Moisture Sorption Characteristics of Freeze Dried Blueberries

Abstract

Moisture sorption isotherms of freeze dried lowbush blueberries at 4, 16,25, 35, and 45°C were determined using indirect gravimetric method. Moisture sorption kinetics at these temperatures and 75% RH were also investigated. The isotherms followed a type III shape with a temperature inversion effect at 0.9 water activity. They were best described by the GAB equation. Net isosteric heat of moisture sorption in freeze dried blueberries, determined using the Clausius Clapeyron equation, varied from 5.5 to 0.25 kJ/mol as moisture content changed from 8 to 36% (dry basis). Moisture adsorption kinetics in freeze dried blueberries were well described by the first order kinetics equation. The rate constant followed the Arrhenius relationship with an activation energy of 38.6 kJ/mol.

Physical characterization of freeze-dried foam prepared from aloe vera gel and guar gum

“…2), the second stage also lasted 20 h, which corresponded to the equilibrium stage. A similar observation was reported by Lim et al (35). The drying rate data that is presented in Fig.…”

Kinetic Study of Convective Drying of Blueberry Variety O’neil (Vaccinium corymbosum L.)

“…The weight of the samples was taken every 15 days until reaching constant weight (equilibrium condition). The salts used to obtain a range of water activity of 0.10 to 0.95 included LiCl, KC2H3O2, MgCl2, K2CO3, NaNO2, KI, NaCl and KNO2 (Lim et al, 1995). Thymol was added separately in a Petri dish to the recipients containing saturated salt solutions with a relative humidity higher than 75% in order to avoid microbial growth, especially mould (Vega et al, 2007).…”

“…Similar results of monolayer moisture have been observed in raisins, figs, plums, potatoes, onions and tomatoes with 0.212-0.087 g water g -1 dm for 30-60 ºC (Kiranoudis et al, 1993); in red and green peppers with 0.113-0.038 g water g -1 dm for 30-60 ºC (Kaymak-Ertekin and Sultanoglu, 2001); in grapes, apples, potatoes and apricots with 0.220-0.095 g water g -1 dm for 30-60 ºC (Kaymak-Ertekin and Gedik, 2004). Monolayer moisture (Xm) is an important parameter since it has a physicochemical behavior that represents the first layer of water molecules, which can thermodynamically interact with other food compounds (Lim et al, 1995;Yu et al, 1999).…”

Contribución al estudio de la aplicación de ultrasonidos de potencia en el secado convectivo de alimentos

“…1.1.6) fue desarrollado a través de una expansión en series matemáticas de curvas sigmoidales. Al igual que el modelo de GAB, presenta la humedad como variable dependiente de la temperatura y de la actividad de agua (Lim et al, 1995;Sun, 1999).…”