Extraction and characterization of acorn (Quercus ithaburensis) starch: physico-chemical, morphological, thermogravimetric, and technological properties

Abstract

Acorn (Quercus ithaburensis) is the fruit of the Quercus tree, with a rich chemical composition, used as a food for human consumption. Despite being rich in starch, more than half of the production of acorns (Quercus ithaburensis) is not utilised. This study aims to produce and characterise starch from acorn seeds using conventional and ultrasound-assisted methods. For this purpose, the starch production conditions of both methods were obtained from 2FI models using the desirability function approach and optimised using response surface methodology. In the classical method, the optimum extraction time, extraction temperature, and sample/solvent ratio were 3 h, 45 °C, and 1:3. In contrast, in the ultrasound-assisted method, the optimum extraction time, ultrasound frequency, and sample/solvent ratio were 30 min, 45 W and 1:2. The ultrasound-assisted method changed the functional properties of the starch. The amylose contents of starches produced by conventional and ultrasonic methods were 31.12 and 34.26, and the minimum gel formation rates were 18% and 14%, respectively. As a result of thermogravimetric analysis, 98.42% of conventional starch and 87.19% of ultrasonic starch was lost. IR-spectra also showed a similar pattern in both modifications, with the band's intensity at 1076 cm^-1 decreasing in the ultrasonically assisted method. Predicted glycemic index of starches ranged from 78.95 to 79.41. This study characterised acorn starch produced by different methods and demonstrated the demonstrated its potential for use in foods.