Development, Characterization, and Stability of O/W Pepper Nanoemulsions Produced by High-Pressure Homogenization

Abstract

Interest in the utilization of bioactive plant compounds in foods has increased due to their biochemical activities (antioxidant, antimicrobial, etc.), and as alternatives in the reduction of the use of high concentrations of chemical substances. However, some of these additives are hydrophobic, thus being harder to disperse into the food matrix, which is generally water-based. A good alternative is the use of low concentrations of these compounds as nanoemulsions. The objective of the present study was to develop oil-in-water nanoemulsions containing Bdedo-de-moça^pepper extract for food applications. Research in the development of these nanoemulsions was carried out using a high-speed homogenizer, followed by a high-pressure homogenizer. The influence of the following parameters was assessed: type and concentration of surfactants, hidrophilic-lipophilic balance, lipid/ aqueous phase ratio, surfactant/oil ratio, pepper extract composition in nanoemulsion, and processing conditions. Nanoemulsions were evaluated by environmental (centrifugal and thermal) and storage stabilities, characterized by average droplet size and ζ-potential measurements, color, interfacial tension, atomic force, and cryo-scanning electron microscopy. Those with average droplet size between 132 ± 2.0 and 145 ± 1.0 nm were developed depending on working pressure a n d n u m b e r o f c y c l e s ; ζ-p o t e n t i a l w a s a r o u n d − 36.71 ± 0.62 mV and the best nanoemulsion was stable to centrifugation and most of the thermal stresses. Droplets were characterized with cryo-scanning electron microscopy as being spherical, homogeneous, and stable, and remained stable when stored at 4°C and room temperature for over 120 days. The pepper nanoemulsion, developed in the present study, has potential applications in the food industry.

Nanoemulsions: Using emulsifiers from natural sources replacing synthetic ones—A review

“…It is the most often used technique for NE preparation, where a mixture of oil, water, emulsifiers is passed through a tight valve at an appropriate level of homogenization pressure (50 to 100 MPa). High-pressure homogenization (HPH) is an instrumental technique existing for industrial applications (Alexandre, Lourenço, Bittante, Moraes, & Sobral, 2016;Galvão, Vicente, & Sobral, 2018). Turbulence and cavitation are the two main phenomena that explain the conversion of large droplets to smaller ones.…”

“…HPH needs a premixing step to prepare a coarse emulsion (using conventional rotor-stator homogenizer) (Dammak & Sobral, 2017;Galvão et al, 2018). When the coarse emulsion passes across the valve, it undertakes, severe disruptive forces that produce nanosize droplets dispersed in the continuous phase.…”

Investigation of food microstructure and texture using atomic force microscopy: A review

“…Nanoemulsion was suggested to increase pepper extract availability. The irregular shape of this nanoemulsion, observed by AFM, provided clues to potential reaction mechanisms (Galvo, Vicente, & Sobral, 2018). Solid lipid nanoparticles have been widely investigated as delivery systems for hydrophobic ingredients.…”

Nanoemulsions: Synthesis, Characterization, and Application in Bio‐Based Active Food Packaging

“…Cryogenic scanning electron microscopy (cryo‐SEM) and transmission (cryo‐TEM) electron microscopy, which have been utilized in this regard, have provided complementary information, the former being more useful for a three‐dimensional observation of relatively large droplets (Lee et al., ). Dried, and sometimes diluted atomic force microscopy (AFM) may also provide useful information concerning the size and morphology of nanodroplets in emulsion (Dario et al., ; Galvão, Vicente, & Sobral, ). Nonetheless, different imaging techniques have been proposed to investigate the morphological aspects of nanoemulsions, for instance, confocal laser scanning microscopy (Gani & Benjakul, ), and a combination of X‐ray computed tomography imaging with near‐infrared fluorescent imaging (Chen et al., ).…”