Maintain quality of refrigerated fresh-cut apples with edible coating.

Consumer demand for ready-to-eat fresh-cut fruits and vegetables has been drastically increasing. Maintaining the quality of this type of produce continues to challenge processors. One possible solution: edible coatings that extensively prolong the shelf life and increase marketability of fresh-cut apples.

With this in mind, scientists at Louisiana State University determined the effects of a whey protein coating on the physical and microbial qualities of fresh-cut Fuji apples during 13 days of refrigerated storage. Their research suggests that a 10% whey protein concentrate (WPC) coating can maintain the quality of fresh-cut Fuji apples during this period of refrigerated storage.

In this study, whole apples were surface sanitized, uniformly cut into cubes, and coated with 0% water as the control, 5% or 10% of WPC, whey protein isolate (WPI) or partially hydrolyzed whey protein concentrate (PHWPC). Each coating solution, except the control, contained 30% glycerol by weight of whey protein. All of the samples were stored in sealed plastic containers at 2 C and tested for color, firmness, moisture loss, total plate count and E. coli and coliform counts after 1, 4, 7, 10 and 13 days of storage.

The researchers used two separate batches of apples. They conducted triplicate quality measurements for each batch. Data were statistically analyzed. The 10% WPC coating was the most effective in minimizing weight loss. A 1.8% moisture loss was observed after 13 days of storage.

There were no changes in the color lightness of samples coated with WPC or WPI. But the scientists observed significantly decreased lightness for the control after four days of storage. The 5% and 10% WPC coated apples turned brown, respectively, after 7 and 10 days of storage. The firmness of the coated samples did not change after 13 days of storage, compared to the firmness of the control that was undesirably soft.

The 10% WPC treatments were better than the 5% treatments in maintaining firmness. The total plate count ranged from 0.3 colony-forming units (CFU) per g to 5.0 CFUs per g after 10 days of storage. No E. coli was detected during the 13 days of refrigerated storage. Further information. Marlene Janes, Department of Food Science, Louisiana State University, Agricultural Center, 111 Food Science Building, Baton Rouge, LA 70803; phone: [phone]; fax: [phone]; URL: www.agctr.lsu.edu/foodscience.