Wasabi, Japanese horseradish (Wasabia japonica (Miq) Matsum) is grown to prepare a green paste which is eaten with traditional Japanese dishes. The plant is grown as a perennial crop in Japan and is now also grown in New Zealand. The best quality wasabi products are produced from the rhizomes (stems) although other parts of the plant such as petioles and leaves also possess some pungency and are also used as raw materials. The characteristic flavour of wasabi comes from the volatile isothiocyanates (ITCs), which are evolved from glucosinolates by enzymatic hydrolysis when tissues are macerated. In this study the total isothiocyanate (ITC) and six different ITCs were measured in the rhizome of wasabi grown at Lincoln under four different soil treatments. The level of total ITC ranged from 2425 to 2810 mg/kg fresh weight, which was significantly higher than the values reported in the literature for wasabi grown in Japan (mean 1659 mg/ kg). Allyl isothiocyanate (AITC) was the main ITC and it contributed between 86 to 92% of the total ITC measured in the rhizomes. Overall, there were small changes in the individual ITCs as a result of the different treatments (control, lime, manure, lime and manure), however no correlation between ITC concentration and yield of plants was found. The total ITC contents quantified by GCMS were marginally higher than the total ITC’s measured by UV spectrometry after approximately one year storage of paraffin oil extract at 0 to -4oC. Comparison of isothiocyanate yield of wasabi rhizome tissues grown either in soil or water Tamanna Sultana, G P Savage, D L McNeil and N G Porter Food group, Animal and Food Sciences Division, Lincoln University, Canterbury, New Zealand. New Zealand Institute for Crop & Food Science, Christchurch, New Zealand. Abstract The isothiocyanate (ITC) content of wasabi, the Japanese horseradish (Wasabi japonica) was measured, by release from glucosinolates, in the rhizomes of plants grown in two traditional ways. Mature plants approximately 18 months old were harvested from two different commercial farms located in the south island of New Zealand. At one farm the plants were grown in raised soil beds while the plants in the other farm were grown in gravel irrigated by river water. Following harvest theThe isothiocyanate (ITC) content of wasabi, the Japanese horseradish (Wasabi japonica) was measured, by release from glucosinolates, in the rhizomes of plants grown in two traditional ways. Mature plants approximately 18 months old were harvested from two different commercial farms located in the south island of New Zealand. At one farm the plants were grown in raised soil beds while the plants in the other farm were grown in gravel irrigated by river water. Following harvest the rhizomes from each growth medium were divided into five size groups based on the weight and length of the rhizomes. The different sized rhizomes were also subdivided into top, middle and bottom portions of the rhizomes and each portion was further subdivided into skin and cortex, and vascular and pith using a knife. The individual and total isothiocyanate content of each portion of the rhizomes were extracted using dichloromethane and measured using a GCFPD technique. The total isothiocyanate content of the rhizomes grown in soil increased (14.24 times) linearly from 15 to 100 g rhizome weight while the mean isothiocyanate content of the water grown wasabi increased (11.13 times) non-linearly for similar sized rhizomes. Water grown rhizomes in the weight range 20 to 60 g gave significantly (P=0.030) higher total ITC (2.2-2.9 times) than similar sized soil grown wasabi. Analysis of the tissues showed that the total and the individual isothiocyanates were found in significantly higher levels (73% and 64% respectively) in the skin and cortex compared to the vascular and pith tissues. Analysis of the isothiocyanate content of the different locations of the wasabi rhizome showed that the lower portion of the rhizome contained significantly higher levels of both total and individual ITCs compared to the middle and top portions of the rhizome. Investigation of isothiocyanate yield of flowering and non-flowering tissues of wasabi grown in a flooded system Tamanna Sultana, David L McNeil, Noel G Porter, G P Savage Food Group, Animal and Food Sciences Division, P O Box 84, Lincoln University, Canterbury, New Zealand. 2 Victorian Institute of Dryland Agriculture, Melbourne University, Horsham, Victoria, Australia. New Zealand Institute for Crop & Food Research Ltd, Christchurch, New Zealand.