Utilization of Defatted Mango Kernel in Wheat-Based Cereals Products: Nutritional and Functional Properties

ABSTRACT

The mango kernel is a byproduct of mango processing industries and it contains appreciable quantities of edible oil and quality proteins. In the present research, wheat flour was partially replaced with defatted mango kernel flour up to 30% and blends were further utilized for the preparation of biscuits. The nutritional and functional properties of flour blends were determined in the first phase. The second phase dealt with product analysis and sensorial appraisal from the trained taste panel. The results indicated that the addition of mango kernel flour improved the mineral and fiber content of flour blends. The addition of mango kernel flour affected emulsifying and foaming properties of flour blends negatively, while water and oil absorption improved positively from 60.76 ± 2.39% to 86.29 ± 2.51% and 81.81 ± 2.94% to 123.87 ± 5.39%, respectively. The results might be due to lower bulk density of blends. The cookies prepared from flour blends showed improved color tonality and textural characteristics. Sensorial appraisal from a trained taste panel was awarded to cookies containing 15% and 20% defatted mango kernel flour, however, the rating was slightly less than the control. The results were conclusive that defatted mango kernel can be used at 15% and 20% with significant consumer acceptability. Future aspects of the present research include the extraction of principal ingredients, e.g., starch and proteins, for value addition.

KEYWORDS:

• Food security
• alternative food resources
• mango kernel
• functional properties
• sensory appraisal

Introduction

Food is vital for human life as it provides essential nutrients required for maintaining normal body growth and development. The escalating population worldwide has resulted in a shortage of food in some regions of the world. Moreover, poverty and improper distribution of foods are also the main factors contributing to food insecurity. The conditions require vigorous planning and setting new goals and objectives at the government level, thus ensuring consistency in food availability. The developing world is also facing the menace of protein energy malnutrition due to an insufficient supply of proteins or intake of proteins with poor nutritional value (Arshad and Shafqat, 2012). The conditions in Pakistan are even worse due to intake of poor quality of proteins mainly due to the reliance of the population on dietary staples. Most of the communities living in the area are unable to purchase meat and meat products to balance their diets resulting in malnutrition (Imdad et al., 2011; Iqbal et al., 2006). Formulation of composite flour is an important strategy for development of value-added products with optimal food security and health benefits. Among different opportunities, cereal-based sweet-dough baking products are suitable options from composite flour containing non-wheat cereal grains, legumes, or some unconventional sources (Rehman et al., 2007).

Mango seed kernel is a by-product of the fruit processing industry that can be utilized as an unconventional source in composite flour technology (Arogba, 2001). In Pakistan, mango is ranked second in fruits production with an annual production of 1.8 million metric tons worth 56 billion rupees. Mango-seed kernel represents around 20–35% of total fruit weight; thus, around 3.6 million metric tons of this nutrient-dense commodity is wasted. Mango kernels contain fats in the range of 8.5–10.4% along with protein, ash, carbohydrate contents, i.e., 4.76–6.70%, 1.74–2.26%, and 71.90–76.28%, respectively. The protein content in mango kernel is higher than some other fruits. However, little effort has been made to utilize mango seed kernel for the preparation of value-added food products in Pakistan. The potential of mango seed kernel is also valuable owing to higher contents of fiber and quality proteins. Various scientists have explored the mango kernel as a source of starch, pectin, proteins, antioxidant, and other nutrients. Mango seed kernel contains around 10–12% oil content and, after oil extraction, the resultant material can be used in composite flour formulation (Saddique et al., 2014). The blending of defatted mango seed kernel with wheat flour needs to be researched. Internationally, studies were conducted to use mango kernel flour in baked products, however, concrete conclusions have yet to be reached.

In Pakistan, no planned study has been conducted focusing on utilization and management of mango waste/byproducts for the production of edible oil and its defatted seed kernel. The current study aims to explore the possibilities to exploit the defatted mango kernel (DFMK) for its utilization in various baked products. A solvent extraction system using hexane was used to extract mango kernel oil and the remaining (defatted mango kernel flour) was utilized to prepare wheat-defatted mango-seed kernel blends. Later, the cereal-based product, i.e., cookies, were prepared to ensure the suitability of the defatted mango kernel flour for human consumption. According to Euromonitor International (2010), the biscuits/cookies/crackers hold an approximately $70 billion market worldwide. In the present research, defatted portions were mixed with wheat flour in amounts ranging from 5% to 30% and functional properties were measured. The defatted mango kernel seed has better functional behavior with water and oil retention along with slight emulsifying properties and thus can be utilized to prepare cookies. The information derived through this research may justify the potential application of mango kernel in product development.

Materials and methods

The current study was carried out in the Postgraduate Research Laboratory, Department of Food Sciences, Bahauddin Zakariya University, Multan, Pakistan. Mango kernels of Nawabpur cultivar were purchased from a local market in Shujaabad, Multan. Raw materials for the preparation of cookies were also procured from a local market while chemicals were obtained from Sigma-Aldrich. The kernels of mango were cleaned manually to remove extraneous materials. The particle size of kernels was reduced into fine flour through a local mill and was packed and stored at room temperature for further study.

Preparation of defatted mango kernel flour

Defatted mango was prepared by the extraction of oil (solvent extraction technique using hexane as solvent) from the mango flour (AOCS, 1998). After the oil extraction, the remaining material was microwave heated and later processed by Saddique et al. (2014). Defatted mango kernel was subjected to various analyses; proximate analyses and mineral compositions are described below.

Proximate analysis of defatted mango kernel

Defatted mango kernels were analyzed for crude protein, moisture, ash, crude fat, crude fiber, and nitrogen free extract (NFE) according to the respective methods described in AACC (2000), i.e., moisture content (Method No. 44-15A), ash (Method No. 08-01), crude protein (Method No. 46-30), crude fat (Method No. 30-25), and crude fiber (Method No. 32-10). NFE was calculated using the expression, i.e., NFE% = 100 – (moisture% + ash% + crude protein% + crude fat% + crude fiber%).

Preparations and analysis of flour blends

Flour blends were prepared by gradually replacing wheat flour (5%, 10%, 15%, 20%, 25%, and 30%) with defatted mango to find its suitability in the end product. Functional properties, such as water and oil absorption capacities, emulsion capacity and stability, foaming capacity and stability, bulk density of flour blends, and DFMK, were determined according to their respective procedures. The bulk density of blends was determined as outlined by Okaka and Potter (1977). A 50-g flour sample was put into a 100-mL measuring cylinder. The cylinder was tapped several times on the laboratory bench to a constant volume. The bulk density (g/cm³) was calculated as weight of flour (g) divided by flour volume (cm³).

Water and oil absorption capacities of flour blends were measured by the centrifugation method of Sosulski et al. (1976). Each of the flour blends (5.0 g) were mixed in 25 mL of distilled water and placed in pre-weighed centrifuge tubes. After 5 min, these tubes were stirred and held for 30 min, followed by centrifugation (Sorvall RC-5B, DuPont Instrument, Newtown, CT, USA) for 25 min at 3000 g. The supernatant was transferred, excess moisture was removed by draining, and water absorption capacity was expressed as the number of grams of water bound per gram of sample on a dry basis. For the determination of oil absorption capacity, a 5.0-g sample was mixed with 25 mL of corn oil in weighed centrifuge tubes. The contents of the tubes were stirred for 1 min in order to get the complete dispersion of the sample in the oil. After a holding period of 30 min, the tubes were centrifuged at 3000 g for 25 min. The separated oil was then removed with a pipette and the tubes were inverted for 25 min to drain the oil prior to reweighing. The oil absorption capacity was expressed as grams of oil bound per gram of the sample on dry basis.

Emulsifying activity and stability were determined by the method of Agyare et al. (2009). Samples (5.0 g) were homogenized for 30 s in 50 mL of water using a homogenizer (Brinkmann, Wesbury, NY, USA) at ~10,000 rpm). Corn oil (25 mL) was added, and the mixture was homogenized again for 30 s. Another 25 mL of corn oil were added, and the mixture was homogenized for 90 s. The emulsion was divided into two 50-mL aliquots and centrifuged at 1100 g for 5 min. Emulsifying activity was calculated by dividing the volume of the emulsified layer by the volume of emulsion before centrifugation at 1100 g. The emulsion stability was determined using similar samples for measurement of emulsifying activity. They were heated for 15 min at 85 °C according to the procedure, and after temperature came back to room temperature they were divided into two 50-mL aliquots and centrifuged at 1100 g for 5 min. The emulsion stability was expressed as the percentage of emulsifying activity remaining after heating.

Foaming capacity and stability were determined as described by Okaka and Potter (1977). A 50-ml aliquot of 3% (w/v) dispersions of sample in distilled water was homogenized using a homogenizer at high setting for 2–3 min. The blend was immediately transferred into a graduated cylinder and the homogenizer cup was rinsed with 10 mL of distilled water, which was then added to the graduated cylinder. The volume of foam formed was recorded before and after whipping. Foaming capacity was expressed as the percentage increase in volume due to whipping. For the determination of foam stability as percent of the initial foam, foam volume changes in the graduated cylinder were recorded at intervals of 6 min of storage.

Product development

Cookies were prepared with some modification of the method given in AACC (2000) by using flour blends as mentioned earlier. For the preparation of cookies, ingredients were weighed accurately. Then creaming of shortening and sugar was done, followed by the addition of eggs. Creaming was continued till foaming occurred. The flour blend, cocoa powder, and baking powder were added to the creamy mass and mixed to a homogenous mass. The batter was then rolled out and was cut with the help of a biscuit cutter. The cookies were then placed on baking trays at a proper distance and were baked at 425 °F in a baking oven for 15–20 min. After baking, the cookies were cooled at room temperature and packed in polythene bags.

Physical analysis of cookies

The width, thickness, and spread factor of cookies was predicted according to the method described in AACC (2000). The width of cookies was measured by placing six biscuits horizontally (edge to edge) and rotated at 90° angles for duplicate reading. Likewise, thickness of the cookies was calculated by placing six cookies on one another and the duplicate reading was recorded. Accordingly, spread factor was calculated using the expression, i.e., SF = W/T × CF × 10 (where CF = correction factor at constant atmospheric pressure). The texture analysis of the cookies prepared with added levels of defatted mango kernel flour was assessed. The parameters like fracture-ability and hardness were measured using the protocols described by Mamat and Hill (2012). The color of cookies prepared with different levels of defatted mango kernel flour supplementation was determined using a CIE-Lab Color Meter (CIELAB SPACE, Color Tech-PCM, Washington, USA). Further, 5 g of the sample was taken and the color values—“L*” (lightness), “a*” (–a greenness; +a redness), and “b*” (–b blueness; +b yellowness)—were recorded. The data thus obtained was used to calculate chroma and hue angle (Gouveia et al., 2005). The measurements were recorded under a constant lighting condition using a white tile control (L* 97.46, a* 0.02, b* 1.72).

Sensory evaluation

The cookies were evaluated for taste, color, flavor, texture, crispiness, and overall acceptability by using a 9-point hedonic score system (9 = like extremely; 1 = dislike extremely) by a panel of judges (five judges) from the Department of Food Sciences, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, and representatives of baking industries (Meilgaard et al., 2007). Similarly, a small trial for consumer acceptability was also conducted involving 45 students of the department to rate the cookies to check their marketability. The judges were asked to express their opinion about the end product by giving scores to attributes like color, flavor, taste, texture, crispiness, and overall acceptability. During sensorial evaluation, cookies with different flour blends were placed in transparent cups and labeled with random codes. Cold water and crackers were supplied to panelists for rinsing their mouths between the samples. In each session, panelists were seated in separate booths equipped with white fluorescent lighting in an isolated room.

Statistical analysis

The data of each parameter was obtained by applying a completely randomized design (CRD). Levels of significance (P ≤ 0.05; P ≤ 0.01) were determined (ANOVA) using a 2-factor factorial CRD (software: Co-Stat v. 6.1, CoHort Software). Significant ranges were further compared using Duncan multiple range (Steel et al., 1997).

Results

Consumption patterns have been altered variably over the last two decades attributed to various reasons that include the escalating population, food availability, reliance on dietary staples, etc. In Pakistan, mango is the second most important fruit with good cash returns. However, considerable amounts of mango seeds are discarded as waste representing ~10% to 25% of the fruit. According to World Trade Organization (WTO) scenario, novel foods including new protein sources, plant extracts, or other novel food ingredients required strict evaluation for nutritional status. The use of defatted mango kernel seed as a food supplement has been seldom revealed owing to limited research. Keeping in view all of the above facts, the present study was designed to explore the role of defatted mango kernel in composite flour technology. In the first phase, the raw materials were analyzed for proximate compositions, including moisture, protein, fat, fiber, ash, and NFE, and are mentioned in Table 1. Moisture contents in the raw material were 9.995 ± 0.223% in wheat flour and 7.801 ± 0.368% in defatted mango kernel flour. The protein content present in wheat flour and mango kernel were recorded to be 10.471 ± 0.111% and 10.046 ± 0.200%, respectively. The fat content followed similar trends as it was apparent from the values that the trait was similar in both wheat flour and mango kernel, i.e., 1.101 ± 0.041% and 1.042 ± 0.026%. Contrary to protein and fat contents, the fiber and ash contents were higher in mango kernel with mean values of 3.773 ± 0.132% and 2.568 ± 0.100%, respectively. In comparison, the wheat flour contained less amounts of fiber and ash, i.e., 0.443 ± 0.021% and 0.572 ± 0.021%, respectively. Contrarily, the nitrogen free extract was higher in wheat flour (77.417 ± 0.360%) as compared to 73.317 ± 1.809% in mango kernel flour (Table 1). The defatted mango kernel flour was further utilized to prepare flour blends and evaluated for different quality traits including proximate composition and functionality. The proximate composition is dependent upon defatted mango kernel and wheat flour used in the present study. The moisture, protein, and fat contents decreased as a function of defatted mango kernel flour addition, while ash and fiber contents increased significantly.

Table 1. Analysis of raw material.

Proximate composition	Wheat flour	Defatted mango kernel flour
Moisture	9.995 ± 0.223	7.801 ± 0.368
Protein	10.471 ± 0.111	10.046 ± 0.200
Fat	1.101 ± 0.041	1.042 ± 0.026
Fiber	0.443 ± 0.021	3.773 ± 0.132
Ash	0.572 ± 0.021	2.568 ± 0.100
NFE	77.417 ± 0.360	73.317 ± 1.809

Note. NFE: Nitrogen free extract.

The functional properties that are important in assessing the suitability of flour blends for product development were also determined. The means for bulk density presented in Table 2 reflected the decreasing tendency as minimum bulk density of 0.44 ± 0.019 was recorded in T₆ (30% defatted mango kernel flour). The maximum bulk density was recorded in 100% wheat flour (0.76 ± 0.047). The means for water absorption capacity depicted the increasing tendency as minimum water absorption capacity of 60.76 ± 2.3915 was recorded in T₀ (10% wheat flour). The maximum water absorption capacity was recorded in 30% defatted mango kernel flour (86.29 ± 2.511). Likewise, minimum oil absorption capacity of 81.81 ± 2.940% was recorded in the control, while the maximum oil absorption capacity of 123.87 ± 5.387% was recorded in flour blends prepared with 30% defatted mango kernel flour. Emulsion capacity and stability varied significantly as a function of treatments. The means for emulsion capacity illustrated the decreasing tendency as the maximum emulsion capacity of 49.57 ± 3.412% was recorded in T₀ (10% wheat flour) as compared to minimum emulsion capacity of 38.99 ± 1.187 in T₆ (30% defatted mango kernel flour). To the contrary, emulsion stability increased with the addition of mango kernel flour and T₆ (30% defatted mango kernel flour) exhibited the maximum emulsion stability of 74.08 ± 2.634%. Means for foaming capacity depicted the decreasing tendency as maximum foaming capacity of 35.03 ± 1.538% was recorded in T₀ (100% wheat flour). In comparison, the foaming stability of the flour blends prepared with 30% defatted mango kernel flour showed a minimum value of 30.49 ± 1.585%. Maximum foaming stability was recorded in flour blends containing 100% wheat flour (65.52 ± 2.689%).

Table 2. Functional properties of defatted mango kernel-wheat flour blends.

Treatments	Emulsion capacity	Emulsion stability	Foaming capacity	Foaming stability	Bulk density	Water absorption capacity	Oil absorption capacity
T0	49.57 ± 3.412^a	48.16 ± 1.712^d	35.03 ± 1.538^a	65.52 ± 2.689^a	0.76 ± 0.047^a	60.76 ± 2.391^e	81.81 ± 2.940^e
T1	48.53 ± 1.943^a	53.26 ± 0.192^c	34.84 ± 1.303^a	62.78 ± 2.534^ab	0.71 ± 0.018^ab	66.07 ± 3.111^d	89.61 ± 2.173^d
T2	47.04 ± 2.159^a	55.25 ± 2.226^c	27.01 ± 1.158^b	61.67 ± 1.820^b	0.67 ± 0.028^bc	69.01 ± 3.309^cd	91.84 ± 3.872^d
T3	42.30 ± 0.169^b	62.76 ± 1.350^b	21.88 ± 0.767^c	43.42 ± 0.797^c	0.66 ± 0.023b^c	71.94 ± 1.444^c	106.77 ± 1.030^c
T4	42.29 ± 3.081^b	65.04 ± 3.325^b	21.01 ± 0.468^cd	42.44 ± 0.919^c	0.65 ± 0.029^c	73.52 ± 2.659^bc	115.62 ± 3.836^b
T5	40.39 ± 1.854^b	73.18 ± 1.098^a	19.56 ± 1.023^d	30.72 ± 1.797^d	0.63 ± 0.034^c	77.67 ± 1.885^b	117.75 ± 4.607^ab
T6	38.99 ± 1.187^b	74.08 ± 2.634^a	17.39 ± 0.786^e	30.49 ± 1.585^d	0.44 ± 0.019^d	86.29 ± 2.511^a	123.87 ± 5.387^a
SS*	313.739**	1781.230**	942.432**	4107.059**	0.182**	1226.453**	4721.016**

Note. T0: Control 100% wheat flour (WF); T1: 5.0% defatted mango kernel and 95% WF; T2: 10% defatted mango kernel and 90% WF; T3: 15% defatted mango kernel and 85% WF; T4: 20% defatted mango kernel and 80% WF; T5: 25% defatted mango kernel and 75% WF; T6: 30% defatted mango kernel and 70% WF.^a–eThe means with similar letters mentioned in each column are statistically at par with each.*Significant effect of treatments.**Highly significant effects of treatments.

In the last phase, the product (cookies) was prepared and analyzed for various traits. The results pertaining to the diameter of cookies (Table 3) showed that addition of defatted mango kernel decreased the diameter significantly from 49.31 ± 0.777 mm (Control: 100% wheat flour) to 43.42 ± 0.817 mm (T6: 30% mango kernel meal). The maximum thickness (11.86 ± 0.223 mm) was observed in T₆ (30% mango kernel meal), while T₀ (5% mango kernel meal) exhibited a minimum thickness of 9.89 ± 0.156 mm. The spread factor of cookies prepared from various levels of defatted mango kernel treatments ranged from 49.84 ± 0.785 to 36.60 ± 0.689. The maximum spread factor was recorded in control cookies made from 100% wheat flour, whereas the lowest was in T₆. The means for hardness of the cookies indicated that maximum hardness was recorded in 10% mango kernel meal biscuits (2274.74 ± 94.669 G) followed by T5 (25% mango kernel flour), i.e., 2687.306 ± 17.622 G. The minimum value of hardness (1488.56 ± 32.237 G) was recorded in T6 (30% defatted mango kernel flour). Likewise, the fracturability of cookies prepared with mango kernel flour varied non-significantly and values were in the range of 76.66 ± 2.457 Mm to 74.31 ± 4.075 Mm (Table 3). The maximum fracturability was recorded in T2 (10% mango kernel flour). The minimum fracturability was recorded at 74.31 ± 4.075 Mm.

Table 3. Effect of defatted mango kernel supplementation on physical parameters and textural profile of cookies.

Treatments	Diameter	Thickness	Spread factor	Hardness	Fracturability
T0	49.31 ± 0.777^a	9.89 ± 0.156^e	49.84 ± 0.785^a	1594.38 ± 92.680	74.31 ± 4.075
T1	48.14 ± 0.792^ab	10.31 ± 0.170^d	46.69 ± 0.768^b	2073.72 ± 65.838	75.58 ± 3.000
T2	47.53 ± 0.564^bc	10.50 ± 0.125^d	45.28 ± 0.537^c	2274.74 ± 94.669	76.66 ± 2.457
T3	46.69 ± 0.929^cd	10.57 ± 0.210^d	44.18 ± 0.879^c	1733.04 ± 69.386	76.08 ± 1.637
T4	45.66 ± 1.017^de	10.92 ± 0.243^c	41.81 ± 0.931^d	1709.98 ± 28.562	75.72 ± 1.294
T5	45.12 ± 0.380^e	11.53 ± 0.097^b	39.12 ± 0.330^e	1770.60 ± 74.365	75.18 ± 1.693
T6	43.42 ± 0.817^f	11.86 ± 0.223^a	36.60 ± 0.689^f	1488.56 ± 32.237	74.97 ± 3.002
SS*	71.414**	8.662**	370.634**	1,358,210.842**	10.584ns

Note. T0: Control (100% WF); T1: 5.0% defatted mango kernel and 95% WF; T2: 10% defatted mango kernel and 90% WF; T3: 15% defatted mango kernel and 85% WF; T4: 20% defatted mango kernel and 80% WF; T5: 25% defatted mango kernel and 75% WF; T6: 30% defatted mango kernel and 70% WF; ns: non-significant effects of treatments.^a–fThe means with similar letters mentioned in each column are statistically at par with each.*Significant effect of treatments.**Highly significant effects of treatments.

The results for color values indicated that L* color tone of the cookies decreased from 70.80 ± 1.564 to 55.48 ± 0.931 (Table 4). The maximum lightness was recorded in the control, while minimum lightness was recorded in T6 (30% mango kernel flour). Further, a* values of the cookies varied from 5.12 ± 0.135 to 6.34 ± 0.116. The maximum reddish tonality was recorded in the control, while the minimum was recorded in T6 (30% mango kernel flour). The values for b* showed that increasing the amount of defatted mango kernel affected the said trait significantly and values were in the range of 16.86 ± 0.152 to 21.49 ± 0.156. Maximum b* color tone was recorded in the control biscuits and minimum values were recorded in T6 (30% mango kernel flour). The maximum hue angle of 46.21 ± 0.728 was observed in the control cookies, which was statistically at par (46.12 ± 0.759) with T5 (5% defatted mango kernel flour). The minimum value for hue angle was recorded for 42.08 ± 0.792 in biscuits prepared with 30% mango kernel meal.

Table 4. Effect of defatted mango kernel supplementation on color tonality of cookies.

Treatments	L*	a*	b*	Chroma	Hue
T0	70.80 ± 1.564	6.34 ± 0.116	21.49 ± 0.156	22.41 ± 0.353	46.21 ± 0.728
T1	68.56 ± 0.058	5.70 ± 0.095	20.94 ± 0.301	21.78 ± 0.358	46.12 ± 0.759
T2	62.70 ± 1.502	5.61 ± 0.080	19.76 ± 0.365	20.04 ± 0.238	45.40 ± 0.539
T3	61.53 ± 0.673	5.52 ± 0.106	18.70 ± 0.333	18.50 ± 0.368	45.68 ± 0.909
T4	56.34 ± 0.993	5.31 ± 0.130	18.57 ± 0.224	17.31 ± 0.386	42.98 ± 0.957
T5	56.24 ± 1.275	5.19 ± 0.061	17.76 ± 0.386	16.50 ± 0.139	42.89 ± 0.362
T6	55.48 ± 0.931	5.12 ± 0.135	16.86 ± 0.152	15.22 ± 0.286	42.08 ± 0.792
SS*	684.358**	3.068**	50.300**	131.434**	55.442**

Note. T0: Control (100% WF); T1: 5.0% defatted mango kernel and 95% WF; T2: 10% defatted mango kernel and 90% WF; T3: 15% defatted mango kernel and 85% WF; T4: 20% defatted mango kernel and 80% WF; T5: 25% defatted mango kernel and 75% WF; T6: 30% defatted mango kernel and 70% WF.*Significant effect of treatments.**Highly significant effects of treatments.

The nutritional composition of cookies indicated that there exist non-significant variations among the cookies prepared with varying levels of defatted mango kernel for moisture contents (3.46 ± 0.05% to 3.41 ± 0.055%). It is obvious from means presented in Table 5 that ash content increased with the addition of defatted mango kernel flour and the maximum ash content was recorded in cookies prepared with 30% defatted mango kernel–wheat flour blends (1.14 ± 0.019%) as compared to the least ash content of 0.84 ± 0.019% recorded in T₀ (control). Protein content decreased non-significantly with each increase in the amount of defatted mango kernel in cookies formulations from 6.62 ± 0.121% to 6.22 ± 0.164%. Contrarily, crude fiber contents increased significantly from 0.53 ± 0.008 in T₀ (100% wheat flour) to 1.05 ± 0.020 in T₆ (30% mango kernel flour supplementation). Nitrogen free extract is determined by the difference and the mean values of nitrogen free extract varied non-significantly from 63.75 ± 0.807 in T₅ to 64.36 ± 0.412 in T₁.

Table 5. Effect of defatted mango kernel supplementation on proximate composition (%) of cookies.

Treatments	Moisture	Ash	Crude protein	Crude fat	Fiber	NFE
T0	3.46 ± 0.051^a	0.84 ± 0.019^g	6.62 ± 0.121^a	24.46 ± 0.177	0.53 ± 0.008^g	64.09 ± 0.295
T1	3.53 ± 0.028^a	0.89 ± 0.001^f	6.50 ± 0.109^ab	24.12 ± 0.347	0.60 ± 0.010^f	64.36 ± 0.412
T2	3.45 ± 0.019^a	0.94 ± 0.023^e	6.41 ± 0.092^abc	24.46 ± 0.452	0.69 ± 0.008^e	64.04 ± 0.448
T3	3.46 ± 0.136^a	0.99 ± 0.011^d	6.38 ± 0.123^bc	24.36 ± 0.434	0.77 ± 0.015^d	64.03 ± 0.367
T4	3.43 ± 0.086^a	1.06 ± 0.019^c	6.37 ± 0.156^bc	24.32 ± 0.294	0.86 ± 0.019^c	63.96 ± 0.494
T5	3.59 ± 0.281^a	1.09 ± 0.025^b	6.31 ± 0.074^bc	24.30 ± 0.528	0.96 ± 0.008^b	63.75 ± 0.807
T6	3.41 ± 0.055^a	1.14 ± 0.019^a	6.22 ± 0.164^c	24.10 ± 0.217	1.05 ± 0.020^a	64.09 ± 0.310
SS*	0.9802^ns	0.8257**	0.3085*	0.39448**	0.6393**	0.5955^ns

Note. T0: Control (100% WF); T1: 5.0% defatted mango kernel and 95% WF; T2: 10% defatted mango kernel and 90% WF; T3: 15% defatted mango kernel and 85% WF; T4: 20% defatted mango kernel and 80% WF; T5: 25% defatted mango kernel and 75% WF; T6: 30% defatted mango kernel and 70% WF; NFE: Nitrogen free extract; ns: non-significant effects of treatments.^a–gThe means with similar letters mentioned in each column are statistically at par with each.*Significant effect of treatments.**Highly significant effects of treatments.

Lastly, sensory evaluation of cookies was carried out and the results showed that color scores of cookies prepared with the addition of defatted mango kernel flour varied significantly (Table 6). The maximum color score of 7.90 ± 0.348 was recorded in the control. The minimum color score was recorded in T₆ (30% defatted mango kernel flour) (6.80 ± 0.168). Likewise, addition of defatted mango kernel flour decreased the flavor of the biscuits. The maximum flavor was recorded in 7.80 ± 0.102 as compared to the minimum score for T6 (30% defatted mango kernel), i.e., (5.40 ± 0.136). Maximum texture was recorded in T₀ (7.80 ± 0.213), whereas the minimum sensory score for texture was recorded in 30% defatted mango kernel flour, i.e., 6.30 ± 0.117. The texture of cookies prepared with mango kernel flour varied significantly decreasing the flavor of cookies. The maximum value of the aroma in cookies was recorded at 8.00 ± 0.126 observed in T2 (10% defatted mango kernel flour). Significant changes occured in the cookies. The means for crispiness indicated that T₀ (Control) exhibited a maximum value 8.00 ± 0.239 while the minimum value 6.10 ± 0.257 was observed in T6 (30% defatted mango kernel) and significantly decreases when defatted mango kernel flour is added in the cookies. Mean values for overall acceptability of cookies was recorded at maximum value 7.90 ± 0.127 (100% wheat flour), whereas the minimum value 5.20 ± 0.096 was observed in T6 (30% defatted mango kernel). It was depicted from the results that cookies prepared with 15% and 20% defatted mango kernel were acceptable to consumers.

Table 6. Effect of defatted mango kernel supplementation on sensory characteristics of the cookies.

Treatments	Color	Flavor	Texture	Aroma	Crispiness	Overall acceptability
T0	7.90 ± 0.348^a	7.80 ± 0.102^a	7.80 ± 0.213^a	7.80 ± 0.180^a	8.00 ± 0.239^a	7.90 ± 0.127^a
T1	7.70 ± 0.068^ab	7.40 ± 0.225^b	7.80 ± 0.203^a	7.80 ± 0.167^a	7.80 ± 0.178^ab	7.80 ± 0.157^a
T2	7.50 ± 0.184^bc	7.20 ± 0.150^bc	7.40 ± 0.099^b	8.00 ± 0.126^a	7.80 ± 0.174^ab	7.50 ± 0.312^b
T3	7.35 ± 0.224^c	7.10 ± 0.158^c	7.20 ± 0.179^bc	7.80 ± 0.399^a	7.60 ± 0.178^b	7.40 ± 0.181^b
T4	7.30 ± 0.246^c	6.80 ± 0.204^d	7.00 ± 0.160^cd	6.40 ± 0.188^b	7.20 ± 0.185^c	6.90 ± 0.103^c
T5	7.20 ± 0.344^c	6.20 ± 0.221^e	6.80 ± 0.218^d	6.20 ± 0.196^b	6.40 ± 0.041^d	6.20 ± 0.194^d
T6	6.80 ± 0.168^d	5.40 ± 0.136^f	6.30 ± 0.117^e	5.60 ± 0.217^c	6.10 ± 0.257^e	5.20 ± 0.096^e
SS*	3.8107**	19.5857**	8.8429**	29.1429**	16.6714**	28.7429**

T0: Control (100% WF), T1: 5.0% defatted mango kernel and 95% WF, T2: 10% defatted mango kernel and 90% WF, T3: 15% defatted mango kernel and 85% WF, T4: 20% defatted mango kernel and 80% WF, T5: 25% defatted mango kernel and 75% WF, T6: 30% defatted mango kernel and 70% WF.

SS*: Sum of squares indicating the level of significance.^a–fThe means with similar letters mentioned in each column are statistically at par with each.**Highly significant effects of treatments.

Discussion

Globally, escalating population has resulted in higher demands for food commodities. However, resources are scarce for meeting the requirements along with poverty and hunger, which is prevalent in some regions of the globe. In the present research, efforts were directed at utilizing the mango kernel for coping with the problem of food security along with value addition. The defatted mango kernel contains higher amounts of protein, fiber, and ash contents. Mango kernel oil that is ~10–12% of total mango kernel weight has been removed. Moreover, the presence of lysine in the amounts of ~5.20 g/100 g in mango kernel protein bolsters its chances for utilization in composite flour technology for value addition. Maisuthisakul and Gordon (2009), while studying in Kenya, peeled, de-pulped, and destined/de-shelled the mangoes. They further crushed, sun-dried, and extracted the collected mango kernels using petroleum ether. Their results elaborated that mango kernels contain fats in the range of 8.5–10.4% along with protein, ash, and carbohydrate contents of 4.76–6.70%, 1.74–2.26%, and 71.90–76.28%, respectively. Anand and Maini (1997) and Garg and Tandon (1997) also reported similar values for these proximate constituents for mango kernel with the exception that they also reported the reducing sugars and tannins, i.e., 2.9% and 1.1%, respectively (Tandon and Kalra, 1989).

The present research was planned to utilize defatted mango kernel flour up to 30% to prepare composite flour blends that were further evaluated for their functional properties. The lower bulk density of mango kernel flour is due to the nature of mango kernel flour. Moreover, the defatting process can be credited for low bulk density, which results in porous texture of the defatted product (Akpata and Akubor, 1999) thus resulting in lower bulk density of flour blends. The lowering of bulk density is useful in preparation of some specialized products, e.g., complementary/weaning foods. Previously, Arogba (1999) studied the bulk density of mango kernel flour and observed the value of 0.50 to 0.51 cc/g. However, the results are not always the same as Akubor et al. (2000), who observed that addition of African breadfruit kernel in the flour blends does not change the bulk density significantly.

Water and oil absorption capacities are among the important functional properties from an industrial point of view since it improves mouth feel and flavor retention. The water binding ability of proteins does not always positively correlate to solubility of the proteins or other components. In response, the presence of hydrophobicity is an indicator of non-polar peptide residues on the surface of protein (Mohamed et al., 2007). Emulsifying activity of an un-conventional food is vital to judge its potential use in different food formulations as a functional agent. Protein, being the surface active agents, can form and stabilize the emulsion by creating electrostatic repulsion on an oil droplet surface. A general requirement of these emulsions is stability against coalescence during storage and utilization. According to Mwasaru et al. (1999), foaming properties are used as indices of the whipping properties of protein. Foam stability is important because the worth of whipping agents depends on their ability to maintain the whisk/whip as long as possible. Foaming capacity of protein depends upon its molecular flexibility, which is attributed to globular protein structure and surface tension. Foaming properties of bran protein concentrates are comparable with that of casein (Chandi and Sogi, 2007). Processing may affect protein solubility of extracted plant proteins; use of high alkaline conditions improves the solubility by dissociation and disaggregation of protein structure. Defatted wheat germ protein isolate possesses good nitrogen solubility, emulsion, and foaming properties (Agyare et al., 2009). The amino acid composition of mango kernel flour can be the major factor for the said variations in emulsifying and foaming properties of the flour blends.

The physical parameters include thickness, diameters, and spread factor. Some other parameters are also included in this category (i.e., indices of color tonality and textural analysis). According to the best of the authors’ knowledge, addition of defatted mango kernel in cookies formulation is tested for the first time in Pakistan through this research study. The results of the present exploration can be strengthened if we consider the study conducted by Mishra and Chandra (2012), which reported that the supplementation of wheat flour with soy flour and rice bran had reduced the diameter and consequently the thickness of cookies got increased. Overall, the data of width from this study is in conformity to those reported for cookies prepared by wheat–defatted wheat germ flour (Arshad et al., 2007) and wheat–cowpea bean flour (McWatters et al., 2003).

The competition among flour with other ingredients during dough mixing may affect the spread ratio. Khouryieh and Aramouni (2012) while studying the physical characteristic of flax seed flour fortified cookies reached a similar conclusion that spread factor of cookies decreases with increasing the level of flax seed flour. The color tonality of cookies was observed with the help of CIELab-Space that usually calculates the L* (lightness), a* (redness), and b* (blueness). The texture analysis of the cookies measured the two parameters, i.e., fracture-ability and hardness. The first parameter represents the force required to fracture the product and hardness represents the force or power required to penetrate the product. The differences in color tone and textural characteristics of the cookies are mainly due to defatted mango kernel flour and its functional properties.

The chemical composition of the cookies is again dependent on the ingredients used in the formulations. The defatted mango kernel contains higher amounts of ash and fiber contents; thus, ash and fiber contents of cookies increased as a function of treatments. Defatted mango kernel flour contains less amounts of proteins and moisture; thus, a decreasing tendency was observed in these traits with addition of defatted mango kernel flour. The results of Arogba (1999) are also in line with the present study. The results can be further justified with the findings of Muchiri et al. (2012).

Sensory evaluation is an important standard for quality assessment of a new product and is usually performed towards the end of the product development to meet the consumer requirements. In the present study, decrease in crispiness scores on increasing DFMK level above 20% has been observed, which is supported by the study of mentioned researchers. Thus, the present study recommended that cookies prepared up to 15–20% defatted mango kernel flour blends are analogous to that of wheat flour cookies but beyond this limit the cookies will not be acceptable by the consumers (Khouryieh and Aramouni, 2012). Changes in color are due to caramelization and Millard reaction relating the interaction of reducing sugars with proteins. Present results are supported by the findings of Haque et al. (2002) as they observed a decrease in flavor scores of cookies and biscuits by the addition of fibrous ingredients, such as corn, rice, oat, and wheat bran, to the formulation beyond 20%. Rababah et al. (2006) evaluated the cookies supplemented with soy protein isolates and observed a significant effect of soy protein supplementation on the taste of the cookies. Similar to the present study, Mishra and Chandra (2012) also concluded that the flour blends containing soy flour and rice bran at the 15% level each can enhance the overall acceptability of the biscuits. Findings of the present study are corroborated with the research investigation of Arshad et al. (2007) who observed a declining trend in quality score for texture. Thus, the present study recommended that cookies prepared up to 15–20% defatted mango kernel flour blends are analogous to that of wheat flour cookies but beyond this limit the cookies will not be acceptable by the consumers.

Conclusions

The utilization of defatted mango kernel is beneficial for developing economies like Pakistan to ensure food security. The results were conclusive that defatted mango kernel can be used to replace wheat flour at 15% and 20% with significant consumer acceptability. In the future, wheat and defatted mango kernel flour blends can be prepared for utilization in other bakery products. Moreover, extraction of principal ingredients, e.g., starch and proteins, for value addition are among the points presented in the current research.

Funding

The authors gratefully acknowledge the Higher Education Commission (HEC), Pakistan for providing funds for carrying out the present research.

Additional information

Funding

The authors gratefully acknowledge the Higher Education Commission (HEC), Pakistan for providing funds for carrying out the present research.