Vol 62, No 2 May 2009 International Journal of Dairy Technology 189 ORIGINAL RESEARCH *Author for correspondence. E-mail: dears@selcuk.edu.tr © 2009 Society of Dairy Technology doi: 10.1111/j.1471-0307.2009.00467.x Blackwell Publishing Ltd Oxford, UK IDT International Journal of Dairy Technology 1364-727X 1364-0307 Society of Dairy Technology 2009 XXX ORIGINAL RESEARCH ORIGINAL RESEARCH Shelf life determination of Yayik butter fortified with spice extracts DERYA ARSLAN,* DURMU S SERT, AHMET AYAR and MEHMET MUSA ÖZCAN Department of Food Engineering, Faculty of Agriculture, Selçuk University, Kampus, Konya, Turkey Sage ( Salvia officinalis L.), cinnamon (Cinnamomum zeylanicum), rosemary (Rosmarinus officinalis L.), clove (Syzygium aromaticum L.), sumac (Rhus coriaria L.), oregano (Origanum vulgare L.), ginger (Zingiber officinale), caraway (Cuminum cyminum L.) and thyme ( Thymus vulgaris L.) extracts were added at two concentrations (0.2 and 0.5%) to yayik butter. The butter samples were stored at two different temperatures, 4°C and 25°C. Product acceptability was monitored following the Weibull Hazard sensory method where the end of shelf life was the time at which 50% of panellists found the product unacceptable. Ginger, thyme and cinnamon extracts increased the shelf life of yayik butter and were comparable to the synthetic preservatives sorbic acid and BHA. The shelf life of the samples stored in the refrigerator was approximately twice as long as the samples stored at room temperature. Keywords Yayik butter, Shelf life, Weibull Hazard, Spice extract. *Author for correspondence. E-mail: dears@selcuk.edu.tr INTRODUCTION In Turkey, butter may be produced from either yogurt or cream. ‘Yayik butter’ is the butter made from yogurt which is commonly consumed in Turkey (Sa˝dıç et al. 2004). Lipid oxidation is a major quality problem in the processing and storage of fats, oils and fat- containing foods (Yang et al. 2002). Oxidation products of lipids affect food quality due to changes in colour, flavour, texture and nutritional value (Frankel 1991; Brewer et al. 1999; Öztürk and Çakmakçı 2006). Factors such as heat, oxygen, light and certain metal ions, notably iron and copper, also play a part in the occurrence of oxidation (Frankel 1991). For these reasons a high oxidative stability of lipids is very important for human health and also has economic importance. In addition, lipid oxidation leading to rancidity is often a decisive factor deter- mining the shelf life of food products. Antioxidants are needed to prevent the formation and oppose the actions of radicals and reactive oxygen species (Lercker and Caboni 1998). Most of the commonly used antioxidants are synthetic compounds such as t -butyl-4-hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and natural antioxidants such as tocopherols because of their chemical stability, low cost and availability (Yang et al. 2002). Generally, oxidation of food can be prevented by synthetic antioxidants, including BHA and BHT, but their safety has been questioned (Pokorny 1991). However, there is a scarcity of information in the literature about the improvement of the storage life of butter by using natural and synthetic antioxidants. Considerable research on the application of spices as a source of natural antioxidants has been carried out (Zegarska et al. 1998). The end of shelf life can be determined from sensory data by various graphical methods. Gacula (1975) introduced the use of hazard rate for shelf life testing of food. The maximum- likelihood graphical procedure, or the Weibull Hazard method, has been used for shelf life deter- mination of many foods (Pickering 1984; Wittinger and Smith 1986; Schmidt and Bouma 1992; Gacula and Singh 1998; Thiemig et al. 1998; Cardelli and Labuza 2001; Duyvesteyn et al. 2001; Al-Kadamany et al. 2003). The aim of this study was to evaluate the effects of some spice extracts on the shelf life of yayik butter by applying the Weibull Hazard method. MATERIALS AND METHODS Materials The spices sage (Salvia officinalis L., leaves), cinnamon (Cinnamomum zeylanicum, tree bark), rosemary (Rosmarinus officinalis L., leaves), clove (Syzygium aromaticum L., buds), sumac (Rhus coriaria L., fruit pericarp), oregano (Origanum vulgare L., leaves), ginger (Zingiber officinale, rhizome), caraway (Cuminum cyminum L., fruit), and thyme (Thymus vulgaris L., leaves) were purchased from a local herb shop. These spices were ground,