Effect of Semolina Replacement with Amaranth Flour on Quality Characteristics of Functional Pasta

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Introduction
Functional foods have nutritional value and benefcial efects on human health and reduce the risk of various diseases [1].Tey include probiotics, prebiotics, polyunsaturated fatty acids, omega-3, conjugated linoleic acid, antioxidants, vitamins, minerals, some proteins, peptides, and amino acids [1].
Today, the consumer demand for cereal-based functional foods, i.e., pasta is increasing.Pasta is made from semolina or durum wheat and is known as a cheap food due to its simple formulation and production process [2].Semolina is the starting material for pasta manufacture and is high in protein and fber, both of which slow digestion.It contains various vitamins such as B complex and minerals such as iron [3].Considering that most cereal products are made from wheat four and wheat protein is defcient in some amino acids such as lysine, so in recent years, many studies related to the enrichment of these products have been undertaken [2].
Moreover, gluten enteropathy or celiac is caused by an inappropriate immune response to wheat gluten.Patients are unable to consume some of the most common products including breads, baked goods, and other food products made from wheat four.Te gluten-free diet is highly effective in alleviating the symptoms of the disease, i.e., small bowel villous atrophy and crypt hyperplasia.In recent years, there has been an increase in consumer interest in glutenfree foods, and researchers have been working more on the development of gluten-free products, prepared with nonwheat fours such as rice, maize, soya, guar, and amaranth [4].
Amaranth belongs to pseudocereals and does not contain gluten and with a high glycemic index, and it is suitable for celiac disease.It is a good source of carbohydrates (73-77%), protein (15.5−12.5%),lipids (7-8.1%),dietary fber (19.5-49.3),and minerals (3.5−3%).Te bran fraction is proportionally higher in amaranth seeds than in common grains such as corn and wheat, which explains the higher levels of protein and fat content in these seeds.Starch (62-65%) is the most abundant carbohydrate in amaranth.Moreover, unlike cereal grains, there is a high content of lysine in the amino acid profle of amaranth.Amaranth starch generally produces more stable pastes than cereals and legumes, due to its small size and low amylose content.Amaranth contains various minerals such as calcium (134-370 mg/100 g), magnesium (230-387 mg/100 g), phosphorus, iron, potassium, and zinc and E and B vitamins, ribofavin, ascorbic acid, polyphenols, and favonoids.Cafeic, p-hydroxybenzoic, and ferulic acids are the main phenolic compounds in amaranth.Its oxalate content is between 178 and 278 mg/100 g.Although oxalates are a potential risk factor for kidney stone formation and reduce the availability of calcium and magnesium, most of the oxalates in amaranth seeds are in insoluble form, and their absorption may be low.Amaranth contains higher lipids than most cereals, and its oil composition is quite similar to other cereals with high unsaturated fatty acids (approximately 77%) such as linoleic acid.Amaranth oil mainly contains tocotrienols, which are associated with cholesterollowering activity, and squalene, which exhibits anticancer and hypocholesterolemic efects [5].
Some studies evaluated the enrichment of cereal products with amaranth, such as bread [6][7][8][9][10][11][12], cake [13], and pasta [3,14].So far, very few studies have reported on the technological evaluation of pasta [3,14].Te purpose of this research was to investigate the possibility of amaranth four as a food supplement to replace semolina in pasta making and improve the quality properties of pasta with enriched protein content and determine the highest proportion of the amaranth four that provides the required functionality to produce acceptable pasta.

Pasta Production.
Pasta was prepared in a pasta machine (Zar Macaron, Iran) with amaranth four to semolina ratios of 0 : 100, 10 : 90, 15 : 85, and 20 : 80. Semolina pasta was also prepared as a control.All batches (280 g each, 14 g of water/ 100 g) were mixed at room temperature with 1.5 g of distilled monoglycerides/100 g and 10 g of egg white powder/100 g in a mixer (Moulinex, France) at a low speed for 2 min, and 50 g of warm distilled water/100 g was slowly added and mixed for 10-15 min.Afterward, the dough was allowed to rest for 35 min in a proofng chamber at 30 °C and 95% RH.First, the proofed dough was laminated in the pasta machine at setting 1 and fnally at setting 3. Te pasta was hand-cut into strips of approximately 25 cm long (fresh pasta) using a scissor and dried at 75 °C and 91% RH for 3 h (dried pasta) in an oven (Behdad, Iran).Te four pasta samples were allowed to cool, placed in individual sealed containers to avoid moisture exchange, and stored at room temperature for 3 months [3].

Physical Characteristics of Pasta.
Te cooking loss was measured after 10, 20, and 30 min according to the Iranian National Standard No. 213 (2010).Te hardness of the pasta was analyzed by using a texture analyzer (Brookfeld, USA).Te color was checked using HunterLab (FMS Jansen GmbH and Co.KG, USA), and L, a * , and b * values were determined [3].

Amylose Leach Out in the Cooking
Water.Pasta (6 g) was cooked in 120 ml of water until optimum cooking time.Cooked water was drained thoroughly into a 100 ml volumetric fask and made up to 100 ml.After mixing, this was fltered using suction. 1 ml of the fltrate was mixed with 1 ml of iodine solution and made up to 25 ml.Te color 2 Journal of Food Quality developed was read at 650 nm.Te amylose content was estimated by linear regression analysis [4].

Microstructure Analysis.
Te morphology of the pasta after coating with gold and immersion in liquid nitrogen was analyzed using the scanning electron microscope (SEM, LEO 435VP, UK) at a voltage of 5-15 kV.
2.8.Sensory Characteristics of Pasta.Te samples were coded before the test, and sensory characteristics of cooked pasta such as favor, odor, color, texture, and overall acceptability were evaluated by 12 trained panelists from the Food Science and Technology Department, using the 5-point hedonic method.Samples were evaluated after cooking and served in porcelain cups coded with random numbers.Panelists were asked to rinse the mouth with water between each sample.Tree samples were assessed per session according to a completely randomized design [4].

Statistical Analysis.
All experiments were conducted in a completely randomized design and with three replications.Te results were expressed as the mean ± standard deviation (SD).Analysis of variance (ANOVA) was performed by SPSS software (ver.21) at a signifcance level of 0.05 (p < 0.05) [13].

Results and Discussion
3.1.Chemical Characteristics of Flour.Amaranth four has a signifcantly higher moisture content, fat, protein, and fber than the semolina four (p < 0.05) (Table 1).Te chemical composition of amaranth four was consistent with other researchers [9,13,16].

Dough's Rheological
Properties.Farinograph and extensograph results are summarized in Tables 2 and 3.
Amaranth increased water absorption, dough consistency, and development time.Te water absorption increase is probably related to the hydrophilic compounds (fbers) that reacted with water.Amaranth reduced the dough's stability.Te highest and the lowest DS were related to the control and A 20 samples, respectively, because of the dilution efect of amaranth on the gluten network formation [17].On the other hand, amaranth contains polysaccharides (insoluble fber) with a weakening efect on gluten [7].
Te degree of softening (DOS) increased with the increase in the concentration of amaranth, which is due to the dilution of the gluten network and the reaction between fber and gluten, which causes the softening of dough [17].
Te farinograph quality number (FQN) is a standard that describes the overall quality of the four.Weak fours show low FQN, and strong fours show high FQN.As can be seen from Table 2, the control treatment showed the highest FQN and the increase in the amaranth concentration decreased FQN.
With the increase of the amaranth substitution, the elastic behavior (R m : maximum resistance) is strengthened and the viscous behavior (E: extensibility) is weakened.During the dough rest, these components are recovered and form a uniform gluten network due to glutenin changes.Terefore, R m and E improve.Te elastic properties are related to the presence of glutenins, and the viscous properties are related to gliadins.Te dilution of gluten changes the ratio of gliadin to glutenin [18].Amaranth treatments had lower R m and E and higher R 50 than the control sample.Tis is probably related to the coarser size of the amaranth particles compared to wheat particles, which causes the rupture of gluten during stretching [11].
Considering the diferent efects of amaranth on R 50 (resistance), R m (maximum resistance), and E (extensibility), the evaluation of energy required for dough stretching (A: energy) can be a better explanation for the rheological behavior.A larger value indicates high dough strength.Amaranth decreased A in comparison with the control sample.

Chemical Characteristics of Pasta.
Te moisture content of pasta samples decreased during 3 months of storage (Figure 1(a)).Te lowest and the highest moisture contents were observed in the control and A 20 samples, respectively, with a signifcant diference (p < 0.05).Te ANOVA results showed that amaranth had a signifcant efect on the contents of fat, protein, and fber (p < 0.05).Te semolina pasta (control) showed the lowest amount of fat, protein, and fber, and the highest amounts of these parameters belong to the A 20 sample (Figures 1(b Te presence of hygroscopic compounds such as soluble and insoluble fbers, cellulose, hemicellulose, and lignin in amaranth preserves the moisture content after cooking and increases water absorption [7].Te results of moisture content confrmed the results of water absorption in farinograph tests. Te higher fat and protein content of pasta samples containing amaranth can be attributed to the diference between fat and protein contents of amaranth and semolina (Table 1).
Sanz-Penella et al. [7] showed that replacing wheat four with amaranth increases the amounts of protein, fat, ash, dietary fber, and minerals.According to the fndings of Hamzehpour and Dastgerdi [13], the addition of amaranth four signifcantly increases the fber and protein content of the cake.
According to the national standard of Iran (no.213; 2010), the permissible limit of moisture content, protein, and fber is maximum 12%, 10%, and 2-3%, respectively, in regard to moisture, all pasta samples were within the standard range, and in regard to protein and fber, A 20 treatment was in the standard range [19].Journal of Food Quality Te microbial growth, chemical reactions, and enzyme activities that can afect the stability of products are infuenced by the moisture content and water activity.Te lower the water activity, the more the stability increases.A lower moisture content is essential for safe storage.However, a very low moisture content leads to dry and brittle pasta [3].

Cooking Loss.
Te results of ANOVA revealed that amaranth had a signifcant efect on the cooking loss of diferent pasta types during 30 min (p < 0.05).Te lowest and highest cooking loss was observed in the control (semolina pasta) and A 20 samples, respectively (Figure 2).As the time increased from 10 to 30 min, the cooking loss increased (p < 0.05).
Te amounts of cooking loss (4.14-5.37%) in all samples are in accordance with the national standard of Iran (no.213; 2010), in which the cooking loss has been determined at a maximum of 11% [19].
3.5.Texture.Amaranth reduced the hardness of pasta.Te lowest hardness was observed in the A 20 sample, and the highest hardness belonged to the semolina pasta (Figure 3).Regarding the reduction of hardness of some samples, it can be said that the preservation of moisture due to the high amount of fber is one of the important factors [20].It seems that fat and hydrocolloids in amaranth four were also effective in reducing hardness (Table 1).Te hardness reduction of cereal products as a result of adding dietary fbers has been reported in other studies [21].Islas-Rabio et al. [3] showed that replacing semolina with amaranth reduces the hardness of pasta.
Te hardness of pasta samples increased during storage (p < 0.05).Staling or hardening of the baked products during storage is a complex process that involves several factors including the recrystallization of gelatinized starch, especially amylopectins, retrogradation of amylose, binding of amylose and amylopectin to each other, moisture migration after crystallization of starch, and reduction of moisture content or distribution of moisture between amorphous and crystalline regions.Te staling of bakery products is related to the moisture content, so there is an inverse relationship between the moisture content and its staling.Water can be efective in reducing hardness by playing the role of a plasticizer.Also, the tendency of fbrous compounds to absorb water causes less gelatinization and recrystallization during storage, which ultimately leads to a reduction in hardness [13].
3.6.Color.By adding amaranth four to pasta, the L and b * values decreased and the a * value increased (Figure 4).During storage, the L * value of all samples decreased and a * and b * values increased (p < 0.05).
Te diference in color parameters can be due to the natural pigments of the amaranth and the hydrophilic role of fbers, which decreased the L and b * values and increased the a * values in the amaranth pasta [7].Te color values in the present study are similar to those found for other gluten-free products containing amaranth [13,[22][23][24].
Te color can be attributed to the interaction of fbers with amylose.Sugar and protein compounds can afect the color parameters.During the cooking process, fber compounds cause a migration of moisture from the crumb to the crust.Another cause of color change is the browning reactions [13].

Amylose Content in Cooking
Water.Te amylose content of all amaranth pasta ranged from 2.03 g to 3.38 g/100 g, which was lower than that of the semolina pasta (4.95 g/ 100 g), as shown in Figure 5.
A higher amylose content is associated with higher hardness and less surface stickiness.Pasta surface stickiness is infuenced by both the surface structure of the strand and starch exuded onto the strand surface during cooking.Amylose decrease increases the stickiness of the pasta.Te higher protein content and lower amylose leach out into cooking water may be the reason for the less stickiness of gluten-free pasta [14].
Tese results are in agreement with the results of Martinez et al. [25].Tey reported that 2-5 g/100 g of amylose leach out in cooking water of commercial spaghetti.

SEM Analyses.
Te microstructure of the functional pasta is shown in Figure 6.Te structure of control pasta is an interwoven network of gluten with many holes and swollen starch granules (Figure 6(a)).Te microstructures of pasta-containing amaranth are slightly diferent (Figure 6(b)).A more uniform structure with fewer holes and a looser gluten network can be seen.
SEM images of gluten-free pasta showed a protein matrix distinct from the gluten network.Tis may be due to the high protein content, fber, and starch of the four used in pasta.Te microstructure showed a fbrous and protein network but not similar to the gluten network.Amaranth pasta showed a smooth but an intact structure when observed in cross section of the pasta which clearly showed the starch molecules that may be the reasons for less starch leaching out during cooking.Te control pasta revealed the gluten protein network with wheat starch molecules embedded in it [14].
3.9.Sensory Characteristics.A 10 obtained the highest score for favor.Te highest score of odor belonged to A10 and A15 samples and the control sample obtained the lowest score.Te semolina pasta (control) and A10 samples showed the highest scores of color and texture.Te highest overall acceptability belonged to the A10 sample, followed by the semolina pasta (Figure 7).Journal of Food Quality Te higher scores in the A 10 treatment are due to the high ability of the fber compounds in amaranth to retain moisture and its more uniform release of moisture during the cooking process [9,10].However, the decrease in sensory characteristics of A 20 treatment is due to the increasing amaranth four substitution and the insufcient cohesion of the gluten network, the reduction of the chewiness, and the aftertaste of amaranth [8].
Buresova et al. [6] showed that the overall acceptability of bread-containing amaranth was negatively infuenced by the favor of amaranth.In the research of Nasir et al. [10], the bread prepared by substituting 5% and 10% of amaranth four is acceptable from the nutritional and sensory points.Derkanosova et al. [8] showed that amaranth bread was similar to traditional samples.Also, amaranth improved the nutritional, sensory, and technological quality of some products [9,13].

Conclusion
Te formulation of gluten-free bakery products presents a challenge to food technologists.Te present study aims at the development of functional pasta mainly covering the evaluation of product quality.
Te results showed that increasing amaranth four weakened the rheological properties of the dough and improved the physicochemical properties of the fnal product.With the increase of amaranth four, the moisture content increased and hardness decreased.Although the cooking loss of enriched pasta was higher than that of the control sample, it was in accordance with the standard limit.Amaranth also reduced amylose leach out compared to the control sample.Amaranth (even in small levels) darkened the fnal product.Amaranth increased the fat, protein, and fber contents of pasta.Te increase in protein and fber can be seen as a reason for the higher nutritional value of pasta products.Tus, amaranth can be used in the formulation of functional baking goods.However, the industrialization of this product requires more studies on increasing shelf life and preventing microbial growth.