Assessment of the physicochemical profile of gluten-free flour and pasta products

The production of food products that do not contain gluten is being actively developed since it is not recommended for certain medical reasons, such as celiac disease. Therefore, developing high-quality and highly nutritional gluten-free (GF) pasta products is crucial. A shortage of domestic gluten-free food products characterises the consumer market of Kazakhstan. Buckwheat, rice, and corn flour are widely used to make gluten-free pasta. The results of the study showed that buckwheat flour contains significantly higher amounts of protein (11.9%), ash (1.54%), iron (2.47%), calcium (38.53%), magnesium (56.11%), phosphorus (267.55) and lower carbohydrate content (67.99%) compared to rice and corn flour. Moreover, pasta made from buckwheat flour also showed higher protein 9.39%, Ca (28.80 mg/100g), Mg (48.28 mg/100g), Fe (2.28 mg/100g), Na (5.50 mg/100g), P (196.45 mg/100g) content. Also, amino acids, such as lysine, tyrosine, alanine, valine, etc., were elevated in buckwheat flour-based pasta. Taken together, these data hint that buckwheat has the potential to become a nutrient-rich GF paste ahead of corn and rice. However, further research is needed to determine the cooking qualities and consumer acceptability.


INTRODUCTION
Currently, the production of special foods, including products that do not contain certain ingredients whose presence in food is not recommended for certain medical reasons (allergens, certain types of proteins, oligosaccharides, polysaccharides, etc.). is being actively developed [1].Celiac disease is an immune-mediated enteropathy arising from consuming prolamins of wheat, rye, and barley.A lifelong adherence to a gluten-free diet is known to be the only therapeutic option for individuals with celiac disease [2].The consumer market of Kazakhstan is characterised by a shortage of domestic specialised food products, including gluten-free products, which determines the need to expand their range and develop recipes and innovative production technologies [3], [4].The food engineering of gluten-free flour products is described by two main directions: products based on natural gluten-free raw materials, mainly of plant origin (gluten-free cereals, pseudo-cereals, legumes, nuts, etc.).The biocatalytic direction focused on removing or modifying gluten in gluten-containing raw materials [5].The degree of complexity in the production of gluten-free products is closely related to the role of gluten in the technological system, which is a structure-forming agent.Obtaining high-quality gluten-free products requires the search for ingredients capable of replacing them.Until now, recipes of gluten-free pasta products based on amaranth, corn, rice, chickpea and buckwheat flours are proposed [6], [7], [8].Rice and corn are more popular raw materials in gluten-free pasta production.Meanwhile, buckwheat, amaranth, quinoa, teff and oats are becoming increasingly popular in production as they improve the nutritional content of products [9].The production of pasta products of high quality and high nutritional content is one of the basic conditions for improving nutrition in general.Nevertheless, there is a shortage of established GF paste recipes based on non-

Laboratory Methods
The tests of proximate chemical composition were conducted for flour as well as for different GF pasta.The protein, fat, total ash, starch, and testable acidity were analysed according to the GOST 10846-91 [10], GOST 29033-91 [11], GOST Р 51411-99 [12], GOST 10845-98 [13], GOST 27493-87 [14], respectively.In addition, the mass fraction of carbohydrates was detected using the permanganatometric method.The GOST 13496.3-92 [15] was used to determine the moisture content and pH.Mineral contents were analysed according to the GOST 32343-2013 (ISO 6869-2000) [16, 17] by the atomic absorption spectroscopy (AAS) method, which is the quantitative analysis based on the properties of atoms to absorb light at a certain wavelength (resonance absorption).Vitamin A content was examined based on GOST Р54635-2011 [18].Besides, the hydro-soluble vitamins were determined using GOST Р 50929-96 (М-04-41-2005) [19].The energy value of pasta products was calculated based on the actual content of proteins, fats, and carbohydrates.
Determination of total arsenic (Ars) was conducted by atomic absorption spectrometry with hydride generation with preliminary mineralisation of the sample under pressure using the GOST 30178-96 [20].Inversionvoltamperometric methods were used for determining the content of cadmium (Cd), lead (Pb), and mercury (Hg) according to GOST EN 14083-2013 [21].This method is based on the ability of elements to electrochemically precipitate on the indicator electrode from the analysed solution at a given potential of the limiting diffusion current, and then dissolve in the process of anodic polarisation at a certain potential characteristic of each element.
The amino acid profile of developed formulations was analysed to maximize the biological value of pasta products.The amino acid profile of raw materials was studied under GOST 31480-2012 (М-04-

Description of the Experiment
Sample preparation: The flour samples were obtained from the local market.Subsequently, 50 g were extracted from each sample manually.Then, samples were dried in air or a desiccator.The thoroughly mixed material was placed in a clean and dry test tube for further experiments.

Design of the experiment:
In the first phase, we obtained non-conventional GF raw materials and determined the proximal composition of rice, corn, and buckwheat flour.In the next phase, we generated two different GF pasta using rice, corn, and buckwheat flour as raw materials.The recipe of the developed pasta samples is given in Table 1.The dough was made with room temperature water (cold mixing, 30 °C).After kneading, all the samples were rounded, placed in polythene bags, and kept at room temperature for 1 hour.Then, the samples were rolled using a regular rolling pin to form pasta straws 1 mm wide and 50 mm long.After, the samples were photographed, labelled, described, and placed in a drying cabinet at 40 °C for 4 hours so that the final moisture content was not lower than 13%.Finally, the proximal composition of developed GF pasta samples was detected.

Statistical Analysis
All data were computed on one-way analysis of variance (ANOVA) or independent sample t-test, followed by the least significant difference (LSD) test to calculate significant differences between the samples (p ≤0.05) using SPSS software (version 25.0, IBM Corporation, New York, USA).Outcomes were expressed as triplicate analyses' mean ± standard deviation (SD) values.

RESULTS AND DISCUSSION Study of the chemical composition of rice, maise, buckwheat flour
The quality of food products, including gluten-free pasta, is largely determined by the quality of raw materials.As can be seen in Table 2.The buckwheat flour contains a significantly higher amount of protein (11.9%), ash (1.54%), TA (8.4 °T), iron (2.47%), calcium (38.53%), magnesium (56.11%), phosphorus (267.55) and lower carbohydrate content (67.99%) compared to rice and corn flour (p <0.01).A recent study reported that the flour from Fagopyrum esculentum and Fagopyrum tataricum buckwheat varieties also exhibited higher protein content (11.81-14.90%),ash (2.58-2.85%)and lower total carbohydrate (61.69-67.83%)compared to hard wheat flour [24].It was shown that protein and ash content in buckwheat flour fractions increased in the order from internal to external fractions [25].Rice flour differs significantly from others in carbohydrate content (76.62%).Similar amounts of total carbohydrates were found in Thai rice varieties, although this may depend on variety and processing [26].It is reported that the longer the hydrolysis lasts, the higher the carbohydrate content of white rice flour [27].The presented values indicate that a higher fat content is found in corn flour (1.71%).The lipid content of treated and untreated white and yellow maise varieties differed significantly [28].Moreover, rice and corn flour lagged behind buckwheat flour in iron, calcium, and magnesium content.In a previous study, enhanced Ca and Mg were found in white buckwheat flour [33].Another paper emphasizes that buckwheat is used as a "smart food" because it is high in nutrients and minerals such as Ca (110 mg/100g), Mg (231-390 mg/100g), and P (330-347 mg/100g) [34].
Safety is a crucial aspect of the food products industry.Metals are widespread and at certain concentrations, including some heavy metals, lead to health issues.Regarding toxic trace elements, Pb (lead) and Cd (cadmium) were detected in rice and corn flour, while As (arsenic) and Hg (mercury) were not identified in all GF flour samples.Mercury is particularly dangerous because of its highly toxic effect and its ability to accumulate in the body [35].Analysis of the results showed their safety and compliance with TR TS 021/2011 requirements.Of interest is that rice-based foods have been shown to contain significantly more toxic elements [36], which may be due to contaminated soil.In terms of amino acid composition, the buckwheat flour was rich in indispensable amino acids, including lysine, histidine, leucine+isoleucine, phenylalanine, methionine, threonine, valine compared to other flour (p <0.01) (Table 3, Figure 1).The results suggest that buckwheat significantly exceeds other cereal crops' nutritional value and protein content.Saeed et al. revealed that lysine (1.03-11 g/kg), isoleucine (0.88-1.19 g/kg) and leucine (1.01-1.05g/kg) in buckwheat cultivars flour [37].Notably, it has been demonstrated that egg-white protein-fortified pasta increases nutritional quality [38].It should be noted that amino acid profiles may vary according to soil, cultivar, and climate.

Study of the chemical composition of rice, maise, buckwheat flour-based pasta
The obtained results of experiments on the determination of proximal chemical content in the selected pasta samples indicate that the protein content in the buckwheat and corn starch-based pasta demonstrated significantly greater (p <0.05) protein content 9.39%, Ca (28.80 mg/100g), Mg (48.28 mg/100g), iron (2.28 mg/100g), Na (5.50 mg/100g), P (196.45 mg/100g) compared to rice and corn flour-based GF pasta (Table 5, Figure 5).Besides, the recipe No. 2 exhibited lower starch (1.63%) and higher moisture content (6,47%).The pasta made of buckwheat flour also showed similar protein content in a previous study (9.9%) [41].In addition, noodles prepared with buckwheat, corn, and potato starches contained more potassium, phosphorus, and magnesium, while mineral content decreased with increasing amounts of starch [42].The pasta made of rice and corn flour showed higher total starch (69.2%) in our study.A previously published study also reported that rice-based GF pasta exhibited greater total starch (89.3%) content [41].Arcangelis et al. reported that gelatinization of buckwheat, rice, and corn flours using 0.1% propylene glycol alginate and 0.5% fatty acid monoglycerides proved to be the best combination to produce a gluten-free paste with good nutritional and culinary properties [41].
Therefore, it was suggested that other pseud o-grain-based flours, such as amaranth, can be added to the ricecorn pasta to increase its protein content.For example, rice-based GF pasta enriched with amaranth flour or soybean flour showed increased protein content [43], [44].Also, the corn pasta prepared with 70% corn flour and 30% broad bean flour resulted in increased protein content [45].The presence of essential amino acids may determine the biological value of proteins, and the amino acid content of GF pasta may depend on different raw materials.Our results indicate that pasta products based on buckwheat flour and corn starch showed elevated levels of almost all amino acids except histidine, methionine, and proline (Table 6).The essential amino acids, including phenylalanine (6.93-7.27%),leucine (7.23-8.52%),and lysine (5.83-6.03%)were detected in buckwheat noodles [46].A previous study on buckwheat cookies

Figure 1 Figure 2
Figure 1 Chromatograms of amino acid composition of a) rice flour, b) corn flour, and c) buckwheat flour; the xaxis is a retention time (min), and the y-axis represents abundance.

Figure 3 Figure 4
Figure 3 Chromatograms of amino acid composition of pasta A) No.1 recipe; B) No.2 recipe.

Figure 5
Figure 5 Ready pasta made from rice-corn flour (left) and from buckwheat flour (right).

Table 1
Recipe of pasta samples based on GF flour.
A, B, C mean p <0.01.

Table 3
Amino acid profile analysis of different GF flour.

Table 4
Water-soluble vitamin contents of different GF flour.

Table 5
Physicochemical composition of the two different manufactured GF pasta.