, it was found that optimal levels for water addition, alkaline salt, guar gum and salt were 30.97, 0.3, 0.8 and 1.54%, respectively. The adequacy of the model for predicting optimum response value was verified by carrying out the analysis of noodle prepared using the optimum levels of the ingredients. Table 4.5 Predicted and actual response values at optimum level of ingredients Response Predicted Value Actual Value Oil Uptake (%) ± 1.06 Cooked Weight (%) ±.87 Cooking Loss (%) ± 0.97 Hardness (N) ± 1.41 Overall Acceptability ± 1.3 The results obtained showed that the experimental values were close to the predicted values, thus, validating the optimal levels of ingredients studied (Table 4.5). 66

12 4.10 Conclusion It may be concluded from the present study that ingredients have an important role to play in governing the quality of instant noodles. It was observed that although higher water inclusion in the instant noodle formulation improved cooked weight it negatively affected the texture, oil uptake, cooking loss, hardness as well as overall acceptability of the product. Alkaline salt, however, reduced cooking loss and cooked weight; it had a positive effect on the overall quality of instant noodles. Guar gum up to a maximum of 0.3% was found to be effective in reduction of oil uptake and improving the quality of noodles. The optimum level of the ingredients i.e. water absorption, alkaline salt, guar gum and salt were observed to be 30.97, 0.3, 0.8 and 1.54%, respectively at minimum level of oil uptake and acceptable quality of instant noodles. 67