42-10 |
Effect of blanching conditions and starch swelling properties on textural changes in processed potatoes |
R. L. YOUNG and M. G. Scanlon. Department of Food Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada Understanding the relationships between raw material properties and how those raw materials should be optimally processed is vital for enhanced utilization of potatoes. Our objective was to investigate the effect of starch swelling properties on the textural response of processed potatoes. Potatoes of high and low solids content (starch) were selected from a batch of tubers. Excoriated and whole potato cylinders were prepared and half were subjected to hypertonic mannitol treatment (to remove water from potato cells). Three blanching conditions were selected: standard, low temperature long time (LTLT) and high temperature short time (HTST). After blanching the textural response (modulus) of the cylinders was measured in compression. Hunterlab L (lightness) value of the resulting french fries was also monitored. French fries blanched under standard conditions had large L values, while those blanched under LTLT and HTST conditions had similar L values. Modulus values of excoriated cylinders were substantially lower than would be expected from a simple reduction in the cylinders' cross-sectional area. For fresh potatoes, the moduli for whole potato cylinders blanched by LTLT conditions were smaller than those blanched by HTST and standard conditions, while the moduli for cylinders excised from potatoes with lower starch contents were larger than those of a higher starch content. In contrast, removing water with mannitol prior to processing essentially eliminated textural differences between processing treatments and starch contents. The interaction between free water, starch content and the chosen processing regime and its effect on measured texture illustrates that starch swelling pressure plays a significant role in french fry texture. Blanching conditions should be adjusted for tuber solids content in order to optimize texture as well as to improve fry colour.
Session 42, Food Engineering: Rheology and texture
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