EFFECT OF THE METHOD OF ISOLATION AND THE DEGREE OF RIPENESS ON THE PHYSICOCHEMICAL, STRUCTURAL AND RHEOLOGICAL PROPERTIES OF APPLE STARCH

We evaluated the effect of two isolation methods (SN method= water washes, and the ST method= toluene Washes) in terms of yield and physicochemical, morphological, thermal, structural and rheological properties of starches of Smoothee Golden Delicious apples harvested at 60 and 90 days after flowering (DAF). The size of the granules were not influenced by the isolation method, but by fruit maturity, going from 2.7-8.6 to 4.5-9 mu m at 60 and 90 DAF, respectively. The SN method showed better yields than the ST method, but the purity of the starches was similar in both cases (> 92%). The color of the starches was influenced both by the isolation method and fruit maturity. The rheological properties varied with fruit maturity; the consistency index (K) ranged from 5.49 to 15.19 Pa sn for apples harvested at 60 and 90 DAF, indicating possible structural changes in the granules. All starches exhibited a type-C diffraction pattern and low gelatinization enthalpies between 6.90 and 10.20 J/g. Immature apples can be an alternative source of starch with specific physicochemical and structural properties.