Research Article The antioxidative effect of lipophilized rutin and dihydrocaffeic acid in fish oil enriched milk Ann-Dorit Moltke Sørensen 1 , Lone Kirsten Petersen 1 *, Sara de Diego 2 **, Nina Skall Nielsen 1 , Bena-Marie Lue 3 ***, Zhiyong Yang 3 , Xubing Xu 3 and Charlotte Jacobsen 1 1 Division of Industrial Food Research, National Food Institute, Technical University of Denmark, Lyngby, Denmark 2 Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain 3 Department of Engineering, Aarhus University, A ˚ rhus, Denmark The antioxidative effect of phenolipids was evaluated in fish oil enriched milk emulsions as a model for a complex food system. Two different phenolipids modified from dihydrocaffeic acid (with C8 or C18:1) and rutin (with C12 or C16) were evaluated. Both dihydrocaffeate esters and rutin laurate showed significantly better antioxidant properties in milk emulsion compared with the original phenolics. However, rutin palmitate only performed slightly better as antioxidant than rutin. The results with rutin indicated that a cut-off effect exists in relation to the alkyl chain length with respect to optimal antioxidant activity in milk emulsions. Thus, the optimal alkyl chain length is at least below 16 carbon atoms, and maybe even less for rutin esters. For dihydrocaffeate esters it was not possible to conclude on a cut-off effect in relation to alkyl chain length and antioxidative effect due to the almost similar antioxidant effect of the two phenolipids. However, there was a tendency towards octyl dihydrocaffeate being slightly more efficient than oleyl dihydrocaffeate. Practical application: The finding that phenolipids are better antioxidants in milk emulsions than the original phenolic acid provides new knowledge that can be used to develop new antioxidant strategies to protect foods against lipid oxidation. However, the results indicate that both optimization of alkyl chain length for each type of phenolic, and optimization for each type of emulsion will be necessary in order to get the best oxidative stability of an emulsion with these phenolipids. Use of efficient antioxidants may lower the amount of antioxidant needed to protect against lipid oxidation and may in addition decrease the costs. Keywords: Caffeic acid / o/w Emulsion / Polar paradox / Rutin Received: October 10, 2011 / Revised: January 9, 2012 / Accepted: February 24, 2012 DOI: 10.1002/ejlt.201100354 1 Introduction The health beneficial effects of n-3 long chain PUFA (LC PUFAs) such as, e.g. reduced risk of cardiovascular diseases are well documented. During the last decade substantial efforts have been put into enriching foods with the healthy n-3 LC PUFAs as reviewed by Jacobsen et al. [1] These efforts have been carried out in order to increase the popu- lations’ intake of especially eicosapentaenoic acid (EPA) and DHA [2, 3]. Despite the increasing number of n-3 PUFA enriched foods on the market, consumer acceptance and shelf-life of such products are still limited by the higher oxidative susceptibility of unsaturated lipids, which will lead to an unpleasant fishy off-flavour [4–7]. To retard lipid oxi- dation, a range of commercial synthetic antioxidants with free radical scavenging activity and metal chelating properties are *Current address: CP Kelco ApS, Ved banen 16, DK-4623 Lille Skensved, Denmark **Current address: Grupo Siro, Paseo Pintor Rosales 40, Madrid, Spain ***Current address: Novozymes A/S, Krogshoejvej 36, DK-2880 Bagsvaerd, Denmark Correspondence: Dr. Ann-Dorit Moltke Sørensen, Division of Industrial Food Research, National Food Institute, Technical University of Denmark, Søltofts Plads, Building 221, DK-2800 Kgs. Lyngby, Denmark E-mail: [email protected]Fax: þ45 4588 4774 Abbreviations: ATD, automatic thermal desorber; BHT, butylated hydroxytoluene; DHCA, dihydrocaffeic acid; DHCA C18:1, oleyl dihydrocaffeate; DHCA C8, octyl dihydrocaffeate; EPA, eicosapentaenoic acid; LC, long chain; PV, peroxide value; Rutin C12, rutin laurate; Rutin C16, rutin palmitate 434 Eur. J. Lipid Sci. Technol. 2012, 114, 434–445 ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com
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Research Article
The antioxidative effect of lipophilized rutin anddihydrocaffeic acid in fish oil enriched milk
Ann-Dorit Moltke Sørensen1, Lone Kirsten Petersen1*, Sara de Diego2**, Nina Skall Nielsen1,
Bena-Marie Lue3***, Zhiyong Yang3, Xubing Xu3 and Charlotte Jacobsen1
1 Division of Industrial Food Research, National Food Institute, Technical University of Denmark, Lyngby,
Denmark2 Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain3 Department of Engineering, Aarhus University, Arhus, Denmark
The antioxidative effect of phenolipids was evaluated in fish oil enriched milk emulsions as a model for a
complex food system. Two different phenolipids modified from dihydrocaffeic acid (with C8 or C18:1) and
rutin (with C12 or C16) were evaluated. Both dihydrocaffeate esters and rutin laurate showed significantly
better antioxidant properties inmilk emulsion compared with the original phenolics. However, rutin palmitate
only performed slightly better as antioxidant than rutin. The results with rutin indicated that a cut-off effect
exists in relation to the alkyl chain length with respect to optimal antioxidant activity in milk emulsions. Thus,
the optimal alkyl chain length is at least below 16 carbon atoms, and maybe even less for rutin esters. For
dihydrocaffeate esters it was not possible to conclude on a cut-off effect in relation to alkyl chain length and
antioxidative effect due to the almost similar antioxidant effect of the two phenolipids. However, there was a
tendency towards octyl dihydrocaffeate being slightly more efficient than oleyl dihydrocaffeate.
Practical application: The finding that phenolipids are better antioxidants in milk emulsions than the
original phenolic acid provides new knowledge that can be used to develop new antioxidant strategies to
protect foods against lipid oxidation. However, the results indicate that both optimization of alkyl chain
length for each type of phenolic, and optimization for each type of emulsion will be necessary in order to get
the best oxidative stability of an emulsion with these phenolipids. Use of efficient antioxidantsmay lower the
amount of antioxidant needed to protect against lipid oxidation and may in addition decrease the costs.
The values were calculated according to the control emulsions from the respective experiment.a) For development of 1-penten-3-one the inhibition percentages were calculated at the day with highest concentration before decreasing, that
means that it was calculated at day 9 for experiment 1 and day 6 for experiment 2.b) This indicate that the specific volatile was not detected in this emulsion and therefore the inhibition percentage was not calculated.
Eur. J. Lipid Sci. Technol. 2012, 114, 434–445 Antioxidant efficacy of lipophilized phenolics 441
i.e. close to the interface instead of as a micelle in the water
phase or in the core of the oil droplets. A similar explanation
could be given for the differences observed with oleyl dihy-
drocaffeate. However, further research is needed in order to
be able to conclude on possible interaction in the milk and
changed partitioning of the phenolipids as a consequence of
the interaction.
4.3 Fish oil enriched milk and human health
Overall it was possible to stabilize fish oil enriched milk by
adding phenolipids. The current amount of fish oil in this
milk will only be a supplement of n-3, since 500 mL milk
daily will result in an intake of 50 mg EPA and DHA. EU
recommendation is currently at an intake of 250 mg daily due
to proved health beneficial effects, thus 500 mL milk daily
will cover 20% of the recommendeted. Consumption of n-3
enriched milk solely may not increase the human health, but
together with other fish or fish oil enriched products.
5 Conclusions
In conclusion, both phenols and phenolipids acted as anti-
oxidants in milk emulsions enriched with fish oil. However,
the phenolipids were more efficient antioxidants especially
rutin laurate, octyl and oleyl dihydrocaffeate. Despite the fact
that only two chain lengths were evaluated, the results tend to
follow the cut-off effect in relation to alkyl chain length and
antioxidative effect for rutin esters. The optimal alkyl chain
length for a rutin ester in fish oil enrichedmilk is at least below
a chain length of 16 carbon atoms. For dihydrocaffeate esters
it was not possible to conclude on a specific cut-off effect in
relation to alkyl chain length and antioxidative effect. To be
able to conclude on the optimal lipid chain length attached to
the phenolic compounds in relation to their strongest anti-
oxidant protection, more studies on the effect of rutin and
dihydrocaffeic acid with different lipid chain lengths are
needed. The antioxidative effect of phenolipids seems quite
complex and it would be of great value to be able to under-
stand the effects of both the lipid chain length and the type of
emulsion system on the antioxidative effect of the lipophilized
compounds. Taken together, these results clearly show that the
polar paradox hypothesis is too simple and must be reconsid-
ered. Moreover, the almost untouched area of phenolipids as
antioxidants in real food systems deserves more attention as the
results have indicated very promising effects of these com-
pounds that could be utilized by the industry in the future.
We thank Maritex Norway (subsidiary of TINE BA, Norway)
for providing the fish oil to our research. The study was financed by
the Danish Council for Strategic Research (Programme committee
for food, nutrition and health) and the Directorate for food,
Fisheries and Agri Business.
The authors have declared no conflict of interest.
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