Impact of an integrated piston-gap and microfluidic high-pressure homogenization system on the stability and quality of lemon emulsions

Lemon emulsion, enriched with vitamin C, organic acids, and dietary fiber, is widely utilized in food applications due to its refreshing flavor and associated health benefits. However, traditional pasteurization (PT) techniques commonly employed to prolong shelf life often lead to nutrient degradation and sensory deterioration. This study investigates the impact of a high-pressure homogenization system integrating piston-gap and microfluidic technologies (IPM-HS) on the quality and stability of lemon emulsions. Emulsions composed of fresh lemon juice, olive oil, and Tween 80 were treated at 200, 300, and 400 MPa. The IPM-HS treatment significantly enhanced turbidity (up to 1.5-fold), reduced particle size below 500 nm, and achieved effective microbial reduction, with no viable microorganisms detected at any pressure level. In addition, EAI and ESI values increased significantly with pressure, indicating enhanced emulsifying capacity and long-term physical stability. Zeta potential measurements showed more negative values after IPM-HS treatment, suggesting improved electrostatic repulsion and greater emulsion stability. The L* value increased markedly from 62.39 to 89.81 at 400 MPa, indicating a shift in color from light yellow to milky white. Emulsions treated with IPM-HS exhibited stable nanostructures with no phase separation during 30-day storage, in contrast to untreated and thermally treated controls. Moreover, total phenolic content increased from 0.49 to 0.58 mg GAE/g ( p  < 0.05), and antioxidant activity was well preserved. Flavor analysis using electronic tongue and nose revealed minimal deviation from the control group. Overall, IPM-HS markedly improves emulsion stability, physicochemical quality, and nutritional retention while maintaining sensory attributes, underscoring its potential as a promising non-thermal processing technology for emulsion-based product development.