Scientific classification of ripening period and development of

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SCIENTIFIC CLASSIFICATION OF RIPENING PERIOD AND DEVELOPMENT OF COLOUR GRADE CHART FOR INDIAN MANGOES (MANGIFERA INDICA L.) USING MULTIVARIATE CLUSTER ANALYSIS

Amirtha Ganesh P

Anantharaman G

Madan B Tarun Kumar S

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ABSTRACT Ripening period of mangoes into different stages To develop a colour grade chart for Indian Mangoes The Physio-chemical, Internal and External colour values

and textual characteristics were measured throughout the ripening period of two varieties. Alphonso Banganapalli

PCA along with Hierarchical clustering method were used and the ripening period of mango fruits was classified into five stages. Unripe early ripe partially ripe ripe over ripe

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ABSTRACT A colour grade sheet was developed based on these

stages along with the physico-chemical, textural and color values of both varities.

The developed colour chart can be used as a useful rapid, non-destructive grading tool at mango pack houses and processing industries.

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INTRODUCTION Mango is an important tropical fruit having a worldwide

demand, India ranking first in production with 54.2% contribution producing 14-16 million tonne yearly.

The Indian varities, known for its strong aroma, intense peel coloration, delicious taste and high nutritious value, are Alphonso Kesar Totapuri Banganapalli Dussehari Neelum

Mangoes, being climacteric fruits, their ripening process takes place immediately after harvest.

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INTRODUCTION Mango pack houses require an easy

nondestructive tool to grade the fruits based on ripening before packaging. The pulping industry needs it to select the fruits at an optimum ripening stage to get desired pulp characteristics.

The colour grade chart would fulfil the above purposes, but at the same time it should contain information about the quality parameters like physico-chemical properties and textural properties

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INTRODUCTION These kind of colour charts were

developed purely based on the external appearance, the internal changes were not considered and moreover scientific way of classification had not been employed.

Hence the study was carried out with the objective of classifying the ripening period into different stages and develop a colour grade chart for Alphonso and Banganapalli mangoes.

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MATERIALS AND METHODS Mangoes were treated with ethylene for

24 h and allowed for ripening. The quality factors viz. TSS, external & internal colour values, titrable acidity and textural parameters were measured throughout the ripening period.

These measured parameters were analysed for its significance and PCA was used to predict the total variability. Then the ripening period was classified into five stages with hierarchal clustering method.

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EXPERIMENTATION1. Mango sample collection and

preparation2. Physicochemical properties3. Textural and colour measurement4. Statistical analysis

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MANGO SAMPLE COLLECTION AND PREPARATION

Raw Alphonso and Banganapalli mangoes were collected from two different locations viz. Krishnagiri at 20 days intervals.

The mangoes after washing and shade drying for 30 min were treated with ethylene at 200 ppm for 24 h at 20◦ C with 85 percent Relative Humidity in the ripening chamber.

After the treatment, the chamber was opened to exude ethylene and the treated mangoes were kept in the for regular analysis.

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MANGO SAMPLE COLLECTION AND PREPARATION

Two batches of mangoes were made, one set for imaging and another one for physico-chemical analysis.

From the second set, three fruits from each varieties were taken randomly for physiochemical analysis every day.

The experiments were continued till the decay of fruit. The decay stage was decided by visual inspection when 50 percent of available fruits for analysis reached the spoilage.

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PHYSICOCHEMICAL PROPERTIES Homogenized mango pulp was obtained

with laboratory mixer to determine 1. Total Souble Solid (TSS)2. Titrable Acidity.

TSS was measured using a digital refractometer and expressed as ◦Brix .

Titrable Acidity was determined by titration with 0.1 N NaOH and it was expressed as grams citric acid equivalent/100g sample (average considered).

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TEXTURAL AND COLOUR MEASUREMENT

The textural characteristics of the mangoes were measured using the Texture - 4 mm cylindrical probe(P/4) was used with 1 mm s−1 pre-test speed, 0.1 mm s−1 test speed, 1 mm s−1 post-test speed, and 10 mm penetration depth to obtain force displacement curve.

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TEXTURAL AND COLOUR MEASUREMENT

The maximum force required to pierce the peel is called as peel strength(pointB).

The slope between A and B point is called as stiffness of the fruit.

The mean force between C and D point is called as flesh firmness.

Textural values were measured at three points in a mango and the average value was used.

Colour coordinates were recorded both for external and internal surface of the mango using a Hunter LAB colour meter. The internal colour was measured by cutting the fruit into two halves along with the vertical axis.

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STATISTICAL ANALYSIS Initially anova was carried out to check the variability between

zones.

Then all the observed data were analyzed with Pearson correlation to find out the correlation between variables.

Then PCA was carried outto predictthe variability. Since all the observed data were describing variables and no predicting variable was involved, cluster analysis would be more suitable rather than PLS or discriminant analysis.

Kaur and Kaur (2013) reported that hierarchical clustering could be more suitable and efficient than K-means clustering for small dataset and ripening might be explained better by hierarchical clustering.

Hence hierarchical clustering analysis using ward method was carried out in order to group the whole data into 5 stages of ripening.

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RESULTS AND DISCUSSIONS

Ripening process was faster in Alphonso and has researched the decay stage on 19th day and Baganapalli on 23rd day due to physiological variations between two varieties.

The Anova result showed that, the changes in physico-chemical, textural and colour properties between the samples collected from two zones were highly non-significant (P > 0.40) during ripening.

It can be perceived that 75 percent of ripening had reached within 10 days and contributed to the major changes in all quality parameters.

Thus the remaining ripening period did not have significant influence on most of the physic-chemical and textural properties.

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CHANGES IN PHYSICO CHEMICAL PROPERTIES

Changes in total soluble solids and titrable acidity of Alphonso and Banganapalli is shown in the Fig. 2. Total soluble solids(TSS) was linearly increasing up to 9th day from 7.7 ± 0.8 to 19.3 ± 0.1 ◦Brix and 7.5 ± 0.3 to 16.5 ± 0.2 ◦Brix for Alphonso and Banganapalli respectively.

An increase of TSS could mainly be due to hydrolysis of starch into soluble sugars such as sucrose, glucose and. After 9th day, only slight variations were observed in TSS in both the fruit varieties, and Alphonso had a TSS of 21.1 ◦Brix on 19th day and Banganapalli had 15.8 ◦Brix on the 23rd day of ripening.

Unlike TSS, titrable acidity (TA) was decreasing up to 16th day and after that no significant change was observed in case of Alphonso.

At the same time, decreasing trend was observed till decay in Banganapalli.

The rate of change in TA was observed to be higher for Alphonso than Ban ganapalli.

This might be due to physiological variation between varieties. The titrable acidity of raw and fully ripened Alphonso was 0.019 ± 0.003 and 0.003 g/100 g of sample respectively and for Banganapallithe acidity values were 0.007 ± 0.003 and 0.001 g/100 g of sample, respectively.

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CHANGES IN PHYSICO CHEMICAL PROPERTIES

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CHANGES IN INTERNAL AND EXTERNAL COLOUR

During ripening, the external colour of raw mango turned from green to reddish yellow, which increased all hunter colour coordinates(Le *,ae *,be *) during ripening.

This was due to chlorophyll degradation, which subsequently revealed the yellow carotenoid pigments.

The changes in internal and external colour values are shown in Fig. 3 and 4. Le * value increased from 49.21 ± 1.4 to 64.55 ± 0.86 and 51.70 ± 2.15 to 70.51 ± 2.75 for Alphonso and Banganapalli respectively. ae * value increased from −9.8 ± 1.07 to 29.07 ± 0.83 and −10.95 ± 2.35 to 16.45 ± 2.40 while be * increased from 32.46 ± 0.82 to 62.150 ± 1.38 and 27.74 ± 3.95 to 48.81 ± 4.12 for Alphonso and Banganapalli respectively.

Lightness value, Li * for the inner surfaces of mango was decreasing due to the internal colour turning from white to yellow. But both internal ai * and bi * values followed the same trend with the external a* and b* values. Li * value decreased from 76.96 ± 1.48 to 56.38 ± 4.47 and from 91.24 ± 1.67 to 73.28 ± 2.94 forAlphonso and Banganapalli respectively.

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CHANGES IN TEXTURAL CHARACTERISTICS

The typical force displacement curve obtained for the mangoes is shown.

Decreasing trend was found in all the three parameters during ripening in both varieties. Many researchers have reported about reduction in fruit firmness for different fruits.

The reduction in fruit firmness was due to alteration in cell wall structure by degrading enzymes (e.g. polyglacteronase) and also by degradation of starch and breakdown of starch, cellulose and hemicellulose.

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During the first week of ripening, drastic reduction was observed in all the three parametersThe rate of decrease in the peel strength, fruit stiffness and flesh firmness reduced after 8th day. All these changes substantiate that 75 percent of ripening occurs within the 10 days.

The maximum and minimum peel strength of raw and ripened mango were 64.75 ± 3.72 N and 5.79 ± 0.72 N for Alphonso and 70.72 ± 3.21 N and 6.82 ± 1.07 N for Banganapalli respectively.

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The raw fruit had the higher stiffness of 18.56 ± 1.25 N and 14.65 ± 1.547 N and lower stiffness were 1.18 ± 0.03 N and 2.05 ± 0.21 N for Alphonso and Banganapalli respectively.

Significant difference in flesh firmness between varieties were observed initially and the values were 28.63 ± 0.97 N and 22.06 ± 1.12 N for Alphonso and Banganapalli respectively. The final flesh firmness was recorded as 0.87 ± 0.24 N and 0.83 ± 0.13 N for Alphonso and Banganapalli respectively.

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CORRELATION STUDIES BETWEEN QUALITY PARAMETERS The Pearson correlation matrix of quality parameters for

Alphonso and Banganapalli is given in Table 1 and 2. Correlation behavior was found as similar for both varieties.

Le ∗ value had a high positive correlation(r > 0.90) with ae ∗, be * and TSS values and high negative correlation(r > − 0.90) with the textural characteristics.

ae ∗ value had a high positive correlation(r > 0.90) with be *, TSS and internal colour coordinates(ai *,bi *) and high negative correlation(r > −0.90) with Li *, acidity and textural properties.

Except Li * the rest of the colour coordinates had shown positive correlation between each other. From these observations, it could be concluded that colour coordinates and TSS were inversely correlated with textural characteristics and acidity for Alphonso than Banganapalli.

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CORRELATION STUDIES BETWEEN QUALITY PARAMETERS

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PCA AND CLUSTER ANALYSIS

The total variations occurring during the ripening period are explained in the PCA score graph and the variation between the variables are shown in the PCA loading. PC1 represent 92 percent and 95 percent, PC2 represent 5 percent and 2 percent of total variations occurring during ripening of Alphonso and Banganapalli respectively.

From the PCA loading graph, it could be noticed that the peel strength can be explained better by PC1 than PC2 and on the contrary PC2 explains more about the colour values ae *, be *.

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Changes in acidity during ripening had followed the same pattern in both varieties and PC1 is sufficient to explain variation. It was found that the changes in the textural characteristics could be explained more with PC1. But both PC1 and PC2 had an important role to explain the total variation in internal and external colour values since they were dispersed over the PCA plot.

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It was found that principal component and hierarchical cluster analysis were capable of differentiating radish slices to select hurdle technologies. From the cluster analysis the ripening period was grouped into five clusters, encircled and denoted in alphapates .Those five clusters represent five stages viz. unripe, early ripe, partially ripe, ripe, over ripe/decay during ripening.

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The firsttwo stages can be grouped as pre-climacteric phase, the second two stages as climacteric and the last stage as senescence phase. In case of Alphonso,firstfour days were grouped to befirst stage,then5thand 6th days as 2nd stage, then 7th to 11th day as third stage, then 12th to 17th day as fourth stage and finally the 18th & 19th day as fifth stage.

In case of Banganapalli, first six days were grouped as first stage, then 7th and 8th days as 2nd stage, then 9th to 12th day as third stage followed by fourth stage lied between 13th to 18th day and finally 19th to 23rd day as fifth stage.

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Clear differences between clusters were observed (Fig. 6a)inAlphonso and it substantiates the distinct changes in physic-chemical parameters in phased manner during ripening. At the same time no clear demarcation between the stages could be found in Banganapalli(Fig. 7a).

This may be due to the fluctuation in the changes in physico-chemical parameters during ripening. In both varieties,the second stage existed too short stint(only for two days). The decay or over ripen stage existed for a short period for Alphonso and it existed for 5 days for Banganapalli. This may be due to slow ripening and physiological variation between the varieties.

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PCA GRAPHS FOR ALPHONSO MANGOES

A. SCORES GRAPH

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B. LOADING GRAPH,

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C. INFLUENCE GRAPH.

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PCA GRAPHS FOR BANGANAPALLI MANGOES

A. SCORES GRAPH,

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B. LOADING GRAPH,

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C. INFLUENCE GRAPH.

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COLOUR GRADE CHART

The colour grade chart was developed with a comprehensive scientific approach using internal as well as external quality parameters.

The colour grade chart was prepared with five ripening stages and is shown in for Alphonso and Banganapalli based on the five clusters.

These five stages were named as unripe, early ripe, partially ripe, ripe and over ripe or decay and categorized into three phases viz. pre-climacteric, climacteric and senescence.

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COLOUR GRADE CHART

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COLOUR GRADE CHART Images of mangoes of each stage were given in

colour chart along with the corresponding ripening period.

In addition to this information, Internal and external quality parameters for the corresponding ripening stage were given.

This colour grade chart may be used as a reference for quick classification based on the external colour appearance of mango fruits in the mango pack houses.

For the export of fresh whole mango, the first and second stage would be more suitable for long and short distance respectively. For the pulping industry, the fourth stage would be most suitable to get good quality finished product.

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CONCLUSION Scientific way of classification of the ripening

period of Indian mangoes into different stages were carried out for the mango varieties viz. Alphonso and Banganapalli.

The colour grade charts were developed and the entire ripening period were classified into five stages viz. unripe, early ripe, partially ripe, ripe, over ripe/decay using PCA and hierarchical cluster analysis.

The optimum stage suggested for fresh produce packaging is stage 1 and 2 and for pulping is stage 4.

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REFERENCES1. Agravante, J., Matsui, T., Kitagawa, H., 1990. Starch

breakdown and changes in amylase activity during ripening of ethylene-and ethanol-treated bananas. Acta Hortic. 269, 133–140. Anonymous. 2014. DGCIS annaul .

2. Boudhrioua, N., Giampaoli, P., Bonazzi, C., 2003. Changes in aromatic components of banana during ripening and air-drying. LWT-Food Sci. Technol. 36, 633–642. Boudhrioua, N., Michon, C., Cuvelier, G., Bonazzi, C., 2002. Influence of ripeness and air temperature on changes in banana texture during drying. J. Food Eng. 55, 115–121.

3. Camps, C., 2010. Non destructive measurement of tomato quality by portable near infrared spectroscopy. [French]. Revue Suisse de Viticulture. Arboricult. et Horticult. 42, 298–303

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