Pilot-scale Production of Cloudy Juice from Low-quality Pear Fruit under Low-oxygen Conditions

In this study, a process for the production of premium quality yellowish, cloudy pear juice from low-quality fruit under low-oxygen conditions was developed. The production process consisted of (1) shredding, (2) pressing with spiral-filter technology including a vacuumized extraction cell, (3) holding in an inert gas buffer tank, (4) pasteurization, (5) and refrigerated storage. First, the system parameters of a spiral-filter press were optimized with the aim of producing a yellowish, cloudy pear juice with the highest possible juice yield. A maximum juice yield of 78% could be obtained. Enzymatic browning during juice extraction could be suppressed as a result of the fast processing and the low air (oxygen) levels in the extraction chamber of the spiral-filter press. Furthermore, we observed that instantaneous pasteurization at 107°C for 6 s, subsequent aluminium laminate packaging and cold storage had only a minimum effect on the phenolic composition.