EFFECT OF PRETREATMENTS AND STORAGE TEMPERATURES ON PHYSICO-CHEMICAL AND FUNCTIONAL PROPERTIES OF CARROT POWDER

Abstract

Drying of vegetable after chemical pretreatment has long been an effective method of preservation. The objective of this study was to find out suitable pretreatment and storage temperature for cabinet dried carrot powder based on physico-chemical and functional properties. Drying process was carried out for carrot cubes (0.3-0.5cm) using four blanching (80±2ºC) pretreatments such as blanching with 1% calcium chloride (CaCl2), 0.2% potassium metabisulphite (KMS), 1% calcium chloride and 0.2% potassium metabisulphite (CaCl2+KMS) combination and pure water. An untreated sample was considered as control. Then all the pretreated samples were dried in cabinet dryer at 60±2ºC temperature for 18 hours and the dried samples were ground as powder. The entire obtained carrot powder sample were packed in low density polyethylene and stored at three storage temperatures such as ambient temperature (20±2ºC), refrigeration temperature (4±2ºC) and freezing temperature (-10±2ºC). The dried samples were analyzed for physico-chemical properties in terms of moisture, ash, fat, protein, fiber, beta-carotene and color and functional properties such as degree of caking, water absorption index, rehydration ratio, swelling capacity, bulk density and solubility at 0 day, 30 days and 60 days of storage. Results revealed that the moisture content of carrot powder treated with KMS and stored in freezing temperature was found to be lower than that of other pretreatments and storage temperatures. In case of fat, protein, ash, fiber and beta-carotene content, there were significant (at p≤0.001) effects of pretreatments and storage temperatures on carrot powder. Carrot powder treated with KMS and stored at freezing temperature was recorded to have better nutritional composition in terms of protein, fiber and betacarotene compared to that of other pretreatments and storage temperatures. On the other hand, all the functional properties of carrot powder were showed to be significantly (at p≤0.001) different due to different pretreatments and storage temperatures. Sample treated with KMS and stored at freezing temperature was reported to show better functional properties than that of other pretreatments and storage temperatures. The overall results indicated that physico-chemical and functional properties of cabinet dried carrot powder can be maintained well if the sample is treated with 0.2% KMS before drying and stored at freezing temperature.