Physical quality change of rose tea during freeze drying

Abstract

Rose tea began to be widely developed since it has advantages in the form of high antioxidant content, and fragrant aroma. Currently, rose tea production uses manual dryers in the form of sunlight energy, which might reduce the physical and chemical quality of rose tea. The low temperature drying is expected to be able to maintain the quality of rose tea. The aim of the study was to determine the drying characteristics of rose tea using a freeze dryer machine. The material used is a local type of rose petals from the Malang region with a water content of 86.76%. The tool used is 1 unit freeze dryer capacity of 1.5 kg with freezing temperature of -18oC, and with a pressure of -76 cm Hg. The drying chamber is made of stainless steel equipped with three heater plates with a total power of 500 watts. The experimental design uses variations in drying time, namely 0, 12, 18, 24, 30, and 36 hours. Parameters measured were water content, color, weight loss, and antioxidant content in the form of flavonoids. The experimental results showed that the final moisture content of roses using drying freeze dryer was 9.54% with a drying rate of freeze dryer of 2.14% per hour. Rose color has decreased from L * value of 27.37 to 8.87 a * value of 52.81 to 14.84 and b * value of 26.19 to -0.77. Based on this, compared to drying with sunlight and cabinet dryers, drying with a freeze dryer is better at drying roses into rose tea.