Oxidative stability of n-3 fatty acids encapsulated in filled hydrogel particles and of pork meat systems containing them

Highlights

• Filled hydrogel particles (FHP) were manufactured as n-3 fatty acids delivery system.

• Lipid oxidation as affected by storage and heating in delivery system was assessed.

• FHP showed lower oxidation rates as compared with a conventional delivery system.

• Meat system containing FHP showed good oxidative stability over the storage time.

• FHP may be used as ingredient to produce n-3 fatty acids enriched meat products.

Abstract

The effect of storage time (2 °C, 19 days) and heating (70 °C, 30 min) on physical characteristics and oxidative stability of fish oil encapsulated in filled hydrogel particles was determined and compared with a conventional oil-in-water (O/W) emulsion with the same oil content (8.5%). Subsequently they were used to enrich meat systems with n-3 LCPUFAs, and their lipid oxidation was evaluated and compared with two other meat systems: one containing all animal fat and another with fish oil added directly. Filled hydrogel particles were more effective in lowering the oxidation rate than O/W emulsion, even when thermal treatment was applied. Oxidative stability over the storage time was best in the n-3 LCPUFA-enriched meat system containing filled hydrogel particles, in which TBARS levels were up to 62% lower than other systems containing fish oil. Hydrogel particles offer a promising means of controlling lipid oxidation in n-3 LCPUFA-enriched meat products.

Introduction

Health benefits provided by consumption of n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA), especially eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, have been widely documented. Indeed, most nutritional guidelines now include recommendations to increase the intake of n-3 LCPUFA (Aranceta & Pérez-Rodrigo, 2012). However, dietary intake of these fatty acids is generally low in western societies due to low consumption of the richest sources (fish oil and seafood) (Meyer, 2011). One possible strategy for enhancing the intake of these fatty acids is to develop food products fortified with fish or algae oil, the most abundant and cheapest sources of EPA and DHA. Nevertheless, although attractive, this alternative has a drawback in the high oxidative instability of n-3 LCPUFA. Lipid oxidation of LCPUFA-rich foods is a serious problem that often negatively affects shelf-life, consumer acceptability, functionality, nutritional value and safety (Arab-Tehrany et al., 2012). Providing the means to deliver n-3 LCPUFA effectively to the body through food therefore requires novel approaches.

Emulsion technology is particularly suited to the design and fabrication of delivery systems for encapsulating bioactive lipids such as n-3 LCPUFA. Oil-in-water (O/W) emulsions are the most common type of emulsion-based systems for delivery of bioactive lipids because of their relative ease of preparation and low cost. However, O/W emulsions have limited potential in terms of their ability to afford bioactive protection. This has led to the development of more complexly-structured emulsions such as filled hydrogel particles. These systems consist of oil droplets (O) trapped inside a hydrogel matrix (W₁), which is dispersed in an aqueous medium (W₂) that may be described as an O/W₁/W₂ type of structured emulsion (Matalanis & McClements, 2013). Filled hydrogel particles have the potential to provide certain benefits over conventional O/W emulsions, such as enhanced stability, or targeted delivery in the body (McClements, Decker, & Weiss, 2007). In this connection it has been reported that the lipid material present in filled hydrogel particles is highly accessible for digestion and absorption in the body and therefore this delivery system would be appropriate for incorporating lipid-based bioactives in foods (Matalanis & McClements, 2012b). Nevertheless, there is still significant room for improvement, particularly in the area of increasing lipid loading capacity and particle yields (Matalanis & McClements, 2013). Thus, such delivery systems, designed to make an important contribution to dietary n-3 LCPUFA recommended intakes, may be incorporated in real foods.

LCPUFA enrichment is especially challenging in meat products. High concentrations of prooxidants (e.g. transition metal and haeme-containing proteins), meat processing operations like grinding and thermal treatment, and addition of potential prooxidant ingredients (e.g. sodium chloride) are conditions that reduce oxidative stability (Lee, Decker, Faustman, & Mancini, 2005).

Other omega-3 delivery systems have been tested in meat systems. However, to our knowledge, the ability of filled hydrogels to protect omega-3 fatty acids in meats has not been tested. The filled hydrogels used in this study could have several advantages for meat systems because they are structurally more robust than conventional emulsions (Matalanis & McClements, 2012b) and thus the integrity of the particle is more likely to survive the thermal processing of meats. In addition, the filled hydrogels used in this study are stabilized with casein and pectin. These biopolymers could potentially play a due role in both physically and chemically stabilizing the omega 3 fatty acids since both proteins and anionic polysaccharides have been reported to have antioxidant activity (Chen et al., 2010, Elias et al., 2008). Therefore the goals of this study were (1) to assess physical characteristics and oxidative stability of filled hydrogel particles (fresh and heated 70 °C/30 min), that contain nutritionally significant amounts of n-3 LCPUFA when used as a food ingredient. This system was compared with an O/W emulsion containing the same type and amount of lipid material. (2) To evaluate the lipid oxidation of n-3 LCPUFA-enriched pork meat systems by incorporation of fish oil added in three different ways: (a) directly; (b) stabilized in a O/W emulsion; and (c) stabilized in filled hydrogel particles. These were compared with a pork meat system containing all animal fat. The influence of chilled storage (19 days at 2 ± 2 °C) was also considered.