Abstract
The aim of the present study was to extract starch from acorn (Quercus suber L.) fruits using water and alkaline methods. Structural and functional properties of extracted starches were investigated and compared to those of corn and modified starches in order to determine their innovative potential application in food industry. The yield of extraction using the two methods was about 48.32% and 48.1%. The isolated starches showed low moisture, fat and protein contents, revealing high purity and quality. Additionally, the starch extracted using the alkaline method (AAS) showed higher lightness (60.41) when compared to starch isolated using hot water (WAS). However, the lightest white color was found for studied commercial starches. Moreover, AAS starch exhibited the highest swelling power, solubility and water absorption, followed by WAS and commercial starches. Results showed that extracted acorn starches were characterized by greater enthalpy and gelatinization temperatures. Similar observations were noted using FT-IR spectra analysis for all analyzed starches. In addition, granule starches observed using scanning electron microscopy were found to be spherical and ovoid. However, from the analysis by X-ray diffraction, a crystalline pattern of C-type was found for acorn starches, while commercial starches presented an A-type pattern. As an innovative food application, these underexploited acorn starches were valued and served to produce new custards with improved functional properties and better microstructure when compared to commercial custard.
Highlights
The genus Quercus, which belongs to the Fagaceae family, contains around 600 species worldwide [1] such as Quercus suber, Quercus robur, Quercus petraea, Quercus ilex, and Quercus pubescens [2]
Most native starches are limited in their direct application because they are unstable with respect to changes in temperature, pH, and shear forces
In order to replace the chemically modified starches, in the food industry, researchers and nutritionists are searching for new natural starch sources such as acorn fruits [6,7,8,9,10,11,12,13]
Summary
The genus Quercus, which belongs to the Fagaceae family, contains around 600 species worldwide [1] such as Quercus suber, Quercus robur, Quercus petraea, Quercus ilex, and Quercus pubescens [2]. To enhance the consumption of natural resources, many other new sources of starch are being studied, such as biri, ginger, arrowroot, sweet potato and yam [11], and maca or Peruvian carrot [12]. These native starches of different botanical origins reveal enormous diversity in their structure and composition, including their amylase, amylopectin, and minor constituent (lipid, protein, and mineral) contents. Starch is used to improve the properties of baking flour and bakery products such as cakes and breads due to their high consumption During their formulations, starch is one of the components responsible for broad technological functionality. The study aimed to investigate selected properties of a newly formulated acorn-based custard to provide information on the potential incorporation of acorn starch into various industrial food applications
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