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International Journal of Food Engineering
Volume 7, Issue 2 2011 Article 14

Optimization of Drying Kinetics and Quality Parameters of Broccoli Florets
Andrea V. Mahn, Universidad de Santiago de Chile Paola Antoine, Universidad de Santiago de Chile Alejandro Reyes, Universidad de Santiago de Chile

Recommended Citation: Mahn, Andrea V.; Antoine, Paola; and Reyes, Alejandro (2011)"Optimization of Drying Kinetics and Quality Parameters of Broccoli Florets," International Journal of Food Engineering: Vol. 7: Iss. 2, Article 14. DOI: 10.2202/1556-3758.2181 Available at: http://www.bepress.com/ijfe/vol7/iss2/art14 ©2011 Berkeley Electronic Press. All rights reserved.

Optimization of Drying Kinetics and Quality Parameters of Broccoli Florets
Andrea V. Mahn, Paola Antoine, andAlejandro Reyes

Abstract
Drying kinetics of broccoli florets in a tunnel dryer was studied. Effective moisture diffusivity (Deff) and activation energy for moisture diffusion (E0) were estimated. The effect of air temperature, air flow rate and particle size on antioxidant capacity, greenness and texture were calculated through a 23 factorial design. Air flow rate and temperature significantlyaffected drying time. Deff fluctuated between 2.82 x 10-10 and 2.00 x 10-9 (m2/s), and E0 was around 42 KJ/mol, agreeing with values reported in literature. The maximum antioxidant activity was obtained at 60°C, air flow rate of 4 m/s and 1.5 cm particle diameter, resulting in a 70 percent reduction in free radical scavenging ability and a 29 percent increase in total reductive capability. Airtemperature had significant effect on greenness, and air flow rate significantly affected texture. The optimization of convective drying of broccoli allows maximizing antioxidant activity and minimizing cost by saving energy and time. KEYWORDS: convective drying, broccoli florets, effective moisture diffusivity, antioxidant capacity Author Notes: Financial support of project FONDECYT 1100437 is gratefullyacknowledged.

Mahn et al.: Convective Drying of Broccoli

INTRODUCTION Broccoli (Brassica oleracea var. italica) has great potential to prevent some types of cancer (Finley et al., 2000; Zeng et al., 2003; Keck & Finley, 2004; Finley, 2005; Hartikainen, 2005; Abdulah et al., 2005) and cardiovascular diseases (Ganji & Kafai, 2004; Wu et al., 2004; Mukherjee et al., 2008). Consuming thisvegetable improves the general health status, mainly due to its antioxidant properties (Borowski et al., 2008). These healthy effects are triggered by some bioactive compounds found in broccoli that positively affect the defense against oxidative stress of the consumer. Among these compounds, glucosinolates, sulforaphane, polyphenols and minerals such as selenium are of major interest (Moreno et al.,2006). On the other hand, broccoli is mostly consumed as a processed food, and then its functional properties, as well as its physical characteristics, can be affected to different extents. Temperature, humidity, or light may induce some reactions during storage, sometimes leading to the loss of quality (Sanjuán et al., 2003). Processes such as blanching, cooking, and freezing, affect the contentof glucosinolates, sulforaphane and polyphenols in broccoli (Sikora et al., 2008; Zhang & Hamauzu, 2004; Gebczynski & Lisiewska, 2006). The dehydration process of broccoli has been understudied so far. Icier et al. (2010) performed an exergy analysis of broccoli dehydration by different processes, such as fluidized bed and heat pump drying. They concluded that the highest exergy efficiency wasobtained in a fluidized bed dryer. Rosa et al. (1997) investigated the effect of dehydration on glucosinolates content in broccoli. They found that 50–65 °C drying maintained the original glucosinolates content, nevertheless glucosinolates were hydrolyzed during rehydration. Recently, Mrkic et al. (2010) found that blanching before drying significantly decreased the glucosinolate content, which in...