GAB Isotherm Calculations for Microfibril Barrier Sorption Qualification
GAB isotherm parameters determine microfibril moisture sorption capacity and establish precise water activity thresholds for barrier packaging compliance.
Water Activity Aw
Thermodynamic Measurement
Comparison of the vapor pressure of water in a material to the vapor pressure of pure water at the same temperature indicates the energy state of the moisture. Accurate water activity aw determines the susceptibility of a product to microbial spoilage and chemical degradation. It is a unitless value ranging from zero to one.
This measurement is more useful for predicting shelf life than total moisture content because it reflects the availability of water for reactions.
Instrumental Analysis
Chilled mirror sensors or electrolytic hygrometers measure the equilibrium relative humidity in a closed chamber above the sample. Measuring water activity aw allows for the mapping of moisture migration between different components of a multi domain food product.
Safety Standard
Safety standards define specific thresholds below which bacteria like staphylococcus aureus cannot grow. Maintaining water activity aw below zero point six prevents the growth of all known microbes including yeasts and molds. This parameter guides the selection of packaging barriers to ensure that the internal environment remains stable over time.
If the value increases during storage, the product may undergo texture changes such as caking or softening. The measurement is sensitive to temperature fluctuations and must be performed under controlled conditions.