Quality Characteristics of the White Birch Sap with Varying Collection Periods

摘要

This study evaluated the quality characteristics of white birch (Betula platyphylla var. japonica) sap with different collection times. The changes of browning index, turbidity, pH, total acidity, organic acid, free sugar, crude protein, crude ash, and mineral content were investigated. The browning index and turbidity increased from 0.076 to 0.222 and from 0.048 to 0.138, respectively, with increasing collection time. The pH decreased from 6.09 to 4.72, while total acidity increased with increasingcollection time. Citric and malic acids were detected and malic acid increased with increasing collection time. Glucose and fructose as free sugars were detected and their contents were 0.364—0.433% and 0.497 — 0.664%, respectively. Crude protein and crude ash contents remarkably increased from 3.40 to 32.37 mg% and from 0.01% to 0.04%, respectively, with increasing collection time. Cu, Fe, Ca, Mg, Mn, and K were detected, and increased with increasing collection time. Particularly, K increased remarkably from 5.25 to 37.27 mg/L over time. These results indicate that the optimum processing method to improve the quality of white birch sap is necessary, because the quality of sap decreased as collection time increased, but nutritional value increased.