EFFECT OF PRETREATMENT AND DRYING TEMPERATURE ON PHYSICOCHEMICAL PROPERTIES OF TOMATO POWDER

Abstract

This study was carried out with an objective of analyzing the effect of different chemical pretreatment and drying temperature on the physiochemical properties of tomato powder. The tomatoes were cut longitudinally into eight equal halves and pretreated with 0.2% KMS, 1% CaCl2, 7% NaCl in distilled water for 10 minutes and untreated (control). These tomato slices were dried in a cabinet dryer in different temperature (55, 60, 65ºC) to equal moisture content and flakes were grounded in a blender to obtain tomato powder whose chemical analysis (Total phenolic content, DPPH radical scavenging activity, lycopene and vitamin C) and physical analysis (bulk density, true density, porosity and solubility) were carried out. The obtained data was analyzed statistically by two way of ANOVA at 5% level of significance. Lycopene, total phenolic content, vitamin C and DPPH radical scavenging activity were found to be significantly affected (p<0.05) by different chemical pretreatment in all the drying temperature. KMS treatment combined with drying temperature of 60ºC was most effective method for retaining total phenolic content and DPPH radical scavenging activity whereas same treatment and drying temperature of 55ºC retain the maximum amount of lycopene and vitamin C, resulting the value of 713.3 mg GAE/100g db total phenolic content, 57.26% DPPH radical scavenging activity, 6.117 mg/100 g db lycopene and 18.78 mg /100g db vitamin C. Most of the samples were significantly different (P <0.05) at 5% level of significance. In case of physical properties, bulk density and true density were found to be maximum in Control sample dried at 65ºC having the value 0.675 g/ml and 1.354 g/ml respectively whereas porosity and solubility were found to be maximum in KMS treated sample dried at 55ºC having the value 0.527 and 19.73 % respectively. Statistical analysis showed a significant difference (P<0.05) at 5% level of significance across all physical properties. Hence, these findings show that drying temperature and chemical pretreatment are important in maintaining the quality of the dried tomato powder.