The experiment was conducted at the laboratory of Postharvest Technology Section, Horticulture Research Centre, Bangladesh Agricultural Research Institute, Gazipur during May 2018. Bitter gourd slices were selected and taken for applying different additives recommended as a food additive for producing minimally processed ready to cook vegetable products for the study. The treatments were as follows:
T1 = 0.5 % Ascorbic acid, T2 = 0.5 % Citric acid, T3 = 0.5 % Calcium Chloride (CaCl2), T4 = Wash with normal water, T5 = Control (without any wash), The design of the experiment was CRD with three replications.
Material: Bitter gourd obtained from a wholesale market was used for this study. Fruits were sorted to eliminate damaged, deformed or defective fruits.
Preparation of ready-to-cook bitter gourd: The whole fruit was washed with clean normal water and sliced into desirable pieces with a sharp stainless steel knife (sterilized in ethanol).To minimize product heterogeneity, slices were mixed and subsequently divided into five equal parts. The first part was dipped in ascorbic acid solution; the second portion in citric acid solution, the third portion in calcium chloride solution, the fourth portion in normal water and the fifth portion was used as a control (without any wash) sample. Dipping treatments with solutions of ascorbic acid (BDH chemicals Ltd, Poole, England), citric acid (Merck, Germany) and calcium chloride (UNI-CHEM, Germany) were applied separately for 3 minutes, after draining, dried in normal air and packed in polypropylene (pp) box with cling wrap. The packets were stored in the normal refrigerator at 4±10C. All dipping solutions were made with distilled water and the concentrations were 0.5% (w/v) in all cases.
Color of bitter gourd slices: The color of vegetable slices was measured with Chroma Meter (model CR-400/410). Five slices of bitter gourd per replication were evaluated from each treatment.
Biochemical traits: Data on bio-chemical traits were determined on the initial day and the day of every three days after storage. The total acidity (%) and vitamin C (mg/100g) were determined according to AOAC (1994). Sensory evaluation: Ten panelists were selected for sensory evaluation. The panelists were directed, prior to the test, to the actual descriptive levels used to evaluate the color, flavor, freshness, marketability, consumer preference, total acceptance and cooking performance of the bitter gourd slices. The acceptability was evaluated based on a 9-point Hedonic scale. The higher the point was, the better the overall sensory quality was (9=like extremely, 8=like very much, 7=like moderate, 6= like slightly, 5= neither like nor dislike, 4= dislike slightly, 3=dislike moderate, 2=dislike very much, 1=dislike extremely). Physiological losses in weight (%) and quality traits like freshness, marketability, consumer preference, cooking performance; chemical changes (% total acidity, Vitamin C) and sensory evaluation were considered during storage time.
Statistical analysis: Analysis of variance was done by one way ANOVA procedures of MSTAT-C software (Statistical package developed by the Crop and Soil Sciences Department of Michigan State University, USA). Comparisons among the samples were done by Duncan’s Multiple Range Test (DMRT).