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The process of fermenting maize, sorghum, millet or rice to produce ogi not only removes parts of the maize kernel such as the seed-coat and the germ, but also involves washing, sieving and decanting, all of which induce changes in the chemical composition and nutritive value of the final product. Akinrele (1970) reported on specific nutrients of a number of ogi samples produced in different ways: unfermented and fermented with Aerobacter cloacae, Lactobacillus plantarum and a mixture of the two bacteria. He compared the values found with those from the traditionally fermented product. Judging from the ratio of amino nitrogen to total nitrogen, the author reported that protein was degraded to a very small amount by any bacterial species. When compared with the unfermented ogi, A. cloacae appeared to synthesize more riboflavin and niacin, which did not take place with L. plantarum. Traditionally produced ogi had more thiamine and slightly lower values of riboflavin and niacin than that made with maize and A. cloacae. In any case the changes were small, and smaller if compared with whole maize, whereas in comparison with degermed maize, the ogi products contained more riboflavin and niacin. Akinrele (1970) and Banigo and Muller (1972) reported on the carboxylic acids in ogi and found lactic acid in greatest concentration (0.55 percent) followed by acetic acid (0.09 percent) and smaller amounts of butyric acid. The latter investigators suggested levels of 0.65 percent for lactic acid and 0.11 percent for acetic acid, responsible for the sour taste, as goals for flavour evaluations. Banigo, de Man and Duitschaever (1974) reported on the proximate composition of ogi made from common whole maize which was uncooked and freeze-dried or cooked and freeze-dried after fermentation. Changes were relatively small in all major nutrients, with a slight increase in fibre and a decrease in ash content when compared with whole maize.
These authors also reported on amino acid content; they found no differences between maize flour and ogi for all amino acids including the essential ones. The ogi samples, however, had about twice the amount of serine and somewhat higher values for glutamic acid. Adeniji and Potter (1978) reported that ogi processing did not decrease the protein content of maize, but total and available lysine were significantly reduced. On the other hand, tryptophan levels were more stable and in two samples increased, probably because of fermentation. These authors also found an increase in neutral detergent fibre and ash but no change in lignin. Akingbala et al. (1987) found a decrease in protein, ether extract, ash and crude fibre in ogi as compared with maize that was processed as a whole grain or dry milled.
Nutritional evaluations of ogi and other maize-fermented products are not readily available. Adeniji and Potter (1978) found a substantial decrease in protein quality of drum-dried common maize ogi, which they ascribed to the drying process. These same authors reported significant losses in lysine Several authors have more recently tested maize and sorghum and reported that fermentation improved the nutritional quality of the product. Akinrele and Bassir (1967) found net protein utilization, protein efficiency ratio and biological value of ogi inferior to those values in whole maize, even though some increase in thiamine and niacin was obtained. It has been indicated that some of the micro-organisms responsible for ogi fermentation, such as Enterobacter cloacae and L. plantarum, use some of the amino acids for growth. This together with the elimination of the germ from kernels explains the very low protein quality of ogi and similarly produced maize products. However, there are some exceptions, such as kenkey and pozol, both products in which the maize is fermented with the germ. Although protein quality values are not available for kenkey, Cravioto et al. (1955) found higher levels of tryptophan and available lysine which suggested higher protein quality than in raw maize or lime-treated maize. More recently, Bressani (unpublished) found the fermented product to be higher in protein quality than raw maize, but not different in quality from lime-cooked dough.
Use of QPM
Adeniji and Potter (1978) used high quality protein maize to make ogi and found similar results to those from common maize, except that the protein quality was higher (although lower than that of the original raw maize). Pozol made from QPM has significantly higher protein quality than raw QPM (Bressani, unpublished data).
Arepa flour is made in a dry milling process which removes the pericarp and the germ from maize. Therefore, arepa flour may be expected to differ from whole maize flour, and this was in fact reported by Cuevas et al. (1985). The protein, ether extract, fibre and ash content of arepa flour from both white and yellow maize were lower than in whole maize. The same is true for thiamine, riboflavin and niacin as well as for calcium, phosphorus and iron. These changes evidently result from the removal of the germ and seed-coat.
Arepa flour has been subjected to biological assay for protein quality by Chavez (1972a). He reported a decrease of about 50 percent in protein quality from maize (0.74) to arepa (0.33), although there was some increase in protein digestibility.
Use of QPM
High protein quality maize has been used to make arepas. Chavez (1972b) found the process to reduce nitrogen, lysine and tryptophan, thiamine and niacin and attributed this to germ removal. Protein quality was also significantly less than in whole maize, but was nonetheless superior to that of maize and arepas from normal maize. All products - tortillas, ogi, pozol, kenkey and arepas made from QPM are of better protein quality and energy value than the products made from common maize.
The main maize products for food use derived from dry milling include flaking grits, coarse or fine grits, maize cones and maize flour. They are products from which the pericarp and germ have been eliminated and they differ from each other in granulation, with flaking grits having the largest particle size and flour the smallest. Basically, their chemical compositions based on food composition data are very similar.
The protein quality of these products, as with most dry-milled maize products, is inferior to that of the original whole grain. If there are any changes, these come about from the processes used to turn such products into the different forms in which they are consumed. For example, the protein digestibility of maize meal was reported by Wolzak, Bressani and Gómez-Brenes (1981) to be 86.5 percent and that of corn flakes 72.0 percent. A significant diminution of protein quality also takes place since available lysine decreases.
Studies on dry milling of QPM, particularly the hard-endosperm types, are not readily available. Wichser (1966) found yields of 8.8 percent grits from milled QPM, while the yield of grits from maize hybrids was about 17 percent. The yields of meal and flour were essentially the same from QPM and hybrid maize. However, the fat, protein, fibre and ash contents in QPM grits, breakfast cereal and flour were higher than those in similar products from hybrid maize.
Not much information on the nutritional value of QPM dry-milled products is available; however, Wichser (1966) showed the endosperm of QPM to have a net protein ratio (NPR) of 76 percent of the value of casein (100 percent), while the endosperm from hybrid maize had an NPR of 47 percent of the value of casein. These results are very similar to those for maize flour made for arepa production from QPM and common maize as shown by Chavez (1972a).
Maize in its different processed forms is an important food for large numbers of people in the developing world, providing significant amounts of nutrients, in particular calories and protein. Its nutritional quality is particularly important for small children. Table 23 shows the consumption of maize as tortillas or lime-treated maize by children in Guatemala. Amounts varied from 64 to 120 g per day, providing about 30 percent of the daily protein intake and close to 40 percent of the daily energy intake. Garcia and Urrutia (1978) reported an intake of 226 g of tortillas by weaned three-year-old children, providing about 47 percent of their calories.
Although these findings are not basically bad, adequate supplementary foods are often not provided or are given only in insignificant amounts. Food legumes are the most readily available supplementary food in developing countries; however, the amounts are generally very small (Flores, Bressani and Elías, 1973). The average intake of beans per age group for the six countries in Central America was 7, 12, 21 and 27 g per child per day at 1, 2, 3 and 4/5 years, respectively. On the basis of 22 percent crude protein in beans, the amounts of protein provided by this food were 1.5, 2.6, 4.6 and 5.9 g, respectively; however, amounts of digestible protein on the basis of a true digestibility of 70 percent were only 1.0,1.8,3.2 and 4.1 g. Thus beans provided about 14, 18, 22 and 30 percent of the dietary protein in the total intake from maize and beans. These amounts and their supplementary effects were very small, particularly for the one- and two-year-old children.
TABLE 23 - Maize consumption and its contribution to daily calorie and protein intake of children in a rural area of Guatemala
|Age (years)||Maize intake (g/day)||
|Maize (g/day)||Total (g/day)||Percent of total from maize||Maize (cal/day)||Total (cal/day)||Percent of total from maize|
Source: M. Flores (cited in Bressani. 1972)
Data for 1979-1981 from FAO (1984) showed that 22 of 145 countries had a maize consumption of more than 100 g per person per day as indicated in Table 24, which also gives the calories and protein that maize provides. It should be pointed out, however, that 1960-1962 figures from FAO food balance sheets (FAO, 1966) were higher for some countries than the 19791981 figures. The figures confirm the importance of maize as a staple food in some Latin American countries, particularly Mexico and Central America, as well as in some African countries. It follows that if the maize intake is high, maize contributes significant amounts of calories and protein to the daily intake of people in these countries.
Table 25 summarizes maize intake, calories per day and protein per day among the rural and urban populations of the six countries of Central America. Two general trends are evident. The first is that maize intake decreases from north to south. The cereal grain that replaces it is rice. The second trend is that intake of maize is higher in rural than in urban areas. In at least three countries maize makes up the greatest proportion of all the ingested food in the rural sector and is therefore an important source of nutrients in the diet. The table shows that maize provides up to 45 and 59 percent of the daily intake of calories and protein respectively.
TABLE 24 - Maize intake and its calorie and protein contribution to the daily diet
|Country||Intake (g/person/day)||Calories (per person/day)||Protein (g/person/day)|
|Cape Verde||334.1||1 052||28.0|
|South Atrica, Rep.||314.7||961||24.6|
|Tanzania, United Rep.||129.1||421||10.0|
Sources: FAO, 1984; *FAO, 1966
TABLE 25 - Importance of maize consumption in rural areas
|Country||Urban maize intake (g/day)||Rural maize intake (g/day)||
Rural calorie intake (per day)
Rural protein intake (g/day)
|From maize||Total||From maize||Total|
|Guatemala||102||318||1 148||1 994||27.0||60|
|Et Salvador||166||352||1 271||2 146||29.9||68|
|Costa Rica||14||41||148||1 894||3.5||54|
Source: INCAP, Guatemala, 1969
Although this information was compiled from dietary surveys conducted in 1969, figures have not changed significantly in recent years. For example, in 1976 average consumption in El Salvador varied from 146 to 321 g per person per day; in Honduras in 1983 consumption in different regions varied from 1 1 1 to 246 g per person per day; and in Costa Rica in 1986, intake varied from 14 to 31 g per person per day. Chavez (1973) indicated that about 45 percent of the national calorie intake is provided by maize in Mexico. In poor rural areas men may consume about 600 g of maize and women about 400 g. On this basis the importance of the nutritional quality of maize is obviously great. Although all nutrients are of interest, the quality of protein has received more attention from researchers.
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