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Journal of Scientific and Industrial Studies, Volume 15, Number 2, 2020 Printed in Nigeria. All Right Reserved. ISSN: 1117-1693 copyright©2020 Duncan Science Company

PROCESSING AND CHARACTERISATION OF DRIED UNRIPE PLANTAIN FLOUR

*K.C. Idahosa1, F. E.Adebanjo1, and H.I.Nwanma2.

1 Chemical Science Department, 2 Biological Science Department Yaba College of Technology, Yaba, Lagos State, Nigeria

ABSTRACT

Four treatment methods were employed using two dehydration methods (sun-drying and oven-drying) for each treated batches of unripe plantain pulp (Musa paradisiaca), to produce physical variations in their colors. Dehydration of the unripe edible portion of the plantain was completed using sun-drying (4-5 days to constant weight) and oven-drying (at temperature 550C for 36 hours) and the dried products were milled and sieved to fine flour. The flours obtained were evaluated in their physical characteristics showing the inhibition of browning in unripe plantain pulp before milling. The results indicate that the treatment methods and dehydration processes affected significantly (p≤0.05) the proximate ( Fibre content, ash content, carbohydrate content, crude protein content, crude lipid content and moisture content) and functional properties (oil absorption capacity, solubility, water absorption capacity, bulk density and swelling power) of the flours. Since the plantain fruits are important crops in tropical and subtropical regions, the preparation of plantain flours with differences in their functional properties from the perishable pulp makes these flours readily available as ingredients for different foods and as instant or quick cooking food. Keywords: Unripe plantain flour, Browning Reaction, Functional Properties, Bulk Density, Absorption Capacity, Fibre Content, Ash Content.

INTRODUCTION & LITERATURE REVIEW Plantain (Musa paradisiaca) belongs to the genus Musa in the family Musaceae. It is a giant perennial herb and cultivated in many tropical and subtropical countries of the world, constituting a major agricultural produce hence one of the major staple foods in producer countries. Ranking third after yam and cassava for sustainability in Nigeria (Ogundareet al., 2015). It is used as a source of starchy staple food for millions of people in Nigeria. The annual world production of plantain and banana is estimated at 75 million tons (John and Marchal, 1995). Traditionally, bananas are usually eaten raw as dessert while plantain and cooking bananas on the other hand are traditionally grown for cooking as part of a staple diet, or for processing into more durable products such as flour that can be stored for later use (Dadzie, 1995; Wainwright and Burdon, 1991). Plantain, being a seasonal fruit, is abundant at a particular period of the year, when they are in season and are scarce during the off season (i.e out of season). Since this crop is highly perishable after harvest, drying is a common practice for preserving them in order to make their product available throughout the year (Agoreyoet al., 2011). Mature unripe plantain pulp is rich in nutrients such as iron, potassium, calcium, zinc, sodium, vitamin A, but low in protein and fat (Adenijiet al., 2006), the water content in unripe plantain is about 61% and the water content increases on ripening to about 68%. The increase in water is presumably due to breakdown of carbohydrates (sugars, starches and fibres) during ripening process of plantain, where carbohydrates are broken down into their constituent parts to produce energy to run cellular activities, thus keeping the cells of fruit alive. Starch is present in the unripe plantain mainly as amylase and amylopectin and this is hydrolysed to sucrose, fructose and glucose during the ripening stages (Zakpaa et al., 2010). Corresponding Author: K.C. Idahosa kcidahosa@gmail.com

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Processing and Characterization of Dried Unripe Plantain Flour In most West African countries including Nigeria, the unripe plantain pulp is traditionally processed into flour after Sun-drying. Unripe plantain is roasted on open charcoal flame and eaten with other delicacies such as roasted pumpkins, avocado, roasted peanut, fish or meat, and sometimes in combination with hot stew, sauce or peanut butter (Ukhum and Ukpebor, 1991). At other instances, unripe plantains are harvested, peeled, sliced and sundried, then pounded and ground to obtain plantain flour. The pap prepared from this plantain flour is fondly called “Amala” among the Yorubas in Nigeria and “Foufou” in Cameroun. This is usually prepared by mixing unripe plantain flour with boiling water to an elastic pastry and eaten with various choices of sauces (Mestersset al., 2004). Since this tropical crop is seasonal, and it is hardly contained during the yearly harvest season due to spoilage, leading to post harvest losses. Consequently, it is insufficient during the off season periods, thereby creating the need for some preservation techniques so that this nutritious food material would be available in some form all the year round. This makes it necessary for it to be processed within the shortest period of time following harvest to reduce or if possible completely eliminate post-harvest losses. Farmers are compelled to process their harvest in order to increase the availability of the staple food product throughout the year, thereby ensuring food security and also providing for themselves a means of financial income during the off season periods (Habouet al., 2003; Eklouet al.,2006). Plantain grouped along with tubers, constitutes a whopping sum of 22.60% of the total per food commodity expenditure profile for Nigerian households (National Bureau of Statistics, 2010). However, postharvest loss is a major problem limiting the production of plantain and banana in Africa due to unavailability of established storage techniques or facilities that can guarantee longer shelf life (Adenijiet al., 2008). Sun-, oven-, and solar drying are the popular preservation technique for this food crop. Sun drying being the most common practice (Matazu and Haroun, 2004). These three drying methods utilize heat to remove water from food by evaporation. These food crops when dried are processed to produce flour which can be reconstituted to form paste or dough (Emperatrizet al., 2008). Most plantain foods are eaten as boiled, fried, or roasted. High level of potassium in plantain makes it an important raw material for indigenous soap manufacture especially the unripe plantain peels which also finds application in the amendment of soil acidity (Izonfuo and Umuaru, 1988). Rahman et al., (1963) reported on the utilization of flour from unpeeled green plantain in poultry feed and concluded that no ill or toxic effect could be observed in chicks fed with the flour. Unripe and peeled plantain meal is usually consumed by diabetic patients because it contains high amount of fiber which helps to aid the digestion process and empty the bowels easily thereby reducing post prandial glucose level (a measurement of blood glucose after a meal containing an amount of carbohydrate) (Oboh and Erema, 2010). Pere–Sira (1997) had also indicated the use of plantain as component of baby food along with cowpeas and soybean during weaning to provide nutrients and proteins for infants. Plantain when dried becomes brown in color due to chemical reactions that takes place within. It is called Browning Reactions. Complex chemical reactions occurring in foods, leading to formation of brown colour, be it as a result of processing or storage of such foods. Though there are many different ways food color chemically changes over time, food browning in particular falls into two main categories which are the Enzymatic and the Non enzymatic browning processes (Kaanane and Labuza, 1989). In the case of plantain flour, it is enzymatic browning that occurs during the sun-drying process. As the name suggests, Enzymatic Browning occurs via the activities of enzymes such as phenolase/polyphenolase oxidase, catalyzing oxidation during sun-drying of the peeled unripe plantain pulp. This implies that the sun-dried pulp becomes brown, hence the flour obtained after grinding the dried pulp is brown as well(Kaanane and Labuza, 1989).

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Journal of Scientific and Industrial Studies, Volume 15, Number 2, 2020 To some people, this brown coloured pap meal (amala) is not appealing, thus discourages such people from eating the pap made from sun-dried unripe plantain flour. This research project aim is to inhibit this browning reaction while processing the unripe plantain pulp, hence produce plantain flour (from dried unripe plantain) that is not brown; rather it retains the colour of the fresh unripe plantain pulp. In so doing, offers options or alternatives to consumers of dried plantain flour and also add value to this agricultural product.

MATERIALS AND METHODS In the course of this research work, the following activities were carried out. Bunches of unripe plantain fruits were purchased from Owode-Mile 12 plantain depot, Owode market, Ikorodu road, Lagos State and was packed into a clean bag.

SAMPLE PREPARATION AND DRYING OF UNRIPE PLANTAIN PULP All materials and equipment used in the sample preparation and drying of unripe plantain pulp are listed as follows: Plastic bowl Sieve Stainless kitchen knife Electric oven Non- absorbent flat tray Electric blender Lime juice (Ascorbic acid) Distilled water Mesh net (size 0.3mm) Electric kettle Mortar and pestle

Unripe plantain fruits were peeled using a stainless kitchen knife and the pulps were rinsed with some clean water and dipped into a distilled water to prevent browning. The plantain pulps were sliced into slim round sizes of about 3mm thick and were divided into four equal batches for the following treatments. Batch A: Non treated unripe plantain pulp (sun-dried and oven-dried) Batch B: Blanched Only unripe plantain pulp (sun-dried and oven-dried) Batch C: Treated Only unripe plantain pulp (sun-dried and oven-dried) Batch D: Blanched and Treated unripe plantain pulp (sun-dried and oven-dried)

Procedure for Batch A: Non Treated The plantain pulp in this batch were only rinsed in distilled water and was further divided into two equal parts, one group for sun-drying and the other for oven-drying respectively. The sliced pulp for sun-drying was spread on a non-absorbent flat tray and dried under the sun for 4-5 days until it was crispy dried to constant weight. The other portions of the sliced plantain pulp were dried in a regulated electric oven at temperature of 550C for 36 hours to constant weight. Both the sun-dried and oven-dried plantain pulp were milled into fine flour separately using an electric blender and sieved with a mesh net size of about 0.3mm. The flour obtained from each process methods were stored in a labeled air tight container separately and kept for further analysis

Procedure for Batch B: Blanched Only The sliced plantain pulp in this batch was blanched, as it was dipped into hot water at a temperature of 72oC for 2-3 minutes, sieved and immediately poured into an iced water to reduce its high temperature and stop it from being cooked. The blanched plantain pulp was then further divided into two parts, one portion for sun-drying and the other for oven-drying. The sliced blanched pulp for sun-drying was spread on a non-absorbent flat tray and kept under the sun for 4-5 days until it was crispy dried to constant weight.

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Processing and Characterization of Dried Unripe Plantain Flour The other part of the sliced blanched pulp was dried in a regulated electric oven at temperature 550C for 36 hours to constant weight. Both sun-dried and oven-dried plantain pulp were milled into fine flour separately using an electric blender and were sieved with a mesh net size of about 0.3mm. The flour obtained from each process was stored in a labeled air tight container separately and kept for further analysis.

Procedure for Batch C: Treated Only Sliced pulp in this batch were soaked into lime juice (ascorbic acid) for 10 to 15 minutes and then sieved to drain. The treated sliced pulp were further divided into two equal parts, one portion for sun-drying and the other for oven-drying respectively. The sliced treated pulp for sun-drying was spread on a non-absorbent flat tray and kept under the sun for 4-5 days until it was crispy dried to constant weight. The other part of the sliced treated pulp was dried in a regulated electric oven at temperature 550C for 36 hours to constant weight. Both sun-dried and oven-dried plantain pulp were milled into fine flour separately using an electric blender and were sieved with a mesh net size of about 0.3mm. The flour gotten from each drying methods were stored in a labeled air tight container separately and kept for further analysis.

Procedure for Batch D: Treated and Blanched Sliced pulp in this batch were first blanched by dipping into hot water of temperature 72o C for 2-3 minutes, sieved and immediately poured into ice water to cool its temperature down rapidly and to avoid it being cooked. Then, the blanched pulp was drained and soaked into lime juice (ascorbic acid) for 10 to 15 minutes and then sieved to drain. The blanched and treated plantain pulp was then further divided into portions, one for sun-drying and the other for oven-drying. The sliced blanched and treated pulp for sun-drying was spread on a non-absorbent flat tray and kept under the sun for 4-5 days until it was crispy dried to constant weight. The other part of the sliced blanched and treated pulp was dried in a regulated electric oven at temperature 550C for 36 hours to constant weight. Blanched and treated plantain pulp was milled into fine flour separately using an electric blender and was sieved with a mesh net size of about 0.3mm. The resulting flour from each drying process was stored in a labeled air tight container separately and kept for further analysis. In general, the preparation of unripe plantain flour can be summarized using a flow chart. Matured Unripe plantain Washing Peeling Slicing Apply Different Treatment methods (Non-treated, blanched only, treated only and blanched and treated) Drying (oven dried at 55oC and sun dried to constant temperature.) Milling Sieving Fine Unripe Plantain Flour Figure 1: Flow Chart Showing the Preparation of Unripe Plantain Flour

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Journal of Scientific and Industrial Studies, Volume 15, Number 2, 2020 Determination of moisture content: The method described by Association of Official Analytical Chemists (AOAC) (2005) was adopted. The crucible was properly washed and allowed to dry in an electrical oven at 110ºC for about 10 min to a constant weight. The crucible was allowed to cool in a desiccator for 30 min and weighed (W1). 2.0 g of TOOD unripe plantain flour sample was accurately weighed into the crucible and reweighed (W2). The crucible containing the sample was placed in an oven maintained at 110ºC for 14 hrs. This was removed and transferred to desiccator to be cooled, finally weighed (W3). The percentage moisture content was calculated as follows: Percentage moisture content = 100 - [(w2-W1) x 100]

1 W3-W1

Weight of empty crucible -W1 Weight of crucible + sample before drying -W2 Weight of crucible + sample after drying -W3 This procedure was followed in the determination of the Carbohydrate Content for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Determination of Ash content: The AOAC (2005) method was adopted for this process. The porcelain crucible was washed and dried in an electric oven to a constant weight at 100ºC for 10 min. It was allowed to cool in a desiccator, and then weighed (W1). 2.0 g of TOOD unripe plantain flour sample was weighed into the previously weighed porcelain crucible and reweighed (W2). The crucible containing the plantain flour was transferred into a furnace, which was set at 550ºC for 8 hours to ensure proper ashing. This was then removed and allowed to cool in the desiccator then finally weighed (W3). The percentage ash content was calculated as follows: Percentage ash content = (W2 - W1) x 100 W3 - W1 1 Weight of empty crucible -W1 Weight of crucible + sample -W2 Weight of crucible + ash -W3 This procedure was followed in the determination of the Ash Content for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Determination of Crude Fibre: The method described by AOAC (2005) was adopted for this process. 2.0g of TOOD plantain flour sample (W0) was weighed into round bottom flask, 100 mL of 0.25M Sulphuric acid solution was added to the sample in the flask, and the mixture was boiled under reflux for two hours. The hot solution was quickly filtered under suction. The residue was thoroughly rinsed with hot water and was constantly tested using pH paper until it became acid free. The residue was transferred into a round bottomed flask and 100 mL of hot 0.3M Sodium hydroxide solution was added and the mixture was boiled again under reflux for one hour and filtered quickly under suction. The insoluble residue was washed with hot water and tested constantly with a pH paper until it was base free. This processes of washing the residue to be acid free and base free was to make the residue neutral. The residue was dried to a constant weight in an oven at 100ºC for 2hours, cooled in desiccator and weighed (W1). The weighed residue was then incinerated (burned to ashes) in a furnace, and reweighed (W2).

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Processing and Characterization of Dried Unripe Plantain Flour Percentage crude fibre content was calculated as follows: Percentage crude fibre = (W2-W1) x 100 W0 1 Weight of initial flour sample -W0 Weight of residue -W1 Weight of ash -W2 This procedure was followed in the determination of the Crude fibre for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Determination of Nitrogen and Crude Protein: Micro Kjeldahl method as described by AOAC (2005) was used. 0.5g of TOOD flour sample was weighed and placed on a nitrogen free filter paper, then folded and dropped into a Kjeldahl digestion flask. 1.0g of Na2SO4( Sodium sulphate) followed by 0.1g of CuSO4 (Copper sulphate) (digesting mixed catalyst) and 25mL of Conc. H2SO4 (Sulphuric acid)was added sequentially to the flour sample in the digestion flask. The mixture in the digestion flask was transferred to the Kjeldahl digestion apparatus; the heater was regulated at a temperature of about 1500C, below the boiling point of H2SO4 until frothing (foaming or bubbles) ceased. The mixture was then boiled vigorously as temperature was increased, until a clear pale blue color was obtained.

Organic N + H2SO4 → (NH4)SO4 + H2O + CO2 + other sample matrix byproducts

The digested mixture was allowed to cool then transferred into 250cm3 volumetric flask and diluted with distilled water to make up 250cm3. 50ml aliquot of the digested mixture was introduced into the distillation jacket of the Micro Steam Distillation Apparatus that was connected to the main condenser, as the water in the distiller flask boils. 50mL of 40% NaOH was added to the digested mixture in the distillation jacket. (NH4)2SO4 + 2NaOH → 2NH3 + Na2SO4 + 2H2O 50mL of 2% Boric acid was measured into the 250mL conical flask, four (4) drops of mixed indicator (a combination of Methyl Orange and Methyl Blue solution) was added. The conical flask containing the mixture was placed on the distillation apparatus having an outlet tube inserted into a conical flask to distill NH3 gas. The distillation was carried out until 25mL of the NH3 distillate was trapped into the Boric acid solution and color change from Wine to Yellow color.

NH3(g) + H3BO3(aq) → NH4+ H2BO-

3 + H3BO3

wine pale green The distillate was then titrated with 0.1M HCl to give a Wine color again and the titre value was recorded. Percentage nitrogen and crude protein was calculated as follows: Percentage nitrogen = Titre value x 0.1 x 14 x 250 x 100 Weight of initial sample x 1000 x 25 Percentage protein = Percentage nitrogen x 6.25 This procedure was followed in the determination of the Nitrogen and Crude Protein for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively.

Determination of Crude Lipid content: The AOAC (2005) method was used. 5.0g of TOOD flour sample was placed into extraction thimble and then covered with cotton wool. The extraction thimble containing the sample was placed in the extraction jacket. One cleaned and 500mL round bottom flask was weighed (W1) and 300mL of petroleum (boiling point 40°C-60°C) was poured into a few anti-bumping granules and were added the content in the flask.

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Journal of Scientific and Industrial Studies, Volume 15, Number 2, 2020 The flask was then fitted to the sohxlet extraction unit. The round bottom flask and the condenser were connected to the sohxlet extractor and cold-water circulation and the heating mantle was switched on. The heating rate was controlled until the solvents were refluxing at a steady rate. Extraction was carried out for 6 hours. The solvent was recovered and the oil extracted was distilled in the oven at 70ºC for 1hour. The round bottom flask and oil was cooled and then weighed (W2). The lipid content was calculated as follows: Percentage crude lipid = (W2-W1) x 100 W1 1 This procedure was followed in the determination of the Crude Lipid content for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Determination of Carbohydrate Content: The total Carbohydrate content was determined by difference method of AACC, American Association of Cereal Chemists (2000).The sum of the percentage moisture, ash, crude lipid, crude protein and crude fiber was subtracted from 100% Carbohydrate. 100 - (% moisture + % ash + % protein + % lipids + % fibre). FUNCTIONAL ANALYSIS (PHYSICO CHEMICAL PROPERTIES) OF UNRIPE PLANTAIN FLOUR Bulk density: The bulk density (BD) was determined by the method described by Wang and Kinsella (1976). 10g of TOOD flour sample were placed in graduated cylinder (50ml), and packed by gently tapping the cylinder on the bench top (10 times) to form reasonable height. The volume of sample was recorded. Bulk density was expressed as grams per milliliter. Bulk density = weight of sample volume occupied This procedure was followed in the determination of the bulk density for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Water absorption capacity (WAC): WAC which gives an indication of the amount of water required for gelatinization was determined according to Solsulski (1962). 2.5 g of TOOD flour sample was added to 30mL distilled water in a weighed 50ml centrifuge tube. The tube was agitated by vortex for about 5 min before being centrifuged at 4000 x g for 20 min. The mixture was decanted and the clear fliud discarded. Adhering drops of water were carefully siphoned (tapped) as much as quantitatively possible and the tube was reweighed. This procedure was followed in the determination of the water absorption capacity for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Swelling capacity: The swelling capacity was determined according to the method of Adebowaleet al., (2009). 5g of TOOD flour sample was weighed into a pre-weighed centrifuge tube, and 20ml of distilled water added and was thoroughly shaken on a vortex (twister). It was then heated to temperatures of 500C, 600C, 700C and 800C for 30 min in a water bath. The sample was centrifuged at 3000rpm for 20min. The supernatant was carefully collected and residue was weighed for swelling power determination. The fluid collected was dried to a constant weight at 1100C in hot air oven (TT 9053A Techmel and Techmel USA). The residue obtained after drying the supernatant represented the amount of starch solubilized in water.

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Processing and Characterization of Dried Unripe Plantain Flour Calculation: Swelling capacity = weight of sediment Weight of sample – weight of soluble sample This procedure was followed in the determination of the swelling capacity for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Water / oil absorption capacity: The water absorption capacity and oil absorption capacity was determined by the method of Satheet al.,(1982) with some modifications. 1 g of TOOD flour sample was weighed into a beaker, 10 ml of water was added and the suspension was stirred with magnetic stirrer for 1 min. The suspension was then allowed to stand for 30 min. at room temperature after which it was centrifuged (New Life Centrifuge NL-90-2) at 5,000 rpm for 30 minutes. After centrifugation, the volume of the supernatant was measured and the result was expressed as volume (ml) of water absorbed per 100 g of the sample. The same procedure was used for oil absorption capacity except that water was replaced with vegetable oil of specific gravity of 0.98 g/ml. This procedure was followed in the determination of the water/oil absorption capacity for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively. Solubility: Solubility in water which indicates their ability to reconstitute was determined by the method of Kulkarni et al. (1991). 10 g of TOOD flour sample was weighed into a 100ml measuring cylinder. Distilled water was added up to 100 ml volume. The sample was vigorously stirred and allowed to settle for 3 hrs. The volume of settled particles was recorded and subtracted from 100 to give a difference that is taken as percentage solubility. This procedure was followed in the determination of the solubility for TOSD, BTOD, BTSD, NTOD, NTSD, BOOD, BOSD and FS (control) respectively.

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Journal of Scientific and Industrial Studies, Volume 15, Number 2, 2020 RESULTS Proximate Composition of Unripe Plantain Flours of Four Different Treatment Methods and Dehydrated by Two Different Methods. SAMPLES MOISTURE

CONTENT %

CRUDE LIPID CONTENT %

ASH CONTENT %

CARBOHYDRATE CONTENT %

CRUDE PROTEIN CONTENT %

CRUDE FIBRE CONTENT %

BTSD 11.60 0.01 3.83 1.07 71.65 7.25 4.62

BTOD 8.69 0.25 5.92 2.14 70.64 4.06 8.55

NTSD 10.08 13 3.77 1.11 69.48 6.26 9.31

NTOD 9.40 3.83 1.22 70.24 6.01 9.34

TOSD 9.51 4.32 1.66 70.36 6.04 8.12

TOOD 8.47 6.73 0.68 69.85 6.04 8.25

BOSD 10.54 4.01

1.37 71.65 6.25 6.20

BOOD 9.59 3.62

1.74 71.56 6.14 7.36

FS 9.51 4.28

1.78 70.74 7.42 6.57

Table 1: A table showing the result of the proximate composition of unripe plantain flour treated with four different methods using two dehydration methods. NOTE: BTSD: blanched and treated sun drying BTOD: blanched and treated oven drying NTSD: non treated sun drying NTOD: non treated oven drying TOSD: treated only sun drying TOOD: treated only oven drying BOSD: blanched only sun drying BOOD: blanched only oven drying FS: flour sample (control).

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Processing and Characterization of Dried Unripe Plantain Flour

Functional Properties of Unripe Plantain Flours of Four Different Treatment Methods and Dehydrated by Two Different Methods. SAMPLES SOLUBILITY

% OIL ABSORPTION CAPACITY (g/g)

WATER ABSORPTION CAPACITY (g/g)

BULK DENSITY (g/ml)

SWELLING POWER (g/g)

BTSD 0.72 0.81 1.16 0.74 1.15 BTOD 0.72 0.88 1.19 0.67 0.85 NTSD 1.19 0.95 1.27 0.67 1.42 NTOD 0.55 0.81 1.54 0.69 1.41 TOSD 0.95 0.79 1.26 0.67 1.07 TOOD 1.82 0.87 1.15 0.65 1.11 BOSD 0.52 0.77 1.53 0.74 1.17 BOOD 0.85 0.67 2.05 0.72 1.03 FS 1.20 0.97 1.67 0.69 1.92 Table 2: A table showing the result of the functional properties of unripe plantain flour treated with four different methods using two dehydration methods.

NOTE: BTSD: blanched and treated sun drying BTOD: blanched and treated oven drying NTSD: non treated sun drying NTOD: non treated oven drying TOSD: treated only sun drying TOOD: treated only oven drying BOSD: blanched only sun drying BOOD: blanched only oven drying FS: flour sample (control). DISCUSSION Table I summarizes statistical analysis of the proximate composition of unripe plantain flour obtained from four different treatment methods. The results indicated that all drying methods except BTSD had no significant effect (P <0.05) on the proximate content of unripe plantain flour. The moisture content of the TOOD sample dried with oven was the lowest and the moisture content of BTSD sun dried sample was the highest compared to the flour sample (FS) used as control. The moisture content of the four samples dried with oven were lower than 9.60% reported for unripe plantain dried with oven at 55°C for 36 hours (Abioyeet.al., 2011). The apparent increase in carbohydrate, ash and fibre contents observed in this study following drying treatments could be as a result of the removal of moisture which tends to increase the concentration of nutrients (Morris et.al., 2004). Processing has been reported to increase carbohydrate availability in a more digestible form (Emperatrizet.al., 2008). This could explain the significant difference (P<0.05) observed in the carbohydrate content of processed flour samples (oven-dried and sundried plantain flour). Decrease in these macro nutrients (table 2) may be attributed to the application of heat. Similar losses of these macronutrients after heat treatment have been reported (Hassan et.al., 2007; Enomfon-Akpan and Umoh, 2004; Morris et al., 2004). Application of heat can be both beneficial and detrimental to retention of nutrients. Heat improves the digestibility of food, promotes palatability and also improves the sustenance of quality of food, making them safer to eat. Heating process also results in nutrients’ losses by inducing biochemical and nutritional variation in food composition.

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Journal of Scientific and Industrial Studies, Volume 15, Number 2, 2020 Moisture content has implication on the shelf stability of food products; unripe plantain flour sample with the highest moisture content will therefore be more susceptible to deteriorative changes during storage. Sun dried samples had the highest protein content of above 6% which was significantly different (P < 0.05) from the protein contents of oven dried samples, the protein contents of all the samples were lesser than 7.50% for both the sun dried and oven dried unripe plantain flour as reported by Eleazuet.al.,(2010). The ash contents of BTOD, TOSD and BOOD samples were not significantly different (P < .05) however, BTSD,NTSD,NTOD, BOSD, and TOOD had the highest ash content of above 1.2% which was significantly different (P < .05) from that of other samples. Ash content is a reflection of the mineral composition of food samples. Table 2 shows the result of the statistical analysis on the functional properties of unripe plantain flour samples. The results obtained are discussed below. The solubility shows TOOD flour sample has the highest solubility, while BTSD and BTOD had the lowest solubility and had no significant difference (p>0.05) from FS (control). This is consistent with the observation of Oluwatooyinet al., (2003). The swelling power clearly showed that all treated and blanched flour samples (BTOD, BTSD, BOOD, BOSD,TOOD, and TOSD) had the lowest swelling capacity compared to FS (control). The low swelling capacity implies that the blanched and treated flour samples require much longer time than the other flour samples before their starch content become completely solubilized. There was significant (p<0.05) difference amongst the flour samples. The oil absorption capacity (OAC) of the samples ranged between (0.75-0.98). Oil absorption capacity of all flour samples were lower than their water absorption capacity. All flour samples showed no significant difference except NTSD. According to Oluwatooyinet al. (2003), good OAC of flour samples suggest that they may be useful in food preparations that involves oil mixing like in bakery products, where oil is important ingredient. The water/fat binding capacity of protein is an index of its ability to absorb and retain oil, which in turn influences the texture and mouth feel of food products like doughnut, pancakes, baked goods and soups. Oil absorption capacity is importance since oil acts as flavor retainer and increases the mouth feel of foods (Aremu et al., 2007). The result of the water absorption capacity (WAC) show that BOOD flour sample had the highest WAC (2.05 %) while TOOD had the least value of 2.39 %. These were in accordance to the findings of Oluwatooyinet al. (2003) who observed that WAC could be enhanced by blanching. Although the values obtained are lower compared to those reported for Bambara groundnuts flour (Eltayebet al., 2011), soybean flour and African yam flour (Oshadiet al., 1997). There was no significant (p > 0.05) difference for all the flour samples. The bulk density (BD) of the blanched flour samples had higher mean than other treatment methods. The bulk density result indicate that the blanched flour sample had more moisture than other flours samples. There were no significant (p > 0.05) difference amongst the flour samples except BOOD flour samples. CONCLUSION AND RECOMMENDATION Based on the results obtained from the study, the two drying methods were both good as all samples yielded nutritional constituents with minimal differences from the flour sample used as control. However, to obtain fast drying, conserve protein and lower moisture content, the oven drying method though likely to be more expensive is recommended, while the sun drying method which is cheaply executed takes a longer time and may be prone to contaminations from microorganisms due to unhygienic exposures. Color is an important physical parameter in flour quality. Flours obtained by sun-drying are darker than those obtained by oven-drying. The darkest color was that of the NTSD and BOSD plantain flour. Those obtained in a BTOD and TOOD presented the lightest color when compared to the standard white plate tile. These results suggest occurrence of the Maillard reaction in those browned coloured flours samples (NTSD and BOSD). This could be due to the browning produced by enzymatic reaction of Polyphenol Oxidase that usually take place in the presence of Oxygen.

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Processing and Characterization of Dried Unripe Plantain Flour The other flour samples maintained their original colour (no browning), indicating that the treatment methods inhibit the browning reaction. Further studies could focus on the microbial contamination of the flours from respective processing methods, fatty acids profile and amino acid profile analysis. Moreover, the reducing sugars content and the glycemic index of the flours need to be examined. This will provide the necessary information to adopt this food sample as a dietary source for special nutritional cases, such as diabetics, depending on the results obtained. REFERENCES Abioye V.F, Ade-Omowaye B.I., Babarinde G.O, Adesigbin M.K. Chemical, physicochemical and

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