76C-31 |
Some changes in pectic substances, starch and firmness during the water immersion of potato slices at low temperatures |
E. Gonzalez-Aguilar1, A. Robledo, J. C. Contreras-Esquivel, M. L. Reyes-Vega, A. F. Aguilera-Carbo, and C. N. AGUILAR6. (1) Food and Nutrition Department, Universidad Autonoma Agraria Antonio Narro, P.O. Box 252, Saltillo, Coahuila, 25000, Mexico, (2) Food Research Department, Universidad Autonoma de Coahuila, P.O. Box 252, Saltillo, Coahuila, 25000, Mexico Thermal processing of fruits and vegetables affects the textural quality of final products, mainly due to the partial destruction of pectic gel that forms much of the matrix of the cell wall and the intracellular adhesive of the middle lamella. Several methods have been proposed to minimize the lack of firmness, among which, low temperature blanching promotes changes at wall cell level forming rigid structures from pectates. Several works have reported such firmness changes in potato using different conditions (i.e. dehydration, freezing, frying, etc.); however, until today it is not clear the exact roles that play some components such pectic substances and starch. The objective was to evaluate the effects of the low temperature blanching treatments on the changes in pectic substances and starch in relation to firmness modifications pre and post frying. Potato slices were blanched in distilled water at 55, 60 and 65 °C, during 10, 20 and 30 minutes. Control samples were potato slices non submerged. Pectinesterase activity, % of polyuronides, esterification degree, galacturonic acid content, pH, starch content, reducing and total sugars and the firmness(Instron machine) were determined. Firmness preservation was evaluated post frying. Maximum firmness was achieved when potato chips were immersed at 60°C during 20 minutes (2.18 N). Under these conditions, pectinesterase activity value was of 1.4 U/mL and the esterification degree, % of polyuronides and pH values were 11.1%, 1.23% and 5.88, respectively. Starch content was lower at 55 and 60°C than 65°C, similar results were obtained for total and reducing sugars. After frying, the firmness preservation was higher in pretreated samples at 60°C during 10 minutes. Results of pectic substances were related to increments in firmness of potato chips, whilst, results obtained for starch, total and reducing sugars contents were not clearly related to firmness.
Session 76C, Fruit & Vegetable Product: Fresh Fruits and Vegetables
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