Methods for measuring water activity (a_w) of foods and its applications to moisture sorption isotherm studies

Abstract

Moisture sorption isotherm is commonly determined by saturated salt slurry method, which has defects of long time cost, cumbersome labor, and microbial deterioration of samples. Thus, a novel method, a measurement (AWM) method, has been developed to overcome these drawbacks. Fundamentals and applications of this fast method have been introduced with respects to its typical operational steps, a variety of equipment set-ups and applied samples. The resultant rapidness and reliability have been evaluated by comparing with conventional methods. This review also discussed factors impairing measurement precision and accuracy, including inappropriate choice of predryingwetting techniques and unachieved moisture uniformity in samples due to inadequate time. This analysis and corresponding suggestions can facilitate improved AWM method with more satisfying accuracy and time cost.

Dried Urine Swabs as a Tool for Monitoring Metabolite Excretion

“…Hypothetically, certain bacterial or oxidative degradation could occur within this period but bench top stability tests (samples were stored at 5 • C for 15-20 h in the LC sample manager) performed within the method validation [19] did not show any compound degradation in liquid samples. However, loss may happen while water activity is declining below critical values when metabolites would be in soluble form to permeate the cell wall in case of microbial contamination [31]. On the other hand, microbial degradation would be highly variable between samples and would not seem plausible with the fair reproducibility for the analytes observed here.…”

Effect of spray-drying conditions on moisture content and particle size of coffee extract in a prototype dryer

“…In addition, the sorption isotherms were determined at 25°C using an Aqualab automatic vapor sorption analyzer (VSA1033, DECAGON, USA). This method has been reported and used recently Schmidt and Lee, 2012;Zhang et al, 2017). The results were adjusted with BET and GAB models, as shown in eqs.…”

Isotermas dinámicas de sorción de humedad y propiedades termodinámicas de café soluble

“…Las isotermas de sorción de humedad son importantes para predecir la estabilidad durante el almacenamiento y seleccionar el material de embalaje apropiado de los alimentos (Aviara, 2020). Generalmente estas curvas se han realizado empleado el método estático gravimétrico en el que se utilizan sales en solución como NaCl, KCl, LiCl, entre otras, las cuales crean una humedad relativa establecida al saturarse (Zhang et al, 2017). El método de la isoterma dinámica de punto de rocío (DDI) es una técnica recientemente desarrollada junto con la adsorción dinámica de vapor (DVS) para medir las propiedades de sorción de agua de materiales alimenticios.…”