Modified atmosphere packaging maintains physico-chemical properties of custard apple (Annona squamosa L.) fruits

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1 Indian J. Agric. Res., 49 (6) 2015 : Print ISSN: / Online ISSN: X AGRICULTURAL RESEARCH COMMUNICATION CENTRE Modified atmosphere packaging maintains physico-chemical properties of custard apple (Annona squamosa L.) fruits R.A. Patil*, D.V. Sudhakar Rao and B. Manasa 1 Division of Post Harvest Technology, Indian Institute of Horticultural Research, Hessarghatta, Bengaluru , India. Received: Accepted: DOI: /ijare.v49i ABSTRACT Custard apple, a tropical fruit, is underutilized because of its poor storability. Researchers have worked on various aspects for improving the storage life of fruits; still its storage life is limited to few days. So to counteract this, an experiment was conducted to study the effect of modified atmosphere packaging using three different kinds of films along with low temperature storage at 8, 12 and 15 C and observations were recorded at weekly interval. The study indicated an increasing trend in the respiration rate and ethylene production rate as well, and the rate increased with increase in storage temperature and duration. The physiological loss in weight in packed fruits showed a drastic reduction. Titratable acidity increased as storage duration while ascorbic acid shown exact reverse trend. There was significant increase in reducing sugar and total sugar as duration increased but rate was low in 8 C fruits. Key words: Low temperature, MAP, Post-harvest quality, Ripening, Storage. INTRODUCTION Custard apple (Annona squamosa L.), a native of Tropical America, is widely distributed throughout the tropical and subtropical regions of the world. It is grown on marginal lands and hillocks with minimum inputs (Rajput, 1985). The fruits are highly perishable with a very short post harvest life of 3 to 4 days under ambient conditions. The limited shelf life of the fruits is further reduced due to the unscientific handling practices, as in many growing regions the harvested fruits are directly loaded or packed in bamboo baskets with paddy straw or leaves of custard apple as cushioning material while transporting to the markets (Salunke and Kadam, 1995; Reddy, 2000). The safe range of storage temperature for extension of storage life of fruits has been found to be between 15-20ºC with maximum storage life of 9 d at 15ºC (Vishnu Prasanna et al., 2000). The custard apple fruits packed in low density polyethylene (LDPE) and stored at 12 C had better shelf-life of two weeks. These fruits ripened normally in three days after storage. The fruits packed in LDPE film scored highest sensory characters at all storage intervals when stored at 12 C (Patil et al., 2014). Below this storage temperature, fruits exhibited chilling injury characterized by hardening and blackening of fruit surface, and messy pulp. Also, the process of ripening can be controlled to certain extent by monitoring the storage conditions. Custard apple, being tropical in origin, is reported to be highly sensitive to chilling temperatures and develops symptoms of blackening when storage temperature falls below 10 o C (Ke et al., 1983). When a commodity is continuously respiring, it leads to the exhaustion of O 2 inside the pack and there is generally a buildup of CO 2 and equilibrium is reached when the rate of respiration is equal to the rate of permeation and as a consequence, steady concentration of O 2 and CO 2 are maintained (Singh, 2003). The technique of modified atmospheric packaging (MAP) has been reported to alleviate chilling injury and maintain the quality in a number of tropical and sub tropical fruits (Yahia and Paull, 1997). Reports by Broughton and Guat (1979) indicated that, the fruits ripened normally at storage temperatures of 15 to 30ºC, but were susceptible to fungal attack at temperatures higher than that of 25ºC. The fruits stored at 20ºC were observed to have optimum eating quality and shelf life, while storing them at 0.5 to 10ºC resulted in chilling injury. Physiologically mature fruits held at 12.5ºC had acceptable eating quality for over 7 days; but at elevated temperatures (20ºC and 25ºC), fruits lost eating quality within three days (Flores, 1982). According to Tsay and Wu (1989), *Corresponding author s raghwendrapatil@gmail.com. 1 Department of Horticulture, University of Agricultural Sciences, GKVK Campus, Bengaluru , KNK.

2 490 INDIAN JOURNAL OF AGRICULTURAL RESEARCH the fruits stored at 28ºC softened by fourth day and those at 20ºC by sixth day during storage, but those at 16ºC did not ripe completely even on 14 th day. The storage life of custard apple fruits could be extended up to two weeks when packed in low density polyethylene (LDPE) or Cryovac PD-961 film stored at 12ºC, without any chilling injury symptoms and the ripened normally in 3 d at room temperature (Patil et al., 2013). In this context, there is a pressing need to develop a suitable packaging techniques and storage system which can extend the shelf-life of custard apple without affecting its quality. The present investigation was, therefore, carried out to explore the possibility of employing modified atmosphere packaging (MAP) to alleviate the chilling damage and thereby enhance the shelf life and postharvest quality of the fruits. MATERIALS AND METHODS The present investigation was conducted at the Division of Postharvest Technology, Indian Institute of Horticultural Research (IIHR), Hessarghatta, Bengaluru, India. Fully mature green fruits, when the areas between two segments turned to cream colour, were procured from the Institute s farm and used for the experiment. The harvesting was done manually in the morning hours (8:00 to 9:00 am) and the fruits kept in the plastic crates with cushion at the bottom were transported to the laboratory. The fruits were sorted out to reject immature and, misshapen fruits and were graded for uniform size, to maintain homogeneity in the experiment. Medium size fruits weighing g were selected and cleaned by dry brushing to remove the adhering mealy bugs or dirt if any. The fruits were then packed in three different kinds of flexible films viz. low density polyethylene (LDPE), Cryovac Opti 300 and Cryovac PD The details about the permeability of these materials have been presented in Table 1. Eight fruits were sealed in each polythene film of cm size and each treatment had 3 replications. These packs were stored in ventilated Corrugated Fiber Board (CFB) boxes in the cold rooms maintained at 8, 12 and 15 C. At weekly interval, the fruits were unpacked and allowed to ripe at room temperature in the laboratory (28-32ºC) and the observations were recorded. Respiration rate: The respiration rate of modified atmosphere packed fruits was measured during their ripening after taking them out of the film at the specified storage intervals; whereas for control (non-packed) fruits, the respiration rate was measured regularly during the entire storage period. The individual fruit was enclosed in a hermetic container of known volume for 30 to 45 min and from the headspace gas, concentration of CO 2 was measured by piercing the probe of auto gas analyzer (Checkmate 9900 O 2 /CO 2, Denmark) in the container through the septa fixed on the lid of container and direct reading was noted from instrument screen. The CO 2 evolution was calculated in mg of CO 2 kg -1 h -1 by using formula: Respiration Rate (mg of CO 2 kg -1 h -1 ) 2 x %CO 2 x volume x 60 = [fruit weight (kg)] x [enclosing time (min)] x 100 Ethylene production rate: The ethylene production rate of modified atmosphere packed fruits was measured during their ripening by taking them out of the film at the specified storage intervals; whereas, it was measured regularly during the entire storage period for control (non-packed) fruits. The individual fruit was enclosed in a hermetic container of known volume for 30 to 45 min and from the headspace gas, concentration of C 2 was measured by piercing the probe of ethylene analyzer in the container through the septa fixed to the lid of container. The production of C 2 was calculated in µl of C 2 kg -1 h -1 by using formula: Ethylene, (µl of C 2 kg -1 h -1 ) C 2 (ppm) x volume x 60 = [fruit weight (kg)] x [enclosing time (min)] x 100 Where, volume = (container volume- fruit volume) Physiological loss in weight (PLW): Individual fruits were numbered in each treatment to record the physiological loss in weight. The weight of numbered fruits were recorded regularly during storage (non-packed control fruits) and during ripening (both non-packed control and unpacked ones), with the help of digital weighing balance (FX-2000, Japan). TABLE 1: Permeability of the films to gases. Film Permeability O 2 (ml mil -1 m -2 CO 2 (ml mil -1 m -2 Water Vapor Transmission day -1 atm -1 ) day -1 atm -1 ) Rate (g m-2 day -1 at 38 o C 90 % RH LDPE , , Cryovac Opti , Cryovac PD (Source: As per the Manufacturer s citation)

3 From these values, the cumulative PLW was calculated and expressed as percentage. Total titratable acidity and ascorbic acid: The total titratable acidity as well as ascorbic acid of custard apple pulp samples were determined by visual titration method as described by Ranganna (1986). Sugars: Sugars present in the custard apple pulp samples were estimated following the method outlined by Lane and Eynon described by Ranganna (1986). Statistical analysis: The observations recorded under each parameter were statistically analyzed following factorial completely randomized design (Sunderraj et al., 1972). RESULTS AND DISCUSSION Respiration rate: The average respiration rate of the fruits stored at 8ºC was mg of CO 2 kg -1 h -1 on second day of storage, which increased very slowly with storage period and it was recorded highest (51.31 mg of CO 2 kg -1 h -1 ) on 19 th day of storage (Figure 1A). The data on respiration rate of the fruits after different storage interval revealed that, irrespective FIG 1: Respiration rate of custard apple fruits (A) during storage storage at low temperature (8.12 and 15 o C) (B) during ripening at room temperature (28-32 o C) after one week storage at low temperature and (C) during ripening at room temperatue (28-32 o C) after two weeks storage at low temperature (Mean +SD, n=3) Volume 49 Issue 6, of temperatures the respiration rate of the MA packed fruits was lower than that of control or non-packed ones. Amongst the films, the LDPE film was better in terms of reducing the respiration rate followed by Cryovac PD-961 and Cryovac Opti 300. The storage of fruits (non-packed) at low temperature resulted in very low respiration rate throughout the storage (Figure 1B and 1C). The rate of respiration of fresh produce is a temperature dependent process and is regulated by many enzymes. The low storage temperature results in the reduced enzyme activity, thus lowering the rate of respiration. The rate of respiration generally shows an inverse relationship with the potential storage life of a commodity (Nazeeb and Broughton, 1978; Lam, 1990; Vishnu Prasanna et al., 2000; Mallikarjuna et al., 2012). The non-packed fruits stored under ambient conditions showed an upsurge in the rate of respiration on the fourth day of storage. The pronounced increase in respiration coincident with ripening, termed as climacteric peak, was a natural phenomenon in the climacteric fruits (Vishnu Prasanna et al., 2000). When the fruits were shifted to room temperature after unpacking, the respiration rate was recorded lower in fruits packed in LDPE compared to the fruits packed in other films. The reduced rates of respiration of LDPE packed fruits were probably due to the positive residual effects of modified atmosphere on fruits after transferring to air during post storage ripening (Li and Kader, 1989; Vishnu Prasanna et al., 2000). Ethylene production rate: The fruits stored at 8 o C did not produce ethylene up to 4 th day of storage, from 5 th day onwards they produced the ethylene gradually up to 12 th day ( µl of C 2 kg -1 h -1 ) and then decrease in production of ethylene was observed. The fruits stored at 12ºC and 15ºC showed more ethylene production as compared to the fruits stored at 8ºC (Figure 2A). The perusal of data pertaining to ethylene production rate after two weeks of storage at LT revealed that the fruits taken out from all the MA packaging films and non-packed control had ethylene peak on 3 rd day of shifting to RT and it declined afterwards (Figure 2B). When the fruits were shifted to room temperature after storage, the non-packed control fruits stored at 8ºC showed highest ethylene production ( µl of C 2 kg -1 h -1 ) and the least was recorded in the fruits stored in Cryovac PD-961 (83.14 µl of C 2 kg -1 h -1 ). Packing of fruits in LDPE and Cryovac PD 961 films could successfully reduce the rate of ethylene production (Figure 2B) during ripening, when the fruits were shifted to room temperature. At lower temperature, the ethylene production of fruits decreases as compared to higher temperature (Wills

4 492 INDIAN JOURNAL OF AGRICULTURAL RESEARCH FIG 2: Ethylene production rate of custard apple fruits (A) during storage at low temperature (8, 12 and 15 o C) during ripening at room temperatue (28-32 o C) after two weeks storage at low temperature (Mean + SD, n=3) et al., 1984). The non-packed fruits stored at 8ºC did not exhibit the characteristic ethylene peak during storage (Figure 2A), which might be due to absence of the respiratory climacteric peak in these fruits as reported in the Figure 2B. The ethylene production behaviour of modified atmosphere packed fruits also varied significantly after storage at different temperatures. The irregularities in the ethylene production behaviour might be due to chilling injury or unfavorable gas atmosphere surrounding the fruits inside packing during storage. However, ethylene production behaviour of LDPE packed fruits was observed quite regular during ripening. The fruits packed in Cryovac PD-961 showed the intermediate response to ethylene rise after removing from packs during ripening. The reason for differential responses of these fruits packed in different films towards ethylene production behaviour could be due to the difference in modified atmosphere conditions and the duration of exposure of these fruits to these conditions. Elevated CO 2 atmospheres could reduce, promote or have no effect on ethylene production or action in fruits, depending upon the commodity, variety, physiological age, initial quality, CO 2 concentration, temperature and duration of exposure to such conditions (Kader 1986). Physiological loss in weight: As the storage temperature decreased, the PLW also decreased and it was less in the fruits that were packed in any film compared to non-packed control. The packaging film might have served as a physical barrier around the fruit to reduce air movement across its surface and secondly, created modified humid atmosphere around it which resulted in reduced PLW. The PLW of the TABLE 2: Effect of modified atmospheric packaging on physiological loss in weight (%) of custard apple fruits during storage at low temperature and subsequently during ripening at room temperature (n=3). 1 WEEK AT LT 1 WEEK LT+ 2D RT 1 WEEK LT + 3D RT 1 WEEK LT + 4D RT T1 T2 T3 Mean P T1 T2 T3 Mean P T1 T2 T3 Mean P T1 T2 T3 Mean P P P P P Mean T C.D. at 5 % NS S.Em.± F test ** ** ** ** ** NS ** ** ** ** ** ** 2 WEEKS AT LT 2 WEEKS LT + 2D RT 2 WEEKS LT + 3D RT T1 T2 T3 Mean P T1 T2 T3 Mean P T1 T2 T3 Mean P P P P P Mean T T P T P T P T P T P T P C.D. at 5% S.Em.± F test ** ** ** ** ** ** ** ** ** Temperature Packaging Film Interaction = (T P) (n=3) T 1 = 8 0 C P 1 = Low density polyethylene (LDPE) P 3 = Cryovac PD- 961 LT= Low Temperature (8 0 C, 12 0 C, 15 0 C) T 2 = 12 0 C T 3 = 15 0 C P 2 = Cryovac Opti 300 P 4 = Control (non-packed) RT= Room Temperature (26-32 o C) (n=3)

5 Volume 49 Issue 6, fruits at 8ºC was significantly less during storage and also during ripening. The physiological loss in weight during ripening was significantly high in all the packages and control. The results showed that the fruits lost a part of its original weight during the process of ripening and this loss varied with the duration of ripening and ripening conditions. The PLW of fruits after one week storage was recorded least in the fruits packed in LDPE and stored at 8ºC (0.72%) and was highest in the control fruits stored at 15ºC (7.37%). When these fruits were shifted to room temperature for ripening, the fruits packed in LDPE showed less PLW at the end of ripening process (4 th day) compared to control and that of fruits packed using other films (Table 2). When the fruits were stored for two weeks at LT the PLW was recorded least in the film LDPE and stored at 8ºC (0.88%) and highest in non-packed fruits stored at 15ºC (8.52%). The similar trend was observed during subsequent observations during ripening process (Table 2). The high PLW in non-packed fruits stored at LT might be due to chilling injury, which damaged the surface organization of the tissue and allowed a much greater loss of moisture through the damaged areas (Li and Kader, 1989). The reduced level of PLW in modified atmospheric packaging was also observed by Silva et al. (2012). Total titratable acidity: The fruits stored at 8ºC had the highest percentage of acidity (1.15%) which was significantly higher than those stored at 12ºC (0.94%). During ripening, the change in acidity was influenced by storage temperature, packaging film and interaction (Table 3). The fruits stored at 12ºC were found to have the highest acidity (0.54%) when compared with the fruit stored at 8ºC (0.37 %). The changes in titratable acidity revealed that there was a progressive decrease in the acid content during storage as well as ripening. However, the retention of titratable acidity might be affected by the modified atmosphere conditions because packed fruits showed a little higher acid content over control. These results are in accordance with those obtained by Silva et al. (2012), when they stored custard apple fruits using different polyfilms. After storage, the titratable acidity was recorded higher in fruits stored at low temperature (8ºC) compared to fruits stored at higher temperature (15ºC). However, after ripening TABLE 3: Influence of modified atmospheric packaging on quality attributes of custard apple fruits stored under different conditions (n=3). Acidity (%) Vitamin C (mg/100g) Reducing sugar (%) Total sugars (%) T 1 T 2 T 3 Mean P T 1 T 2 T 3 Mean P T 1 T 2 T 3 Mean P T 1 T 2 T 3 Mean P One week at low temperature (8 0 C, 12 0 C and 15 0 C) storage. P P P P Mean T % NS NS NS 1.94 NS NS 2.28 NS NS S.Em. ± F- test * * * NS NS NS ** NS NS ** NS NS After ripening at room temperature (26-32 o C) preceded by one week low temperature (8 0 C, 12 0 C and 15 0 C) storage. P P P P Mean T % NS NS S.Em. ± F- test NS ** * * * NS ** ** ** ** * ** Two weeks at low temperature (8 0 C, 12 0 C and 15 0 C) storage. P P P P Mean T % 0.05 NS NS NS NS NS NS NS S.Em. ± F- test * NS NS NS NS NS ** ** * ** NS NS After ripening at room temperature (26-32 o C) preceded by two weeks low temperature (8 0 C, 12 0 C and 15 0 C) storage. P P P P Mean T % NS NS NS S.Em. ± F- test ** ** ** NS NS NS ** ** ** ** ** **

6 494 INDIAN JOURNAL OF AGRICULTURAL RESEARCH at RT, reverse trend was observed wherein titratable acidity was more in fruits stored at high temperature compared to fruits stored at low temperature. The decrease in acidity during ripening may be due to conversion of acids to sugars or due to utilization of organic acid in respiratory process at the higher temperatures (Ulrich, 1970; Sankat and Maharaj, 1997). Ascorbic acid: Retention of ascorbic acid was more at higher storage temperature (12ºC and 15ºC), when compared with the lower temperature (8ºC). Fruits packed in Cryovac PD- 961 could significantly retain the ascorbic acid content at all the three temperatures after one week storage (Table 3). The storage temperatures, films as well as interaction of both could not affect the ascorbic acid content in fruits stored for 2 weeks. The temperatures did not show the significant difference between each other though, fruits stored 8ºC and 12ºC had more ascorbic acid content (2.60 mg) than 15ºC (2.40 mg) (Table 3). Ascorbic acid content in custard apple fruits decreased as the days of storage increased. Initially (At harvest) the ascorbic acid content of fruits was 6.60 mg/100g and it decreased in all storage intervals. The reduction in ascorbic acid content might be due to the activity of oxidative enzymes (ascorbic acid oxidase) during storage, leading to the oxidative reduction of vitamin C in presence of molecular oxygen (Pruthi et al., 1984). The ascorbic acid content of the fruits stored in films was reduced, possibly due to the higher concentration of CO 2 in MA packed film (Shrinivas et al., 2002). Sugars: Reducing sugar content in the custard apple fruits was significantly influenced by the storage temperature irrespective of films in all two storage intervals viz. one week and two weeks. From data presented in Table 3 it could be said that, irrespective of film used, the reducing sugar in fruits stored at 8ºC increased steadily throughout the study. As the storage temperature increased, the reducing and total sugars also increased (Table 3). The increase in reducing sugars could be attributed to: (i) inversion of non reducing sugars in the pulp into reducing sugars which was enhanced in the presence of natural acidity present in fruit, (ii) increase in total sugars due to hydrolysis of some polysaccharides into sugars during ripening. The storage at lower temperatures retarded the processes, which could be the cause of lower level of increase in reducing sugars in the pulp samples. Fruits stored at low temperature (8ºC) showed significantly lower total sugar content than those at 15ºC. This could probably be due to slower ripening rate at the low storage temperature. As the days of storage increased the total sugars also increased. This increase in total sugars could be due to hydrolysis of starch as reported by Lodh et al. (1970) and Smith et al. (1979). The continuous increase in sugars content during storage was observed by Vishnu Prasanna et al. (2000), wherein they observed that the changes were more rapid at 25 and 20ºC than at 15 and 10ºC. The total sugars increased as the storage period increased, irrespective of storage temperatures and packaging films. The possible reason could be attributed to the hydrolysis of polysaccharides like cellulose and hemicelluloses present in the pulp into sugars. The restricted increase in total sugars and reducing sugars in MA stored fruits after storage i.e. before ripening could be attributed to the effect of reduced metabolism rate. The reduced level of sugars in packed fruit at ripe stage could be attributed to the consumption of sugars due to higher respiration rate (Lodh et al., 1970; Smith et al., 1979). CONCLUSIONS When the fruits stored at 8ºC, the LDPE packed fruits were found better than those of Cryovac PD-961 with regard to all quality attributes, whereas quality was slightly affected in Cryovac Opti 300 packed fruits. At 12ºC, the quality of fruits with regard to physical, physiological and biochemical parameters was assured by LDPE film followed by Cryovac PD-961, and the fruits could be stored for 14 days when packed in LDPE or Cryovac PD-961 followed by 3 d at room temperature. While, at 15ºC, the high concentration of CO 2 in Cryovac Opti 300 packs resulted in loss of some quality parameters like ascorbic acid. The shelf-life of fruits was 2 to 3 days when these were ripened after 14 days of MAP. REFERENCES Broughton, W. J. and Guat, T. (1979). Storage conditions and ripening of custard apple (Annona squamosa L.). Scientia Horticulture, 1: Flores, G. A. A. (1982). Studies on the dynamics of fruit ripening in soursop (Annona muricata L.). 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