Effects of Different Clarification Processes on Qualities in Lemon Juice and Establishment of Prediction Model on Degradation of Limonin during the Storage

To optimize the process of lemon NFC juice, the present study was conducted to compare the effects of the four clarification processes including agar flocculation, combination of enzymolysis and adsorption, combination of enzymolysis and flocculation and freeze-thaw technique on the clarification of lemon juice, and further establish the degradation model of limonin in the lemon raw juice and the lemon clear juice obtained by different clarification processes during storage. The results showed that, the four clarification processes could significantly promote the transmittance and maintain the quality in lemon raw juice. The combination of enzymolysis and adsorption had a more significant effect on clarification efficiency than the other three methods, but it significantly reduced the contents of total phenolics and ascorbic acid in the lemon clear juice. The optimum parameters for the clarification of the lemon raw juice by the combination of enzymolysis and adsorption were obtained by the addition with 0.3% of pectinase, 0.15% of cellulose and 4% of active clay and under the optimum conditions of enzymolysis time 2 h. The degradation rate constants of limonin contents in the samples of lemon clear juice clarified by any of the four processes was attributed to possess a high correlation with Arrhenius model and was modeled as a first-order reaction kinetics equation. The activation energy (Ea) of limonin degradation in the clear lemon juice clarified by combination of enzymolysis and adsorption were lower than the clarified samples by the other three methods, which indicated that limonin was more prone to degradation in this system. Therefore, all of the processes including agar flocculation, combination of enzymolysis and adsorption, combination of enzymolysis and flocculation and freeze-thaw technique could be applied for clarification of lemon NFC raw juice. However, the damage to the functional compositions should be avoid while the use of the clarification in actual juice production.