Rapid Sensor Measures Mold in Food Products

Problem

Mold (fungi) contamination is responsible for up to 10% losses worldwide in agricultural produce. Many industries regularly monitor mold levels in food products. Despite years of research, until now there has been no method for measurements of mold in food products that is fast, simple and inexpensive, and will detect a wide variety of mold species.

In the California tomato industry, mold contamination is a continual issue, and has been regulated by the Federal Government since the turn of the century. Mold levels are graded by visual inspection at grading stations, and also scored by counting mold fragments under the microscope in canneries (Figure 1).

Figure 1. Present mold grading practice in the tomato industry

Objectives:

1. Develop a rapid technique that will quantify mold contamination in field tomatoes.
   
2. Test on a wide variety of mold species.
   
3. Automate technique so that it can be performed at grading stations and in canneries.
   

Sensor Technology:

To detect fungi, we use a molecular probe that binds only to fungal cell walls. Attached to this probe is a fluorescent molecule that emits green light when illuminated with blue light (Figures 2 & 3). We can measure the amount of fluorescence in a sample, and therefore the amount of mold using a commercially available fluorometer (Figure 4).

Figure 2. Microscopic images showing fluorescent probe bound to mold. At left, normal view. At right, fluorescent view (400x)



Figure 3. UC Davis detection method



Figure 4. Laboratory evaluation of mold readings in tomato juice

Potential Applications

• rapid analysis of mold in grapes, fruit juices.
• monitoring airborne spore levels in citrus packinghouses.

• monitoring fungal infections in human patients.
• monitoring airborne fungal allergens in U.S. cities.
• detecting airborne mold levels in hospitals and biotech clean rooms.

Funding provided by the Processing Tomato Advisory Board

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last modified 12/17/2003