Hygroscopic Properties of Sweet Cherry Powder: Thermodynamic Properties and Microstructural Changes

Understanding sorption isotherms is crucial in food science for optimizing the drying processes, enhancing the shelf-life of food, and maintaining food quality during storage. This study investigated the isotherms of sweet cherry powder (SCP) using the static gravimetric method. The experimental water sorption curves of lyophilized sweet cherry powder were determined at 30°C, 40°C, and 50°C. The curves were then fitted to six isotherm models: Modified GAB, Halsey, Smith, Oswin, Caurie, and Kühn models. To define the energy associated with the sorption process, the isosteric sorption heat, differential entropy, and spreading pressure were derived from the isotherms. Among the six models, the Smith model is the most reliable in predicting the sorption of the cherry powder with a determination coefficient (R2) of 0.9978 and a mean relative error (MRE) ≤1.61. The values of the net isosteric heat and differential entropy for the cherry increased exponentially as the moisture content decreased. The net isosteric heat values varied from 10.63 to 90.97 kJ mol−1, while the differential entropy values varied from 27.94 to 273.39 J. mol−1K−1. Overall, the enthalpy-entropy compensation theory showed that enthalpy-controlled mechanisms could be used to regulate water adsorption in cherry powders.

When Thermodynamic Properties of Adsorbed Films Depend on Size: Fundamental Theory and Case Study

Small system properties are known to depend on geometric variables in ways that are insignificant for macroscopic systems. Small system considerations are therefore usually added to the conventional description as needed. This paper presents a thermodynamic analysis of adsorbed films of any size in a systematic and general way within the framework of Hill’s nanothermodynamics. Hill showed how to deal with size and shape as variables in a systematic manner. By doing this, the common thermodynamic equations for adsorption are changed. We derived the governing thermodynamic relations characteristic of adsorption in small systems, and point out the important distinctions between these and the corresponding conventional relations for macroscopic systems. We present operational versions of the relations specialized for adsorption of gas on colloid particles, and we applied them to analyze molecular simulation data. As an illustration of their use, we report results for CO2 adsorbed on graphite spheres. We focus on the spreading pressure, and the entropy and enthalpy of adsorption, and show how the intensive properties are affected by the size of the surface, a feature specific to small systems. The subdivision potential of the film is presented for the first time, as a measure of the film’s smallness. For the system chosen, it contributes with a substantial part to the film enthalpy. This work can be considered an extension and application of the nanothermodynamic theory developed by Hill. It provides a foundation for future thermodynamic analyses of size- and shape-dependent adsorbed film systems, alternative to that presented by Gibbs.

An Experimental Study on the Way Bottom Widening of Pier Foundations Affects Seismic Resistance

The resistance of a pier to horizontal loads, like seismic loads, is due to the flexural rigidity of its foundations and the horizontal subgrade reaction. In the event of a massive earthquake, the latter becomes very small because of the softening of the ground, while the structure may experience a large inertial force and lateral spreading pressure. Therefore, structures with high seismic resistance are required in areas with high seismicity. When a wide caisson is used as a pier foundation, a rotational resistance moment caused by the vertical subgrade reaction acting on the foundation bottom can be expected. Although this rotational resistance moment increases if the foundation is widened, in design practice the subgrade reaction coefficient is evaluated as being low under such circumstances. Therefore, even if the foundation is widened, the rotational resistance moment does not increase greatly. Rotational resistance commensurate with the increased construction cost due to foundation widening cannot be expected. In the present study, horizontal loading experiments were performed at one pier with a normal foundation and at one with widened at the bottom foundation, and the way that the widening affected the seismic performance was examined. The results show that compared with the normal foundation, the bottom-widened one experienced far less displacement and offered higher earthquake resistance.

Thermodynamic Properties and State Diagram of Gum Ghatti-Based Edible Films: Effects of Glycerol and Nisin

In this present study, the thermodynamic and thermal properties of glycerol and nisin-incorporated gum ghatti (GG, Anogeissus latifolia)-based films were determined. The films exhibited type III isotherm behaviors. Moisture content (MC) of films was increased with increasing water activity (aw) and decreased with higher temperature. The incorporation of glycerol and nisin increased the sorption ability of GG films. The net isosteric heat of adsorption (qst) and differential entropy (Sd) were decreased with increasing MC, showing an exponential negative correlation between them. Spreading pressure (φ) was increased with increasing aw, but decreased with higher temperature. This incorporation of glycerol and nisin increased the qst, Sd and φ of the GG films. The sorption behaviors were enthalpy-driven and non-spontaneous processes. The glass transition temperature (Tg), critical MC and aw of the films were decreased, and increased respectively with the incorporation of glycerol and nisin. This work provides a theoretical basis for the application of edible films in fresh food preservation.

Experimental Study of the Lateral Spreading Pressure Acting on a Pile Foundation During Earthquakes

In the seismic design of pile foundations, the safety of the pile is assessed by considering the inertial force during an earthquake and subgrade reaction as external forces against the pile. The amount of deformation of the pile must be limited to a small value to maintain the safety of the pile. In the event of a large earthquake, quay walls and seawalls are subjected to lateral spreading because of the influence of biased seaward earth pressure. The amount of lateral spreading is considerably larger than what can be expected in a typical pile seismic design and may reach several meters. In this study, loading experiments that reproduced lateral spreading were conducted to evaluate the lateral spreading pressure acting on a pile when considerably large lateral spreading occurred. The experiment results showed that lateral spreading pressure depended on the ratio of pile spacing to pile diameter while the peak value of lateral spreading pressure was larger than the one assumed in practical design.

Moisture sorption isotherm and thermodynamic properties of jamun (Syzygium cumini L.) powder made from jamun pulp and seed

The present work aimed to: i) find the suitable proportion, based on sensory evaluation, of microwave-convective hot air dried jamun (Syzygium cumini L.) pulp and seed kernel powder to be mixed for the preparation of jamun powder (JP); ii) generate and model the moisture sorption isotherm (MSI) of JP; and iii) estimate net isosteric heat of sorption (qst), spreading pressure (φ), net integral enthalpy (Qin), and net integral entropy (Sin). To formulate JP, the proportion (w/w, db) comprising 2% kernel and 98% pulp powder was the most desirable. The Peleg model was the best fit to MSI of JP. The qst decreased following linear relationship from 11.02 kJ. mol-1 at 5% equilibrium moisture content (EMC) to 0.27 kJ. mol-1 at 30% EMC. The φ increased with increase in water activity and decreased with increase in temperature from 25 ºC to 35 ºC, and the values of φ at 45 ºC were even higher than at 25 ºC. Net integral enthalpy (Qin) initially decreased till 6% moisture content in JP and displayed an increasing trend with further increase in moisture content. On the contrary, Sin, kept on decreasing continually with increasing moisture content. The moisture zone of 7-11% was considered safe for storage for storage of JP within the temperature range of 45-25 ºC.