Use of eggshell powder as a potential hydrolytic retardant for citric acid-filled thermoplastic starch

A simple preparation of low water-soluble crosslinking starch-based foam containing palm oil: Thermo-physicochemical properties

“…All TPS foams presented characteristic bands of palm oil at 2,924 cm −1 and 2,854 cm −1 due to –CH stretching and 1,743 cm −1 assigned to C=O stretching of the carboxylic group. 32 The appearance of a new C=O stretching peak indicated the occurrence of crosslinking reaction due to esterification between citric acid and glycerol/starch, which was observed at different bands as 1,724 cm −1 23 , 1,730 cm −1 9 , and 1,740 cm −1 . 33 The C=O stretching peaks of palm oil and esterified crosslinking chains were very close to each other; therefore, the esterified peak alone could not be used to indicate the occurrence of crosslinking starch chains.…”

“…On the other hand, in the citric acid-filled TPS foams, the thickness of each wall inside the starch foam matrix increased with increasing citric acid concentration (Figures 7(b)–(f)). The included citric acid acted as a hydrolytic agent 9 or a crosslinking agent 23 for the starch matrix. Hirashima et al 25 explained that the two different roles of citric acid responded conversely to the viscosity of the starch pastes as (i) a crosslinking agent; when the pH of the citric acid solution was in the range of 3.6–5.5, the viscosity of the starch pastes increased, and (ii) a hydrolytic agent; when pH of the citric acid solution was below 3.5, the viscosity of the starch pastes decreased.…”

“…7 TPS foam dissolved at 16% in water at 30°C for only 30 min; 1 however, it requires additional improvements to be suitable for packaging applications such as compostable trays and plates. 8 Many previous starch modification techniques have been used to overcome low water resistance limitations including (i) addition of fillers such as eggshell, 9 natural fibers, 6,10 and organoclay, 11 (ii) mixing with organic compounds including vegetable oil, 8,12,13 essential oil, 14 and citric acid, 15,16 and (iii) blending with polymers such as chitosan, 17,18 poly(lactic acid), 19,20 and agar. 21 Among the given examples in these various techniques, vegetable oil and citric acid are low-cost food additives and are safe for food packaging applications that can effectively improve the low water resistance limitations of TPS.…”

“…On the other hand, in the citric acid-filled TPS foams, the thickness of each wall inside the starch foam matrix increased with increasing citric acid concentration (Figures7(b)-(f)). The included citric acid acted as a hydrolytic agent9 or a crosslinking agent23 for the starch matrix. Hirashima et al25 explained that the two…”

Foamed bioplastics: a review

“…This market is starting to require manufacturers to produce environmentally safe materials that must obviously also meet certain usability requirements. The growing interest in environmentally friendly materials has stimulated the development of the production of new packaging materials consisting of natural raw materials (Parra et al, 2006;Prapruddivongs and Wongpreedee, 2020;Steinbüchel, 2005).…”