Abstract:
This thesis entitled “Thermal and non- thermal extraction and pasteurization of red
dragon fruit juice” investigates the application of novel non-thermal and thermal processing
technologies—pulsed electric field (PEF), ultrasound (US), and retort pasteurization—for
enhancing juice extraction, preservation, and storage stability in red dragon fruit (Hylocereus
polyrhizus). Due to the fruit's high perishability and complex pulp structure, traditional
extraction methods often compromise juice yield and quality. The study aimed to (1) optimize
US and PEF pretreatment parameters to maximize juice extraction, (2) evaluate PEF and retort
pasteurization for quality preservation and enzyme inactivation, and (3) assess the shelf life of
treated juices during refrigerated storage. Experimental results revealed that US pretreatment
(40 % amplitude and 10 min treatment time) significantly enhanced juice yield (72.83%) and
retention of bioactive compounds - betacyanins (10.08%), total phenolics (19.13%), and
antioxidant activity (12.33%) - outperforming PEF pretreatment. PEF pasteurization (40
kV/cm, 21 μs, 600 pulses) effectively inactivated polyphenol oxidase (14.6%) and peroxidase
(7.2%) while preserving nutritional quality. Retort pasteurization (90°C, 5 min) provided
superior microbial stability, retaining over 90% of phenolics and antioxidant activity post-
processing. Storage studies over two months confirmed better retention of betacyanins and
antioxidant activity in PEF-treated juice, though retort pasteurization better controlled
microbial growth. FTIR analysis and sensory evaluation supported the preservation of
molecular and sensory quality in both treatments. Economic analysis indicated that both PEF
and retort pasteurization are commercially viable, as they exhibit equal benefit-cost ratios. The
findings establish ultrasound-assisted extraction and PEF pasteurization as promising
technologies for producing high-quality, functional dragon fruit juice, while retort processing
offers cost-effective shelf life extension. This research provides a foundation for scaling
innovative processing methods in the functional beverage industry.
