Shelf life extension of sliced wheat bread using either an ethanol emitter or an ethanol emitter combined with an oxygen absorber as alternatives to chemical preservatives

In the present study, the effect of active packaging [ethanol emitter (EE) or ethanol emitter combined with an oxygen absorber (EE + OA)] on shelf life extension of sliced wheat bread stored at 20 °C was investigated. Bread containing commercial preservatives (WP) and no preservatives (WOP) were taken as controls. Microbiological, physicochemical and sensory changes occurring in the product as a function of treatment and storage time were monitored for 30 days. Counts for yeasts and molds were 5.1, 3.8, 2.0 and 2.0 log cfu/g and for Bacillus cereus 4.7, 2.5, 2.3 and 2.0 log cfu/g for WOP, WP, EE and EE + OA treatments respectively after 30 days of storage. Initial pH 6.3 and 6.4, for WP and WOP samples remained fairly constant irrespective of specific treatment. Aroma quality deterioration during storage was due to the loss of volatile compounds and the formation of “off-flavors” through lipid oxidation. Neither the EE nor the EE + OA had an adverse effect on initial odor, taste and texture of bread. Based on sensory (texture) and microbiological data, shelf life was ca. 4 days for samples WOP; 6 days for samples WP; 24 days for samples containing the EE and at least 30 days for samples containing the EE + OA.