Study On Cloudy Blueberry Juice Processing And Its Pomace Drying

Blueberry is one of the fruits riched with nutrient contents, as known"the king of the fruits". Some blueberries are eaten in fresh, some are processed to products, such as juice﹑beverage﹑jam and so on. In order to improve the qualities of cloudy juices and resolve the critical technologies restricted the quick development of juice market, the systemic study on the processing and qualities of cloudy juices is very essential.The objective of this dissertation was to study the effect of steam blanching on the polyphenol oxidase (PPO), and the optimum parameters of steam blanching process were confirmed with blanching for 2 min. Compared with the effect of PPO inhibitor Vc on juice quality, steam blanching was not only able to inactivate PPO, but also good for the recovery of anthocyanins and polyphenolics, improving cloudy juice quality.The effects of different pectic enzymes on cloudy blueberry juice were determined. The commercial pectinase named RAPIDASE C80 MAX (RC), which had cellulytic activity and pectolytic activity, had a desirable effect on the yield and quality of blueberry juices. 0.0041 g/dL RC addition could increase the juice yield by more than 10% and improve the cloud and color stability by enzymatic reaction for 80 min at 50℃.The influences of different hydrocolloids on the stability of cloudy blueberry juices were studied, and the mechanism of cloud stability was investigated. Compared with single gum aciduric CMC, the co-operatation of 0.04% (w/v) xanthan and 0.08% (w/v) aciduric CMC had better effect on juice stability. The mixture of aciduric CMC and xanthan accelerated a weak three-dimension network formation, and improved the stability of small suspended particles. Furthermore, the juice added with multiple hydrocolloids had best color and cloud stability with the highest z-potential, its cloud stability involved in electrostatic repulsive forces. The results of storage tests at different storage temperature indicated that anthocyanins were prone to degradation, and the non-enzymatic browning of cloudy blueberry juice was prominent. Storage at low temperature was good for the color stability of juices.According to the results of the main components of sedimentation of cloudy blueberry juices after 6 months storage, the main aspects influencing sedimentation of blueberry juices were discussed. During the storage, the macromolecular substances such as protein and pectin, cell fragments and other suspended particles formed the sedimentation due to the action of gravity. During storage part particles were aggregated together and grown up to form more sediments.Cloudy blueberry juice concentrates and their rheological properties were studied. The 47oBrix blueberry juice concentrates, the 55oBrix blueberry juice concentrates without gums or with single gum appeared a pseudoplasticity, fit for power-law model; the over 55oBrix blueberry juice concentrates with aciduric carboxymethyl cellulose (CMC) and xanthan, 61oBrix blueberry juice concentrates without gums or with single gum exhibited a thixotropic...