Abstract
Nanoemulsions are feasible delivery systems of lipophilic compounds, showing potential as edible coatings with enhanced functional properties. The aim of this work was to study the effect of emulsifier type (stearic acid (SA), Tween 80 (T80) or Tween 80/Span 60 (T80/S60)) and emulsification process (homogenization, ultrasound or microfluidization) on nanoemulsion formation based on oxidized corn starch, beeswax (BW) and natural antimicrobials (lauric arginate and natamycin). The response variables were physicochemical properties, rheological behavior, wettability and antimicrobial activity of BW–starch nanoemulsions (BW–SN). The BW–SN emulsified using T80 and microfluidized showed the lowest droplet size (77.6 ± 6.2 nm), a polydispersion index of 0.4 ± 0.0 and whiteness index (WI) of 31.8 ± 0.8. This BW–SN exhibited a more negative ζ-potential: −36 ± 4 mV, and Newtonian flow behavior, indicating great stability. BW–SN antimicrobial activity was not affected by microfluidization nor the presence of T80, showing inhibition of the deteriorative fungi R. stolonifer, C. gloeosporioides and B. cinerea, and the pathogenic bacterium S. Saintpaul. In addition, regardless of emulsifier type and emulsification process, BW–SN applied on the tomato surface exhibited low contact angles (38.5° to 48.6°), resulting in efficient wettability (−7.0 mN/m to −8.9 mN/m). These nanoemulsions may be useful to produce edible coatings to preserve fresh-produce quality and safety.
Highlights
The food industry is consistently looking for innovative technologies to improve quality, safety and functional properties of food products [1]
To overcome solubility limitations of lipophilic ingredients, nanoemulsions have been proposed as suitable delivery systems [5]
The thermal behavior of BW was evaluated through the differential scanning calorimetry (DSC) thermogram (Figure 1), in which the exothermic process was used to estimate the crystallization onset temperature (Toc) that was 61.47 ± 0.02 ◦C
Summary
The food industry is consistently looking for innovative technologies to improve quality, safety and functional properties of food products [1]. The incorporation of hydrophobic agents such as beeswax (BW) into polysaccharides or protein suspensions is a potential food-packaging alternative to prevent water loss and to improve appearance of fresh produce when applied as edible coatings [3,4]. Oil-in-water (O/W) nanoemulsions consist of small lipid droplets (10–100 nm in diameter) dispersed in an aqueous continuous phase. Their low particle size provides slight turbidity, being suitable for a wide range of food applications [6,7]. Nanoemulsions are metastable systems because of the surface free energy required to increase the interfacial area between oil and water phases, and tend to break down over time due to gravitational separation and droplet aggregation [9,10]. This study aimed to evaluate the type of emulsifier and the influence of processing parameters on the physicochemical, rheological, wettability and antimicrobial properties of nanoemulsions containing beeswax (BW) and oxidized starch (OS), added with natural antimicrobials
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