COMBINED EFFECTS OF BLANCHING AND FREEZING ON THE CELLULAR STRUCTURE, TEXTURE AND COLOR OF GREEN BEANS
This work studies the combined effects of blanching, using either peroxydase (POD) or lipoxygenase (LOX) as indicators, and different freezing conditions on the final quality of green beans. The time-temperature blanching conditions for the freezing experiments were chosen arbitrarily to reach an indicator residual activity of 10％. The blanching temperatures used were 70, 80, 90 and 100℃. After blanching, the samples were submitted to four freezing conditions: a) nitrogen vapor, b) blast freezing, c) natural convection, and d) natural convection inside polystyrene boxes. The freezing rate was measured by means of thermocouples placed in the center of the green beans pods and by fluxmeters adhered to their surfaces. The quality of thawed samples was evaluated by: a) light microscopy of thin cut transversal sections of the pods, b) axial compression tests by application of constant constraint of 2 N and, c) evaluation of color variation using the CIELAB color space. HTST blanching protocols contributed to minimize color and texture deterioration. High freezing rates ＞ -94.2 kJ/(kg.min) enabled preservation of the internal parenchyma and, consequently the retention of firmness. Color is not significantly affected by the freezing rate.
ALVARO AMARANTE CAMILA PERUSSELLO JEAN-LOUIS LANOISELL(E)
Pontifícia Universidade Católica do Paraná, Mechanical Engineering Department P.O. Box 17315, 80242- Université de Technologie de Compiègne, Laboratoire Génie de Procédés Industriels, P.O. Box 20,529;
国际会议
The 22nd International Congress of Refrigeration(第22届国际制冷大会)
北京
英文
2007-08-21（万方平台首次上网日期，不代表论文的发表时间）