Proximate composition, nutritive and sensory properties of fermented maize, and full fat soy flour blends for “agidi” production

Composite flours containing 100:0, 85:15, 80:20 and 70:30 fermented maize and full fat soy flours, respectively were prepared. The effect of the soy flour supplementation on the proximate composition and nutritive values of the blends were evaluated. “Agidi”, a maize based fermented food product produced from the blends were subjected to sensory evaluation. The result shows higher protein contents (16:55, 20.63 and 20.77%) than the fermented maize used as control (8.92%). There were corresponding increases in the fat, ash and energy contents of the blends. The weight gains of the rats fed the diets containing 20 and 30% soy flour (2.25 and 2.30 g) and then protein efficiency ratio (PER) (2.00, 2.10) were not significantly different from those of casein (2.35 and 2.50 g, respectively) (P>0.05). No statistical differences were found for colour, consistency, flavour and overall acceptability among the “agidi” products (P>0.05). The blends containing 20 and 30% full fat soy flour were found to have the best potential for “agidi” production.


INTRODUCTION
"Agidi" is a thick gel produced from fermented maize paste or flour. It is a popular food product in Nigeria and some West African countries (Otunola et al., 2006;Otunola et al., 2007;Osungbaro et al., 2009). Agidi produced from fermented maize flour is inherently deficient in nutrients, especially lysine and some nutrients are leached out because of the poor processing techniques involved in its traditional production (Adeyemi and Beckly, 1986;Adeniyi and Porter, 1978;Adeyemi et al., 1987). Such deficiencies may result in protein malnutrition among consumers of "agidi" particularly the young children who are fed with the product as weaning food (Onyeka and Dibia, 2002;Plahar et al., 2003). Earlier attempts at improving the physico-chemical, sensory and nutrient qualities of "agidi" included, process modification, cereal variety selection and protein supplementation (Akpapunam et al., 1997;Tsatsu, 2009;Ohenhen, 2002;Adeniy and Porter, 1978;Aminigo and Akingbala, 2004). Incorporation of oil seed such as soybean to fermented maize floor is supposed to provide a nutritionally improved food because of the expected increase in protein quality and high energy value of the blends. However, very little has been reported about the nutritive value of "agidi" especially those supplemented with legumes or oil seed. One major limitation of plant food blends that is obvious and already noticed is the poor digestibility associated with low solubility of plant proteins (Michelfelder, 2009;Messina and Messina, 2010). These factors such as the physico-chemical, sensory properties and nutritive value of soy supplemented *Corresponding author. E-mail: aveyina2012@gmail.com. agidi need to be investigated so that the full potentials of the blend can be established for product development (Ohenhen and Ikenemoh, 2007., Osundahunsi et al., 2003., Osungbaro,1990a., Osungbaro,1990b., Osungbaro, 1998. The study reported here therefore determined the effect of full fat soy flour supplementation on the proximate composition and protein nutritive value of maize/soy flour blends for "agidi" production. The sensory properties of the "agidi" produced from the maize : soy blends were also determined.

MATERIALS AND METHODS
The maize (Zea mays L.) and the soybean (Glycine max L.) used for the study were obtained from a local farm in Makurdi, Benue State, Nigeria.

Preparation of fermented maize flour
The fermented maize flour was prepared by the wet milling process with slight modification (Adeyemi and Beckly, 1986;Adeniyi and Porter, 1978;Osungbaro, 1990a;Osungbaro, 1990b;Osungbaro, 1998). The maize grains were sorted and cleaned to remove broken grains and foreign objects. The grains were boiled in water (1:2w/v) at 100 ± 2°C for 2 min. The boiled grains were wet milled in a commercial maize mill and filtered through cheese cloth with excess water. The slurry obtained was left to sediment and ferment for 3 days at room temperature (27 ± 2°C). The water was decanted and the paste obtained was dried in the sun at 40 -50°C (3 days). The dried paste was milled into flour in a maize mill (model corona -2N, England) and stored in a refrigerator at 4°C after sieving (150 µm).

Preparation of soy flour
The soy flour was prepared according to the method reported by Amadou et al. (2009) andIwe (2003). The flour was stored in a refrigerator (4°C) until used.

Blend formulation
Three different blends were formulated based on fermented maize and full fat soybean flours in the ratios of 100:0, 85:15, 80:20 and 70:30, respectively. The formulation was designed to obtain the most acceptable product or products which have the highest protein content (Akpapunam et al., 1997).

Proximate analysis
The proximate analysis (protein, fat, ash, moisture and crude fibre) of the fermented maize flour and the blends was determined by the official methods of AOAC (2012). Carbohydrate was determined by difference (100 -the sum of the content of protein, fat, ash and moisture). Energy was calculated using Artwater factor (fat x 9 + carbohydrate x 4 + protein x 4 kcal/100 g).

Biological evaluation of protein quality
Protein nutritional quality of the blends was assayed in vivo by means of the protein efficiency ratio (PER) according to the AOAC Ikya et al. 447 (2012) official method. Twenty five young albino rats (21 days old) weighing 45 -55 g were randomly assigned to five experimental diets in groups of 5 rats each. The rats were housed in individual metabolic cages placed on cardboard to allow collection of faeces. Ten grams of each experimental basal diet (Table 1) and water were fed to the rats ad libitum. Casein served as the control diet. The total food intake of the rats was determined by recording the food left after daily intake. Daily weight gain was determined by weighing the rate individually. Protein consumption was calculated from the food intake.
Carmine red (0.1 g) was added to the diet to serve as marker. The coloured faeces of the rats that appeared on day 10 was collected to mark the beginning of collection. The collection was from day 10 to day 26. All collected faeces were stored in small screw bottles and stored in a refrigerator (4°C) until used. At the end of the collection period, the bulk faeces for each rat were dried, weighed and milled into fine powder. The nitrogen content of the faeces was determined by the standard kjeldahl method (AOAC, 2012) to determine the nitrogen digestibility (N.D).

Preparation of "agidi"
Nigerian agidi or eko is Nigeria's Jello sort of. It is made with corn flour. The process is very similar to the process of making ogi but with a slight difference.

Sensory evaluation of "agidi"
Colour, consistency, flavour and general acceptability of the agidi samples were evaluated by a 22-member panel, using a 5 point Hedonic scale with 1 representing the least score and 5 the highest (Akpapunam et al., 1997).

Statistical analysis
Analysis of variance (ANOVA) was performed on all data collected to determined differences, while the least significant test was used to detect significant differences among the means (Steel and Torrie, 1990).

RESULTS AND DISCUSSION
The proximate composition of maize/soy flour blends is presented in Table 2. The content of protein, fat, fibre and ash increased with the increase in the soy flour in the blends. Conversely, the carbohydrate content of the blends decreased considerably from 84.30% in the 100% maize flour to 67.11% in the blend containing 30% soy flour. The protein content of the 100% maize flour blend was 8.92% as compared to 16.55, 20.63 and 20.77% for the blends containing 15, 20 and 30% soy flours, respectively. The trend was the same for fat, fibre and ash contents of the blends. This is a reflection of the superior nutritional properties of soybean flour over maize flour and it demonstrated their mutual supplementation effect. The protein values compared favourably with Table 1. Composition of experimental diet (g/100 g diet) (10% been total gram mass of maize and soy flours as the protein containing materials in the formulation).  those reported by (Edema et al., 2005;Olaoye et al., 2006;Adeyemi and Beckly, 1986;Adeyemi et al., 1987;Osungbaro et al., 2009). The high caloric value of the blends is note worthy (416.57 to 424.07 Kcal/100 g). It is an indication that agidi produced from the blends would be a good source of energy. The results of the nutritive value of the control ration and the maize/soy flour blends are shown in Table  3. The high food intake of rats fed diet A (7.8 g) could suggest that the protein was of poor quality as such, and the rats consumed more to compensate for the poor quality-a commonly observed phenomena. The rats fed diet A had negative weight gain (-0.44 g) even though they consumed more food. This is a further indication that the protein was of poor quality (Alabi et al., 2001;Chai et al., 2011;Osungbaro et al., 2009;Evans et al., 2007;Adeyemi et al., 1987). The rats fed diet B had the second highest food intake and also the second lowest weight gain.

Component of experimental diets (g/100 g) Sample code (A -E )
The same reason adduced for diet A is applicable here. However, diet B appears to have more desirable pattern of essential amino acid (EAA) that supported growth than that of diet A. On the other hand, the control rats which consumed less (2.85 g) gained more weight (2.35 g). This indicates its protein superiority over the other diets. The food intake and weight gain of rats fed diets C and D were very close suggesting that their protein quality was readily the same. The lower PER (0.35) of rats fed diet A was not a surprise. The rats had negative body weight and feed efficiency, which affected the PER. The higher PER for casein group showed that the diet contained desirable pattern of EAA, which the animals used to synthesize new protein (Alabi et al., 2001;Chai et al., 2011;Osungbaro et al., 2009). The PER of rats fed diet D is close to that of E which tends to suggest that its protein was as good as that of the control (casein). The negative nitrogen utilization (NU) for diet A is expected because of its poorer protein quality. The lower but positive NU (48.24) for diet B showed that 15% soy flour supplementation was not as good as others (20 or 30%). The closer NU for diets C and D to that of E indicates that nitrogen from soy flour and mixtures could be utilized as that of casein. The high digestibility for the diets (93.7 -98.5%) showed that their proteins were digestible; however, the utilization was low. The result of the study has shown that addition of 20 to 30% full fat soy flour to fermented maize flour could produce a nutritionally adequate food product 'agidi'. Similar findings with legume and oil seeds have been reported by other workers (Alabi et al., 2001). The sensory evaluation results of the "agidi" samples are presented in Table 4. No statistical differences were found for colour, consistency, flavour and overall acceptability among the products. There were, however, slight decreases in these quality attributes with increase in soy flour supplementation. Panel members did not detect any beany flavour in the products, which indicates that the processing of the soybean seeds was able to remove the typical beany flavours associated with soy products (Ampofo, 2009).

Conclusion
The nutritive value of maize/soy flour blends for "agidi" production is dependent on the level of soy flour supplementation. Chemical, biological and sensory evaluation of the flour blends and the agidi showed an increased nutritive value and a comparative sensory acceptability with respect to the control (all maize "agidi"). The blends containing 20 and 30% full fat soy flour were found to have the best potential for agidi production.