REGULAR ARTICLE DEVELOPMENT OF FIBER AND MINERAL ENRICHED COOKIES BY UTILIZATION OF BANANA AND BANANA PEEL FLOUR

An experimental study was designed to formulate ready to eat cookies by incorporating banana and banana peel flour which is normally unused in Bangladesh but contains excellent amount of nutrients especially dietary fiber, essential vitamins and minerals. Cookies were prepared by replacing 5 % (sample-1), 10 % (sample-2) and 15% (sample-3) of wheat flour with banana and banana peel flour. The proximate analysis and sensory parameters of those cookies were compared with control cookies where no banana and banana peel flour were added and designated as normal cookies (0% substitution). Functional properties were also evaluated and a significant difference found (P<0.05) in WHC, OHC, swelling capacity, emulsion activity, emulsion stability and flour dispersibility in banana peel flour when compared to wheat flour. On proximate analysis of cookies, significant variation (P<0.05) was also observed in protein, ash, fiber and carbohydrate content of banana and banana peel flour cookies in a comparison to normal cookies. The increasing the substitution of banana and banana peel flour in cookies increased the ash and crude fiber content remarkably. About 15% substitution of banana and banana peel flour in cookies increased 93.25% crude ash (mineral) and 197.56% crude fiber than normal cookies. Energy values of the cookies were also evaluated and ranged between 480 Kcal and 513 Kcal per 100 g, with sample-3 cookies having the lowest value. In conclusion, the addition of both banana and banana peel flour in cookies by replacing 10% wheat flour were more acceptable with all quality characteristics.


Preparation of banana (unripe) peel flour
At first the bananas were collected and washed with water to remove all harmful ingredients. After peeling, the peels were sliced and dipped for ten minutes in 0.5% (w/v) citric acid solution to reduce enzymatic reaction. After drained out, the sliced were then dried in oven at 50 0 C for 16-20 hrs. The dried banana peels were then amalgamated by using a commercial blender and passes through 60 mesh screen to obtain fine banana peel flour. The dried banana peels powder were then stored in airtight packet at ambient temperature.

Formulation of cookies
Hydrogenated vegetable oil (80g) and sugar (200g) were uniformly mixed together for 3 minutes at a speed of 10 and 8 rpm by rotary mixture machine. Then other ingredients such as milk, egg, salt and baking powder (composition shows in table-1) were mixed together at a speed of 6 rpm. After mixing above ingredients then added vegetable oil and uniformly mixed for 3 minutes at a speed of 8 rpm. Finally wheat flour, mashed banana and banana peel flour were added and uniformly mixed well together. The batter were rolled out and cut uniformly and send it to baking chamber and baked at 150 0 C temperatures for 15-16 minutes. When the color of cookies turned to light brown color it indicates the finished baked cookies. After baking, cookies were then cooled and packed in plastic packets. The ready to eat cookies were than stored at room temperature for further analysis.

Analysis of functional properties of banana peel and wheat flour
Functional qualities such as water and oil holding capacity, swelling capacity, emulsion activity and stability and also flour dispersibility of banana peel flour and wheat flour were analyzed. About 1g of flour sample and 25ml of water were taken in a 30 ml capacity test tube and allowed for 15 minutes at room temperature. The tube was then centrifuge for 20 min at 3000 rpm and drained off the supernatant. The weight of the residue after drained off the excess water was the water holding capacity of flour and determined as g of water/g dry sample (Rodriguez-Ambriz et al., 2008).

Oil holding capacity (OHC)
About 1g of flour sample and 25 ml of commercially olive oil were taken in a 30 ml capacity test tube and centrifuged the mixture at 3000 rpm for 20 minutes. The weight of the residue was recorded after decanted the free oil. OHC was calculated as gram of water per gram of dry sample (Rodriguez-Ambriz et al., 2008).

Swelling capacity (SC)
The swelling capacity of flour sample was evaluated by Okaka and Potter (1977) method.

Emulsion activity (EA) and emulsion stability (ES)
The emulsion activity and emulsion stability of sample were evaluated by Yasumatsu et al., (1972) method.

Flour dispersibility (FD)
About 10 g of sample were mixed with distilled water in a cylinder to make a final volume of 100ml, stir vigorously and then allowed it to settle. After 3 hours, settled particles volume was recorded. And finally percentage of flour dispersibility (Kulkarni et al., 1991) was calculated by subtracted it from 100.

Sensory evaluation of cookies
The sensory evaluation of prepared cookies was carried out by 15 panel members (trained on sensory evaluation) from different food industries in Bangladesh. The panel members evaluated each sample of the cookies for color and appearance, texture & consistency, taste, aroma and overall acceptability. The samples were rated by 9 point hedonic scale (9-like extremely, 8-like very much, 7-like moderately, 6-like slightly, 5-neither like or dislike, 4-dislike, 3-dislike moderately, 2-dislike very much, 1-dislike extremely). Score were collected and analyzed statistically. The score 6 or more were considered as acceptable for the consumer acceptability.

Proximate analyses of composite flour and cookies
Proximate analyses such as moisture, ash, fat, protein and crude fiber of the sample were analyzed by using AOAC-2000 method (AOAC, 2000). Energy value of the sample was calculated by using factor method described by by Chinma and Igyor and the Atwater factor method is [(9xfat) + (4xcarbohydrate) + (4x protein)] (Chinma and Igyor, 2007)

Physical characteristics of cookies
Physical property of cookies is an important attributes which plays an important role to determine the consumer acceptability. AACC method was used to determine the diameter and thickness of the cookies (AACC, 2000). The Spread Factor (SF) of the cookies was determined according to the following formula: SF = (Diameter/Thickness × Correction Factor) × 10, where correction factor was 1.0 in this study at constant atmospheric pressure.

Statistical analysis
All the sample analyses were performed in triplicate and descriptive statistics were analyzed by using SPSS (Statistical Package for the Social Science) software package version 16.0 (SPSS Inc., Chicago, IL, USA) for all variables. All of the values are expressed as the mean of three individual replicates ± Standard Error Mean (SEM). All data were subjected statistically to ANOVA test (analysis of variance) and mean value were separated using Tukey's test (Steele Torrie, 1980). Differences between mean values were considered to be significant at p < 0.05.

RESULTS AND DISCUSSION
Chemical composition of raw material, different functional properties of banana peel flour and wheat flour, physical and nutritional properties of cookies were analyzed by using standard procedures. Determination of functional properties was important as it show the interaction among the composition, confirmation, structure, and physicochemical properties of protein and other food components (Kinsella, 1976). The effect of incorporation of different proportions of banana peel flour on nutritional and sensorial properties of cookies were also analyzed.

Chemical composition of raw materials
The raw materials, i.e., banana, banana peel flour and wheat flour were analyzed for chemical composition and the data are presented in table 2. Moisture content is one of the important indicators which influence shelf life, changes of flavor and enzyme activity and storage stability of flours. Research findings suggest that flours having more than 14% moisture content or 0.7 to 0.9 aw are prone to mold growth and infestation by insects (Manley, 2000;Ayub, 2003). Banana pulp had the highest moisture content (74.77%) whereas banana peel flour contained only 9.40% moisture and wheat flour had 10.90% moisture. These results are quite similar to the results found in sweet potato flour by Singh et al., (2008). Moisture content in flour is mainly affected by amount of moisture used for wheat conditioning and also for type of wheat milling. Another functional component of flour is percentage of protein content by which flour specification, flour condition and quality of the product depends. Protein content varies from 6-20% in different varieties of wheat (Kent, 1983).  et al., 2000). The high crude ash content of banana peel flour can be attributed to relatively high mineral content. Banana peel flour is rich in iron, zinc, calcium, magnesium, phosphorus, and potassium (Michel et al., 2016). Similarly, banana is rich in potassium (Bezemek, 2015). The crude fiber content was also significantly high in banana peel flour (8.82%) than banana (1.34%) and wheat flour (0.34%). The high fibers content in banana peel flour (11.81g/100g dry peel) also observed by Romelle et al., (2016). Banana peels contain both soluble and insoluble dietary fiber. Happi Emaga et al., (2007) found insoluble dietary fiber; cellulose 7 to 12 g/100 g, lignin 6.4 to 9.6 g/100 g and hemicelluloses 6.4 to 8.4 g/100 g, in banana peels and also found soluble dietary fiber that is pectin 13.0 to 21.7 g/100 g. High fiber diet are very important for adult, in that, it promotes the wave-like contraction that helps to move food through the intestine and also easing the passage of waste and expanding the inside walls of the colon to make an anti-constipation effect (Eromosele and Eromosele, 1993). Crude fibers are known to aid digestion, absorb water and make stools larger and softer so as prevent constipation (Ayoola and Adeyeye, 2009). The high level of fiber in the plantain suggests that it is capable of promoting digestion as fibers are known to aid and speed up the excretion of wastes and toxins from the body, and also prevent colon cancer as it prevents waste or toxins to stay in the intestine for too long (Ogbonna et al., 2016) . As carbohydrate content of flours calculated by difference method, it varied from 19.09 to 77.94%.

Functional properties of wheat and banana peel flour
Test of functional properties is very important because it describes how ingredients behave during preparation and cooking. It also describes how they affect the quality of finished food product in terms of looks, tastes, and feels. WHC, OHC, SC, EA, ES and FD are important properties of flour both of physicochemical and technological point of views. WHC is the amount of water that can be bound in fiber until the application of external force. In this study, a significant (P<0.05) difference was found in WHC of banana peel flour and wheat flour. Mean WHC of banana peel flour found slightly higher (4.58 g/g dry sample) than WHC of wheat flour (3.19 g/g dry sample) ( Table-3). These findings are quite low compared to dietary fiber found by Larrauri et al., (1996) in mango (12 to 15 g water/g dry sample) and mango peel (11 to 12 g water/g dry sample). Whereas, the mean OHC of wheat flour was found slightly higher that was 0.63 g/g dry sample than OHC of banana peel flour that was 0.44 g/g dry sample which was also statistically significant (P<0.05). These findings are quite similar to the results observed by Kaushal et al., (2012). Another functional property of flour is swelling capacity and it depends on variety, size of particles and types of processing methods. A significant (P<0.05) difference was found in swelling capacity of wheat flour and banana peel flour. Swelling capacity of wheat flour and banana peel flour found 15 ml and 13.50 ml respectively. Emulsion Activity and Emulsion Stability both were found higher in wheat flour (41.20% and 35.10%) than banana peel flour (36% and 30.50%) respectively which was statistically significant (P<0.05). A significant (P<0.05) variation was found in flour dispersibility test of banana peel flour and wheat flour. About 61% flour dispersibility found in banana peel flour whereas 66.56% found in whole wheat flour.

Nutritional values of the cookies
According to Table 4, with increasing the substitution of banana and banana peel flour, the moisture content was increased in cookies. Moisture content ranged from 2.28% to 3.35% and highest moisture content were observed in 10% banana and banana peel flour cookies. Moisture content increased with the incorporation of banana and banana peel flour which was statistically significant (P<0.05). The water binding capacity of banana peel flour found quite higher than the water binding capacity of wheat flour. These findings are quite similar to the study of Bertagnolli et al. (2014), who found that cookies made from composite flour that contain guava peel flour has moisture ranged from 2.7 and 4.9%. Maximum variation in moisture content was found 2.47 to 8.75% in commercially available biscuits whether fat content varies between 1.04 to 14.82% (Semwat et al., 1996). The substitution of banana and banana peel flour to refined wheat flour at levels of 5-15% showed a lowering effect on the protein contents of the cookies (Table 4). A statistically significant variation (P<0.05) was also found in protein content of all sample cookies. Possible reason for this may be higher percentage of protein in wheat flour than banana and banana peel flour. This finding is quite lower than the cookies made with 100% pigeon pea flour (12.97% protein) reported by Okpala and Okoli (2011). The protein content found in banana and banana peel flour cookies was close agreement to the cookies of taro-wheat blend (Ojinnaka. 2009).
There was no major distinction found in the fat percentage of the cookies made by substitution of 5 to 15% banana and banana peel flour. There was no significant variation (P>0.05) found in cookies except sample-2 and sample-3 cookies. A noteworthy difference (P<0.05) was found in ash content of all sample cookies and it increased from 1.63 to 3.15%. The maximum ash content (3.15%) was found in 15% banana and banana peel flour cookies followed by 10% ( FAO and WHO (1994), as they suggested not to add more than 5 g dietary fiber per 100 g dry matter. Carbohydrate content of prepared cookies was calculated by difference method and there was no remarkable variation found in carbohydrate content of cookies. Carbohydrate content found highest in 15% banana and banana peel flour cookies followed by 5% banana and banana peel flour cookies. These results are in close relation with the cookies made from cocoyam-wheat blends (Ojinnaka, Akobundu and Iwe, 2009).
The energy values of the prepared cookies ranged from 480 to 513 Kcal /100 g. The slight variation on energy value due to the variation of protein and fat content of cookies outweighs the decrease in carbohydrate content.

Physical characteristics of cookies
The cookies were also analyzed for their physical properties such as thickness, diameter and spread factor shown in table 6. A significant variation (P<0.05) observed in diameter and thickness of the cookies. The cookies diameter ranged from 5.75 cm to 5.86 cm. while thickness of the cookies ranged from 1.22 cm to 1.42 centimeter. The highest thickness was found in cookies made by without addition of banana and banana peel flour. As spread factor was calculated from diameter and thickness of the cookies there was a significant variation (P<0.05) found in spread factor. The highest spread factor was found in 10% banana and banana peel flour cookies and lowest one found in normal cookies. A similar inclination in cookies observed by Chinma and Gernah (2007) made from mango, cassava and soybean composite flour. Higher spread ratios in cookies having are considered the most desirable (Kirssel and Prentice, 1979).

Sensory evaluation of functional cookies
Sensory evaluation of the cookies depends on its appearance, color, flavor and aroma, texture and overall acceptability taste of the sample. All the panelists were having excellent capability (trained on sensory evaluation) to evaluate the sensory evaluation of banana and banana peel flour cookies. Table 7 shows the sensory evaluation score of functional cookies supplemented with different level of banana and banana peel flour. Besides normal cookies, sample-2 cookies liked very much by the panelist (score 7.5). On the other hand, 15% substitution of banana and banana peel four got the lowest score on color and appearance. A statistical significant variation (P<0.05) found on color and appearance score. Increasing the supplementation of banana peel flours with wheat flour increased the darkness of cookies may be the prime reason for find objectionable of the cookies.

Texture and consistency acceptability
Texture and Consistency depends upon mainly the rate of development of the dough and the proportion of sugar used. Table 7 shows that the normal cookies and sample-1 got the highest score on Texture and Consistency of cookies (score 7) and sample-2 got the second highest score on Texture and Consistency. The softness of the texture of normal, sample-1 and sample-2 cookies may be the main reason for getting the highest score by the panelist. Similarly the hardness of sample-4 than normal cookies may be the reason for getting lowest score. The result revealed that, increasing the substitution of banana and banana peel flour increases the hardness of cookies.

Taste acceptability
Taste is also influenced by the quality of the raw materials used in the processing unit of cookies. No significant variation (P>0.05) found in taste acceptability taste. About 15% substitution of banana and banana peel flour cookies got the lowest score on taste acceptability taste.