Design and application of ozone detoxification equipment for patulin in contaminated apple juice

Abstract: Apple juice can be contaminated by patulin inevitably due to the improper production, processing and storage, which seriously threats the health of consumers. In order to effectively degrade patulin in apple juice, an equipment for detoxifying patulin using ozone technology is designed. The ozone detoxification equipment is made of stainless steel, and it includes 6 systems: ozone preparation system, gas delivery system, ozone concentration adjusting and detecting system, juice delivery system, detoxification system, and ozone decomposition system with heating. Patulin in apple juice is degraded based on the strong oxidation role of ozone by full contacting between juice and ozone. The degradation efficiency of patulin in artificially contaminated apple juice by ozone and its effects on main quality of juice were studied using the designed equipment. The experiments were carried out at 0-12 mg/L ozone concentration and 3 L/min ozone flow rate, and the exposure time of ozone was set from 0 to 30 min with an interval of 5 min based on the preliminary studies. The results showed that patulin in apple juice could be degraded effectively by ozone, and ozone concentration and exposure time could obviously affect the degradation efficiency of patulin (P<0.05). Patulin was significantly reduced with the increase of ozone concentration (P<0.05). When the initial concentration of patulin in apple juice was 247.13 μg/L, patulin was decreased to 87.03 μg/L after detoxification at 7 mg/L ozone concentration for 10 min of ozone exposure, with a reduction of 64.78%. When the ozone concentration increased to 12 mg/L, patulin in apple juice was decreased to 45.30 μg/L, and it was reduced by 81.67% under the other same conditions. The residual patulin in apple juice was well fitted using a power regression curve with a determination coefficient (R2) of 0.954 3. The exposure time of ozone is also a very important factor influencing the degradation of patulin. The residual patulin was significantly reduced with the increase of ozone exposure time (P<0.05). When the patulin initial concentration, pH value and soluble solid content of apple juice were 201.60 μg/L, 3.5 and 15.0%, respectively, patulin was decreased to 49.24 μg/L at the ozone concentration of 12 mg/L and ozone flow rate of 3 L/min for 15 min of exposure, which was reduced by 75.58%. It is lower than the limit level in apple juice (50 μg/L) set by WHO (World Health Organization) and BSDA (British Soft Drinks Association). The relation between the residual patulin and ozone exposure time followed a first-order kinetic model with a determination coefficient (R2) of 0.974 9. Ozone treatment has no significant effects on the soluble solids, pH values, and total acids of apple juice (P<0.05), while adverse effects on its transmittance rate, color, malic acid, and total phenol contents (P<0.05). The phenolic compounds and organic acids are responsible for the flavor and taste of apple juice, so the effects of ozone detoxification on the critical nutritional properties of apple juice should be considered by processors prior to its adoption as a detoxification technique. The results are helpful in the development and commercial application of the ozone detoxification equipment in fruit juice processing.