Application of supercritical carbon dioxide to enhance the aroma of whole sorghum flour for use in 3D printing of sorghum cookies.

Sorghum is a promising ingredient for new food products due to its high fiber content, slow digestibility, drought resistance, and gluten-free nature. One of the main challenges in sorghum-based products is the unpleasant aroma compounds found in grain sorghum. Therefore, in this study, sorghum flour was treated via supercritical carbon dioxide (SC-CO2) to remove undesired aroma compounds. The resulting SC-CO2-treated flours were used to generate dough for 3D food printing. At the optimized conditions, sorghum cookies were 3D-printed using 60 % water and a nozzle diameter of 1.5 mm. All dough samples produced with untreated and SC-CO2-treated sorghum flours exhibited shear-thinning behavior. Changing the treatment pressure (8-15 MPa) or temperature (40-60 °C) did not significantly affect the viscosity of the dough samples. Moreover, the sorghum cookie doughs had higher G' and G″ values after the SC-CO2 treatments (G' > G″). Doughs generated from flours treated at 15 MPa - 40 °C and 8 MPa - 60 °C showed lower adhesiveness compared to the ones produced from untreated flour, whereas 15 MPa - 60 °C treatment did not affect the adhesiveness. After baking, the 3D-printed cookies from SC-CO2-treated flour exhibited significantly lower redness (a*), but the hardness of the cookies was not affected by SC-CO2 treatment. Overall, the SC-CO2 treatment of sorghum flour did not negatively affect the quality parameters of the 3D-printed cookies while enhancing the aroma of the flour.

Effect of a novel drying method based on supercritical carbon dioxide on the physicochemical properties of sorghum proteins.

The aim of this research was to use supercritical carbon dioxide (SC-CO2) drying as a novel approach for generating sorghum protein concentrates/isolates with enhanced functional properties. Sorghum protein extracts were obtained from white whole-grain sorghum flour and were dried by two methods, namely, freeze-drying and SC-CO2 drying. The collected proteins were characterized for their morphology, color, crystallinity, surface hydrophobicity, emulsifying activity index (EAI), creaming index (CI), foaming capacity (FC), foaming stability (FS), protein solubility, chemical interactions, and viscosity. The SC-CO2-dried proteins exhibited higher porosity compared to the freeze-dried ones with smaller particle sizes (∼5.1 vs. 0.4 µm, respectively). The XRD patterns indicated that the SC-CO2-dried proteins had a lower crystallinity than the freeze-dried proteins. However, the surface hydrophobicities of the freeze-dried and SC-CO2-dried proteins were similar. The EAI results showed that the emulsifying activity of freeze-dried protein powder (40.6) was better than that of SC-CO2-dried protein powder (29.8). Nevertheless, the solubility of SC-CO2-dried proteins was higher than that of freeze-dried proteins in most of the pHs investigated. Overall, the proposed SC-CO2 drying method has the potential to generate porous protein powders with improved solubility that can be used in developing functional foods.

High hydrostatic pressure-assisted extraction of lipids from Lipomyces starkeyi biomass.

The purpose of this study is to evaluate the effect of high hydrostatic pressure (HHP) as a novel approach for yeast cell disruption and lipid extraction from Lipomyces starkeyi DSM 70295 grown in glucose medium (40 g/L and C/N:55/1) at initial pH of 5.0, 25°C, and 130 rpm for 8 days. HHP extraction conditions including pressure, time, and temperature were optimized by response surface methodology. The high speed homogenizer-assisted extraction (HSH) was also used for comparison. The biomass subjected to HHP was examined under scanning electron microscopy and light microscope. A maximal lipid yield of 45.8 ± 2.1% in dry cell basis (w/w) was achieved at 200 MPa, 40°C, and 15 min, while a minimum yield of 15.2 ± 0.9% was observed at 300 MPa, 40°C, and 10 min (p < 0.05). The lipid yield decreased with increasing pressure. It was demonstrated that low pressure (200 MPa) collapsed the cells, while high pressure (400 MPa) created protrusions on the cell wall and cell fragments spread in the environment. This study favors HHP as a promising method for Lipomyces oil extraction. PRACTICAL APPLICATION: Single-cell oils are considered future alternatives to plant-based oils as food additives and dietary supplements. Oleaginous microorganisms accumulate oils in their cell plasma, which makes extraction essential. One of the main obstacles with existing methods is the utilization of strong acids to destroy cell walls. This study aims to demonstrate high hydrostatic pressure as a rapid method for lipid extraction from oleaginous yeast Lipomyces starkeyi.