Abstract

The aim of this study was to determine the optimal cooking conditions in preparing jujube concentrates using various boiling times (5, 10, 15, 20 hours). The moisture contents of the concentrate samples ranged from 38.86 to 42.36%. Crude protein content was highest in the 15 hr-boiled concentrate, crude fat was highest in the 20 hr-boiled concentrate and both the 15 and 20 hr boiled concentrates had high crude fiber contents. There were no differences in color L- and a-values by boiling time; however, the b-value decreased with increasing boiling time. The pH levels of the concentrates ranged from 5.24 to 5.27, and the brix level increased with increasing boiling time. Glucose was the primary of free sugar in the concentrates and its highest level was 102.3 ${\mu}M$ in the 20 hr-boiled concentrate. The 15 hr-boiled concentrate had the highest electron donating ability to 46.68%. The total polyphenol contents of the concentrates ranged from 21.53 to 24.56%, in which the 15-boiled concentrate had the highest level (24.56%). In the sensory evaluation, the 15-hr-boiled concentrate again performed well, showing the highest overall acceptability scores. From these results, 15 hrs was the optimal boiling time for preparing jujube concentrate in terms of obtaining functional compounds and overall product acceptability.

Keywords

• Jujube concentrates;
• electron donating ability;
• total polyphenol contents;
• overall acceptability