Effect of Microwave oven Drying on some Nutritional and Anti-nutritional Content of Pretreated Paw-paw (Carica Papaya) Pulp Using Response Surface Methodology

Abstract

This study was conducted to investigate the effect of pretreatment and microwave oven drying on the nutritional and anti-nutritional content of Paw-paw (Carica papaya) pulp using response surface methodology (RSM). The response surface method used had 3 factors at 2 levels with full factorial central composite design used for the design matrix. The independent variables(factors) were Blanching Time (BTime), Ultrasound Time (UTime) and Ultrasound Energy (UEnergy). The Pawpaw fruit (Carica papaya) samples were purchased from Itam Market, Uyo, Akwa Ibom State, Nigeria. The samples were washed with clean water thoroughly removing all dirts and placed on a flat clean kitchen plastic tray and peeled vertically. After peeling, the pawpaw fruit was sliced into two halves vertically to enable the removal of dark brown seeds. The sample were then cut into 4mm to 6mm.thickness and 5mm x 6mm size in preparation for pretreatment and microwave oven drying. The thickness was 3mm. The pretreatment followed the outlined design matrix and thereafter was dried in a microwave oven. The drying temperature for Microwave Oven was 60⁰C and pretreatment blanching temperature was 90⁰C. The pawpaw slices were dried and monitored for every 30minutes till the moisture content was at equilibrium with the environment. The average  sample weight for each of the 15 (fifteen) experimental runs were 50g. The response variable considered in the study were nutrient - Vitamin-C, Carotene; Minerals; Iron, Potassium and Anti-nutrients- Phytate and Oxalate content of the pulp. It was observed that the fresh paw-paw pulp had the following composition: Vitamin-C; 105mg/ml; Carotene; 43.90mg/ml, Iron; 0.36mg/ml, Potassium; 167mg/ml, Phytate; 0.95mg/ml and Oxalate; 0.38mg/ml. The dried pretreated paw-paw pulp had the following nutritional and anti-nutritional composition; Vitamin-C; a range of 112.73mg/ml to 118.12mg/ml, Carotene; a range of 50.28 to 50.45mg/ml, Iron; a range of 0.48mg/ml to 0.61mg/ml, Potassium; a range of 177.75mg/ml to 183.27mg/ml, Oxalate; a range of 0.27mg/ml to 0.53mg/ml and Phytate; a range of 0.89mg/ml to 1.31mg/ml. It was observed that the dried samples nutrient and anti-nutrients content increased as compared to the fresh samples.