Valorization of guinea grass seed (Megathyrsus maximus): Synthesis and utilization of cellulose microfiber to reinforce esterified and cross-linked guinea starch films

The present study extracts starch from guinea grass seed and fiber from the starch extraction residue. The fibrous residue was chemically converted into cellulose microfiber (CMF) and used to reinforce the native, esterified and crosslinked guinea starch films. The films were developed with 5 % starch, 40 % glycerol and 0, 2.5, 5, and 10 % CMF based on the dry matter of starch. SEM images of all film samples showed good compatibility of CMF with starch molecules, and no fractures or pores were observed. Adding filler materials to modified starch films slightly increased the film thickness (0.24 to 0.30 mm) due to the high dimensions of CMF, which comprise a significant amount of the composite's volume. A synergetic effect of starch modification and CMF in films decreased the moisture content (21.98 to 9.21 %), water solubility (25.65 to 15.47 %), water vapor permeability (6.96×10-7 to 1.65×10-7g∙mm2∙day∙Pa), and elongation at the break (33.51 to 16.79 %) while increasing the tensile strength (1.84 to 3.85 MPa) and Young's modulus (5.49 to 22.93 MPa). The L* and a* values of the films decreased, and the b* and opacity values of the films increased with the addition of CMF. The XRD graph showed that all films have semicrystalline structures with peaks at 18°, 20°, and 22°, and the degree of crystallinity increases (32.3 to 55.1 %) with CMF. All film samples showed good thermal stability up to 315 °C. In conclusion, esterified starch-based films exhibited superior barrier properties and flexibility. On the contrary, cross-linked starch films demonstrated higher tensile strength and lower water solubility.

Synthesis, optimization, and characterization of precipitation derived starch nanoparticles from guinea seeds

Guinea starch nanoparticles (GS-SNP) were developed using ultrasound and nanoprecipitation techniques. The physicochemical, thermal, structural, morphological, pasting, and rheological properties of GS-SNP were examined and compared with native starch. The particle size of GS-SNP was 391.50-206.00 nm, with a PDI of 0.35-0.23 and a zeta potential of -37.5 to -13 mV. The amylose content of GS-SNP increased with a decrease in relative crystallinity, and a VH-type crystalline structure was observed. The GS-SNP were in round shape with some self-aggregated granules. The water and oil absorption capacity, solubility, and gelatinization temperature of GS-SNP increased, but the swelling power was restricted. The viscosity of the GS-SNP dispersion remained almost constant throughout the heating but slightly increased after cooling. A higher degree of shear thinning was observed due to a fluid-like gel network and weak gel structure. The optimum conditions were: 50 % amplitude, 30 min time, and a starch to ethanol ratio (1:4) with 85 % maximum desirability. Overall, the findings suggest that GS-SNP have promising potential for application in a liquid system where viscosity of the system cannot be significantly influenced by temperature.

Advances in isolation, characterization, modification, and application of Chenopodium starch: A comprehensive review

The Chenopodium genus includes >250 species, among which only quinoa, pigweed, djulis, and kaniwa have been explored for starches. Chenopodium is a non-conventional and rich source of starch, which has been found effective in producing different classes of food. Chenopodium starches are characterized by their smaller granule size (0.4-3.5 μm), higher swelling index, shorter/lower gelatinization regions/temperature, good emulsifying properties, and high digestibility, making them suitable for food applications. However, most of the investigations into Chenopodium starches are in the primary stages (isolation, modification, and characterization), except for quinoa. This review comprehensively explores the major developments in Chenopodium starch research, emphasizing isolation, structural composition, functionality, hydrolysis, modification, and application. A critical analysis of the trends, limitations, and scope of these starches for novel food applications has also been provided to promote further scientific advancement in the field.