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Bananas' mechanical properties are affected by the ripening and the drying processes since they induce profound microstructural changes. In this study, first, the interacting effect of the ripening and the drying processes on the mode of viscoelastic behavior of bananas was investigated. Second, the stress relaxation properties of fully ripe bananas were measured as a function of the hot air drying conditions. Finally, the two‐element generalized Maxwell model was fitted to the experimental data. Thus, this study clarified the dependence of the mode of rheological behavior on both the ripening stage and the moisture content. It showed that bananas start softening at the onset of the drying when the fruit moisture content is high. The softening is reversed at a critical value, at which the bananas start regaining stiffness with further moisture reduction. The critical moisture content value decreases with ripening from 1.4 g/g solids for green bananas (5–11% Brix percentage) to 1.23 g/g solids for half‐ripe bananas (15–20% Brix percentage) and eventually vanishes when the bananas are fully ripe (25–31% Brix percentage). The stress relaxation properties measured with fully ripe bananas substantiated the initial findings on the influence of the ripening stage on the mode of rheological behavior. The relaxation moduli displayed a decreasing trend with decrease in the moisture content for 40, 60, and 80°C drying temperatures and decayed with time as expected for viscoelastic bodies. Lastly, the two‐element generalized Maxwell model fitted well to the experimental data with the root mean square error varying between 0.06 × 10⁻⁵and 90.6 × 10⁻⁵MPa.

 

It is essential to understand the physical and mechanical properties of a product since these properties affect the structure, texture, and ultimately consumer acceptance. The effect of drying conditions on dynamic viscoelastic properties, stress relaxation function and creep compliance, and physical properties, such as moisture distribution, color parameters, and shrinkage, was studied. An increase in drying temperature and duration resulted in a decrease in moisture content and volume, which were highly correlated (R= .988). Water evaporation followed the falling rate period, demonstrating that the water transport was limited by internal resistances. The decomposition of carotenoids led to a decrease in magnitude of color parameters (L,a, andb), between 30.1% and 51.6% with 4 hr drying. It was observed that the material shrinkage and moisture content highly affected the mechanical properties; increased stress relaxation modulus and decreased creep compliance values of the sample. The creep behavior, expressed with Burger's model (R² ≥ .986), was highly dependent on moisture content. The linear viscoelastic region of carrots was found to be at strains lower than 3%. The three‐element Maxwell model well fitted to describe the viscoelastic behavior of carrots (R² ≥ .999,RMSE ≤ 2.08 × 10⁻⁴). The storage moduli (G′) were higher than loss moduli (G″), indicating that samples presented solid‐like behavior. The findings can be used to improve the textural attributes of carrots and carrot‐based products.

 

Emerging portable near infrared (NIR) spectroscopic approaches coupled with data analysis and chemometric techniques provide opportunities for the rapid characterization of spray-dried products and process optimization. This study aimed to enhance the understanding of applying NIR spectroscopy in spray-dried samples by comparing two sample preparation strategies and two spectrometers. Two sets of whey protein–maltodextrin matrixes, one with a protein content gradient and one with a consistent protein content, were spray-dried, and the effect of the two preparation strategies on NIR calibration model development was studied. Secondly, a portable NIR spectrometer (PEAK) was compared with a benchtop NIR spectrometer (CARY) for the moisture analysis of prepared samples. When validating models with the samples with focused protein contents, the best PLS protein models established from the two sample sets had similar performances. When comparing two spectrometers, although CARY outperformed PEAK, PEAK still demonstrated reliable performance for moisture analysis, indicating that it is capable as an inline sensor. 

Separation of liquid mixtures, frequently by distillation, is ubiquitous in the chemical and process industries (CPI). Distillation accounts for ~95% of the energy used in liquid separations, ~25–40% of overall energy used in CPI, and ~3% of global energy consumption.1-2 The low efficiency of distillation is largely due to two issues. First, there are large irreversible losses due to heat transfer.3 Second, a significant fraction of energy used in liquid separations is used to separate azeotropic mixtures in azeotrope-forming systems (e.g., ethanol/water). While a number of conventional distillation technologies4-5 (e.g., pressure-swing, extractive distillation, and azeotropic distillation6) and new separation approaches5 (e.g., dividing-wall columns, membranes, molecular sieves, and bio-absorbance) have been developed for azeotropic systems, these approaches largely rely on thermal separation via phase equilibrium or involve large capital and/or operational costs.