Developing countries (especially Nigeria) are faced with the problem of malnutrition (protein  energy  malnutrition), due to the deficiencies of proteins and calories. The protein/calorie  sources   of  vegetable  origin  have  been proposed as a solution to this problem. The common dietary problem caused by malnutrition is said to be endemic (Olu, 2001), characterized by micro-nutrient deficiency and protein energy malnutrition. Animal protein products are quite expensive and above the reach of low income families, as a result, dietary diversification has been employed as a solution to malnutrition challenges. Studies have been carried out to find other ways of enriching our locally prepared cereal dishes with indigenous plant legumes (Nkama, 1998).

Some raw materials (such as soya bean and maize) are amply used but are not sufficiently available to meet the demand (Echendu et al., 2004). Good alternatives like sorghum, cowpea, plantain and sweet potato are used which possess interesting food characteristics or potentials, with large production that can be exploited for products such as breakfast cereal materials. Cookies have been suggested as a better use of composite flour than bread due to their ready to eat form, wide consumption, relatively long shelf-life and a very good eating quality (Tsen et al., 2011).

Breakfast cereal is defined as food obtained by soaking, swelling, roasting, toasting, grinding, rolling, flaking, shredding or puffing of any cereal preferred for breakfast or in between meals (Olu, 2001).

Based on literature review, no attempts have been made to combine the food stuffs used in this study to obtain a blend that could be used as a cereal based breakfast meal or in between meals referred to as cookies.

The study was aimed at formulation and production of cookies from sorghum, cowpea, plantain and sweet potato blend. The objectives of this study were to:

1. determine the tannin contents of unprocessed and processed sorghum grain.

2. produce and evaluate the nutritional qualities of sorghum, cowpea, plantain and sweet potato cookies.

3. determine the proximate and mineral element composition of the blend.

4. determine the in vitro digestibility of composite blend.

 

Collection of samples

Sorghum (chakalari white), cowpea (Borno red), plantain (unripe) and sweet potato (Ipomoea batatas) were used for this study and were purchased from Maiduguri Monday Market and was authenticated by a botanist in the Department of Biological Science, University of Maiduguri, and Borno state. Nigeria

Pre-treatment of samples

All the sorghum and cowpea samples were manually cleaned by removal of moldy and broken ones. The cereals and legumes were sprouted (while plantain and sweet potatoes was oven dried), as described by Kulkarni et al. (1991).

Sprouting of sorghum and cowpea sample

Three hundred grams (300 g) each of sorghum and cowpea were soaked in plastic bucket containing 300 ml of water and were steeped in water for 30 min at room temperature (28 ± 2°C). The steep water was discarded by decantation and the steeped grains were germinated for 72 h by spreading on a clean grease free tray pan and thereafter were sundried for 2 to 3 days on a sterilized tray pan. The sorghum grains and cowpea were then milled separately using a disc mill (Hunt No. 2A premier mill Hunt and Co, UK), to an average particle size of less than 0.3 mm. The milled grains were sieved through a fine mesh (0.5 um) to obtain the sorghum and cowpea flour, respectively.

Preparation of plantain and sweet potato flour

Five medium sized unripe plantain and 3 medium sized sweet potatoes were used. Each of the plantain fruits and sweet potato tubers were washed in tap water and hand peeled, the edible portions (pulp) from each were sliced with a stainless knife into 2.5 cm thick slices.

The slices were dried at 60°C in an air oven for 4 to 5 h. The slices were then milled using a disc mill (Hunt No. 2 A premier mill Hunt and Co. Ltd, UK) to an average particle size of less than 0.3 mm. The milled plantain and sweet potatoes were sieved through a fine mesh (0.5 um) to obtain plantain and sweet potato flours, respectively as described by Kulkarni et al. (1991).

Cookies preparation

The basic formulation for the cookies according to the method described by Nistiburi and Kwawashik (2004) was 100 g of unprocessed sorghum (US) (control), sprouted sorghum (SS), sprouted cowpea (SC), dried plantain (DP) and dried sweet potato (DSp), 40 g fat (margarine), 25 g sugar, 1½ teaspoonful powdered milk, 1 g sodium bicarbonate, ½ teaspoon full liquid vanilla flavor, 0.3 g nut meg, 1 g salt and ½ whole egg, the dry ingredients were thoroughly mixed (Table 1). The margarine and eggs were added and the dough thoroughly kneaded on a flat stainless metal table for five minutes. The dough was thinly rolled on a sheeting board to a uniform thickness (8.0 mm) and was cut using a round cutter to a diameter of 35 mm.

 

 

The cut out dough pieces were baked for 15 to 25 min on aluminum sheet at 185°C in an oven, cooled, packaged on polyethylene bags and stored at room temperature for further analysis. Determination of proximate composition of cookies blends moisture, crude protein, fat, ash, fiber and carbohydrate were determined according AOAC (2001) method. Atomic absorption spectrophotometer (AAS) AA 6800 series, shimazo corp was used for the determination of Ca, P, K, Fe, and Zn. Tannin content determination was based on vanillin hydrochloric acid quantitative method as described by Burns (1963). In -vitro protein digestibility was determined using the Micro Kjedhal method. The formula below was used to calculate the % digestibility:

Where   CP1 = total protein of unprocessed grain, CP2 = total protein after digestion with trypsin. Vitamin content was determined by the method described by Angelika et al. (1996).

Sensory evaluation

20 panels  of experts’ consumers were used from staff and students of the Department. Criteria for selection were that panelists were regular consumers of cookies and were not allergic to any type of food. Panelists were instructed to evaluate color, taste, texture, palatability and general acceptability.

Statistical analysis

Data’s obtained were subjected to analysis of variance (ANOVA); results were presented as means standard error of mean.

 

 

 

Effect of germination and oven drying on the proximate composition of processed samples

Table 2a shows the effect of processing on the proximate composition of germinated and oven dried samples. The moisture content of the samples of SS, SC, DP and DSp were 8.60, 6.73, 9.53 and 5.53%, respectively. Crude protein content of sprouted sorghum and sprouted cowpea have increased significantly (P < 0.05) (7.08 and 25.04%). Sprouted sorghum had a significantly (P<0.05) lower ash content (1.00%) while comparable higher values were recorded for DP and DSp which had relatively closer values of about 2.80 and 2.70%, respectively.

 

 

 

Percentage carbohydrate content of SS, SC, DP and DSp were 73.00, 55.51, 74.71 and 84.37%, with DSp having the highest value while SC having the least value of 55.51%. The differences observed in all the samples were statistically significant (P < 0.05).

Effect of formulation on the proximate composition of formulated cookies

Table 2b shows the effect of formulation on proximate composition of the control and formulated cookies. The moisture content of the formulated cookies of SSSC, SSDP, SSDSp, SSSCDP and SSSCDSp were 11.67, 11.03, 9.70, 8.70 and 9.67%, respectively. All values were statistically significant (P < 0.05). SSSCDP (60:30:10) had the highest value of crude fiber content (19.04%). Percentage carbohydrate contents of the formulated cookies were 45.54, 51.00, 50.30, 54.42 and 56.00%, with SSSCDSp having the maximum level of about 56.00% and maximum energy level was obtained from SSDP (60:40) of about 414.60 Kcal.

Mineral content of test samples

Table 3a shows the mineral content of test samples; there were significant differences in the mineral contents of the samples. SC had higher levels of Na -73.50%, Fe- 0.83%, and Ca- 213.67%, respectively while SS had the least value of Na about 35.20%. DP and DSp had closer values of 52.70 and 43.20%. DP had the lowest value of Zn (0.09%), highest value was obtained from DSp of about 0.23%, the remaining samples SS and SC had values of 0.11 and 0.09%. Higher value for Fe was obtained from SC 0.83%, while the least value was obtained from DSp 0.37%. DSp had the highest value for K, SS 60:40 and SC 60:40 had closer values of 2.70 and 2.80% and DP had 6.21%.

 

 

 

Mineral content of formulated cookies

Table 3b shows the mineral contents of the formulated cookies. The result showed that for each of the mineral element assayed for, there was a general decrease in composition when comparison was made between the processed samples and the formulated cookies. SSDSp 60:40 had significantly (P < 0.05) higher value of Na content 71.20% while SSDP 60:40 had the lowest value (17.71%), SSSCDP and SSSCDSp had about closer values 32.90 and 37.70%, respectively. SSSC 60:40 and SSSCDP had the lowest values of 0.02% each for Zn while comparable highest values were obtained from SSDP  60:40   of   about   0.68%.   SSDP  60:40  had  the highest values of elemental Fe and Ca 2.19 and 143.33%, respectively. All data obtained were statistically significant (P < 0.05).

Table 4 shows the result of the tannin content of raw and processed sorghum (control). The raw sorghum (control) had 2.07 mg/g of tannin, the processed sample had 0.86 mg/g while the percentage reduction between the unprocessed and processed sorghum was 0.59%.

 

 

In vitro protein digestibility of test samples (%)

Table 5a shows the in vitro protein digestibility of test samples  at  times  of  0, 1  and 6 h, respectively. Results obtained showed a significant (P < 0.05) increase in protein digestibility of the sprouted samples where SC gave the highest value at 0, 1 and 6 h having 91.74, 91.86 and 91.90%, respectively and least value was obtained with DSp having recorded values of 47.58, 52.67 and 5.65%, respectively at different time intervals. SS had 80.17, 82.30 and 86.30% and DP had 44.36, 46.16 and 49.36%, respectively.

 

 

 

Table 6a shows the vitamin contents per gram of test samples. SC had the highest numerical value of vitamin B1 (84.10 µg/g), DP had the least value (9.5 µg/g), SS and DSp had values of 12.1 and 18.40 µg/g. Vitamin B2 and vitamin C were totally not detected in all the samples, vitamin B6 had the highest value of 251.80 µg/g obtained in SC, SS, DP and DSp had values of 35.30, 16.7 and 980.00 µg/g, respectively.

Table 6b shows the vitamin content per gramme of formulated cookies. Vitamin B1 was only present in SSSCDP 60:30:10 and SSSCDSp 60:30:10 (1.3 and 2.10 µg/g), respectively. Vitamin B2 was also present only in SSDSp  60:40   (5.2  µg/g). Vitamin  B6  had  the  highest numerical value of 147.22 µg/g in SSSC 60:40 while comparable least value was obtained in SSSCDP 60:30:10 of 3.00 µg/g, SSDP, SSDSp and SSSCDSp had values of 10.70, 4.60 and 3.40 µg/g, respectively. Vitamin C was also absent in SSSCDSp 60:30:10, having the maximum value in SSSCDP 60:30:10 having 10.70 µg/g and the comparable least value obtained from SSSC 60:40 was 3.92 µg/g, SSDP 60:40 and SSDSp 60:30:10 had values of 4.10 and 6.50 µg/g, respectively.

 

 

 

Sensory evaluation of formulated cookies

The sensory evaluation of the formulated cookies is presented in Table 7. The result revealed that in terms of texture, cookies from SSSC (60:40) had no significant difference with SSDSp (60:40), SSDP (60:40) had no significant difference with SSSCDP (60:30:10), and SSSCDP (60:30:10) also had no significant difference with SSSCDSp (60:30:10), respectively. From the general  acceptability  score,  cookies from SSDP (60:40) had no significant difference with SSSCDP (60:30:10), it can be concluded that cookies from SSSC (60:40) and SSDSp can be baked with satisfactory acceptance.

 

 

Table 8 shows the comparison between formulated cookies and commercial cookies. The commercial cookies had total fat content of 9.0 g while the formulated cookies had SSSC (10.53 g), SSDP (9.23 g), SSDSp (8.42 g), SSSCDP (7.30 g), SSSCDSp (7.49 g) and USC had 9.63 g. The least total carbohydrate was obtained from the commercial cookies (20.0%), the least carbohydrate among the formulated cookies was in SSSC (45.54 g) and the highest value was obtained from SSSCDSp (56.00 g). The formulated cookies had lower crude protein content (4.0 g), higher value  was  obtained from SSSC (12.82 g), and the least value was obtained from SSSCDSp (7.13 g).

 

 

 

 

 

 

 

 

 

Proximate composition

Lack of nutrient dense complementary food is one of the factors accounting for decline in satisfactory protein-energy nutrition. Lartey et al. (1999) reported that appropriate number of feedings depends on the energy density of local foods and the usual amount consumed at each   feeding.   The   dry   matter  content  of  formulated complementary cookies when compared with 7.73 and 12.67% reported in formulated wheat and pigeon pea flour used as a snack in between meals in Western and Eastern Nigeria is an improvement in nutrient density of complementary food which may lead to improved nutrient intake, which means more nutrient for same quantity taken, and may contribute to solving the problem of protein energy malnutrition in the zone. The effect of processing (sprouting) on the proximate composition of processed samples and formulated cookies indicated that processing significantly increased the crude protein, moisture and protein digestibility while it decreased the crude fibre, fat, ash and tannin content, respectively and this may be due to the breakdown of complex compounds into more simple forms, transformation into essential constituents and breakdown of nutritionally undesirable constituents and  conversion of storage proteins into albumins and globulins during sprouting, which may improve the quality of cereal protein. Sprouting is the practice of soaking, draining and germinating, as sprouts are rich in digestible energy, bioavailable vitamins, minerals, amino acids, proteins, beneficial enzymes and phytochemicals, as these are necessary for germinating a plant to grow, and a reduction in the levels of fat, crude fibre, ash were due to germination of the samples (sorghum and cowpea) (Chavan and Kadam, 1989). Sprouting and other fortification with legumes greatly improve the nutritive value and quality of sorghum by removing the anti-nutritive factor (tannin).

The protein content of sprouted sorghum (7.00%) and sorghum fortified with legume (12.82%) showed a significant difference when compared with unprocessed sorghum (control) 5.07%. Fortification of sorghum with legumes (cowpea) improved the nutrient quality of sorghum, as most cereals are deficient in proteins and essential amino acids (Singh, 1984) and conversion of stored soluble proteins, such as albumin and globulin during sprouting, may improve the quality of cereal grain protein (Chavan and Kadam, 1989). The protein quality of the formulated cookies increases with increased levels of cowpea flour. The increased protein and ash content of SC flour was expected because it has been reported to have a relatively high protein (25.00%)  and  ash  content (1.98%), with easily digested carbohydrate, low in fat and high in iron, the increase in carbohydrate content could be due to the high carbohydrate content in sorghum, of all the solid nutrients present in tubers and roots, carbohydrate predominates.

The moisture contents of the samples, sorghum 8.60% and cowpea 6.73% were also increased as a result of processing (sprouting); the increase might be attributed to increased water absorption during sprouting which results in increased activities of hydrolytic enzymes, improvement in total protein content, total sugars, B group vitamins. Increase in the moisture content is only apparent and attributed to the disappearance of starch (Chavan and Kadam, 1989). The fat content of the cookies was relatively low, it was reported that fat plays a role in determining the shelf life of foods. A high amount of fat can accelerate spoilage by promoting rancidity, leading to the production of off flavors and odor (Singh, 1984). Also, a diet that is high in fat can predispose consumers to different illness such as obesity, coronary heart disease etc. The low fat is desirable to both the processor and the consumer and the health conscious individuals, and the low fat in this study may be attributed to germination. Chavan and Kadam (1989) reported that germination results in reduction of fat, crude fiber and ash content, respectively.

The crude fiber content of USC was higher 11.31% than the values for SS and SC (6.03 and 8.17%), which was in accordance with the range reported by Kent and Evers (1998) as sprouting drastically reduce the fiber content. DP and DSp had values of 8.47 and 4.51%, respectively. The highest carbohydrate content of the processed sample was obtained from DSp 84.37%, while the least value was obtained from SC 55.51%, while that of the USC, SS and DP were 65.30, 73.00 and 74.71%, respectively.

In vitro protein digestibility (IVPD)

Research has shown that nutrient composition of foods is not enough to determine the nutrient bioavailability (Dikshit and Ghadle, 2005), hence the need for in vitro digestibility.  The  IVPD  showed  a  significant difference, sprouting increased IVPD due to leaching out of polyphenols in water and enzymic activity as polyphenols form complexes with dietary protein reducing digestibility and protein quality (Boutler et al., 1991), increased digestibility in sprouting may be due to germination of pericarp during sprouting since tannins are found to be located in pericarp of sorghum grain. The in vitro protein digestibility (IVPD) of all the formulated cookies has significantly decreased when compared with the IVPD of the processed samples at time intervals of 1, 2 and 6 h, respectively. The samples with the least protein content (SSSCDP 60:30:10 and SSSCDSp 60:30:10) had the highest IVPD, while the samples with the highest protein content SSSC 60:40 had lower IVPD. This result showed that high protein content does not necessarily imply high digestibility as protein digestibility is actually the amount of protein absorbed into the body relative to the amount that was consumed (Friedman and Cuq, 1988). Protein digestibility has been reported to be reduced by the presence of anti-nutritional factors such as tannin, trypsin inhibitors and oxalate. The level of the anti-nutrient was too low to account for the observed decrease in IVPD. The decrease could have been due to non-enzymic browning reactions which involve interaction between inherent protein and added sugar, resulting in non reversible formation of compounds, causing a decrease in the availability of protein for digestion (McWatters et al., 2003).

Temple and Bassa (1991) produced cookies from Hungary rice (acha), soybean and wheat, and observed that the in vitro protein digestibility of the cookies decreased as the level of soybean flour was increased. This further corroborates the findings in this work where increase in protein content actually resulted in decrease in IVPD, since dietary tannin and trypsin inhibitor are responsible for the poor digestibility of dietary protein (Liener, 1980).

Tannin content

Tannin content was low, as a result the vitamin content, mineral and protein quality of the samples increased from 5.07% in the unprocessed sample (control) to 7.01% of processed sorghum. The tannin content of the sorghum sample was low, the vitamin, mineral and crude protein quality of the processed samples has been enriched. High levels of tannin in raw sorghum may be due to the presence of coloured pericarp either red or brown (Temple and Bassa, 1991). In this study, processing of the sorghum grain from the result obtained significantly reduced the tannin content of the sorghum grain. This is in agreement with the work of Hibberd et al. (2003) who reported that processing method significantly reduces tannin content. The level in the raw sorghum sample was 2.07 mg/g, as for sprouting sorghum, the tannin level decreased to 0.851%. In sorghum, tannin  level is  known to be concentrated in outer layer of caryopsis (Temple and Bassa, 1991). Tannin levels decreased as a result of processing method (soaking, sprouting, germinating).

Mineral composition

As for the mineral composition study conducted, the result showed a marked difference in almost all the mineral element content of unprocessed sample (control) when compared with processed samples (sprouted), this is so because during processing the grains break open and the aleurone layer of some cereals are lost, thus resulting in massive decrease because almost all the minerals are found either on pericarp or aleurone layer of the grain (Mahgoub and El-hag, 1998). This work is in consonance with previous publications which states that processing of cereals depletes their tannin and the mineral content (some) and increase digestibility (Chavan and Kadam, 1989). There was an increase in the Ca and K levels while a significant decrease in level of Zn, Na and Fe (Rooner and Serna-Saldive, 1999), sorghum is a good source of Mg, Fe, Zn, Cu etc., but a poor source of Ca and Na, the result from the present study showed that there was an increase in the levels of Ca and Na due to reduction of phytic acid during sprouting (Svanberg and Sandberg, 1998). The Na content of the unprocessed sorghum (control) was 54.90%, the processed sorghum had decreased value of 35.20%, SC, DP and DSp had values of 73.505, 43.20% and 52.70%, respectively, and the highest value from Ca was obtained from US (control) having about 104.67% while comparable least value was obtained from SC of 21.67%. DSp had the highest value of Zn 0.23% and the least value 0.37% for Fe. The formulated cookies had the highest level of Na from SSSCDSp 60:30:10 of 37.70%, comparable least value was obtained from SSDP 60:40 of about 17.71%. Higher levels of Zn and Fe were obtained from SSDP 60:40 of 0.68 and 2.19%, least values were also obtained from SSSCDP 60:30;10 of 0.02 and 0.33%, respectively. K and Ca least value was obtained from SSSCDSp 60:30:10 of 2.70 and 47.67%, respectively.

Vitamin content of samples

The vitamin content of the samples was affected by processing when compared with the unprocessed and formulated cookies. SC has the highest value of vitamin B1 among the processed samples (84.1%); the least value was obtained from SS 12.1% while US (control) had none. It was not present. DP and DSp have values of about 9.5 and 18.4%, respectively. Vitamin B2 and C were totally absent in all the samples. Vitamin B6 has the highest value of 251% in SC, comparable least value was obtained from 2.2, SS, DP, DSp have values of 35.3, 16.7  and  98.0%,  respectively.  The  formulated  cookies have lower values of vitamin and mineral content than the processed samples due to heat denaturation because they are heat liable. In US, SS and SC, vitamin B1 was absent; SSSCDP and SSSCDSp had values of 1.3 and 2.1 %. Vitamin B2 was only present in SSDSp, having 5.2%. Vitamin B6 had the highest value from US (control) of about 147.2% and the least value from SSSCDP, highest value of vitamin C was obtained from SSSCDP of 10.7% while it was absent in SSSCDSp.

 

SSSC (60:40) has higher protein, greater potentials and can be compared favorably than SSDP (60:40), SSDSp (60:40), SSSCDP (60:30:10) and SSSCDSp (60:30:10), while SSDSp is a better fortified option than SSDP as is more superior in most of the nutrients analyzed in the levels of protein (11.42 ± 0.00) than SSDP (10.11 ± 0.00) and ash (1.78 ± 0.01) than SSDP (1.70 ± 0.10) and crude fiber (18.49 ± 0.02) than SSDP (17.20 ± 0.00) due to supplementing of processing methods and availability of the blend component, and low socio-economic class of individuals can be able to meet up the nutritional requirement. The result observed gave a good indication that the formulation could provide the nutrient needed. It also showed that food blend could be of high nutritive value with a balanced status (mono - cereal) than a single meal. Food processing (sprouting) of the samples has shown a significant increase in protein, moisture and carbohydrate content (P < 0.05) and a significant decrease in fat, crude fiber, ash, vitamin and mineral content, there was also an increase in IVPD due to reduction in tannin level during sprouting.

 

Based on this research, the following recommendations are made:

1. Further analysis like storage stability and physical properties of the cookies blend should be carried out.

2. Nutritional Educational Programme should be planned and implemented to convince people that cookies can be nutritionally improved by supplementing grain with legumes at 40% level of inclusion.

3. Further analysis like amino acid composition should be carried out.

 

The authors have not declared any conflict of interest