Sodas

International Journal of Food Science and Technology 2012, 47, 167–176

167

Original article Optimisation of pomegranate (Punica Granatum L.) juice spray-drying as affected by temperature and maltodextrin content
Hasan Vardin* & Mehmet Yasar
Food Engineering Department, Faculty of Agriculture, Harran University, Sanliurfa, Turkey (Received 10 April 2011; Accepted in revised form 14September 2011)

Summary

Pomegranate juice powder is easier to handle and has more potential applications than the concentrate. In this study, the response surface, 3-level factorial design was used to evaluate the influence of spray-drying conditions on the physicochemical properties of a powdered product obtained by drying pomegranate juice concentrate (PJC). It was spray-dried with a lab-scalespray-dryer using 18 and 7 dextrose equivalent (DE) maltodextrins (MD) as drying-aid agents. Adding MD significantly reduced the hygroscopicity and stickiness of the pomegranate juice powder, and thus yielded higher recovery. The maximum achieved ratio of PJC ⁄ MD was 1 ⁄ 1, and it was obtained with the use of DE7 MD. However, graphical optimisation studies resulted in 125–145 °C and 0.6–0.8 PJC ⁄ MDratio as optimum variables to produce acceptable dried powder. The results indicated that increasing inlet air temperature increases solubility time and loss of anthocyanins and decreases bulk density and moisture content of the powder.
Maltodextrin, optimisation, pomegranate, spray drying, stickiness.

Keywords

Introduction

Pomegranate (Punica granatum L.) is one of the important fruitsgrown in Turkey, Iran, USA, Mediterranean and Arabic countries. The edible part of the fruit contains considerable amount of acids, sugars, vitamins, polysaccharides, polyphenols and important minerals. The fruit is consumed directly as fresh arils as well as fresh juice, which can also be used in beverages for jellies, and flavouring and colouring agents. The kernels are also used as a garnish fordesserts and salads (ALMaiman & Ahmad, 2002; Vardin & Fenercioglu, 2003). Pomegranate juice (PJ) has bitter–stringent taste, and is used to enhance colour and flavour of a wide range of juices, beverages and other food products (Altan & Maskan, 2005). It has been reported that PJ has potent anti-atherogenic effects in healthy humans and atherosclerotic effects in mice that may be attributable to itsanti-oxidative properties (Negi et al., 2003). PJ is also a natural preservative, due to its high phenolic substance, invert sugar and organic acid contents (Robert et al., 2010). Bhandari et al. (1993) investigated the conditions of producing blackcurrant, raspberry and apricot powder with spray drying using maltodextrin (MD) with dextrose equivalent (DE) 6, 12, 19 as drying agent, and obtainedthe optimum ratio of additive materials.
*Correspondent: E-mail: hvardin@harran.edu.tr

The purpose of PJ drying is to produce stable and easily handled form of fruit juice as a powder with extended shelf life. In addition, it can be used as ingredient in dry food products, such as bread, cake and cookie mixes, breakfast cereals and dried soups. Dried PJ powder possesses all the advantages ofpomegranate juice concentrate (PJC), beyond many disadvantages of the juice. Spray drying is one of the most complex methods for fruit juice drying. Fruit juice is very sensitive and is open to be affected by various drying parameters. Among the main problems in fruit juice drying, such as PJ, are stickiness and thermoplasticity stemming from its composition. It is a well-known fact that foods,which contain large amounts of simple sugars (sucrose, glucose, fructose), are impossible to spray dry in pure form due to stickiness problem (Rodriguez-Hernandez et al., 2005; Roustapour et al., 2006). The particles stick to one another, to the dryer and to cyclone walls and remain there, forming thick wall deposits, while very little product comes out at the dryer’s exit. This might lead to low...