Comparative Post-harvest Behavior of Two Mango Cultivars (Sensation and Trementina) Growing in Venezuela

Angel Guadarrama and Angela Sarmiento

Department of Agricultural Botany, College of Agriculture, Central University of Venezuela, Maracay, Aragua 2021,Venezuela

Corresponding author: Angel Guadarrama, Ph.D., research field: postharvest physiology of tropical fruits. E-mail:angelguadarrama6@gmail.com.

Abstract: Mango is an important crop in Venezuela for domestic consumption in fresh form and industry uses and export purposes at low scale. The aim of this work was to make a comparative study of post-harvest behavior of two mango cultivars (Sensation and Trementina) growing in Venezuela. Fruits were harvested at physiological maturity and placed in the laboratory at ambient conditions to 25 +/- 1°C and 60-70 % relative humidity. Chemical analysis (total carotenoids, soluble solids and acidity ) and physiological analysis (respiratory activity). Postharvest behavior of two cultivars showed differences. Total carotenoids and soluble solids content were higher in Sensation cultivar. Respiration was higher in Sensation cultivar reaching climacteric peak eight days after harvest. Trementine cultivar reached its climacteric peak seven days after harvest. Titratable acidity tendency was similar in both cultivars. Results could be indicative of genetic variability in post-harvest behavior of two mango cultivars studied suggesting to

consider specific postharvest management for each cultivar.

Keywords: mango, Sensation, Trementina, postharvest, ripening.

1. Introduction

Mango (Mangifera indica L.) is considered as king of fruits due to its attractive color, aroma and jelly pulp packed with vitamin A but it is highly perishable in nature [1].

The ripening process of mango fruit involves a series of biochemical reactions or metabolic activities that cause chemical changes, increased respiration, ethylene production, changes in structural polysaccharides causing softening, degradation of chlorophyll and development of pigments by carotenoids biosynthesis, carbohydrates or starch conversion into sugars, changes in the organic acids, lipids, phenolics and volatile compounds, thus leading to ripening of

fruit with a softening of texture to an acceptable quality [2]

Respiration plays a central role in the overall metabolism of a plant and it is therefore often used as a general measure of metabolic rate. Under proper storage conditions, respiration proceeds at relatively low and stable rates throughout the storage period. However, respiration may increase or decrease based upon changes in storage conditions and the physiological status of the produce [3].

In heat treated Keith mangoes after harvest, the respiratory rate is greatly increased, finding that is increased to 5 times the normal value on storage conditions, suggesting

the increase in consumption of sugars and organic acids which may reflected in an organoleptic quality deterioration [4].

`Haden' and `Tommy Atkins' mangoes (Mangifera indica L.) were stored in air, 2, 3, 4 or 5 kPa O2 plus N2, or 25 kPa CO2 plus air for 14 days at 15 °C or 21 days at 12 °C, respectively, then in air for 5 days at 20 °C to determine their tolerance to reduced O2 levels for storage times encountered in typical marine shipments. All low O2 treatments reduced mature green mango respiration (CO2 production). Results indicate that pre-climacteric `Haden' and `Tommy Atkins' mango fruit are able to tolerate 3 kPa O2 for 2 or 3 weeks at 12 to 15 °C and that tolerance to low O2 decreases as mangoes ripen. Results also show that low O2 and high CO2 affect mango ripening differentially [5]

Carotenoids biosynthesis and its regulation during fruit development and ripening is a complex process that occurs alongside the differentiation of chloroplasts into chromoplasts and changes to the organoleptic properties of the fruit [6]

Accumulation of β-carotene during postharvest ripening of nine Thai mango cultivars was assessed after verifying extraction and high-performance liquid

chromatographic and the vitamin A potential of mangoes was evaluated at different ripening stages. Exponential development of mesocarp color and all β-carotene levels, was described for each cultivar allowing good prediction of mesocarp color (hue angle, H°) and vitamin A value at consumption ripeness.  [6]

Titratable acidity and total soluble solids influence flavor properties of mango. Acid concentration affected ratings for sweet, sour, pine/turpentine, astringent, and biting. Solids/Titratable Acidity correlated (P < 0.01) with and were useful predictors (r > 0.80) of sour taste and chemical feeling descriptors astringent and biting. It is evident from this study that sugars and acids enhance human perception of specific flavor in mango, including aromatics [7]

Because the sugars conferring sweetness and organic acids conferring acidity account for the major portion of total and soluble solids, most of the research concerning fruit quality has centered on these components [8]

Knowledge of processes physiological occurring during mango ripening is fundamental in leading the technical troubleshooting associated with postharvest of this fruit. As mentioned

above in ripening of mango fruits, a series of physical, chemical and physiological occur in pursuit of the final organoleptic quality of ripe fruit.

Trementina mango fruit smells like some hydrocarbon so are commonly called turpentine mangoes in Venezuela and are green or slightly yellow when ripe and Sensation is light yellow orange-yellow or reddish peel in color with very fine fiber and flavor is mildly sweet with a light aroma.

The purpose of the present study was to compare the postharvest behavior of two mango cultivars (Sensation and Trementina) growing in Venezuela by determination of some physiological and chemical parameters concerning to fruit quality in order to contribute in designing specific and appropriate handling to extend the shelf life of the studied mango cultivars

2. Materials and methods

2.1 Plant Material

Mangoes were harvested in green mature stage from a orchards during commercial harvest period, transported immediately to the laboratory, and stored at tropical ambient conditions (28±1°C and 68±2% RH) previously washed and treated with Benomile (1 g/l of water). The measurements on respiration of the samples were carried out one day after harvest until nine days for Trementina and thirteen days for Sensation and carotenoids, acidity and soluble solids were measured one day after harvest until seven days for Trementina and thirteen days for

Sensation when fruits reach acceptable full ripe for consumers.

2.2 Physiological Analysis

The respiration rates of two mango cultivars stored at 28±1 °C were determined using a respirometer designed in the laboratory to measure CO2 based on the fundamentals of CO2

collection arising from fruit respiration [9]. The method employed consisted of measuring respiration by carbon dioxide evolution. A stream of air was passed at a constant rate over a jar with fruits inside, and then into a solution containing alkali (NaOH) for CO2 absorption producing Na2CO3 that reacts with added BaCl to produce BaCO3, which is titrated with HCl solution using phenolphthalein as an indicator. Stoichiometry of these reactions allowed to determine the amount of CO2 produced per kg of fruit per hour.

2.3 Chemical Analysis

Total carotenoids were determinate according to McCollum method [10] using hexane as solvent and an average specific absorption coefficient of 224 obtained from α-carotene (248), β-carotene (228) and criptoxantol (216) and readings were performed on a Spectronic 20 at 470 nm. Results were expressed as mg of total carotenoids/100 g of peel.

Titrable acidity by AOAC method [11] for slightly colored solutions and titrating with 0.1 N NaOH and phenolphthalein as indicator. Results were expressed as % of citric acid

Soluble solids (SS) or ° Brix by means of the refractometer ATAGO N1 From

each fruit two longitudinal slices was taken. Samples were prepared by mixing two slices for every mango fruit using three replicates for analysis the slices were squeezed longitudinally to get a mixture of juice from all regions.

Soluble solids to titratable acidity ratio were calculated as the ratio between soluble solids and titrable acidity.

3.-Results and discussion

Variations in respiratory activity

Figure 2 shows post-harvest change in respiratory activity in the two mangoes cultivars studied during storage ripening at tropical ambient conditions (28±1°C and 68±2% RH). During the first to fourth days after harvest respiratory activity was almost similar for both cultivars. From the fifth day respiratory rate is greatly increased in Sensation cultivar to overcome thereafter the Turpentine cultivar until ripening ends.

Respiration of Sensation cultivar followed a climacteric pattern attaining a peak of 395 mg CO2 kg−1 hr−1 on the eighth day of storage while full ripeness was attained on the tenth day. Respiration of Trementina cultivar also followed a climacteric pattern but reaching a peak of 180 mg CO2 kg−1

hr−1 on the seventh day after harvest while completely ripeness In advanced stage of ripening (nine days after harvest),Trementine cultivars showed senescence and fruits become no acceptable for exigent consumers.

Fig 2 Variations in respiratory activity of two mango cultivars during fruit ripening

Similar pattern was reported in papaya [12] and banana [14] also climacteric fruits.

During respiratory activity, the production of energy from the oxidation of the own fruit reserves such as starch, sugars and organic acids. Once harvested, the product can not replace these reserves and the magnitude which decrease is an important factor in the duration of post-harvest life, so that the characterization of respiration is required for designing of storage appropriate to extend the shelf life of the two mango cultivars.

Respiration rate is an excellent indicator for metabolic activity of the tissues, and thus is a useful guide for the potential storage life of fresh fruits. Respiration rate is inversely proportional to shelf-life of the product, the lower rate the longer shelf-life

Variations in total carotenoid content

Figure 3 shows variation in the total carotenoid content for Trementina and Sensation cultivars, respectively. Total carotenoid production was always higher in Sensation cultivar since the beginning of ripening, reaching a value

of almost six times higher in relation to Trementina cultivar.

Sensation values in all stages of ripening are much higher than those of Trementina, reflecting possible genetic differences related to carotenoids metabolism. Under the environmental conditions of the experiment, Trementina full ripening is reached at 7 days and the Sensation at 11 days, reflecting also marked differences in the physiological processes involved in the ripening of these two varieties.

Carotenoids biosynthesis and its regulation during mango fruit development and ripening is a complex process that occurs alongside the differentiation of chloroplasts into chromoplasts and changes to the organoleptic properties of the fruit [3].

Fig 3 Variations in total carotenoids during of two mango cultivars during fruit ripening

The distribution of carotenoids, both qualitative and quantitative, during three stages of ripening of mango has been studied using chromatographic, spectroscopic and chemical methods. There was an increase in content as well as in number of carotenoids during ripening [15] .The mentioned study showed there were 15, 14 and 17

different carotenoids in the unripe, partially ripe and fully ripe mangoes, respectively. [15]

Variations in titrable acidity

Figure 4 shows a tendency to decrease the acidity of both varieties as ripening proceeds. Titratable acidity expressed as% citric acid, was always higher in Sensation and decreased along the ripening in both cultivars. During seven days of ripening, when Trementina reaches senescence, the acidity degradation tendency of the cultivars were similar and Sensation tendency to decrease was almost constant until senescence

Fig 4 Variations in titrable acidity in two mango cultivars during fruit ripening

This decrease could be attributed to the organic acids are used as reserve respiratory substrate during ripening. In all stages of ripening, titrable acidity values in Sensation cultivar are higher.

Fig 4 Variations in titrable acidity in two mango cultivars during fruit ripening

Fruits contain a number of organic acids, which are responsible for acid taste. The acids which are usually in relatively large amounts in mango fruits are  citric and malic acids were found to be the major organic acids [16].

Mango fruits acidity, as measured by titratable acidity is an important component of fruit organoleptic quality

Titratable acidity steadily decreased during ripening [13] and was found that acidity slightly increased in pulp and peel of three mango cultivars up to 20 days before physiological maturity and progressively decreased afterwards. During fruit ripening, titratable acidity was reported to increase up to the climacteric peak and declined afterwards in papaya [12], banana [14] mango [17] and guava [20]. These results support the view that acids can be used as substrates for respiration when sugars have been consumed or participated in the synthesis of phenolic compounds, lipids and volatile aromas and provide in addition, a series of metabolites which are used in many processes that reflect dominance of sweet flavor in mango fruit

Acidity plays an important part in the perception of fruit quality. It affects not

only the sour taste of the fruit but also sweetness, by masking the taste of sugars., the overall consumer appreciation is related more to the soluble solids/titratable acidity ratio than to the soluble sugars content alone. The proportions of individual acids are also important; for example, citric acid masks the perception of sucrose while malic acid seems to enhance sucrose perception. Two organic acids, citric and malic, are dominant in most fruit species, and understanding the elaboration of acidity requires studying the mechanisms involved in the accumulation of both. [18].

The organic acids present in the pulp of Keith mangoes at various stages of ripeness were analyzed by h.p.l.c. Acidity loss was shown by decreasing titratable acidity and increasing pH values. Citric and malic acids were found to be the major organic acids. A large decrease in citric acid and a small reduction in malic acid were responsible for the loss of acidity. Tartaric, ascorbic, oxalic and α-ketoglutaric acids were also shown to be present at low concentrations [19].

Variations in soluble solids

Changes in soluble solids were parallel to the changes in carotenoids of both mango cultivars. As fruits ripe the soluble solids content increased as shown in Figure 5, which is attributed to degradation of starch probably due to an increase in the activity of starch hydrolases enzymes.

Fig 5 Variations of soluble solids in two mango cultivars during fruit ripening

Soluble solids content was slightly higher in Sensation fruits in all stages of ripening comparing to those of Trementine. Generally the solids content (primarily sugars) increases in ripening fruit conferring to a more pleasant flavor as it improves the balance sugar-acid. Compositional changes of fruit pulp and peel during ripening of white- and pink-fleshed guava fruits were studied [20].

Total soluble solids increased in pulp and peel of both guava types with decrease in flesh firmness. More increase in total sugars was observed after the climacteric peak of respiration. Reducing sugars and titratable acidity increased up to the full-ripe stage and then decreased [20].

Soluble sugars of mango pulps are mainly composed of fructose, with about 30% sucrose and 20% glucose similarly, sucrose has been reported to be the major sugar in mango [13].

Significant increase in sucrose content of mango has been observed during

ripening and this has been attributed to an increase in total soluble solids during ripening. This is due to transformation of starch into soluble sugars as the carbohydrates in the fruit are broken down under the action of phosphorylase enzyme during ripening into simple sugars. On the other hand, hydrolysis of starch in the ripening mango fruit has been associated with amylase activity [17]

Variations in soluble solids to titratable acidity ratio

As show figure 6 the values of Soluble Solids/Titratable Acid ratio were found high in Trementina cultivar in almost stages of ripening reaching the maximum value at seven days after harvest while Sensation cultivar at 13 days after harvest

Fig 6 Variations of soluble solids to titratable acidity ratio in two mango cultivars during fruit ripening

The soluble solids/ titratable acidity ratio contributes giving mango fruits their characteristic flavor and so is an indicator of commercial and organoleptic ripeness. At the beginning of the ripening process the soluble solids/ titratable acidity ratio is low, because of low sugar content and high fruit acid content, this makes the fruit

taste sour. During the ripening process the fruit acids are degraded, the sugar content increases and the sugar/acid ratio achieves a higher value. Overripe fruits have very low levels of fruit acid and therefore lack characteristic flavor.

The overall consumer appreciation is related more to the soluble solids/ titratable acidity than to the sugars content alone.

4. Conclusions

Cultivars had a climacteric behavior but reaching different peaks and distinctive respiratory rate so respiration measurements is required for designing specific and appropriate storage to extend the shelf life of the studied mango cultivars

The behavior of total carotenoids ,soluble solids and soluble solids/ titratable acidity ratio showed different patterns during postharvest suggesting variability in organoleptic quality in the cultivars.

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