Drying Process Optimization and Modelling the Drying Kinetics and Quality Attributes of Dried Chili Pepper (Capsicum frutescens L.)

Abstract

This study is important in terms of the fact that the production of a dried product with good quality and minimum process drying cost is dependent on individual or combinations of several drying conditions. However, if drying is not properly conducted at favourable drying conditions, it generates product quality-related problems for the consumer and food market. Thus, this study focused on the optimization and evaluation of the main and interactive effects of drying air temperature (DAT), air velocity (DAV), relative humidity (RH), and drying time (DRT) on the cabinet-tray hot air drying and quality attributes of chili pepper using the four-factors-five-level-rotatable central composite experimental design of response surface methodology. The drying kinetics was also modeled using known empirical drying models (Page, Newton, Logarithmic, and Henderson and Pabis). The drying conditions utilized are DAV (0 - 2 m/s), RH (60 - 80 %), DAT (40 - 80 °C), and DRT (180 - 900 min), while the moisture content (MC), carbohydrate content (CHC), total plate count (TPLC), and protein content (PTC) were the considered product quality attributes. The results showed that the most significant drying process conditions that exerted a more pronounced main and interactive effects on the dried chili pepper quality attributes are drying process time and drying air temperature. Second-order quadratic regression model adequately predicted the quality attributes of the dried chili pepper. The optimum process conditions for the production of dried chili pepper with minimum MC (9.93 %) and TPLC (40.10 CFU/g) as well as maximum PTC (7.88 %) and CHC (24.66 %) were obtained to be DAT, 61.59 °C, DAV, 0.70 m/s, RH, 68.39. %, and DRT, 729.63 min. The Page model best describe the drying kinetics. The drying treatments generally retained the protein and carbohydrate contents (nutritional properties) in the dried chili pepper product as well as reduced the microbial load to the acceptable limit allowed for consumption. HIGHLIGHTS Effects of drying conditions on dried chili pepper quality attributes were evaluated using response surface method (RSM) Dried chili pepper quality attributes were optimized using RSM Drying conditions retained the quality attributes of dried chili pepper Microbial load of dried chili pepper was within the acceptable limit for consumption A mathematical model was developed for the dried chili pepper quality attributes’ prediction GRAPHICAL ABSTRACT