Novel determination of green life based on image processing data of Cavendish banana after receiving post-harvest treatments

Conventional methods used in determining green-life are still relatively difficult to use because they are subjective. The initial phase shift from green to yellowish-green as the end of green-life is very difficult to detect and quantify with naked eyes. Therefore, we need a standard method that can be used to determine its green-life. The purpose of this study was to test a new method for determining the green-life based on image processing data of Cavendish banana after receiving post-harvest treatments. The data were collected from Cavendish banana at various maturity levels which had received post-harvest treatments of fruit coatings and storage temperatures. The results showed that the intensity of red (I-Red) as a component of the yellow colour has increased, while the intensity of green (I-Green) has decreased until the end of the observation. Green life ended when I-Red showed a greater value than I-Green. Cavendish banana in cold temperature storage showed a longer green life than room temperature storage with an average of 17.83 days and the longest was 35 days. Meanwhile, storage at room temperature showed an average green life length of 13.25 days with the longest period was 16 days.


Introduction
The length of the green-life period is an important parameter in the export of Cavendish banana.The importer countries receive tropical banana in its green life with plastic wrapping and paperbox packing during two weeks shipment process [1].Conventional methods used in determining green-life are still relatively difficult to be standardized because they are subjective.Colour parameter identification is the first thing to identify the maturity of banana [2].The maturity stage of banana is determined using rind colour stage with 7 stages (stage 1 is green, stage 2 is yellowish green, stage 3 is greenish yellow, stage 4 is yellow with green tip and stalk, stage 5 is yellow with green tip and yellow stalk, stage 6 is yellow with developing abscission layer at stalk, and stage 7 is yellow with brown spots [3].The initial phase shift from green to yellowish-green as the end of green-life is very difficult to detect and quantify with 1230 (2023) 012077 IOP Publishing doi:10.1088/1755-1315/1230/1/012077 2 naked eyes.Therefore, we need a standard method that can be used to determine its green-life objectively.
Green life is critical phase of Cavendish banana shelf life.Green life of banana means distance between green at harvesting to slightly yellow colour that indicates the climacteric crisis and the decreasing of green pigment [4].After Cavendish banana has passed its green life, the ripening process will take place very quickly and it is difficult to control.Therefore, a standard method is needed to determine the accuracy of the green life period.A digital image is a collection of colour pixels resulting from defining the x and y coordinates with the function f (x,y) and the amplitude f in each pair of coordinates of an image [5].Image Processing is an implementation of images by using computational transformations, the transformations are around the sharpening, contrast, and other required parameters to extract some usefull informations [6].Banana colour according to the colour stage is around green, yellow and brown which are composed by red and green colour whereas blue colour does not play a role within.A Red Green Blue (RGB) colour is the primary colour that can produce secondary colour like yellow, brown, etc.A RGB colour is one of the results of image processing that can be used for determining the green life of banana by comparing the red and green intensities of Cavendish banana image.The further stage of banana denotes secondary colour that is dominated by red colour donor as a result of the decreasing green pigment.The end of banana green life period is indicated when the composition of red is higher then green.The purpose of this study was to develop a new method for determining the green-life based on image processing data of Cavendish banana after receiving postharvest treatments.

Material and method
The data were collected from 24 Cavendish banana at various maturity levels and 3 replications which had received postharvest treatments of fruit coatings (non-coating/control, 1% chitosan, GA3 150 ppm, 1% chitosan + GA3 150 ppm mix that were applied on the fruit rind tip and base) and storage temperatures (room temperature [27 ± 1 o C] and cold temperature [16 ± 1 o C]).The image collection was the object that was analyzed by image processing methods to extract the information of RGB colour intensity (Figure 1).The research was conducted at the Laboratory of Horticulture and Postharvest, Department of Agronomy and Horticulture, Faculty of Agriculture, University of Lampung, Bandar Lampung, Indonesia during July to September 2022.

Image capturing
The image data were captured using an 8 MP digital camera (Infinix X6812B) with a 15 watts LED lamp as an illumination source from a distance of 30 cm above the sample (Figure 2).A sample was laid on a white-off paper in visible box.RGB colour intensities of the images were extracted using the Matlab program.This step was done everyday during maximum of 35 days.

A.
B.

RGB colour segmentation
Colour segmentation of the original image was analyzed by using vector method to calculate the gradient and form a composite gradient image of RGB components in the image [5].The difference gradients between object image and background were shown in final mask image.The object image (Cavendish banana) as the observation was clearly separated with the background.The fit values of RGB components at the coordinates (x,y) was added and scaled.The 1 value was the region of banana and the 0 value was the region of background.The colour of Cavendish banana was formed by RGB colour with trichromatic coefficient, defined as R+G+B=1.The thresholding result image was then carried out to masked image processing and it was divided into three primary colours, red, green, and blue components to extract the colour intensity informations as I-Red, I-Green and I-Blue.Region of Interest (ROI) area determination of sample was needed case by case, in this research the ROI area was set 30% part of the sample full shape to representative the whole fruit (Figure 3).

The data collection
The output data of image processing was in the form of txt format that contained mean and deviation standard of RGB colour intensities.Furthermore, there were also the information of pixel amount and ROI/object percentage.The data collection was done by collecting and exporting the required mean values of RBG colour intensities to Microsoft Excel.The required data such as mean and standard deviation of Red and Green colour intensities were exported to Microsoft Excel for the green life determination.

Result and discussion
After the data of RGB colour intensities were collected and exported to Microsoft Excel, determination of green life was done by marking cells where the intensity of red value (I-Red) is higher than intensity of green value (I-Green).It was the end of green life period of Cavendish banana samples.In this study, the intensity of blue was not used as a determinant because blue is not one of constituents of green and yellow in Cavendish banana.The intensity of blue value (I-Blue) on Cavendish banana rind colour showed random value which could not be defined.In the Figure 5, as it seen that blue does not form green or yellow.Blue band histogram of RGB colour in banana was not recommended to be a determinant due to its overlapping distribution [8].

Figure 5. RGB Colour Model
According to Table 1 and 2, cold temperature storage showed lengthen green life than in room temperature storage with average of 26.33 days and the longest was 35 days (see footnote under Table 1).Meanwhile, the average of green life in room temperature storage was 14.25 days and the longest time was 16 days (see footnote under Table 2).Cavendish banana could last up to 30 days of its green life period in cold storage at 10 o C.Meanwhile, at 25 o C, the green life of Cavendish banana occured descreasing as much a week [4].Hence, the determination method is logically reasonable.Length of the green life can also be caused by other influences such as environmental and physiological influences.As a climacteric fruit, Cavendish banana has a high response to exposed ethylene that causes shorten its green life.Ethylene will be induced in water stress condition of storage [9].The older maturity level of harvesting causes reduction of green life length which is called preclimacteric phase [10].
Table 1.The end of green life by marking cell where I-Red >I-Green (Cold Temp.) The days displayed are based on the determination of green life period of each sample only, the other days were still measured.but not displayed in this table.The maximum length of shelf life of the observation was 35 days.The average of green life period of cold storage was 17.83 days (x̄ = {sum of observations}/{total number of observations} = 316/12 = 26.33 days).As an illustration, red-lined box means the longest green life of Cavendish banana in cold temperature.Table 2.The end of green life by marking cell where I-Red >I-Green (Room Temp.) The days displayed are based on the determination of green life period of each sample only, the other days were still measured.but not displayed in this table.The maximum length of shelf life of the observation was 35 days.The average of green life period of cold storage was 17.83 days (x̄ = {sum of observations}/{total number of observations} = 171/12 = 14.25 days).As an illustration, red-lined box means the longest green life of Cavendish banana in room temperature.
Figure 6 showed an increasing trend of I-Red and decreasing of I-Green until the end of the shelf life of Cavendish banana.The value of redness in green to red parameter (*a) in banana increased during storage period due to the green pigment breakdown [11].A correlation between the increasing of red colour and higher stages of banana due to chlorophyll reduction [12].The end of the green life period can be determined by the I-Red which is higher than the I-Green.In physicochemical during maturation and ripening, a colour changes usually occur in fruits.According to the Figure 6, the yellow dot indicated the day when green life of Cavendish banana sample ended.Cavendish banana will show a climacteric peak and response to ethylene after it arrived and received ethylene gassing in the export destination, or when the green life period has passed [13].When Cavendish banana reach this point, I-Green will no longer exceed I-Red until the end of its shelf life.

A.
B. Prediction on the maturity and ripeness stages in banana, lately done by colour analysis and supported by high level of accuracy, which is equal to 94-98% [11].High prediction accuracy which is higher than 95% in his research on the colour values of three maturity levels of banana [3].Determination method of green life based on image processing in Cavendish banana is a non-destructive, simple and economically affordable way that can facilitate banana farmers in determining post-harvest handling  steps, avoiding large losses and speeding up the sorting process.A conventional determination method using colour-metric technique takes a long time and is very subjective, and it needs uniformity of samples [14].In this determination method, it is necessary to make observation be conducted at the same time at least once a day, because colour change can occur very quickly.

Conclusion
The value of red intensity (I-Red) and green intensity (I-Green) of Cavendish banana rind colour can be used to determine its green life period.The end of green life is marked by I-Red value which is higher than I-Green value.The implementation of this method in future work will objectively, nondestructively and efficiently useful for banana farmers to facilitate target market segmentation.
According to this proposed method, Cavendish banana in cold temperature storage showed a longer green life than room temperature storage with an average of 26.33 days and the longest was 35 days.
Meanwhile, storage at room temperature showed an average green life length of 14.25 days with the longest period was 16 days.

Figure 2 .
Figure 2. The illustration of image capturing in the visible box (A) and the image result (B).

Figure 3 .
Figure 3.The illustration of colour segmentation.

Figure 4 .
Figure 4.The illustration of rind colour histogram.

Figure 6 .
Figure 6.Selected samples of colour intensity of Cavendish banana.(A) Non-coated sample in cold temperature and (B) GA3 coated sample in room temperature.