Natural nano-emulsions: A sustainable solution for rice weevil control in stored paddy rice

Abstract

Nanoemulsion technology offers a promising method to enhance the absorption and effectiveness of various active compounds. This study specifically developed nanoemulsions of frankincense, turmeric, and sesame oil to assess their impact on paddy rice. Notably, there is a lack of research examining both the efficacy and long-term effects of nanoemulsion treatments on rice quality, as most existing studies focus primarily on immediate harmful effects or repellent capabilities without considering prolonged impacts. This research is pioneering in exploring how nanoemulsion treatments influence the physical and chemical properties, nutritional value, and overall quality of paddy rice, as well as their effects on the rice weevil, (Sitophilus oryzae L., Coleoptera: Curculionidae). Nanoemulsions were prepared using a high-energy ultrasonication process and characterized by transmission electron microscopy, revealing spherical particles ranging from 27 to 34 nm in diameter. The formulations exhibited kinetic stability, slight acidity (pH 5.0–6.33), and favorable physicochemical properties including zeta potential (−31.6 to −15.2 mV), viscosity (27–34 cP), and surface tension (28.12–53.59 dyne/cm). The nanoemulsions were applied to paddy rice of the Sakha 108 cultivar at concentrations of 500, 1500, and 2000 μL/kg. Over 9 months of storage, the sesame nanoemulsion at 2000 μL/kg significantly improved milling quality (71.78% vs 70.23% in controls), hardness (7.25 N vs 5.40 N), and cooking properties. It also enhanced nutritional content, increasing vitamin B3 to 51.12 mg/kg (vs 44.63 mg/kg in controls), potassium to 1149 mg/kg (vs 1113 mg/kg), and phosphorus to 1133 mg/kg (vs 1064 mg/kg). The nanoemulsions demonstrated robust insecticidal effects against S. oryzae. The turmeric formulation at 2000 μL/kg achieved 100% adult mortality after two weeks and complete inhibition of progeny emergence over 9 months. Sesame and frankincense nanoemulsions at the same concentration resulted in 90% and 83.33% mortality, respectively, after two weeks. These findings demonstrate the potential of nanoemulsion technology as an environmentally friendly alternative to conventional chemical treatments for maintaining rice quality and providing effective pest control during long-term storage.