IMPROVED VACUUM FRYING PROCESS for HIGH QUALITY SWEET POTATO CHIPS a Thesis by YAGMUR RAVLI Submitted to the Office of Graduate
IMPROVED VACUUM FRYING PROCESS FOR HIGH QUALITY SWEET POTATO CHIPS A Thesis By YAGMUR RAVLI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Rosana Moreira Committee Members, Elena Castell-Perez Steven Talcott Head of Department, Stephen Searcy December 2012 Major Subject: Biological and Agricultural Engineering Copyright 2012 Yagmur Ravli ABSTRACT Vacuum frying is a promising method for preserving the desired color, texture, and flavor of products with high sugar content. Since most vegetables and fruits degrade when processed with traditional frying, vacuum frying is an excellent alternative to high temperature processing. However, in vacuum frying the product should be pre-treated before frying to obtain a better texture. The kinetics of oil absorption and oil distribution in sweet potato chips (total, internal, and surface oil content) was studied so that effectiveness of the de-oiling system could be established. An analysis of product quality attributes (PQA) such as moisture content, oil content, microstructure, diameter shrinkage, and thickness expansion, as well as, color, texture, bulk density, true density, and porosity of chips fried at different temperatures (120, 130, and 140°C) was performed to evaluate the effect of process temperature on the product. The final oil content of the sweet potato chips was 0.178±0.007, 0.178±0.011, and 0.172±0.002 g/g solid for frying temperatures of 120, 130, and 140ºC, respectively. These values were lower (~60% less) than those found in traditionally fried sweet potato chip, which indicates that the de-oiling mechanism is crucial in vacuum frying processing.
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