Bigels of oleogel-in-hydrogel structures
were developed as carriers
for curcumin and epigallocatechin gallate (EGCG), and the roles of
oleogelator (glycerol monostearate, GMS) content on the structures
and delivery functionality were elucidated. The results indicated
that hardness and viscosity of the bigels were gradually enhanced
with the increase in GMS content. In the meantime, oil holding capacity
of the bigels was improved, while water holding capacity remained
unchanged. XRD analysis and CLSM observation revealed that higher
GMS content contributed to higher crystallinity and more compact gel
systems. When curcumin and EGCG were incorporated within bigels, their
release could also be modulated by the gel structures. Curcumin was
slowly released in gastric digestion and rapidly released in intestinal
juices. Higher content of GMS led to a much lower release rate of
curcumin. EGCG was quickly released in the gastric juice, and the
release rate was almost constant afterward. GMS content had little
effect on the release of EGCG. The information obtained proved that
bigels could codeliver functional ingredients of different polarities,
whose release could be modulated by gel structures.
Air-assisted sprayers are widely used in orchards for pest and disease control. However, air-assisted spray deposition on the abaxial surface of leaves is often limited. In this study, a method to achieve satisfactory spray deposition on the abaxial leaf surface and an assessment of factors that affect abaxial surface deposition were investigated. The effects of leaf angle, wind speed, platform velocity, and nozzle type were assessed. Abaxial surface coverage was significantly affected by leaf angle, wind speed, and nozzle type, of which the leaf angle had the strongest impact. The leaf angle largely determines the abaxial surface area exposed to the wind field. When the abaxial surface is situated leeward, deposition of droplets on the abaxial surface is difficult. Therefore, to improve abaxial surface exposure for field application, the exposure probability of the abaxial surface at different angles between the leaf and the airflow (α) was examined. The relationship was well represented by a logistic growth curve. The exposure probability exceeded 95% when the α value was greater than 5°. The latter finding was verified by conducting a field application in which the deposition efficiency on the abaxial surface (DEAS) was calculated. Adjustment of the airflow angle based on the theoretical value achieved DEAS of 49.9% and 109.3% in the middle and upper layers of the canopy, respectively, whereas the DEAS was less than 30% if the airflow angle was not adjusted. This is caused by the difference in the exposure probability of the back of the leaf. The results provide a reference for adjustment of the wind field of air-assisted sprayers in field applications.
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