Antioxidant effect of natural plant extracts on the microencapsulated high oleic sunflower oil

https://doi.org/10.1016/j.jfoodeng.2007.05.029Get rights and content

Abstract

This study demonstrates that natural plants extract (NPE) such as rosemary, broccoli sprout and citrus can effectively inhibit the lipid oxidation of microencapsulated high oleic sunflower oil (MEHS). By employing a dextrin-coating method with supplements such as milk protein isolates (MPI), soy lecithin and sodium triphosphate emulsifier in the presence of NPE, MEHS with high microencapsulation efficiency was obtained. Similar to that of high oleic sunflower oil (HS) in liquid state, lipid oxidation of MEHS was remarkably reduced under the accelerated storage condition in the presence of a mixture of NPEs rather than a single component of NPE. Specifically, induction period of MEHS was significantly elongated in the presence of NPE when tested by using the Rancimat method, and the peroxide value (POV) and p-anisidine value (ASV) were also significantly lowered by addition of NPE even after storage for 30 days at 60 ± 1 °C. Based on the results, it is anticipated that NPEs find wide applications as an antioxidant for the elevated quality of microencapsulated oil products in food industries.

Introduction

Lipids in seed oils are important functional components of foods and have a significant effect on the quality of foods even though they constitute a minor component. They not only contribute to flavor, odor, color and texture, but also confer a feeling of satiety and palatability to foods. However, the major problem in these oils lies in lipid oxidation during storage or food processing (Frankel, 1998), which can lead to the rancidity (Gordon, 1991) and defective nutrition due to degradation products such as reactive oxygen species, resulting in harmful effects on human health (Esterbauer et al., 1991, Guardiola et al., 2002, Sanders, 1983).

Recently, many attempts have been made to prevent the oxidative deterioration of lipids by using natural antioxidants (Chaudiere, 1994, Frankel, 1998, Frankel et al., 1994, Gordon, 1990). Some components in natural products such as carotenoids, flavonoides, anthocyanins and phenolic compounds are known to function as scavengers in both primary and secondary oxidation process. In particular, it has been reported that potential antioxidants exist in a number of natural plant extract (NPE) including grapes (Lapidot, Harel, Akiri, Granit, & Kanner, 1999), green teas (Frankel, Huang, Aeschbach, & Prior, 1997), berries (Nielsen, Haren, Magnussen, Dragsted, & Rasmussen, 2003), tomatoes (Gahler, Otto, & Böhm, 2003) and rosemary (Frankel et al., 1996, Richheimer et al., 1996). Although antioxidant effect of rosemary was extensively investigated on various samples (Banias et al., 1992, Wada and Fang, 1992), little information is available about the combined effect with other NPEs on the seed oils. Furthermore, no study on the combined antioxidant effect of natural plant extracts such as citrus, broccoli sprout, and palm oil extract on the various seed oils has been carried out.

Another approach to protect lipid from oxidation is to microencapsulate the lipid products, which has been widely used in manufacturing powder-type oil and fat products (Keogh and O’Kennedy, 1999, Rosenberg and Lee, 1993, Rosenberg and Young, 1993). Microencapsulation can provide more prolonged shelf-life by protecting oils with encapsulating agent such as milk protein or dextrin, etc. By choosing the appropriate materials to enclose small oil particles, core components such as oil can be protected from deterioration due to adverse environmental conditions such as light, moisture and oxygen, resulting in the increase of the shelf-life of the product (Shahidi & Han, 1993). Although microencapsulation can protect seed oils from oxidation, severe lipid oxidation on the surface of the microcapsule could also occur due to high temperature during the spray-drying process and the residual oils on the surface. However, there have been few studies regarding prevention of lipid oxidation of residual free fat on the surface of microcapsules by using natural antioxidants. Shelf-life of edible oils is normally predicted from the accelerated storage tests which are usually conducted at high temperature ranging from 60 °C for the Schaal oven test to 100 °C for the Rancimat test (Frankel, 1998, Makhoul et al., 2006). While the shelf-life of sunflower oil was well assessed by measuring the rancidity (Makhoul et al., 2006), no study on lipid oxidation of sunflower oil in microcapsules has been reported. In this regard, the use of proper antioxidants is required even for microencapsulation of relatively stable HS.

In this report, the effect of NPEs such as rosemary, broccoli sprout, and citrus on the oxidation of microencapsulated high oleic sunflower oil (MEHS) is demonstrated. High oleic sunflower oil (HS) is increasingly used owing to relatively high stability, but vulnerability of MEHS to oxidation has hampered its widespread use. A single component or a mixture of NPEs were tested regarding their antioxidant effects on the MEHS.

Section snippets

Materials

Rosemary extract (Rosmarinus officinalis) was supplied from FLAVEX (Lehlingen, Germany), broccoli sprout extract (Brassica oleracea var. italica) was supplied from ORYZA (Ichinomiya, Japan), citrus extract mixture (Citrus Aurantium dulcis, Citrus Aurantium amara and Citrus paradisi) was supplied from BREKO (Bremen, Germany) and palm oil extract (Elaeis Guineensis) was supplied from Carotech (Perak, Malaysia). CO (Corn oil of Zea mays), SO (Sunflower oil of Helianthus annuus) and HS (High oleic

Results and discussion

High oleic sunflower oil (HS) was microencapsulated by using a dextrin-coating method with supplements such as milk protein isolates (MPI), soy lecithin, and sodium triphosphate emulsifier. It was well documented that milk protein and dextrin are a good wall material for microencapsulation of oils (Keogh & O’Kennedy, 1999) and light core material such as flavors (Trubiano & Lacourse, 1988), respectively. In this study, dextrin was employed as a main coating agent by taking into consideration

Acknowledgements

The authors thank to Yeo K.M., Kim B.J. and Ahn S.Y. for their skillful technical assistance for microencapsulation.

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