Comparing the Effects of Enzyme and Fermentation Pre-Treatments on the Chemical, Antioxidant and Sensory Properties of Beetroot Juices

Ong, Ai Qi (2026) Comparing the Effects of Enzyme and Fermentation Pre-Treatments on the Chemical, Antioxidant and Sensory Properties of Beetroot Juices. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

Text Ong Ai Qi_Full Text.pdf Restricted to Registered users only Download (6MB)

Abstract

Beetroot has gained popularity in health-conscious markets for its bioactive compounds and dietary nitrate. While many studies have optimized juice yield and bioactive retention, few have addressed the sensory properties of the extracted beetroot juice—which are crucial for consumer acceptance. This study compared the effects of enzymatic and fermentation pre-treatments on the chemical, bioactive and sensory properties of the extracted beetroot juice. Beetroots were processed into paste and subjected to four treatments: amylase, pectinase, Lacticaseibacillus casei ATCC393 and Monascus purpureus fermentation, with untreated samples as control. Juices were extracted using ultrasound and squeezed with cheesecloth. Juice yield, pH, colour, total phenolic content, total flavonoid content, antioxidant activities (ABTS, DPPH, FRAP), nitrate content and betalain content were measured whereas sensory evaluation on odour, vibrancy and hue were conducted. Enzymatic pre-treatments did not significantly improve juice yield or phenolic and flavonoid recovery compared to control, likely due to matrix-related limitations. Conversely, fermentation with L. casei and M. purpureus significantly reduced phenolics (146.35 ± 16.46 and 72.49 ± 5.14 mg GAE/mL), flavonoids (609.36 ± 77.60 and 312.16 ± 35.13 mg QE/mL) and betalain content (74.19 ± 4.24 and 60.02 ± 2.96 mg/L); leading to the significant reduction in all antioxidant activities. Fermented juices also exhibited greater earthy odours and altered colour profiles, especially in the M. purpureus sample. Additionally, nitrate levels increased significantly in L. casei sample (526.53 ± 12.29 mg/L). Despite limited enzymatic activity attributed to high viscosity and inhibitory compounds of beetroot paste, enzymatic pre-treatments preserved bioactive compounds, while fermentation produced trade-offs between nutritional and sensory quality. Future studies should optimize substrate preparation, refine incubation times to minimize degradation and explore M. purpureus inoculation with mycelium rather than spores to identify possible enhancements in the investigated parameters