EXOGENOUS APPLICATION OF CALCIUM CHLORIDE INFLUENCES THE PHYSICO-CHEMICAL CHANGES IN SUGAR APPLES (ANNONA SQUAMOSA L.) FRUITS IN COLD STORAGE

A. K. Vandana*, G. J. Suresha and R. H. Hanamant. Department of Postharvest Technology, Kittur Rani Channamma College of Horticulture, University of Horticultural Sciences, Bagalkot, Arabhavi 591218, Karnataka. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

The physicochemical characteristics and shelf life of sugar apple fruits treated with control and calcium chloride (3, 6, 9%) for 5 minutes were studied. All tested treatments indicated a significant delay in the change of weight loss, firmness, respiration rate, titrable acidity, total soluble solids, colour (L*, a*, b*), and organoleptic evaluation in sugar apple fruits of experimental set than that of the control set. Moreover, the physicochemical analysis of sugar apple fruits of experimental set revealed that it also contain higher amount of titratable acidity and firmness. The significant impact of treatment is found on the least physiological loss of weight in the order of fruits treated with CaCl 2 6%. Hence, it could be concluded that post harvest chemical treatment with 6% of CaCl 2 has the potential to maintain the firmness, prolong the storage life upto 12 days and preserve in cold storage of 13±1ºC of valuable attributes of post harvest sugar apple, presumably because of its effect on inhibition of ripening and senescence processes. (1984 &1998) has explained, ripening of some tropical and sub-tropical fruits can be retarded by storage at lower temperatures; however, sugar apple is very sensitive to low temperatures, presenting chilling injury symptoms, typically peel blackening, flesh browning and loss of aroma and flavor. Freire-júnior, M. and Chitarra, A. B. (1999) reported that, Postharvest treatment of calcium chloride have attracted recent research interest as a promising new technique to maintain fruit quality during storage; which might be an alternative to disinfestations of fruit and could modify its response to other stresses. In particular, biotechnologists have shown increasing interest in the use of postharvest heat shock to alleviate chilling injury in various crops and also inhibit biochemical pathways involved in ripening and other biological processes in a number of fruits and vegetables. Factors that influence temperature responses include species, variety, cultivation methods, fruit size, morphology, physiological maturity, final temperature and duration of exposure at various temperatures and type of treatment. 1500 Lester, G. E. and Grusak, M. A. (2000) has explained, calcium chloride has shown promise in quality retention of fruits and vegetables. Pre-and postharvest application of calcium may help to reduce senescence during commercial and retail storage of fruit, with no detrimental effect on consumer acceptance. According to  calcium dips have been employed to improve firmness and extend the postharvest shelf life of a wide range of fruits and vegetables; the effectiveness of such treatments may be influenced by the combination of time and temperature. Increasing the calcium content can help to delay softening and decrease the incidence of physiological disorders. According to Poovaiah, B. W. (1986) calcium chloride has been reported to reduce the onset of ripening in sugar apple ( . According to Lima, sugar apples treated with CaCl 2 (6%) and stored at 16°C showed reduced weight loss, respiration rates, control of the peroxidase activity, and maintained higher firmness, as the biochemical processes of ripening were delayed. Joyce, D. C. et al., 2001 studied by treatment with 4% calcium chloride did not extend the shelf life of mangoes from four cultivars. In recent years, significant advances have been made in fruit storage by the use of CaCl 2 dipping alone or combined with other treatments. The aim of the present study was to investigate the effects of postharvest treatment of dipping in 3, 6 and 9% of aqueous CaCl 2 on the storage of sugar apple at 13±1ºC with 85% RH in cold storage.

Materials and Methods:-
Fruits of uniform size, shape and maturity were harvested in the evening and brought to the laboratory of the Department of Post Harvest Technology in plastic crates. The damaged, bruised, punctured and infected fruits were discarded manually. Then, the healthy fruits were pre-cooled in cold storage at 13±1°C for twelve hours to remove field heat. After removal from the cold room, fruits were thoroughly washed in 0.2 per cent sodium hypochlorite solution for five minutes to remove the surface microbial load and dirt adhered to the fruit surface. Immediately, fruits were air dried under fan to remove the surface moisture. These fruits were then used for further experimentation to impose different postharvest treatments to study their influence on behaviour and shelf life during storage.
The fruits were divided into four lots of 64 fruits with 16 fruits for each replication, the T 1 being control, the T 2 calcium chloride (3%), the T 3 with calcium chloride (6%) and the T 4 calcium chloride (9%) for 5 minutes. After subjecting to dipping for specific duration in the respective treatment, custard apple fruits were surface dried under electric fan. Then the fruits were packed in ventilated corrugated fiber board (CFB) boxes. Paper lining was provided between the two layers of the fruits and paper shreds were used to provide cushioning and avoid fruits directly coming in contact with each other.

Physiological parameters:-Physiological loss in weight (PLW %):-
In each replication, 4 fruits were ear marked to record the PLW. The marked fruits in each replication of the respective treatment were weighed individually at the beginning of storage to record the initial weight. On subsequent days of observation, the fruits were weighed again. The cumulative losses in weight of fruits were calculated and expressed as per cent physiological loss in weight.

Firmness (g):-
Firmness of custard apple flesh was measured on 4 sides of the fruit at regular intervals taking a fruit from each replication by using force guage (Make: Lutron FG-5000A). It was recorded in Newton.

Respiration rate (ml CO 2 /kg/h):-
Respiration rate was measured with a CO 2 gas analyzer (Make: PBI Dansensor, CheckMate -II) in static method. The fruit was weighed and placed in a hermetically sealed container of 1250 ml capacity for 60 minutes. At the end of incubation period, gas sample was drawn from the container head space using gas tight syringe and injected into the CO 2 analyzer. The change in CO 2 gas concentration in the head space and time was read in the instrument was recorded. The respiration rate of the fruit was expressed as ml CO 2 /kg/h.

Colour (L*, C* and h o angle):-
The colour of the samples was measured using a Lovibond colour meter (Lovibond RT300, Portable spectrophotometer, The Tintometer Limited, Salisbury, UK) fitted with 8 mm diameter aperture and the instrument 1501 was adjusted at 10° observer and D65 primary illuminant. The instrument was calibrated using the black and white tiles provided. Colour was expressed in Lovibond units L* (Lightness/darkness), C* (chroma) and h o angle (hue). Custard apple fruits were directly placed under the aperture of the colour meter.

Biochemical parameters:-TSS ( o B):-
The juice extracted by squeezing the homogenized fruit pulp through muslin cloth was used to measure the TSS. It was determined by using ERMA hand refractrometer, replicated four times and the mean was expressed in o B.
Titratable acidity (%):-A known volume of juice sample (10 ml) was taken and titrated against standard NaOH using phenolphthalein indicator. The appearance of light pink colour was marked as the end point. The value was expressed in terms of per cent titratable acidity of juice.
Statistical analysis:-Statistical analysis was performed using Web Agri Stat Package (WASP) Version 2.0. All data the collected were analysed by one-way analysis of variance (ANOVA). Significant differences among means at P ≤ 0.05 were determined by post hoc tests using Duncan's multiple range test.

Physiological loss in weight (PLW %):-
Results on effect of CaCl 2 on weight loss indicated significant differences. All the treatments involving CaCl 2 were able to reduce the PLW significantly when compared to control. However, the treatment involving CaCl 2 at 9 per cent effectively reduced the PLW (8.28±0.48, 10.42±0.29 and 15.25±0.96 per cent at 4, 8 and 12 days, respectively) during the storage at 13±1°C and 80-85 % RH.      (Table 1). Fruits dipped in CaCl 2 solution registered significant differences with untreated fruits (p<0.05). Calcium chloride at 6 per cent treated fruits recorded higher values (72.25 ± 1.71) which were on par with 9 per cent CaCl 2 treated fruits (71.00 ± 1.83) at 12 days of storage at 13±1°C and 80-85 % RH.

Initial value of hue (hᵒ) angle is 80:-
Lower alteration or higher retention of peel C* and h° values were noticed in the treatments involving CaCl 2 . The fact that calcium treatments reduce the respiration rate and delay fruit ripening (Faust and Shear, 1971a) is attributed to the effect of calcium in cytosol is regulation of respiratory activity. The fruit with less calcium content has a very high respiratory rate and the respiration rate is inversely related to calcium concentration (Faust and Shear, 1971b). Calcium concentration in the tissue cell wall directly influences the production of CO 2 and ethylene (Conway and Sams, 1987). Calcium chloride treatment of 9 per cent retained higher peel and pulp h° and C* values during 14 days at cold storage. This might be due to increased accumulation of calcium in the cell wall and middle lamella and also due to binding of calcium ions with protein molecules. As a result, the prevention of green pigment degradation that might have persisted during prolonged storage in cold storage. These findings are corroborate the works of

Phenols (%):-
Results pertaining to phenol concentration showed significant differences (p<0.05) with untreated and CaCl 2 treated fruits. Sugar apple fruits treated with 9 per cent CaCl 2 registered maximum phenols (2.23±0.06, 2.18±0.03 and 2.18±0.02 at 4, 8 and 12 days, respectively) during the storage and which was on par with 6 per cent treatment throughout the storage.