Trends in Food Science & Technology 65 (2017) 49e67
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Review
Trends of spray drying: A critical review on drying of fruit and vegetable juices Mohammad Rezaul Islam Shishir, Wei Chen* Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Key Laboratory of Agro-Products Postharvest Handling, Ministry of Agriculture, National & Local Joint Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang University, Hangzhou 310058, China
a r t i c l e i n f o
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Article history: Received 24 December 2016 Received in revised form 23 March 2017 Accepted 11 May 2017 Available online 17 May 2017
Background: Spray drying is extensively used to preserve fruit and vegetable juices in powder form. The major concern is to obtain high quality fruit and vegetable powders, which requires optimization of spray drying conditions. High drying temperature damages sensitive bioactive compounds, carrier agent protects such compounds and other factors involved in spray drying affect physicochemical and microstructural attributes of the product. Scope and approach: This review summarizes current trends of spray drying of fruit and vegetable juices, covering principles of spray drying, physicochemical and microstructural effects of spray drying conditions, optimization of spray drying conditions and new developments in spray drying. Several new techniques have been introduced into spray drying, helping to overcome its limitations. These techniques are posted to set new standards for the production of high quality fruit and vegetable powders in industrial application. Key findings and conclusions: The most significant factors in spray drying are inlet temperature and carrier agent. Successful spray drying enhances physical properties of powdered products, while preserving bioactive compounds with the help of carrier agents or their combinations. Response surface methodology is the most suitable tool for optimization of spray drying conditions. The application of ultrasound technique during atomization, vacuum drying chamber with controlled atmosphere, and supply of dehumidified air to drying chamber of basic spray dryer have distinctly improved the potential of the technology over conventional spray drying. These advances will contribute to further research improvement of drying of fruit and vegetable juices by conventional approaches as well as modified spray drying techniques. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Spray drying Fruit and vegetable juices Carrier agent Powder properties Response surface methodology
1. Introduction Fruits and vegetables provide health benefits due to their high nutritional content and health-promoting effects (Bao et al., 2016; Chen, Su, Xu, Bao, & Zheng, 2016; Chen, Xu, Zhang, Su, & Zheng, 2016; Chen, Zhou, & Zheng, 2015; Xu et al., 2017). High perishability is the main problem challenging fruit and vegetable production. Postharvest spoilage causes fast degradation of quality resulting in large wastage (Basseto, Jacomino, Pinheiro, & Kluge, 2005). The production of fruit and vegetable juice powders is a promising approach to reduce the expenditures of packaging,
* Corresponding author. Department of Food Science and Nutrition, Zhejiang University, 866 Yuhangtang Road, Xihu District, Hangzhou 310058, China. E-mail address:
[email protected] (W. Chen). http://dx.doi.org/10.1016/j.tifs.2017.05.006 0924-2244/© 2017 Elsevier Ltd. All rights reserved.
storage and transportation, but also to curtail losses because of the high stability of powder form as compared with its liquid counterpart. Juices from fruit and vegetable can be preserved from weeks to months (Esteve, Frígola, Rodrigo, & Rodrigo, 2005; Walkling-Ribeiro, Noci, Cronin, Lyng, & Morgan, 2009), while powdered products produced from fruit and vegetable juices can be preserved from months to years depending on packaging (Chauhan rdova, & Saavedra, 2013; Pua et al., & Patil, 2013; Henríquez, Co 2008). The flexibility of powder form facilitates advanced formulations and opens new markets. In addition, the production of highly nutritional and regularly micro-structured fruit and vegetable powders may meet the requirements in pharmaceuticals and cosmetic industries. A variety of drying techniques are available for use on the industrial scale. According to Chopda and Barrett (2001), the most
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M.R.I. Shishir, W. Chen / Trends in Food Science & Technology 65 (2017) 49e67
successful methods for fruit juice powder production are freeze drying, foam mat drying and spray drying. Spray drying is the most economic technique maintaining quality by rapid dehydration. It provides a large surface area in the form of fine liquid droplets through atomization in the drying chamber, which leads to the production of regularly and spherically shaped powder particles (Fazaeli, Emam-Djomeh, Kalbasi Ashtari, & Omid, 2012; Turchiuli, Gianfrancesco, Palzer, & Dumoulin, 2011). Freeze drying is regarded as the most efficient in nutrients preservation in powdered products, but its industrial-scale application is hampered by the high expenditures of the instrumentation and high energy consumption, as well as by a low throughput (Hsu, Chen, Weng, & Tseng, 2003; Ratti, 2001). The quality of the final product depends on the conditions of spray drying process, which include feed concentration, inlet and outlet air temperature, feed flow rate, compressor air flow rate, drying air flow rate, type of atomizer and atomizer speed (Fazaeli et al., 2012; Goula & Adamopoulos, 2005; Goula, Adamopoulos, & Kazakis, 2004; Kha, Nguyen, & Roach, 2010). Higher bulk density and low moisture content are the most important requirements on the powdered product. The reasons are that a high bulk density reduces packaging and shipping costs and increases flowability, while low moisture content (
