Adsorption characteristics of patulin in jujube juice using macroporous resin

Abstract: Jujube belonging to the Rhamnaceae and is a nutrient-rich fruit. The production of jujube in China accounts for 90% in the world. During the growth, harvest and storage periods of jujube, it is easily infected by fungus, especially in the rainy days during harvest, so there will be mycotoxins residue in jujube and related deep process product. Patulin is a mycotoxin produced by various species of the genera penicillium, aspergillus, and byssochlamys. It could be detected in jujube or other jujube processing food such as jujube juice once they are infected by penicillum or other fungus. In this study, in order to improve the safety of jujube juice, macroporous resin was used to remove patulin in jujube juice. Macroporous resin is widely used in the processing of fruit juice, it could be used for adsorption of mycotoxin, removal of pesticide residue, decolorization of juice and purification of natural antioxidants. LSA-900B resin has great adsorption capacity for patulin but there were rarely studies focus on patulin removal in jujube juice using macroporous resin. For further understanding the adsorption mechanism of patulin, the adsorption isotherm, thermodynamics and kinetics during adsorption process were investigated, and the physicochemical characteristics including total sugar, reducing sugar, total acidity, flavonoids, total polyphenols, color value and transmittance of jujube juice were analyzed. Results showed that LSA-900B resin exhibited an effective adsorbability of patulin in jujube juice, and the maximum adsorption quantity and removal rate were 5.31 μg/g and 73.78%, respectively. When the temperature was controlled within 30-50 °C, and the initial concentration of patulin was at 30-200 μg/L, the adsorption quantity of patulin decreased with the rise of temperature and increased with the increase of patulin content. The adsorption equilibrium could be described by the Freundlich isotherm (R2>0.99). According to the changes of enthalpy, free energy and entropy, it was suggested that the adsorption process was spontaneous, endothermic process and belonging to physical adsorption. Results of kinetic analysis showed that the pseudo second-order model (R2=0.9982) was more suitable than the pseudo first-order model (R2=0.9529) for describing the kinetic data. The adsorption rate could be affected by film diffusion and intra-particle diffusion, and the former was the rate-limiting step. Moreover, after the adsorption treatment, the contents of total sugar, total acidity, flavonoids and total polyphenols of jujube juice were significantly decreased, while the color value and transmittance of jujube juice were increased. The order of the influence of positive correlation indices was color value > transmittance, and the order of the influence of negative correlation indices was flavonoids > total sugar > total acidity > total polyphenols. After comprehensive analysis of the data, when the initial content of patulin was 100 μg/L, the most suitable condition for this adsorption process could be that the additive amount of LSA-900B resin was 14 g/L and the adsorption time was 90 min. Under this condition, the patulin content of jujube juice decreased to 36.61 μg/L, lower than the standard value of 50 μg/L, and the color value and transmittance of jujube juice could increase to relatively higher values. The results provide an important reference for the further application of LSA-900B in production practice.