Sensory measurement of dynamic flavour intensity in ice cream with different fat levels and flavourings Michael Bom Frøst a, * , Hildegarde Heymann b , Wender L.P. Bredie a , Garmt B. Dijksterhuis a , Magni Martens a a Sensory Science Group, Department of Dairy and Food Science, LMC, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg, Denmark b Department of Viticulture and Enology, University of California, One Shields Avenue, Davis, CA 95616-8749, USA Received 14 April 2002; received in revised form 18 January 2004; accepted 23 May 2004 Available online 1 July 2004 Abstract Flavour compounds vary in physicochemical properties and therefore behave differently in foods with different fat content. The objective was to investigate differences in dynamic flavour intensity in a realistic food system and relate them to two relevant molecular descriptors for flavour compounds. Ice creams with different fat levels (3%, 6% and 12% milk fat) and flavouring (b- ionone (berry), d-nonalactone (coconut), isopentyl acetate (banana), vanillin (vanilla)) were examined. Approximately iso-intense concentrations (in 12% fat) were selected. Samples were analysed with time-intensity methodology, evaluating perceived melt rate and flavour intensity (trained panel N ¼ 12, 3 replicates). Data were analysed by ANOVA, principal component analysis (PCA) and ANOVA partial least squares regression (APLSR). Analyses of data showed faster perceived melt rates and faster increases and decreases in dynamic flavour perception with lower fat levels. Individual flavour compounds were not affected similarly by changes in fat level. Increase and decrease rates of dynamic flavour perception were related to boiling points and hydrophobicity of the flavour compounds. Isopentyl acetate with the lowest boiling point had the fastest increase rate and the slowest decrease rate in intensity. Vanillin with the lowest hydrophobicity index (log P ) had the fastest decrease rate. d-nonalactone and b-ionone with high boiling points and high log P had similar increase rates as vanillin, but had a slower decrease rate in flavour intensity. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Dynamic flavour perception; Time-intensity; Physicochemical properties; Ice cream 1. Introduction During the last few decades there has been much interest in flavours and their interactions with other constituents in the food matrix (Land, 1996). A whole array of food components has been shown to interact with flavours (for an overview, see McGorrin & Leland, 1996). Flavour compounds have a wide range of phys- icochemical properties, but the majority of flavour compounds are at least partially soluble in fat. Changes in the amount of fat in food affect the perceived intensity and duration of flavours (Shamil, Wyeth, & Kilcast, 1991/92). This is a challenge to all product development involving reduction of the fat content. Advancing methodological tools for sensory analysis in connection with formulation of lower fat versions of products will provide product developers with a better foundation for their decisions regarding reformulation of flavours. Ice cream is a highly complex food matrix, containing proteins, fat, sugars, air, minerals, etc. and countless interfaces between the different constituents. During consumption it undergoes phase changes from solid to liquid. Ice creams are generally made with added flavour compounds, either naturally occurring in one of the ingredients (e.g. strawberry), or added as flavour mix- tures or extracts. This complexity, phase changes during consumption and the importance of flavour provides an important matrix for investigating dynamic flavour intensity. It is well established that fat content affects flavour release. Generally speaking, a higher fat content leads to a slower release (Hatchwell, 1996). Other con- stituents affect flavour release as well. Different proteins interact with flavour compounds, and can cause * Corresponding author. Tel.: +45-3528-3207; fax: +45-3528-3190. E-mail address: mbf@kvl.dk (M.B. Frøst). 0950-3293/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodqual.2004.05.009 Food Quality and Preference 16 (2005) 305–314 www.elsevier.com/locate/foodqual