Insight into the Molecular and Structural Changes in Red Pepper Induced by Direct and Indirect Ultrasonic Treatments

Area of Science:

• Food Science and Technology
• Plant Biochemistry
• Ultrasound Applications

Background:

• Ultrasound processing is a non-thermal technology with potential for modifying plant tissues.
• Understanding the differential effects of direct and indirect ultrasound is crucial for optimizing food processing.
• Red bell peppers are rich in bioactive compounds, making them a suitable model for studying ultrasound effects.

Purpose of the Study:

• To comprehensively assess the impact of direct (probe) and indirect (bath) ultrasound on red bell pepper physicochemical and structural properties.
• To investigate how ultrasound parameters influence the release and stability of bioactive compounds.
• To determine the optimal ultrasound mode and duration for preserving tissue integrity and enhancing beneficial compounds.

Main Methods:

• Application of direct and indirect ultrasound under controlled conditions.
• Analysis of chemical composition (polyphenols, flavonoids, carotenoids, vitamin C, sugars).
• Microbiological (TVC, TYM), spectroscopic (FTIR, NMR), thermal (TGA), and microscopic (SEM, micro-CT) evaluations.

Main Results:

• Direct ultrasound induced greater cell wall disruption and enhanced release of polyphenols, vitamin C, and antioxidants.
• Indirect ultrasound preserved cellular integrity and sugar profiles while moderately increasing antioxidant activity.
• Short-term direct sonication boosted antioxidant release; prolonged exposure led to degradation. Ultrasound mode significantly differentiated sample properties.

Conclusions:

• Ultrasound mode and duration are critical factors that can be tailored to modulate tissue integrity and bioactive compound release in red bell peppers.
• Direct ultrasound is effective for rapid extraction of antioxidants, while indirect ultrasound is better for preserving overall quality and composition.
• This study provides insights for optimizing ultrasound-assisted processing of plant-based foods for enhanced nutritional value and quality.