The experiments were conducting in the Postharvest Technology Division of Bangladesh Agricultural Research Institute, Gazipur in the year of 2014-2015. Good quality ginger rhizomes (BARI ginger-1) were collected form Spices Research Centre and used in this study. The ginger rhizomes were broken into pieces to expose the crevices and then washed in running water to remove the adhering mud. Again the cleaned rhizomes were scraped with a knife to remove dirt as well as spoiled portion. The ginger rhizomes were peeled cut and make paste using grinder then hold at room temperature for 1 hr in covered container to facilitate enzymatic action for flavor and colour development. The pastes were treated with 0%, 3%, 6%, 9%, and 12% common salt and added citric acid 0.4%. The paste to come down the PH level around 4.0. The paste were thermally processed at 1000C for 20 min in water bath and poured immediately in glass bottle, plastic container and aluminum foil package according to the treatments used in this study. Then, the paste with containers was stored at room temperature (25-300C). The physicochemical parameters and microbial test were carried out to examine the quality of the products were studied during storage.
Treatments
T1,T4,T7,T10 and T13 =ginger paste in glass container in 0%, 3%,6%,9%,12% salt ratio, respectively
T2,T5,T8,T11 and T14 = ginger paste in plastic container in 0%, 3%,6%,9%,12% salt ratio, respectively
T3,T6,T9,T12 and T15 = ginger paste in aluminum foil packet in 0%, 3%,6%,9%,12% salt ratio, respectively
Measurement of titratable acidity, PH and total soluble solids (TSS): Titratable acidity in the processed paste was measured in terms of citric acid following the method described by Wang e t al. (1995). For measuring titratable acidity, 5 g paste were diluted with 95 mL distilled water making the volume to 100 mL, then filtered through Whatman no. 41 filter paper and titrated against 0.1 N NaOH to PH 8.1 using phenolphthalein indicator. Acidity was expressed as percent citric acid by weight. The paste sample (5 g) was diluted with 45 mL distilled water, and PH was measured with glass electrode (EUTECH Instruments, Selangor, Malaysia). Sodium chloride was determined by titration with silver nitrate (Ranganna, 1986). Total soluble solids (°Brix) were determined with a digital bench top Abbe Refractometer at 200C (Atago Co., Ltd., Tokyo, Japan). To determine the total soluble solids, the paste was dried under vacuum at 700C to constant weight. The dried samples were allowed to cool in desiccators for 30 min and then weighed (AOAC, 1995). Total solids (%) = (mass of dried sample mass/mass of fresh sample) ×100. Enumeration of coliforms, mesophilic aerobes and yeasts and molds were done by pour plate and spread plate method following the procedure of the International Commission on Microbiological Specifications (ICMSF, 1992). Violet red bile agar for coliform bacteria, plate count agar (PCA) for mesophilic aerobes and potato dextrose agar (PDA) for yeast and molds procured from Himedia, India were used. Ten grams of ginger garlic paste sample were weighed in duplicates into 90 mL of 0.1% peptone water aseptically, homogenized and serial dilution was carried out. One milliliter of the appropriate dilution of the sample was taken in sterile Petri plates and 15 mL of respective agar maintained at 45C were poured into plates and allowed to solidify. Set plates were incubated at 37C for 48 h and colony count was taken after 24–48 h of incubation for bacteria. The potato dextrose plates for yeasts and molds were incubated at 27C for 3–4 days and colony count was recorded. All tests were carried out in duplicate and the average mean values are reported.
Statistical Analysis: Statistical analysis of the data obtained for each treatment was carried out by analysis of variance followed by Duncan’s new multiple range test (Duncan, 1955) to found out differences between treatments at the probability level of P <0.05.