Vacuum frying process of gilthead sea bream (Sparus aurata) fillets A. Andrés-Bello, P. García-Segovia, J. Martínez-Monzó ⁎ Food Technology Department, Polytechnic University of Valencia, Camino de Vera, s/n, 46022 Valencia, Spain abstract article info Article history: Received 2 June 2009 Accepted 3 June 2010 Keywords: Vacuum frying Fish Oil content Shrinkage Vacuum frying was tested as an alternative technique to develop low oil content fried gilthead sea bream fillets. Three oil temperatures for vacuum frying (90, 100, and 110 °C) were considered. For each temperature the times investigated were 1, 2, 3, 4, 5, 6, 8 and 10 min. To compare the effect of vacuum frying to atmospheric frying on the characteristics of gilthead sea bream fillets and frying rate, treatment at 165 °C was considered. The effect of oil temperature and pressure conditions on the drying process and oil absorption of sea bream fillets was investigated. Other product attributes such as shrinkage and colour were analyzed. Atmospheric frying (165 °C) produces a greater decrease in the mass of the fillets than vacuum frying treatment. Compared with atmospheric frying, oil content of vacuum-fried fish fillets was lower. After ten minutes of treatment the values obtained for vacuum frying were 0.14 ± 0.01 g oil /g dry solid , 0.18 ± 0.02 g oil /g dry solid and 0.12 ± 0.01 g oil /g dry solid for 90 °C, 100 °C and 110 °C respectively and 0.27 ± 0.01 g oil / g dry solid for traditional frying at 165 °C. Atmospheric frying was the treatment that produced the greatest shrinkage in the fillets reaching values of 36.8% with respect to the fresh sample after ten minutes of treatment. For vacuum treatments shrinkage values ranged between 23.7% and 33.0% at 100 °C and 110 °C respectively after 10 min of frying. According to the results, the vacuum treated samples became lighter, less greener and more yellow. Industrial relevance: Healthy products are a tendency in the international market. Vacuum frying offers some advantages that can include: the preservation of natural colour and flavours of the products due to low temperature and low oxygen content during the process (better than with conventional deep fat frying), and has less adverse effects on oil quality. The use of this technology on fish products can improve the problems of market saturation at the present time for some species like gilthead sea bream (Sparus aurata). © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Aquaculture in Mediterranean countries, including Spain has experienced a spectacular growth that could turn it into one of the main food producing industries in the near future (Lougovois, Kyranas, & Kyrana, 2003). The sector needs to diversify supply and to produce healthier food linked to the increasing demands of the consumer for quality food elaborated with natural and safe ingre- dients and long shelf-life (Goulas, Chouliara, Nessi, Kontominas, & Savvaidis, 2005). For these reasons, the study of the technologies that maintain the shelf-life of fish products (quality and safety) is more than justified, constituting a field of research of great interest responding to the demands of the sector and the consumer. Fish is a food that must be included in all healthy and balanced diets. The beneficial effect that fish consumption has for human health is based on its content in n-3 PUFA (polyunsaturated fatty acids). The influence of these fatty acids on the prevention and treatment of a multitude of diseases has been demonstrated (Das, 2000; Simpoulos, 2001). Since most fish species are consumed cooked, the nutritional value of the final cooked product is of major importance for human health. Culinary processes can significantly alter the content, composition and biological activity of fish lipids. Frying, which is commonly used for cooking fish, leads to an increase in the fat content of the fish fillet (Candela, Astiasaran, & Bello, 1997; Aro, Tahvonen, Mattila, Nurmi, Sivonen, & Kallio, 2000), extensive lipid exchanges between the fish and the frying medium (Sebedio, Ratnayake, Ackman, & Prevost, 1993) along with the production of oxidized and polymerized lipid products (Kubow, 1992; Skog, Johansson & Jagerstad, 1998). Deep-fat frying is the most common unit operation, involving the immersion and cooking of foods in hot oil, as evidenced by the worldwide annual production of more than 20 million tons of frying oil (Gertz, 2004). Vacuum frying is defined as the frying process that is carried out under pressures well below atmospheric levels, preferably below 50 Torr (6.65 kPa). Due to the low pressure, the boiling point of the water in the food is lowered. Vacuum frying offers some advantages that can include: (1) reduction of the oil content in the fried product, (2) preservation of natural colour and flavours (better than with conventional deep fat frying), and (3) reduction of adverse effects on oil quality (Garayo & Moreira, 2002; Shyu, Hau, & Hwang, 2005). Innovative Food Science and Emerging Technologies 11 (2010) 630–636 ⁎ Corresponding author. Tel.: + 34 963879364; fax: + 34 963877369. E-mail address: xmrtine@tal.upv.es (J. Martínez-Monzó). 1466-8564/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2010.06.002 Contents lists available at ScienceDirect Innovative Food Science and Emerging Technologies journal homepage: www.elsevier.com/locate/ifset