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The perception of strawberry aroma in milk
W.L.P. Bredie and M.A. Petersen (Editors) Flavour Science: Recent Advances and Trends 9 2006 Elsevier B.V. All rights reserved.
553
The perception of strawberry aroma in milk Zdenka Panovska, Alena gedivfi, Jan Pokorn)~ and Dobroslava Lukegovfi
Department of Food Chemistry and Analysis, Institute of Chemical Technology in Prague, Technickd 3, 166 28 Prague, Czech Republic
ABSTRACT The flavour release in foods depends on the nature and concentration of flavour compounds present and their interaction with the food matrix. Studies on flavour release should also include the evaluation of food properties by using the human senses. Perceived intensity and pleasantness of strawberry aroma in milk were tested by sensory methods. The ability of assessors to distinguish fattiness of milk and small concentration of strawberry aroma was tested by a ranking test. Samples were evaluated by descriptive analysis using 9 attributes to characterising the sensory profile of the milk aroma with added a strawberry flavour mixture. The results show the difference in sweet taste among the samples. The strawberry aroma influences the feeling of fattiness. The panellists judged milk containing strawberry aroma to be fatter. 1. I N T R O D U C T I O N Sensory science evaluates the food properties by using the human senses that react to certain stimuli from food. The sensation depends not only on the type and intensity of the stimulus but also on the person's or group of person's sociological and psychophysiological conditions [1]. Moreover it is also important to choose the suitable method that allows one to determine the reliability of the data and it is also necessary to know in detail the properties and composition of compounds that form the food. Milk can be produced to differ in fat content. The fat in milk is emulsified as micro globules and the first sensation is the aroma of fat soluble volatile flavour molecules, perceived through the nose and mouth. Frost and co-workers studied sensory perception of fat in milk [2]. They investigated the effects of various factors such as thickeners, cream flavours and whiteners on sensory properties and perceived fattiness. Their experiments showed that the fat does not affect the sensory properties of milk in a linear fashion and that there are larger sensory
554 differences between milk with 0.1% and 1.3% fat than there are between 1.3% and 3.5% fat. Tepper and Kuang studied the effect of flavour addition in milk. They showed that products with a high level of added aroma compounds were perceived similar to products with a higher fat content [3]. The aim of this study was to evaluate the effect of strawberry aroma on perception of fat and intensity of sweet taste. 2. MATERIALS AND METHODS
2.1. Material Pasteurised milk with three different levels of fat content (0.5%, 1.5% and 3.5%) was used. The strawberry flavour mixture (0.1 g/l) was kindly provided by Givaudan. 2.2. Sensory analysis Sensory evaluation was performed in the laboratory with 6 individual booths equipped according to requirements of the international standard ISO 8589. The preparation and serving of the samples were in agreement with the requirements of ISO 6658-1985. Tap water was used for washing the mouth before the first sample and between samples. Samples were served blind coded in 20 ml portions at 15 ~ and 22 ~ 2.3. Sensory panel Sixty-five assessors (22 men, 43 women) mostly university students were experienced in sensory analysis, particularly with the sensory profiling and ranking methods. 2.4. Sensory analysis Ranking tests were performed with two sets of milk samples (0.5%) with different flavour concentration were prepared. The first set had 8 samples (0; 0.05; 0.1; 0.15; 0.2; 0.25; 0.3; 0.35 g/l) and the second set had 5 samples (0; 0.2; 0.4; 0.6; 0.8 g/l). Sensory profiling was done using unstructured line scales of 100 mm long, constructed after the standard ISO 4121-1985. The scales were anchored by descriptors. Statistical analyses were done using Microsoft Excel 2000 and SPSS software v 12.0. 3. RESULTS
3.1. Testing ability of panellist to recognise level of fat in milk The assessors were tested for their ability to recognise differences in fat content of milk by rating on a sensory scale the fattiness of milk containing 1.5% fat (Figure 1). 3.2. Testing the ability of paneilists to rank the samples with strawberry aroma The assessors ranked the model samples of milk (0.5%) with different levels of strawberry aroma by their intensities. In the first set the step differences in concentration of strawberry flavour were too small, namely 0.05 g/1. The assessors could not distinguish the differences among samples. Therefore, a second set was prepared with
555 step differences in concentration of strawberry flavour of 0.2 g/1. About 50% of assessors could distinguish correctly the intensity of strawberry aroma in milk. It was easier for assessors to distinguish differences at the lower concentrations (0.2 and 0.4 g/l) than at the higher concentration of 0.4 to 0.6 and from 0.6 to 0.8 g/1 (Figure 2).
Figure 2. Result from intensity ranking of strawberry flavour in milk with different added concentrations of strawberry flavour (g/l). Percent of correct answers form the ranking test.
556
3.3. Profile of low fat milk with and w i t h o u t aroma The profile of milk with and without aroma was evaluated by assessors for all types of milk. The main differences were observed in the profile of low fat milk (Figure 3).
1 8O 7
~~
2
1 - Pleasantness
of s m e l l
2 - Pleasantness
of t a s t e
3 - I n t e n s i t y of s w e e t t a s t e 4 - P l e a s a n t n e s s of s w e e t t a s t e 5 - Intensity aroma 6 - Pleasantness 7 - Fattiness
6
3
-- ~
of a r o m a
- m i l k 0 . 5 % fat + a r o m a 0.1 g/I m i l k 0 . 5 % fat
Figure 3. Sensory and hedonic profiles of low fat milk with or without added strawberry flavour. Analysis of variance (ANOVA) using 95% of confidence intervals was run for each of descriptors to disclose possible differences among the samples. The statistical differences were in pleasantness of smell, perception of sweet taste and also the aroma influenced the feeling of fattiness. The panellists considered milk with aroma fatter. The same profile was done also for fatter milk but there were no significant differences between samples. 4. D I S C U S S I O N AND C O N C L U S I O N Only 22% of assessors can correctly judge the fat content in milk. The most pleasant concentration of strawberry aroma in milk was 0.4 g/l (one third of assessors). The differences among samples with and without aroma were in perception of sweet taste. The aroma also influenced the feeling of fattiness. The panellists consider milk with aroma fatter. The same profile was done also for fatter milk but there were no significant differences between samples. We confirmed that fat does not affect the sensory properties of milk in a linear fashion. There are larger differences between low fat milk and middle fat than between middle fat and fat milk. References 1. P. Alvarez and M.A. Blanco, J. Sci. Food Agr., 80 (2000) 409. 2. M.B. Frost, G. Dijksterhuis and M. Martens, Food Quality Pref., 12 (2001) 327. 3. B.J. Tepper and T. Kuanga, J. Sens. Stud., 11 (3) (1996) 175.
553
The perception of strawberry aroma in milk Zdenka Panovska, Alena gedivfi, Jan Pokorn)~ and Dobroslava Lukegovfi
Department of Food Chemistry and Analysis, Institute of Chemical Technology in Prague, Technickd 3, 166 28 Prague, Czech Republic
ABSTRACT The flavour release in foods depends on the nature and concentration of flavour compounds present and their interaction with the food matrix. Studies on flavour release should also include the evaluation of food properties by using the human senses. Perceived intensity and pleasantness of strawberry aroma in milk were tested by sensory methods. The ability of assessors to distinguish fattiness of milk and small concentration of strawberry aroma was tested by a ranking test. Samples were evaluated by descriptive analysis using 9 attributes to characterising the sensory profile of the milk aroma with added a strawberry flavour mixture. The results show the difference in sweet taste among the samples. The strawberry aroma influences the feeling of fattiness. The panellists judged milk containing strawberry aroma to be fatter. 1. I N T R O D U C T I O N Sensory science evaluates the food properties by using the human senses that react to certain stimuli from food. The sensation depends not only on the type and intensity of the stimulus but also on the person's or group of person's sociological and psychophysiological conditions [1]. Moreover it is also important to choose the suitable method that allows one to determine the reliability of the data and it is also necessary to know in detail the properties and composition of compounds that form the food. Milk can be produced to differ in fat content. The fat in milk is emulsified as micro globules and the first sensation is the aroma of fat soluble volatile flavour molecules, perceived through the nose and mouth. Frost and co-workers studied sensory perception of fat in milk [2]. They investigated the effects of various factors such as thickeners, cream flavours and whiteners on sensory properties and perceived fattiness. Their experiments showed that the fat does not affect the sensory properties of milk in a linear fashion and that there are larger sensory
554 differences between milk with 0.1% and 1.3% fat than there are between 1.3% and 3.5% fat. Tepper and Kuang studied the effect of flavour addition in milk. They showed that products with a high level of added aroma compounds were perceived similar to products with a higher fat content [3]. The aim of this study was to evaluate the effect of strawberry aroma on perception of fat and intensity of sweet taste. 2. MATERIALS AND METHODS
2.1. Material Pasteurised milk with three different levels of fat content (0.5%, 1.5% and 3.5%) was used. The strawberry flavour mixture (0.1 g/l) was kindly provided by Givaudan. 2.2. Sensory analysis Sensory evaluation was performed in the laboratory with 6 individual booths equipped according to requirements of the international standard ISO 8589. The preparation and serving of the samples were in agreement with the requirements of ISO 6658-1985. Tap water was used for washing the mouth before the first sample and between samples. Samples were served blind coded in 20 ml portions at 15 ~ and 22 ~ 2.3. Sensory panel Sixty-five assessors (22 men, 43 women) mostly university students were experienced in sensory analysis, particularly with the sensory profiling and ranking methods. 2.4. Sensory analysis Ranking tests were performed with two sets of milk samples (0.5%) with different flavour concentration were prepared. The first set had 8 samples (0; 0.05; 0.1; 0.15; 0.2; 0.25; 0.3; 0.35 g/l) and the second set had 5 samples (0; 0.2; 0.4; 0.6; 0.8 g/l). Sensory profiling was done using unstructured line scales of 100 mm long, constructed after the standard ISO 4121-1985. The scales were anchored by descriptors. Statistical analyses were done using Microsoft Excel 2000 and SPSS software v 12.0. 3. RESULTS
3.1. Testing ability of panellist to recognise level of fat in milk The assessors were tested for their ability to recognise differences in fat content of milk by rating on a sensory scale the fattiness of milk containing 1.5% fat (Figure 1). 3.2. Testing the ability of paneilists to rank the samples with strawberry aroma The assessors ranked the model samples of milk (0.5%) with different levels of strawberry aroma by their intensities. In the first set the step differences in concentration of strawberry flavour were too small, namely 0.05 g/1. The assessors could not distinguish the differences among samples. Therefore, a second set was prepared with
555 step differences in concentration of strawberry flavour of 0.2 g/1. About 50% of assessors could distinguish correctly the intensity of strawberry aroma in milk. It was easier for assessors to distinguish differences at the lower concentrations (0.2 and 0.4 g/l) than at the higher concentration of 0.4 to 0.6 and from 0.6 to 0.8 g/1 (Figure 2).
Figure 2. Result from intensity ranking of strawberry flavour in milk with different added concentrations of strawberry flavour (g/l). Percent of correct answers form the ranking test.
556
3.3. Profile of low fat milk with and w i t h o u t aroma The profile of milk with and without aroma was evaluated by assessors for all types of milk. The main differences were observed in the profile of low fat milk (Figure 3).
1 8O 7
~~
2
1 - Pleasantness
of s m e l l
2 - Pleasantness
of t a s t e
3 - I n t e n s i t y of s w e e t t a s t e 4 - P l e a s a n t n e s s of s w e e t t a s t e 5 - Intensity aroma 6 - Pleasantness 7 - Fattiness
6
3
-- ~
of a r o m a
- m i l k 0 . 5 % fat + a r o m a 0.1 g/I m i l k 0 . 5 % fat
Figure 3. Sensory and hedonic profiles of low fat milk with or without added strawberry flavour. Analysis of variance (ANOVA) using 95% of confidence intervals was run for each of descriptors to disclose possible differences among the samples. The statistical differences were in pleasantness of smell, perception of sweet taste and also the aroma influenced the feeling of fattiness. The panellists considered milk with aroma fatter. The same profile was done also for fatter milk but there were no significant differences between samples. 4. D I S C U S S I O N AND C O N C L U S I O N Only 22% of assessors can correctly judge the fat content in milk. The most pleasant concentration of strawberry aroma in milk was 0.4 g/l (one third of assessors). The differences among samples with and without aroma were in perception of sweet taste. The aroma also influenced the feeling of fattiness. The panellists consider milk with aroma fatter. The same profile was done also for fatter milk but there were no significant differences between samples. We confirmed that fat does not affect the sensory properties of milk in a linear fashion. There are larger differences between low fat milk and middle fat than between middle fat and fat milk. References 1. P. Alvarez and M.A. Blanco, J. Sci. Food Agr., 80 (2000) 409. 2. M.B. Frost, G. Dijksterhuis and M. Martens, Food Quality Pref., 12 (2001) 327. 3. B.J. Tepper and T. Kuanga, J. Sens. Stud., 11 (3) (1996) 175.