Physicochemical properties changes of sea buckthorn cloudy juice during cold crushing, concentrating and storage

Sea buckthorn berries were used as raw materials to study the process of concentrating sea buckthorn cloudy juice and their quality. Physicochemical properties including vitamin C, total flavonoids, total polyphenols, polysaccharides, pH value, total acidity, and browning index changed. Cold crushing sea buckthorn berries, concentrating production and the storage of concentrated cloudy juices were investigated systematically. The results showed that the quality of sea buckthorn juice obtained by cold crushing process technology was excellent. The contents of soluble solids and total acidity reached to 18.0% and 4.24% of sea buckthorn juice obtained respectively. It contained vitamin C 729.69 mg/100mL, flavonoids 445.17 mg/100mL, total polyphenols 924.67 mg/100mL and polysaccharides 25.22 mg/100mL. Disc milk separator removed the impurities and oil in sea buckthorn juice due to horizontal screw centrifuge. Whole cold crushing was fast with low temperature. Nutrient and health components in sea buckthorn juice lost less, they had been effectively enriched. Then, different concentrations for multiple sea buckthorn juices were processed at 45℃ by evaporation in the vacuum of 0.095~0.1 MPa. With the increase of the concentration, the loss rate of nutrients and browning index became larger, the total acidity and 5-HMF content were increased and pH value was decreased. Different concentratedn juices were placed at room temperature(10 to 25℃) and refrigerated conditions(5 to 8℃) for 60 days, their physicochemical properties were changed as follows. Vitamin C, flavonoids, total polyphenols and polysaccharide contents decreased gradually, pH and total acidity did not change significantly, browning index and 5-HMF content increased. Furthermore, refrigerated conditions were conducive to the preservation of the sea buckthorn juice compared with the room temperature condition. The nutrient and health components in preserving rate of same multiple sea buckthorn cloudy juices placed at refrigerated conditions were higher than that placed at natural room temperature. The nutrient and health components in preserving rate of 2-fold concentrated cloudy juice at refrigerated conditions was highest. Its vitamin C, total flavonoids, total polyphenols, polysaccharides preservation rate were 11.46%, 20.44%, 18.37%, 9.83% higher than that of 2-fold concentrated cloudy juice placed at room temperature. Moreover, the browning index and 5-HMF content of concentrated sea buckthorn cloudy juice placed at refrigeration conditions was lower. 2-fold sea buckthorn cloudy juice stored at room temperature conditions was not stabile, but the stability of 2-fold concentrated cloudy juice at refrigerated conditions was better than that of 3 times and 4 times concentrated cloudy juice.