Determination of Display Shelf Life of Sandwich Components

There is considerable demand for process design data on all aspects of food chilling, especially for unwrapped products. This is a result of strict product temperature legislation together with economic requirements to maximise throughput, minimise weight loss and operate refrigeration systems in the most efficient manner. Recent years have seen an increase in customer demand for fresh convenience food, which has caused a major increase in the volume of sales of unwrapped products. Surface drying has been identified as the main reason for commercial loss from unwrapped chilled food in display cabinets. Surface drying increases weight loss and leads to colour changes that are undesirable. This paper reports on work aimed at determining the mass transfer coefficients for some of the most common fillings used in unwrapped sandwiches under the environmental boundary conditions that exist in a display cabinet, and to evaluate their display shelf life and dehydration rate. It was observed that changes in relative humidity along with the air velocity have a substantial effect on drying rate. The measured drying rates were used to derive the average mass transfer coefficients, which are presented in the form of empirical equations that can be used in the selection of appropriate display cabinet environmental conditions to prolong shelf life and reduce wastage.