By Shamsul Islam Naz
A team of breeders headed by an expert Mr. Khalid Aziz of the University of Agriculture Faisalabad has developed a new method of oil extraction from maize, because of which the country can save a substantial amount of foreign exchange, now being spent on the import of edible oils.
Dilating on the theme of “Maize in Human Nutrition”, the experts have pointed out that “maize possesses nutritive energy of tremendous value, for the growth of small children and also occupies an important position in the high-energy rations for the fattening of poultry birds and livestock animals. The study suggests that “packets of ration should be prepared making use of maize meal, cottonseed meal and sugarcane molasses for feeding animals. This is how a large acreage of land being utilized presently for growing fodder can be freed and prepared for growing food for human consumption. “In Europe and America this practice has resulted in increased efficiency of livestock in respect of milk and meat production”.
According to this study “a major chemical component of maize kernel is starch which provides 70 to 73 per cent of kernel weight. Other carbohydrates are simple sugars present as glucose, sucrose and fructose. After starch, the next largest chemical component of the kernel is protein. The protein contents vary from 8 to 11 per cent of the kernel weight. “Both the quality and quantity of maize kernel protein are limited. It is deficient in essential amino acids like lysine and trytophan. This is due to the abundance of zein fraction of protein in the endosperm, which is very low in lysine content and lacking in tryptophan”, the study observes.
According to the study, the discovery of opaque-2 and floury-2 genes has given way to quality protein maize (QPM). This gene reduces the concentration of zein by some 30 per cent due to which, the lysine and tryptophan content is relatively higher in QPM varieties than in common maize. Concerted breeding and genetic engineering efforts are needed to convert commercial maize varieties into QPM varieties.
The study reveals that a wide range of variability is available for oil content of the germ ranging from 3 to 18 per cent which is genetically controlled and influenced by external environmental factors such as season of growing, soil fertility etc. Maize oil is highly prized because of its low-level of saturated fatty acid content i.e., on an average 11 per cent plasmatic and 2 per cent stearic acid. “On the other hand, it contains relatively high levels of poly unsaturated fatty acids, mainly linoleic acid with an average value of about 24 per cent. Furthermore, maize oil is relatively stable since it contains only small amounts of linoleic acid (0.7 per cent) and high levels of natural antioxidants. “The sugar content in the maize kernel ranges between one to 3 per cent, with sucrose being the major component, found mostly in the germ. Within 12 days after pollination the sugar content is relatively high, while starch is low. But as the kernel matures the sugar decline and starch increases. That is why the fresh maize ears are so sweet and liked by the people,” the study claims. “Besides, the germ of maize kernel is also a rich source of mineral and the most abundant mineral is phosphorus. Two fatsoluble vitamins, provitamin A, or carotenoids, and vitamin E are present in the maize kernel with the former mainly present in the endosperms and the latter in the germ. Variable amounts of water soluble vitamins such as thiamin, riboflavin and nicotinic acid have been found”, the study goes on to say.
According to the study, variability in chemical composition of maize kernel is under the influence of genes, therefore, it can be subjected to improvement through concerted plant breeding efforts. Through the application of genetic engineering, success has been achieved in changing and improving the carbo-hydrate composition and the quantity and quality of oil and protein content of maize kernel. “The researchers have indicated that maize varieties with waxy or sugary genes can be tailored which should be having better nutritional value for monogastric animals because of the greater digestibility of the starch they produce”.
The study also reveals that the quantity and quality of protein in maize varieties can be improved through selection. In a study at Illinois University it was observed that the protein content could be increased from 10.9 to 26.6 per cent in maize strains after 65 generations of selection. “Selection over 65 years increased oil content from 4.7 per cent to 16.5 per cent which could be accomplished by increasing the germ size. A common problem with quality improvement in maize and many other crop plants is that of low yield. Total oil content, fatty acid content have also shown to be genetically controlled thus likely to be improved through breeding efforts, as seen by varieties in linoleic acid content in maize oil”.
The study further points out that being a short duration crop, and with the possibility of raising two crops a year, maize is a cereal with great yield potential. If given with proper package of agronomic practices including choice of a good quality seed, proper sowing time, adequate supply of fertilizers, pesticides and Irrigation regime, maize can surpass any other cereal in yield. “In Pakistan the area under maize is increasing gradually at an annual rate of 1.5 per cent which is indicative of the fact that the crop is gaining popularity among farmers. The farmers have started thinking about the cultivation of this crop particularly in the areas where cotton has failed to show satisfactory results”.
