J Sci Food Agric 1997, 75, 244È250 Textural Changes of Banana and Plantain Pulp during Ripening Silas T A R Kajuna,1 Walter K Bilanski2 and Gauri S Mittal2* 1 Department of Agricultural Engineering, Sokoine University of Agriculture, PO Box 3003, Morogoro, Tanzania 2 School of Engineering, University of Guelph, Guelph, Ontario, Canada, N1G 2W1 (Received 30 April 1996 ; revised version received 18 February 1997 ; accepted 14 March 1997) Abstract : Green banana and plantain fruits were treated with ethylene or kept untreated, then stored in environmental chambers at 13, 16, 20 and 25¡C for 8 days. On daily basis, cylindrical samples of the fruits were compressed twice at 50 mm min~1 to 75% of the original height. Changes in the textural properties were estimated by the texture proüle analysis (TPA) technique, involving such parameters as hardness, chewiness, guminess, cohesiveness, springiness. Storage time signiücantly reduced all TPA parameters except cohesiveness. Untreated bananas were harder than untreated plantains at all stages of storage. In treated fruits, however, the trend was reversed, and bananas softened more than plantains. Generally, treated fruits resulted in reduced TPA parameters as compared to untreated fruits. Untreated fruits of both varieties had a good correlation between pH and hardness-1 while treated fruits did not show any correlation between the two properties. J Sci Food Agric 75, 244–250 (1997) No. of Figures : 3. No. of Tables : 6. No. of References : 11 Key words : banana, plantain, texture, ripening, ageing treated with caution and such a modulus is termed apparent modulus of elasticity or modulus of deformability (Mohsenin and Mittal 1977). The latter modulus considers both recoverable and non-recoverable deformations that take place when a food sample is subjected to even very small strains. The actual modulus of elasticity may be obtained by cyclic loading within the elastic limit, and taking the slope of the ürst unloading curve. The apparent modulus of elasticity was measured (Ramaswamy and Tung 1989) by compression tests on ripening banana. The modulus of elasticity has been used by some researchers to represent the ürmness of fruits (Finney et al 1967). The textural aspects of plantain have received little attention in the literature, and the available data based on objective measurements can hardly be sufficient for providing optimum texture for ripeness (Peleg and Brito 1977). Therefore, the objectives of this study were (i) to investigate and compare the textural properties of bananas and plantains as aþected by the ripening process, and (ii) to correlate the INTRODUCTION Texture is a major division of sensory quality in food products. It is limited to the sensation of touch or feel by the human hand and mouth parts. This property may be determined both subjectively and objectively. The objective techniques have the advantage over subjective ones in that they are precisely reproducible. One of the methods that have been employed in analyzing the textural properties of food materials is the texture proüle analysis (TPA). Young’s modulus of elasticity can be obtained as the slope of the compressive stress–strain curve within the linear region. Most agricultural materials are viscoelastic (Mohsenin 1986), exhibiting both ýow and deformation properties. Therefore, the modulus of elasticity obtained for agricultural materials must be * To whom correspondence should be addressed. Contract grant sponsor : International Development Research Centre, Ottawa, Canada. 244 ( 1997 SCI. J Sci Food Agric 0022-5142/97/$17.50. Printed in Great Britain T extural changes of banana and plantain change in hardness with the change in pH during the ripening process. MATERIALS AND METHODS Fruits of two cultivars namely, bananas of the Cavendish sub-group (Musa AAA Group) and plantains, of the plantain sub-group (Musa AAB Group) were acquired in three diþerent shipments from Costa Rica through a fruit dealer (Meloripe Banana Company, Toronto, Canada) between May and July 1993. Each shipment represented a replication for the experiment. When they arrived to Toronto, they looked green and were estimated at stage 1 on the colour ripening chart. The bananas were in cartons of 18·2 kg while plantains were in cartons of 11·4 kg each. The fruits stayed in the warehouse of the dealer for 3 days from receiving date to the delivery date. Twenty cartons of bananas (half of them ethylene treated) and 32 cartons of plantains (half of them treated) were delivered to the University by a truck (1 h drive). The ethylene treated fruits were treated with 1000 ppm ethylene for 24 h in air tight rooms at room temperature (B20¡C). Thus preliminary transportation treatment was same on all the batches used for the research. There was no visible transportation damage to the fruits. Upon arrival at Guelph, the fruits were estimated to be between stages 1 and 2 (dark to medium green) on the standard colour ripening chart (Banana Retail Guide of Del Monte Tropical Fruit Company, USA). All fruits were stored at four diþerent temperatures in 8 separate environmental chambers with the relative humidity controlled at 90 ^ 4%. The variables were ethylene treatment (treated, untreated), cultivar (bananas and plantains), temperature (13, 16, 20 and 25¡C), and storage time (days 1 to 8). Day 1 was considered after storage for 24 h at the desired temperature. The fruits were removed daily from the storage chambers and allowed to equilibrate to ambient temperature (B20¡C) for about 30 min. Cylindrical samples of size 20 mm diameter by 20 mm long were taken from the fruit pulp along the longitudinal axis, using a cork borer. Samples were taken from approximately the same central position of the fruit, and each sample being taken from a diþerent fruit. The TPA test was carried out on a universal testing machine (Model 4024, Instron Canada Ltd, Burlington, Ontario, Canada). Two compressions, each to 75% of the original height of the sample were done at a crosshead speed of 50 mm min~1. Force–time data were collected on a personal computer through IEEE and a BASIC software. The software logged 10 data sets per second. Three samples were taken from each treatment and the whole experiment was replicated three times. Thus, there was a total of 1152 tests involving an equal number of fruits (ie 2 ethylene treated or untreated 245 (gas) ] 2 varieties (var) ] 4 temperature levels (temp) ] 8 days ] 3 samples ] 3 replications (rep)). The pH was determined by inserting the probe of a pH meter (Accumet model 925-Fisher Scientiüc Co, USA) into the pulp of the fruit and recording the pH readings. The following TPA parameters were then calculated (Fig 1). Hardness-1 (H1, N) refers to the ürst peak before the compressive plate reverses direction and hardness-2 (H2, N) is represented by the force at the second peak on the force deformation curve. Cohesiveness (COH) is the strength of the internal bonds making up a food material, and is represented by the ratio of the area under the second curve, (A2) to the area under the ürst curve, (A1). Gumminess (GUM, N) is the force required to disintegrate a semisolid food to a state ready for swallowing, and is a product of hardness-1 and cohesiveness. Springiness (SPGN, cm) is also referred to as elasticity, and is deüned as the rate at which a deformed food material goes back to its undeformed condition after the deforming force is removed. On the TPA curve, it is represented by the distance on the abscissa, from the point where the loading plate touches the food sample during the second bite to the point corresponding to hardness-2. Chewiness (CHEW, N cm) is the energy required to masticate a solid food Fig 1. Typical texture proüle plot for (a) untreated plantain pulp stored at 13¡C for 1 day, and (b) treated banana pulp stored at 16¡C for 2 days. S T A R Kajuna, W K Bilanski, G S Mittal 246 product to a state ready for swallowing, and is product of the hardness-1, cohesiveness and springiness. The apparent modulus of elasticity was also computed as the slope of the ürst compressive stress–strain curve within the linear region. The data were analysed (SAS 1988) using analysis of variance (ANOVA), least square diþerence (LSD) and correlation (CORR) procedures. The general linear model (GLM) procedure of the SAS was used to perform a split-plot analysis. There was one restriction on randomisation as storage days were selected after selecting other treatment parameters—ethylene treatment and storage temperature. Ethylene treatment and storage temperature were randomised. The whole experiment was repeated twice. RESULTS AND DISCUSSION Replication and interaction eþ ects The replication eþect was not signiücant at 1% level for all the TPA parameters, except springiness, at 5% level (Table 1). Most of the three-way interaction eþects were not signiücant except for SPGN (P \ 0·01). Ethylene eþ ect The ethylene treatment to banana and plantain fruits had a signiücant eþect on all the TPA parameters (Table 1). Temperature did not show signiücance on any of the parameters as an individual factor. However, it aþected through interaction with gas and replication. This therefore suggests that the eþect of temperature on the hardness or texture of banana and plantain fruits during storage depended on whether fruits were treated or not. At the end of the 8-day storage period, treated bananas at the temperature of 25¡C had started to rot while those at 13¡C were still hard and ürm, with a large blend of green colour with yellow (ie more green than yellow). Since each replication represented a different batch of the fruits, there could possibly be some diþerences in maturity from batch to batch. This could perhaps inýuence the way the fruit responds to ethylene at diþerent temperatures. Associated with the batch to batch variation is perhaps the time the fruits were harvested or the time period taken for the fruits to be transported from the source (farms) to the market. The data showed a trend for the temperature inýuence on the hardness, with fruits becoming softer at higher temperatures than lower temperatures. However, this trend was greatly aþected by ethylene treatment. There was a more uniform texture of the fruit pulp (for both bananas and plantains) in treated fruits than in untreated fruits. Therefore, ethylene treatment would be encouraged where uniform texture of the fruits is the marketing strategy. In climacteric fruits, the greater the concentration of ethylene the faster the stimulation of respiration (Pantastico 1975). However it is more eþective when applied during the pre-climacteric stage. The application of ethylene signiücantly aþects the time scale required to reach the climacteric peak. In climacteric fruits like bananas, ethylene acts only to shift the time axis, it does not alter the shape of the respiratory curve. TABLE 1 Split-plot ANOVA showing the mean sum of squares (MS) for TPA parametersa,b Source df H1 H2 (]10~5) COH GUM SPGN (]10~2) CHEW Modulus 6 2324** 17 31 65 6140** 45 22 1·4* 38·3** 0·4 0·2 19·1 981·0** 6·6 4·0 4·3 277·3** 1·9 0·5 Test of the hypothesis using var ] day ] gas ] temp as error term Var 1 5330 42142** 942** Day 7 49381** 16667** 4 Var ] day 7 9526** 1592** 16** Var ] gas 1 47304** 74719** 1647** Var ] temp 3 1542 941 12* Gas ] day 7 2321 1313 16** Temp ] day 21 1171 557 4 Var ] temp ] day 21 510 210 2 Var ] gas ] temp 3 1927 792 9 Gas ] temp ] day 21 1320 637 5 Var ] gas ] day 7 2079 379 3 633** 101** 5 909** 11 14* 5 2 9 6 1 42·4** 0·5* 0·3 16·8** 0·6* 0·1 0·1 0·1 0·3 0·1 0·6* 62·9** 15·5** 1·6 115·3** 2·4 3·7* 0·8 0·3 2·2 0·9 0·5 11·2** 6·5** 0·9* 20·9** 0·2 0·4 0·1 0·1 0·2 0·1 0·3 Test of hypothesis using rep ] gas ] temp as error term Rep 2 36209 11752 Gas 1 1787802** 867385** Temp 3 11660 6030 Gas ] temp 3 3118 2017 a Abbreviations : df, degree of freedom ; rep, replication ; temp, storage temperature ; gas, ethylene treated or untreated. b Level of signiücance : * P \ 0·05, ** P \ 0·01. T extural changes of banana and plantain 247 H1 had a mean of 191 N for bananas while it was 161 N for plantains (Table 2). On the contrary, in treated fruits, plantains had H1 of 47 N while that of bananas was 32 N. Thus, for the ürst bite, untreated bananas would require more energy than untreated plantains. After ethylene treatment, however, plantains would require more energy than bananas, signifying that bananas soften more with ethylene treatment than plantains. For the second bite (H2), Table 2 shows a trend similar to that of H1, except that lower energy would be spent in biting the food sample. As reported elsewhere (Pitt 1992) the major modes of failure in fruit and vegetable tissues are cell rupture and cell debonding, therefore untreated plantain pulp would suþer more cell rupture and cell de-bonding on the ürst and second bites than untreated banana pulp. But once ethylene is applied, the energy requirement would be reversed. Cohesiveness, which is a measure of the strength of the internal bonds of the food material was signiücantly higher for untreated bananas than for untreated plantains (Table 2), also supporting the argument above, that more energy would be required for de-bonding the Ethylene treatment also interacted with the variety (Table 1) to cause a signiücant eþect on all the TPA parameters. It also interacted with storage time to cause a signiücant eþect on COH, GUM and CHEW. The mean values for the response of the TPA parameters for the var ] gas interactions are shown in Tables 2 and 3. For untreated fruits, the response variables H1, H2, COH, GUM, CHEW and modulus of elasticity (modulus) were consistently higher for bananas than plantains, except the springiness (SPGN) which was higher (except for day 2 and 4) in untreated plantains than untreated bananas. For treated fruits, these variables (including SPGN) were consistently higher in plantains than in bananas ; further underlining the eþect of interaction between gas and variety. Ethylene had a greater softening eþect on banana than plantain. Variety eþect Hardness-1 was not inýuenced by variety, but was inýuenced by the interaction between variety and ethylene treatment (var ] gas). However, all other TPA parameters were inýuenced by the variety and var ] gas interaction (Table 1). For untreated fruits, TABLE 2 Comparison of pulp’s textural parameters between treated and untreated bananas and plantains [var ] gas]a Untreated H1 (N) H2 (N) COH GUM (N) CHEW (N cm) Modulus (MPa) Ethylene treated Bananas Plantains Bananas Plantains 191 ^ 41 142 ^ 33 0·062 ^ 0·011 12·2 ^ 3·8 4·6 ^ 1·6 2·6 ^ 0·5 161 ^ 92 94 ^ 54 0·039 ^ 0·006 6·6 ^ 4·2 2·7 ^ 1·8 1·7 ^ 1·0 32 ^ 32 20 ^ 22 0·034 ^ 0·005 1·2 ^ 1·1 0·3 ^ 0·4 0·4 ^ 0·4 47 ^ 45 27 ^ 25 0·037 ^ 0·004 1·7 ^ 1·6 0·6 ^ 0·5 0·5 ^ 0·5 a The data are the averages of 96 observations ^ SD. TABLE 3 Comparison of springiness (SPGN, cm) in treated and untreated bananas and plantains at diþerent storage times [var ] gas ] day]a Days Bananas Plantains Untreated 1 2 3 4 5 6 7 8 Treated Untreated Treated Mean SD Mean SD Mean SD Mean SD 0·358 0·410 0·375 0·396 0·364 0·367 0·355 0·355 0·019 0·056 0·027 0·069 0·036 0·054 0·053 0·032 0·286 0·283 0·285 0·272 0·258 0·246 0·246 0·263 0·006 0·037 0·017 0·032 0·016 0·024 0·034 0·039 0·436 0·394 0·416 0·393 0·379 0·370 0·381 0·407 0·020 0·050 0·041 0·048 0·036 0·048 0·048 0·047 0·366 0·366 0·365 0·388 0·367 0·390 0·382 0·381 0·053 0·048 0·049 0·045 0·039 0·033 0·032 0·033 a The data are the averages of 12 observations. S T A R Kajuna, W K Bilanski, G S Mittal 248 pulp of untreated bananas than that of untreated plantains. Similarly, gumminess which is a measure of the force to disintegrate the particles ready for swallowing was also higher for untreated bananas that it was for untreated plantains (Table 2). The eþect was reversed when the fruits were treated. Springiness, which is a measure of the recovery in height after the sample has been compressed by the teeth during mastication, was higher in both untreated and treated plantains than in untreated and treated bananas (Table 3). This suggests that although untreated bananas may require more mastication energy in the mouth for the ürst and second bites than untreated plantains, they may not spring back as much as plantains. There was a var ] temp interaction eþect on springiness of the pulp (Tables 1 and 4) which showed that at each temperature, springiness was higher for plantains than it was for bananas. Chewiness, which is the energy for masticating the food product until it is ready for swallowing, was higher in untreated bananas than in untreated plantains (Table 2) and the trend was again reversed for treated pulp. This further supports the earlier observations for H1, H2 and GUM. The elastic modulus which is a measure of ürmness (Finney et al 1967) was higher in untreated banana than in untreated plantain with the trend being reversed in treated fruits (Table 2). The pulp rupture force in three untreated cultivars of plantains and one untreated cultivar of Cavendish bananas at 20¡C was compared (Marriott et al 1981). They reported that rupture force for unripe banana pulp was higher (25·5 N) than the rupture force in the pulp of two of the three plantain cultivars (23·1 and 25·0 N). Only one plantain cultivar showed a higher pulp rupture force (27·5 N). However, once ripening commenced, the rupture force in plantains was always higher than that of bananas. This supports the results of this study that untreated banana pulp had a harder texture than that of untreated plantains. Storage time or ripening eþect The storage or ripening time (days) had a signiücant eþect on all the TPA parameters except cohesiveness. It also interacted with variety to aþect all the TPA parameters except gumminess and chewiness (Tables 1 and 5). There was also a gas ] day interaction eþect on cohesiveness, gumminess and chewiness (Tables 1 and 6). As well, there was a three-way interaction eþect (var ] gas ] day) on springiness (Tables 1 and 3). On day 1, plantains started with higher H1 and H2 than TABLE 4 Comparison of cohesiveness (COH) and springiness (SPGN) for various temperatures for bananas and plantains [var ] temp interaction]a Variety Temperature level (¡C) 13 Banana Plantain 16 20 25 COH SPGN (cm) COH SPGN (cm) COH SPGN (cm) COH SPGN (cm) 0·049 ^ 0·017 0·038 ^ 0·006 0·33 ^ 0·06 0·38 ^ 0·04 0·050 ^ 0·019 0·038 ^ 0·005 0·33 ^ 0·07 0·38 ^ 0·04 0·047 ^ 0·016 0·038 ^ 0·005 0·32 ^ 0·08 0·39 ^ 0·05 0·045 ^ 0·015 0·038 ^ 0·005 0·30 ^ 0·06 0·39 ^ 0·05 a The data are the averages (^SD) of 48 observations including ethylene treated and untreated. TABLE 5 Comparison of textural parameters between bananas and plantains at diþerent storage times [var ] day interaction]a Storage day 1 2 3 4 5 6 7 8 Bananas Plantains H1 (N) H2 (N) COH Modulus (MPa) H1 (N) H2 (N) COH Modulus (MPa) 151 ^ 73 122 ^ 86 113 ^ 91 112 ^ 85 104 ^ 90 97 ^ 89 99 ^ 93 95 ^ 90 108 ^ 59 91 ^ 69 83 ^ 71 83 ^ 67 75 ^ 69 69 ^ 67 71 ^ 70 67 ^ 67 0·051 ^ 0·020 0·051 ^ 0·018 0·049 ^ 0·019 0·050 ^ 0·017 0·046 ^ 0·016 0·045 ^ 0·015 0·046 ^ 0·016 0·046 ^ 0·015 1·97 ^ 0·87 1·62 ^ 1·16 1·52 ^ 1·24 1·48 ^ 1·17 1·40 ^ 1·27 1·29 ^ 1·25 1·29 ^ 1·26 1·23 ^ 1·24 203 ^ 78 135 ^ 95 111 ^ 94 85 ^ 81 87 ^ 87 69 ^ 71 71 ^ 78 72 ^ 76 109 ^ 45 80 ^ 58 66 ^ 58 49 ^ 48 52 ^ 52 41 ^ 44 42 ^ 46 42 ^ 43 0·036 ^ 0·006 0·037 ^ 0·006 0·038 ^ 0·007 0·037 ^ 0·004 0·039 ^ 0·004 0·037 ^ 0·004 0·039 ^ 0·003 0·039 ^ 0·004 2·20 ^ 0·84 1·49 ^ 0·98 1·23 ^ 1·05 0·95 ^ 0·94 0·92 ^ 0·93 0·74 ^ 0·82 0·77 ^ 0·86 0·78 ^ 0·86 a The data are the averages (^SD) of 24 observations including ethylene treated and untreated. T extural changes of banana and plantain 249 TABLE 6 Comparison of the cohesiveness (COH), gumminess (GUM) and chewiness (CHEW) between treated and untreated pulp at diþerent storage times [gas ] day interaction]a Untreated 1 2 3 4 5 6 7 8 Ethylene treated COH GUM (N) CHEW (N cm) COH GUM (N) CHEW (N cm) 0·054 ^ 0·018 0·054 ^ 0·016 0·053 ^ 0·015 0·051 ^ 0·016 0·050 ^ 0·012 0·047 ^ 0·013 0·049 ^ 0·013 0·048 ^ 0·013 12·8 ^ 4·1 11·1 ^ 4·1 10·5 ^ 4·4 9·0 ^ 4·9 8·8 ^ 4·7 7·4 ^ 4·7 8·1 ^ 5·3 7·6 ^ 4·8 4·99 ^ 1·43 4·57 ^ 1·95 4·16 ^ 1·73 3·59 ^ 2·06 3·28 ^ 1·79 2·84 ^ 1·92 2·98 ^ 1·97 2·90 ^ 1·80 0·033 ^ 0·005 0·034 ^ 0·004 0·034 ^ 0·004 0·037 ^ 0·006 0·036 ^ 0·005 0·035 ^ 0·004 0·036 ^ 0·005 0·036 ^ 0·005 3·9 ^ 2·1 1·9 ^ 1·7 1·0 ^ 0·6 1·2 ^ 1·3 0·9 ^ 0·5 0·8 ^ 0·3 0·8 ^ 0·3 0·8 ^ 0·3 1·29 ^ 0·71 0·63 ^ 0·57 0·35 ^ 0·21 0·41 ^ 0·36 0·29 ^ 0·17 0·26 ^ 0·15 0·25 ^ 0·14 0·26 ^ 0·15 a The data are the averages (^SD) of 24 observations. bananas (Table 5) but softened faster than bananas to end up with lower H1 and H2 than bananas. The LSD test (SAS 1988) showed (data not given) that H1 for all fruits decreased signiücantly for the ürst 4 days in storage from 177 to 98 N. After that there was a gradual non-signiücant decrease in H1 to the value of 83 N on day 8. For bananas, it decreased from 151 N on day 1 to 95 N on day 8, while for plantains, it decreased from 203 N on day 1 to 72 N on day 8 (Table 5). This suggests that for bananas and plantains in storage, there is a faster rate of decrease in ürmness in the ürst 4 days than in the subsequent storage period. Thus, any marketing strategy would have to aim at disposing of the bananas and plantains within that period to avoid the possible loss. Since the softening of the banana and plantain fruits is accompanied by the hydrolysis of starch to sugars by the amylases and phosphorylases (Agravante et al 1990), there is less and less substrate remaining to be acted on in the last days of storage, perhaps a reason why the decrease in hardness was less signiücant. Agravante et al (1990) also observed that in bananas, there was a rapid increase in the total sugars at the initial stages of ripening when the peel started to turn yellow, and slowed down at the later stages. This agrees with the observation in this study, of the rapid decrease in H1 in early days of the storage of treated plantains, and a slower decrease in the later storage days. The eþect of storage time on H2 followed a trend similar to that of H1 (Table 2). Storage time as a factor, had no signiücant eþect (P [ 0·05) on cohesiveness, but a signiücant eþect was observed through interaction. Gumminess decreased signiücantly from 8·4 N on day 1 to 5·1 N on day 4 for all the fruits. From there on, the decrease was nonsigniücant until the last day when it was about 4·0 N (data not shown). But considering the interaction eþects, Table 6 shows that untreated fruits started oþ with higher gumminess of 12·8 N (about 4 times) than treated fruits (3·9 N) after day 1. Similar eþect was observed for cohesiveness and chewiness. After 8-days storage time, untreated fruits ended up with about 10 times higher gumminess (7·6 N) than treated fruits (0·8 N). From the three-way interaction of var ] gas ] day (Table 3) it can be seen that treated fruits had less springiness than untreated fruits. Plantains had generally higher springiness than bananas, and the LSD test showed that springiness was higher in the ürst 4 days than in the remaining 4 days, but there was no signiücant diþerence between the ürst 4 days and the last 4 days of storage. Modulus of elasticity The modulus of elasticity decreased with storage time for both treated and untreated fruits (Table 5). This observation matches that of Finney et al (1967) who reported that during ripening of bananas, there is a decrease in starch content of the pulp which was also correlated to the elastic modulus of the fruit. Hydrolysis of starch to sugar during ripening causes an increase in osmotic pressure in the banana pulp. The increase in the osmotic pressure is usually associated with a decrease in turgor pressure which may account for softening during ripening, and would cause the elastic modulus to decrease (Finney et al 1967). A similar trend of decrease in the modulus of elasticity with ripeness has been reported in blueberries (Bower and Rohrbach 1976). Correlation of H1 with pH Plantain pulp was more acidic than banana pulp, and in both varieties, the acidity increased with storage time. As seen in Fig 2, there was a linear trend, between H1 and pH. Regression analysis showed a low (0·36) coefficient of determination, indicating that there may not be a strong linear relationship between H1 and pH 250 S T A R Kajuna, W K Bilanski, G S Mittal samples remained on the higher end of the scale. Like in bananas, the scatter in treated plantains did not show any strong relationship between pH and H1. CONCLUSIONS Fig 2. Correlation between pH and hardness 1 (H1) in untreated bananas. Y \ 4·96 ] 0·003X. R2 \ 0·36. Each point is a mean of 3 observations. in untreated bananas. However, there was a distinct pattern showing that higher values of H1 tended to occur with higher values of pH. This implies that when the fruits were harder, they were less acidic and became more acidic as they softened. Also untreated fruits tended to have higher pH (less acidic) throughout the storage period, which reýects higher H1 values. In treated bananas, there was no deünite relationship between pH and H1. However, it will be seen, contrary to the results in Fig 2, that most of the samples tested had a mean value on the lower end of the H1 scale, which supports the softening of the pulp due to ethylene treatment. Plantains showed a stronger linear relationship between pH and H1 (Fig 3). The scatter was more uniformly distributed over the entire range of the H1 scale as compared to what was observed in untreated bananas. Thus, plantains softened faster than bananas. In fact it will be seen, comparing Figs 2 and 3 that towards the end of storage time, a reasonably good number of samples had shifted towards the lower end of the H1 scale in plantains while for bananas, more Fig 3. Correlation between pH and hardness 1 (H1) in untreated plantains during storage. Y \ 4·61 ] 0·004X. R2 \ 0·73. Each point is a mean of 3 observations. Storage time signiücantly reduced all TPA parameters except cohesiveness. Based on these parameters, except springiness, untreated bananas were harder than untreated plantains at all stages of storage. In treated fruits, the trend was reversed, and bananas softened more than plantains. Ethylene treatment resulted in reduced TPA parameters as compared to untreated fruits. 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