Color Stability of Juice Concentrates of 6 Pear Species during Storage at 4

The color stability of the juice concentrates that were prepared from 6 pear species was studied during the storage at 4 ℃.During the storage of the 6 pear concentrates,the browning degree and the total color aberration elevated gradually,the content of reducing sugar changed slightly,the content of amino nitrogen showed a decreasing trend,the soluble phenol and protein reduced gradually,and no obvious change in pH was found.The difference of color and its related indexes among 6 pear juice concentrates were obvious-the pear concentrates prepared from Dangshansu pear,Kuerle fragrant pear and Laiyangchi pear showed a higher browning degree compared to Zhongxiang pear,Huangjin pear,and Qiu pear.The concentrate prepared from Kuerle fragrant pear displayed higher soluble phenol content,and that prepared from Zhongxiang pear had higher protein content.The concentrate of Dangshansu pear exhibited the highest pH(above 4.9) and that of Laiyang pear showed the lowest pH(4.4-4.5) during the storage.The peaks of 5-HMF content of concentrates prepared from Dangshansu pear and Laiyangchi pear appeared at the fourth month and those of other species appeared at the third month.