Lipid Oxidation in Emulsions Fortified with Iron-Loaded Alginate Beads

Abstract

The potential use of iron-loaded alginate beads to fortify oil-in-water (O/W) emulsions was studied. Iron-loaded alginate beads with different sizes (0.65, 0.84, 1.5 and 2 mm) were produced by ionic gelation with calcium chloride, leading to 81% encapsulation efficiency (EE) of ferrous sulfate. These beads were added to O/W emulsions to investigate their effect on lipid oxidation. The use of iron-loaded alginate beads inhibited lipid oxidation in emulsions, compared to a control emulsion with the same concentration of free ferrous sulfate in the continuous phase, but did not totally prevent it. Results obtained with scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX) analysis showed that some reactive iron was present at the surface of the beads. Oxidation of the lipid droplets was slightly higher for smaller alginate beads, suggesting that the reaction could be linked to the total bead surface. When covering iron-loaded beads with an extra layer of alginate, lipid oxidation was inhibited, which confirmed the role of reactive surface-bound iron. This study shows that the location of iron within the encapsulates plays a crucial role in the chemical stability of fortified foods and should be taken as a starting point in the design of iron-fortified food products.

Effects often overlooked in lipid oxidation in oil‐in‐water emulsions: Agitation conditions and headspace‐to‐emulsion ratio

“…The zeta potential of all emulsions was strongly negative (Figure S3b), as reported by others for emulsions stabilized by non‐ionic surfactants such as polysorbates (Berton et al, 2011; Cengiz et al, 2019). Stripped rapeseed oil and fresh emulsions containing iron had a low amount of free fatty acids (acid value), 0.03 mg/g oil and 0.08 mg/g oil, respectively (Table 1).…”

“…After 8 days of incubation at 25 C, the FFA content of all emulsions increased, with some differences depending on agitation method and headspace-to-emulsion ratio. This indicates that triglycerides are limitedly hydrolysed into FFAs (Cengiz et al, 2019). The emulsion incubated in immobile conditions had the lowest FFA content of 0.51 mg/g oil at the end of the incubation period, whereas both rotated and shaken emulsions had similar values around 0.90 mg/g oil, and emulsions with larger headspace (88% [vol/vol] headspace) had the highest FFA content (1.21 mg/g oil), compared to the 12% and 56% (vol/vol) headspace emulsions ($0.97 mg/g oil).…”

“…Another possible explanation for the formation of free fatty acids, and drop in pH is the degradation of the polysorbate (Tween 20) by hydrolysis of the fatty acid ester bond, or oxidation of the polyethylene oxide (POE) chains leading to generation of short chain acids such as formic acid, and various other components such as aldehydes, acids, and ketones (Kerwin, 2008;Kishore et al, 2011), and even trace amounts of fatty acids (Tomlinson et al, 2015). In general, these FFAs have low solubility in water, yet it may be enhanced by the presence of Tween 20 (Cengiz et al, 2019). Formation of weak acids may occur through degradation of hydroperoxides, yet this is most probably not the cause for the pH drop, since the formation of hydroperoxides T A B L E 1 Average particle size, zeta potential, pH and acid value in stripped rapeseed oil, and in emulsions freshly prepared or after 8 days of incubation under various agitation conditions and volume of headspace at 40 C.…”

Microencapsulated iron in food, techniques, coating material, efficiency, and sensory analysis: a review

“…These characteristics can be beneficial for the iron absorption because the duodenum has a similar pH (Yao et al, 2020). Perez-Moral et al (2013) and Cengiz et al (2019) performed simulations under gastrointestinal conditions under progressive release; in gastric conditions 45% was absorbed, a retention in the gastrointestinal tract of 43% and in duodenal conditions 12%; however, gels limit fortification in some food matrices (flours and powders) (Onsekizoglu Bagci and Gunasekaran, 2016) making it difficult to control the particle size, which usually varies between 3 and 5 nm (Katuwavila et al, 2016).…”

Standardized methods for testing the quality attributes of plant‐based foods: Milk and cream alternatives

“…The particles may first be collected by centrifugation or TA B L E 1 Methods for expressing the particle concentration in colloidal dispersions, such as plant-based milks filtration and then analyzed using proximate analysis (e.g., fat, protein, carbohydrate, ash, and moisture content) or elemental analysis (e.g., atomic absorption, nitrogen analysis, or X-ray scattering). Alternatively, chemical microscopy methods can be used, such as energy-dispersive X-ray spectroscopy combined with scanning electron microscopy (SEM), which provides information about the elemental composition of different regions of a microscopy image (Cengiz et al, 2019).…”