Responses of GP3 and MD2 pineapple clones to post-harvest applications of some fruit coating materials
Ahmad Ziaurrahman1, Soesiladi Esti Widodo2*, Agus Karyanto2, Sri Waluyo3
1Study Program of Magister of Agronomy, Faculty of Agriculture, University of Lampung, Bandar Lampung, Indonesia
2Department of Agronomy and Horticulture, Faculty of Agriculture, University of Lampung, Bandar Lampung, Indonesia
3Department of Agricultural Engineering, Faculty of Agriculture, University of Lampung, Bandar Lampung, Indonesia
*Corresponding author email: [email protected]
Abstract. The challenge of maintaining shelf life will be faced when entering the market share of fresh pineapple. One way that can be used so that the fruit can survive during storage is by coating the fruit. Currently the use of coating materials is still very dependent on imported products. The objective of this study was to study the responses of two pineapple clones of GP3 and MD2 applied with 5 coating materials as post-harvest treatments, consisting of StaFresh 2952, OE6012, palm stearin, chitosan and the control without coating. All treatments were stored at 7oC and observed at days of 0, 7, 14, 21, 28 and 35. The results showed that the GP3 clone was more susceptible to Internal Browning (IB) disorders and this IB began to appear on day 14, much more earlier than the MD2 clone. The GP3 clone showed a Brix value of 13.9% and a vitamin C of 52 ppm which were significantly lower compared to the MD2 clone with a Brix value of 16.4% and a vitamin C of 586 ppm. From the results, the GP3 clone was considered not suitable as a fresh pineapple. The coatings were not able to prevent the IB disorders and to affect respiration rate, but they had significant effects on fruit weight loss, with StaFresh 2952 treatment consistently reduced weight loss by 11.8% until 35 days of shelf-life.
Keywords: coating, internal_browning, pineapple, postharvest, shelf-life
1. Introduction
Pineapple (Ananas comosus L Merr.) is a plant from the Bromeliaceae family. This fruit is one of the most important tropical fruits in the world, its production can reach 20% of the world's tropical fruits [1] Indonesia is one of the largest pineapple producing countries in the world with a total fruit production in 2020 of 2,447,243 tons, and Lampung Province contributes 27.07% to national
production [2]. The opening of Indonesian fresh pineapple market opportunities to foreign countries needs to be utilized for business expansion and development. The Great Giant Pineapple company, which currently produces canned pineapple using the Pineapple GP3 clone, feels the need to try to penetrate the market share of fresh pineapple which is dominated by the MD2 clone. Pineapple clone GP3 which is a pineapple cultivar 'Smooth Cayenne' has other advantages such as being more tolerant of Phytophthora sp. and also fruit collapse caused by Erwinia chrysanthemi, while pineapple MD2 is more resistant to Internal Browning (IB), but susceptible to fruitlet core rot and more sensitive to Phytophthora than 'Smooth Cayenne' [3].
IB is a typical postharvest chilling injury symptom in pineapples. Chilling injury is a complex physiological disorder that occurs in tropical and subtropical fruits, including pineapple, after exposure
to low temperatures (0–20 oC). This symptom is characterized by the appearance of brownish spots near the fruit core [4]. The challenge of maintaining shelf life will also be faced when reaching the market share of fresh pineapple. One way that can be used so that the fruit can survive during storage is by coating the fruit (Fruit coating). Currently the use of coating materials is still very dependent on imported products. so that alternative materials are needed that can be produced independently and are easily obtained. In this study, the raw material used came from stearin which is a palm derivative product as the main raw material. This raw material was chosen because Indonesia is the largest palm oil producer in the world with a production of 42.5 million tons in 2019 [5] so that the raw materials for making alternative coatings are relatively easy to obtain.
2. Metodologi
This research was conducted in June to August 2022 at the Postharvest Laboratory of Great Giant Pineapple Co. Ltd. - Plantation Group 4 which is located in East Lampung. The study was conducted for 35 days, in a cold storage at a cold temperature of 7 ºC. Observation was carried out on days of 0, 7, 14, 21, 28 and 35 after application. This study used a 2 x 5 factorial in a Completely Randomized Design with five replications. The main factor was two pineapple clones (GP3 and MD2), and the second factor was four coating treatments [K: control; C: chitosan (1% w/v); S: Sta-Fresh2952 (10% w/v equivalent to ºBrix 5.5), O: OE6012 (10% v/v equivalent to Brix º5.5) and P: Palm stearin (1% w/v) based coating materials consisted of palm stearin melted at 60ºC, chitosan (1% w/v), citric acid (2% v/v), and Tween 80/ Polysorbate 80 (2% v/v) so that the equality of ºBrix 5.5 was obtained.
Statistical analysis were performed using MINITAB Version 19 software. All data were analysed with an analysis of variance of one-way (ANOVA). If there was a treatment effect, the analysis was continued with a significant difference at P < 0.05 determined by Duncan’s Multiple Range Tests (DMRT).
2.1. Materials
The material used were pineapple with maturity level category SC0 (green fruit skin) which was harvested at the age of 144 days after forcing as many as 350 pieces consisting of GP3 and MD2 clones, with a weight range between 1000 - 1200 grams. Coating materials were StaFresh-2952, OE- 6012, Palm stearin-based coating materials, and chitosan.
2.2. Process of Coating and Its Application on Pineapple Fruit
For coatings made from palm stearin, the concentration used was 1% which was mixed with the Tween80 emulsifier as much as 2% and also 1% chitosan along with 2% citric acid then boiled and stired evenly at 60 ºC until all ingredients were evenly mixed. Meanwhile, the coating of chitosan was a coating made from pure chitosan with a concentration of 1% which was dissolved using 2% citric acid at a temperature of 60ºC. The Sta-Fresh2952 and OE6012 coatings were existing coating products whose applications in this study were diluted using water into a concentration of 10%. After the coatings were well prepared, the pineapple fruits were washed, with clean water, and then the coatings were applied to the fruits, air dried, packaged and then stored in a room with a temperature of 7oC and a 90-95% RH.
2.3. Observation Method
Observations were made on acidity/free acid content (as citric acid, a titration method with 0.1 N NaOH and phenolphthalein as an indicator), soluble solid [ºBrix (%) with an Atago MASTER-M], respiration rate[6], fruit weight loss, vitamin C (with the 2,6-dichloroindophenol titrimetric method of AOAC Method 967.21), internal browning (IB), and fruit coating [(analyzed with Scanning Electron Microscope (SEM)].
Respiration rate was analyzed, following the method of Cano-Reinoso et al. (2022) [6]. Measurement of CO₂ concentration was conducted in a sealed container with a capacity of 13 L using a CO2 detector HT-2000 Digital CO₂ meter (CO2 range: 0-9999 mg/kg, 10-99% RH, 0-50 °C; Dongguan Xintai Instrument; China). Before measuring CO₂, the fruit was weighed with a digital scale. After that the fruit was put into the container with a CO₂ meter and ensured that it was tightly closed. This measurement was carried out in the cold strage room of 7 ºC. Changes in CO₂ concentration were calculated for 1 hour on each fruit.
Analysis for vitamin C was carried out with the method of 2,6-dichloroindophenol titrimetric method (AOAC Method 967.21). In this titration, metaphosphoric acid was added to the sample preparation, thus preventing other metal catalysts from oxidizing vitamin C. The principle of analysis of vitamin C levels by 2,6-dichlorophenol titration method was to determine vitamin C levels in foodstuffs based on titration with 2,6-dichlorophenol indophenol where there was a reduction reaction of 2,6- dichlorophenol indophenol in the presence of vitamin C in an acid solution. Ascorbic acid reduced 2,6- dichlorophenol indophenol in a colorless solution. The end point of the titration was indicated by a color change to pink under acidic conditions [7].
Assessment of the internal browning was identified by changes in flesh color of the fruit wich were evaluated every 7-day until end of observation. Fleshcolor is determined using the color index on the pineapple. Internal browning of flesht is visually graded from 0 (normal), 1 (light), 2 (medium), and 3 (severe browning).
Microstructure of the pineapple coated surface was analysed using a Scanning Electron Microscope SEM (ZEISS/EVO MA 10; German). The SEM analysis was conducted in the Technical Implementation Unit of the Integrated Laboratory and the Center for Technological Innovation, University of Lampung, Indonesia. Rectangular pieces (5 mm3 × 5 mm3 × 2 mm3) of the coated pineapple obtained from the phloem tissue were cut for the observation the film-coated pineapple surface. A small piece of tissue in the middle of the flesh adjacent to the core was split with a tweezer. Before scanning, the slices were dehydrated with ethanol solutions and dried at a critical point of liquid CO2 with a desiccator. The samples were mounted onto aluminium specimen stubs using conductive silver glue and sputter-coated with gold.
3. Result and Discussion 3.1. Acidity
Based on the results of the analysis shown in Figures 1 and 2, it shows that the differences between the GP3 and Md2 clones have no different acidity levels (p-value >0,05), and the effect of different coating types does not affect the overall acidity level (p-value >0,05), the overall acidity value ranges from 0.6%. The level of acidity is not only influenced by varieties but can also be influenced by seasons and regions, during the summer the acidity can range from 0.3-0.4%. while in winter, acidity of up to 0.7% is acceptable for most consumers [8].
3.2. ºBrix
Figure 3 shows a significant difference (p-value <0,05) the level of sweetness of pineapple between the two clones, pineapple clone MD2 consistently shows a higher level of sweetness with a value of 16.4% compared to GP3 with a value of 13.9% until the end of the observation, while Figure 4 shows differences in coating type did not give a significant effect (p-value >0,05) on changes in the level of sweetness of the fruit until the end of the shelf life. This condition indicates that the MD2 clone does have a sweeter taste characteristic than GP3 which is a Smooth Cayenne cultivar[8].
3.3. Respiration rate
Based on the observations made (Figure 5), there was a significant difference (p-value <0,05) between respiration in MD2 (M) and GP3 (G) clones from day 0 to day 14, the condition then stabilized without a significant difference (p-value >0,05) from day 21 to day 35 of observation. While the coating treatment (Figure 6) did not show a significant effect on the respiration rate between treatments (p-value >0,05), this is because fruit storage at 7oC is the optimal temperature for pineapple storage so that the pineapple fruit respiration rate can be suppressed ranging from 1.3 to 4, 4 ml CO2/Kg.H-1 during storage at that temperature, while at 23oC the respiration of pineapple fruit was around 22 ml CO2/Kg.H-1 [3].
Figure 1. Effect of different pineapple clones ; MD2 (M) and GP3 (G) on the acidity level stored at 7oC temperature.
Each value is the mean of 25 replicates.
The vertical bars represent the standard error of the mean
Figure 2. Effect of different coating ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) on the acidity level stored at 7oC temperature.
Each value is the mean of 10 replicates.
The vertical bars represent the standard error of the mean
Figure 3. Effect of different pineapple clones ; MD2 (M) and GP3 (G) on the ºBrix level stored at 7ºC temperature.
Each value is the mean of 25 replicates.
The vertical bars represent the standard error of the mean
Figure 4. Effect of different coating ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) on the ºBrix level stored at 7 ºC temperature.
Each value is the mean of 10 replicates.
The vertical bars represent the standard error of the mean
Figure 5. Effect of different pineapple clones ; MD2 (M) and GP3 (G) on the respiration rate level stored at 7oC temperature.
Each value is the mean of 25 replicates.
The vertical bars represent the standard error of the mean
Figure 6. Effect of different coating; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) on the respitration rate level stored at 7oC temperature.
Each value is the mean of 10 replicates. The vertical bars represent the standard error of the mean
3.4. Weight loss
The weight loss between the two clones shown in Figure 7 shows that the MD2 (M) clone has a weight loss of 13.9% and this value is 2% significantly lower (p-value <0,05) than the GP3 (G) clone compared to the weight loss value of 15.9%. While Figure 8 shows that the use of Sta-Fresh 2952 (S) coating is more stable in suppressing the rate of weight loss starting from 3 weeks after storage until the end of the shelf life, which is 11.8% of the initial weight value compared to the use of other coatings and also treatment without coating. which has a greater weight loss value with a value of 14.9% to 17.4%. This value shows a significant difference with the effect of the treatment (p-value
<0,05).
Figure 7. Effect of different pineapple clones ; MD2 (M) and GP3 (G) on the weight loss level stored at 7oC temperature.
Each value is the mean of 25 replicates.
The vertical bars represent the standard error of the mean
Figure 8. Effect of different coating ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) on the weight loss level stored at 7oC temperature.
Each value is the mean of 10 replicates. The vertical bars represent the standard error of the mean
3.5. Vitamin C
The vitamin C/ascorbic acid content of the two clones was significantly different (p-value <0,05), as shown in Figures 9 and 11 which show the difference in Vitamin C content in the comparison of the two clone types and their combination with various types of coatings during the shelf life, indicating that the GP3 clone has ascorbic acid content of as much as 52ppm while the MD2 clone can reach
586ppm. The content of Vitamin C in the MD2 clone is also known to be higher than Smooth Cayenne [1]. The high content of ascorbic acid will affect the incidence of Internal Browning (IB). The incidence of IB will be lower if the ascorbic acid content is more than 500 ppm. Ascorbic acid content can change during the shelf life, changes in content can increase and decrease when stored at 8oC [9].
Figure 10 shows that different coating treatments can affect the content of Vitamin C in the fruit. The content of Vitamin C in the treatment without coating (K) showed the highest value which was significantly different (p-value <0,05) compared to the overall coating treatment.
Figure 9. Effect of different pineapple clones ; MD2 (M) and GP3 (G) on the Vit.C level stored at 7oC temperature.
Each value is the mean of 25 replicates.
The vertical bars represent the standard error of the mean
Figure 10. Effect of different coating ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) on the Vit.C level stored at 7oC temperature.
Each value is the mean of 10 replicates.
The vertical bars represent the standard error of the mean
Figure 11. Vitamin C/Ascorbic acid during shelf life ; Pineapple clones ; MD2 (M) and GP3 (G) combine with different coating materials ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K).
3.6. Internal Browning
Internal Browning (IB) symptoms are more susceptible to occur in pineapple clones GP3/Smooth Cayenne as shown in Figure 12-14. the appearance of IB in GP3 clone pineapples stored at 7oC began
to appear after 14 days of storage, while in MD2 clones only appeared on days 28 with a very minimal incidence rate, this value shows a significant difference (p-value <0,05). Pineapple which is susceptible to IB is also characterized by the low content of ascorbic acid in the fruit [1], ascorbic acid or vitamin C can also act as antioxidants. Antioxidants can prevent the initiation of browning by reacting with oxygen, so that with the high content of ascorbic acid, the potential for IB will be smaller.
While the various types of coatings shown in Figure 14 did not show different results (p-value >0,05) in terms of preventing the appearance of IB in the whole treatment.
Figure 12. Effect of different pineapple clones ; MD2 (M) and GP3 (G) on the IB level stored at 7oC temperature.
Each value is the mean of 25 replicates.
The vertical bars represent the standard error of the mean
Figure 13. Effect of different coating ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) on the IB level stored at 7oC temperature.
Each value is the mean of 10 replicates.
The vertical bars represent the standard error of the mean
MP MS MC MO MK
GP GS GC GO GK
Figure 14. Pineapple flesh condition after stored for 35 days ; Pineapple clones ; MD2 (M) and GP3 (G) combine with different coating materials ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K), All GP3 clones show IB with browning flesh color at the core
3.7. Scanning Electron Microscope
In order to study the homogeneity of the coating layer on the surface of the pineapple skin which is coated by several coating products, microscopic studies are carried out as shown in Figure 15. In the
image, the photo with the code MK and GK is the condition of the pineapple skin on both types of clones, GP3 and MD2 without giving a coating layer, from the appearance it can be seen that the skin of the pineapple without the addition of a coating layer looks more smooth without any layer covering the surface of the fruit skin. While the other picture shows the condition of the pineapple skin with several coatings consisting of Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K). The condition of coating with various types shows the density of coating particles on the surface of the fruit skin that covers the pores. In the marked picture, it can be seen that some parts are not completely covered by the coating, so the surface of the fruit skin is still visible. Each coating material has a characteristic appearance of a layer that is not the same as other materials, this can later affect water loss in the fruit as indicated by a reduction in weight loss. The presence of a coating layer acts as a barrier to the transpiration process so that it can reduce the high potential for evaporation.
MK MC MO
GK GC GO
GS MS MP
Figure 15. Display the results of various coating materials ; Pineapple clones ; MD2 (M) and GP3 (G) combine with different coating materials ; Palm stearin (P), Sta-Fresh2952 (S), Chitosan (C), OE6012 (O) and Control with out coating (K) at 200X display magnification using Scanning Electron Microscope
Table 1 is the result of various parameters measured at the end of the observation to see the effect of differences in clone and type of coating on the parameters observed during the shelf life. Parameters coded with the letters “M” and “G” represent the two types of clones used with each code representing 25 data each while the parameters coded with the letters “P”, “S”, “C”, “O ” and “K” represent the
type of coating material used with each code representing each of the 10 analysed data with a 95%
confidence interval.
Table 1. Influences of the treatments applied on the Brix, Acidity, Weight loss, Respiration, Vitamin C and Internal Browning at the end of shelf life.
**
Brix (%)
Acidity (%)
Weight loss (%)
Respiration (ml CO2/KgH-1)
Vitamin C (ppm)
IB (score)* M 16,4+0,7a 0,67+0,11a 13,9+1,4b 4,30+0,4a 586+51,7a 0,08+0,2b G 13,9+0,2b 0,62+0,06a 15,9+1,8a 4,47+0,2a 52+9,2b 2,36+0,1a P 15,2+0,7a 0,69+0,7a 17,4+1,8a 4,59+0,3a 318+32,8ab 1,3+0,7a S 15,6+0,8a 0,58+0,6a 11,8+1,8c 3,97+0,6a 296+19,1b 1,1+0,6a C 14,9+0,4a 0,67+0,7a 15,5+1,5ab 4,48+0,6a 314+38,7ab 1,3+0,7a O 14,8+0,9a 0,65+0,7a 15,1+1,2b 4,49+0,7a 314+31,2ab 1,3+0,5a K 15,4+0,8a 0,62+0,6a 14,9+1,6b 4,40+0,4a 353+30,6a 1,1+0,4a Note : * 0 (normal), 1 (light browning), 2 (medium browning), 3 (severe browning)
** M (MD2 Pineapple clone), G (GP3 Pineapple Clone)
P (Palm Stearin), S (Sta-Fresh2952), C (Chitosan), O (OE6012), K (Control without coating) Each value represents a mean ± standard error. Mean values in each column followed by the same lower-case letters are not statistically different by Duncan’s multiple range test.
4. Conclusions
From the comparison results of the 2 clones GP3 and MD2, it showed that the GP3 clone was more susceptible to Internal Browning (IB). The content of Vitamin C / ascorbic acid affected the occurrence rate of IB in the MD2 clone. In pineapple GP3 the content of ascorbic acid and ºBrix showed a much lower compared to MD2. The results of the study showed also that clone GP3 had a ºBrix value of 13.9% and ascorbic acid 52 ppm which was much lower than clone MD2 with a ºBrix value of 16.4%. and 586 ppm ascorbic acid. The incidence of IB in pineapple clone GP3 also began to appear on the 14th day after storage, while in MD2 it only appeared on day 28 with a very slight occurence. Based on these considerations, the GP3 clone was considered unsuitable as a fresh pineapple compared to the MD2 clone.
The use of various types of coatings to maintain the quality of pineapple fruit during the shelf life could not prevent the appearance of internal browning. The respiration process during the shelf life continued and the role of the coating to suppress the respiration rate did not show significantly different results because storage at a cold temperature of 7oC played a greater role in restraining the respiration rate of pineapple. However, the role of the coating was to minimize the occurrence of weight loss, especially the StaFresh 2952 coating which consistently reduced weight loss by 11.8% for up to 35 days of shelf life.
5. Acknowledgments
Special thanks are directed to the Director General of Higher Education, Research, and Technology, the Ministry Education, Culture, Research and Technology, the Republic of Indonesia for funding this research through the Postgraduate Research Grands of Magister Research Program of National Competency Research Grand 2022. The authors would like to thank the Research and Development Department of the Great Giant Pineapple Co. Ltd. Lampung, Indonesia for its much support during the research. Thanks are also to the Technical Implementation Unit of the Integrated Laboratory and the Center for Technological Innovation, University of Lampung, Indonesia for giving technical helps and permissions to carry out SEM analysis.
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