Organic Acids of the Microbiological Post-Culture Medium as Substrates to be Used for Starch Modification

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.

Effect of the Esterification of Starch with a Mixture of Carboxylic Acids from Yarrowia lipolitica Fermentation Broth on Its Selected Properties

“…Starch was modified according to the method for starch citrate production described by Kapelko-Żeberska et al [ 5 ] and Zdybel et al [ 23 ], in two parallel series.…”

“…The degree of starch substitution (DS) was expressed as percentage content (g/100 g) of acid residues in the modified starch preparation and determined according to the method described by Zdybel et al [ 23 ].…”

“…The temperatures of onset, maximum, and end of the phase transformation, and the specific heat of phase transformation were read from the thermal curve obtained. The analysis was carried out in triplicate [ 23 , 25 ].…”

“…The determined amount of glucose was used to calculate the percentage of rapidly digestible starch (RDS), slowly digestible starch (SDS), and amylolysis-resistant starch (RS) in the starch preparations. The analysis was carried out in triplicate [ 5 , 23 ].…”

“…The possibility of starch modification with a mixture of organic acids contained in a fermentation broth was described in our previous paper [ 23 ]. However, it is still an innovative research issue also due to a novel direction of managing fermentation broth waste.…”