Abstract
This study aimed to identify the feasibility of producing highly-substituted starch esters via thermal modification of starch using a post-culture medium of Yarrowia lipolitica yeast. This manuscript describes a successful attempt at potato starch modification with a post-culture medium of Yarrowia lipolitica yeast with different concentrations of organic acids. Starch preparations produced by roasting (130 °C) and these produced by starch reaction with a synthetic acid mixture were compared in terms of the types and number of acid residues esterified with starch. The effectiveness of starch esterification was found to depend on medium composition and to be higher upon the use of a synthetic acid mixture. In addition, a higher reactivity with starch was demonstrated for citric acid than for α-ketoglutaric acid. The highly-substituted starch esters formed as a result of potato starch modification with post-culture medium were characterized by decreased values of thermal parameters of pasting characteristics, determined with a differential scanning calorimeter (DSC), and by compromised resistance to amylolysis. The intensity of these changes increased along with an increasing total percentage of starch ester substitution.
Highlights
Starch—which plays the role of a storage substance in plants—is produced on the industrial scale mainly from maize, rice, tapioca, and potatoes
In the case of citric acid (Figure 1), the highest achieved substitution percentage was 4.9%. Comparable content of this acid was reported by Mei et al [18], who used citric acid to esterify cassava starch; by Kapelko-Żeberska et al [6], who by using the same method of esterification obtained preparations with 2.5 to 5.5 g of citric acid residues per 100 g of the preparation; and by Olsson et al [19], who investigated the possibility of using starch citrates in biodegradable package materials
An analysis of reaction effectiveness allows for the conclusion that it is advisable to use higher amounts of citric acid in starch esterification reactions because this enables the production of preparations with a higher degree of esterification and ensures that proportionally more acid takes part in the reaction with starch than in the case of a reagent containing less acid being used (Figure 2)
Summary
Starch—which plays the role of a storage substance in plants—is produced on the industrial scale mainly from maize, rice, tapioca, and potatoes. Most of starch material is modified with enzymatic, physical, or chemical methods to tailor its properties to specific industrial applications [2]. Physically- or enzymatically-modified starch may be used in the food industry without any limits. Chemically-modified starch preparations are produced from starch isolated from starchy materials using acids, their anhydrides, or salts, as well as oxidative or alkylating agents. Such modified preparations of low-substituted starch serve as food additives, and their use is regulated by law [3]. Among a wide array of chemically-modified starch preparations, oxidized starch (E1404), monostarch phosphate (E1410), distarch phosphate (E1412), phosphorylated distarch phosphate (E1413), acetylated distarch phosphate (E1414), acetylated starch (E1420), acetylated distarch adipate (E1422), hydroxypropyl starch (E1440), hydroxypropyl distarch phosphate (E1442), sodium starch octenylsuccinate (E1450), acetylated oxidized starch (E1451), and aluminum starch octenylsuccinate (E1452) are permitted for use as food additives [4]
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