African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 4, Num. 2, 1996, pp. 243-248

K. AHENKORA, M. A. KYEI^1, E. K. MARFO^2 and B. BANFUL

Crops Research Institute, P.O. Box 3785, Kumasi, Ghana
^1 University of Science and Technology, Kumasi, Ghana
^2 Ghana Standards Board, Accra, Ghana

(Received 13 April, 1994; accepted 21 August, 1995)

Code Number: CS96062
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ABSTRACT

False horn Apantu pa Plantains (Musa spp.) at the green, greenish yellow, yellow and brown colour stages of ripeness and their boiled/fried products were analysed for nutritional composition. The results showed that the nutritional composition of plantain pulp was diversely affected by natural ripening and processing. Significant changes (P<0.05) due to ripening occurred in the water, carbohydrate, sugar and starch contents. The degree of colouration is indicative of the composition of these components in plantain. Changes in mineral composition varied and were not consistent with most stages of ripeness. The processing methods employed significantly (P<0.05) reduced the protein, sugar, iron and copper contents of raw plantain pulp. The nature of the processing medium influenced the levels of fat and moisture in the products.

Key Words: Chemical composition, plantain, Musa spp., processing, natural ripening

RESUME

Les faux cornes Apantu pa plantains (Musa spp.) aux couleurs vertes, jaunes vert, jaunes et brunes apres murissage et leurs produits cuits e l'eau ou frites etaient analyses pour leur composition nutritive. Les resultats ont montre que la composition nutritive de la pulpe du plantain etait affectee d'une facon differente par le murissage naturel et les procedes de preparations. Des changements significatifs (P<0.05) de la quantite d'eau, de carbohydrate, de sucre et d'amidon sont observes avec le murissage. Le degre de coloration est un indicateur de la composition de ces composants dans le plantain. La composition minerale variait en n'etait pas consistente avec la plupart des stades de murissage. Les methodes de preparation employees reduisaient d'une facon significative la quantite de proteine, de sucre, de fer et de cuivre dans la pulpe du plantain cru. La nature du milieu de preparations influenait les niveaux de graisse et d'humidite des produits.

Mots Cles: Composition chimique, plantain, musa spp. procede de preparation murissage naturel

INTRODUCTION

Plantain (Musa spp.) is an important starchy staple that contributes to subsistence economies in West Africa. Plantain is attractive to farmers due to the low labour requirement for production compared with cassava, maize, rice and yam (Marriott and Lancaster, 1983). Sellers artificially induce ripening of plantains before marketing them, as ripe fruits generally attract the highest price. Ripening is done at room temperatures by placing the fruit into a room or box, with ethylene, acetylene, or smoke (Pantatisco et al., 1971; Salem et al., 1976). In Ghana, a more common practice is to allow slow ripening under ambient conditions.

Plantain fruits may be consumed unripe (green), yellow-green, or ripe. Understanding of the chemical changes associated with ripening may form the basis for expanding the utilisation of plantains. The chemical composition of plantains contributes to their acceptance as processed products in purees, flours, flakes or chips. Processing of plantains into such products is a useful means of using the plantain surplus during harvest and fruits rejected as unsuitable for export. Boiling and frying are two of the major traditional processing methods employed in plantain utilisation. There is little information on the effects of such processing methods on the chemical composition of plantains.

The objective of the present work was to determine the proximate (including sugar and starch) and mineral compositions of a popular Ghanaian False horn plantain Apantu pa during natural ripening (at the green, greenish yellow, yellow and brown colouration stages) and after processing (boiling and frying).

MATERIALS AND METHODS

Samples of fresh and green bunches of fully matured plantain Apantu pa were bought from a local market in Kumasi, Ghana. Plantain fingers were grouped into three based on size and weight. The fruits were stored at ambient conditions (25-28 C, 56-62% RH). Six fingers were selected randomly from each set for proximate analysis. The samples were oven dried at 63 C, milled to pass through 1mm sieve and stored in a refrigerator until analysis.

The standard AOAC (1984) methods were used to determine the moisture, crude protein, ash, crude fibre, crude fat and carbohydrate contents. The total ethanol soluble sugar and starch contents were determined by the method of Hansen and Miller (1975). Minerals were extracted from dry-ashed samples in HCl and determined by atomic absorption spectrophotometry (AOAC, 1984). Some fingers were boiled and deep fat-fried. For boiling, the skin was removed and the pulp sliced into sizeable pieces which were put in a 1000 ml beaker containing 400 ml water and 2 g salt (sodium chloride). This was then boiled for 15 minutes. Plantain pulp was also sliced (0.5 cm thick) and deep-fried in hot soybean oil until the colour turned golden brown. The samples were removed, put in a sieve and the oil drained off. Processed samples were oven-dried at 63 C and milled before they were analysed. Analysis were done in triplicates.

The results for green and ripening plantains and raw and processed plantains were compared on the basis of Students "t"-test for two averages (P <0.05).

RESULTS AND DISCUSSION

Proximate composition. The proximate composition and percent changes in proximate composition of false horn plantain during ripening and processing are shown in Tables 1 and 2, respectively. There was an increase in moisture content of 15% from the green to the brown-flecked stage (fully ripe). The increase in the water content of the pulp during ripening is consistent with the report by Aboua (1991) and could be due to the movement of water from the peel (Marriott and Lancaster, 1983). Boiling increased the moisture content of plantains while frying decreased the moisture content. Green plantains absorbed more moisture when boiled and lost more moisture when fried than yellow or fully ripe plantains. The increased water content of the boiled products is due to the cooking medium (water).

Table 1

Table 2

Apantu pa contained little protein (2%) which did not change during the ripening process but decreased by 50% when boiled or fried. The result of the ripening process is in contrast to the observation made in banana where the protein content increased significantly (Brady et al., 1970). Change in the protein content of plantain as a result of processing could be due to leaching of nitrogen- containing compounds to the cooking medium or possible interaction of proteins with other food components.

The fat content of plantains changed slightly with ripening or boiling but increased drastically with frying. The changes in fat content of the fried products were due to fat being absorbed from the frying medium (oil).

The ripening process slightly affected the crude fibre content of plantains. Boiling, however, decreased the fibre content whilst frying increased the fibre content of plantain products. The decrease and increase in fibre as a result of boiling and frying, could be due to the gain in moisture and the loss of moisture with the boiling and frying processes, respectively.

Ash content increased with ripening. Changes in ash content due to processing did not follow a consistent trend and seemed to be dependent on the processing method and the stage of ripeness of the plantain.

Apantu pa contained 42% carbohydrate at the raw green stage which decreased with ripening. Boiling decreased the carbohydrate content whilst frying increased the carbohydrate content. This observation could be due to the respective moisture contents of the boiled and fried products.

Sugars formed 2% of the dry weight of green plantain and rose to 63% in the ripe plantain. Total sugar contents at the green, greenish-yellow, yellow and brown-flecked colouration stages of ripeness were significantly different. Boiling and frying decreased the sugar content of plantains and could be due to possible dissolution and leaching of sugars. Both processing methods reduced the sugar levels of green plantains more than yellow or brown-flecked plantains.

Starch formed 83.7% of the pulp dry weight of green plantain and decreased gradually to 11.01% in the ripe plantain . Starch content at the green, greenish-yellow, yellow and brown-flecked colouration stages of ripeness were also significantly different. Starch is stoichiometrically converted to sugars during ripening with the formation of sucrose, glucose, and fructose (Ketiku, 1973). Significant changes in starch content were observed in the boiled yellow and boiled brown-flecked products.

Mineral content. The mineral content and changes in mineral content of false horn plantain during ripening and processing are shown in Tables 3 and 4, respectively. Apantu pa at the green stage was rich in magnesium, potassium, iron and calcium. Similar findings have been made with banana and other plantain varieties (Marriott and Lancaster, 1983). Unlike other foods, the iron content in plantain is 100% utilisable for human nutrition (Loeseck, 1950). There were varied changes in mineral composition of plantains during ripening and processing. Potassium content decreased by 1% with ripening and processing. The calcium content of plantain showed small and inconsistent increases during ripening and small decreases with processing. Changes in magnesium content due to ripening or processing were insignificant and the trends were inconsistent. Significant increases in mineral content due to ripening were observed for iron, copper and zinc. However, the increases were not consistent with the stage of ripeness. In general, boiling and frying decreased the iron, copper and zinc contents.

Table 3

Table 4

The nutritional composition of false horn Apantu pa plantain was diversely affected by natural ripening and processing. The most distinct changes in chemical composition for the different stages of ripeness occurred in the water, carbohydrate, sugar and starch contents. The nutritional composition of plantain products was dependent on the processing method employed and the stage of ripeness.

REFERENCES

Aboua, F. 1991. Chemical and physical changes in plantains (Musa paradisiaca) during ripening. Tropical Science 31:183-187.

AOAC. 1980. Official Methods of Analysis. W. Horwitz (Ed.). 13th Edn. Association of Official Analytical Chemists.

Brady, C. J. 1970. An increase in protein synthesis during ripening of banana fruit. Phyto-chemistry 9:1037-47.

Hansen, J. and Miller, J. L. 1975. Percolation of starch and soluble carbohydrate with anthrone. Dept. of Plant Physiology and Anatomy. Royal Veterinary and Agriculture University. Thirvaldesrej 40, K.K. 1871. Copengahen.

Ketiku, A. O. 1973. Chemical composition of unripe (green) and ripe plantain (Musa paradisiaca). Journal of Science, Food and Agriculture 24:703-707.

Loeseck, W.H. 1950. Bananas. Interscience Publishers, New York, Vol.1. 2nd edition. 120pp.

Marriott, J. and Lancaster, P.A. 1983. Bananas and Plantains. Handbook of Tropical Foods. Harvey T.C. Jr. (Ed.), pp. 85-142. Marcel Dekker, Inc.

Marriott, J., Robinson, M. and Kakari, S.K. 1981. Starch and sugar transformations during the ripening of plantain and bananas. Journal of Science, Food and Agriculture 32:1021-1026.

Pantatisco, Er. B. and Mendoza, D. B. 1970. Production of ethylene and acetylene during ripening and charring. Phillipine Agriculture 53:477-448.

Salem, E.A., Rizk, S.S., Eissawy, M.T. and Yehia, M. 1976. Banana fruit ripening. 1. Comparative study of the convential methods used in Egypt. Agriculture Research Review 54:77-81.

Copyright 1996 The African Crop Science Society

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