Spray-drying production of litchi powder is frequently constrained by low yield and unstable quality, largely attributable to variations in fruit sugar–acid profiles. To elucidate the compositional factors affecting powder performance, ten litchi cultivars with distinct sugar–acid ratios were processed under identical conditions. Baitangying produced superior powder with the highest yield (89.23±1.25%), solubility (98.17±0.49%), and glass transition temperature (52.17±2.00 ℃). Jizuili also performed well. Both high-sucrose, low-acidity cultivars demonstrated excellent drying efficiency and storage stability. Conversely, high-acid and reducing-sugar cultivars (Feizixiao, Guanxiangli) retained more moisture (> 7%) and showed lower glass transition temperature, suggesting inferior stability. Correlation analysis revealed that fructose (ρ = −0.794, p < 0.001) and titratable acidity (ρ = −0.770, p < 0.001) were negatively correlated with yield, while sucrose was positively associated with yield and color lightness (ρ = 0.630, p < 0.05). Antioxidant capacity varied among cultivars and was mainly governed by total phenolics and litchi thaumatin-like protein, with Feizixiao and Jingganghongnuo showing the highest FRAP values (19.36 ± 0.12 and 17.38 ± 0.33 μg TE/mg DW). Overall, intrinsic sugar–acid profiles fundamentally determine the drying efficiency, powder stability, and bioactive retention of litchi powder.

Paraffin-based nanofluids have higher thermal conductivities compared to the paraffins, which makes them potential useful in thermal energy storage. However, few studies have been conducted on the solidification structure of paraffin-based nanofluids which directly decides whether or not they can be reused for energy storage. This paper investigated the effects of surfactant and ultrasound on the solidification behaviors of Al/Paraffin nanofluid. Sodium dodecyl sulfonate (SDS), polyvinyl pyrrolidone (PVP) and cetyl trimethyl ammonium bromide (CTAB) were used as surfactants to prepare Al/Paraffin nanofluids. Al/SDS/Paraffin, Al/PVP/Paraffin and Al/CTAB/Paraffin nanofluids as well as Al/Paraffin nanofluid without surfactant were cooled down with and without ultrasonic vibration. An environmental scanning electron microscope was used to measure the solidification structures of paraffin-based nanofluids. The Al/Paraffin nanofluid was found to solidify in the form of annulus icing. The advancing solidification front pushed the Al nanoparticles to the middle of container, resulting in the aggregation of Al nanoparticles there. The Al micro-aggregates settled down quickly during the subsequent melting process, bring out the failure problem of Al/Paraffin nanofluid. Surfactants CTAB, PVP and SDS couldn’t solve this failure problem of Al/Paraffin nanofluid fundamentally, but ultrasonic vibration could. The SEM images of solidified paraffin-based nanofluids with ultrasonic vibration showed that the Al nano-aggregates distributed evenly in the paraffin. It was found that solidification of each paraffin-based nanofluid assisted by ultrasonic vibration almost took place simultaneously throughout the container. We therefore obtained that ultrasonic vibration could promote the heterogeneous nucleation on Al nanoparticles mainly by reducing the temperature inhomogeneity in paraffin-based nanofluids.