Starch blends are a technological alternative aimed at the development of starchy matrices that exhibit improvements in some physicochemical properties from interactions between their individual components. Native cassava and yam starches were mixed in different proportions and the effect of the blend on the structural, physicochemical, and pasting properties was evaluated. The viscosity behavior as a function of temperature revealed a significant non-additive effect on the pasting parameters of all the blends with respect to the individual native starches. Similarly, non-additive variations were evident in the crystallinity index of some mix ratios (NSB-2: 40.11%). Likewise, the difference in the amylose content of each native starch (20.88-25.66%) possibly exerted an effect on the resulting semicrystalline characteristics of the blends and the gelatinization behavior. Hence, the botanical origin and the proportion of starch blends play an important role in the behavior of the resulting physicochemical properties and in vitro digestibility. Polymeric blends were obtained with a low tendency to retrogradation and lower crystallinity index values compared to their native counterparts and a regulated water absorption capacity, all potentially desirable characteristics in the food industry.

Cassava starch is modified to increase porosity and lacerations that are limited when only enzymatic treatments are used. This study proposes to improve enzymatic activity of α-amylase and amyloglucosidase on the polymer chains of cassava starch by implementing physical and thermal pretreatments below the gelatinization temperature and before the hydrolytic process. The pretreatments increased the biocatalytic action of the enzymes, causing significant changes in the morphology of the granules, and superficial lacerations were found in samples of starches pretreated with ultrasound (UTS) or annealing and ultra-rapid freezing (ANN-C). At the structural level, the modified starches revealed substantial changes as the infrared spectra reflected a displacement of the absorption bands in the region from 900 to 1100 cm-1. This is associated with an alteration and reorganization of the amorphous and crystalline zones of the granules and is consistent with a decrease in amylose content (from 19.53% to 17.64%) and an increase in the crystallinity index. The thermal behavior of the starches was also modified by increasing the peak temperature (from 68.22°C to 75.38°C) and reducing the gelatinization enthalpy (from 19.34 to 15.79 J/g). UTS and ANN-C pretreatments significantly improved the mesoporous and hydrophilic properties of the modified cassava starches.

This study aimed to assess the physical, chemical, and combustion properties of pellets made from corncob and rice husk residues sourced in Sucre, Colombia, and to evaluate the performance of different blending ratios. Before pelletization, the residues were ground and processed using a small-scale flat die pellet mill equipped with a 6 mm die. Physical properties were evaluated according to ISO standards for particle density, bulk density, and impact resistance assessment. Proximate and ultimate analyses, as well as heating values, were determined and compared against the ISO 17225-6:2021 classification for herbaceous biomass. The 70:30 corncob-to-rice husk blend (CC70:RH30) showed good quality, with 7.23% ash, 9.18% moisture, and an LHV of 15.19 MJ/kg, meeting the criteria for Class B pellets. Combustion performance was assessed using a custom-designed macro-TGA, revealing that co-pelletized blends exhibited improved ignition temperatures and comprehensive combustion indices compared to the individual feedstocks. Additionally, calorific values were proportional to the blending ratios. In summary, controlling the blending ratio of corncob and rice husk residues during pellet production allows modulation of both the total ash content and the lower heating value of the resulting solid biofuels, making them more suitable for thermochemical conversion routes such as combustion and/or gasification.