Abstract
To explore the functional properties of mixed biopolymer systems affected by acid and salts. The effects of acid and salt solutions (i.e., NaCl, KCl and CaCl2) on the pasting, rheology, texture and microstructure of lotus root starch–konjac glucomannan (LRS/KGM) mixtures were assessed. Acid (citric acid buffer) treatment worsened the pasting (except for breakdown viscosity), rheological (except for fluid index), and textural properties, thereby inhibiting retrogradation, weakening pseudoplasticity and thickening, and reducing mixture viscoelasticity. Furthermore, it led to destructive ruptures and large pores in the internal microstructure. Salt treatment worsened the pasting properties (except for setback viscosity), thus inhibiting retrogradation and weakening pseudoplasticity, but enhanced the rheological properties, improving thickening and fluctuating viscoelasticity of the mixture. Moreover, salt addition decreased the hardness while increasing mixture cohesiveness, and modified the elasticity, adhesiveness and internal microstructure in a salt type- and concentration-dependent manner. A salt solution concentration of 0.5 mol/L NaCl, 0.1 mol/L KCl, and 0.5 mol/L CaCl2 led to the mixture with the best texture and gel network.
Highlights
Lotus root is an important and edible aquatic vegetable widely distributed in China, Japan and Southeast Asia
Trial test results showed that the pasting, rheology and texture properties of the lotus root starch–konjac glucomannan (LRS/Konjac glucomannan (KGM)) mixture were best at a lotus root starch (LRS)/KGM ratio of 8.5:1.5 (M/M) using the following measured methods
The solutions were adjusted to pH 3 and 7 using citric acid-containing phosphate buffer, weighed LRS/KGM was mixed with the solutions in an aluminum box, forming a 6 g/100 g suspension, to determine the effect of pH on the LRS/KGM system
Summary
Lotus root is an important and edible aquatic vegetable widely distributed in China, Japan and Southeast Asia. Lotus roots have crisp tissues and a bright color, are rich in nutrients (e.g., starch, protein, cellulose, polyphenolic substances, and antioxidants), and have considerable medicinal properties [1]. Given their high brittleness, lotus root starch (LRS) particles are crushed or deformed during heating and agitating but do not readily form a gel after cooling [2]. KGM and some similar hydrophilic colloids have been extensively studied in the manufacturing of gel food, beverages, packaging films, and drug carriers, etc. Konjac glucomannan (KGM) is a hydrophilic colloid with high tightness and a branched structure [4,5], with many excellent functional characteristics and properties, including hydrophilicity, thickening, gelation, film formation, and bacterial resistance [6,7], as well as being highly biodegradable.
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