Pulsed Light and Retort Processing of Coconut Inflorescence Sap (neera): Process Optimization and Storage Stability

Abstract

The coconut inflorescence sap, also known as coconut neera, is a low glycemic index beverage, susceptible to rapid fermentation from the time of its extraction. Coconut neera was subjected to pulsed light (PL) processing at different treatment conditions, viz., number of pulses (50, 100, 150), sample-source distance (4, 7, 10 cm), and sample depth (5, 10, 15 mm). The retort processing (RP) of coconut neera was conducted at different combinations of temperature–time (70–90 °C; 15–25 min). The PL processed coconut neera exhibited less impact on the physicochemical and bioactive compounds, while significant ascorbic acid losses (up to 28%) were observed at intense treatment conditions. On the other hand, the RP samples showed significant colour degradation (E^* > 3.0) and loss of ascorbic acid (up to 64%). The PL processing effectively reduced the microbial load (total bacterial count, yeast, and mould count) by up to 6 log cycles as against 8 log cycle reduction in case of RP samples. The optimized process condition for PL processing was 150 pulses/5 mm sample thickness/7 cm sample-source distance, while the corresponding condition for RP was found to be 82 °C/19 min. The optimally processed RP (retort pouch) samples had a shelf life of 25 days, while that of PL (PET bottles) treated samples was limited to 20 days, under refrigerated storage conditions. The outcomes from this study demonstrate the efficacy of PL in attaining microbially stable, superior-quality coconut neera with the potential for enhanced shelf life.