Chicken embryo testThe destruction and detoxification of aflatoxins B,, G,, B, and G2 (50 &mL in 4% dimethyl sulfoxide) with ozone were confirmed by thinlayer chromatography and chicken embryo assay. Aflatoxins B1 and G, were sensitive to ozone and easily degraded with 1.1 mgiL of ozone within 5 min at room temperature. The result of Ames test showed the inactivation of the mutagenic activities of the toxins by ozone. Also, the deleterious acute effect of ozone-treated aflatoxin B, was not detected in the rat. On the other hand, aflatoxins B2 and G2 were rather resistant to ozone, requiring SO-60 min to degrade them completely with 34.3 mg/L of ozone.

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Industrially it is important to understand the cooling process of beer in cylindro-conical tanks (CCTs) in regard to energy efficiency and to the maturation of beer from 10°C to 0°C. However the cooling process is a complicated phenomenon. We have previously studied thermal convection in a miniature CCT constructed of transparent acrylic resin (ACCT) and found that thermal convection was not uniform, but rather wavy in the circumferential direction. In this report thermal convection was studied in a CCT constructed of metal and enlarged to the 500 L size. The water temperature in the CCT was measured by thermosensors and the surfaces visualized using an infrared camera.We confirmed that both 500L CCT and ACCT have qualitatively similar flow from 10°C to below 4°C. Although there are size effects between small CCTs and large CCTs, experiments with the smaller CCT gave useful information on the early cooling process. An infrared camera was employed to investigate the state of convection and gave information on how to effectively refrigerate beer.Key words: Cylindro-conical tank, thermal convection, visualization of flow. -2863(9'8-32In the beer maturation process, cylindro-conical tanks (CCTs) have been widely used as storage tanks since they have several operating advantages including bottom yeast collection, ease of tank cleaning, etc 1 . There are various sizes of CCT used in the brewing world and the sizes can be extremely large, i.e., up to 40 m high and more than 10 m diameter 1 . It is important to understand the details of the cooling process of beer in a CCT in order to optimise the refrigeration and maturation process 2 .In this study water was used instead of beer. The reasons include: (1) the volume expansion coefficient, the thermal diffusivity and the kinematic viscosity of beer are close to those of water 3 , (2) the density of beer has a convex temperature dependability similar to water 3,4 , (3) water is easier to handle than beer.We have previously researched the early cooling process using a miniature CCT made of transparent acrylic resin (ACCT) to visualize the thermal convection in the tank 5 . In this previous work we found that thermal convection was not uniform, but rather wavy in the circumferential direction. Because in practice industrial CCTs are very large, it was necessary to investigate the cooling process using a larger CCT. In this report, the size of CCT was enlarged to 500 L and the CCT was constructed of metal. The early cooling process from 10°C to below 4°C in a 500 L CCT was studied and compared with that in an ACCT. 1%8)6-%07 %2( 1)8,3(7 ']PMRHVS GSRMGEP XEROW ERH GSSPMRKThe 500L CCT was constructed of SUS 304 and had an inner diameter of 55 cm, a height of 253 cm and a cone angle of 60° (Fig. 1a). The cooling zones were divided 1 part cone and 3 parts cylinder. The area of the cooling zones was approximately 45% of the wall, when the tank contained 400 L water as described below. Zones indicated by hatched boxes (Fig. 1a) on the outer wall of the 500L CCT show where the coo...