Effects of Thermal, Acidic, and Enzymatic Extraction Methods on the Physicochemical, Microbiological, and Sensory Properties of Longkong Syrup

Abstract

Longkong (Lansium domesticum Corr) is an important economic fruit in Southern Thailand. The prices of fresh longkongs in the harvesting season were significantly low due to large domestic production. This work attempted to give added value to low-grade longkong by producing syrup. The pectinase-treated longkong juice showed a higher recovery of soluble solids (p£0.05), compared to the other extraction methods (blending, hot water (90°C, 15 min), and hot acid (0.1N HCl at 90°C, 15 min)). Extracting a dilute sample (1 : 1 pulp to water ratio) improved the recovery of soluble solids (p£0.05). Longkong syrup was obtained by adding sucrose to longkong juices at a final concentration of 70% w/w. The color values (L*, a*, and b*) for non-enzymatic treated syrup were higher than that of the pectinase-treated syrup (p£0.05). Regarding clarity, the longkong syrup prepared with pectinase-treated juice showed significantly lower turbidity (p£0.05). Sensory evaluation showed that the pectinase-treated syrup had a higher mean score on all attributes (p£0.05) than the control sample (w/o pectinase). Levels of aerobic plate count, yeast and mold count, Staphylococcus aureus, and Salmonella spp. of the longkong syrups complied with Thai Community Product Standard (TCPS) 1500/2561 for plant-based syrup.