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Importance of Normality Testing, Parametric and Non-Parametric Approach, Association, Correlation and Linear Regression (Multiple & Multivariate) of Data in Food & Bio-Process Engineering
Published in Surajbhan Sevda, Anoop Singh, Mathematical and Statistical Applications in Food Engineering, 2020
Moisture sorption isotherm plays an important role for the long-term storage of dried and packaged foods. As the permeability of the packaging film is main concern for shelf life enhancement of the product, the use of GAB model is more appropriate than all other models to determine the sorption isotherm. It has been observed that the nonlinear regression analysis based on standard GAB equation helps in minimizing the experimental error and influenced the resulting constants, rather than transformed GAB model (Samaniego-Esguerra et al., 1991). The unfavorable condition has been avoided by weighting the square of residuals with the variance of data at each aw (water activity) level.
Drying
Published in C. Anandharamakrishnan, S. Padma Ishwarya, Essentials and Applications of Food Engineering, 2019
C. Anandharamakrishnan, S. Padma Ishwarya
Water activity relates to the proportion of available water which facilitates the chemical reactions and microbial growth in foods. A graphical representation of the relationship between moisture content and water activity of a food is known as the moisture sorption isotherm (Figure 10.2). The shape of moisture sorption isotherm is characteristic of the chemical composition, physical structure, and nature of the water binding in the food. The moisture sorption isotherms can be plotted from adsorption (wetting or gain of moisture until equilibrium is attained with the surrounding of high RH) or desorption (drying or loss of moisture until equilibrium is attained with the surrounding of low RH). The difference between the adsorption and desorption curves is known as hysteresis (Figure 10.2). Obtaining an understanding of the moisture sorption isotherms is relevant from the perspectives of design and optimization of drying equipment.
Food Dehydration
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Martin R. Okos, Osvaldo Campanella, Ganesan Narsimhan, Rakesh K. Singh, A. C. Weitnauer
From a knowledge of moisture binding energy, the moisture sorption isotherm at a different temperature can be predicted.Example 11.1The average moisture binding energy of extruded pasta at moisture content of 10 g per 100 g of dry solid is 3000 cal/mol. If the water activity of extruded pasta at the moisture content stated is 0.35 at 35°C, predict the water activity of the sample at 50°C.SolutionFrom Equation 11.22. lnaw2aw1=EbR(1T1−1T2)As Eb = 3000 cal/mol, R = 1.987 cal/mole·K, T1 = 298 K, and T2 = 323 K,lnaw2aw1=30001.987(1298−1323)=0.392aw2aw1=1.48;aw2=0.518
Moisture sorption isotherm and thermodynamic properties of Centella asiatica L. (CAL) powder
Published in Chemical Engineering Communications, 2021
Mohammad Danial Azhar, Syafiza Abd Hashib, Ummi Kalthum Ibrahim, Nurul Asyikin Md Zaki, Norashikin Ahmad Zamanhuri, Norazah Abd Rahman
Presence of water in a food material is responsible for physical, chemical, microbiological, and enzymatic reactions and were known as the main causes of deterioration and changes in the material. Moisture sorption isotherm is a thermodynamic tool widely used in research to predict shelf-life and storage stability as well as understand the sorption mechanism between the material and water molecules (Abdenouri et al. 2010; Vidana et al. 2015). The isotherm can be defined as a relationship between equilibrium moisture content of the material (Xe) and water activity (aw) at a constant temperature and pressure (Edoun and Kuitche 2014). The method can predict an amount of water that a material can hold if it is exposed to an ambiance condition at a specified water activity and temperature (Sormoli and Langrish 2015). Several techniques have been used to determine sorption isotherm experimentally, however, static gravimetric is the most preferable method used among the researchers. Many mathematical models have been developed to describe the moisture sorption isotherm of a product. These models can be divided into several categories such as kinetic model based on a monolayer of water (BET model), semi-empirical model (Halsey model), and purely empirical model (Smith, Peleg, and Oswin models) (Muzaffar and Kumar 2016).
Effects of environmental temperature and relative humidity on the rehydration of dried pistachios
Published in Drying Technology, 2019
Water activity (aw) is a significant parameter for stability of the raw and processed agricultural products. It is a determinant for the growth of microorganisms on foods.[11] An increased water activity(aw) permits the formation of bacteria, yeast, and molds.[9] It is used to determine the sorption isotherm and to use the estimated optimal residual moisture content as a result of the drying process.[12,13] The knowledge of moisture sorption isotherm describes the relationship between the moisture content and equilibrium relative humidity; it also contributes in understanding the phenomena occurring during the drying or rehydration process of food[14] and the suitable packing and storage conditions.[15] Moisture effects shall become even more important if the used materials are exposed to air since they might absorb significant amounts of moisture[16] and change the water activity (aw) of food.[17,18] According to the thermodynamic principle, some conditions in defining water activity (aw) must be met. They include pure water (aw=1.00; aw=100%-RH), the equilibrium system, and the defined temperature. So, a linear relationship occurs between the RH% and the water activity (aw).[19] There is also a need of establishing the water activity (aw), preferentially at the temperature of storage .[20]
Hydrogels based on gelatin, xanthan gum, and cellulose obtained by reactive extrusion and thermopressing processes
Published in Preparative Biochemistry & Biotechnology, 2022
Jéssica F. Pereira, Beatriz M. Marim, Bruno M. Simões, Fabio Yamashita, Suzana Mali
Moisture sorption isotherm of a material describes the equilibrium relationship between water activity and moisture content at constant temperature, being useful to give insights about the moisture-binding characteristic of the studied material.[34,37,40] Moisture sorption isotherms and GAB model parameters are shown in Figure 7 and Table 3, respectively. As can be seeing from Figure 7, all samples showed similar patterns, with an increase close to linear in the equilibrium moisture content with increase of aw, which is typical of hydrophilic materials. It can be attributed to the water adsorption that are partially bound in the samples.[16]