Interaction effect of plant extracts and natural ethylene sources on ripening behaviour, shelf life and quality of banana cv. grand naine (AAA) under ambient conditions (ratoon crop)

Introduction

Banana (Musa spp.) belongs to the family Musaceae is one of the oldest fruits known to mankind. It is also known as Apple of Paradise and one of the most important sources of tropical fruits in the world as it is a significant staple food as well as a major export commodity (Rahman et al., 2013) [5] . Banana holds a high position in fruit and food crops of the tropical and sub-tropical regions and good source of income for growers and its taste and high nutritional value keep it in high demand by consumers throughout the year. The use of various chemicals and waxing material at the pre and post-harvest stages is becoming popular among growers in order to enhance the shelf life of fruits. However, the use of these substances has their own limitations, as some of them are believed to be ecologically unsafe and economically not viable besides leaving their residue on the fruit surface, which may have the direct effect on human health. Additionally, some of them may be associated with the changes of aroma of the fruit. Coating of plant leaf/flower extract forms a thin film around each fruit, which act as a semipermeable membrane to regulate the diffusion of oxygen and carbon dioxide into and out of the fruit, thereby reducing the rate of metabolism and also preventing water loss (Umesh et al., 2017) [9] . Post-harvest application of botanicals such as Azadirachta, Ocimum, Aloe, Tagetes, Mentha, Gingiber, Curcuma, and Eucalyptus which are known to contain higher amounts of some principle natural substances exhibiting growth regulating, fungicidal, insecticidal properties can be exploited for retaining freshness and enhancing the shelf life of horticultural crops. Successful marketing of edible cultivated bananas requires control over the ripening process to ensure predictable ripening and good quality ripe fruits. Thus, most bananas are harvested in the unripe stage, transported to destination markets where they may be induced to ripen by exposure to ethylene prior to sale. Unripe bananas can normally be initiated to ripen by exposure to an exogenous source of ethylene (100 to 1000 µl l -1 for 24 hours) under high humidity and controlled temperature conditions in specially designed ripening rooms (Soltani et al., 2010) [7] . Fruits may be classified as climacteric or non-climacteric depending on its respiration rate. The level of ethylene present in ripe climacteric fruitis more than sufficient for inducing the major ripening associated events such as softening and colour changes. Fruits like avocado, banana, mango, pear and tomato produce 500, 40, 3, 40, 35 µg/l (µg l) ethylene at the climacteric peak (Belitz et al., 2009) [1] while the threshold level of ethylene for fruits like avocado, banana, mango, tomato ranges from 0.1 to 0.5 ppm.

Materials and Methods

The experiment was conducted with factorial completely randamoised block design with three replications with sixteen treatments. The treatment details are with different plant extracts i.e., E 1 -Leaf extract of Neem (Azadirachta indica) 20%, E 2 -Aloe vera gel extract (Aloe barbadensis) 20%, E 3 -Rhizome extract of Ginger (Zingiber officinalis) 20% and with different natural ethylene sources like N 1 -Apple, N 2 -Sapota, N 3 -Papaya, N 4 -Tomato, N 5 -Banana and one treatment is control without imposition of any treatments.

Preparation of Extracts

Aqueous extracts of different plant materials shall be prepared under laboratory conditions on per cent weight basis as per the method described by Gakhukar (1996) and Sharma et al. (1997) [2,6] .

Neem leaf extract

The method consists of collection of fresh leaves, followed by shade drying and then grinding them to powder form in an electric blender. Fresh green leaves of neem were collected blended with distilled water. Then 20% neem leaf extract solution was prepared by taking 60 ml of raw neem leaf extract in 500 ml beaker with the addition of 240 ml distilled water separately to make a final volume of 300 ml (Suva laxmi and Dash 2017) [8] . Finally, the extracts solutions were filtered before use and stored in refrigerator at 5°C

Aloe vera gel extract

For preparation of aloe vera gel extract, aloe vera gel matrix was separated from the outer cortex of leaves and this colourless hydro parenchyma was ground in a blender. The resulting mixture was filtered to remove the fibre. The liquid obtained constituted fresh Aloe vera gel. It was later be stored in brown Amber bottle to prevent oxidation of the gel.

Ginger rhizome extract

In case of ginger rhizomes fresh juice was extracted and then different concentrations were prepared by dilution. The extract was stored in bottles till use. Aqueous solutions were prepared by soaking a known weight of the extract in an equal quantity of water and keeping it overnight. The extract was separated with the help of muslin cloth and it was considered to be of 100 per cent strength. It was diluted by adding appropriate quantity of distilled water to make up the desired concentration. After harvesting 80-85% matured fruits are taken for the treatment. Ripened fruits (apple, sapota, papaya, tomato and banana) placed along with some unripe matured fruits (in a ratio of 1:100 in a closed environment (Prashanta,2014)) to initiate ripening.

The interaction treatments showed the significant difference among them. Among the different interactions treatment E2N4 showed the lowest (2.32) physiological loss in weight on the 3rd day which was at par with E 2 N 5 (2.42) and E 2 N 3 (2.43) and highest loss (4.65) recorded in E 3 N 1 and in control (4.72). Whereas same increasing trend of physiological weight was observed from 6 th to 18 th day. On 18 th day E 2 N 4 showed the lowest (12.28) physiological loss in weight which was at par with E 2 N 5 (14.31) and E 2 N 3 (14.41) followed by E 2 N 2 (14.84) and highest loss (16.95) in E 3 N 1 . The physiological loss of weight (14.82) was recorded in control on 12 th day. Aloe vera gel in combination with different ethylene sources has given the significant results for the main crop of banana. Among the different treatments the aloe vera gel in combination with tomatoes given the better results when compared to the combination with apples this might be due to the fact that apple is a good generator of ethylene and initiated the ripening process faster than the other fruits. The mechanism involved in the positive effect of aloe vera gel can be explained based on its hydrophobic property which enables formation of a barrier to water diffusion between the fruit and outside environment thus avoiding its external interference.

Fruit color (Score) Among the different interactions treatment E2N4 showed the lowest (1.09) change in fruit colour and the highest (1.35) on the 3 rd day in E3N1and in control (1.52). Whereas same increasing trend of fruit colour was observed from 6 th to 18 th day. On 18 th day treatment E2N4 showed the lowest (4.32) change in fruit colour and the highest (6.53) was recorded in E3N1.The fruit colour (6.92) was recorded in control on 12 th day. The earliest visual sign of ripening was a change in colour primarily due to disappearance of chlorophyll at peak and post climacteric stage, higher amount of ethylene released from apples during peak climacteric period. Aloe vera coated fruits showed a lesser loss in chlorophyll, lesser development of xanthophyll and reduced rate of ripening. Many coatings have the added advantage of providing a moisture barrier that reduces dehydration in the fruit during storage. Similar results of colour retention in coated fruit had been reported in carambola fruits (Neeta et al., 2013) [3] Fruit spoilage (%) No spoilage was seen up to 3 days of storage. Among the different interactions treatment E 2 N 4 showed the no spoilage and the highest (2.68) on the 6 th day in E3N1and in control (3.10). Whereas same increasing trend of fruit spoilage was observed from 6 th to 18 th day and almost the results obtained in these days were found to be non-significant. On 18 th day treatment E 2 N 4 showed the lowest (5.28) spoilage and the highest (7.97) was recorded in E3N1.The spoilage (8.47) was recorded in control on 12 th day This is because aloevera gel is not only capable of reducing the rate of respiration and ripening process but also can significantly retard the growth of bacteria, fungi and molds that is known to cause rotting in fruits. Mature fruits coated with Aloe vera showed an extended life in comparison to control, which may be attributed to its antimicrobial properties and hygroscopic properties of gel that enable the formation of a barrier to diffusion of gasses and water vapour between fruit and environment.

Fruit firmness (kg/cm 2 ) Among the different interactions treatment E 2 N 4 showed the highest (4.58) firmness on the 3 rd day which was at par with E 2 N 5 (4.52) and E 2 N 3 (4.51) followed by E 2 N 2 (4.32) and lowest (3.03) in E 3 N 1 and in control (3.05). Whereas same trend was observed from 6 th to 18 th day. On 18 th day E 2 N 4 showed the highest (3.17) firmness which was at par with E 2 N 5 (3.05) and E 2 N 3 (3.04) followed by E 2 N 2 (2.96) and lowest (1.90) in E3N1.The fruit firmness (1.96) was recorded in control on 12 th day. Synergistic effect of Aloe vera coating experimentally noted in reduced respiratory and transpirational loss in fruit weight, maintenance of fruit texture or firmness, activity of cell wall hydrolase and reduced rate of chlorophyll degradation and thereby extending shelf life and also less release of ethylene from natural ethylene sources.Aloe vera gel has been proved to maintain the texture of fruit efficiently. This may be due to the effect of Aloe vera gel on the reduction of galactosidase, polygalacturonase, and pectinmethyl-esterase activities.

Among the different interactions treatment E2N4 showed the long (24.00) shelf life which was at par with E2N2 (22.00), E2N3 (22.33) and E2N5 (22.67) followed by E2N1 (21.00) and less days (18.67) in E3N1. The Shelf life for the fruits in control is 13.45 days. Shelf life of any fruits calculated from the period of harvest up to rotting. Shelf life was the period of time which started from the time of harvesting and extended up to the start of rotting of fruit and it is the basic quality of fruit as well as it is the most important parameter in loss of reduction biochemical reaction of fruit and more release of ethylene from apples resulted in early ripening and thus resulting reducing the shelf life

Ripening days

Among the different interactions treatment E2N4 showed the long (11.45) days of ripening and less days (8.87) was observed in E3N1 and results for interaction found to be non significant and for the control it has taken 8.90 days. On the basis of results obtained, it can conclude that all the botanical extracts significantly reduced the ripening percentage in banana and in turn increased the shelf life of fruits. The retardation of ripening process observed in present study may be attributed to reduced ethylene production caused by the modified atmosphere and less ethylene from other climacteric fruits apart from apples. Many coatings have the added advantage of providing a moisture barrier that reduces dehydration in the fruit during storage. One advantage to the use of coatings in a fruit like bananas, is that the skin is not normally consumed, possibly providing greater flexibility in the choice of coating materials (Neeta et al., 2013) [3] .

References

1. Belitz HD, Grosch W, Schierberle P. Food Chemistry. 4th revised and extended edition. Springer Publications; 2009. USA.
2. Gakhukar RT. Commercial and industrial aspects of neem-based pesticide. Pestology. 1996;22(10):15-32.
3. Neeta BG, Manu LC, Rao TVR. Effect of edible coatings on quality and shelf life of carambola (Averrhoa carambola L.) fruit during storage. Journal of Food Science and Technology. 2013;13:988-989.
4. Prashanta P. Use of higher ethylene generating fruits for ripening as an alternative to ethylene. Journal of Food Science and Technology. 2014;13:345-349.
5. Rahman S, Biswas N, Hassan MM, Ahmed MG, Mamun ANK, Islam MR, Moniruzzaman M, Haque ME. Micropropagation of banana (Musa spp.) cv. Agnishwar by in vitro shoot tip culture. International Research Journal of Biotechnology. 2013;4(4):83-88.
6. Sharma RN, Tare V, Vartak PH. Bio-activity of some natural oils from Himalayan region on different insects. Indian Journal of Science and Research. 1997;1(1):1618.
7. Soltani M, Alimardani R, Omid M. Prediction of banana quality during ripening stage using capacitance sensing system. Australian Journal of Crop Science. 2010;4(6):443-447.
8. Suvalaxmi P, Dash DK. Influence of post-harvest application of plant extracts and storage condition on post-harvest physiology of mango cv. Amrapali. International Journal of Current Microbiology and Applied Sciences. 2017;6(8):1429-1440.
9. Umesh, Arjun K, Shrestha S, Srivastava, Shrestha. Ripening regulation and post-harvest life improvement of banana cv. Malbhog using plant extracts and modified atmosphere package. The Asian Journal of Horticulture. 2017;12:255-259.
10. Watharkar RB, Burbade RG, Landge KC. Effect of packaging material on shelf life and quality attributes of grapes (Vitis vinifera L.). International Archive of Applied Sciences and Technology. 2017;8(3):1-8.