Quality assessment of nutri-cereal bran rich fraction enriched buns and muffins

Abstract

Millet bran, a by-product obtained during millet processing is rich in nutrients, fiber, antioxidants and phyto-nutrients, but remains underutilized. Consumption of bakery products have increased significantly among all age groups. Majority of the bakery products are calorie dense and lack nutrients. There are limited studies on utilization of minor millet brans and bran rich fractions (BRF) in development of bakery products. Thus, present study aimed at formulating designer buns and muffins using foxtail and kodo millet BRF respectively. It was observed that buns prepared with 20% foxtail and muffins prepared with 30% kodo BRF showed better acceptability. The nutritional profile of BRF enriched buns and muffins had significant increase in dietary fibre (2.73% and 2.79%), iron, calcium, zinc, antioxidant capacity and phytonutrient content. A reduction was observed in the available carbohydrates in both buns (51.11–47.85 g/100 g) and muffins (46.76–43.87 g/100 g). Buns and muffin exhibited moderate glycemic index (57.71, 56.42) and glycemic load (19.32, 14.85) respectively. Shelf life of buns and muffins was 3 and 7 days respectively at room temperature. In both the products moisture, water activity and microbial plate count increased during storage whereas sensory acceptability decreased. The study indicates that addition of minor millet BRF in baked products enhanced nutritional content and reduced glycemic index thereby exhibiting its potential as a functional ingredient in food processing.

Introduction

Significant boost in consumption trend of bakery products like biscuits, breads, cakes, buns and muffins have been witnessed globally with Indian bakery market having value of US$ 9626 Million in 2020 that is forecasted to rise by 2021–2026 at 10.8% compound annual growth rate (IMARC report, available at https://www.imarcgroup.com/indian-bakery-market accessed on 18 July 2021). Muffins and buns are especially becoming popular amongst all age groups due to their convenience, accessibility, palatability and texture. The bakery products are conventionally prepared using refined wheat flour, fat and sugar making them calorie-dense or energy rich, but devoid of certain nutrients, minerals and fibre (Lebesi and Tzia 2011; Heo et al. 2019). Life style changes, excess and frequent consumption of calorie-dense foods are also associated with various health issues like obesity and its related disorders, micronutrient deficiencies and diabetes. Thus, promoting healthy snacking, by improving nutrient density of such calorie dense foods is essential. The increased consumption of these bakery products favors its utilization for fortification (Lebesi and Tzia 2011; Patel 2015). This, coupled with rising health consciousness amongst consumers has paved way for researchers and food industries to formulate nutri-dense and functional products. Various functional ingredients like cereal/millet brans, vegetable and fruit pomace are exploited to enhance nutritional value of bakery products by partly replacing refined wheat flour (Jisha et al. 2010; Mildner-Szkudlarz et al. 2016; Kaur et al. 2017; Heo et al. 2019).

Bran, an outer layer of cereal/millet grains and bran-rich fractions (aleurone layer, testa, pericarp) are usually discarded during primary processes like dehulling, debranning, milling, polishing to improve edibility and palatability of grains (Saleh et al. 2013; Patel 2015). Many studies have depicted that good amount of fibre, minerals, vitamins, antioxidants, and phytonutrients are concentrated in bran and its removal decreases nutritional content of grains. Bran and BRF due to their health promoting fibre, antioxidant, phytochemical content can be used as functional ingredient in preventing or controlling various aliments like constipation, obesity, diabetes, hyperlipidaemia etc. (Dykes and Rooney 2007; Patel 2015). Thus, value-addition of bakery products with bran has captured interest of researchers as it not only helps in utilization of cereal/millet processing by-products but also enhances fibre and nutrient content. Although brans are utilized as functional ingredient in bakery industry only cereal brans like rice, wheat, oat, brans are popular whereas, millet brans and BRF still remain underutilized though they have comparable nutrient profile. Millet grains themselves are being termed as ‘nutri-cereals’ as they confer lots of health benefits due to their rich protein, amino acid, fats, dietary fibre, minerals, phytonutrient and phenolic compounds contributing to antioxidant capacity. Similarly, bran and BRF obtained as result of millet processing are also rich in the same.

Minor millets viz. foxtail, kodo, barnyard, proso are further acquiring consumers attention due to their nutrient profile. Dehulling or dehusking of these millets can be tedious and difficult on account of limited accessibility to high-end fabricated dehullers and their small grain size thus, major portion of seed can be lost during processing resulting in loss of more nutrients (Suma and Urooj, 2012). Considering all these factors and limited studies on utilization of minor millet bran and bran rich fractions (BRF), present study was conducted to evaluate nutritional profile, glycemic index and shelf life of designer buns and muffins formulated incorporating foxtail and kodo millet BRF.

Material and methods

Procurement of raw material and sample preparation

Minor millets viz. kodo (Paspalum scrobiculatum) and foxtail (Setaria italica) were procured from local vendors, dehulled using stone abrasive mini dehuller (Gurunanak Engineering, Hyderabad) for 35 and 30 min respectively to obtain bran rich fractions (true bran + broken grain + husk). It was further ground, sieved (60 mesh) and stabilized using microwave heating (900 W for 2.5 min) based on the preliminary studies conducted and literature survey. Stabilisation was done to improve its shelf life. Stabilised BRF samples were then packed in airtight containers and stored at − 20 °C till further use. All the other ingredients required were purchased from local market of Hyderabad.

Formulation of muffins and buns

Flour mix was developed by incorporating foxtail (F) and kodo (K) BRF at 0, 10, 15, 20, 25 and 30% in refined wheat flour. This flour was further used in preparation of muffins and buns. Six variations (0, 10, 15, 20, 25, 30%) of muffins and buns were prepared using a standard recipe with slight modifications described by Heo et al. (2019) and Arora and Saini (2016) respectively.

Functional properties of flour

The flour mix was analysed for its functional properties i.e. water, oil absorption and foaming capacity (Chandra et al. 2015).

Production of buns and muffins

The muffin flour was mixed with baking powder, salt; sifted (thrice) then added to creamed oil, sugar and egg. This mixture was creamed again till it became light and fluffy, followed by filling in greased muffin tray and baking at 180 °C for 25 min in a preheated oven. For preparing buns, firstly active dry yeast was mixed with lukewarm water and was used to knead the dough. The dough was proofed for 1 h, till it became double its volume, further it was divided into round equal balls and baked at 180 °C for 25 min in a preheated oven. Both muffins and buns prepared using refined flour without addition of BRF were considered as control.

Sensory evaluation

Products were evaluated for parameters viz., appearance, color, texture, flavor, taste and overall acceptability by 21 semi-trained panelists using 9-point hedonic scale (Peryam and Pilgrim, 1957) to select best accepted muffins and buns. The panelists were oriented about the study objectives and written consent was obtained from all the semi-trained panel members before presenting the samples for evaluation.

Nutrient analysis

Both control and best accepted muffins (K30) and buns (F20) were analyzed for moisture (IS:1155—1968 reaffirmed 2010), protein (AOAC 2010:954.01), fat (AOAC 2007: 922.06), total dietary fibre (AOAC 2010: 985.29) and total ash (IS:1155—1968 reaffirmed 2010). Total and available carbohydrate content were calculated ‘by difference’ method where dietary fibre was subtracted to get available carbohydrate content. Energy (Kcal/100 g) was calculated for all the samples as [Protein (g) × 4] + [Carbohydrate (g) × 4] + [Fat (g) × 9]. Minerals viz., iron, calcium and zinc were estimated using Atomic Absorption Spectrophotometry (AOAC, 1990: 975.03) whereas sodium and potassium using Flame Photometry (AOAC, 1990: 956.01).

Antioxidant and phytonutrients analysis

Phytonutrients viz. Total polyphenols (TP), Phytic acid were analyzed and antioxidant activity was estimated using DPPH (1,1-diphenyl-2-picrylhydrazyl), FRAP (Ferric reducing antioxidant power) and TBARS (Thiobarbituric acid reactive substances) protocols.

Sample extraction

All samples were extracted using 80% acidified methanol (pH 2.0), where 1 g accurately weighed sample was extracted thrice using methanol (15 ml each time) by continuous shaking (155 rpm) at room temperature for 30 min. Supernatants collected from all 3 times were centrifuged (6000 rpm) for 15 min, filtered (Whatman No. 1) and volume was made to 50 ml using solvent. This extract was used to determine TP, DPPH and FRAP activity.

Total polyphenol (TP)

The Folin–Ciocalteu (FC) method as described by Sadasivam and Manickam (2007) was used with slight modifications. Briefly, to 0.1 ml aliquot, 0.5 ml of diluted FC reagent (1:1, v/v) 10 ml of (7.5%) sodium carbonate was added and incubated at 37 °C for 60 min. Absorbance was measured at 765 nm (Shimadzu UV spectrophotometer, Japan Model: UV-1800). Gallic acid standard curve (5–35 µg) was prepared (y = 0.0133x − 0.0019; R² = 0.9965) and TP was expressed as mg gallic acid equivalent (GAE)/100 g of sample.

Phytic acid (PA)

Standard protocol as described by Sadasivam and Manickam (2007) was followed.

DPPH radical scavenging activity

DPPH radical scavenging activity was estimated using protocol described by Blois (1958) with slight modification. Briefly; to 0.1 ml aliquot, 3 ml methanolic solution of DPPH (1 Mm) was added, incubated in dark (37 °C for 20 min) and absorbance was measured at 517 nm (Shimadzu UV spectrophotometer, Japan Model: UV-1800). Methanol (1 ml) was used as control and Trolox to obtain standard curve (Conc. 5–35 µg, y = − 0.0174x + 0.6176; R² = 0.9679). The results were expressed as percentage DPPH scavenging activity relative to control.

$$\text{DPPH}\text{scavenging}\text{activity}\left(\%\right)=\frac{\text{Control}\text{absorbance - Sample}\text{absorbance}}{\text{Control}\text{absorbance}}\times 100$$

Ferric reducing antioxidant power (FRAP)

As described by Benzie and Strain (1999) standard protocol was followed with slight modifications. Acetate buffer, 2,4,6-tripyridyl-S-triaizine (TPTZ) and FeCl₃ in 10:1:1 proportion to prepare FRAP reagent. In a test tube standards/sample aliquot were mixed with distilled water (3 ml), FRAP reagent (1.8 ml) and incubated for 4 min at 37 °C further read at 593 nm (Shimadzu UV spectrophotometer, Japan Model: UV-1800). FRAP reagent with distilled water was used as blank. Trolox was used for preparing standard curve (y = 0.3057x + 0.0117; R² = 0.9689) was expressed as µM/g.

$$\text{FRAP}\left(\mathrm{\mu }\text{M/g}\right)=\frac{\text{Absorbance}\text{of}\text{sample}}{\text{Absorbance}\text{of}\text{standard}}\times 1000$$

TBARS Assay

TBARS protocol as described by Zeb and Ullah (2016) with slight modification was followed. Sample (1 g) was extracted with 100% glacial acetic acid (5 ml) by continuous agitation for 1 h followed by filtering (Whatman No1 filter paper). For TBARS estimation sample aliquot (2 ml) was mixed with TBA reagent (2 ml), incubated in boiling water bath (95 °C) for 60 min and read at 532 nm (Shimadzu UV spectrophotometer, Japan Model: UV-1800). From 1 mM Malondialdehyde (MDA) stock solution working standards (0.1, 0.2, 0.4, 0.6, 0.8 and 1.0 mM) were prepared to obtain standard curve (y = 0.3204x − 0.1118 R² = 0.997). TBARS was calculated and expressed as µM/g of the sample:

$$\text{TBARS}\left(\mathrm{\mu }\text{M/g}\right)=\frac{\text{Ac}\times \text{V}}{\text{W}}\times 100$$

where Ac is amount determined from calibration curve, W is weight of sample taken and V is volume in ml of the total extract prepared.

Assessment of glycemic index (GI) and glycemic load (GL)

Ethical committee approval

Approval and clearance of institutional ethical committee was obtained before initiation of study (Project No2./IEC/PJTSAU/AICRP-PGRC/HHD/17-05 dated 13-01-2020).

Subject selection

Ten normal healthy individuals (19–22 years age) were recruited after briefing them with aim of study, protocols to be used and obtaining their written consent. The subjects were screened from a pool of 20 participants after conducting Oral Glucose Tolerance Test (OGTT) in Health Centre, PJTSAU to check for any abnormalities in glucose tolerance. For OGTT each participant was given glass of water containing 75 g of glucose and blood glucose levels were assessed at fasting, 60, and 120 min. Subjects were eliminated if they had abnormal glucose values (between 140 and 200 mg/dL) after 2 h of consumption. Subjects with gastrointestinal disorder, allergic/intolerant to any food, prescribed on heavy medication were also excluded. Those subjects who felt any discomfort during the study were either eliminated or allowed to withdraw.

Glycemic index (GI) and glycemic load (GL)

Best accepted muffins and buns enriched with minor millet BRF were assessed for GI and GL using protocol described by Aston et al. (2008). Portion size of test and reference food was calculated such that each serving provides 25 g of available carbohydrate. Amount of 25 g available carbohydrate was selected to avoid large and uncomfortable portion size of test foods to be consumed by subjects. For reference food participants were given 25 g of glucose in 1 glass of water, this was repeated for 3 consecutive days. A washout period of 4 days was maintained between each test foods. After 4 days washout period serving portion of test food providing 25 g available carbohydrate was calculated and given to same subjects. Subjects were asked to consume the reference/test food within 15 min. Consumption of heavy meals, rigorous exercise was avoided and overnight fasting (10–12 h) was maintained by subjects before consumption of reference/test food. Finger prick test using glucometer (AccuSure simple, Model No. TD: 4183, Manufactured by Taidoc Technology Corporation, Taiwan) was used to take reading at fasting, 15, 30, 60, 90 and 120 min after the consumption of reference/test food. Experiment was conducted thrice for minimizing the errors. Incremental area under curve (IAUC) was calculated using GI was calculated with the following formula:

$$\text{GI}=\frac{\text{IAUC}\text{for}\text{test}\text{food}}{\text{IAUC}\text{for}\text{reference food}}\times 100$$

Glycemic load (GL) was calculated using following formula

$$\text{GL}=\frac{\text{Dietary}\text{carbohydrate}\text{content}\text{of}\text{serving}\text{measured}\text{in}\text{grams}\times \text{GI}}{100}$$

Shelf life study

Muffins and buns were stored in air tight container at room temperature and evaluated during storage (1st, 3rd and 7th day) for moisture, water activity and sensory parameters. Microbial plate count for total bacterial count (TBC), total mold count (TMC) using Nutrient agar and Rose Bengal agar respectively were also determined during storage using standard protocol for pour plate method (FSSAI 2012).

Statistical analysis

All experiments were conducted in triplicates and values were reported as mean scores. One-way analysis of variance for functional properties of flour, nutrient composition and sensory evaluation of products, two-factorial design for storage studies was performed using INDOSTAT (version 9.1) and Microsoft excel. Significant difference was noted based on CD (critical difference) values.

Results and discussion

Functional properties of flour mixed with minor millet BRF

Functional properties like water, oil absorption and foaming capacity of flour affect overall texture and sensorial acceptability of product. Water absorption and foaming capacity affect the final texture of product while oil absorption contributes to flavor and mouth feel (Egbedike et al. 2016). In the present study it was observed that addition of foxtail (F) and kodo (K) BRF significantly increased (p < 0.05) the water absorption of flour from 209.20 g/100 g in control (CFR) i.e. refined wheat flour to 245.74 g/100 g and 248.18 g/100 g in F30 and K30 respectively (Table 1). No significant difference was observed between F30 and K30. Also, results depicted that water absorption increased with increasing BRF proportion. In contrast to this, inverse relation was observed between water solubility of the flour mix which reduced from 7.41% in CFR to 6.56% and 5.54% in flour mix with kodo and foxtail millet BRF respectively (Table 1). Similarly, a decreasing trend was observed in oil absorption (from 246.70 (CFR) to 220.32 and 233.01 in F30 and K30 respectively) and foaming capacity (from 19.33% in CFR to 10.26 and 11.33 in F30, K30 respectively) of the flour mix. This significant increase in water absorption and reduction in water solubility, oil absorption and foaming capacity after the incorporation of BRF can be attributed to the presence of high fibre, their protein and fat composition (Sairam et al. 2011). These results are in accordance with studies conducted by El-Sharnouby et al. (2012) and Egbedike et al. (2016).

Table 1.

Water absorption capacity (WAC), water solubility index (WSI), oil absorption capacity (OAC) and foaming capacity (FC) of flour mixed with minor millet BRF

Millet BRF	WAC (g/100 g)	WSI (%)	OAC (g/100 g)	FC (%)
CFR	209.20a	7.41 g	246.70NS	19.33c
F10	217.31b	6.30bcd	227.76NS	16.00b
F15	232.89c	6.25bcd	225.09NS	12.67ab
F20	230.73c	6.24bc	223.19NS	11.70a
F25	231.43c	5.94ab	221.68NS	11.27a
F30	245.74e	5.54a	220.32NS	10.26a
K10	222.94c	7.36g	237.42NS	16.00b
K15	228.29c	7.27fg	234.85NS	14.67b
K20	235.70cd	6.91efg	234.40NS	13.33ab
K25	247.56e	6.79def	233.95NS	12.00ab
K30	248.18e	6.56cde	233.01NS	11.33a
SEm ±	1.922	0.186	5.532	1.069

BRF bran rich fractions, CFR control flour, F foxtail BRF, K kodo BRF, 10, 15, 20, 25, 30: percent incorporation. Means represented within same column having different alphabet show statistically significant difference at 5%. NS indicates no significant difference

Sensory evaluation

Results of both buns and muffins revealed that all products were acceptable up to 30% BRF incorporation as the scores ranged between 6 and 8 (liked slightly—liked moderately), although there was a slight reduction in sensory scores as percentage of BRF increased. No significant difference (p > 0.05) was noted in overall acceptability amongst all muffins (K0–K30) thus K30 with highest BRF content was selected as best accepted product. In terms of overall acceptability of foxtail buns (F0–F30), control (F0) significantly scored highest (8.14) followed by F10 (7.52), F15 (7.19), F20 (7.14), whereas, F25 (6.71) and F30 (6.67) comparatively scored low. F10, F15 and F20 scored above 7 (Like moderately) and showed no significant difference (Table 2). Thus, in case of buns, F20 having highest BRF percentage was considered as best accepted product. Slight reduction in sensory scores for muffins and buns developed with BRF could be due to the granular/grainy texture and husky/sandy taste imparted by bran (Lebesi and Tzia 2011). Overall, it was observed that BRF incorporation was acceptable up to 30% in muffins and 20% in buns. These results show slightly higher percent of kodo BRF in muffin was acceptable compared to previously available literature where up to 15–24% cereal or millet bran was acceptable (Romjaun and Prakash 2013; Nazni and Karuna 2016), whereas for foxtail BRF buns the results are in accordance with previous studies where breads with 20% bran incorporation was found best (Saccotelli et al. 2017; Ahmad et al. 2018).

Table 2.

Mean sensory scores for muffins and buns prepared using flour mixed with minor millet BRF

Variations	Appearance	Colour	Texture	Flavour	Taste	Overall acceptability
Muffins
K0	7.81NS	8.10b	7.71NS	7.52NS	7.52NS	7.71NS
K10	7.62NS	7.57ab	7.33NS	7.43NS	7.62NS	7.57NS
K15	7.86NS	8.10b	7.48NS	7.52NS	7.71NS	7.81NS
K20	7.71NS	7.67ab	7.38NS	7.43NS	7.48NS	7.57NS
K25	7.71NS	7.67ab	7.38NS	7.24NS	7.62NS	7.43NS
K30	7.71NS	7.38a	7.33NS	7.05NS	7.33NS	7.33NS
SEm ±	0.198	0.213	0.249	0.253	0.266	0.225
Buns
F0	8.19c	8.10c	8.14d	7.90c	8.00c	8.14c
F10	7.57b	7.48b	7.52c	7.14b	7.33bc	7.52bc
F15	7.43ab	7.10ab	7.19bc	6.81ab	6.86ab	7.19ab
F20	7.29ab	7.24b	7.00abc	7.05b	7.10ab	7.14ab
F25	7.24ab	7.19b	6.71ab	6.62ab	6.62a	6.71a
F30	6.90a	6.62a	6.48a	6.14a	6.48a	6.67a
SEm ±	0.203	0.186	0.221	0.258	0.251	0.222

F foxtail BRF bun, K kodo BRF muffin; 0, 10, 15, 20, 25, 30: percent BRF incorporation. Means represented within same column having different alphabet show statistically significant difference at 5%. NS indicates no significant difference

Nutritional composition

Nutritional composition of buns (F0 and F20) and muffins (K0 and K30) are presented in Table 3. Moisture content ranged from 24.95 ± 0.197 (F0) to 24.84 ± 1.271 (F20) in buns and from 25.08 ± 1.588 (K0) to 25.40 ± 0.563 (K30) in muffins with no significant difference. In buns addition of foxtail BRF increased the protein content by 20% whereas, only 1% increase was observed in muffin after kodo BRF incorporation. Ash content also increased in bun (F10) and muffin (K30) by 25.76% and 31.70% respectively. It was observed that addition of BRF significantly increased total dietary fibre (TDF) thereby resulting in reduction of total and available carbohydrate content. K30 showed 272% increase, whereas F20 showed 268.92% increase in TDF respectively. There was reduction of 2.47% and 6.38% in total and available CHO respectively in buns, while in muffins it was 1.77% and 6.18% respectively. Reduction in carbohydrate on addition of BRF can be associated to its increased fibre content. Similar results for increased protein, ash, fibre content in products developed with bran incorporation were reported by several researchers (Jisha et al. 2010; Sairam et al. 2011; El-Sharnouby et al. 2012). Addition of BRF made both products significantly (p < 0.05) superior to control in terms of minerals like iron, zinc, calcium and sodium. Iron content of F20 and K30 is more than 1/3rd of the daily requirements suggested for Indian adults. Thus, it was observed that value-addition of BRF resulted in product with better nutrient profile, providing healthy substitute for empty calorie bakery snacks.

Table 3.

Nutritional, antioxidant and antinutrient composition of designer products prepared using flour mixed with minor millet BRF

Parameter	Bun		Muffin
	F 0	F 20	K 0	K 30
Moisture (g/100 g)	24.95 ± 0.197NS	24.84 ± 1.271NS	25.08 ± 1.588NS	25.40 ± 0.563NS
Protein (g/100 g)	5.65 ± 1.157NS	6.83 ± 0.804NS	6.96 ± 0.111NS	7.03 ± 0.303NS
Fat (g/100 g)	15.92 ± 1.138NS	15.71 ± 2.013NS	19.22 ± 0.123NS	19.29 ± 0.697NS
Ash (g/100 g)	1.63 ± 0.995NS	2.05 ± 0.048 NS	1.23 ± 0.0311	1.62 ± 0.0052
TDF (%)	0.74 ± 0.009a	2.73 ± 0.042b	0.75 ± 0.0071	2.79 ± 0.0142
T. CHO (g) *	51.85 ± 0.994NS	50.57 ± 2.191NS	47.50 ± 1.795NS	46.66 ± 0.952NS
A. CHO (g/100 g) *	51.11 ± 0.986NS	47.85 ± 2.209NS	46.76 ± 1.799NS	43.87 ± 0.937NS
Energy (Kcal)*	373.31 ± 10.067NS	371.01 ± 8.722NS	390.84 ± 6.189NS	388.36 ± 1.938NS
Minerals
Iron (mg/100 g)	1.22 ± 0.090a	13.83 ± 0.657b	1.51 ± 0.0531	7.86 ± 0.2132
Zinc (mg/100 g)	3.73 ± 0.208a	4.53 ± 0.187b	0.79 ± 0.0191	0.85 ± 0.0042
Calcium (mg/100 g)	15.59 ± 0.209a	23.90 ± 1.446a	34.68 ± 0.3711	40.68 ± 0.4632
Potassium (mg/100 g)	67.49 ± 0.111b	55.52 ± 0.256a	76.08 ± 0.8082	65.01 ± 1.1111
Sodium (mg/100 g)	34.19 ± 0.216b	45.60 ± 0.511a	31.68 ± 0.0901	35.98 ± 0.4512

Parameter	F 0	F 20	K 0	K 30
Antioxidant and antinutrients
DPPH (%)	7.06 ± 0.692a	19.17 ± 0.000a	11.98 ± 0.9231	25.97 ± 2.5372
FRAP (µM/g)	229.00 ± 3.464a	894.33 ± 9.238b	100.67 ± 5.7741	861.67 ± 11.5902
TBARS (µM/g)	1.19 ± 0.077b	0.85 ± 0.020a	1.81 ± 0.1062	1.29 ± 0.0491
TP (mg GAE/100 g)	152.53 ± 4.272a	319.77 ± 8.025b	224.80 ± 13.6831	402.40 ± 12.4712
PA (mg /100 g)	599.67 ± 6.110a	792.67 ± 6.526b	488.76 ± 8.681	650.00 ± 8.6602

F0: control bun, F20: 20 percent foxtail BRF bun; K0: control muffin, K30: 30 percent kodo BRF muffin; Values are expressed as Mean ± Standard deviation; *calculated value; When compared between buns means represented within same row having different alphabet as superscripts show statistically significant difference at 5%; Similarly, when compared between muffins different means represented within same row having different numbers as superscripts show statistically significant difference at 5%. NS indicates no significant difference

Bran, bran rich fractions and extracts derived from kodo and foxtail millet have shown to possess good antioxidant profile (Bijalwan et al. 2016). Bran also contains phytonutrients in the form of phenol and phytic acid, that contributes to antioxidant activity. In present study BRF incorporation in products (F20, K30) significantly increased antioxidant activity from their controls (F0, K0). These antioxidants contribute in prevention of various degenerative diseases caused by oxidative stress. TP contributing to antioxidant activity in present study showed percentage increase of 109.64% and 79.00% in F20 and K30 respectively. Inhibition of DPPH (%) increased from 7.06 ± 0.692 (F0) to 19.17 ± 0.000 (F20) in buns and 11.98 ± 0.923 (K0) to 25.97 ± 2.537 (K30) in muffins. FRAP assay also depicted that supplementation of BRF increased the antioxidant capacity of products. Higher the phenolic content, higher was antioxidant capacity. Phytic acid, a chelating agent responsible for hindering absorption of certain minerals also contributes to antioxidant capacity (Abdulwaliyu et al. 2019). Phytic acid increased from 599.67 ± 6.110 (F0) to 792.67 ± 6.526 (F20) and 488.76 ± 8.68 (K0) to 650.00 ± 8.660 (K30). TBARS values were lower in F20 and K30 thus confirming that they had better antioxidant potential. This could be associated with lower lipid peroxidation and thus reduced production of malondialdehyde (MDA) in BRF enriched products (Zeb and Ullah 2016).

Glycemic index (GI) and glycemic load (GL)

Blood glucose response of buns and muffins are depicted in Fig. 1a and it was observed that rise in blood glucose levels after 30 min of consumption was lowest in muffins, followed by bun and highest increase was observed in reference food (glucose). The GI and GL of bun (F20) and muffin (K30) are depicted in Fig. 1b. It was observed that both muffin and bun fell into intermediate-GI category (> 55– < 70) with GI of 56.42 and 57.71 respectively. The glycemic index is affected by various factors like varietal differences grains used, type and content of starch, sugar, carbohydrate, fat, protein, fiber, phytonutrients like polyphenols, phytates, cooking method and time etc. (Eleazu 2016; Ganesan and Xu 2017). Dietary fibre content in whole grains is associated with hypoglycaemic and hypolipidemic effects. Thus, presence of dietary fiber resulting in reduction of available carbohydrate and presence of TP, PA could be one of the reasons for reduced blood glucose response after consumption of test food (F20, K30) when compared to reference food. Similar report of reduction in peak blood glucose rise was depicted by Tosh et al. (2008) in muffins enriched with oat bran. Glycemic load considers the test food’s portion sizes. In present study 2 muffins (K30) and 1 bun (F20) were considered as 1 serving, with portion size of 60 g, and 70 g respectively. Muffins for 60 g serving showed to have GL of 14.85 and buns for 70 g of serving had GL of 19.32. Both products fell in category of medium GL foods.

Fig. 1.

a Mean Blood Glucose response and b Glycemic index and glycemic load of Foxtail BRF bun (F20) and Kodo BRF muffin (K30)

Shelf life studies

Shelf life of products was tested for one week for both buns and muffins at interval of 1st, 3rd and 7th day storage (Figs. 2, Fig. 3) at room temperature. Parameters like moisture, water activity, microbial plate count and sensory evaluation were analyzed. Visible spoilage was noted on buns on 4th day of storage; thus, the analysis was discontinued for buns after 3rd day of storage. The moisture content, water activity and microbial load increased during storage, whereas the sensory scores decreased. Significant increase (p < 0.05) was noted in moisture levels on 3rd day for buns and 7th day for muffins. Generally, moisture decreases in core during storage, while it increases in crust due to redistribution of moisture. However, the increased moisture in the present result could be associated to the effect of atmospheric temperature and humidity during storage, that might have caused condensation of air into the storage container leading to increase in moisture. However, in depth studies need to be conducted for understanding the effect of storage on the moisture levels during shelf life. Water activity significantly increased from 0.690 (1st day) to 0.797 (7th day) in K0 and 0.691 (1st day) to 0.795 (7th day) in K30. For buns the increase was noted from 0.677 (F0, F20) at day 1 to 0.702, 0.700 (F0, F20) at 3rd day storage. Within the treatments no significant difference was observed amongst moisture and water activity of K0 and K30, whereas moisture content of F0 and F20 differed significantly. Increase in water activity and moisture content can favor the growth of microorganisms. It was observed that TBC and TMC also increased during storage in both buns and muffins but stayed well within limits (FSANZ 2016). Sensory scores decreased with increasing storage period, this can be associated with the change in flavor and taste due to rancid off flavor produced during storage. Decreased sponginess was also one of the reasons for reduced scores during storage. In muffins sensory scores for appearance, color, texture, flavor, and overall acceptability significantly decreased from 1st to 7th day of storage. In buns though there was decrease in sensory scores, no significant difference was observed in the scores till 3^rd day of storage. Similar results for bread and muffins samples stored at room temperature were recorded by Kamaljit et al. (2011) and Romjaun and Prakash (2013).

Fig. 2.

Moisture content (a), water activity (b), total bacterial count (c) total mould count (d) and sensory scores (e) of buns during storage. Note: F0: control bun, F20: 20 percent foxtail BRF bun

Fig. 3.

Moisture content (a), water activity (b), total bacterial count (c) total mould count (d) and sensory scores (e) of muffins during storage. Note: K0: control muffin, K30: 30 percent kodo BRF muffin

Conclusion

The present study demonstrated that foxtail and kodo millet BRF incorporation increased the fiber content of buns and muffins compared to control. Antioxidant activity and phytonutrients in the products were increased with addition of BRF. The nutritional profile of buns and muffins enhanced with value-addition of foxtail and kodo millet BRF. Thus, present study revealed that minor millet BRF can be exploited as potential source of natural nutraceutical and functional ingredient in food industry.

Abbreviations

BRF

Bran rich fractions

CFR

Control flour

F

Foxtail

K

Kodo

Authors' contribution

BMD Conceptualization of research work, conducting the experiments, investigating the results and interpretation, statistical analysis, writing, revising and editing the original draft of manuscript. TVH Conceptualization of research work and administration, supervision of work, interpretation of results, revision and editing the manuscript. AK Contribution as committee member in planning and designing the study experiments, interpretation of results, revising and editing of manuscript. MS Contributed as committee member in planning the study, revising and editing of manuscript. VSR Contributed as committee member in planning the study, revising and editing of manuscript.

Funding

Not applicable.

Declarations

Conflict of interest

The authors declare that they have no conflict of interests.

Ethics approval

Approval and clearance of institutional ethical committee was obtained before initiation of study (Project No2./IEC/PJTSAU/AICRP-PGRC/HHD/17-05 dated 13-01-2020).

Consent to participate

All the participants were oriented about the study objectives and written consent was obtained from all before recruiting them in the study.

Consent for publication

Not applicable.

Availability of data and material

Not applicable.

Code availability

Not applicable.