MA Rahman
Horticulture Research Centre, BARI, Joydebpur, Gazipur-1701, Bangladesh.
MN Islam
Horticulture Research Centre, BARI, Joydebpur, Gazipur-1701, Bangladesh.
TAA Nasrin
Horticulture Research Centre, BARI, Joydebpur, Gazipur-1701, Bangladesh.
MM Begum
Tuber Crop Research Centre, BARI, Joydebpur, Gazipur-1701, Bangladesh
Tomato, Differential Absorbance, Maturity Index, Fruit Firmness, Skin Colour, Chlorophyll Contents, Postharvest
Horticulture Research Centre, Bangladesh Agriculture Research Institute (BARI), Gazipur, Bangladesh
Postharvest and Agro-processing
A popular commercial summer tomato variety cv. BARI Tomato-8 grown at the research field of Horticulture Research Centre, Bangladesh Agriculture Research Institute (BARI), Gazipur, Bangladesh was used in this experiment. Flowers were tagged on first day of fruit set to determine the stage of fruit development. Tomatoes were harvested at every alternate day started on 21 days after fruit set (DAFS) until 31 DAFS. Flowers were tagged on first day of fruit set to determine the stage of fruit development. Sixty randomly selected tagged fruits from different plants were harvested at each alternate day started on 21 days after fruit set (DAFS) until 31 DAFS to determine their physicochemical properties like tissue firmness, external colour, chlorophyll index using DA meter, TSS, ascorbic acid content and pH. Surface colour of tomato was measured with a Chroma Meter (Model CR-400, Minolta Corp., Japan). CIE L*a*b* coordinates were recorded using D65 illuminants and a 10° Standard Observer as a reference system. L* is lightness, a* (-greenness to +redness) and b* (-blueness to +yellowness) are the chromaticity coordinates. The a* and b* values were converted to chroma [C = (a*2 + b*2)1/2] and hue angle [h = tan-1 (b*/a*)]. Before measurement, the equipment was calibrated against a standard white tile. Skin colour was measured at two opposite middle positions on the fruit surface using 20 fruits replicated thrice at each sampling period. Firmness analysis was performed using both destructive method using Fruit Texture Analyzer (GUSS, Model No. GS25, SA supported by FTA Win Software) and a non-destructive firmness tester (53215 Fruit Hardness Tester, T.R. Turoni, Italy). With fruit texture analyzer, firmness measurement was taken as the maximum penetration force reached during the tissue breakage and determined with 8 mm diameter stainless steel flathead probe, which penetrates in a normal direction at a cross-head speed of 5 mm s-1. After establishing zero-force contact between the probe and the horizontally positioned fruit, specimens were compressed 3 mm at two equidistant points along with the equatorial region of each fruit. The maximum force generated during probe travel was used for data analysis. Results were expressed in Newton (N). In case of non-destructive method, fruit samples were horizontally placed under the firmness tester and pressed the probe for a moment. Data were taken from two equidistant points of each fruit and expressed in shore. Twenty tomato fruits replicated thrice were used at each sampling time for measuring the tissue firmness in each method. Measurement of absorbance difference index (IAD) In this experiment, difference of absorbance index of tomato fruit was measured using DA Meter (tr DA Meter, T.R. Turoni, Italy). Fruits were harvested at every alternate day started on 21 DAFS and finished on 31 DAFS, from a preoptimum maturity stage until fruit were of red ripe stage of maturity. At each sampling period, DA readings were measured on both cheeks of 20 fruit, replicated 3 times. DA readings were correlated with chlorophyll content, TSS, titratable acidity, pH and vitamin C content as well as with non-destructive measurements of surface color using a colorimeter and firmness using a hardness tester. Measurements of ascorbic acid, titratable acidity (TA), total soluble solids (TSS) and pH Ascorbic acid content was estimated by 2,6- dichlorophenolindophenol titration following the method by Ranganna (1986), and results were expressed as mg 100 g-1 fresh weight. 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 (1986). The total soluble solids and pH of the juice were determined by using hand-held refractometer (Model N-1E, Brix 0-32%, Atago, Japan, brix range 0-30% at 20° C) and glass electrode pH meter (Microprocessor pH meter, Hanna Instruments), respectively. Measurement of chlorophyll content using acetone method The thin pericarp of the tomato was cut into small pieces with a sharp knife and put 2 g of fresh tissue into a mortar. Crush the tissue thoroughly with a pestle. Acetone (80%) was added to allow the tissue to be thoroughly homogenized. Then the supernatant was decanted through a filter paper into a 100 ml volumetric flask. The extraction procedure was repeated by adding 80% acetone to the mortar. Finally, the volume was made up to 100 ml with 80 % acetone and measures the chlorophyll content using spectrophotometer (T80 UV/VIS Spectrophotometer, PG Instrument Ltd.) at 645 and 663 nm (Whitam et al., 1986). Final result in chlorophyll contents were expressed in µg g-1. Chlorophyll content (mg g-1) was calculated using the following formula: Chlorophyll (a+b) = [20.2 (OD645) + 8.02 (OD663)] x V/1000W Where, V= Final volume (ml) of acetone-chlorophyll extract W= Fresh weight (g) of plant sample Statistical analysis The data were subjected to analysis of variance (ANOVA) using the ‘R Statistical Software version 3.1.2. The results showing significant differences were then subjected to mean separation using LSD test at P < 0.05.
Int. J. Agril. Res. Innov. Tech. 9(2): 42-50, December 2019
Journal