FUNCTIONAL AND ANTIOXIDANT PROPERTIES OF NEW BUCKWHEAT PRODUCTS
DOI:
UDK:
JOURNAL No:
Volume 38, Issue 1
PAGES
27-32
KEYWORDS
buckwheat, phenolic compounds, tocopherols, antioxidant activity, crackers, functionality, gluten-free products
Sedej J. Ivana*1
1University of Novi Sad, Institute of Food Technology, 21000 Novi Sad, Bulevar cara Lazara 1, Serbia
*This paper is a result of the research within Project (TR – 20068) supported by the Ministry of Science and Technological Development, Republic of Serbia.
ABSTRACT
ABSTRACT
This study investigated wheat milling fractions (flours T-400, T-500, T-850, wholegrain flour and bran) and buckwheat (Fagopyrum esculentum Moench) milling fractions (hull, groat, dehulled grain, wholegrain flour and refined flour). Content of total polyphenols and total flavonoids, and antioxidant activity were determined in ethanolic extracts of wheat and buckwheat milling fractions. ESR spectroscopy was used for investigation of antiradical activity of wheat and buckwheat milling fraction extracts on reactive superoxide anion and hydroxyl radicals. HPLC analysis was used for quantitative and qualitative determination of polyphenols and tocopherols composition of wheat and buckwheat milling fractions. The correlation between phytochemicals content and antioxidant activity of wheat and buckwheat milling fractions has been analyzed.
After investigation of rheological properties of buckwheat dough, new cracker formulation has been developed and two types of gluten-free buckwheat crackers have been produced. Quality parameters of produced buckwheat crackers (refined and wholegrain) were analyzed and compared with control wheat crackers (refined and wholegrain). Content of total polyphenols and quantitative and qualitative composition of polyphenols and tocopherols were determined in crackers. Scavenging activity of crackers on DPPH radicals has been tested. Shelf-life of buckwheat and wheat crackers was deter-mined applying gas chromatographic analysis of the formed aldehydes as secondary products of lipid oxidation. Sensory quality of the new buckwheat crackers has been established applying point-based method and instrumental analyses of color and texture.
Introduction
Consumers are increasingly interested in functional foods and this has led to greater supply of such products on the market. In the area of bakery products this trend is still relatively underdeveloped (Siro et al., 2008). Therefore, different alternative crops (amaranth, quinoa, buckwheat, etc.), as raw materials, are in focus for development of new bakery products.
Buckwheat (Fagopyrum esculentum Moench) is highly nutritious pseudocereal known as a dietary source of protein with favorable amino acid composition, vitamins, starch, dietary fiber, essential minerals and trace elements (Bonafaccia et al., 2003). Phenolic compounds are also found in abundance in buckwheat, including rutin, orientin, vitexin, quercetin, isovitexin, kaempferol-3-rutinoside, isoorientin, and catechins (Kreft et al., 2006).
In comparison to most frequently used cereals, buckwheat has been reported to posses higher antioxidant activity, mainly due to high rutin content. Another functionnality of buckwheat stems from its gluten-free characteristics making buckwheat suitable for the diet for celiac disease patients.
MATERIAL AND METHODS
Commercially available buckwheat milling fractions (hull, groat, dehulled grain, wholegrain flour and refined flour) and wheat milling fractions (flours T-400, T-500, T-850, wholegrain flour and bran) were compared by: 1) quantification of main antioxidant components: phenolic compounds and tocopherols, and the total phenolics and flavonoids content, and 2) determination of antioxidant activity of milling fraction extracts by different direct and indirect methods (through measuring scavenging activity on 1,1-diphenyl-2-pi-crylhydrazyl (DPPH•), hydroxyl (•OH) and superoxide anion (O2•–)radicals, reducing activity, and chelating activity on Fe2+. Rheological properties of two types of buckwheat and wheat flours (refined and wholegrain) were investigated in order to estimate the potential usage of flours as appropriate ingredients for formulation of bakery products.
New formulations for gluten-free buck-wheat crackers (refined and wholegrain) were developed under the laboratory conditions and compared with wheat based crackers (refined and wholegrain). Proximate composition, content of main antioxidant compounds (polyphenols and tocopherols), antioxidant activity (scavenging activity on DPPH•) and sensory quality were analyzed and compared with those of wheat crackers made from refined and wholegrain wheat flours. Additionally, shelflife of created crackers was compared by determination of five aldehydes selected as markers for lipid oxidation.
Table 1.Total phenolic content, phenolic compounds of crackers and scavenging activity on DPPH•
|
|
Refined |
Refined buckwheat cracker |
Wholegrain wheat |
Wholegrain buckwheat cracker |
|
Total phenolic content |
84 ± 1a |
231 ± 1c |
143 ± 3b |
292 ± 0d |
|
Phenolic compounds (mg/100g) |
|
|||
|
Protocatechuic acid |
0.29 ± 0.01a |
1.59 ± 0.03c |
0.55 ± 0.01b |
2.42 ± 0.05d |
|
Ferulic acid |
0.53 ± 0.00a |
0.69 ± 0.01b |
1.11 ± 0.01d |
0.75 ± 0.00c |
|
Rutin |
n.d. |
2.06 ± 0.05a |
n.d. |
5.02 ± 0.04b |
|
Quercetin |
n.d. |
0.26 ± 0.01a |
n.d. |
0.91 ± 0.06b |
|
Scavenging activity on DPPH• (IC50 mg/mL) |
28.2 ± 1.17c |
1.63 ± 0.07a |
16.2 ± 1.85b |
0.95 ± 0.17a |
Values are means of three determinations ± SD. Values in each row with the same superscript are not significantly different
(P < 0.05). n.d.- not detected
RESULTS
Considering all applied assays for determination of antioxidant activity (electron spin resonance (ESR) spectroscopy and spectrophotometry) it has been concluded that all investigated milling fractions showed remarkable antioxidant activity. Buckwheat milling fractions expressed higher antioxidant potential (Sedej et al., 2010a, 2010b).
These findings suggest the potential improvement of the antioxidant properties of wheat-based food products through addition of buckwheat flour (Filipčev et al., 2011) or even complete replacement of wheat flour.
Mixolab measurements confirmed that the absence of structure-forming gluten proteins influences the resistance of buck-wheat dough (Sedej et al., 2011a). In contrast to bread, in crackers the gluten network needs to be only slightly developed for the dough to be cohesive without being too elastic, and therefore formulation of crackers with complete substitution of wheat buckwheat flour was accomplished. Buckwheat crackers were characterized with higher content of dietary fiber in comparison to wheat crackers. Furthermore, crackers made from buckwheat flours have significantly higher (P < 0.05) total phenolic content than wheat crackers. Quantitative HPLC analysis (Mišan et al., 2011) revealed the presence of protocatechuic and ferulic acid in all tested crackers, whereas two flavonoids, rutin and quercetin were found in buckwheat crackers (Table 1). α-, γ-, δ-tocopherols in crackers were found in the following order: α- >> γ- > δ-tocopherol for all samples (Sedej et al., 2011b).
Content of γ-tocopherol and total tocopherols were significantly higher (P < 0.05) in both buckwheat crackers in comparison to wheat ones.
Consequently, buckwheat crackers were superior in scavenging activity on DPPH• in comparison to wheat crackers as evidenced by their lower IC50 value (Table 1). Sensory analyses of the crackers, which included evaluation of the representative properties of crackers done by the pointsbased method (Table 2), determination of surface color and texture analysis showed that buckwheat flours may be used in gluten-free cracker formulation without adversely affecting the sensory properties of crackers. Buckwheat and wheat crackers are presented in Figure 1.
Lipid oxidation in crackers, containing approximately 30% of vegetable fat, was monitored at the first day when they were baked, after 2 weeks, 1, 4, 6 and 12 months of storage at ambient temperature (22 ± 2 °C). According to the obtained results of static headspace gas chromatographic (SHS-GC) method, there was no significant change in content of propanal, pentanal, hexanal, heptanal and octanal in all cracker samples during four months.
Table 2.Sensory scores of crackers
Property |
Refined |
Refined buckwheat cracker |
Wholegrain wheat |
Wholegrain buckwheat cracker |
|
Appearance |
3,97 ± 0,40b |
4,57 ± 0,40a |
4,66 ± 0,44a |
4,37 ± 0,39ab |
|
Texture |
||||
|
Structure, break, firmness |
4,49 ± 0,79a |
4,79 ± 0,28b |
4,25 ± 0,52ab |
4,14 ± 0,65ab |
|
Chewiness and other textural properties |
3,57 ± 0,69a |
4,46 ± 0,51b |
3,97 ± 0,37ab |
3,83 ± 0,66ab |
|
Aroma |
||||
|
Odour |
3,25 ± 0,67a |
3,18 ± 0,67a |
3,18 ± 0,58a |
3,27 ± 0,68a |
|
Taste |
4,42 ± 1,04a |
4,83 ± 1,41a |
4,70 ± 0,93a |
4,39 ± 1,47a |
|
Weighted mean value |
3,94 |
4,57 |
4,35 |
4,20 |
Scores are means of seven evaluations by seven panelists ± SD. Values in each row with the same superscript are not significantly different (P < 0.05). Scores: 1 – unacceptable, 2 – acceptable, 3 – good, 4 – very good, 5 – excellent.
Figure 1. Appearance of crackers: 1 – refined wheat cracker, 2 – refined wholegrain cracker, 3 – wholegrain wheat cracker, 4 – wholegrain buckwheat cracker
After the sixth month of storage higher increase in aldehydes content was noticed in wheat than in buckwheat crackers, implying longer shelf-life of buckwheat crackers.
CONCLUSION
The results of this PhD thesis could be relevant for the production of gluten-free crackers based on buckwheat flours. Further research needs to be done in order to examine consumer acceptance of the new products and confirm biological activity of new products through in vivo experiments. The introduction of buck-wheat crackers in the market would increase the diversity of functional bakery products and, even more importantly, of functional foods suitable for celiac disease patients.ACKNOWLEDGMENTS
This doctoral dissertation was done as a part of the Project (TR – 20068) supported by the Ministry of Science and Technological Development, Republic of Serbia. I would like to acknowledge the project manager and my comentor Dr. Marijana Sakač for her guidance and assistance throughout the project, and for making it possible. Also I would like to acknowledge my mentor Prof. Dr. Jasna Čanadanović-Brunet for her invaluable guidence. Finally, I would like to thank my colleagues: Dr. Vesna Tumbas, Slavica Sančanin, Petar Grbić, Olivera Šimurina, Dr. Anamarija Mandić, Dr. Aleksandra Mišan and Dr. Mladenka Pestorić for their support, technical expertise and help.