Moisture Sorption Properties of Food Products and Packaging Materials Studied by DVS (Application note 102)

by Dan Burnett, Armando R. Garcia, Majid Naderi, and Manaswini Acharya, Surface Measurement Systems Ltd.

Introduction

The moisture sorption properties of food products are recognised as critical factors in determining their storage, stability, processing and application performance

[1-2]. Moisture sorption properties for many food products and packaging materials have traditionally been evaluated by storing samples over saturated salt solutions of established relative humidities and then regularly weighing until equilibrium is reached [3]. However, there are a number of disadvantages with these methods, including: (i) the prolonged period of time taken for the samples to reach equilibrium using a static method, often many days and commonly many weeks; (ii) inherent inaccuracies as the samples have to be removed from the storage container to be weighed which can cause weight loss or gain; (iii) static methods necessitate the use of large samples sizes (typically 10-100g); and (iv) the highly labour intensive nature of static methods.

For the above reasons, a rapid, highly-sensitive and automated approach is desired. Hence, the invention of the Dynamic Vapour Sorption (DVS) instrument by Surface Measurement Systems in the early 1990’s. Today, the DVS is widely used across numerous industries for investigating the vapour sorption properties of solids, fibres, gels, particulates, and composite materials. This application note summarises several DVS applications related to foods, food ingredients, and food packaging.

Graphs

App 102 Isotherm

Moisture sorption kinetic (a.) and isotherm (b.) plots for starch at 25 °C.

App 102 Humidity

Humidity-induced phase transitions for spray-dried lactose measure via DVS.

Method

The instrument measures the uptake and loss of vapour gravimetrically using the SMS UltraBalance with a mass resolution of ±0.1 μg. The vapour partial pressure around the sample is generated by mixing saturated and dry carrier gas streams using electronic mass flow controllers.

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