Effect of planting time on the pungency concentration of white radish (Raphanus sativus L.) grown on the central coast of New South Wales, Australia

White radish (Raphanus sativus) is an extremely popular root vegetable in Japan, Korea and other Asian countries. It is consumed in a wide variety of forms including fresh, dried and pickled. The performance of this vegetable as a crop in Australian climate and soil is of particular interest as it represents a significant export market opportunity for Australia. The predominant taste characteristic of white radish is its fresh pungent flavour which is caused by 4-methylthio-3-trans-butenyl Isothiocyanate (MTBITC). This paper investigates the effects of different planting times on MTBITC concentration in the roots of Hoshiriso white radish. Additionally, it was determined whether there is any change in MTBITC concentration due to root maturity and distribution through out the root. Four different planting times corresponding to growth in the Spring, Summer, late Summer and Autumn were used with roots harvested at the same five points throughout the crop development period between 47 days and 110 days after sowing. MTBITC was extracted and measured by gas-liquid chromatography with the method developed by Okano et al. (1991). It was found that the MTBITC concentration differed significantly between the four trials with root maturity. The average MTBITC concentration was highest in the distal end of the root decreasing along the root to the lowest concentration in the top section of the root. MTBITC concentration was the highest in the Spring trial and the lowest in the Autumn trial.