Pineapple fruits (Ananas comosus cv. Honey Queen) (at about matured stages 3) were selected on the basis of the uniformity of the color and size from a commercial grower in Naniarchar, Rangamati hill district, Bangladesh. The stage of ripeness was determined by visual assessment of the shell. The scale ranges from 0 to 5: 0, all eyes were totally green; 1, < 20% of the eyes were predominantly yellow; 2, 20 to 40% of the eyes were tinged with yellow; 3, up to 65% of the eyes were predominantly yellow; 4, 65 to 90% of the eyes were fully yellow; 5, > 90% of the eyes were fully yellow and not more than 20% of the eyes were reddish orange. All fruits were cleaned and soaked in 0.05% (w/v) Iprodione solution (Rovral, FMG, Auto Crop Care Ltd, Bangladesh) for 2 min to eliminate potential microbes. Afterwards, the treated fruits were divided into ten groups; each group (10 fruits) was placed in a clean plastic box. The fruits of one group were dipped in water (as control). The fruits of nine groups were treated with Sta-Fresh 2952 (FMC) wax solution at 30, 60 and 90 g/l. After being air dried, the samples were placed in polyethylene bags (0.04 mm), stored at 9, 11 and 13°C and at 88±2% relative humidity (RH) for 21 day and transferred to 25°C for 3 day to simulate shelf conditions for chilling injury and quality evaluation. Five fruits from each box were randomly sampled to determine quality characteristics of fruits after storage periods and then the optimal treatment condition was chosen. Ninety (90) fruits were treated with the optimal treatment and 90 fruits were dipped in water (as control). All fruits were stored at 9, 11 and 13°C and some samples were taken at intervals. After 21 day storage at 88±2% RH, the residual samples were transferred to room temperature (25 - 28°C) for three days storage. Five fruits from each box were randomly sampled every 7 days in cold storage and each day in room temperature (25 - 28°C) storage to determine physical and biochemical changes during storage periods. The treatment combinations were as follows:
T1= Sta-Fresh 2952 coating@ 30 g/l + 90C storage temperature
T2= Sta-Fresh 2952 coating@ 30 g/l + 110C storage temperature
T3=Sta-Fresh 2952 coating@ 30 g/l + 130C storage temperature
T4= Sta-Fresh 2952 coating@ 60 g/l + 90C storage temperature
T5= Sta-Fresh 2952 coating@ 60 g/l + 110C storage temperature
T6= Sta-Fresh 2952 coating@ 60 g/l + 130C storage temperature
T7= Sta-Fresh 2952 coating@ 90 g/l + 90C storage temperature
T8= Sta-Fresh 2952 coating@ 90 g/l +110C storage temperature
T9= Sta-Fresh 2952 coating@ 90 g/l +130C storage temperature
T10 =Control
Sugar content and titratable acidity: Sugar content was estimated by the method of Ranganna (1994) and titratable acidity expressed as citric acid (%) was determined by titration with 0.1 mol L-1 NaOH to pH 8.1 according to the method by Ranganna (1994).
Total soluble solid: Total soluble solid in the extracted juice of fruits was measured by a refractometer (ATAGO (Brix = 0 to 32%)) and the results were expressed as % Brix
Ascorbic acid: For ascorbic acid measurement, 10g pulp tissue was homogenized in 50mL of 3% cold metaphosphoric acid (HPO3) using a blender for 2 min and filtered through Whatman filter paper No. 2. The clear supernatant was collected for assaying ascorbic acid by 2, 6-dichlorophenolindophenol titration following the method of Ranganna (1994). Ten milliliters of aliquot was titrated with 0.1% 2, 6-dichlorophenolindophenol solution until the filtrate changed to pink colour persisted for at least 15 seconds and the titration volume of 2, 6-dichlorophenolindophenol was recorded. Prior to titration 2, 6-dichlorophenolindophenol solution was calibrated by ascorbic acid standard solution. Ascorbic acid content was calculated according to the titration volume of 2, 6-dichlorophenolindophenol and results were expressed as mg 100g-1 fresh weight.
Experimental design and statistical analysis: The experiment was carried out in a Completely Randomized Design (CRD) with three replications. The data were subjected to analysis of variance (ANOVA) using the R Statistical Software version R i386 3.1.2. The results showing significant differences were then subjected to mean separation using Least Significant Difference (LSD) multiple range test at P<0.05.