BIOLOGICAL VALUE, ORGANOLEPTIC, PHYSICAL-CHEMICAL CHARACTERISTICS, AND CONFORMATIONAL CHANGES OF PRO-TEIN MOLECULES IN DOUGH GLUTEN-FREE STEAMED BREADS Текст научной статьи по специальности «Биотехнологии в медицине»

BIOLOGICAL VALUE, ORGANOLEPTIC, PHYSICAL-CHEMICAL CHARACTERISTICS, AND CONFORMATIONAL CHANGES OF PRO-TEIN MOLECULES IN DOUGH GLUTEN-FREE

STEAMED BREADS

Shanina O.M.

doctor of technical sciences, professor, Kharkiv Petro Vasylenko National Technical University of Agriculture

Minchenko S.M. postgraduate student,

Kharkiv Petro Vasylenko National Technical University of Agriculture

Dugina K.V. Ph.D.,

Kharkiv Petro Vasylenko National Technical University of Agriculture

ABSTRACT

The effectiveness of different kinds of gluten-free flour application as protein sources and key elements was investigated regarding the impact on nutritional value, organoleptic properties and physical-chemical indicators of steamed breads as well as on conformational changes of protein molecules in dough.

It was established that addition of oilseed and quinoa kinds of flour to corn flour or rice flour increased indexes of biological value and quantity of absorp-tion peaks in the area of a-helixes ma ft-sheets on infrared spectrum of dough. The enhancement of gluten-free steamed bread appearance and increasing of specific volume and porosity were determined. Key words: steamed bread, amino acid content, gluten-free, IR spectroscopy, bread quality.

Introduction. Nowadays the production of foods for particular nutritional uses is rapidly growing. These products do not contain some ingredients are not recommended due to medical contraindications. Such tendency can be explained by increasing quantity of sickness cases of celiac disease, lactose enteropathy and different types of allergic. Celiac disease is known to be a metabolic intolerance to gluten, and is one of the most widespread autoimmune diseases. Up to 1% of the global population suffers from celiac disease. In the USA alone, there are 3 mil-lion patients. It is difficult to diagnose celiac disease in the early stages, because patients frequently suffer from thyroadenitis, diabetes mellitus type 1 prautoim-mune hepatitis coexist as well. As such, it is important to focus public attention on treatment of this illness, and to provide nutritious, alternate food products for the millions of people that suffer from this disease [1].

The only possible way to treat celiac disease is complete exclusion of glu-ten-containing products (wheat, ray, barley) from the patients' diet. Special atten-tion should also be given to those products which contain so-called "hidden glu-ten". For instance, gluten can be used in production of emulsifiers, stabilizers, colorants and other food additives that can be applied in technology of sausages, ice-cream, chocolate, cheese, etc. That is why development of wide range of glu-ten-free products with high nutritional value is a crucial task to provide patients with sufficient levels of necessary nutrients.

Analysis of recent research and publications. Numerous scientists work on development of gluten-free products in Ukraine and worldwide. It is typically recommended to use different gluten-free flours (generally rice, corn, millet and/or buckwheat). The main challenge of such technologies is to get the product struc-ture that is provided by gluten in the usual bread from wheat flour. Generally for solving this task scientists propose to use hydrocolloids (xanthan, gums, starch-es, etc.) [2,3], enzymes, such as transglutaminaze [4,5] and sourdough [6]. All these additives allow to imitate structure of usual bread,

but final products have low content of protein.

Today scientists have already developed a wide range of gluten-free prod-ucts - breads, muffins, biscuits from corn, buckwheat, and rice flour. But as for steamed bread production, this segment of market has not developed enough. Steamed bread is a traditional Chinese bread product that is produced from wheat flour or wheat-rice flour mixture. Steamed bread is widespread in eastern countries (basically in China, Japan, Korea, Thailand) and in the USA, Canada and some European countries as well. It has a few strong benefits which include a decelerating glucose absorption while steaming, reduction of glicemic index, ab-sence of Millard reaction (reducing loses of lysine and other water-soluble amino acids as a result of that) and deficiency of harmful acrylamides (that don't form while steam treatment).

Highlighting of unsolved pats in general problem. The main challenge of gluten-free breads production is formation of the product structure that in the usual bread from wheat flour is provided by gluten. As far as technology of glu-ten-free products requires a complete exclusion of gluten-containing raw materi-als from recipe it is necessary to use effectively highprotein flour of non-conventional grain raw material. As a highprotein ingredients we chose oilseed flour (~44% proteins), flaxseed flour (~32% proteins), quinoa flour (~16% pro-teins) and sorghum flour (~14% proteins). Despite the lower protein content in quinoa and sorghum flour, they have high content of essential amino acids. We were guided by consideration that all chosen kinds of flour allow can improve the bread structure by virtue of increased protein content and enrich the nutrient val-ue of bread due to high content of essential amino and fatty acids, fibers, and vit-amins.

Aim of research. Thus, the aim of this study was to investigate the effec-tiveness of different kinds of gluten-free flour application as protein sources and key elements determining the impact on nutritional value, organoleptic properties and physical-chemical indicators of steamed breads as well as on

conformational changes of protein molecules in dough.

Results & discussion. Supplementation of bread via various grain proteins application is widespread in food industry today. For instance, proteins of leg-umes exceed cereal proteins substantially by amino acid content, protein quality index and protein utility coefficient. But high content of antialimental compounds limits usage of legumes in bread production. That is why such additives as qui-noa, oilseed, flaxseed and sorghum flour and their influence on biological value of gluten-free steamed bread are considered in the current article.

Indexes and criteria that were developed by Academician Lipatov and Academician Rogov are widely used for estimation of biological value of protein components. These indexes are based on elaboration of well-known principle of MitchellBlock. According to the principle, the range of criteria that allow to es-timate amino acids content and its balance in the products were defined [7]. The widespread criteria are

Indexes of biological value of flour mixti

protein utility coefficient, protein quality index, equilibri-um and disequilibrium coefficients of amino acids content and correlative reduct-ancy of amino acids in flour mixtures.

The reasonable flour mixtures (in the context of the best organoleptic char-acteristics) were selected for research:

Cr/Fl - mixture of corn and flaxseed flour in the ratio of 95:5;

Cr/Qn - mixture of corn and quinoa flour in the ratio of 70:30;

Rc/Sg - mixture of rice and sorghum flour in the ratio of 75:25;

Rc/Os - mixture of rice and oilseed flour in the ratio of 95:5.

Samples were compared with two controls:

Cr - corn flour;

Rc - rice flour.

Data of biological value calculation of flour mixtures for gluten-free steamed bread production are presented in table 1.

Table 1

es for gluten-free steamed bread production

Indexes of biological value Cr Cr/Fl Cr/Qn Rc Rc/Sg Rc/Os

Protein Utility coefficient 0,51 0,52 0,54 0,53 0,57 0,60

Protein quality index 0,39 0,51 0,59 0,41 0,54 0,73

Equilibrium coefficient 0,30 0,40 0,51 0,32 0,34 0,93

Disequilibrium coefficient 0,54 0,51 0,46 0,49 0,42 0,24

Correlative reductancy of amino acids 41,54 38,12 30,14 38,69 26,60 24,52

Table 1 show that non-conventional raw materials addition had a positive influence on biological value of gluten-free steamed bread production. In the samples that had corn base (Cr/Fl and Cr/Qn), utility coefficient of protein in-creased by 2% and 6% while adding of flaxseed and quinoa flour relatively in comparison with Cr. Furthermore, protein quality index rose by 31% and 51% relatively. Equilibrium coefficient of amino acids also increased by 33% and 70%, but disequilibrium coefficient conversely decreased by 6% and 15% relatively. Correlative reductancy of amino acids also reduced by 8% and 27%.

The samples that had rise base (Rc/Sg and Rc/Os) demonstrated the similar tendency. Regarding Rc (rice flour only) utility coefficient of Rc/Sg and Rc/Os in-creased by 8% and 13% relatively, protein quality index - by 38% and 78%, equilibrium coefficient of amino acids - by 6% and 190%, as far as disequilibri-um coefficient of amino acids decreased by 14% and 51% and correlative reduct-ancy of amino acids - by 31% and 37%.

On the assumption of obtained results, we can make a conclusion that ap-plication of flaxseed or quinoa flour in the mixture with corn flour and sorghum and oilseed flour in the

mixture with rice flour effects positively on biological value of gluten-free steamed breads, increasing significantly protein quality index and utility coefficient.

Another way of protein biological value estimation consists in Index of Es-sential Amino Acids (IEAA) determination. The main benefit of IEAA is that fact that it considers not only quantity of limited amino acid, but quantity of all es-sential amino acids. That is why on the next stage of experiment we determined IEAA of flour mixtures for gluten-free bread production. Fig 1 shows the results of IEAA analysis.

All simples with non-conventional raw materials showed an upward trend of the most of IEAA. This index increased by 3...19% depending on certain ami-no acid in mixture of corn and flaxseed flour (Cr/Fl). In the mixture of corn and quinoa flour (Cr/Qn) IEAA raised by 2.151%. Tryptophan had the most signif-icant growth. It can be explained by high content of this amino acid in quinoa flour.

It is also established that sorghum flour in mixture with rice flour (Rc/Sg) had a law influence on IEAA (there was a rise by 1.13%). Application of oilseed flour increases IEAA by 55.180%. The substantial improvement is ex-plained by high content of high-quality protein in oilseed flour.

Tryptophane Threonine Methionine

Tryptophane Threonine Methionine

0,00 0,20 0,40 0,00 0,80 1,00 1,20 □ Cr ■ Cr/Fl ■ Cr/Qn

0.00 0,40

□ Re ■ Rc/Sg IRc/Os

Fig. 1 Influence of non-conventional raw materials on IEAA of flour mix-tures (A - on the basis of corn flour, B - on the basis of rice flour)

Thus, conducted research of IEAA of flour mixtures for gluten-free steamed bread production showed that the application of mixture from corn and quinoa flour in the ratio of 70:30 and the mixture from rice and oilseed flour in the ratio of 95:5 shown significant effect on biological value of steamed breads.

As far as non-conventional raw materials have not only increased content of essential amino acids but also high amount of protein, we suppose that it can cause changes of quality characteristics of bread. That is why on the next stage of experiment the research of organoleptic properties and physical-chemical indica-tors of gluten-free steamed breads was conducted.

The organoleptic properties and physical-chemical indicators of breads are considered by customers as the most significant. Marketing studies show that majority of Ukrainian customers prefers products with pleasing odor, taste and appearance, and only after organoleptic estimation they pay attention to nutri-tional value of product. Taking this aspect into consideration, we determined ap-pearance of gluten-free steamed bread and their physical-chemical indicators such as specific volume and porosity.

The surface and porosity of products substantially increased (fig.2). Use of flaxseed, quinoa, sorghum and oilseed flour led to obtaining of equable structure of crumb and film-alike crusts.

Fig. 2 Appearance of gluten-free steamed breads

Furthermore application of flour from non-conventional raw materials had vari-ous influence on specific volume and porosity of gluten-free steamed bread. Ob-tained data are displayed in table 3. Remarkably, the application of flaxseed flour contributed increasing specific volume of corn steamed bread by 3% and margin-ally decreased its porosity. Taking

these results into consideration, high content of fats in flaxseed flour that prevented the porosity development would explain such effect. The application of quinoa in the mixture with corn flour increased specific volume of bread by more than two times and porosity - by 30%.

Table 3

Influence of flour from non-conventional raw materials on physical-chemical indicators of gluten-free steamed breads

Sample Specific volume, g/cm3 Porosity, %

Cr 1,60±1% 44±3

Cr/Fl 1,65±1% 40±2

Cr/Qn 2,9±2% 57±3

Rc 1,85±1% 39±1

Rc/Sg 3,90±2% 41±1

Rc/Os 4,25±2% 56±2

Influence of sorghum and oilseed kinds of flour on specific volume and po-rosity of rise breads had a similar character, but oilseed flour improved physical-chemical indicators of bread more significantly. The specific volume increased by more than 2,3 times and porosity - by 44%. The obtained data correlate with re-search of infrared spectroscopy of dough regarding the most significant influence of oilseed flour as well.

It is known that amino acid composition can influence on conformational characteristics of proteins. During kneading of dough from flour mixtures, some changes are expected to take place in protein molecules structure. This process leads to changes of physical and chemical properties of dough. Basing on this reasoning, we analyzed infrared spectrums of dough simples from studied flour mixtures.

To gain a deeper insight on the effect of non-conventional raw materials on the functionality of the cereal proteins, Infrared spectroscopy was used to inves-tigate the conformational proteins structure of the dough and steamed bread. In-frared spectroscopy results explain the influence of different factors on conforma-tional changes in protein molecules by means of interpretation of absorption peaks displacement and their intensity. Structural components of protein mole-cule have nine absorption bands in the middle infrared area. They are Amides: A, B, I, II, III and IV, V, VI, VII [8].

The aim of Infrared spectroscopy research of dough was to

Characteristics of infrared absorption band Amid

estimate possi-ble interaction between proteins of corn flour and flaxseed/quinoa flour and rice flour and sorghum/oilseed flour.

Absorption spectrum of dough had intensive band of Amid I that is indica-tive for protein carbonyl group with absorption maximum over 1670 cm-1; feebly marked band of Amid II over 1530 cm-1. Valence vibrations of -OH group nearby 3400 cm-1 and 1021 cm-1 indicated the presence of polysaccharides. Peaks around 1740 cm-1 of all samples of dough can be explained by presence of -C=O group of ethers, together with asymmetrical and symmetrical valence vibrations of -CH3 group (2950 - 2920 cm-1) shown existence of a little quantity of lipids in the dough. Experiment samples had differences in intensity of absorption bands and length of base lines.

Interpretation of experimental data can be complicated by presence of wa-ter in the dough. That is why we analyzed absorption band Amid III with the aim to elaborate obtained results. Amid III absorption band (1350 - 1200 cm-1) in the middle infrared area is responsed for deformation vibrations of N-H bond to-gether with valence vibrations of C-N group, and deformation vibrations of C-H bonds [9]. In the area of absorption band of Amid III, vibrations of -OH group of water molecules do not influence on protein absorption spectrum. The results of quantitative analysis of absorption peaks of infrared spectrum are displayed in Table 2.

Table 2

III of dough for glu-ten-free steamed bread production

Elements Absorption peaks, cm-1

of protein Cr Cr/Fl Cr/Qn Rc Rc/Sg Rc/Os

secondary

structure

a-helix 1292 1297 1295 1310 1298 1299

1304 1304 1305 1316 1303 1305

1308 1308 1308 1322 1320 1314

1314 1314 1314 1322 1319

1320 1320 1321 1324

1323 1325 1326

1326 1328

parallel 1239 1221 1220 1239 1221 1225

ß-sheet 1243 1224 1226 1240 1228

1226 1240 1234

1240 1244 1237

1242 1246 1242

1243

nonparallel 1280 1277 1275 1277 1277 1273

ß-sheet 1288 1280 1281 1280 1280 1276

1285 1285 1286 1288 1287 1283

1292 1288 1288 1293 1289

1293 1295 1291

irregular 1266 1265 1259 1258

regions 1268 1267

1259

Obtained data shown that application of flour of non-conventional raw ma-terials led to increasing a- helimerization of protein molecule (with rigid structure) and appearance of additional absorption peaks in the area of ^-sheets that indicates the adjustment of protein molecule and strengthening of hydrogen bonds. Thus, application of flaxseed and quinoa flour in mixture with corn flour led to formation of 2 and 1 additional absorption peaks respectively in the area of a-helixes, application of sorghum and oilseed flour in mixture with rise flour - 1 and 3 additional absorption peaks in the area of a-helixes and 1 and 4 additional absorption peaks in the area of ^-sheets respectively. Additional 4 and 3 absorp-tion peaks in the area of ^-sheets exist while adding of flaxseed and quinoa flour to corn flour as well.

Obtained results point at the formation of more adjusted protein molecules structure that is associated with formation of additional absorption peaks in the area of a-helixes and ^-sheets, and disappearance of irregular structures (in the case of application of quinoa and sorghum flour).

Conclusion. The results of the present study show that the functionality of gluten-free corn and rice kinds of flour in terms of streamed breadmaking performances can be successfully improved by the application of flour from non-conventional raw materials (flaxseed, quinoa, sorghum and oilseed). Biological value and structure of final products gluten-free steamed bread improves sub-stantially in case of using flour mixtures regarding a certain type of flour. The most significant influence has mixture from quinoa flour corn flour and mixture from oilseed flour and rice flour. Such mixtures allow to improve biological val-ue, specific volume, and porosity of breads. Furthermore the quantity of energeti-cally favourable parallel and nonparallel ^-sheet was increased in dough from proposed flour mixtures that has a positive effect on dough structure.

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