M: Food Microbiology & Safety Effects of Turmeric, Shallot Extracts, and Their Combination on Quality Characteristics of Vacuum-Packaged Rainbow Trout Stored at 4 ± 1 ◦ C Samaneh Pezeshk, Masoud Rezaei, and Hedayat Hosseini Abstract: The effects of turmeric extract (T), shallot extract (Sh), and their combination (T + Sh) on the quality of vacuum-packaged rainbow trout (Oncorhynchus mykiss) were examined during refrigerated storage (4 ± 1 ◦ C) over a period of 20 d. Fish samples were divided into 4 batches; 3 batches were treated by dipping for 30 min in aqueous solution of turmeric extract (1.5%; v/v), shallot extract (1.5%; v/v), or turmeric and shallot extract combination (1.5% + 1.5% v/v), while the fourth batch was dipped in distilled water as a control sample. The control and the treated ﬁsh samples were analyzed periodically for microbiological (total viable count, psychrotrophic count), chemical (total volatile base nitrogen [TVB-N], peroxide value [PV], and thiobarbituric acid [TBA] value), and sensory characteristics. The results indicated that the effect of the T, Sh, and T + Sh on the ﬁsh samples were to enable the good quality characteristics to be retained longer and to extend the shelf life during the refrigerated storage. Keywords: antibacterial activity, antioxidant activity, ﬁsh, food preservation, sensory evaluation Introduction Fish are more vulnerable than red meat and chicken as it con- tains relatively large amounts of free amino acids and a higher ﬁnal pH limiting the shelf life of the product (Mexisa and others 2009). During storage, the quality of ﬁsh and seafood products de- grade due to a complex process, in which physical, chemical, and microbiological mechanisms are implicated. Enzymatic and chem- ical reactions are usually responsible for the initial loss of freshness, while microbial activity is responsible for subsequent spoilage, which thereby establishes product shelf life (Sallam and others 2007). The increasing demand for high-quality fresh seafood has resulted in the use of methods and technologies for better fresh ﬁsh utilization. Vacuum packaging is widely used in the food in- dustry because of its inﬂuence in decreasing oxidative reactions in the product at relatively low cost. This method of packaging can be a supplement to the other preservation methods such as low temperature, antioxidants, and antibacterials to delay spoilage, extend the shelf life, maintain a high quality, assure the safety, and reduce economic loss of ﬁsh and seafood products (Manju and others 2006; Mahmoudzadeh and others 2010). The natural antioxidants and antimicrobial activity of plant oils and extracts has been recognized for many years (Khanzadi and others 2010; Raoufy and others 2010) and has been applied in several studies as antioxidant or antibacterial agents for many ﬁsh species, including bonito (Lin and Lin 2005), mackerel (Banerjee MS 20101368 Submitted 12/2/2010, Accepted 4/18/2011. Authors Pezeshk and Rezaei are with Dept. of Fisheries, Faculty of Marin Sciences, Tarbiat Modares Univ., Noor, Iran. Author Hosseini is with Dept. of Food Science &Technology, Natl. Nutrition and Food Technology Research Inst., Faculty of Nutrition Sciences &Food Technology, Shahid Beheshti Univ. of Medical Sciences, Tehran, Iran. Direct inquiries to author Hosseini (E-mail: hedayat@sbmu.ac.ir). 2006), shrimp (Cadun and others 2008), swordﬁsh (Kykkidou and others 2009), octopus (Atrea and others 2009), and trout (Mexisa and others 2009). These studies have demonstrated both antimi- crobial and antioxidant activity of herbal extracts against food- borne pathogens and extension of the shelf life of ﬁsh. Among the several vegetables, herbs, and spices, turmeric (Curcuma Longa L.) and shallot (Allium ascalonicum L.) are 2 well-known items in our daily diet. Turmeric is a tropical herb of the Zingiberaceae family indigenous to southern Asia. Several studies demonstrated that turmeric is a good source of natural antioxidant and an- tibacterial agents (Negi and others 1999; Jayaprakasha and others 2002; Kumar and others 2006). Shallot is a herb of the Allium species. Reports concerning the biological effects of shallot are scarce compared to other Allium species such as onion and garlic. Recently, shallot has been reported to show antioxidative, antibac- terial, and free radical scavenging abilities (Adeniyi and Anyiam 2002; Wongmekiat and others 2008). However, research on the retention of the good quality characteristic and the extension of shelf life during refrigerated storage of ﬁsh by turmeric and shallot is still lacking. Therefore, the main objective of the present work was to determine the effect of turmeric extract, shallot extract, and their combination application on the shelf-life extension of whole gutted rainbow trout (Oncorhynchus mykiss) during vacuum- packaged storage at 4 ± 1 ◦ C by evaluating certain microbiological, chemical, and sensory parameters. Materials and Methods Preparation and treatment of ﬁsh samples Fish sample preparation. Fresh rainbow trout with average weight of 350 g and average length 28 cm were purchased from a public market alive and were brought within 60 min to the laboratory in sealed foamed polystyrene boxes containing ﬂaked ice. Then, these were gutted and washed in potable water. C  2011 Institute of Food Technologists R  doi: 10.1111/j.1750-3841.2011.02242.x Vol. 76, Nr. 6, 2011  Journal of Food Science M387 Further reproduction without permission is prohibited