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International Journal of Food
Volume 7, Issue 2


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, PaolaAntoine, and Alejandro Reyes

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 temperaturesignificantly affected
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 reductivecapability.
Air temperature 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
Author Notes: Financial support of projectFONDECYT 1100437 is gratefully acknowledged.

Mahn et al.: Convective Drying of Broccoli

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; Mukherjeeet al., 2008). Consuming this
vegetable 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 seleniumare 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 asblanching, cooking, and freezing, affect the content of
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. Theyconcluded that the
highest exergy efficiency was obtained 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...