Development of multigrain premixes—its effect on rheological, textural and micro-structural characteristics of dough and quality of biscuits

Abstract

Four different Multigrain Premixes (MGPs) namely MGP I, MGP II, MGP III, MGP IV were developed to select the best premix for preparation of biscuits based on nutritional value and biscuit quality. The MGPs were prepared using cereals (barley, sorghum, maize, oats), pulses (chickpea dhal, green gram, peas, soya flour), millets (pearl millet, finger millet) and wheat germ each at 20 % level. The MGPs developed had 22.91–27.84 % protein, 16.82–18.72 % dietary fiber and 3.11–3.46 % minerals. The wheat flour was replaced with MGPs separately at different levels of 10, 20, 30, 40 and 50 %. The incorporation of these MGPs significantly (p ≤ 0.05) decreased the water absorption (56.0–50.9 %), peak viscosity (273.67–154.92 RVU), biscuit spread ratio (10.28–8.15) and increased the pasting temperature (67.10–79.20 °C), dough hardness (311.66–460.26 N) and biscuit breaking strength (13.25–28.68 N). SEM studies showed that incorporation of MGP disrupted the protein matrix. Among the MGPs, MGP III was found to be more suitable even at the 40 % level for obtaining nutritious multigrain biscuits with higher protein, dietary fiber, and mineral content.

Introduction

Bakery products have become popular in India as evidenced by two fold increase in their production during the last five years. Among all snack foods, biscuits form the most popular snack item and offer certain advantages such as cheaper than conventional snack items, easy to use during travel or at home, because of their availability in varieties of convenient pack sizes and longer shelf life (Crassina et al. 2012). Though, annual per capita consumption of biscuits is quite low (1.8 kg) as compared to 10–15 kg in developed countries, it has almost doubled from 882 g to 1.8 kg during 1998–2012 (Malhotra and Verma 2015). Total annual production of biscuits both in the organized and unorganized sector is estimated to be around 1.2 million tonnes and the growth rate is around 9 %. Nevertheless, it has been reported that normal biscuits are nutritionally deficient as they are low in protein, dietary fiber as well as vitamins and minerals (Jyotsna et al. 2012; Ritika et al. 2012). Several studies have reported on improving the nutritional quality of biscuits by using protein rich ingredients like oil seed meals (Sridevi and Sarojini 2013), pulses (Jyotsna et al. 2012), industrial by-products like wheat germ (Shivani and Sudha 2011) and milk products (Santiago et al. 2013).

The present day scenario requires exploring the possibility of incorporating novel ingredients in commonly consumed foods rather than developing new products to improve the functional characteristics (Aleem et al. 2012). Recently few studies have been reported on the use of multigrain to improve the nutritional quality of bread and other traditional products. The use of multigrain not only improves the various nutritional parameters, but also reported to improve the quality of protein by mutual supplementation of amino acids (Indrani et al. 2010, 2011).

Some of the grains used in the multigrain premixes are cereals, pulses, oil seeds and millets. The cereals like barley and oats are excellent sources of soluble and insoluble dietary fibers, particularly beta-glucan, which is reported to lower cholesterol levels (Izydorczyk and Dexte 2008). Pulses like chickpea, green gram, and pea are rich sources of protein and essential amino acids like lysine, arginine, leucine, isoleucine which are limiting in other grains (Indrani et al. 2010). Soya is known for its rich protein content with high levels of lysine and other micronutrients (Aleem et al. 2012) whereas, millets like pearl and finger millet are rich in minerals (calcium, iron, zinc and phosphorus) and a good source of dietary fiber (Anuradha et al. 2010). Wheat germ, a by-product of wheat flour milling industries is a rich source of protein, dietary fiber, vitamin E and B-group vitamins (Amado and Arrigoni 1992).

Literature survey has clearly shown that there are no study reported on the use of multigrain in biscuits, which is consumed largely by the various sections of the population, particularly children. Hence there is a need to develop suitable multigrain premix for use in biscuits to improve its nutritional quality. The effects of these premixes on the rheological, textural, micro structural characteristics as well as biscuit making qualities were studied.

Materials and methods

Raw materials

The different grains like barley (Hordeum vulgare L.), Pearl millet (Pennisetum glaucum), maize (Zea mays L.), oats (Avena sativa), sorghum (Sorghum vulgare), finger millet (Eleusine coracana), chickpea (Cicer arietinum), whole green gram (Phaseolus aureus Roxb), whole dry pea (Pisum sativum), commercially available wheat flour, cane sugar, Marvo brand bakery shortening (Bunge India Pvt. Ltd., Mumbai, India), skimmed milk powder (Nandini brand, Karnataka Milk Federation, Mysore, India), vanilla essence (Bush Boake Allen Ltd., Chennai, India) were procured from the local market in Mysore, Karnataka, India. The grains were cleaned and stored individually in an airtight container. Defatted toasted soya flour (Glycine max) was procured from the Sakthi Soya Company, Pollachi, Tamilnadu, India. Wheat (Triticum aestivum) germ was procured from the Yamuna Roller Flour Mills Pvt. Ltd., Thrissur, Kerala, India. The Enzymes like termamyl, pepsin and pancreatin were procured from M/s Sigma Chemical Co., (St. Louis, MO, USA). All other chemicals were of analytical grade.

Preparation of multigrain premixes (MGPs)

All the grains were separately milled in an ultra-centrifugal mill (Retsch ZM 200, Germany) using 200 μm sieve. Wheat germ was roasted using an electric roaster by maintaining the temperature at 130 to 160 °C for about 20 min until it turned to light brown color and cooled prior to milling. Based on preliminary studies, MGPs containing five different grains were selected and combined in the ratio of 1:1, to get maximum benefit of protein and dietary fiber in all the MGPs without adversely affecting the sensory characteristics of biscuits. The compositions of different MGPs are presented in Table 1.

Table 1.

MGP formulations

MGP I	MGP II	MGP III	MGP IV
Finger millet	Pearl millet	Barley	Pearl millet
Oats	Finger millet	Sorghum	Barley
Chickpea	Green gram	Chickpea	Maize
Wheat germ	Oats	Pea	Green gram
Defatted soya	Defatted soya	Defatted soya	Defatted soya

MGP multigrain premix, each ingredient at 20 % level

The soya flour is used in all the mixes as a source of protein. The ingredient like oats, barley are used as a source of dietary fiber and finger millet, pearl millet is used as a source of minerals and dietary fiber in two mixes each to find out the effect of each on the quality of biscuits. The different flours were mixed in a Hobart mixer (Model N50, Hobart GmbH, Offenburg, Germany) for about 10 min and sieved through 200 μm sieve to get homogenous mixture. The MGPs were packed in an airtight container and stored at 4 °C for further use.

Color analysis of MGPs

The color values of different MGPs were measured using a Hunter color meter (Hunter Associates Laboratory, Inc., Reston, Virginia) with standard D65 day light illuminate and 10° view angle. A higher L* value indicates a brighter or whiter sample. The positive a* value indicates redness and the negative a* value indicates greenness. The positive b* value indicates yellowness and the negative b* value indicates blueness. Numerical values of a* and b* were calculated into hue angle (h°) and chroma value (C*) as reported by Nielsen (1998) by using the following formulas and studies were carried out for sample in triplicates.

$${\mathrm{h}}^0={tan}^{-1}\left(\mathrm{b}*/\mathrm{a}*\right);\mathrm{C}*=\sqrt{{\left(\mathrm{a}*\right)}^2+{\left(\mathrm{b}*\right)}^2}$$

Proximate composition

The moisture (method 44-16), protein (method 46-10), fat (method 30-10), ash (method 08-01) were analyzed based on AACC (2000) procedures. The soluble and insoluble dietary fibers were estimated according to the methods of Asp et al. (1983). An average of three independent determinations was recorded.

Rheological characteristics of wheat flour

Consistograph characteristics

The effect of incorporation of MGPs on the rheological behavior of wheat flour was determined using Consistograph (Chopin Technologies, Villeneuve-la-Garenne Cedex, France). Consistographic characteristics like (i) water absorption capacity, (ii) dough development time (TprMax), the time to reach maximum consistency with a maximum pressure of 2200 mb (millibar), (iii) maximum tolerance index (Tol), time elapsed from maximum to 20 % of the dough consistency peak and (iv) the extent of decay in pressure, the difference in mb in the dough consistency peak height in 250 s (D250) and 450 s (D450) were determined according to AACC (2000) method 54–50. An average of three independent determinations was recorded.

Pasting characteristics

The pasting characteristics of wheat flour were studied using the Rapid Visco Analyzer (Newport Scientific Pvt. Ltd., Warier Wood, Australia) according to AACC (2000) method 76–21 with modifications. The total program was run for 13 min starting at 50 °C, and heated to 95 °C at a constant rise of 12 °C/min, holding the temperature at 95 °C for 2.5 min and then cooling the system to 50 °C at 12 °C/min for 3 min. The viscosity parameters measured were pasting temperature, peak viscosity, breakdown viscosity, final viscosity and setback viscosity. An average of three independent determinations was recorded.

Preparation of biscuits

Biscuits were prepared using multigrain premixes according to the AACC (2000) method 10–52 with modification made by Kumar et al. (2015). The biscuits in three replicates were prepared according to following standardized formula.

Wheat flour 300 g, pulverized sugar 105 g, bakery shortening 60 g, sodium chloride 1.5 g, sodium bicarbonate 1.5 g, ammonium bicarbonate 3 g, skimmed milk powder 6 g, dextrose 6 g, vanilla essence 3 ml. The wheat flour was replaced by all the four MGPs separately at 0, 10, 20, 30, 40 and 50 % level respectively.

The method of preparation was as follows: Sugar, bakery shortening, skimmed milk powder, dextrose and vanilla flavor were creamed in Hobart mixer with a flat blade, for 5 min at 61 rpm and to the cream, water containing dissolved sodium chloride, sodium bicarbonate and ammonium bicarbonate were separately added and mixed for 5 min at 125 rpm until homogenous cream. Finally, sifted wheat flour was added and mixed at 61 rpm for 2 min. The dough was sheeted to 3.5 mm thickness using a metal frame of 3.5 mm thickness and cut into round shape of 55 mm diameter using circular cutter. The baking was done at 200 °C for 10 min. The biscuits were cooled and stored in airtight container.

Texture profile analysis of biscuit dough

The texture of biscuit dough’s from all the four mixes were measured with texture profile analysis (TPA) method of Bourne (1978) using a texture analyzer (TA- HD plus, Stable Micro Systems, Surrey, U.K). The hardness, springiness and gumminess of the biscuit dough were measured with 5 Kg load cell. The following conditions were used: biscuit dough thickness, 10 mm (circular disc); diameter, 40 mm; circular probe - 80 mm diameter; crosshead speed, 50 mm/min; compression - 50 % of dough height. The data were collected for three replicates and the mean value was reported.

Quality characteristics of biscuits

Physical characteristics

The diameter (D) and thickness (T) in mm of biscuit were measured by placing six biscuits edge to edge and placing one above the other respectively. The biscuits were rearranged and restacked to get average diameter and thickness. Mean weight of the two biscuits was noted and spread ratio (D/T) of biscuits was calculated.

Texture measurement

The breaking strength of biscuit was determined by texture analyzer using triple beam snap (three point break) techniques as per method described by Gains (1991). The peak force from the resulting curve indicated as the breaking strength of biscuits. The mean of three independent determinations was reported.

Sensory evaluation

Sensory quality of multigrain biscuits (MGBs) were evaluated by 20 panelists of age between 25 and 50 years, including both male and female, who had earlier experience in quality evaluation of bakery products. They were further oriented in four sessions, including two hours of training in each session. Six samples, including control biscuits were evaluated in triplicates by each panelist for crust color, surface character, crumb color, crumb texture, taste, mouth feel and overall acceptability on a 9 point hedonic scale (1 = dislike extremely, 5 = neither like nor dislike and 9 = like extremely) according to the method of Larmond (1997). The samples were identified by code numbers and presented in a random order to the panelist.

Micro structural changes of dough and biscuits

Micro structural studies of dough and biscuits were carried out using scanning electron microscope (SEM) (EVO LS10 SEM, Zeiss, UK). The sample preparation for the study was carried out according to the method of Indrani et al. (2010) with slight modification. The dough was thinly sheeted (thickness 0.5 mm) and cut into 20 × 20 mm size pieces without damaging the structure. The dough pieces and biscuits were defatted using hexane to remove fat and freeze dried. The freeze dried samples were separately sputter coated with gold-palladium alloy and the morphological analysis was carried out at high vacuum using an operating voltage of 10 kV.

Nutritional composition of biscuits

The protein, dietary fiber and mineral content of control and selected experimental biscuits were analyzed using the same method as mentioned earlier.

Statistical analysis

All the experiments were carried out in triplicates and data was statistically analyzed using Duncan’s new multiple range tests (DMRT) with different experimental group using statistica software version 7.0 of Stat Soft Incorporation, Tulsa, OK, USA as per the method of Steel and Torrie (1960). The significant level was established at P ≤ 0.05.

Results and discussion

Color analysis of MGPs

The color values of MGPs are shown in Table 2. There is a significant (p ≤ 0.05) decrease in lightness value in all the MGPs as compared to wheat flour and found to be 83.19, 79.13, 80.09, 83.8 and 93.55 for MGP I, II, III, IV and wheat flour respectively. The reduction in the lightness (L*) value resulted in an increase in redness (a*) value. The decrease in L* and increase in a* may be attributed to the presence of dark colored flours like finger millet, pearl millet, wheat germ, etc. The significantly (p ≤ 0.05) higher increase in redness value in case of MGP I may be due to the presence of wheat germ. The MGP IV had significantly (p ≤ 0.05) higher positive yellowness (b*) value of 17.28, may be due to the presence of maize. The chroma which is the measure of purity or intensity of color increased from 10.04 of wheat flour to 16.52, 15.29, 14.78, and 17.31 for MGP I, II, III and IV respectively.

Table 2.

Proximate composition and color values of MGPs

Parameter	Wheat flour	MGP I	MGP II	MGP III	MGP IV
Moisture %	12.96 ± 0.1a	7.73 ± 0.06b	7.42 ± 0.05c	8.13 ± 0.09d	7.27 ± 0.06c
Ash %	0.58 ± 0.09a	3.35 ± 0.1b	3.23 ± 0.007ab	3.46 ± 0.007b	3.11 ± 0.04c
Total protein %	10.91 ± 0.18a	27.84 ± 0.24b	23.96 ± 0.16c	26.28 ± 0.18d	22.91 ± 0.22e
Dry gluten %	9.94 ± 0.28	–	–	–	–
Total fat %	1.33 ± 0.1a	4.69 ± 0.15b	3.49 ± 0.06c	3.18 ± 0.18d	2.91 ± 0.16d
Total dietary fiber %	2.93 ± 0.24a	18.72 ± 0.39b	18.68 ± 0.22b	17.51 ± 0.03c	16.82 ± 0.18d
Insoluble dietary fiber %	2.32 ± 0.23a	13.41 ± 0.08b	12.53 ± 0.37c	10.13 ± 0.08d	10.03 ± 0.19d
Soluble dietary fiber %	0.62 ± 0.01a	5.31 ± 0.31b	6.51 ± 0.59c	7.38 ± 0.6d	6.79 ± 0.01c
Carbohydrate %	74.22 ± 0.37a	56.39 ± 0.42b	61.9 ± 0.16c	58.95 ± 0.22d	63.8 ± 0.13c
Energy kcal	352.49 ± 0.54a	379.13 ± 0.61b	374.85 ± 0.78c	369.54 ± 0.39d	373.03 ± 0.4c
L*	93.55 ± 0.14a	83.19 ± 0.06b	79.13 ± 0.19c	89.09 ± 0.26d	83.8 ± 0.27b
a*	0.47 ± 0.01a	2.12 ± 0.05b	1.54 ± 0.04c	1.21 ± 0.01d	1.11 ± 0.02e
b*	10.03 ± 0.11a	16.38 ± 0.15b	15.21 ± 0.16c	14.74 ± 0.27c	17.28 ± 0.19d
dE	10.33 ± 0.06a	12.27 ± 0.02b	15.11 ± 0.18c	9.07 ± 0.21d	12.16 ± 0.28b
Hue angle (h0)	87.32 ± 0.01a	82.62 ± 0.13b	84.23 ± 0.21c	86.91 ± 0.09a	86.38 ± 0.05d
Chroma	10.04 ± 0.11a	16.52 ± 0.1b	15.29 ± 0.15c	14.78 ± 0.27c	17.31 ± 0.19d

Values are mean ± standard deviation of three independent determinations. ^a Mean values in the same column within the mix (I, II III, IV) followed by different superscripts differ significantly (P ≤ 0.05)

MGPs multigrain premix; L* lightness/darkness; a* redness/blueness; b* yellowness/greenness; dE color difference

Proximate composition of MGPs

The proximate composition of MGPs is shown in Table 2 and there is a significant (p ≤ 0.05) decrease in moisture content of all the MGPs (7.27–8.13 %) when compared to wheat flour (12.9 %) which may be due to lower moisture of grains and also moisture loss during milling. The ash content values of MGPs are found to be significantly (p ≤ 0.05) higher as compared to wheat flour may be due to the use of whole grain flours in the preparation of MGPs. Earlier studies also indicated high ash content in multigrain mixes (Indrani et al. 2010). The wheat flour used in the study contains dry gluten of 9.9 % showing medium hard nature of wheat used for milling. The protein content was found to be higher in MGPs than wheat flour due to the presence of pulses and oil seeds. Among the MGPs, MGP III had highest protein content of 26.28 %. From the Table 2, it is observed that MGP I contained significantly (p ≤ 0.05) higher fat content than other premixes due to the presence of wheat germ (Shivani and Sudha 2011). The total dietary fiber in MGPs ranged from 16.82 in MGP IV – 18.72 % in the case of MGP I, which is almost 5 to 6 fold higher than wheat flour of 2.93 %, while the soluble dietary fiber ranged from 5.3 in MGP I– 7.4 % in the case of MGP III. The high soluble dietary fiber is due to the presence of either barley or oats in the premix (Izydorczyk and Dexte 2008).

Effect of incorporation of MGPs on rheological characteristics of wheat flour

Consistograph characteristics

The effect of incorporation of MGPs on the rheological characteristics of wheat flour is represented in Table 3. The water absorption capacity significantly (p ≤ 0.05) decreased from 56.0 in control sample to 50.9 % in the case of MGP II at 50 % of replacement. The reduction in water absorption capacity is attributed to dilution of gluten (Hoseney 1994). There is no drastic increase in dough development time (TprMax) up to 30 % level of incorporation. However, beyond that level, there is a significant (p ≤ 0.05) increase in TprMax. Earlier, Callejo et al. (2009) also observed an increase in the TprMax while using rye meals in wheat flour.

Table 3.

Effect of incorporation of MGPs on consistograph characteristics of wheat flour and texture profile analysis of biscuit dough’s

MGPs	Level (%)	WAC (%)	TPrMax (s)	Tol (s)	D250 (mb)	D450 (mb)	Hardness (N)	Springiness (mm)	Gumminess (N)
MGP I	0	56.0a	180b	332b	59d	423d	311.66d	0.21a	52.21a
	10	54.4b	182b	398a	520a	1002a	403.00b	0.20ab	50.36ab
	20	53.9bc	189ab	348b	322b	772b	413.08a	0.19abc	48.44b
	30	53.3bc	191ab	204c	187c	586c	417.72a	0.18bc	45.22bc
	40	52.9cd	272c	174cd	157c	206e	419.29a	0.17c	34.88c
	50	51.9d	297a	160d	72d	92f	371.45c	0.17c	32.21c
MGP II	0	56.0a	180b	332b	59d	423d	311.66e	0.21a	52.21a
	10	53.8b	183b	358a	470a	891a	439.77b	0.21a	51.47a
	20	53.3c	192ab	337ab	338b	774b	446.93b	0.20a	47.78b
	30	52.6d	209c	288c	279c	454c	460.26a	0.19a	40.29c
	40	51.9e	272d	208d	278c	324e	398.22c	0.19a	32.81cd
	50	50.9f	309e	103e	185e	269f	372.71d	0.18a	26.09d
MGP III	0	56.0a	180e	332b	59d	423e	311.66e	0.21a	52.21a
	10	55.4b	181e	388a	384a	844a	319.65d	0.21a	36.86b
	20	54.1c	186d	378ab	372a	746b	339.69b	0.18b	31.81bc
	30	53.6d	193c	280c	313b	716c	358.47a	0.17b	28.73c
	40	53.2e	213b	261d	252c	644d	345.66b	0.16b	27.78c
	50	52.8f	227a	246d	121e	300f	330.76c	0.16b	24.64d
MGP IV	0	56.0a	180f	332b	59d	423d	311.66e	0.21a	52.21a
	10	55.3b	187e	340b	325a	776a	368.66b	0.21a	36.53b
	20	54.8c	197d	300a	292ab	539b	382.88a	0.19ab	31.32c
	30	54.6cd	206c	246ab	188b	506c	385.75a	0.19ab	24.44cd
	40	54.3d	238b	220c	185b	279e	357.87c	0.17bc	25.48d
	50	52.8e	259a	115d	133c	162f	325.04d	0.15c	23.65cd

Mean values in the same column within the mix (I, II III, IV) followed by different superscripts differ significantly (P ≤ 0.05)

MGPs multigrain premix; WAC water absorption capacity; TPrMax time in seconds to reach maximum pressure; Tol maximum tolerance index; D250 decay in 250 s; D450 decay in 450 s

Maximum tolerance index (Tol), a measure of stability of the dough, increased up to 20 % addition of MGPs and thereafter further addition decreased the tolerance to mixing. Gunathilake et al. (2009), also observed similar results by adding defatted coconut flour to wheat flour and correlated the data to the stabilization of the gluten structure of the dough by coconut protein. Similarly, there could be a stabilization of wheat protein with other proteins present in MGP. The Decay in pressure at 250 s (D250) and 450 s (D450) is greater at any levels of addition of MGP. The decay was decreased consistently as the level of incorporation of MGP increased. Similar observations were made by Callejo et al. (2009) when incorporating rye flour to wheat flour.

Pasting characteristics

The pasting properties of wheat flour as affected by the incorporation of MGPs are shown in Table 4. The pasting temperature significantly (p ≤ 0.05) increased from 67.10 °C in control sample to 79.20 °C in the case of MGP IV sample at 50 % of replacement. The increase is minimum in MGP III and maximum in MGP IV. This variation could be attributed to the different grains used in MGPs which have different pasting temperatures (Sanaa and El-syed, 2006). Earlier, Khan et al. (2015) also reported increase in pasting temperature with an increase in the level of non-wheat flour due to higher resistance of starch granules to swell. The peak viscosity decreased with the increase in the level of incorporation of MGP. The extent of decrease varied with the type of MGP used. Similar observations were also made by Hamaker and Griffin (1993) while studying the effect of protein on rice starch gelatinization. Breakdown viscosity showed a decreasing trend from 128.83 RVU in control sample to 82.33, 73.67, 65.58, and 63.75 RVU for MGP I, MGP II, MGP III and MGP IV, respectively as the level of incorporation of MGP increased from 0 to 50 %. Final viscosity, which indicate the ability of starch to form a gel on cooling decreased with the increase in the level of incorporation of MGPs. Set back viscosity, a measure of aggregation of amylose fractions leading to the reinforcement of swollen granules and fragments by bonds between and within them also decreased with the increase in the incorporation of MGP from 0 to 50 % (Khan et al. 2015). A representative graph of RVA at the 30 % level of incorporation of MGPs is depicted in Fig. 1.

Table 4.

Effect of incorporation of MGPs on pasting characteristics of wheat flour

MGP	Level (%)	Pasting temperature (°C)	Peak viscosity (RVU)	Breakdown viscosity (RVU)	Final viscosity (RVU)	Set back viscosity (RVU)
MGP I	0	67.10f	273.67a	128.83a	281.58a	136.75a
	10	67.85e	245.92b	101.08b	274.08b	127.41b
	20	69.35d	235.92c	99.25c	269.00c	123.67c
	30	71.85c	234.67c	98.25d	256.83d	123.25c
	40	76.80b	218.25d	90.58e	240.42e	120.42d
	50	77.70a	201.50e	82.33f	237.92f	118.75e
MGP II	0	67.10e	273.67a	128.83a	281.58a	136.75a
	10	67.05e	241.00b	107.42b	272.00b	138.42a
	20	69.35d	221.83c	98.75c	260.50c	137.42a
	30	75.10c	204.58d	93.58d	251.17d	135.17a
	40	77.50b	182.50e	88.08e	240.92e	130.00b
	50	78.20a	166.58f	73.67f	230.18e	129.26b
MGP III	0	67.10e	273.67a	128.83a	281.58a	136.75a
	10	67.10e	279.67b	125.50b	290.42a	136.25a
	20	68.70d	240.00c	113.87c	249.67c	123.50b
	30	71.90c	220.58d	96.67d	234.17d	121.25c
	40	74.35b	179.83e	68.92e	208.50e	97.58d
	50	75.10a	179.33e	65.58f	206.58f	96.83de
MGP IV	0	67.10d	273.67a	128.83a	281.58a	136.75a
	10	69.55c	241.42b	105.33b	269.92b	133.84b
	20	71.05b	222.83c	98.33c	258.02c	133.52b
	30	79.05a	195.00d	89.08d	248.00d	131.83c
	40	78.40a	175.17e	78.58e	240.16e	129.58d
	50	79.20a	154.92f	63.75f	239.25e	129.08d

^aMean values in the same column within the mix (I, II III, IV) followed by different superscripts differ significantly (P ≤ 0.05)

RVU rapid visco unit; MGPs multigrain premix

Fig. 1.

RVA curve of wheat flour and at 30 % level of incorporation of different MGPs. a – Wheat flour; b- MGP I; c- MGP II; d – MGP III; e- MGP IV; MGPs multigrain premix

Texture profile analysis of biscuit dough

The texture profile analysis of biscuit dough showed that with the increase in the addition of 10–50 % MGP to control biscuit dough, the hardness value increased significantly (p ≤ 0.05) irrespective of type of MGP confirming that, the dough with MGP is harder than the control biscuit dough. In general, the hardness values were higher for MGP I and II as compared to III and IV at comparable levels. The higher increase in hardness with MGP I and II could be attributed to the presence of finger millet flour in the premix (Crassina et al. 2012). Springiness is the elastic recovery property of dough after removal of first deforming force decreased from 0.21 mm observed for control dough to 0.15 mm in case of IV at 50 % of replacement. A similar reduction in springiness property of biscuit dough by the addition of fiber and protein rich Moringa leaves was reported by Dachana et al. (2010). Gumminess drastically reduced from 52.21 N in control sample to 32.21, 26.09, 24.64 and 23.65 N for MGP I, II, III and IV respectively with an increase in the level of MGPs. Earlier, Nirmala et al. (2011) also reported a reduction in springiness and gumminess value of cookie dough with the addition of fenugreek and flax seed powder and attributed this to dilution of gluten.

Effect of MGPs on the quality of multigrain biscuits (MGBs)

Color

The surface color values of different MGBs are represented in Table 5. The lightness (L*) value indicating whiteness of the product decreased from 67.95 in control biscuits to 55.0, 57.78, 59.18 and 60.03 for MGB I, II, III and IV respectively with the addition of MGPs. A similar trend was observed by Shivani and Sudha (2011) for wheat germ based biscuits. The redness (a*) value of the biscuits increased and yellowness (b*) value decreased significantly (p ≤ 0.05) as the level of MGP increased. The increase in redness value of biscuits could be attributed to the presence of high protein in MGPs which resulted in browning due to the Maillard reaction. The chroma and hue angle values which are direct indicators of color intensity decreased with increase the level of incorporation of MGPs.

Table 5.

Physical properties of multigrain biscuits (MGBs)

Flour	Level (%)	Weight (g)	Diameter (D) (mm)	Thickness (T) (mm)	Spread ratio (D/T)	Breaking strength (N)	L*	a*	b*	dE	h0	Chroma
MGP I	0	7.86 ± 0.32a	57.83 ± 0.41a	5.66 ± 0.51b	10.28 ± 1.02a	13.25 ± 0.26a	67.95 ± 0.01a	10.66 ± 0.14b	35.39 ± 0.16a	3.14 ± 0.05e	36.95 ± 0.19a	73.26 ± 0.11a
	10	8.49 ± 0.57ab	57.67 ± 0.52a	5.83 ± 0.41b	9.93 ± 0.72a	16.86 ± 0.3b	64.43 ± 0.12b	11.22 ± 0.33b	34.52 ± 0.09b	3.68 ± 0.14d	36.3 ± 0.19b	72.16 ± 0.25b
	20	8.99 ± 0.57ab	57.5 ± 0.54a	5.92 ± 0.2b	9.73 ± 0.41a	17.3 ± 0.37b	62.16 ± 0.4c	11.35 ± 0.14b	34.11 ± 0.07bc	5.98 ± 0.39c	35.95 ± 0.11b	71.6 ± 0.17b
	30	9.30 ± 0.36b	57.33 ± 0.52a	6.00 ± 0.63b	9.67 ± 1.04a	19.52 ± 0.55c	59.87 ± 0.11d	11.43 ± 0.16b	34.12 ± 0.04bc	8.22 ± 0.13b	35.98 ± 0.01b	71.49 ± 0.26b
	40	9.58 ± 0.27c	56.5 ± 0.55b	6.33 ± 0.82ab	9.06 ± 1.33ab	24.20 ± 0.79d	60.57 ± 0.18e	11.68 ± 0.43a	33.75 ± 0.16c	8.69 ± 0.01b	35.92 ± 0.08b	72.2 ± 0.39b
	50	9.67 ± 0.27d	55.17 ± 0.41c	6.83 ± 0.75a	8.15 ± 0.85b	28.68 ± 0.88e	55 ± 0.31f	12.52 ± 0.42ab	32.93 ± 0.22d	13.32 ± 0.29a	35.23 ± 0.36c	69.2 ± 0.51c
MGP II	0	7.86 ± 0.32a	57.83 ± 0.41a	5.66 ± 0.51c	10.28 ± 1.02a	13.25 ± 0.26a	67.95 ± 0.01a	10.66 ± 0.14b	35.39 ± 0.16a	3.14 ± 0.05e	36.95 ± 0.19a	73.26 ± 0.11a
	10	8.25 ± 0.19b	58.6 ± 0.54a	5.72 ± 0.26bc	10.26 ± 0.47a	15.47 ± 0.72b	64.07 ± 0.16b	11.17 ± 0.17b	34.75 ± 0.31a	3.97 ± 0.18a	36.51 ± 0.35a	72.78 ± 0.18ab
	20	8.33 ± 0.41b	58.2 ± 0.84a	5.78 ± 0.18abc	10.07 ± 0.34a	18.17 ± 0.68c	61.22 ± 0.94c	11.47 ± 0.22bc	33.72 ± 0.59b	6.98 ± 0.78b	35.87 ± 0.14a	71.99 ± 0.46bc
	30	8.56 ± 0.35b	56.6 ± 0.55b	6.22 ± 0.31abc	9.12 ± 0.52b	18.99 ± 0.57c	60.61 ± 0.13c	11.93 ± 0.08c	32.32 ± 0.18c	7.97 ± 0.19c	35.59 ± 0.33ab	71.71 ± 0.33c
	40	9.04 ± 0.17c	55.8 ± 0.84bc	6.36 ± 0.36ab	8.80 ± 0.61b	22.39 ± 0.79d	58.38 ± 0.28d	12.41 ± 0.28cd	31.64 ± 0.09c	10.61 ± 0.23d	34.14 ± 0.43b	71.25 ± 0.34c
	50	9.41 ± 0.23c	54.9 ± 0.89c	6.44 ± 0.38a	8.55 ± 0.55ab	25.65 ± 0.62e	57.78 ± 0.56d	13.48 ± 0.25d	30.69 ± 0.14d	11.12 ± 0.26d	33.71 ± 0.82b	70.99 ± 0.41c
MGP III	0	7.86 ± 0.32a	57.83 ± 0.41a	5.66 ± 0.51a	10.28 ± 1.02a	13.25 ± 0.26a	67.95 ± 0.01a	10.66 ± 0.14b	35.39 ± 0.16a	3.14 ± 0.05e	36.95 ± 0.19a	73.26 ± 0.11a
	10	8.09 ± 0.29a	57.6 ± 0.55a	5.7 ± 0.27a	10.12 ± 0.42b	13.93 ± 0.21b	65.87 ± 0.17b	10.97 ± 0.11a	35.05 ± 0.25ab	3.89 ± 0.09a	36.72 ± 0.48a	72.62 ± 0.2b
	20	8.30 ± 0.20b	57.8 ± 0.45a	5.8 ± 0.27a	9.98 ± 0.44b	15.32 ± 0.29ab	63.54 ± 0.38c	11.89 ± 0.11ab	34.89 ± 0.39ab	4.67 ± 0.13b	36.87 ± 0.01a	71.19 ± 0.02c
	30	8.52 ± 0.15c	57.1 ± 0.45a	5.8 ± 0.27a	9.98 ± 0.37b	16.43 ± 0.27c	61.64 ± 0.23d	12.58 ± 0.24c	34.69 ± 0.28ab	7.67 ± 0.29c	35.52 ± 0.29b	70.53 ± 0.16d
	40	8.76 ± 0.15cd	57.2 ± 0.74a	5.92 ± 0.19a	9.85 ± 0.31b	19.11 ± 0.15d	61.06 ± 0.29d	13.28 ± 0.18d	34.27 ± 0.16b	8.11 ± 0.17d	35.06 ± 0.26bc	70.21 ± 0.16d
	50	8.93 ± 0.30cd	55.6 ± 0.55b	6.12 ± 0.38a	9.11 ± 0.51c	26.69 ± 0.65e	59.18 ± 0.27e	13.53 ± 00.07d	34.13 ± 0.13b	9.25 ± 0.03f	34.42 ± 0.09c	69.59 ± 0.12e
MGP IV	0	7.86 ± 0.32a	57.83 ± 0.41a	5.66 ± 0.51c	10.28 ± 1.02a	13.25 ± 0.26a	67.95 ± 0.01a	10.66 ± 0.14b	35.39 ± 0.16a	3.14 ± 0.05e	36.95 ± 0.19a	73.26 ± 0.11a
	10	8.01 ± 0.19a	58.2 ± 0.84a	5.7 ± 0.19bc	10.22 ± 0.35a	14.86 ± 0.83b	65.38 ± 0.33b	10.83 ± 0.11a	34.53 ± 0.16b	3.22 ± 0.13a	36.25 ± 0.11b	72.64 ± 0.16b
	20	8.53 ± 0.09b	56.9 ± 0.84b	5.84 ± 0.11bc	9.89 ± 0.09ab	16.28 ± 0.43c	64.62 ± 0.19c	11.18 ± 0.26a	34.28 ± 0.0.25b	3.56 ± 0.14b	35.93 ± 0.28ab	72.55 ± 0.01b
	30	8.67 ± 0.18b	56.8 ± 0.45b	5.9 ± 0.22abc	9.64 ± 0.39ab	17.12 ± 0.73c	63.16 ± 0.11d	11.37 ± 0.14ab	33.91 ± 0.32b	4.86 ± 0.11c	35.41 ± 0.06c	72.38 ± 0.08b
	40	8.92 ± 0.18bc	56.2 ± 0.84b	6.18 ± 0.22ab	9.11 ± 0.43bc	18.65 ± 0.88d	60.72 ± 0.15e	11.86 ± 0.11b	35.01 ± 0.11c	7.34 ± 0.17d	34.92 ± 0.16d	71.43 ± 0.19c
	50	9.38 ± 0.16c	55.6 ± 0.55ab	6.38 ± 0.13a	8.72 ± 0.21c	26.4 ± 0.511e	60.03 ± 0.07f	12.21 ± 0.37c	32.69 ± 0.06d	7.93 ± 0.08f	34.25 ± 0.18e	70.97 ± 0.01d

Values are mean ± standard deviation of three independent determinations. ^a Mean values in the same column within the mix (I, II III, IV) followed by different superscripts differ significantly (P ≤ 0.05)

L* lightness/darkness; a* redness/blueness; b* yellowness/greenness; dE color difference; h0 hue angle, MGP multigrain premix

Physical characteristics

The biscuits prepared using 0, 10, 20, 30, 40 and 50 % level of incorporation of all the four MGPs separately are evaluated for various physical parameters (Table 5). The weight of the biscuits increased with the addition of MGP due to increase in the density of biscuits (Francine et al. 2011). The diameter of biscuits decreased and thickness increased with the addition of MGP irrespective of the type. This is reflected in the values of the spread ratio, which decreased from 10.28 in control sample to 8.15, 8.55, 9.11 and 8.72 in the case of MGP I, II, III and IV respectively. This is may be due to dilution gluten and disruption of gluten protein matrix. These results are in agreement with earlier studies carried out by Jyotsna et al. (2012) for green gram incorporated biscuits and Crassina et al. (2012) for finger millet flour biscuits.

Texture measurement

Breaking strength of biscuits measured by texture analyzer showed that the force required to break the biscuits increased significantly (p ≤ 0.05) from 13.25 in control sample to 28.68, 25.65, 26.69 and 26.4 N in the case of MGP I, II, III and IV respectively at 50 % of replacement. The biscuit hardness is affected by the interaction of proteins and starch by hydrogen bonding. The similar finding of increased breaking strength of biscuits by adding fenugreek seed and flax seed was reported by Nirmala et al. (2011) and attributed to decrease in spread ratio.

Sensory characteristics

The results of sensory analysis indicated that as the level of incorporation of MGP increase from 10 to 50 %, sensory scores of biscuits decreased significantly (Fig. 2a–d). The crust color darkens with the increase in the level of MGPs as indicated by lower scores. This darkening of color may be due to addition of dark color MGPs and also attributed to the Maillard reaction between protein rich MGP and sugars in biscuits (Lee and Brennand 2005). Among the biscuits, the one prepared from MGP I was much darker than other MGPs at comparable levels. The surface of biscuits becomes little rough in MGP incorporated biscuits. The change was similar irrespective of type of MGP used as all premixes are coarser than wheat flour. Crumb color darkened to a varying extent with an increase in the level of MGP. However, the extent of darkening is minimum in biscuits containing MGP III. The texture of biscuits hardened with increase in the level of MGP. Among the biscuits, MGP III incorporated biscuits is less hard even at the 40 % level of incorporation. The change in texture as a result of incorporation of MGP is also reflected in the breaking strength score. Biscuits made with MGP III had a better wholesome taste as compared with biscuits prepared from other MGPs.

Fig. 2.

Sensory evaluations of biscuits. a Sensory evaluation of MGB I, b MGBII, c MGB III, d MGB IV

The statistical analysis carried out on different parameters have clearly shown that there is no significant (p ≤ 0.05) difference in the various quality parameters such as crust color, surface character, crumb color, crumb texture, taste and overall acceptability up to 30 % addition of MGP. However, MGP III could be used even up to 40 % level without any significant (p ≤ 0.05) change in the above characteristics. Earlier, Crassina et al. (2012) also reported the reduction of the sensory score in the biscuits prepared with above 40 % addition of finger millet flour. This clearly suggests that the formulation of MGP III, containing barley flour, sorghum flour, chickpea flour, pea flour and defatted soya flour is best suited for preparation of multigrain biscuits with improved sensory characteristics. Hence a biscuit with MGPIII at 40 % level was selected for further studies.

Effect of MGPs on micro-structure of dough and biscuits

The micro structural studies were carried out with the help of SEM to study the internal structural changes occurring in dough development and baking. The changes in structure during dough formation and baking are mainly related to changes of two major components i.e. starch and protein. The SEM images of control dough and MGP III incorporated dough were represented in Fig. 3a and b. From the figure, the large and small starch granules enmeshed in the gluten protein matrix were observed in control dough as earlier reported by Nandeesh et al. (2009). But in MGP III incorporated dough the starch granules are partially enmeshed and number of small protein bodies of multigrain adhering to starch granules is visible. Starch granules are more intact in control dough compared to MGP III incorporated dough. Similar observation of starch granules embed on the protein matrix during dough development is observed by Rojas et al. (2000). Starches play an important role in structuring of dough and biscuits by its interaction with the protein matrix during baking. The protein matrix appears to be very thin in MGP III incorporated dough as the continuity of protein matrix is disrupted by the addition of protein and fiber rich MGP III as compared to control dough (Pomeranz et al. 1984).

Fig. 3.

SEM images of dough and biscuits. a Control dough, b MGP III at 40 % incorporated dough, c Control biscuits, d MGP III at 40 % incorporated biscuits. SSG small starch granules, LSG large starch granules, GS gelatinized starch, PGS partially gelatinized starch, PM protein matrix, PB protein bodies

SEM images for control and MGP III incorporated biscuits surface were represented in Fig. 3c and d. In Fig. 3c, the small and large starch granules are gelatinized and gel formation is observed, whereas in Fig. 3d, starch is partially gelatinized and an outline of gelatinized starch is observed. This may be due to the lack of sufficient water in the MGP incorporated dough as most of the water is absorbed by fiber rich MGP (Kulp et al. 1991). The microstructure of MGP III incorporated biscuits showed a severe disrupted gluten protein matrix due to the replacement of wheat flour with high fiber. This is also indicated in the biscuit texture, as the hardness of biscuits increased due to a reduction in the spread ratio (Mc Watters 1977). The permanently disrupted protein matrix with incorporation of green gram flour was reported by Jyotsna et al. (2012). Earlier, Flint et al. (1970), observed openings of various sizes and cavities on the surface of the sweet, semi-sweet biscuits and cream-crackers biscuits. Similar cavities were found in this study. These cavities are formed due to expansion of gas bubbles with increase in baking temperature, resulted in an increase of water vapour pressure leads to rupture of membrane to form holes and tunnels in the biscuits through which gas will escape.

Nutritional composition of MGB

The nutritional composition of multigrain biscuits developed using MGP III at 40 % is depicted in Fig. 4, clearly shows a significant (p ≤ 0.05) increase in nutritional parameters like protein, dietary fiber and mineral content when compared to wheat flour biscuits.

Fig. 4.

Effect of MGP on protein, dietary fiber and mineral content of biscuits. MGP multigrain premix; Mean values of triplicates; SDs are denoted as bars

Conclusion

All the four multigrain premixes prepared are found to be rich in protein, dietary fiber and mineral content and incorporation of these MGPs at varying proportions significantly (p ≤ 0.05) decreased the consistograph water absorption, peak viscosity and increased the pasting temperature and biscuit dough hardness. The biscuit making trials showed that biscuits became slightly harder depending on the level and type of premix used. These biscuits had better taste and flavor of multigrain along with increased nutritional characteristics. The MGP III could be incorporated even up to 40 % level indicating its suitability for obtaining biscuits with much higher nutrition and overall acceptability without considerably affecting the other quality parameters. Two fold increases in protein, three fold increases in dietary fiber and one fold increase in mineral content was observed in the multigrain biscuits. The MGPs will give new dimensions in the development of nutritious biscuits and boost the industry to newer heights.