Effects of Gac aril microwave processing conditions on oil extraction efficiency, and b-carotene and lycopene contents Tuyen C. Kha a,b , Minh H. Nguyen a,c,⇑ , Paul D. Roach a , Costas E. Stathopoulos a a School of Environmental and Life Sciences, The University of Newcastle, Australia b Faculty of Food Science and Technology, Nong Lam Unviersity, Viet Nam c School of Science and Health, University of Western Sydney, Australia article info Article history: Available online xxxx Keywords: Gac oil b-Carotene Lycopene Microwave Steaming Pressing Extraction efficiency abstract The effects of Gac oil extraction conditions including microwave power, microwave time, steaming time and hydraulic pressure on extraction efficiency (EE), and b-carotene and lycopene contents were studied. It was found that the EE, and b-carotene and lycopene contents could be enhanced by suitable extraction conditions. Microwave drying was found to be better than air drying for pretreatment. Moisture content after drying and steaming between 8% and 11% (wt/wt) were best for pressing. Results showed that the most suitable conditions for Gac oil extraction from 900 g samples were microwave power of 630 W, microwave time of 65 min, steaming time of 20 min and hydraulic pressure of 170 kg/cm 2 . Under these conditions, the highest EE of 93% was achieved while Gac oil contained the highest content of b-carotene and lycopene at 140 and 414 mg/100 mL, respectively. Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. 1. Introduction Gac fruit (Momordica cochinchinensis Spreng) contains high lev- els of bioactive compounds, especially essential fatty acids, b-caro- tene and lycopene (Aoki et al., 2002; Kubola and Siriamornpun, 2011; Nhung et al., 2010; Vuong et al., 2006) that are well known to be beneficial in human health. For example, the aril of Gac fruit contains a significant amount of fatty acids, at 102 mg per g of edi- ble portion (Vuong et al., 2002). About 70% of total fatty acids in the aril are unsaturated, and 50% of these are polyunsaturated (Vuong, 2000). The highest concentrations of b-carotene and lycopene are found in the fresh aril, at 101 lg/g and 380 lg/g respectively (Aoki et al., 2002). Furthermore, the presence of fat in the Gac fruit aril plays an important role in the absorption of carotenes and other fat-soluble nutrients (Kuhnlein, 2004). The benefits from Gac nutri- ents can be obtained from the consumption of Gac powder (Kha et al., 2010, 2011). However there are many applications where just Gac oil is needed. Therefore, it is important to determine a suitable extraction method for Gac oil which yields the maximum extraction efficiency (EE) and bioactive compounds including b- carotene and lycopene. Generally, mechanical extraction by hydraulic or screw press is one of the most common methods in oil processing industry. How- ever, the EE seldom reaches 70% when a hydraulic press is used (Bargale et al., 1999; Owolarafe et al., 2007). Therefore, attempts have been made to use air-drying or microwave irradiation and steaming prior to pressing to enhance the EE. Recent interest in microwave extraction for plant oils has been highlighted owing to their benefits (Desai et al., 2010). Effect of treatment with micro- wave radiation before mechanical pressing on oil recovery and quality of oil from Chilean hazelnut was investigated by Uquiche et al. (2008). Different microwave treatment conditions (potencies and times) were studied, and an increase in oil yield was found in comparison with untreated samples. Moreover, the microwave- pre-treated oil samples also possess superior quality characteris- tics in terms of oxidative oil stability, oil composition and other physicochemical properties, as compared to untreated one. Simi- larly, Azadmard-Damirchi et al. (2010) reported that a significantly higher yield of oil from rapeseed could be obtained by treatment with microwaves before pressing. Results also indicated that this extraction method could be used to produce rapeseed oil with high oxidative stability and nutraceutical content. Therefore, investiga- tions on the microwave treatment conditions prior to pressing oil from Gac aril are recommended. Moreover, steaming treatment of the microwave-dried material is one of the most important steps in the oil extraction process. This step can adjust the moisture content of starting materials prior to pressing so it is the most significant factor affecting the oil yield (Mpagalile and Clarke, 2005; Sivala et al., 1991). In addi- tion, under steaming process, the heat can soften and break down the oil containing cells, and also lower oil viscosity (Mpagalile and Clarke, 2005; Ward, 1976). Hence the oil is easily released in sub- 0260-8774/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jfoodeng.2012.10.021 ⇑ Corresponding author at: School of Environmental and Life Sciences, P.O. Box 127, Ourimbah, NSW 2258, Australia. Fax: +61 2 434 84145. E-mail address: Minh.Nguyen@newcastle.edu.au (M.H. Nguyen). Journal of Food Engineering xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng Please cite this article in press as: Kha, T.C., et al. Effects of Gac aril microwave processing conditions on oil extraction efficiency, and b-carotene and lyco- pene contents. Journal of Food Engineering (2012), http://dx.doi.org/10.1016/j.jfoodeng.2012.10.021