- Email: [email protected]
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements
CHAPTER
47
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements Stefanie Sandgrubera and Andrea Buettnera,b a
Department of Chemistry and Pharmacy, Food Chemistry, University of Erlangen-Nuremberg, Erlangen, Germany b Fraunhofer Institute for Process Engineering and Packaging (IVV), Freising, Germany
47.1 INTRODUCTION A series of studies on adults demonstrated the protective effects of n-3 polyunsaturated fatty acids (PUFAs) with regard to coronary heart disease, as well as the fact that a diet supplemented with n-3 PUFAs may decrease mortality due to myocardial re-infarction and sudden death. These effects have been attributed to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are present in fish oil, as well as alpha-linolenic acid [1,2]. Besides this, n-3 PUFAs have been shown to be beneficial for fetal and neonatal development with regard to diverse aspects such as vision, cognition, and several others [3–5]. Accordingly, supplementation with (commonly encapsulated) fish oil products during pregnancy and the breastfeeding period has become increasingly popular to provide longchain n-3 PUFAs for improved development of brain and cardiovascular health function [6,7], and is also now a common supplement in everyday diet. Nevertheless, supplementation with such prescriptions repeatedly elicits complaints from consumers/patients about fishy impressions that appear after ingestion of the encapsulated material.
47.2 MATERIALS AND METHODS 47.2.1 Samples Fish oil samples were extracted from the capsules immediately before odorant extraction. Product 1 contained 61 mg DHA and 10 mg vitamin E per g fish oil (n = 14), Product 2 contained 143 mg DHA and V. Ferreira and R. Lopez (Eds): Flavour Science. DOI: http://dx.doi.org/10.1016/B978-0-12-398549-1.00047-7
© 2014 2013 Elsevier Inc. All rights reserved.
245
246
Stefanie Sandgruber and Andrea Buettner
9 mg vitamin E per g fish oil (n = 15), and Product 3 contained 360 mg DHA and 3 mg mixed natural tocopherols per g fish oil (n = 27).
47.2.2 Preparation of Solvent Extracts Each fish oil sample (1–5 g) was extracted with 5 mL dichloromethane (DCM). After extraction (30 min, RT), the fish oil volatiles were isolated by mild solvent assisted flavor evaporation (SAFE; 50°C, 5 × 10−3 Pa). Distillates were dried over anhydrous Na2SO4 and concentrated to a total volume of 100 μL.
47.2.3 Two-Dimensional High Resolution Gas Chromatography-Olfactometry/Mass Spectrometry (2D-HRGC-O/MS) Analyses were performed with a system consisting of two Type 3800 gas chromatographs (Varian, Darmstadt, Germany), coupled with a Saturn 2200 mass spectrometer (Varian) and ODP sniffing ports (Gerstel, Mühlheim, Germany). Mass spectra were generated at 70 eV ionization energy (CI).
47.2.4 Stable Isotope Dilution Assays (SIDAs) Defined amounts of the respective 2H stable isotopically-labeled odorants were added to the samples; then followed the work-up described above. The odorant amounts in fish oil were calculated from the intensity ratios of labeled and unlabeled compounds.
47.2.5 Sensory Analyses Sensory analyses were performed in a sensory panel room at 21±1°C. Fish oil samples (1 g) were presented in covered glass vessels (capacity 140 mL) to the sensory panel for comparative orthonasal evaluation (randomized order, no sample information; as in [8]) with attribute intensity rating on a scale from 0 (no perception) to 3 (strong perception). For the hedonic rating, the panelists were asked to rate pleasantness of the fish oil samples on a scale from 0 (dislike extremely) to 3 (like extremely).
47.2.6 Statistical Analyses Kruskal-Wallis ANOVA was used for multiple comparisons between fish oil products 1, 2, and 3 in orthonasal perception of each odor attribute and for quantitative results for each odorant, with significance level at 0.05.
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements
247
Fishy 3
2 Rancid-oil-like
Fatty
1
0
Tang-like
Oily Product 1
Product 2
Product 3
Figure 47.1 Aroma profile of fish oils (median values).
47.3 RESULTS To characterize the aroma profiles of the investigated fish oils (Figure 47.1), the attributes fishy, fatty, tang-like, oily, and rancid-oil-like, amongst others, were evaluated. At first sight Product 2 appears to stick out because of its dominant fishy odor, but this difference is statistically insignificant (Kruskal-Wallis ANOVA; H(2) = 5.7; P > 0.05). On the other hand, Product 1 shows high mean values according to the more negatively voted attributes tang-like and rancid-oil-like (Kruskal-Wallis ANVAO; H(2) = 0.9, 1.2; P > 0.1 in all attributes). According to this, Product 1 was rated as the “most disliked,” followed by Product 3; Product 2 was evaluated as the “least liked out of all three dislikable choices” (data not shown). Based on comparative aroma extract dilution analysis (data not shown), typical fatty acid oxidation odor substances dominated the odor composition of all three fish oils. Figure 47.2 shows concentrations of selected marker substances, measured by means of stable isotope dilution assays in conjunction with 2D-HRGC-O/MS. In contrast to the aroma profile evaluation, the concentrations between the three products revealed some pronounced differences. Within concentration ranges between 2 and 450 μg/kg, Product 1 consistently
248
Stefanie Sandgruber and Andrea Buettner
Product 1
Product 2
Product 3 n=7 n=5 n=6
Hexanal n=6 n=7 n=6
(Z)-Hept-4-enal
n=6 n=5 n = 11
(E)-Non-2-enal (E,E)-Deca-2,a4-dienal
n=6 n=4 n = 13
n=8 n=8 n = 11
y-Nonalactone n=8 n=8 n=7 n=7 n = 10 n=4
Oct-1-en-3-one (Z)-Octa-1, 5-dien-3-one 0
1
10
100
1000
Conc. [µg/kg]
Figure 47.2 Concentration (logarithmic representation) of potent odorants in investigated fish oil products.
represented the highest amounts of all analyzed volatile compounds except for the aldehyde (Z)-hept-4-enal, which was highest in Product 2. With regard to statistic analysis, the quantification data led to significant differences within all odor compounds (Kruskal-Wallis ANOVA; H(2)=13.3, 17.3, 17.6, 16.6, 19.6, 17.0; P < 0.01 in all odorants).
47.4 DISCUSSION AND CONCLUSION The presented data show that encapsulated fish oil products can vary to a considerable degree. Variance in specific odor attributes from orthonasal aroma profiling as well as the observed quantitative differences in oxidation products between products may explain consumer rejection of certain fish oil supplements.
ACKNOWLEDGEMENT This work was supported by the German Federal Ministry of Education and Research (BMBF). The authors are exclusively responsible for the contents of the publication.
REFERENCES [1] H.C. Bucher, P. Hengstler, C. Schindler, G. Meier, N-3 polyunsaturated fatty acids in coronary heart disease: a meta-analysis of randomized controlled trials, A. J. Med. 112 (4) (2002) 298–304.
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements
249
[2] P. Marckmann, M. Grønbæk, Fish consumption and coronary heart disease mortality. A systematic review of prospective cohort studies, Eur. J. Clin. Nutr. 53 (8) (1999) 585–590. [3] J. Colombo, Recent advances in infant cognition: implications for long-chain polyunsaturated fatty acid supplementation studies, Lipids 36 (9) (2001) 919–926. [4] M. Fleith, M.T. Clandinin, Dietary PUFA for preterm and term infants: review of clinical studies, Crit. Rev. Food Sci. Nutr. 45 (3) (2005) 205–229. [5] B. Koletzko, C. Agostoni, S.E. Carlson, T. Clandinin, G. Hornstra, M. Neuringer, et al., Long chain polyunsaturated fatty acids (LC-PUFA) and perinatal development, Acta Paediatr. 90 (4) (2001) 460–464. [6] F. Gottrand, Long-chain polyunsaturated fatty acids influence the immune system of infants, J. Nutr. 138 (9) (2008) 1807–1812. [7] H. Hauner, C. Vollhardt, K.T.M. Schneider, A. Zimmermann, T. Schuster, U. AmannGassner, The impact of nutritional fatty acids during pregnancy and lactation on early human adipose tissue development. Rationale and design of the INFAT study, Ann. Nutr. Metabol. 54 (2) (2009) 97–103. [8] S. Stefanie, M. Daniela, A.G. Ulrike, et al. Sensory and molecular characterisation of human milk odour profiles after maternal fish oil supplementation during pregnancy and breastfeeding, Food Chemistry. 128 (2) (2011) 485–494.
47
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements Stefanie Sandgrubera and Andrea Buettnera,b a
Department of Chemistry and Pharmacy, Food Chemistry, University of Erlangen-Nuremberg, Erlangen, Germany b Fraunhofer Institute for Process Engineering and Packaging (IVV), Freising, Germany
47.1 INTRODUCTION A series of studies on adults demonstrated the protective effects of n-3 polyunsaturated fatty acids (PUFAs) with regard to coronary heart disease, as well as the fact that a diet supplemented with n-3 PUFAs may decrease mortality due to myocardial re-infarction and sudden death. These effects have been attributed to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are present in fish oil, as well as alpha-linolenic acid [1,2]. Besides this, n-3 PUFAs have been shown to be beneficial for fetal and neonatal development with regard to diverse aspects such as vision, cognition, and several others [3–5]. Accordingly, supplementation with (commonly encapsulated) fish oil products during pregnancy and the breastfeeding period has become increasingly popular to provide longchain n-3 PUFAs for improved development of brain and cardiovascular health function [6,7], and is also now a common supplement in everyday diet. Nevertheless, supplementation with such prescriptions repeatedly elicits complaints from consumers/patients about fishy impressions that appear after ingestion of the encapsulated material.
47.2 MATERIALS AND METHODS 47.2.1 Samples Fish oil samples were extracted from the capsules immediately before odorant extraction. Product 1 contained 61 mg DHA and 10 mg vitamin E per g fish oil (n = 14), Product 2 contained 143 mg DHA and V. Ferreira and R. Lopez (Eds): Flavour Science. DOI: http://dx.doi.org/10.1016/B978-0-12-398549-1.00047-7
© 2014 2013 Elsevier Inc. All rights reserved.
245
246
Stefanie Sandgruber and Andrea Buettner
9 mg vitamin E per g fish oil (n = 15), and Product 3 contained 360 mg DHA and 3 mg mixed natural tocopherols per g fish oil (n = 27).
47.2.2 Preparation of Solvent Extracts Each fish oil sample (1–5 g) was extracted with 5 mL dichloromethane (DCM). After extraction (30 min, RT), the fish oil volatiles were isolated by mild solvent assisted flavor evaporation (SAFE; 50°C, 5 × 10−3 Pa). Distillates were dried over anhydrous Na2SO4 and concentrated to a total volume of 100 μL.
47.2.3 Two-Dimensional High Resolution Gas Chromatography-Olfactometry/Mass Spectrometry (2D-HRGC-O/MS) Analyses were performed with a system consisting of two Type 3800 gas chromatographs (Varian, Darmstadt, Germany), coupled with a Saturn 2200 mass spectrometer (Varian) and ODP sniffing ports (Gerstel, Mühlheim, Germany). Mass spectra were generated at 70 eV ionization energy (CI).
47.2.4 Stable Isotope Dilution Assays (SIDAs) Defined amounts of the respective 2H stable isotopically-labeled odorants were added to the samples; then followed the work-up described above. The odorant amounts in fish oil were calculated from the intensity ratios of labeled and unlabeled compounds.
47.2.5 Sensory Analyses Sensory analyses were performed in a sensory panel room at 21±1°C. Fish oil samples (1 g) were presented in covered glass vessels (capacity 140 mL) to the sensory panel for comparative orthonasal evaluation (randomized order, no sample information; as in [8]) with attribute intensity rating on a scale from 0 (no perception) to 3 (strong perception). For the hedonic rating, the panelists were asked to rate pleasantness of the fish oil samples on a scale from 0 (dislike extremely) to 3 (like extremely).
47.2.6 Statistical Analyses Kruskal-Wallis ANOVA was used for multiple comparisons between fish oil products 1, 2, and 3 in orthonasal perception of each odor attribute and for quantitative results for each odorant, with significance level at 0.05.
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements
247
Fishy 3
2 Rancid-oil-like
Fatty
1
0
Tang-like
Oily Product 1
Product 2
Product 3
Figure 47.1 Aroma profile of fish oils (median values).
47.3 RESULTS To characterize the aroma profiles of the investigated fish oils (Figure 47.1), the attributes fishy, fatty, tang-like, oily, and rancid-oil-like, amongst others, were evaluated. At first sight Product 2 appears to stick out because of its dominant fishy odor, but this difference is statistically insignificant (Kruskal-Wallis ANOVA; H(2) = 5.7; P > 0.05). On the other hand, Product 1 shows high mean values according to the more negatively voted attributes tang-like and rancid-oil-like (Kruskal-Wallis ANVAO; H(2) = 0.9, 1.2; P > 0.1 in all attributes). According to this, Product 1 was rated as the “most disliked,” followed by Product 3; Product 2 was evaluated as the “least liked out of all three dislikable choices” (data not shown). Based on comparative aroma extract dilution analysis (data not shown), typical fatty acid oxidation odor substances dominated the odor composition of all three fish oils. Figure 47.2 shows concentrations of selected marker substances, measured by means of stable isotope dilution assays in conjunction with 2D-HRGC-O/MS. In contrast to the aroma profile evaluation, the concentrations between the three products revealed some pronounced differences. Within concentration ranges between 2 and 450 μg/kg, Product 1 consistently
248
Stefanie Sandgruber and Andrea Buettner
Product 1
Product 2
Product 3 n=7 n=5 n=6
Hexanal n=6 n=7 n=6
(Z)-Hept-4-enal
n=6 n=5 n = 11
(E)-Non-2-enal (E,E)-Deca-2,a4-dienal
n=6 n=4 n = 13
n=8 n=8 n = 11
y-Nonalactone n=8 n=8 n=7 n=7 n = 10 n=4
Oct-1-en-3-one (Z)-Octa-1, 5-dien-3-one 0
1
10
100
1000
Conc. [µg/kg]
Figure 47.2 Concentration (logarithmic representation) of potent odorants in investigated fish oil products.
represented the highest amounts of all analyzed volatile compounds except for the aldehyde (Z)-hept-4-enal, which was highest in Product 2. With regard to statistic analysis, the quantification data led to significant differences within all odor compounds (Kruskal-Wallis ANOVA; H(2)=13.3, 17.3, 17.6, 16.6, 19.6, 17.0; P < 0.01 in all odorants).
47.4 DISCUSSION AND CONCLUSION The presented data show that encapsulated fish oil products can vary to a considerable degree. Variance in specific odor attributes from orthonasal aroma profiling as well as the observed quantitative differences in oxidation products between products may explain consumer rejection of certain fish oil supplements.
ACKNOWLEDGEMENT This work was supported by the German Federal Ministry of Education and Research (BMBF). The authors are exclusively responsible for the contents of the publication.
REFERENCES [1] H.C. Bucher, P. Hengstler, C. Schindler, G. Meier, N-3 polyunsaturated fatty acids in coronary heart disease: a meta-analysis of randomized controlled trials, A. J. Med. 112 (4) (2002) 298–304.
Sensory and Molecular Characterization of the Aroma Profiles of Fish Oil Supplements
249
[2] P. Marckmann, M. Grønbæk, Fish consumption and coronary heart disease mortality. A systematic review of prospective cohort studies, Eur. J. Clin. Nutr. 53 (8) (1999) 585–590. [3] J. Colombo, Recent advances in infant cognition: implications for long-chain polyunsaturated fatty acid supplementation studies, Lipids 36 (9) (2001) 919–926. [4] M. Fleith, M.T. Clandinin, Dietary PUFA for preterm and term infants: review of clinical studies, Crit. Rev. Food Sci. Nutr. 45 (3) (2005) 205–229. [5] B. Koletzko, C. Agostoni, S.E. Carlson, T. Clandinin, G. Hornstra, M. Neuringer, et al., Long chain polyunsaturated fatty acids (LC-PUFA) and perinatal development, Acta Paediatr. 90 (4) (2001) 460–464. [6] F. Gottrand, Long-chain polyunsaturated fatty acids influence the immune system of infants, J. Nutr. 138 (9) (2008) 1807–1812. [7] H. Hauner, C. Vollhardt, K.T.M. Schneider, A. Zimmermann, T. Schuster, U. AmannGassner, The impact of nutritional fatty acids during pregnancy and lactation on early human adipose tissue development. Rationale and design of the INFAT study, Ann. Nutr. Metabol. 54 (2) (2009) 97–103. [8] S. Stefanie, M. Daniela, A.G. Ulrike, et al. Sensory and molecular characterisation of human milk odour profiles after maternal fish oil supplementation during pregnancy and breastfeeding, Food Chemistry. 128 (2) (2011) 485–494.