Biodegradation Behaviour of Thermoplastic Starch: The Roles of Carboxylic Acids on Cassava Starch

The process of biodegradation upon modified thermoplastic starch with various types of carboxylic acids was performed via soil burial testing. As such, modification of thermoplastic starch via esterification with citric acid and ascorbic acid was made varied within the range of 1–4 by weight percentage (% w/w). As a result, after citric acid modification and ascorbic acid modification displayed higher moisture resistivity (15.04 and 20.46%) compared to thermoplastic starch, which resulted in 43.79% respectively. In addition, environmental degradation was determined by performing a biodegradation process by using compost soil. Besides, Fourier transform infrared spectroscopy and high performance liquid chromatography tests were carried out to assess the biodegradability attribute of the starch film. The findings showed that the both citric acid and ascorbic acid modifications exhibited lower rates of weight loss, consequently due to the action demonstrated by of carboxylic acids that inhibited the invasion of microbial after exposure to environmental degradation. Furthermore, the optical analysis revealed that both citric acid and ascorbic acid possessed capability to retard the invasion of microbial upon modifications observed from its rather limited formation of microbial colonies. Nevertheless, the carbonyl index portrayed lower growth rate for citric acid and ascorbic acid, in comparison to unmodified thermoplastic starch. Hence, the study concludes that the addition of carboxylic acid had reduced the rate of degradation for the thermoplastic starch, besides improving moisture resistivity.