Effect of blending ratio on proximate composition of maize flour
Moisture content
The moisture content of flour is important for two reasons, first, the higher the moisture content, the lower the amount of dry solids and secondly, the organisms present naturally in the flour start to grow at higher moisture contents, producing off odour. The moisture content of whole maize flour and blended maize flour varied from 8.56±0.01 to 8.66±0.01% as presented in Fig 1. The average moisture content for whole maize flour was found out to be 8.56±0.01%, wheat flour was 8.58±0.02% and gram flour was 8.60±0.02%. The average moisture content of maize flour blended with wheat was 8.58±0.02% while for the gram flour it was 8.59±0.01%. It was higher in case of maize flour blended with gram rather than wheat. The difference in the moisture content of both is due to the difference in the individual moisture content of wheat and gram flours. Similar trends were reported by
Kaushal et al., (2012) for the blends of taro, rice and pigeon pea flour.
Protein content
Protein is a macronutrient essential to build muscle mass. It is basically composed of amino acids. It is important to measure protein content as a higher percentage of protein means a harder flour best suited to make chewy, crusty flatbreads. The protein content of whole maize flour and blended maize flour varied from 10.41±0.01 to 12.89±0.02% as presented in Fig 2. The average protein content of whole maize flour was 10.41±0.01%. The average protein content of maize flour blended with wheat was 12.43±0.01% while for the blended with gram flour it was 12.83±0.02%. The protein presence was higher for gram blended flour than blended with wheat. The difference in protein content of both the blended flours is due to the fact that the protein content of gram flour is higher than the wheat flour. Similar trend was reported by
Butt et al., (2004) who studied the protein content for the blends of wheat and rice flour.
Crude fat content
The crude fat content of whole maize flour and blended maize flour varied from 4.36±0.01% to 6.20±0.02% (Fig 3). The average crude fat content of whole maize flour was 4.36±0.01%. The average crude fat content of maize flour blended with wheat was 5.48±0.01% while for the one blended with gram flour, the average crude fat content was 6.13±0.02%. The crude fat content is higher for maize flour blended with gram than the flour blended with wheat. This may be due to the difference in the individual fat content of both the blended flours. Similar trend was reported by
Yaseen et al., (2007) for finding the crude fat content of corn flour blended with triticale flour.
Ash content
Ash content is the mineral or inorganic material in flour. It is important to measure ash content of flour as it is a good indicator of contamination in refined flour. The ash content of whole maize flour and blended maize flour varied from 2.20±0.02% to 2.32±0.02% as presented in Fig 4. The average ash content of whole maize flour was 2.20±0.02%. The average ash content of maize flour blended with wheat flour was 2.22±0.02% while for the one blended with gram flour was 2.30±0.02%. The ash content of gram blended maize flour is slightly higher than wheat blended flour. This may be due to the difference in the particle size of the two flours used as blend. Similar trend was reported by Tekle (2009) for blending taro flour with wheat.
Crude fibre content
Crude fibre determination is adequate to estimate the dietary fibre in flour. The crude fibre content of whole maize flour and blended maize flour varied from 2.40±0.02% to 2.88±0.02% (Fig 5). The fibre content of whole maize flour was 2.40±0.02%. The average fibre content of maize flour blended with wheat was 2.73±0.02% while for the one blended with gram flour, the average crude fibre content was 2.82±0.02%. The fibre content of gram blended maize flour is higher than the wheat blended flour. The difference in the fibre content of the two flours used as blend is the reason for the higher fibre content of gram flour than the wheat flour. Similar trend was reported by Tekle (2009) for blending taro flour with wheat.
Carbohydrates content
Carbohydrates are chemically defined as neutral compounds of carbon, hydrogen and oxygen. The carbohydrate content of whole maize flour and blended maize flour varied from 66.04±0.01 to 70.13±0.01% as presented in Fig 6. The average carbohydrate content of whole maize flour was 70.13±0.01%. The average carbohydrate content of maize flour blended with wheat was 68.72±0.01% while for the one blended with gram flour, the average crude fibre content was 66.25±0.01%. The carbohydrate content of wheat blended maize flour was higher than the gram flour blended. While measuring the chemical composition of different blending ratios of corn and triticale flour, similar trend was reported by Hussein and Hegazy (2007) on researching the carbohydrate content of the flour.
Functional properties of flour
Titrable acidity
Total titrable acid is a measure of amount of acid present in the flour. Its determination is important to measure the perceivable acidity of the flour. The titrable acidity of whole maize flour and blended maize flour varied from 0.076±0.001% to 0.085±0.001% as presented in Fig 7. The average titrable acidity of whole maize flour was 0.076±0.001%. The average titrable acid content of maize flour blended with wheat was 0.083±0.001% while for the one blended with gram flour, it was 0.078±0.001%. The titrable acidity of wheat blended flour was higher than the gram blended flour. Hruskova and Machova (2002) studied the acid content of the degermed and whole maize flour and the results showed a trend similar to this.
Colour value
Flour colour determination is important because it affects the crumb colour of the finished product
i.e. flatbreads. The L of whole maize flour and blended maize flour varied from 65.41±0.02 to 75.52±0.02 as presented in Fig 8. The average colour value of whole maize flour was 70.05±0.02. The average colour change of the flour blended with wheat was found out to be 75.40±0.02 while for the one blended with gram flour, it was 65.42±0.02. The colour value for flour blended with gram flour was less than the flour blended with wheat. This is due to the colour difference of both wheat and gram. Gram flour when mixed with maize flour provides a darker colour, thus decreasing the L value. Wheat flour when mixed with maize flour makes it light in colour, thus increasing the L value. Jamin and Flores (1998) studied the colour difference for different varieties of corn flour and the results showed a trend similar to this.
Swelling power
Swelling power is defined as the wet weight of flour over its dry weight. The determination of swelling power of flour is important for a crunchy and chewable processing of flatbread. The swelling power of whole maize flour and blended maize flour varied from 22.31±0.01% to 31.06±0.01% as presented in Fig 9. The average swelling capacity of whole maize flour was 22.31±0.01%. The average swelling power of the flour blended with wheat was found out to be 30.74±0.01% while for the one blended with gram flour, it was 25.30±0.01%. The swelling power of maize flour blended with wheat was higher than the one blended with gram flour. The main reason for the difference in swelling power is the difference in the amylose content of wheat and gram flours. A similar trend was reported by Moorthy (2002) for the swelling capacity calculation of cassava flour.
Water holding capacity
Water holding capacity (WHC) is the ability of proteins to prevent water from being released or expelled from their three-dimensional structure. WHC plays an important role in developing food texture. The water holding capacity of whole maize flour and blended maize flour varied from 70.32±0.01% to 74.16±0.01% as presented in Fig 10. The average moisture holding capacity of whole maize flour was 70.34±0.01%. The average water retaining power of the flour blended with wheat was found out to be 74.09±0.01% while for the one blended with gram flour, it was 72.42±0.01%. Water absorption capacity of wheat blended maize flour is higher than the gram blended maize flour. The main reason for the difference in the moisture retaining capacity of the blended flours is the molecular structure which inhibits water absorption. A similar observation was reported by Butt and Batool (2010) while measuring the water absorption capacity (WAC) of rice, green gram and potato flour blended to wheat flour.
Oil holding capacity
Oil holding capacity is the amount of oil that can be absorbed per gram of the sample. It is important to determine OHC for the flavour retention of flatbreads and to improve their palatability. The oil holding capacity of whole maize flour and blended maize flour varied from 122.12±0.02% to 125.19±0.02% as presented in Fig 11. The average oil holding capacity of whole maize flour was 122.3±0.01%. The average oil holding power of the flour blended with wheat was found out to be 125.15±0.02% while for the one blended with gram flour, it was 124.13±0.01%. Oil holding capacity of wheat blended maize flour is higher than the gram blended maize flour. The main reason for the difference in the oil retaining capacity is the presence of high fat content. Similar findings were observed by
Kaushal et al., (2012) and
Aremu et al., (2007) while measuring the oil absorption capacity (OAC) of rice, green gram and potato flour blended to wheat flour.