International Journal of Horticulture, 2024, Vol.14, No.5, 310-318 http://hortherbpublisher.com/index.php/ijh 312 2.3 Determination of moisture content, total soluble solids and pH value The initial moisture content of the pepper samples was determined using the AOAC (2000) method. A dish was pre-dried at 130 °C for one hour and was transferred into a desiccator for about 15-20 minutes. The weight of the aluminum tin was measured. About 2.0-3.0 g of the sample was weighed into the aluminum tin, and the sample was dried at 130 °C for 6 hours. The total soluble solids (TSS) level of the hot pepper was determined according to the AOAC (2000) method by using a hand refractometer at room temperature (ranged from 18 °C to 23 °C). The pH value of hot pepper powder was determined according to Choi and Lee (2017). About 45 mL of distilled water was added to 5.0 g of hot pepper powder and homogenized for 1 min. The solution was kept for 1hr at ambient temperature, and the pH value of the supernatant was measured using digital pH meter. 2.4 Powder bulk density The bulk density of the red pepper powder was measured by a funnel method according to Narayana and Rao (1984). About 10.0 g of pepper powder was weighed into a 100 mL graduated cylinder and then gently dropped 10 times onto a rubber mat from a height of 15 cm. The volume of powder occupied in the measuring cylinder was recorded. The bulk density was calculated as follows: pb= mp Vp Where, ρb is bulk density (g/cm3), mp is the mass of the powder (g), and Vp is the volume of the powder (cm3). 2.5 Browning index The browning index was estimated according to the procedure described by Supapvanich et al. (2011). About 5.0 g of pepper powder was measured and placed in a beaker. Then, 100 mL 65% (v/v) ethanol was added. The mixture was stirred at room temperature for 1 h. The extract was filtered using Whatman No. 1 filter paper. Absorbance at 420 nm was taken using UV–visible spectrophotometer. The result was expressed as the mean of the three replications of the absorbance. 2.6 Oleoresin determination Oleoresin was determined according to Raquel and Matiachevich (2017). The extraction was carried out using the paste (400 g in total) was mixed with hexane in a ratio of 1:2 (pepper powder: solvent) in weight, keeping the mixture at 25 °C during 20 hours at constant stirring in an incubator. Then, the mixture was vacuum filtered with Whatman No.1 filter paper to separate the residues of the extract and the solvent was evaporated and recovered using rotavapor at 40 °C (at this temperature, the compounds were not degraded. 2.7 Total carotenoids Total carotenoids were determined spectrophotometrically using the method described in (Rodriguez-Amaya and Kimura, 2004). About 5.0 g of samples were weighed and ground with 40 mL of cold acetone using a mortar and pestle until the residue became colorless. Sample residue was filtered under a vacuum-filtered pump using a Buchner funnel. The extract was partitioned with 60 mL of petroleum ether; then each fraction was washed three times with 200 mL of distilled water in each cycle for complete removal of acetone. The extracts were collected in a 50 mL volumetric flask using sodium sulphate to trap remaining water and acetone in the crude extract. When the collected extract did not reach the mark point of 50 mL volumetric flask, it made up to a volume of 50 mL by adding petroleum ether. All the procedures were performed in dim light. The absorbance of extracted carotenoids was taken at 452 nm using a UV spectrophotometer. The total carotenoids was calculated as follows: Total Carotenoid (µg/g)= [A × volume (mL) × 104] [A1cm1% × sample weight (g)] Where, A = absorbance; volume = total volume of extract = 50 mL; A1cm1% =absorption coefficient of β-carotene in petroleum ether (2592).
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