Comprehensive evaluation the quality of imported

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Ground grain was one of civilized man's first foods. Ancient methods of grinding can be traced to the Far East, Egypt and Rome. As early as 6,700 B.C., man ground grains with rocks. Water mills did not appear until 85 B.C. in Asia Minor. Windmills appeared between 1180 and 1190 A.D. in Syria, France and England.

In Libya and the countries of the southern Mediterranean Region, bread has always been considered as the staple food of choice. consequently Libya imports 95% of the flour needed for its baking industry from European countries. Preliminary studies showed that most of imported flour been highly deteriorated. This fact revealed that:

  1. High free fatty acids has been found in most parches of flour imported from abroad.
  2. Most of imported flour is less inform of wheat gluten ( weak flour - less than 30% ). Incomparable to what has been accepted by Libyan quality board (more than 30% for wet gluten).
  3. Most of imported flour in medium in term of gluten strength which is not suitable for bread nither cookies and cakes production.
  4. Because of weakness of flour, most of bakers using chemical improvers which is most of its in out of order due to health concern.
  5. We noticed that high quantity of flour imported from abroad, which greater than to be needed for local user.
  6. The extra flour been stored in the local store which is not proper one because of lack of cooling facilities. We noticed that this flour has been deteriorated within three months, mainly in the
    summer time. Also huge amount of insect which more than acceptable has been noticed in the stored flour.
  7. The quality of local wheat varieties is not studied well mainly in term of genotype and location affects to predect its quality aspect to be used in baking industries.

It is important to study the quality of the plantain flour to determine its suitability for use as composite flour. The flour quality can be assessed by physical and chemical analysis as well as by baking tests. Many workers have studied the physical and baking properties of other starchy staples like cassava, cocoyam and taro. Idowu et al. [5] studied the use of cocoyam flour as composite with wheat flour in bread and biscuit production. They found that up to 10% and 80% substitution with cocoyam flour produced acceptable breads and biscuit, respectively.

The objectives of this study is to evaluate:

  1. Study the chemical composition.
  2. Gluten determination (Wet and Dry).
  3. Amylase activity.
  4. Flour water absorption, dough stability, dough weakness.
  5. Resistance to extension, extensibility and ratio figure.
  6. Gelatinization temp. maximum viscosity.
  7. measuring the bread volume for prepared, loaf bread.
  8. Sensory evaluation for the bread made from imported flour and local flours.



Five kilogrammes (5kg) of "False Horn" matured green plantain (Musa paradisiaca) were procured from International Institute of Tropical Agriculture, (IITA), Onne, near Port Harcourt, Rivers State. The wheat flour used was white extract of milled grain imports from USA by the Nigerian Flour Mills. Both hard and soft wheat flours were provided for bread and biscuit formulations respectively. All other baking ingredients were supplied by the Nigerian Flour Mills Plc, Port Harcourt and the baking process was done at their factory.

Sample Preparation

Plantain heads were cut into separate bunches which were subsequently defingered. The fingers were washed, peeled, cut into thin slices of 2 cm thick and blanched in 1.25% NaHS03 solution at 80°C for 5 min [7]. Blanched plantain slices sere drained and dehydrated in a Thelco air-recirculating oven at 60°C for 24 hours. Dried plantain slices were milled into flour in a Retch Muhle 2880 Hammer mill. Flour obtained were sifted through a 250 µm aperture sieve and packed in a two-ply medium density (0.926 - 0.949 g/cc) polythene bag.

Bread and biscuit making

Composite flour samples containing wheat and plantain flours were formulated at 0, 5, 10, 20 and 30% (w/w) level of wheat flour substitutions for bread making and for biscuits at 0, 50, 60, 70, 80, 90 and 100% (w/w) levels.

Proximate Composition

Proximate analyses of the samples will carry out using official AOAC methods [8] for moisture (14.004), crude fat (14.081), crude fiber (7.0006), ash (14.006) and crude protein (47.021). A nitrogen to protein conversion factor of 6.25 was used. Carbohydrate will calculate by difference.

Functional Properties

Water and oil absorption capacity: Water and oil absorption properties of the composite flour were determined following methods of Sathe et al. [9]. Briefly, flour sample (2 g) was mixed with 20 ml distilled water for water absorption and 20 ml of oil for oil absorption in a Moulinex blender (Model dePC 3, France) at high speed for 30 (s). Samples were then allowed to stand at 30°C for 30 min then centrifriged at 10,000rpm for 30 min. The volume of supernatant in a graduated cylinder was noted. Density of water was taken to be 1g/ml and that of oil was determined to be 0.93 g/ml. Means of triplicate determinations were reported. Foaming capacity and stability were studied according to the methods described by Desphande et al. [10]. For stability, the flour sample (0.5g) was blended for 30 min in distilled water (40 ml) at top seed in a Moulinex blender. The whipped mixture was transferred into a 100 ml graduated cylinder. The blender was rinsed with 10 ml distilled water which was then gently added to the graduated cylinder. Foam volume in the cylinder were recorded per sample after 30 min standing. Triplicate measurements were made for each sample and mean values recorded.

Emulsion capacity and stability

A flour sample (2g) and distilled water (100ml) were blended for 30 (s) in a Moulinex blender (Model depC 3, France) at high speed (ca.100rpm). After complete dispersion, peanut oil was added from a burette in streams of about 5 ml. Blending continued until there was separation into two layers. Emulsification determinations were carried out at 30°C and expressed as grams of oil emulsified by 1g flour. Emulsion stability was studied following the methods described by Okezie and Bello [11]. Briefly, sample (4 g) was dispersed in distilled water (100 ml), then 100 ml of peanut oil was added at the rate of 12.5 ml per (s) while blending. Each sample was blended in a Moulinex blender at high speed for additional 60 sec. and transferred into a 250 ml graduated cylinder volumetric changes in foam, oil and aqueous layers were recorded after 3 hr. Triplicate measurements were made and average results taken.

Bulk Density

Bulk densities of samples were determined by weighing the sample (50 g) into 100 ml graduated cylinder, tapping cylinders ten times against the palm of the hand and expressing the final volumes as g/cc.

Rheological Determinations

Rheological properties of dough from the blends were determined using an alveograph (Chopin, Model MA 82, France) using standard recommended alveograph procedures [12, 13]. Flour blends (250g) was kneaded with water (500ml) containing 25% NaCl in the alveograph mixer. A mixing time of 8 min. at 29°C and 20 min rest period were the condition used. From alveograms obtained, the following rheological parameters of dough were calculated;

  1. the height of curve, R (mm) which measured the pressure applied during inflation and indicated the resistance of dough to deformation.
  2. the length of the curve, L (mm), which measured the extensibility of the dough.
  3. mechanical work for deformation, W, (10-4 joules/g) which measured the overall strength of gluten height/length rate of the curve.
  4. height/length ratio of curve, R/L.

Composite flours were then used to prepare bread and biscuits using standard recipes (Table 1). For bread-making, a modification of the straight dough method [14] was used. The ingredients, based on a 350 g wheat flour or wheat-plantain composite flour were mixed in a Hobart N-50 mixer fitted to a dough hook for 1 min at No. 1 speed, 1 min at No. 2 speed and the rest of the mixing time at No. 3 speed. Two baking responses namely, dough handling properties and loaf volume (rapeseed method as modified by Giami et al. [15] were monitored as function of added water and % plantain flour in the composite while mixing for 6 mins. Following a 90 minute fermentation time, doughs were punched, moulded, scaled to 500 g and proofed for 2 hr, which gave good loaf volumes for wheat flour and optimum volumes for blends. Baking was at 204°C for 30 min. Duplicate loaves were baked for each substitution level. Loaves were allowed to cool on stainless steel wire at room temperature then placed in plastic bags for sensory evaluation on the second day. For biscuit making, the sheeting method described by Adeyemi and Omolaye [16] was used.

Evaluation of Bread Characteristics

Bread characteristics or baking qualities were evaluated by measuring the loaf volume, specific loaf volume, the oven by spring and the organoleptic characteristics. Loaf volume was measured 50 minutes after loaves were removed from the oven by using the rapeseed displacement method as modified by Giami et al. [15]. Briefly, loaf volume was measured by seed displacement using pearled barley in place of rapeseed. A box of fixed dimensions (24.00 x 15.70 x 18.95 cm) of internal volume 7140 cm3 was put in a tray, half filled with pearled barley, shaken vigorously 4 times, then filled till slightly overfilled, so that overspill fell into the tray. The box was shaken again twice, then a straight edge (or rule) was used to press across the top of the box once to give a level surface. The seeds were decanted from the box into a receptacle and weighed. The procedure was repeated three times and the mean value for seed weight was noted (B g). A weighed loaf was placed in the box and weighed seeds (4500 g) were used to fill the box and leveled off as before. The overspill was weighed and from the weight obtained the weight of seeds around the loaf and volume of seed displaced by the loaf were calculated using the following equations.

Seeds displaced by loaf (L) = B g + overspill weight - 4500 g.

Vol. of loaf (V) = L x 7140 cm3

Specific volume of loaf = V/wt (cm3/g)

Weight of loaf samples were taken and specific loaf volume was obtained by dividing the loaf volume by its corresponding loaf weight. Oven spring was determined from the difference in height of dough before and after baking. Sensory evaluation was performed 24 hours after baking to evaluate loaf appearance, crust colour, crumb colour, taste/flavour and overall acceptability of the bread sample. The bread samples were sliced into pieces of uniform thickness and served with water. Twenty panel members (familiar with quality attributes of local bread) were randomly selected from students and staff of the Department of Food Science and Technology, to perform the evaluation. Panelists evaluated bread samples on a 9 point hedonic scale quality analysis [17] with 9 = liked extremely, 8 = liked very much, 7 = liked, 6 = liked mildly, 5 = neither liked nor disliked, 4 = disliked mildly, 3 = disliked, 2 = disliked very much and 1 = disliked extremely .

Evaluation of Biscuits

The flow and break strength were determined according to Okaka and Isieh [18] Taste panel evaluation of biscuit samples was similarly conducted using fifteen panel members selected randomly (that are familiar with quality attributes of local biscuits) to access colour, crispness and taste as quality parameters. A 9-point hedonic scale quality analysis as described by Larmond [17] was similarly used as described above.

Statistical Analysis

Analysis for significant differences in the results obtained were performed by using the F-test and the least significant Difference Test (LSD) [19].


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Wheat flour is one of the most important foods in Libyan culture, and is the defining ingredient in most North African styles of breads and pastries.

Ground grain was one of civilized man's first foods. Ancient methods of grinding can be traced to the Far East, Egypt and Rome. As early as 6,700 B.C., man ground grains with rocks. Water mills did not appear until 85 B.C. in Asia Minor. Windmills appeared between 1180 and 1190 A.D. in Syria, France and England.

Ground grain was one of civilized man's first foods. Ancient methods of grinding can be traced to the Far East, Egypt and Rome. As early as 6,700 B.C., man ground grains with rocks. Water mills did not appear until 85 B.C. in Asia Minor. Windmills appeared between 1180 and 1190 A.D. in Syria, France and England.

There are six different classes of wheat: Hard Red Winter, Hard Red Spring, Soft Red Winter, Hard White, Soft White and Durum. The end products are determined by the wheat's characteristics, especially protein and gluten content. The harder the wheat, the higher the protein content in the flour. Soft, low protein wheats are used in cakes, pastries, cookies, crackers and Oriental noodles. Hard, high protein wheats are used in breads and quick breads. Durum is used in pasta and egg noodles. Flour is the product obtained by grinding wheat kernels or "berries." The kernel consists of three distinct parts: bran, the outer covering of the grain; germ, the embryo contained inside the kernel; and endosperm, the part of the kernel that makes white flour. During milling, the three parts are separated and recombined accordingly to achieve different types of flours.