Template LAAR 2021

Abstract-- In the study the grape seed flour (GSF) at 7.5% and 15% ratio was blended with wheat flour (W), siyez wheat flour (S) and oat flour (OAT) separately in muffin recipe. The total flavonoid content, total antioxidant capacity, phenolic profile using HPLC-PDA and sensory properties of prepared muffins were determined. Total flavonoid contents of each three muffin were increased significantly (p<0.05) by addition of grape seed flour. Besides, the muffins with OAT had higher total flavonoid content and total antioxidant capacity values than S and W samples. Identified ten phenolic compounds were o-coumaric acid, caffeic acid, gallic acid, phlorizin, kaempherol, trans-resveratrol, (-)-epicatechin, t-cinnamic acid, (+)-catechin and epigallocatechin gallate. W15 muffin was mostly liked, following with S15 and OAT15 according to crust color, odor, and crumbliness characteristics. The GSF used in muffin formulations up to 15% increased nutritional quality and functional properties without adverse effect on sensory quality.

Keywords-- Bakery products; functional food; phenolic compounds; sensory analysis; antioxidant analysis

I. INTRODUCTION

Bakery products such as muffins are extensively eaten all over the world and traditionally refined wheat flour is used in the original recipe which is deficient in the natural bioactive components like dietary fiber, antioxidants and therefore may cause lowered health benefits. Considering the popularity of the baked products, the enrichment is an effective way to improve the nutritional quality. Because consumer behavior and eating habits change and people prefer to consume foods with high nutritive value. Thus, a favorable way to enhance the bakery products with supplementation by using dried fruit and vegetables, vitamins, minerals, antioxidants, fibers, by products to produce high nutritional value cakes (Kim et al., 2012; Salehi and Aghajanzadeh, 2020; Goswami et al., 2015; Martins et al., 2017).

According to FAO (2019) reports, food loss produced during processing of foods is US$310 billion in developing and US$680 billion in industrialized countries. Use of food by-products is an effective solution for management of this loss (Salehi and Aghajanzadeh, 2020; Iriondo-DeHond et al., 2018). Powder form of the dried fruits and vegetables by-products can be used as a nutrient source for bakery products. Use of by-product reduces waste with saving the expenses in food factories (Salehi and Aghajanzadeh, 2020) and negative effects on the environment by residue accumulation and denote an important chance for the agroindustry (Larrosa and Otero, 2021).

In last years, wheat flour used in bakery products such as cakes, bread, biscuits, muffins, cupcakes, snacks have been fortified with different nutritional ingredients and by-products. Grape seed powder is the one of the most powerful by-product of food industries has been used as a blend alternative for bakery products, meat fortification and antioxidant for oils (Larrosa and Otero, 2021; Yalcin et al., 2021; Martins et al., 2017; Coelho et al., 2020; Andrade et al., 2019). According to studies there are 15 polyphenolic compounds, including 11 flavane-3-alcohols ((−)-epicatechin, (+)-catechin, epigallocatechin gallate, proanthocyanidins (B1, B2, B3 and B4), gallate C1, B1-3-O-gallate, B2-3-O-gallate and B2-3 '-O-gallate), 3 flavonols (quercetin, kaempferol and myristin), and phenolic acid (gallic acid) in the grape seed extract. Proanthocyanidins in grape seeds have a wide range of antioxidant system, containing chelation, free radical scavenging and inhibition of polyphenol oxidase. Studies in vitro with grape seed extract showed that oxidative stress of proliferating cell nuclear antigen protein expression in heart muscle is decreased due to antioxidant activity. Also, the activities of some antioxidant enzymes, for example superoxide dismutase, catalase, and glutathione peroxidase are enhanced in vitro (Chen et al., 2020; Coelho et al., 2020; Andrade et al., 2019). According to studies it was concluded that grape seeds have numerous health benefits, like anticancer, antioxidative, anti-inflammation, lipid-lowering, neuroprotective, hypotensive and bacteriostatic effects and can be used as a food additive, food preservative, healthy food ingredient, and food packaging material at labscale (Chen et al., 2020; Cho, et al., 2018; Coelho et al., 2020).

Noodles prepared with blend of wheat flour and grape seed powder showed that 1% grape seed powder addition supported the combination of gluten proteins by stimulating hydrophobic interactions and hydrogen bonding, consequently increased the noodle quality (Chen et al., 2021). In the study of Peng et al. (2010), 0.3 g, 0.6 g and 1 g grape seed extract containing 95% proanthocyandins including epicatechin and catechin was added to 350 gr white bread flour separately and obtained three different bread (500 gr) were analyzed. The effect of heat treatment on health was researched by measuring NƐ-(carboxymethyl)lysine (CML) and antioxidant content. They concluded that bread produced by mixing of wheat flour with grape seed extract provided increased antioxidant activity and lowered CML on bread crust nearly 30-50% depending on dose. Utilization of grape seed extract in bread formulation is encouraging for development of functional food with reduced heath risk (Peng et al., 2010).

Muffins prepared with replacing wheat flour with buckwheat flakes/amaranth flour blend at 33 or 50% enhanced nutritional and antioxidative properties (Antoniewska et al., 2018). Muffin made with 20% chia seeds had significantly increased mineral content (calcium, phosphorus, zinc and iron) and 20% total antioxidant activity (Sharma et al., 2020). Muffins formulated with ground flaxseed at 10% enriched the nutrients and enhanced its antioxidant potential (Kaur and Kaur, 2018). The effect of grape by-products on CML level was investigated with muffin model and results showed that formulation of muffins at 20% level grape by-products reduced the amount of CML with no significant changes in sensory profile (Mildner-Szkudlarz et al., 2015). Functional muffins were prepared by blending grape seed flour with whole wheat, whole siyez wheat and whole oat flours and results showed that antioxidant capacities were increased with addition of grape seed flour with acceptable sensory characteristics (Yalcin et al., 2021).

Cupcakes are a popular bakery product because of their suitable form for eating, taste, and long shelf life. Cupcakes are like muffins which available in small portions and takeaway form of the cakes. In traditional recipe, they are prepared by using wheat flour, which is deficient in lysine, tryptophan and in some minerals. Enhancement of cupcakes with some functional foods or by- products may improve dietary nutrients for consumers. They are useful for fortification, and one of the most preferred types in bakery shops. Mirani and Goli (2021) used eggplant in the cupcake formulas and obtained low calorie, high antioxidant, and fiber content than control (Mirani and Goli, 2021). Ayoubi et al. (2022) fortified cupcake with pomegranate seed powder which is a by-product of the pomegranate juice factories and increased the protein, fat, and fiber contents of cupcakes significantly. They concluded that %5 pomegranate seed powder addition is an optimum amount in case of sensory attributes (Ayoubi et al., 2022). Abdel-Moemin (2016) used the Roselle calyces for enrichment of cupcakes because of the high content of its phytochemicals. Cupcakes formulated with Roselle calyces extract at 20% showed increase in anthocyanins (465 mg/100 g) and dietary fiber (8%) and also panelists gave higher overall liking score (Abdel-Moemin, 2016).

The aim of this study is to improve nutritional quality of muffins and obtain functional bakery products by using grape seed and find alternative ways for waste management as a value-adding by-product. For this purpose, using various flours (wheat (Triticum aestivum L.), siyez wheat (Triticum monococcum L.), and oat (Avena sativa L.)) was blended with grape seed flour (GSF) at 7.5% and 15% level and the influence of grape seed flour addition on three different flour on their antioxidant capacities, phenolic profile and sensory attributes of muffins were investigated.

II. METHODS

A. Materials

For the determination of flavonoid contents and antioxidant capacities, quercetin (≥95%), ethanol (≥99.8%), neocuproine (Nc) from Sigma-Aldrich Chemie GmbH (Steinheim, Germany); methanol (≥99.9%), formic acid (≥98%), sodium nitrite (NaNO₂), sodium hydroxide (NaOH), potassium persulfate (K₂S₂O₈), dipotassium hydrogen phosphate (K₂HPO₄), potassium dihydrogen phosphate (KH₂PO₄), copper (II) chloride (CuCl₂) and ammonium acetate (NH4Ac) from Merck KgaA (Darmstadt, Germany); 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) and aluminum chloride (AlCl₃) from Fluka Chemie (Buchs, Switzerland); potassium chloride (KCl) from Riedel-de Haen Laborchemikalien GmbH (Hanover, Germany) were purchased. All chemicals used as standards in HPLC-PDA analysis including o-coumaric acid, caffeic acid, gallic acid, phlorizin, kaempherol, trans-resveratrol, (-)-epicatechin, t-cinnamic acid, (+)-catechin and epigallocatechin gallate were obtained from Sigma-Aldrich Chemie GmbH (Steinheim, Germany).

B. Sample preparation

Muffins have been produced by reference to the procedure of the working sample of Topkaya and Işık (2019). Grape seed flour was purchased from a well-known local brand (Arifoglu, Arifoglu Co., Istanbul, Turkey). Product formulations were given in detail in Table 1. First, the eggs were prepared by beating them in a whisk machine (Bosch mum 58920) at high speed for six minutes. Then sugar was added and whisked at high speed for 4 minutes. Milk, sunflower oil, and yoghurt were added and mixed at average speed for another minute. Finally, according to the type of flour in the formulation, flour, vanilla, baking powder and grape seed flour were added, if necessary, according to the type of formula, and mixed with the help of a spatula by gently tempering. Prepared mortar cake mold 24 to split muffins (Metaltex Istanbul Turkey), 52x45 mm muffins divided in equal amounts to paper (21 g) are added. Muffins were cooked in an oven (Bosch, Germany) at 175°C for twenty minutes, and carefully removed from the mold after cooling at room temperature. The cakes were placed in sealed plastic containers and stored in a dry and cool environment for analysis. Pictures of prepared muffins according to Table 1 were shown in Fig. 1.

C. Preparation of extracts

Conditions were optimized for extraction, and 3 parallel extracts were prepared according to Çapanoglu et al. (2008). Two grams of muffins were mixed with five ml of solvent containing 0.1% formic acid in 75% aqueous

Table 1. Product formulations.

PRODUCTS	INGREDIENTS g / 100 g product
PRODUCTS	whole wheat/ siyez/ oat flour	Grape seed flour	egg	sugar	salt	sunflower oil	yoghurt	baking powder	vanillin
W	21.86	0.00	9.67	19.34	16.44	12.96	16.83	1.93	0.97
W7.5	20.22	1.64	9.67	19.34	16.44	12.96	16.83	1.93	0.97
W15	18.58	3.28	9.67	19.34	16.44	12.96	16.83	1.93	0.97
S	21.86	0.00	9.67	19.34	16.44	12.96	16.83	1.93	0.97
S7.5	20.22	1.64	9.67	19.34	16.44	12.96	16.83	1.93	0.97
S15	18.58	3.28	9.67	19.34	16.44	12.96	16.83	1.93	0.97
OAT	21.86	0.00	9.67	19.34	16.44	12.96	16.83	1.93	0.97
OAT7.5	20.22	1.64	9.67	19.34	16.44	12.96	16.83	1.93	0.97
OAT15	18.58	3.28	9.67	19.34	16.44	12.96	16.83	1.93	0.97
W: Whole wheat muffin cake; W7.5: Whole wheat muffin cake with 7.5% grape seed flour; W15: Whole wheat muffin cake with 15% grape seed flour; S: Whole siyez wheat muffin cake; S7.5: Whole siyez wheat muffin cake with 7.5% grape seed flour; S15: Whole siyez wheat muffin cake with 15% grape seed flour; OAT: Whole oat muffin cake; OAT7.5: Whole oat muffin cake with 7.5% grape seed flour; OAT15: Whole oat muffin cake with 15% grape seed flour.

Figure 1. Method of preparation and picture of the prepared muffins from left to the right; a) W+0% GSF, W+7.5% GSF and W+15% GSF b) OAT+0% GSF, OAT+7.5% GSF and OAT+15% GSF c) S+0% GSF, S+7.5% GSF and S+15% GSF

methanol. The prepared aliquots were centrifuged in ul-trasonic bath (Kudos, Shanghai, China) at 4 ° C, 9000 rpm for 10 minutes and supernatants were collected (Universal 320R, Hettich Centrifuge Tuttlingen, Germany). The extraction procedure was performed two times, and 2 supernatants of this procedure were collected to a final volume of ten ml in a tube. Finally, the extracts were stored at -20 °C in the refrigerator until they are analyzed.

D. Determination of total flavonoids

The total flavonoids (TF) were measured colorimetrically using the method of Kim et al. (2003). 250 µl of the sample extract, 1.25 ml of distilled water and 75 μl of 5% sodium nitrite (NaNO2) were mixed and waited for 6 min. Later 150 μL aluminium chloride hexahydrate (AlCl3.6H2O) was put into the solution by stirring carefully and rested for 5 min. Then 500 µl of 1 M sodium hydroxide (NaOH) was incorporated. The total aliquot was completed to final volume of 2.5 mL with distilled water. The mixture absorbance value was determined at 510 nm using UV-Vis spectrophotometer (Beckman Coulter, DU730, California, USA) and the total flavonoid content with reference of quercetin standard curve was found and described as mg of quercetin equivalent / 100 g sample (mg QE/100 g).

E. Determination of total antioxidant capacity

CUPRAC assay method was used to determine total antioxidant capacity (TAC) (Apak et al., 2004). Used standard was Trolox in the method and data was expressed as mg of Trolox equivalent (TE) per 100 g sample.

10⁻² mM CuCl₂.2H₂O solution, NH4Ac buffer at pH 7.0, 7.5 × 10⁻³ M neocuproine (Nc) solution were prepared. 1 mL of CuCl₂.2H₂O solution, 1 mL of Nc solution, 1 mL of NH₄Ac buffer, 1 mL of distilled water were mixed with 100 μl of sample extract. For measuring samples, extracts were diluted ten times to be in a linear range. The absorbance was measured at 450 nm after 30 mins with UV-Vis spectrophotometer (Beckman Coulter, DU730, California, USA).

F. Determination of phenolic profile using HPLC-PDA

Individual phenolic compounds were identified and quantified according to the methods of Capanoglu et al. (2008). 0.45-μm-membrane filters were used for filtration of extracts and injected into Waters W600 (Waters Co., Milford, MA, USA) high-performance liquid chromatography (HPLC) system. Photodiode array (PDA) (Waters 996) and fluorescence (Waters 2475) detectors and a Luna 3 µ C18 150 × 4.60 mm column (Phenomenex, Torrance, CA, USA) was utilized in HPLC. The spectral determination was done at 280 and 312 nm with the appropriate solvents which were mobile phase solvent A, 0.1% (v/v) Milli-Q water TFA and solvent B, 0.1% (v/v) TFA acetonitrile at 1 mL/min flow rate and 10 μL injection volume. A linear gradient was arranged as 95% solvent A and 5% solvent B at 0 min, 65% solvent A and 35% solvent B at 45 min, 25% solvent A and 75% solvent B at 47 min and at 54 min go back to the initial settings. Figure 2 shows the HPLC-PDA chromatograph of whole oat muffins added with 15% grape seed flour. The retention times were used for identification for UV spectra and quantification with external standard curves. All analyses were performed in triplicates and the results were expressed as μg/g of sample.

Table 2. Total phenolic and flavonoid contents and antioxidant capacities of muffin cakes

PRODUCTS	Total flavonoid (mg QE/100 g sample)	CUPRAC (mg TEAC/100 g sample)
W	110.00±14.49^g	165.77±6.92^f
W7.5	197.64±17.82^de	192.71±17.66^e
W15	295.39±5.62^b	220.10±5.92^cd
S	170.11±28.25^e	198.32±25.71^de
S7.5	250.45±9.60^c	208.99±1.00^cde
S15	338.65±32.31^a	251.65±12.53^a
OAT	138.65±24.69^f	224.82±23.33^bc
OAT7.5	203.26±14.95^d	245.02±11.59^ab
OAT15	353.26±13.04^a	257.15±10.89^a

Different letters within the column across the table show significant differences at α = 0.05. W: Whole wheat muffin cake; W7.5: Whole wheat muffin cake with 7.5% grape seed flour; W15: Whole wheat muffin cake with 15% grape seed flour; S: Whole siyez wheat muffin cake; S7.5: Whole siyez wheat muffin cake with 7.5% grape seed flour; S15: Whole siyez wheat muffin cake with 15% grape seed flour; OAT: Whole oat muffin cake; OAT7.5: Whole oat muffin cake with 7.5% grape seed flour; OAT15: Whole oat muffin cake with 15% grape seed flour.

G. Sensory analysis

Ranking test method was used to analyze the sensory preference of grape seed flour enriched muffin formulations. Eighteen trained panellists were selected from a pool of 32 panellists based on sensory panelist education procedures (ISO 5496, 2006; ISO 3972, 2011) in ranking test. These panellists were educated by depending on ISO standards for sensory analysis (ISO 8586, 2012) and subjected to performance monitoring (ISO 11132, 2012).

Sensory analysis was completed in accredited sensory analysis laboratory in Bursa Turkey (Republic of Turkey Ministry of Agriculture and Forestry, Central Research Institute of Food and Feed Control). Muffins were analyzed according to ranking test (ISO 8587, 2006), for all the specified characteristics including crust and crumb colors, odor, taste, softness/hardness, moistness/dryness, elasticity, crumbliness, volume and general preference ranking 1 for the best liked product to 3 to least liked product. Ranking tests were performed in 3 sessions. They have ranked the muffin samples having same amount of GSF in muffins W, S and OAT in a session.

H. Statistical analysis

Three independent experiments were made to get data and described as mean ± SD for total phenolic and total flavonoid contents, total antioxidant capacities, phenolic profiles measured using HPLC-PDA method. For multiple comparisons, data were subjected to statistical analysis using IBM SPSS software 9 (version 25.0; SPSS Inc., Chicago, IL, USA) for the analysis of variance (ANOVA). Duncan’s new multiple range test was used to analyze differences between treatments (p < 0.05) after verifying normal distribution. Sensory analysis results using ranking test method were also analyzed using Friedman’s tests (p < 0.05) between samples (ISO 8587, 2006).

III. RESULTS AND DISCUSSION

A. Total flavonoid content

Total flavonoid contents of 9 muffins were given as mg quercetin equivalent (QE) / 100 g (Table 2) and statistically significant (p < 0.05) differences between samples were detected. Total flavonoid contents of samples were ranged from 110.00±14.49 to 353.26±13.04 mg QE / 100 g. OAT15 muffin has the highest total flavonoid content (353.26±13,04 mg QE / 100 g). Besides, W muffin has the lowest total flavonoid content (110.00±14.49 mg QE / 100 g).

The total flavonoid content of OAT15 muffin was found to be about 20% higher than W15. It was also found out that the total flavonoid amount of muffins were improved by fortification with grape seed flour. The total flavonoid contents were increased about 79% and %160 in W muffins, 47% and 99% in S muffins and 47% and 156% in OAT muffins by fortification of 7.5% and 15% grape seed flour, respectively.

B. Total antioxidant capacity

Total antioxidant capacities of muffin formulations showed statistically significant differences (p < 0.05). Total antioxidant capacities of muffins were observed in a range of 165.77±6.92 - 257.15±10.89 mg TEAC/100 g using CUPRAC method (Table 2). Relative to other samples, the highest TAC values were reached in oat muffin enriched with 15% of grape seed flour (257.15±10.89 mg TEAC/100 g). Besides, the values obtained from whole wheat muffin (65.77±6.92 mg TEAC/100 g) were determined to be the significantly lowest relative to other formulations. In addition, when all the formulations of 15% grape seed flour enriched muffins were compared, the muffin produced using oat flour showed 2% and 16% higher antioxidant capacity than the muffins with siyez wheat flour and wheat flour, respectively. different than W15.

Total antioxidant capacities of muffins prepared with three varieties of flours used including wheat, siyez wheat and oat flours muffins showed statistically significant differences (p < 0.05). Moreover, total antioxidant capacities of samples S15 and OAT15 showed no statistically significant differences, but they showed difference from W15. It was also found out that the total antioxidant capacity contents of muffins were improved significantly by addition of grape seed flour. The TAC measured using CUPRAC method of W muffins were improved by 14% and 33%; S muffins were improved by 20% and 26%; OAT muffins were improved by 4% and 14% by fortification with 7.5% and 15% grape seed flour, respectively.

According to the results the TAC amounts of muffins enriched with grape seed flour reached significantly higher values. Besides, the flours used have an impact on total antioxidant activity, as oat flour have the greatest activity, followed by siyez wheat and finally wheat flour.

In accordance, Peng et al. (2010) studied the antioxidant activity change in breads formulated with grape seed extract. The results showed that bread with grape seed extract had stronger antioxidant activity than that of control and increasing the level of grape seed extract further enhanced their antioxidant capacity. Rosales Soto et al. (2011) have studied the effect of addition of grape seed powder in noodles, pancakes and cereal bars and found out that the highest total antioxidant capacity was obtained in pancakes containing Cabernet Sauvignon GSF (25% and 30%), noodles containing Cabernet Sauvignon GSF (20%) and cereal bars containing Merlot GSF (5%).

Furthermore, Aksoylu et al. (2015) studied the total phenolic content and total antioxidant amounts of biscuits prepared by using 5% of grape seed flour. They found that total phenolic content was doubled and total antioxidant capacity was 30 times higher in comparison to the control (Aksoylu et al., 2015). Additionally, in a recent study of Valkova et al. (2021), they have observed that fortification of bread with 1% grape seed micro powder (GSMP) led to significantly (p < 0.05) higher total phenolic content (1.44 ± 0.17 g/kg expressed as gallic acid equivalents), total flavonoid content (1.04±.04 g/kg expressed as caffeic acid equivalents) and stronger antioxidant capacity (2.02±0.06 g/kg expressed as Trolox equivalents capacity) as compared to the control one (0.97±1.44 g/kg, 0.60±1.04 g/kg and 1.72±0.08 g/kg, respectively). Moreover, Antonic et al. (2021) enriched waffle with grape seed flour in concentrations of 1, 3, 5 and 10%. They observed that total antioxidant capacity was enhanced by using grape seed flour compared to the control and the maximum value was obtained with high ratio of grape seed flour addition (Antonic et al., 2021).

C. Analysis of individual phenolics using HPLC/PDA

Individual phenolic compounds identified and measured were given in Table 3. 10 phenolic compounds were identified and quantified using HPLC/PDA method including o-coumaric acid, caffeic acid, gallic acid, phlorizin, kaempherol, trans-resveratrol, (-)-epicatechin, t-cinnamic acid, (+)-catechin and epigallocatechin gallate. There were statistically significant differences between gallic acid, caffeic acid, phlorizin, kaempherol, trans-resveratrol, t-cinnamic acid and (+)-catechin contents between muffin samples. It was observed the kaempherol contents were increased with increasing amounts of GSF, whereas no kaempherol was detected in W, S and OAT muffins with no GSF. The highest kaempherol content (10.79±0,25) was observed in OAT15 muffin. The highest gallic acid, caffeic acid, phlorizin, trans-resveratrol and t-cinnamic acid contents were found in OAT muffins with GSF. Irakli et al. (2012) found that total content of free and bound phenolic acid levels of oat was higher than corn, barley, rye, triticale and wheat in accordance with this study. However, the individual phenolic contents including caffeic acid, gallic acid, trans-resveratrol, t-cinnamic acid and catechin levels were decreased by increasing amounts of GSF. Similar reduction was observed in total phenolic content of coffee beverages when prepared with milk (Quan et al., 2020; Niseteo et al., 2012). The reason may be due to the interactions of the phenolic compounds with the proteins, carbohydrates, vitamins, or other compounds present. It was reported that phenolic compounds may bind to the proteins, result in a formation of more complex compounds as polyphenol–protein complexes through covalent or noncovalent interactions, and may cause the reduction in identified phenolic compounds (Quan et al., 2020; Ozdal et al., 2013; Niseteo et al., 2012). The phenomena of polyphenol–protein interactions can be either multi-position (many polyphenols bound to one protein), or multi-dentate interactions (one polyphenol bound on multiple sites of one or many proteins). Both two interactions make possible protein precipitation and thus may limit the reaction among the bound polyphenols and the free oxidants (Niseteo et al., 2012). Peng et al. (2015) concluded that cooking process in bread might lower the antioxidant capacity of grape seed extract (GSE) due to reactions of GSE proanthocyanidins with food components, like proteins or starch and generate large molecules. On the other hand, heating might trigger GSE proanthocyanidins to degrade, and consequently lowered antioxidant amount. Reduction in phenolic compounds can also be explained with another alternative situation that damaging of the cellular form frees phenolics, may result in the delivery of some endogenous enzymes for example cytoplasmic polyphenol oxidase, thus can cause oxidative damage of polyphenols (Quan et al., 2020).

D. Sensory analysis

The results of ranking sums of all muffins samples were given in Table 4 and Friedman test analysis results were in Table 5. According to the ranking test results performed using Friedman test, F values higher than critical F values (F) given in Table 4 of ISO 8587:2006 and showed statistically significant differences. F critical value according to ISO 8587:2006 was 5.99 (ɑ=0.05) and F values determined according to ranking sums were compared with this critical F value. F value was higher

than F critical value only for crust color, odor, and crumbliness of 15% GSF containing muffins (Fig. 1). Therefore, muffins of W, S and OAT prepared with 15% GSF were found to be statistically different (p < 0.05) from each other in terms of crust color, odor, and crumbliness characteristics. As a result of ranking test results, W muffin including 15% GSF were mostly liked, following with S including 15% GSF and OAT muffins including 15% GSF were least liked according to crust color, odor, and crumbliness characteristics. However, there are no statistically significant differences (p>0.05) in preference of muffins including sensory attributes of crumb color, softness, taste, elasticity, moistness, volume, porosity, and general preference between muffins having different amounts of GSF according to ranking test method. Additionally, there have been found no statistically significant differences between W, S and OAT muffins in all sensory attributes as well as the formulations enriched with 7.5% GSF.

In the study of Antonic et al. (2021) they have observed that enrichment of waffles with grape seed flour in concentrations of 1, 3, 5 and 10%, had no significant effect on overall impression or the predictable price value for all samples, although apparent variations were noted by the panelists in their color, consistency, and sweetness. Furthermore, Samohvalova et al. (2016) studied the effects on sensory profile of biscuits enriched with grape seed flour and found that taste and flavor of butter biscuits formulated with 10, 15 and 20% of grape seed flour was not significantly changed.

Considering the results obtained from this study and literature, it was seen that use of grape seed flour had a valuable effect on antioxidant capacity of the enriched product. There is no negative affect on the general sensory preference if the product formulation is balanced with amount used and functional food products with enhanced grape seed flour is preferred among the consumers.

III. CONCLUSION

In this study, GSF, which is known to be a valuable source of bioactive components but has a low economic value and is a waste material, was used in fortification of muffins for nutritional improvement. Results showed that total flavonoid content and total antioxidant capacity of the muffins increased significantly (p<0.05) in GSF blended muffins because of the biologically active phenolic compounds of GSF. Moreover, ten phenolic compounds, including o-coumaric acid, caffeic acid, gallic acid, phylorizine, kaempherol, trans-resveratrol, (-)-epicatechin, t-cinnamic acid, (+)-catechin, and epicatechin gallate, were identified and quantified in fortified muffins. According to the results of the ranking test, the W muffins with 15% GSF was more preferred depending on the crust color, odor, and crumbliness characteristics, followed S muffins with 15% GSF but OAT muffin with 15% GSF was the least liked. However, no differences were found in preference of three muffins including sensory attributes of taste, crumb color, moistness, softness elasticity, volume, porosity, and general preference at 15% GSF fortification level. In conclusion, functional muffins could be prepared by using 15% level GSF in the recipes without adverse effect on sensory quality. Muffin can be a functional food and would have a “clean” label with cost effective advantage with 15% GSF addition and provide significant increase in total flavonoid content as well as antioxidant capacity.

ACKNOWLEDGEMENT

This is a multidisciplinary MSc. thesis belonging to Elif Yalcin with advisor Ilkay Gok and co-advisor Tugba Ozdal supported by Istanbul Okan University.

CONFLICT OF INTEREST

The authors have declared no conflicts of interest for the article.

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Received: November 22, 2021

Sent to Subject Editor: November 30, 2021

Accepted: January 1, 2022

Recommended by Subject Editor Sebastián Collins