Drying kinetics, behavior, quality evaluation and monitoring of desiccated coconut using single and hybrid drying modes

Drying desiccated coconut has always been a topic in searching for better drying methods that are technically and economically feasible. While convective drying (CD) uses hot air as a heat source to dry a product, infrared drying (IR), a recently developed method, uses radiant energy without the need for a medium. However, applying IR drying to desiccated coconut has yet to be investigated. Moreover, the potential of using both drying methods (IR and CD) as hybrid drying on desiccated coconut has yet to be explored. The evaluation and monitoring of desiccated coconut quality throughout the drying process is also lacking. This research aimed to investigate further the drying kinetics and mathematical model of both single-mode drying (CD and IR). The effect of IR drying conditions and pre-treatment on the physical quality of desiccated coconut was optimized. The drying time, specific energy consumption (SEC), effective moisture diffusivity, color change (ΔE), whiteness index (WI), oil content, peroxide value (PV), free fatty acid (FFA), and microstructure of desiccated coconut based on single-mode drying (CD and IR) and hybrid -mode drying (combined IRCD and sequential IR-IRCD) were evaluated. The moisture content reduction and the final color quality of the desiccated coconut from the recommended drying method were monitored and predicted using hyperspectral imaging (HSI) technology. The quality of the final desiccated coconut from recommended drying with the commercial was compared. The results showed that IR drying of desiccated coconut provided a faster drying rate with a shorter drying time compared to CD at 50-70°C of drying temperatures and 1.5-3.0 m/s of air velocity. The average effective moisture diffusivity value of infrared drying was greater with significant differences (p<0.05) than convective drying within the drying parameter range. The lowest activation energy was found at an air velocity of 2.3 m/s of infrared drying. The Page model provided excellent predictions of moisture change for both infrared and convective drying of desiccated coconut. With hot water blanching pre-treatment and the optimal infrared drying conditions of 64 °C for drying temperature and 2.4 m/s for air velocity, the lowest SEC and highest WI were attained. The sequential hybrid drying (IR-IRCD) at 70°C was recommended in this study due to its ability to achieve shorter drying times, lower energy consumption, higher moisture diffusivity, improved energy efficiency, minimal color changes with a higher whiteness index, and maintaining acceptable oil quality. The partial least squares regression (PLSR) of the pre-processed model at full spectrum (421-960 nm) of hyperspectral images demonstrated excellent prediction (R2 >0.95) on moisture content and color attributes. The moisture content and yellowness distribution map of desiccated coconut generated from PLSR models were observed. Sequential hybrid drying (IR-IRCD) at 70°C was also shown to be more effective than commercial drying in preserving the color quality and total polyphenol content (TPC) of desiccated coconut. The advantages of using sequential hybrid drying combined with HSI technology offered a substantial opportunity for industry stakeholders to explore and adopt this innovative approach.

Text FK 2024 50 - Declaration Form.pdf Restricted to Repository staff only Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (2MB) Text FK 2024 50 - Full Text.pdf Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (12MB) Text FK 2024 50.pdf Restricted to Repository staff only Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (12MB) Official URL or Download Paper: http://ethesis.upm.edu.my/id/eprint/19015

Actions (login required)

View Item