I.1 Nutritional elements

Maize is an important element in the diet of the population of developing countries, especially in Africa and Latin America. In some cases (e.g. Malawi), maize may account for 80 to 90 per cent of the total calorie intake of the rural population. Yet maize is deficient in a number of essential nutrients, and excessive reliance on maize diets could result in severe diseases such as pellagra. Consequently, a number of countries have implemented various measures for the enrichment of maize meal for human consumption (e.g. addition of various vitamins, soya bean meal, groundnut flour).

Given the deficiency of maize in a number of essential nutrients, it is paradoxical that a number of developing countries have allowed or even favoured the adoption of milling technologies which further reduce the amount of these nutrients per unit of output as well as the total amount of maize meal for human consumption per tonne of processed maize. Reasons for the increasing adoption of these technologies will be provided later, and suggestions will be made for the promotion of milling techniques consonant with desirable socio-economic objectives. It will first be useful to indicate the effect of alternative milling technologies on the nutritional value of the meal produced.

Table I.1 provides estimates of the main nutrients which constitute the three types of maize meal consumed in developing countries: whole meal, bolted meal (partly de-germed) and de-germed (super-sifted) meal. While the number of calories per 100 grams of flour are approximately equal for the three types of meal, the proportions of important nutrients per unit weight of flour are generally much larger for whole meal than for bolted and super-sifted meal. This is particularly true for calcium, iron, niacin, riboflavin and the fat content of the meal. The production of sifted meal by roller mills also removes two important types of proteins (globulins and glutelins), leaving zein which is a poorer source of protein.¹ Furthermore, enriched sifted meal is in general nutritionally less adequate than whole meal.

¹ Source: see Stewart (1977)

Table I.1

Nutrient composition of different types of maize meal

Product/Nutrient	Whole meal	Bolted meal (partly de-germed)	De-germed meal (super-sifted)
Moisture (percentage)	12-13	12-13	12-13
Calories per 100 gr	353-356	360	363
Protein (percentage)	9.3-9.5	9.3	7.9-8.4
Fat (percentage)	3.8-4.5	Variable (>2)	1.2-2.0
Carbohydrates (percentage)	73.4	Variable (>74)	78.4
Fibre (percentage)	1.9-3.0	0.7-1.0	0.6-0.7
Ash (percentage)	1.3	n.a.	0.5
Calcium (mg per 100 gr)	7-17	6	5-6
Iron (mg per 100 gr)	2.3-4.2	1.8	1.1-1.2
Thiamine (mg per 100 gr)	0.3-0.45	0.35	0.14-1.18
Niacin (mg per 100 gr)	1.8-2.0	1.3	0.6-1.0
Riboflavin (mg per 100 gr)	0.11	0.09	0.08

Note: Variations in data according to sources may be explained by variations in the raw materials analysed and/or variations in the quality of meal.

Sources: Schlage (1968); FAO (1968); FAO (1953); FAO (1954); Uhlig and Bhat (1979).

Table I.2 provides estimates of the minimum daily consumption of whole meal and sifted meal (de-germed) which will be required for an adult's daily needs of four essential nutrients: iron, thiamine, riboflavin and nicotinic acid. The table shows that, should adults rely exclusively on maize, they will need to consume two to seven times more de-germed meal than whole meal in order to satisfy their daily needs of these four nutrients. Obviously, few people will rely exclusively on maize for their diet, and the estimates provided in Table I.2 are of a purely theoretical nature. However, as to be shown later, the deficiency of de-germed meal in a number of essential nutrients could have serious repercussions on the diet of low-income groups in developing countries.

Table I.2

Minimum daily consumption of whole meal and super-sifted meal
(Amounts of meal required in grams to provide an adult's daily needs of one mineral and three vitamins)

Maize meal	Substances
	Iron	Thiamine	Riboflavin	Nicotinic acid
Whole meal	233	357	1,076	1,066
Sifted meal	424	2,500	4,670	2,670

Source: FAO (1968); Harper (1974).

Milling techniques also affect the availability of flour for human consumption. The extraction rates of bolted or sifted meal per tonne of processed maize are much lower than those of whole meal. Table I.3 shows that extraction rates for whole meal vary from 97 per cent to 99 per cent while those for bolted and sifted meal vary respectively from 80 per cent to 96 per cent and from 60 per cent to 75 per cent. On the other hand, the proportion of by-products may be as high as 40 per cent in the case of sifted meal whereas generally it does not exceed 3 per cent for whole meal. These by-products are used either as animal feed or for oil extraction. The production of bolted or sifted meal may thus have important repercussions on consumption by low-income groups for the following reasons.

First, from the purely quantitative point of view, and given the above extraction rates, approximately 20 to, 40 per cent of cultivated maize will not be available for direct human consumption if, for example, it is used to produce sifted meal instead of whole meal (the corresponding percentages for bolted meal will be 3 to 17 per cent). The lower extraction rates associated with the production of sifted and bolted meal should be of little consequence for countries producing a net surplus of maize (e.g. for export or further processing into oil or animal feed). On the other hand, countries which do not grow enough maize to fully satisfy the needs of their population may face larger shortages of maize meal if sifted rather than whole meal is produced. If these countries do not make up for these shortages by importing maize or other kinds of grain, in the absence of price controls the low-income groups will either have to pay higher prices for the available supply of maize or cut down consumption. In either case as shown in table I.3, they will suffer from the lower supply of maize flour due to the low extraction rates of sifted maize mills (i.e. roller mills).

Table I.3

Extraction rates per 100 kg of maize
(percentages)

Product	Use
	Flour for human consumption	By-product used for animal feed or oil extraction
Whole meal	97-99	1-3
Bolted meal	80-96	4-20
Sifted meal	60-75	25-40

Source: Stewart (1977) and Uhlig and Bhat (1979).

Secondly, the use of by-products (bran and germ) as animal feed (e.g. for cattle or poultry) may not fully compensate for the low extraction rates associated with the production of sifted meal: if these by-products are used to increase the production of meat, their nutritional value will not generally exceed 10 per cent of that of bran and germ (i.e. the conversion of bran and germ into meat results in a 90 per cent loss of the nutritional value of these two by-products). Furthermore, it is very unlikely that low-income groups will be able to afford to improve their daily diet by buying the meat produced.

Thirdly, it may be noted that by-products are generally locally marketed or exported as animal feed and that few developing countries have maize oil extraction plants. In any event, however, the extraction of oil from the by-products may not justify the production of sifted meal. Two important factors should be considered before deciding to invest in a maize oil extraction plant. These are:

- whether a sufficiently large and regular supply of by-products will be available to ensure a continuous high capacity utilisation of the plant, and therefore competitive (non-subsidised) retail prices of oil; and

- whether oil should not be obtained from some other raw material given the importance of maize for direct human consumption.

The previous analysis of the nutritional value of the three types of maize meal indicates that in terms both of quality and quantity, the production of whole meal is to be preferred to that of sifted or bolted meal if the satisfaction of the basic needs of low-income groups constitutes a major development objective. Other factors may, however, vitiate the above analysis, as indicated below.