Impact of the polymer dispersity on the properties of curcumin/polyvinylpyrrolidone amorphous solid dispersions

Amorphous solid dispersions (ASD) are known to enhance the absorption of poorly water-soluble drugs. In this work we synthesise well-defined Polyvinylpyrrolidone (PVP) to establish the impact of dispersity and chain-end functionality on the physical properties of Curcumin (CUR)/PVP ASD. Thermodynamic characterisation of synthesised PVP emphasises a strong effect of the dispersity on the glass transition temperature (Tg), 50 °C higher for synthesised PVP than for commercial PVP K12 of same molar mass. This increase of Tg affects the thermodynamic properties of CUR/PVP ASD successfully formulated up to 70 wt% of CUR by milling or solvent evaporation. The evolution of both the Tg and CUR solubility values versus CUR content points out the development of fairly strong CUR-PVP interactions that strengthen the antiplasticising effect of PVP on the Tg of ASD. However, for ASD formulated with commercial PVP this effect is counterbalanced at low CUR content by a plasticising effect due to the shortest PVP chains. Moreover, the overlay of the phase and state diagrams highlights the strong impact of the polymer dispersity on the stability of CUR/PVP ASD. ASD formulated with low dispersity PVP are stable on larger temperature and concentration ranges than those formulated with PVP K12.

Ultrasonication assisted salt-spices impregnation in black carrots to attain anthocyanins stability, quality retention and antimicrobial efficacy on hot-air convective drying

The present study aims at optimisation of enhanced solute impregnation through ultrasonication (US) at 37 kHz using central composite design of response surface methodology (RSM). Black carrots were blanched at 98 °C/3 min followed by immersion in salt-spices based solutions for 8 h, treated with bath sonication at specific intervals (2, 4 & 6 h) for 5, 10 and 15 min. Responses for optimum water loss (WL), solute gain (SG), anthocyanins retention, texture and highest antioxidant activity were optimized in effect of NaCl%, spices mix% and US time. The suggested models were of good fit while lack of fit as non-significant (p < 0.0500). Best combination was compared for anthocyanins retention on pressure-cooking (120 °C/15 psi) with fresh, blanched, salt-spiced without US subjected to hot-air convective drying (55 °C/5 h). Ultrasonication-assisted salt-spiced convective dried (USPCD) carrots retained highest anthocyanin content (41%) post cooking which correlated with increased glass transition (T_g) and antimicrobial efficacy (as zone of inhibition) in comparison to fresh, blanched convective dried (BCD) and salt-spiced convective dried (SPCD) carrots. FTIR spectra suggested the correlation of textural effects with pectin degradation and solute impregnation. XRD spectra revealed changes in pectin (2θ = 22.06°) and NaCl crystallinity peaks at 2θ = 27.49, 31.86, 45.62, 56.68, 66.45 and 75.43°, owing to the processing of black carrots. The spectra also confirmed higher solute impregnation in USPCD than SPCD carrots. Scanning electron micrographs of USPCD also indicated higher impregnation through smallest pores visible in longitudinal section of carrot tissue structure, which also appeared to be polymeric network filled with higher solutes than SPCD. Taken together, US assisted solute impregnation might have provided protection to the anthocyanins degradation as well as retention of other quality parameters on processing.