Effect of Preservation Methods on Retention of Main Quality Compnents in Fresh Tea Leaves

Fresh leaves plucked from tea bushes of 11 varieties were preserved by freezing, hot-air drying or microwave heating to compare the retention of polyphenols, free amino acids and caffeine in the leaves. The two-dimensional point set distribution and principal component analyses were performed to determine the data variances among the samples. The results showed that the contents of polyphenols, EGCG, EC, ECG, aspartate, arginine, serine and cystine were significantly lower in the tea leaves treated by hot-air than by freezing. Either microwaved or frozen leaves could largely retain the original composition. However, being convenient and efficient in handling and for preservation, the microwave method was recommended for the application.