The Effect of Selected Additives on the Oil Uptake and Quality Parameters of Fried Instant Noodles

Featured Application: Authors are encouraged to provide a concise description of the speciﬁc application or a potential application of the work. This section is not mandatory. Abstract: The scope of the paper includes the analysis of various quality parameters of fried instant noodles depending on the type and amount of the additive added to the basic recipe. For the analyzed instant noodles, the effect of hydroxypropylmethylcellulose (HPMC), microcrystalline cellulose (MCG), maltodextrin, and psyllium on the quality parameters (oil uptake, moisture, water activity, color, and acoustics) were determined. Results show that the quality parameters of instant noodles signiﬁcantly depend on the type and amount of additives. The addition of HPMC and MCG resulted in decrease absorption, while the use of maltodextrin and psyllium increased the fat absorbed during frying. There is a signiﬁcant relationship between the type of additive and the color of instant noodles. Color brightening was observed for instant noodles with the HPMC and MCG, while the addition of maltodextrin and psyllium contributed in the darkening of instant noodles (reduction of the L* parameter). The type of additives signiﬁcantly inﬂuenced the texture of the instant noodles. The samples with a 3% addition of maltodextrin had a softer texture than the control sample, while the instant noodles with the HPMC, MCG, and Psyllium were characterized by a harder texture. For instant noodles with the addition of HPMC, MCG, and Psyllium larger number of acoustic events and higher breaking force were observed than for the control one. The frying temperature signiﬁcantly inﬂuenced the texture of analyzed instant noodles (acoustic and mechanical properties). Increasing frying temperature from 160–170 ◦ C caused a signiﬁcant increase in acoustic descriptors and force.


Introduction
Instant noodles are one of the main cereal products next to the bread and the groats. Due to the tendency to spend less time preparing meals, the modern consumer tends to buy convenience food products. The instant noodles belong to the most popular examples of the convenience food, being a component of many prepared dishes. According to the World Instant Noodles Association (WINA), in 2017, the demand for instant noodles in China and Hong Kong alone was more than 38

Preparation of Instant Fried Noodles
The instant noodle dough was formulated by 100% flour, 3% (kg/kg flour) salt, 3-5% (kg/kg flour) maltodextrin, 0.8-1% (kg/kg flour) MCG, 0.4-0.5% (kg/kg flour) HPMC, 3-5% (kg/kg flour) psyllium, and 33% (kg/kg flour) water. First, flour was mixed with appropriate additives, such as maltodextrin, MCG, HPMC, and psyllium, and after that, the water solution of dissolved salt was added. Finally, the dough has been formed by mixing all the ingredients. The crumbly dough was then placed into a resealable plastic bag and rested for 30 min before further size reduction.
The dough was then passed through the roller unit attachment of a pasta machine (Kitchen Aid, Benton Harbor, MI, USA) with the regulating knob set at the No. 1 position (2.5 mm). The resulting sheet was folded in half and passed again through the rollers. This process was repeated several times until the dough sheet was smoothly formed. The thickness of the sheet was reduced stepwise by passing between the rollers of the pasta machine. The final cutting roll gap was adjusted to 1.0 mm and the noodle sheet was cut through a cutter attachment. The noodles were then steamed in a steamer for 5 min. The final step was frying in canola oil (ZT Kruszwica S.A., Kruszwica, Poland) at temperatures of 160, 170, and 180 • C for 90 s. After the frying process, noodle strands were cooled at a room temperature (~23 • C) and packed into polyethylene bags.

Moisture Analysis
Moisture contents were measured by slightly modifying the air oven method [29], and each sample measurement was carried out in triplicate. These samples were dried at 100 ± 1 • C. The process of drying, cooling, and weighting was repeated until constant weight obtained.

Fat Analysis
The fat content of instant noodles was determined by automated Soxhlet extraction (Soxtec™ 2050 Auto Fat Extraction System). Three repetitions were made for each measurement and the average data collected was used for statistical analysis. The dried samples were accurately re-weighted.

Color Determination (L/, a/, b/ Parameters)
The color of instant noodles was measured using the L*, a*, b* system as described by Papadakis, Abdul-Malek, Kamdem, and Yam [30]. L/ refers to the luminosity or lightness component, a/ (intensity of red (+) and green (-)) and b/(intensity of yellow (+) and blue (-)) are the chromaticity coordinates. All sampled instant noodles were analyzed in terms of the referred parameters using a Minolta CR-310 colorimeter (Konica-Minolta, Osaka, Japan) that was previously calibrated with a white standard tile. Three repetitions were made for each measurement.

Water Activity Analysis
Water activity was measured in 3 repetitions with the precision of ±0.001 using a Hygroscope DT2 (Rotronic AG, Bassersdorf, Switzerland)

Density Analysis
The apparent density was measured in 3 repetitions using helium pycnometer from a stereopycnometer (Quantochrome Instruments, Boynton Beach, FL, USA).

Mechanical Properties Analysis
Compression tests were carried out using a TA-HD plus texture analyzer (Stable Micro Systems, Godalming, UK) equipped with a 5-kg load cell and HDP/MK0-type probe. Samples of instant noodle Appl. Sci. 2019, 9, 936 4 of 14 with weight 4.5 ± 0.1 g and dimensions of 16 mm were deformed at a constant speed of 1.0 mm·s −1 and up to a compression strain of 60%. Fifteen samples were subjected to the compression test at 25 • C. The force versus deformation data were registered, and selected parameters were determined using Exponent software (Stable Micro Systems, Godalming, UK): compression force (N); force at a strain of 60% and area under force-deformation curve until the strain 40% as compression work (mJ).

Acoustic Emission (AE) Analysis
The acoustic emission (AE) was detected by a contact method using the 4381 sensor (Brüel& Kjaer, Denmark) when sampling the instant noodle in the compression test in the Texture Analyzer TA.HDPlus (Stable Micro Systems, Godalming, UK) was deformed. The sensor was connected with a 2 m cable to the AE signal amplifier. The acoustic emission signal was amplified by 40 dB in the low-noise amplifier and digitalized using an Adlink Technology Inc. type 9112 (Adlink Technology Inc., Taipei, Taiwan) analog-digital conversion sound card with the sampling frequency of 44.1 kHz [31]. The recorded acoustic signal generated during compression was analyzed in the frequency range of 0.1-18 kHz. The acoustic descriptors-sound amplitude, the energy of one acoustic event, and the number of acoustic events-were all determined using a computer program, the Calculate_44kHz_auto program (Warsaw, Poland). These analyses were conducted in 15 repetitions.

Statistical Analysis
The analysis of variance (ANOVA) was conducted using Statistica 12 PL and the significant differences between mean values were determined using Tukey's Multiple Range test at a significance level of p < 0.05. In the case of abnormal distribution, division into homogeneous groups was performed using the non-parametric multiple comparison test (a Kruskal-Wallis test). Principal component analysis (PCA) was performed to reduce the number of variables (from 7 to 2) and for easy comparison of the analyzed instant noodles. This analysis allows the possibility to observe similarities and differences between the studied instant noodles [32].

Moisture
Moisture is an important parameter affecting food quality and storage stability [33]. According to Hou [26], fried instant noodles are characterized by changes in moisture during the frying process from an initial moisture level of 30-40% to a final moisture level of 2-5%.
The analysis of the obtained results showed that the level of moisture was in the range of 2.57-3.79% (Table 1), which is consistent with that reported by Kim et al. [34], 3-4%. The highest moisture content was determined in instant noodles with the addition of HPMC and MCG, being in the range from 3.29-3.85%. The lowest moisture (2.57%) was observed in instant noodles with 5% addition of psyllium fried in temperature 180 • C.

Oil Uptake
The fat content is an important feature of the quality of fried instant noodles, a result of the production process parameters (the temperature and the frying time), the quality of raw materials, and the frying medium used during the instant noodles production process [3,26,34]. The frying medium used in the instant noodles production process is not only a heat carrier, but also becomes its new ingredient (migration into the internal structure of the instant noodles) [6,35].
Instant noodles obtained during experiments contained from 20.5-30.51% fat. The fat content depended on the type of the additives and increased together with an increase of the amount of the additive and an increase of frying temperature (for HPMC and MCG, the changes in the amount of appropriate additives has not decreased the fat content along with increasing the frying temperature.
The lowest values of fat content were observed with the addition of HPMC and MCG, while the Appl. Sci. 2019, 9, 936 5 of 14 highest fat content was observed with the psyllium additive. Similar relations were observed by Rekas and Marciniak-Lukasiak [20] using sunflower oil as a frying medium. Differences in the fat content in the process of frying instant noodles come from the microporous structure of the instant noodles and from the amount of water absorbed in the evaporation process [6]. In the frying process, the water molecules contained in the food moves from the center of the product to its surface. As a result of the evaporation of water from the instant noodles threads, a porous structure is formed [36]. Evaporating water creates empty spaces in the microporous structure of the instant noodles being filled by fat during frying [6].

Color
Color is an important factor in food quality-it affects the food acceptance level of the consumer. Combined with texture, the color affects the appearance of instant noodles. Color depends mainly on the quality of the flour, the amount and the type of hydrocolloids [37], the frying process parameters [25,38], and the content of protein (affects the formation of the characteristic yellow color of instant noodles) [39]. According to Hatcher [35], instant noodles should be characterized by an appropriate level of brightness, a lack of discoloration, and a typical light yellow color.
According to Park and Baik [40], L* is a critical parameter in the frying industry and is usually treated as the first quality attribute evaluated by consumers during the determination of the acceptance level of a product. Low L* values indicate dark color and are mainly associated with non-enzymatic browning reactions [41]. Instant noodles made from durum wheat flour are generally characterized by higher brightness (L* > 76.4), while instant noodles produced from wheat flour are characterized by lower brightness (L* < 76,4). According to Chon-Sik Kang et al. [42], the brightness of instant noodles should be in the range of 73.5-82.0.
Based on the obtained results, it was found that the brightness of the instant noodles was within the range suggested above. The highest level of the L* parameter was observed for instant noodles with the addition of HPMC, (associated with a light color). In contrast, the use of the maltodextrin and psyllium resulted in the darker color of instant noodles. Along with the increasing amount of the particular additive and the increasing frying temperature, the L* parameter was found to be decreasing (the darker color of the instant noodles). Similar trends were observed by Rekas and Marciniak-Lukasiak [20].
Discriminants of the color of instant noodles without and with the addition of maltodextrin, MCG, HPMC, and psyllium were fried in rapeseed oil at 160, 170 and 180 • C for 90 seconds. During the analysis of the a* parameter (corresponding to the red (+a*) and the green color (−a *)), it was found that the majority of tested instant noodles were characterized by red saturation. Increasing the percentage of MCG and HPMC in the original recipe resulted in decreasing the red color saturation, while increasing the amount of psyllium and maltodextrin in the recipe increased the red saturation of the color of the instant noodles (Table 2). In the b* parameter (corresponding to the yellow (+b *) and the blue (−b *) color), it was observed that regardless of the amount of the additive, instant noodles were characterized by yellow color saturation. With the increase of the HPMC, maltodextrin and psyllium percentage in the recipe, the values of the b* parameter increased (Table 2).
3.3. Water Activity, Density, Mechanical Properties, and Acoustic Emission Table 3 shows the water activity, density, and texture parameters (acoustic and mechanical) of instant noodles. The water activity of the tested instant noodles did not differ statistically (p = 0.441), regardless of the type of additives used. However, the density of the samples depended on the type of the additive (p = 0.030). The addition of Psyllium in the amount of 3% caused a decrease of the density value in comparison with the control sample, but the addition of Psyllium in the amount of 5% had no influence on the density. The smallest density was found in instant noodles with the addition of Psyllium in the amount of 3%, while the largest was observed in instant noodles with Maltodextrin 5%. In the sample with the addition of Psyllium in the amount of 3%, a high content of fat and a low level of moisture was observed which caused the low density value of the instant noodle. However, the addition of Maltodextrin in the amount of 5% caused the instant noodle to have a similar fat and moisture content as samples with addition of Psyllium in the amount of 3%, but the density was significantly higher.
Both ingredients: Psyllium and maltodextrin were added to the dough bind water [43], which evaporates during frying. Differences in the density of the tested instant noodle samples may result from the strength of water binding and the possibility of its release during frying. In addition, it can be assumed that Psyllium has greater gas retention ability during frying than Maltodextrin. Samples with a higher concentration of MCG (0.8%) HPMC (0.5%) in comparison with instant noodles with maltodextrin, had a density value on the similar level, higher moisture content and the lower fat content. One can conclude that higher concentrations of MCG and HPMC result in less moisture loss and reduces the absorption of fat during instant noodles' frying.
Cellulose derivatives such as CMC, HPMC, and hydroxypropyl cellulose (HPC) and amylose have been evaluated as oil barriers in a deep-fat fried African cowpea paste-based food, comparing the coatings obtained by spraying and dipping the cowpea balls [22]. This oil barrier effect was related to the thermal gelation capacity of HPMC. Above the incipient gelation temperature, the viscosity increases dramatically as intermolecular associations occur very rapidly, and the solutions gel at the point which for HPMC is found lies in a temperature range of 50-90 • C. The gel layer controls the migration of water and oil during frying.
Acoustic emission (AE) is a phenomenon of generation and propagation of elastic waves in various materials. The basis for the creation of such waves are microcracks, mutual shifts, or friction of surfaces of materials. In order to characterize the observed AE signal, acoustic descriptors are determined [31]. AE descriptors strongly depend on the composition of the product, the type of structure, and mechanical properties such as hardness or tendency of the material to experience plastic deformation [44]. Pasta textural parameters are recognized as one of the most important features for consumers and are one of the critical aspects for quality assessment.
Statistical analysis showed that the type of additives significantly affected the acoustic parameters: The number of AE events (p < 0.001), the amplitude of the sound (p < 0.001), and the energy of a single AE event (p < 0.001) ( Table 3). The lowest number of AE events was generated by the control sample, while the largest number was observed in the sample with the addition of Psyllium 5% (Table 3). Instant noodles with Maltodextrin, MCG, and HPMC generated a significantly higher number of AE events than the control sample, but smaller than instant noodles with Psyllium. Higher density, as well as the lower fat content of samples with maltodextrin, MCG, and HPMC addition, influenced the generated number of AE events. The density of the instant noodle is related to the porosity, i.e., the lower the density value, the greater the porosity value. This could have affected a large number of AE events generated by the samples with Psyllium addition. During amplitude analysis, an inverse relationship was found. The control sample during the compression phase generated the sound with the highest amplitude, while the samples with Psyllium contents of 3% and 5% generated the sound with the lowest amplitude. Samples with Psylium contents of 3% and 5% generated sounds with the highest energy (Table 3). It was observed that the increase in the additional amounts of maltodextrin, MCG, HPMC, and Psyllium caused a significant increase in the number of AE events, but the amplitude and energy of a single EA event were similar to the other samples ( Table 3). The reason for such results may be due to the high fat content in the samples with Psyllium additions. Moreover, the addition of carboxymethyl cellulose improved the gluten structure and formed a matrix with the gluten proteins where starch granules became embedded and decreased the solid loss in cooking [45].
The high number of AE events registered in the case of the tested instant noodles acted not only due to the breaking of the instant noodles' ribbons, but also due to their mutual friction during the compression test. The smallest sound amplitude was recorded for the hardest samples of instant noodles (with Psyllium). The amplitude depends on the structure of the material-the more anisotropic the structure, the higher the amplitude of the sound [46]. Acoustic emission is strongly dependent on the formulation of the product. A small sound amplitude indicates a low crispness of the instant noodle, which may be related to an increase of the moisture in the instant noodle [47], an increase in fat content together with structural changes [44], or a high inulin content [48].
Mechanical parameters such as the force (p < 0.001) and the work (p < 0.001) significantly depend on the type of additive ( Table 3). The hardness is a measure of the compression force of the noodles. Work is the energy needed to compress samples to 40% of the original height. The control and HPMC samples were characterized by the lowest hardness value, while the samples with Psyllium 3 and 5% were characterized by the highest hardness value. The hardness, like acoustic emission, strongly depends on the density of the material and its chemical composition [31,44,49]. Therefore, the samples from Psyllium were the hardest because they had high densities and the lowest water contents. Both the hardness and the compression work were characterized by high variability, as evidenced by the value of the standard deviation. This is due to the uniformity of the samples.

Temperature
The frying temperature did not significantly affect water activity (p = 0.269) of the instant noodles. The instant noodles densities varied considerably due to the frying temperature (p = 0.023). One has observed a significant dependency between the type of additive and the frying temperature (p = 0.005). Increasing the frying temperature from 160-170 • C caused an increase in the density of the material with Maltodextrin addition in the amount of 3.00%, MCG in the amount of 1.00%, and HPMC in the amount of 0.40% (Table 3). The amount and access to water are limited in pasta. Therefore, when frying begins, there is a competition between starch, proteins, and added hydrocolloids with water molecules. Morris [1990] reported that the interaction of protein and hydrocolloid fills the cracks of the combination of the soy protein-gluten interaction and makes a protein matrix which has higher moisture holding capacity [50].
The instant noodles' properties such as the number of AE events (p = 0.023) and the energy of one AE event were significantly influenced by the frying temperature (p < 0.001). There was no effect of frying temperature only on the amplitude of the sound (p = 0.621). Also, the mechanical parameters such as force (p < 0.001) and work (p < 0.001) depended on the instant noodles' frying temperature.
The principal component analysis (PCA) with the classification allowed for the interpretation of the results of the instant noodles' texture evaluation. Simultaneous presentation of the projection of the evaluated parameters and the tested samples of instant noodles allowed us to determine features differentiated in the samples (Figure 1). 15.8%. In total, the first two main components contained 77.2% of the total information. Amplitude, single-event energy of AE, force, work, and fat content formed the first component (PC1), while the second component (PC2) was formed by the number of AE events and the density (Figure 1). The close position of force, work, the number of AE events, and fat content indicated a positive correlation of these features (Figure 1, Table 4). Strong positive correlations also occurred between the amplitude of sound and the density of the instant noodles ( Table 4).

Conclusions
HPMC and MCG decrease the fat absorptions in instant noodles, while the use of maltodextrin and psyllium increased the fat absorbed during frying. There is a significant relationship between The first two components (PC1 and PC2) were selected for analysis using the Kaiser criterion [30]. The first one (PC1) explained 61.4% of the total variance, while the second (PC2) accounted for 15.8%. In total, the first two main components contained 77.2% of the total information. Amplitude, single-event energy of AE, force, work, and fat content formed the first component (PC1), while the second component (PC2) was formed by the number of AE events and the density (Figure 1). The close position of force, work, the number of AE events, and fat content indicated a positive correlation of these features (Figure 1, Table 4). Strong positive correlations also occurred between the amplitude of sound and the density of the instant noodles (Table 4).

Conclusions
HPMC and MCG decrease the fat absorptions in instant noodles, while the use of maltodextrin and psyllium increased the fat absorbed during frying. There is a significant relationship between the type of additive and the color of instant noodles. Color brightening was observed for instant noodles with the HPMC and MCG, while the addition of maltodextrin and psyllium contributed in the darkening of instant noodles (reduction of the L* parameter).