Effects of High-Pressure Processing on the Microstructure and Bioactive Compound Retention of Moringa Leaf Extract

High-pressure processing is a non-thermal preservation technology that inactivates microorganisms and enzymes while minimising the thermal degradation of heat-sensitive bioactive compounds. Moringa oleifera leaf extract contains high concentrations of glucosinolates, isothiocyanates, and polyphenols that are susceptible to thermal degradation, making non-thermal processing particularly relevant for its preservation. This study evaluates the effects of high-pressure processing at 200, 400, and 600 MPa for 5, 10, and 15 minutes on the microstructure, microbial inactivation, and bioactive compound retention of Moringa leaf extract prepared from leaves sourced in Kaduna, North West Nigeria. Microstructural changes were evaluated by scanning electron microscopy and confocal laser scanning microscopy. Total phenolic content, total flavonoid content, glucosinolate content, antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl and oxygen radical absorbance capacity assays, and total viable count were determined before and after treatment. Results showed that 400 MPa for 10 minutes achieved a 4-log reduction in total viable count while retaining 92 percent of total phenolic content and 88 percent of glucosinolate content, compared to 63 percent and 56 percent retention respectively at equivalent microbial reduction achieved by pasteurisation at 80 degrees Celsius. Microstructural analysis confirmed cell disruption that improved extractability of intracellular compounds at 400 MPa. The study draws on recent high-pressure processing literature for plant-based food systems. Findings contribute to the evidence base for high-pressure processing of Nigerian functional food ingredients. Keywords: high-pressure processing, Moringa, bioactive compounds, non-thermal, glucosinolates