Concept Of Glass Transition Temperature Research Articles

Kinetics of phytate hydrolysis during storage of red kidney beans and the implication in hard-to-cook development

In this study, the kinetics of phytate (inositol hexaphosphate, InsP6) hydrolysis by endogenous phytase in red kidney beans stored at varying conditions of temperature (25–42 °C) and moisture content (6.9–14.5%) was determined and the potential role in hard-to-cook (HTC) development was evaluated. In addition, the concept of glass transition temperature (Tg) was assessed and correlated against the rate of phytate hydrolysis. Under the conditions studied, phytate hydrolysis during storage was mainly influenced by storage temperature and time with limited influence of storage moisture content whereby the highest and lowest storage temperatures (42 °C and 25 °C) resulted in the highest and lowest hydrolysis rates (0.058 ± 0.003 and 0.003 ± 0.001 week−1). Hydrolysis of phytate resulted in formation of lower inositol phosphates, inositol pentaphosphate (InsP5) representing an intermediate whose concentration increased with storage time and temperature. The relationship between the rate of InsP6 hydrolysis and storage above the overall Tg (T − Tg) was moisture content dependent implying that this difference did not fully explain InsP6 hydrolysis. Nevertheless, for each moisture content, the rates of InsP6 hydrolysis during storage were strongly correlated (r > 0.98, p < 0.05) with rates of HTC development signifying that InsP6 hydrolysis facilitates HTC development in beans.

Understanding the Relations Among the Storage, Soaking, and Cooking Behavior of Pulses: A Scientific Basis for Innovations in Sustainable Foods for the Future.

The world faces challenges that require sustainable solutions: food and nutrition insecurity; replacement of animal-based protein sources; and increasing demand for convenient, nutritious, and health-beneficial foods; as well as functional ingredients. The irrefutable potential of pulses as future sustainable food systems is undermined by the hardening phenomenon that develops upon their storage under adverse conditions of temperature and relative humidity. Occurrence of this phenomenon indicates storage instability. In this review, the application of a material science approach, in particular the glass transition temperature concept, is presented to explain phenomena of storage instability such as the occurrence of hardening and loss of viability under adverse storage conditions. In addition to storage (in)stability, application of this concept during processing of pulses is discussed. The state-of-the-art on how hardening occurs, that is, mechanistic insights, is provided, including a critical evaluation of some of the existing postulations using recent research findings. Moreover, the influence of hardening on the properties and processing of pulses is included. Prevention of hardening and curative actions for pulses affected by the hardening phenomenon are described in addition to the current trends on uses of pulses and pulse-derived products. Based on the knowledge progress presented in this review, suggestions for the future include: first, the need for innovation toward implementation of recommended solutions for the prevention of hardening; second, the optimization of the identified most effective and efficient curative action against hardening; and third, areas to focus on for elucidation of mechanisms of hardening, although existing analytical methods require advancement.

Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C

Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35-0.90 a(w) , whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 a(w) . Blahovec-Yanniotis was considered to give the best fit over the whole range of a(w) tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec-Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (T (g)) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the T (g) line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.

MOISTURE ADSORPTION CHARACTERISTICS OF BLACK CURRANT (RIBES NIGRUM L.), BLACK ELDERBERRY (SAMBUCUS NIGRA L.) AND CHOKEBERRY (ARONIA MELANOCARPA, [MINCHX.] ELL.) SAMPLES AT DIFFERENT TEMPERATURES

ABSTRACTAdsorption isotherms of black currant, black elderberry and chokeberry were obtained at 10, 25 and 40C. Generally, increasing temperature decreased adsorbed moisture particularly at 10C, whereas the adsorption was similar at 25 and 40C in the range of 0.10–0.75 water activity (Aw) for all the berry samples. All the berries sorbed more water at 40C than at 10 or 25C above 0.75 Aw. Of the six sorption models, Peleg's model gave the best fit. The net isosteric heats of adsorption were obtained using Clausius–Clapeyron equation showing that the adsorbed water is strongly bound to adsorbent at low moisture content. The glass transition temperature concept was also discussed. Based on the results of the study and the literature reviewed, the chilled storage has a favorable effect on the quality and shelf life of the dried berries.PRACTICAL APPLICATIONSThe knowledge of the moisture content and water activity (Aw) relationships of food products is very important. These can be estimated by determining moisture sorption isotherm that can be used for defining storage conditions and in making shelf life determination. The unsuitable storage conditions may lead to deterioration of the product caused both by native enzymes and by microorganisms activity (Ross 2001). The sorption data for the berries are restricted for those used in human diet (Khalloufi et al. 2000) but have never been published for berries predominantly used in medicine. The results of this study would be useful in assessment of proper storage condition to keep the quality of the product in a high level.

A new method of producing date powder granules: Physicochemical characteristics of powder

A mixing technique was developed to produce free flowing powder granules from date. This method involved preparation of the paste from raw date, mixing with maltodextrin powder followed by an oven drying. In order to determine an optimum proportion of date paste and maltodextrin (DE 6) to produce stable granules, mixing was carried out at various levels of maltodextrin (MD) ranging between 0.54 kg and 1.0 kg per kg of date paste (dry weight basis). The date paste dried with 1.0 kg of maltodextrin/1.0 kg of date paste produced non sticky and free flowing powder. Several physicochemical parameters such as water activity, bulk density, color, hygroscopicity and glass transition temperatures of date powders were measured. The caking of date powders during storage at room temperature was explained using the concept of glass transition temperature.

Optimization of cocurrent spray drying process for sugar-rich foods. Part II—Optimization of spray drying process based on glass transition concept

A steady state mathematical model for cocurrent spray drying was used to find the optimal spray drying process for sugar-rich foods. Maltodextrin-sucrose solution was used as a sugar-rich food model. The optimization of the spray drying process was carried out by finding a set of inlet variables to minimize the between the outlet air temperature and the glass transition temperature of the final products. The minimization was simplified by approaching the outlet drying air and average powder moisture content with the polynomial equations of the inlet variables in a range of interest. The drying condition at the lowest between outlet air temperature and product glass transition temperature provided the highest powder recovery at the cyclone obtained from experiment. This result shows that the stickiness of a particular sugar-rich food in spray drying can be minimized by choosing proper inlet variables using the glass transition temperature concept.

Optimization of co-current spray drying process of sugar-rich foods. Part I—Moisture and glass transition temperature profile during drying

A steady state mathematical model for co-current spray drying was developed for sugar-rich foods with the application of the glass transition temperature concept. Maltodextrin–sucrose solution was used as a sugar-rich food model. The model included mass, heat and momentum balances for a single droplet drying as well as temperature and humidity profile of the drying medium. A log–normal volume distribution of the droplets was generated at the exit of the rotary atomizer. This generation created a certain number of bins to form a system of non-linear first-order differential equations as a function of the axial distance of the drying chamber. The model was used to calculate the changes of droplet diameter, density, temperature, moisture content and velocity in association with the change of air properties along the axial distance. The difference between the outlet air temperature and the glass transition temperature of the final products (Δ T) was considered as an indicator of stickiness of the particles in spray drying process. The calculated and experimental Δ T values were close, indicating successful validation of the model.