Polysaccharides are widely used to improve the quality of plant-based meat analogue (PMA). In this study, four kinds of konjac glucomannan (KG) with different deacetylation degrees (DD) were prepared, namely KG1 (native KG, DD = 0.00 %), KG2 (DD = 41.40 %), KG3 (DD = 80.01 %) and KG4 (DD = 89.07 %), and their effects on the quality of PMA were studied. Results manifested that KG3 improved the hardness (from 3017.16 g to 3307.16 g) and protein digestibility (from 49.65 % to 53.01 %) of PMA without reducing the P21, KG2 and KG4 were less effective than KG3, while KG1 led to a significant decline in the hardness and protein digestibility of PMA. The rheological properties and intermolecular force analysis showed that the partially deacetylated KG was more conducive to improving the G\' of the protein system during heating and the proportion of covalent bonds in PMA. These findings suggested that partially deacetylated KG was more promising than native or highly deacetylated KG in PMA. Furthermore, scanning electron microscopy revealed that the morphology of KG gradually changed from fine filaments, to coarse filaments, short filaments and granules as DD increased. This study provides a theoretical basis for the application of partially deacetylated KG in PMA.

A large number of hydrogen bonds is the main reason for hindering the dissolution and reaction of chitin, and a mild and green deacetylation method to prepare chitosan for a wider range of applications is urgent. As a non-toxic and degradable green solvent, the deep eutectic solvent can effectively interfere with the hydrogen bond network of chitin, making chitin more susceptible to other solvents. Therefore, a NADES system consisting of betaine and glycerol was proposed for application in the deacetylation reaction of chitin to facilitate further attack of N-acetyl groups by low concentrations of NaOH. After optimizing the reaction conditions, chitosan with 83.77 % deacetylation was prepared, requiring only a concentration of 25 wt% NaOH. The analysis of the product chitosan showed that NADES could not only effectively improve the degree of deacetylation, but also reduce the degree of damage to the molecular weight by alkali. In addition, the potential mechanisms involved in the deacetylation process by NADES were explored. The nature of the reaction was verified by FT-IR, XRD and theoretical calculations as the process of opening intra/intermolecular hydrogen bonds of chitin by NADES. More importantly, experimental and in-depth theoretical studies provide a reference for the green preparation of chitosan.

Unless better measures are put in place to address the environmental and social impacts emanating from the huge waste generated from sea food processing industries; \'tragedy of the commons\' is inevitable. Needless to re-emphasise the enormous contributions of aquaculture as the perfect substitute to capture fisheries which has been proven unsustainable. Be that as it may, the huge amount of bio-waste produced could be transformed into useful products such as chitin and chitosan with far reaching applications. Chitin and chitosan have been consistently processed from many sources following the traditional chemical sequence of Demineralization (DM), Deproteinization (DP), Decolouration (DC) and Deacetylation (DA). In this study, this method was re-ordered, resulting to 4 sequences of chemical processes. HCl, NaOH, ethanol (97%) and NaOH (50%) were used for DM, DP, DC and DA respectively. The results of this study showed that better chitin (23.99 ± 0.61%) and chitosan (15.17 ± 1.69%) yields were obtained from sequence four (SQ4) following the order of DC-DM-DP-DA. In addition, physicochemical properties such as DDA (80.67 ± 2.52%) and solubility (66.43 ± 2.61%) were significantly higher (p ≤ 0.05) in SQ4 thereby making the obtained product suitable for use as coagulant and flocculant in wastewater treatment. Results of FTIR, XRD and SEM of the study proved that the resultant product exhibited the characteristic nature of chitosan with porous and fibril nature. In the analysis of the physical properties of chitosan obtained from bio-waste of Macrobrachium rosenbergii, the high Carr\'s index (CI) and low bulk as well as tapped densities were an indication that the chitosan produced in this study had poor flowability and compressibility, thereby making it unfit for application in pharmaceutical industries.