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Effect of post-harvest treatments on quality attributes like total soluble solids, total sugar and reducing sugar of langra mangoes ( Mangifera indica L.) during storage

The effect of calcium salts (calcium nitrate and calcium chloride) and Gibberellic acid on quality attributes and consumer’s acceptability of Langra mangoes during storage was examined. The fruits were treated with Ca(NO 3 ) 2 at the concentration of 1, 2 and 3 per cent, CaCl 2 at the concentration of 1, 2 and 3 per cent and GA 3 at the concentration of 50, 100 and 150 ppm. Water treated fruits were taken as control. Data were recorded in respect of TSS, reducing sugars and total sugars under influence of these treatments. All treatments were found effective in maintaining the higher level of these quality attributes of fruits during entire course of the experiment. At end of trial, Ca(NO 3 ) 2 at 2% was proved as the best treatment in respect of TSS, reducing sugars and total sugars and was able to maintain the level of these up to 24.32%, 9.00% and 20.05% respectively.


Introduction
Mango (Mangifera indica L.) is a tropical, climacteric fruit that is very popular among million of peoples world-wide. Mango, the king of fruits belongs to family Anacardiaceae. Mango is fifth widely produced fruit crop in the world after banana, apple, grape and orange. India ranks first in term of production in the world. It contributes approximately 50% of the global mango supply. In India, during 2015-16, it was grown in an area of 2.209 million hectares with a production of 18.643 million tonnes and productivity of 8.4 tonnes/ hectare (Anonymous, 2017) [2] . Nutritionally, it contains β carotene, β cryptoxanthin, vitamin C, and dietary fibre (Pal, 1998) [12] as well as soluble sugars and various minerals used as good sources of nutrition, and are readily available and easily assumable in human body   [1,18,19] . Approximately 30-50% fruits wasted during postharvest handling, storage, and ripening. Among the fruits mango manifested high postharvest losses because of its high perishability and climacteric pattern of respiration. Mango always decays after harvest, and postharvest losses can be minimized by applying improved storage technology and prolonging the shelf life of fruits. Among the cultivated varieties of Bihar, the variety Langra is most famous and is one of the most popular cultivars of India (Khara et al, 2016) [4] . In domestic market this variety has good demand and is able to fetch highest price in the market of Bihar. However, owing to its highly perishable nature and below average keeping quality, export potential of this variety is yet to be capitalised. Earlier efficacy of pre and post-harvest applications of certain chemicals and growth hormones in maintaining the quality of fruits during storage has been established. Gibberellins as a preharvest spray was reported as an efficient growth regulator in enhancing fruit storability and marketability through its action on cell juvenility and retardation of senescence, fruit coloration and softness (Macleod and Millar, 1962) [9] . Post-harvest spray of calcium increases the productivity of mango due to reduction of abscission and it enhances the fruit quality by increasing the fruit firmness and by maintaining the turgidity of middle lamella cells (Ranjan et al., 2005) [17] . Fruits storability was also improved by CaCl2 under cold storage (Ahmed et al., 2000) [1] . Low fruit calcium levels have been associated with reduced post-harvest life and physiological disorders. Pre-harvest sprays of calcium compounds and GA3 significantly retained more sugar content and ascorbic acid in mango fruits along with better consumer acceptability during storage (Rani and Brahmachari, 2003) [16] . Banerjee and co-workers (2016) [3] recorded minimum reduction in TSS and maximum retention of acidity with the application of GA3 during 17 days of storage of Amrapali mango fruits. Mounika et al. (2017) [11] recorded higher level of TSS, sugars and acidity in Amrapali mango fruits treated with calcium salts as postharvest application. Singh et al. (2017) [1,18,19] while working on Dashehari and Amrapali cultivars of mango proved the potential of calcium nitrate and calcium chloride in preserving valuable attributes of post-harvest quality (TSS, total sugar and acidity contents) of mango of fruits during storage.

Materials and Methods
The experiment was conducted in the Department of Botany, Jai Prakash University Chapra (Bihar) during the cropping year of 2018-19. The physiologically matured fruits were purchased from the market and carried to the experimental laboratory in bamboo baskets. The maturity was judged on the basis of fruit colour changes from greenish to the pinkish, flatness of the tubercles and smoothness of the epicarp as suggested by Pandey and Sharma (1998) [13,19] . The fruits divided in different lots were dipped for five minutes in aqueous solution of different chemicals at different concentrations separately. The experiment consisted of 10 treatments which are Ca(NO3)2and CaCl2 each at 1%, 2% and 3% per cent, and GA3 at the concentration of 50, 100 and 150 ppm and Control. The control fruits were dipped in water and kept for comparison. Fruits were stored after air drying at room temperature. The storage was terminated on the day when the fruits exhibited 12 per cent or more loss due to rotting under best treatment. The data were recorded on total soluble solids (TSS%), reducing sugar (%), total sugar (%). TSS (%) was determined by putting two drops of homogenized juice on the prism of hand refractometer and values were expressed as percentage. Reducing sugar was estimated by Lane and Eynon (1923) [7] copper titration method. For estimation of total sugar 10 ml of freshly extracted juice was first hydrolysed adding 5 ml of concentrated HCL and then left for 24 hours and after that it was neutralized by adding saturated sodium hydroxide (NaOH) solution. For testing, complete neutralization blue and red litmus papers were used. After this total sugar was estimated using Lane and Eynon (1923) [7] copper titration method.

Result and Discussion Total soluble solids (TSS %)
The rate of increase in TSS content was greatly influenced by different treatments (Table-1, Fig.-1). In general, initially TSS content was increased and after attaining a peak showed a declining trend. On the last day of storage maximum (24.32%) TSS was with Ca(NO3)2 at 2 per cent followed by GA3 100 ppm (24.0 %)and both these treatments were very closed to each other. Whereas, the minimum (17.43%) TSS was noted under control. Observations on similar lines were also noted earlier by Patil and Bodke (2018) [14] in mango and Pimpalpalle et al. (2017) [15] in sweet oranges. According to Stahl and Campbell (1936) [20] , the conversion of cell wall materials such as pectin and hemicellulose in simpler substances during storage are responsible for increase in TSS content. The higher values under calcium and GA3 treated fruits might be due to the greater pace of this conversion and slower pace of degradation owing to reduced respiration (Kumar, 2005) [6] . Koksal et al., (1994) [5] opined that the decline in TSS content in later days might be due their utilization in evapotranspiration, respiratory process, and other biochemical activities.  Fig.-2). The last day observation exhibited significantly higher value (9.00%) of reducing sugar with Ca(NO3)2 at 2 per cent followed by 8.88% with GA3 100 whereas, significantly minimum value (6.45%) was recorded under control. These results are in close proximity with those obtained by Kumar (2005) [6] and Mounika et al. (2017) [11] . The initial increase in reducing sugars might be due to the hydrolysis of starch into reducing sugars and later on reduction could probably be due to utilization of these sugars in the process of respiration. The increase in reducing sugar content of fruits treated with Calcium salts and GA3 might be due to reduced rate of catabolic activities like respiration under the influence of these chemicals (Kumar, 2005) [6] .

Total sugar (%)
The average content of total sugars gradually increased with the advancement of storage period and registered a decline after attaining a peak (Table-3, Fig.-3). At the end, maximum (20.05%) total sugars was recorded with Ca(NO3)2 at 2 per cent which can be ranked with GA3 100 ppm having 19.78 per cent total sugars content. On the same day minimum value (14.37%) was with control.The similar effect of calcium salts and GA3 was reported in pear by Mahajan and Dhatt (2004) [10] and in mango by Mounika et al. (2017) [11] . The delayed increase in total sugars over a longer period of time in calcium and GA treated mango fruits might be attributed to delay in ethylene production and respiration rate of fruits.

Conclusion
All treatments were found effective in maintaining the higher level of the quality attributes as well as the consumer's acceptability of fruits during entire course of the experiment. At end of trial, Ca(NO3)2 at 2% was proved as the best treatment in respect of TSS, reducing sugars and total sugars. Hence it can safely be concluded that calcium nitrate at 2 per cent and GA3 at 100 ppm as post-harvest application can be used during storage of mango fruits in order to improve the quality attributes.