Food Resctwh lnternc~tional26 ( 1993) 187-193

Chemical changes in relation to mode and degree of maturation of plantain (Musa paradisiaca) and

banana (Musa sapienturn) fruits

J. 0. Offem & 0. 0. ‘Thomas Depurtment of’ Chemi.str.v, University of‘ Caluhrrr. PMB II IS. Culahur, Nigeritr

Changes in the proximate and mineral constituents of the plantain and banana fruits were monitored with time, beginning 60 and 90 days from bunch visible emergence, respectively, for fruits allowed to ripen on the plants, and ripen off the plants. For fruits on the plants, the point of minimum moisture content for the pulp and/or peel corresponded to maximum maturity for both the plantain and the banana fruits. Protein levels increased with time in the fruits on the plants, and for the same fruit ages, there was slightly more protein in the plan- tain than the banana. Sugar content in both fruits increased gradually at first until after 92 days, then increased sharply at onset of ripening and continued increasing through the rest of the experimental period. At identical ages, har- vested fruits contained far more sugar (p > 0.05) than fruits allowed to ripen on the plants. Energy values increased gradually with time and reached a maxi- mum at maximum maturity of both fruits. The values were consistently higher for the plantain than the banana (t-test. p<O,Ol). Virtually all the elements studied had statistically higher values in plantain fruits than in bananas. No reason could be advanced for this phenomenon.

Keywords: mode and degree, fruit maturation. proximate and mineral composi- tion, plantain, banana.

INTRODUCTION

The plantain (Muss paradisiaca) and banana (Muss sapienfum) plants are permanent crops which grow prolifically in most tropical regions of the world. In Nigeria they flourish in the warm and humid southern parts of the country where optimum growth conditions of 27°C and 2000 mm rainfall per annum (Phillips, 1977) are easily at- tained. They both belong to the genus Muss of the family Musuceae and many authors point out that any distinction between the two is artificial and can both be referred to as bananas. Morpho- logically, the two can be distinguished only at the fruiting stage.

In Nigeria, the fruits of these crops have re- mained essential staples to not only the people of the southern parts of the country, where they are

Food Research InternutionulO963-9969193/$06.00 ‘(5 1993 Canadian Institute of Food Science and Technology

IX7

produced in abundance, but also to those in the northern parts who provide ready markets for the excess bananas and plantains from the south. Fresh, mature, unripe banana and plantain pulp can be consumed roasted, or boiled or fried into chips or prepared into porridge or sun-dried and milled into flour which is used to prepare ‘amala’ ~- a favourite starchy Nigerian dish (Ukhun & Ukpebor, 1991). Ripe, peeled bananas are most often eaten raw while the plantain counterpart, which contains more starch (Ladele et al., 1984), is preferred eaten after slicing into flakes and deep-fried in vegetable oil as ‘dodo’.

All the year round, the fruits of these two plants can be found in one Nigerian market or the other. The quantity found varies, depending on the season. This implies that even during harsh weather with strong winds or high temperatures, which are known to scorch the pseudostems of these plants, some bunches could still be found on them at various stages of maturation. Such plants

sometimes fall over, as a result of broken pseudo- stems, with their fruits which may not be mature enough to ripen. The concerned farmers may allow such fruits to remain on the fallen plants for some time more to improve on the maturation. In any case, such fruits hardly attain that desired maturity found in the normally grown plants (Edet, 1988). Furthermore, even for the normally grown plants, the stage of harvesting the bunch is deter- mined by the persona1 judgement of the individual farmer which may differ from one farmer to the other (Offem, J. 0.. 1989, pers. comm.). It is also possible that a not-so-mature bunch is harvested for sale when the farmer is in dire need of money (I ITA, 1984). Therefore, in every plantain/ banana market, one finds bunches of these fruits being sold at various stages of their maturation. The customer has little or no scientific method to assist him 01 her to determine what he or she is paying for.

The literature on the chemistry of the Nigerian plantain or banana fruit is very scanty indeed. Ketiku (1973) and Ladele rt al. (1984) have re- ported some results on the chemical composition of ‘green’ and ‘ripe’ plantains (Muss parurlisiaccz). The manganese content (Offem & Edet. 1989). phosphorus content (Offem & Edet. l99l), car- bonatexarbon content (Edet of rrl.. 1987) of some organs of the plantain plant, including the fruit, have been reported. Recently, Offem & Njoku ( l992a,h) reported on the distribution of mineral elements in the leaves of MUSU puvadisiucu at diff- erent stages of growth, and on the mineral distri- bution in the fruits.

The taste of these fruits is most often at its best when harvested at maximum maturation, but the farmer runs the risk of the fruits getting ripe the very next day or a few days after (Offem & Njoku, 1992h). Maximum maturation is attained by those fruits developing on a normally growing plant at the point just prior to the onset of ripening (Offem. J. O., 1989, pers. comm.) Once ripening sets in any bunch, the fruits all have to be con- sumed within hours or else they go bad. On the other hand, harvesting the bunch earlier than at maximum maturation delays the advent of ripen- ing but at the expense of the appropriate tastes and flavours (Edet. 1988). In a series of works aimed at highlighting the chemical properties of these fruits at any given state of maturation, we intend to inform the consumer of the properties of the plantain or banana being bought and educate the farmer on how best to know the appropriate time to harvest a bunch. Here we present the work

on the chemical changes of the fruits in relation to the mode and degree of maturation.

MATERIALS AND METHODS

The banana samples used in this study were har- vested from a commercial plantation at Odukpani, along the Calabar-Itu express way, about 36 km north-west of the University of Calabar. C‘alabar. Nigeria. The plantain samples also came from a commercial plantation but this time located in the Qua River Swamp at Idundu, along the Ekang road, about 10 km north-east of the University of Calabar. Calabar, Nigeria. Both plantations were free from any artificial fertilization. In each plan- tation, six plants were identified, labelled and used in this work. The plants were chosen on the basis of sighting an emerging bunch (just at the point where it starts emerging) within a I-week scan period. The exact day of sighting each bunch was noted and the bunch allowed to grow. The plants were supported with fork-like sticks to prevent them from being blown down by strong winds.

The six plants of each plantation were consti- tuted into two groups (A and B) of three plants each. Fruit samples were harvested from group A plants for analysis starting 60 days from \vhen the emerging bunch was sighted and at the intervals described in the tables. All three bunches were al- lowed to remain on the plants throughout the cx- perimental period. As for the group B plants. each bunch was harvested after 90 days of sighting its emergence and separately covered with leaves in the shade within the plantation and allowed to ripen. It was earlier found that maximum matura- tion in these fruits is attained on about day 90 of bunch emergence (Otfem. J. 0.. ! WO. pers. comm.). During this period, samples were taken for analysis at the intervals listed in the tables.

Sampling of each fruit bunch for analysis was done systematically. At each sampling stage. the central fingers in the top of the second hand of each bunch were analysed first, followed by those to the left and then to the right in that order until the top row was exhausted. before beginning with the bottom row, also in that order. (‘ounting of the hands of the bunch hanging from the plants in the natural position followed a spiral direction (Gottreich rt ul., 1964). All sample harvesting was done at noon and a sharp steel knife uas used in cutting the fingers off the bunch and in slicing oH both ends of the fingers.

Muturation of plantain urd hanana jhits 189

Each finger was washed with deionized distilled water wiped gently with a clean cotton gauze and kept overnight to dry in an air-conditioned room (approx. 1YC). These were individually and care- fully separated into the peel and the edible part (pulp). Each component was chopped into tiny pieces and homogenized in an electric blender (National Model MX-29 IN) for 10 min. The moisture content was measured by oven-drying about 2 g portions of the homogenized samples at 105°C to constant weight. The total lipids were extracted and determined according to the Bligh & Dyer (1959) method. Total protein (crude pro- tein, N X 6.25) and other proximate constituents were determined according to the AOAC (1984) standard procedures. The samples were analysed for sugar content using the modified method of Dubois et ul. (1956) and for starch (Kent & Amo, 1967). The nitrogen free extractives (NFE) were calculated by difference and include values of total sugars and starch (Muller & Tobin, 1980). The en- ergy content was determined by multiplying per- centage crude protein, crude lipids and NFE (total crude carbohydrates) with the factors 4, 9 and 4. respectively (Bogert et al., 1973; Osborne & Voogt, 1978; Gaman & Sherrington, 198 1).

Mineral analysis was done by dry-ashing at 450°C for 3 h followed by analysis using an atomic absorption spectrophotometer (Schimadzu AA0678/GP-7 computerized model, courtesy of the NNPC Refinery’s laboratory at Port Har- court) according to the procedures of Isaac & Johnson (1975). Phosphorus content is triple acid digested extract was determined by the vanado- molybdate calorimetric method (AOAC, 1984) using a Pye Unicam SP6 Model 450 spectropho- tometer.

Statistical analyses

Analyses of variance (ANOVA) for changes in the chemical parameters where indicated, were done (Snedecor & Cochran, 1956). t-test analyses were also done, where indicated, in accordance with de- scribed methods (Harris, 1982).

RESULTS AND DISCUSSION

The proximate compositions of plantain and ba- nana fruits when bunches are allowed to mature and ripen on the plants are given in Table 1, while those for bunches harvested at maturity and al-

lowed to ripen off the plants are given in Table 2. Previous works on plantain (Ketiku, 1973; Ladele et al., 1984) and on banana (Askara, 1973; Lii et al., 1982) were done on fruits purchased from local markets with no history of age and/or degree of maturation. Awan & Ndubizu (1978) on the other hand, used plantain fruits described as ‘har- vested at full maturity’ - an expression which is rather vague. The results presented here monitor the changes in proximate composition of these fruits with time of growth, maturation, and ripen- ing. Values are presented for the fruit pulp while the moisture content of the fruit peel is reported as well.

From Table 1, the fruit peel consistently had more moisture than the fruit pulp in both the ba- nana and the plantain but the differences were sta- tistically insignificant (p > 0.05). Moisture levels in the banana pulp and peel decreased steadily from 61.5 and 63.2%, respectively, on day 60 after bunch emergence to a minimum of 55.6 and 57~1’!% respectively, at day 92 before rising rapidly (onset of ripening) and continued rising for the rest of the experimental period. A similar trend is observed in the plantain pulp and peel whose moisture content decreased to a minimum at day 93 before increasing steadily through the rest of the experimental period. It has earlier been re- ported (Offem & Njoku, 1992h) that the point at which minimum moisture content of the plantain fruit peel is achieved while the bunch is growing on the plant corresponds to the point of maxi- mum maturity of the fruits. In the present study, this conclusion is further confirmed and extended to the banana fruits as well. Moisture content in- creased in both pulp and peel and in both the ba- nana and plantain as ripening progressed. This is in agreement with Ukhun and Ukpebor (1991) who, working with instant plantain flour, ob- served higher moisture contents in instant plantain flour made from ripe plantain than that made from unripe plantain. A similar observation had earlier been made by Awan & Ndubizu (1978). The pulp of the banana statistically had more moisture than the plantain pulp (pIO.05).

Contrary to Table 1, Table 2 shows that the pulp of both the plantain and banana contained more moisture than the peel. Also, at correspond- ing ages of the fruits, moisture content values are statistically higher @lO.OS) for Table 2 than Table 1 for both crops. This could mean that fruit bunches harvested from the plants at maturity (90 days of bunch emergence) ripen faster with more

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Tab

le

2. P

roxi

mat

e co

mpu

sitio

n of

the

fru

its

of M

USU

pura

disi

uca

and

Mu

ss s

apie

ntut

n at

var

ious

st

ages

of

mat

urat

ion

(g p

er

100

g ho

mog

eniz

ed

pulp

) fo

r fr

uits

pl

ant

at d

ay 9

0 __

_ ~~

_~

._

Sam

ple

Day

s af

ter

bunc

h em

erge

nce

Moi

stur

e

Pulp

Pe

el

Cru

de

fibre

C

rude

pr

otei

n (K

jeld

ahl

N x

6.

25)

Silic

a-

Cru

de

free

as

h lip

id

siig

ar>

Star

ch

Ener

gy

cont

ent

(kca

l pe

r 10

0 g)

harv

este

d fr

om

Nitr

ogen

-fre

e ex

tract

ives

__

Ban

ana

90

56.3

57

.6

1.8

3.1

+_ 0.

4 1.

7 +_

0.6

I.1

1.8

33.0

16

5.5

? 4.

2 92

56

.9

57.2

1.

9 3.

3 f

0.7

1.9

+ 0.

7 1.

3 2.

6 31

.4

163.

7 *

6.1

94

57.4

56

.4

2.2

3.8

+ 0.

6 2.

1 f

0.3

1.6

7.3

23.8

16

1.2

+ 5.

3 96

59

.5

55.6

2.

5 3.

8 f

0.5

1.8

+ 0.

2 I .

4 12

.4

17.5

15

1.8

f 5.

9

98

61.2

53

.7

3.1

3.9

+ 0.

5 1.

5 +

0.5

1.2

17.1

11

.5

142.

8 f

4.6

20.2

6.

9 13

3.6

5.1

100

62.5

56

.9

3.8

4.0

f 0.

3 1.

3 *

0.1

0.8

+ 10

2 64

.8

58.5

3.

9 4.

3 f

0.6

0.9

+ 0.

6 0.

6 21

.8

2.8

124.

6 f

2.7

104

65.2

60

.1

4.1

4.9

+ 0.

7 0.

7 T!

I 0.2

0.5

22.3

1.

8 12

2.5

+_ 1.

4

Plan

tain

90

48

.4

49.2

3.

0 2.

9 f

0.6

2.6

+ 0.

1 0.

8 0.

7 40

.1

188.

0 +

6.7

92

46.2

47

.7

3-2

30+0

2 35

io.3

o-

9 2.

8 39

.5

i 96.

9 i

2.4

94

45.1

48

.3

3.6

3.3

f 0.

4 2.

4 f

0.4

I.1

4.3

38.9

20

1.1

+ 3.

6 96

49

.4

48.6

3.

3 3.

4 +

0.8

2.3

f 0.

8 1.

3 8.

9 29

.8

186.

5 f

5.1

98

52.7

49

.4

3.0

3.8

+ 0.

5 2.

1 ?I

0.2

1.

1 IO

.7

24.9

17

4.3

+ 4.

4 10

0 55

.1

51.0

2.

8 3.

9 +

0.3

2.2

_+ 0.

4 1.

0 12

.3

21.3

16

4.6

+_ 4.

8 10

2 58

.9

52.3

2.

7 4.

1 f

0.3

I .9

f 0.

6 0.

8 15

.2

15.9

15

0.0

?z 3

.1

104

59.7

53

.6

2.5

4.4

+ 0.

8 1.

8 +

0.5

0.9

16.6

13

.8

148.

5 +

2.8

106

60.5

54

.1

2.3

4.5

f 0.

7 2.

0 *

0.1

1.1

17.1

11

.8

146.

3 f

1.6

108

60.4

55

.3

2.9

4.8

I!Z 0

.2

2.0

f 0.

3 0.

9 18

.8

9.5

143.

3 +

2.2

110

60.9

56

.4

2.8

4.6

+_ 0.

5 I .

9 +

0.4

1.0

19.2

8.

4 14

2.6

+ 1.

5 ~~

___~

~~

~_~_

____

~~~

Fact

-, va

lue

1s th

e cl

ean

of d

uplic

ate

anal

ysis

pe

r liu

it

fing

er

fill-

eac

h ~,

!’ th

e th

ree

hunc

he\

+ st

anda

rd

devi

atio

n.

whe

re

indi

cate

d O

ther

m

ean?

ha

ve

stan

dard

de

viat

ions

4)

8.

35.8

+ 1

.2

5 34

.7 +

0.8

B

2

32.9

+ 1

.0

c.

31.0

f

1.5

;

29.1

+ 0

.9

27.6

+ 0

.6

2 s 25

.5 f

0.

3 ,$

24

6 +

0.7

“3.

%

42.3

f

0.9

4 44

.2 +

1.

i g

44.5

f

0.6

g 40

.3 f

0.

4 g

37.3

+ 0

.8

% E

35.0

?I 0

.6

5 31

.6 f

0.

3 30

.7 +

0.5

29

.6 f

0.

2 29

.0 f

0.

3 28

.8 L

0.4

__

_-_

water in their pulp and peel. The rate of physlo- logical activity, presumably respiration, has been known to be higher for harvested fruits than those still on the plants (Awan & Ndubizu. 1978) which could explain the greater increases in the moisture contents of harvested fruits. Awan & Ndubizu ( 1978) also reported that moisture content of har- vested plantain increased from 49.42% at harvest to 57.52’14, after 14 days of storage, which is in agreement with results in Table 2.

There was a very gradual increase of the protein levels in the fruits in the plants (banana and plan- tain) throughout the experimental time and for the same ages, there was slightly more protein in the plantain than the banana. Protein levels also increased with time in harvested fruits and their values were consistently higher than for fruits which remained on the plants (t-tests, 11lO~Ol).

The sugar content of the banana pulp increased gradually up to maximum maturation (92nd day) before increasing sharply at onset of ripening and continued these marked increases through the rest of the experimental period. The plantain displayed a similar pattern for its sugar content, even though the banana contained far more sugar QJ lO.05) than the plantain. The harvested fruits contained more sugar at identical ages than the fruits on the plants. Breakdown (hydrolysis) of starch to sugar appears, therefore. to be faster in harvested fruits

than in fruits on the plants. Awan & l\duhi/u ( 1978) observed up to 625% increa\c.\ III su~iir J content of plantain 2 weeks after harvesting.

As expected, there is a corresponding decrease in the starch levels with time as ripening pro-. gressed starch is being hydrolysed LJ sugar. The plantain consistently had more starch than banana and the rate of breakdown of banana starch was higher than for plantain starch. Statis- tically the rate of breakdown of starch MXS higher (pSO.05) for harvested fruits than for fruits which remained on the plants.

For the fruits which remained on the plants, the energy values increased gradually and reached their maximum at maximum maturity before de- creasing equally gradually. Energy values were consistently higher for the plantain than the ba- nana (f-test. p = 0.01). It thus appears that the energy values of the banana and plantain fruits de- crease with the degree of ripening. At similar ages of fruits the energy values were higher for fruits on the plants than for harvested fruits (p<O.O5).

Awan & Ndubizu ( 1978) reported that mature plantain contain 0.96% crude fibre which re- mained constant in the first week of storage only to rise to I .4’%, at the end of the 14 days’ storage. Our crude fibre values (Tables I and 2) are some- what higher and do not show any clear-cut trend of increases or decreases with age of fruit.

Day after bunch

emergence Ca

Ban Plan

60 0.5 0.8 70 0.7 l-5 X0 0.8 1.X 90 0.9 2.4 92 1.4 2.9 94 l-7 3.3 96 2.3 4.2 9X 2.5 3.9

100 3.1 4.4 102 2.7 4.7 104 2.9 4.5 I 06 4.0 I08 3-7 II0 3-2 II2 3.5 II4 3.0 116 3.4

for fruits ripened on the plant

g per kg of dry flour

Mg Fe K Na P

Ban Plan Ban Plan Ban Plan Ban Plan Ban Plan

Table 3. Mineral composition of plantain and banana fruits at different stages of maturation (based on fruit ash produced at 500°C

mg per kg dry flour

I.3 2.6 0.3 0.7 5.5 12.6 0.6 I.4 I.0 0.4 1.9 3.2 O-5 0.9 6.9 13.8 0.9 2.0 I.7 0.9 2.1 3.9 0.7 I.1 7-4 15.1 I.1 2.0 2.2 I.2 2.6 4.2 0.X 1.4 X.4 16.6 1.3 3.1 2.6 I.8 3,3 4.6 I.3 2-7 IO.1 IX-3 I.8 3.8 3-l 2.5 3.8 5.3 2.7 3.9 I I.7 20.4 I.7 4.4 37 2.4 3.5 5.7 2-l 5.3 IO.9 21.7 2.3 4-9 3.5 2.2 4.2 6.4 I.9 8.4 Il.5 21 2 2.5 4.5 4.2 3.7 4.9 6-7 I.7 7.3 13-z 19.7 2.2 4.1 4.9 3-X 4.3 6.5 I.8 9.5 14.6 19.3 2.8 3.7 5.6 4.5 3.6 6.6 I.9 IO.1 15.x 18.4 32 3.3 6.1 4.7

6.5 10.2 20.5 3-5 4-l 6.7 9.7 18.0 2-6 4.9 6.7 9.9 18.3 77 __ 5.3 6.8 IO.5 IX.7 2.5 4-8 6.5 9.X 19.1 2.0 4.7 6.7 IO.3 IX.6 l-7 4.3

Each value is the mean of duplicate determinations per finger per each of the three bunches Plan = plantain. Ban = banana.

Mn Zn c‘u

Ban Plan Ban Plan Ban Plan

3.X 6.6 4-4 10.X I 6 I 7 4.4 7-3 s I 12.4 1-X 2.4 4.7 x-5 5.9 I33 2.5 3.X 5.2 9.6 6 7 14.1 3 I -12 67 II.2 71 I57 ‘9 4-9 7 3 IO.5 6.9 I6 2 :6 57 77 IO.1 7X 161 -1.1 63 X-3 9.x X5 Ii4 j .9 59 8.6 95 X-7 IX.2 17 6-X 9.2 x.7 9-2 18 9 5 1 7-4

IO.3 9 I IO.3 20 3 - 3 - 3 9-J x.3 21 3 X.9 x-4 21.0 IO I x.0 22 6 II 4 77 23’ I I-X 7.0 24 5 11-3 6’5 35 -. 7 I3 5

Table 3 presents results of the mineral composi- tion of these fruits and how mineral levels changed with age of fruit while on the plant. The results of a similar work with the plantain had earlier been reported (Offem & Njoku. 1992~~) using plantains from plants grown on a soil with chemically different composition from our present soil. Values reported in the present study are sta- tistically much lower that those in that report. The influence of soil composition on mineral accumu- lation in plant fruits must be at work here (Njoku, 1992). It is interesting to note here, however, that mineral levels for virtually all the elements studied were statistically higher in the plantain fruits than the banana fruits. An earlier study (Edet, 1988) has reported the mineral composition of both soils ~~ Odukpani (banana plantation) and Idundu

(plantain plantation) ~~~ and shows that. in terms of mineral composition, these two soils are not very different and. therefore, should not be the fac- tor influencing the higher mineral contents in the plantain than the banana. Also, it is known that the two plants are morphologically very similar. Therefore, only further work can lead to a reason- able explanation of these marked differences in the mineral profiles of their fruits.

In conclusion, we would suggest that farmers be vigilant at their plantations to notice that day bunch emergence is just sighted. Thereafter, they should count 90 + 6 days before harvesting a bunch depending on whether fruits are to be used ripe or unripe. Since the results show that fruits harvested at day 90 did ripen faster than fruits which remained in the plant, fruits to be used when ripe should be harvested on day 90 and those to be used when unripe could be harvested as from day 84 or even allowed on the bunch till just required up to day 96.

REFERENCES

AOAC (1984). Qficiul Methods of’ Analysis, 14th edn. Associ- ation of Official Analytical Chemists, Washington, DC.

Askara, A. (1973). The importance of amino acids in fruits: Behaviour of amino acids during ripening of bananas. Gor- dim, 73, 12 16.

Awan, J. A. & Ndubizu, T. 0. C. (1978). Some aspects of nutri- ent changes in stored plantain fruits. Paradisiaq 3, l&24.

Bligh. E. G. & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Can. J. Biochm. Phvsiol.. 37, 91 I- 17.

Bogert, L. J., Briggs. G. M. & Calloway, D. H. (1973). Nutri- tion und Physical Fitness, 9th edn. W. B. Co., Philadelphia.

Dubois, M.. Gitle. K. A., Hamilton, P. A., Rebers. A. & Smith, F. (1956). C’olourimetric method for determination

of sugars and related substances. .Iflri/ t”l?c,mi,~r!?. 28, 350 6.

Edet. 0. S. 0.. OtTem, J. 0. & Nya. A. E. ( 1987). Simple. rapid and sensitive titrimetric determination of carbonate-carbon in soils and plant materials. IV@ J Soil Sci.. 17. 119-37.

Edet. 0. S. 0. (198X). Bio-inorganic characterization of two Iota: plants and their proposed uses PhD thesis. I Jniver- sit): :,f Calabar. Calabar. Nigeria.

Gaman. P. M. & Sherrington. K. B. ( i9Xi J Thr Scirtm o/ fkul: .-In Ittttvduction to Food Sciettw .butriticm md Lfic~rohio/og>~. 2nd edn. Maxwell Macmillan International

editions. Pergamon Press, Oxford, New York. Tokvo, pp. 139 46.

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(Received 30 September 1992; accepted 7 December 1992)