Corrigendum to "Evaluation of freeze-dried phenolic extract from cashew apple by-product: Physical properties, in vitro gastric digestion and chemometric analysis of the powders" [Food Chemistry: Molecular Sciences 5 (2022) 100149].

[This corrects the article DOI: 10.1016/j.fochms.2022.100149.].

Effect of devitrification on the survival and resistance of dried Saccharomyces cerevisiae yeast.

Yeasts are anhydrobiotes that accumulate large amounts of trehalose, which is involved in the vitrification of the cytoplasm during drastic desiccation. The effect of devitrification, which can be induced by the transient exposure of desiccated yeasts to increased humidity or elevated temperature, on the survival of yeast has been studied. A glass transition temperature (Tg)/water activity (aw) diagram of yeast was constructed based on differential scanning calorimetry analysis. The survival rate of yeasts that were equilibrated at different relative humidities (RHs) and temperature values over their Tg range was measured. The results revealed a long period of cell preservation at an intermediate RH (55%), with 100% survival observed after 3 months, a loss of 1.24 log colony-forming units/g recorded after 1 year at 25 °C and full preservation of viability at 75 °C for 60 min and at 100 °C and 12% RH for up to 10 min. These findings led us to conclude that dried yeast can resist low or intermediate RH values and elevated temperatures in the devitrified state. Considering the thermal and humidity fluctuations occurring in the yeast environments, we hypothesized that the supercooled state, which occurs immediately above the Tg after rehydration or heating, is a protective state that is involved in the persistence of yeasts at intermediate humidity levels. KEY POINTS: • Yeast survival for months in a supercooled state is observed at room temperature. • Dried yeasts survive a 10-min exposure to 100 °C in the supercooled state. • The supercooled state is suitable for yeast preservation.

Efficient stabilisation of curcumin microencapsulated into yeast cells via osmoporation.

This study proposes the investigation of curcumin encapsulation into Saccharomyces cerevisiae cells through osmoporation as an efficient way of increasing curcumin stability. The influence of three process parameters (cell, ethanol and curcumin concentrations) on the encapsulation process was evaluated, and the obtained biocapsules were characterised for physical and photochemical stabilisation. Results showed that encapsulation efficiency was favoured by the increase of cells/curcumin ratio and ethanol concentration up to 60%. Differential scanning calorimetry (DSC) curves revealed that yeast encapsulation delayed the curcumin melting point up to 207 °C. Encapsulated curcumin retained over 80% of antioxidant activity after thermal treatment (150 °C) and over 70% after a 50-day exposure to artificial light. Photochemical stability of yeast-encapsulated curcumin was increased by 5.7-fold, and half-life time reached 181 days under illumination conditions. Overall, osmoporation-produced yeast biocapsules confirmed the versatility of osmoporation as an encapsulation technique and successfully improved curcumin stability.

Water and temperature contribution to the structuration of starch matrices in the presence of flavour.

The effect of modulating the gelatinisation extent by hydration (50/50 and 80/20 water to starch ratio) and temperature (65 or 85 °C) on various properties of wheat starch in presence of flavours has been studied. The hydrothermal treatments resulted in samples with different properties. The lowest residual flavour content was found in samples treated at the highest hydration and temperature (85 °C) while the other treatment conditions led to samples with similar residual flavour content. Ethyl hexanoate significantly increased the characteristic pasting viscosities compared to starch±2-hexanone; suggesting a greater structuration with ethyl hexanoate. Heating starch in excess water caused amylopectin melting, but promoted an incomplete granular swelling as revealed by RVA. This study suggested that lowering the hydration upon treatment could limit both crystal melting (with a residual crystalline content up to 38% in the most extreme conditions) and granular swelling but increased granule organisation like following annealing.

New insights on the thermal analysis of low moisture composite foods.

Low moisture baked products were investigated with a view to characterising the effect of both formulation and humidity on their physical stability. At the end of the baking process, the samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with differential scanning calorimetry and their glass transitions were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat flow. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a plasticizer (sugar)-rich phase whose behavior depended on the sample water content. This novel approach of thermal properties suggested new insights: considering the phase behavior of complex systems and thus the properties of their individual phases could contribute to a better understanding of the physical stability of the products.

Effect of water on glass transition in starch/sucrose matrices investigated through positron annihilation lifetime spectroscopy: a new approach.

Glass transition is studied through positron annihilation lifetime spectroscopy (PALS) in maize starch matrices containing 10 (batch STS10) and 20 (STS20) w/w% sucrose, as a function of temperature (T) and water content (c(w)). To circumvent important losses of water upon heating while recording the PALS spectra, a new method is developed: instead of a series of measurements of τ(3), the triplet positronium lifetime, at different T, the latter is kept constant and the series relates to c(w), which is left to decrease at a constant rate. Similarly to the changes in τ(3) with T, the τ(3)vs. c(w) plots obtained show a smooth linear increase until a break, denoting the occurrence of glass transition, followed by a sharper increase. The gradients appear to be independent of T. The variation of the glass transition temperature, T(g), with c(w) shows a broad sigmoid with a large linear central part; as expected from the plasticising effect of sucrose, the plot for STS20 lies some 10 K below that for STS10. Results from differential scanning calorimetry for STS20 yield T(g) values some 15 K higher than from PALS. On the basis of the general shape of the τ(3)vs. T variations, a general equation is set for τ(3)(T, c(w)), leading one to expect a similar shape for τ(3)vs. c(w), as experimentally observed.

Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition processes.

The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition. Unexpectedly, the starch volume fraction (as probed through thermal gravimetry) decreases with T at a higher rate than the free volume fraction (as probed through PALS).

Influence of sucrose and water content on molecular mobility in starch-based glasses as assessed through structure and secondary relaxation.

Molecular mobility is known to be a key parameter in controlling the physical properties of materials and thus their quality and performance. Beyond glass transition related changes, attention should be called to the impact of local motions remaining in the glassy state. Gelatinized waxy maize starch at different sucrose contents (0-20% solids) was equilibrated between 0 and 14% water and sorption isotherms determined at 25 degrees C. The effect of water and sucrose content on the molecular mobility of glassy starch was investigated by differential scanning calorimetry through enthalpy relaxation studies and dynamical mechanical thermal analysis. The existence of sucrose-starch interactions was suggested by the sorption isotherms not following the expected additivity of the single component sorption curves. Contrary to the glass transition or associated alpha relaxation, water and sucrose affected differently the secondary relaxations. Indeed, the beta relaxation observed around -15 degrees C was shifted to lower temperature upon increasing hydration, and to higher temperature when sucrose content increased, suggesting a hindering of these local motions. Enthalpy relaxation of the ternary mixtures was studied following aging up to 668 h at Tg -15 degrees C. Ternary mixtures exhibited an enthalpy relaxation upon aging lower than starch alone as a sign of lower polymer mobility in the presence of small molecules, contrary to the free volume theory. Relaxation kinetics were characterized with the Cowie-Ferguson model and compared to literature data. The extent of the enthalpy relaxation appeared to be controlled by the distance between the aging temperature and the beta relaxation temperature.

Study of release kinetics of small and high molecular weight substances dispersed into spray-dried ethylcellulose microspheres.

Spray-dried ethylcellulose microspheres were used as matrices for the encapsulation of a fungal lactase and/or small paramagnetic probes (Tempol or Tempo). Their dissolution in water was studied. Kinetics fitted with the model Q = kt(n) of Korsemeyer et al. [Int. J. Pharm. 15 (1983) 25] exhibited a non-Fickian diffusion. The calculated diffusional exponent (n) values were near 0.26 whatever the encapsulated probes. The release rates (k) were only slightly different for paramagnetic probes and lactase. This result indicated that the probes' release mechanisms are not diffusion controlled. Other factors such as matrix porosity and probe solubility in the matrix and in water could influence the probes' release rate.