Food Microbiology

Statement of the problem: Wheat grains are naturally contaminated with bacteria, yeasts and moulds while in the field and during storage, which represent the major cause of grain spoilage. In particular, fungi produce losses related to heating, biochemical changes, production of mycotoxins, decrease of germination capacity, and loss of dry matter. Growth of microorganisms can be prevented by drying of grains to reduce the moisture content and using of chemical preservatives. However, drying methods are expensive and chemical preservatives affect the germination capacity of wheat grains. Pulsed light (PL) is an emerging non-thermal technology able to reduce the microbial population on the surface of food and food contact materials.

 

Methodology: Wheat grains have been exposed to PL at different fluencies (2.23–30.05 J/cm2) and different number of pulses (10–60) in an experimental set-up able to rotate the wheat grains and expose the entire surface to PL. Survival populations of fungi and bacteria have been counted after each PL treatment and compared with fungi and bacteria load of control sample. Germination tests have been performed for PL treated samples and control. Subsequently, wheat grains used to determine the germination capacity have been dried, ground and subjected to analyse antioxidant capacity and enzymatic activity.

 

Findings: PL exposure of wheat grains resulted in reductions of up to 2.3 log CFU/g and 1.2 log CFU/g for fungi and bacteria respectively. Germination capacity of wheat grains has not been affected by PL treatment, but germination rate has been improved due to reduction of microbial load and enhanced of enzymatic activity.

 

Conclusion & Significance: Results confirm the positive effect of PL treatment on wheat grain decontamination and enhancement of germination rate which extend the shelf life of grains and use in food industry.