Whey protein films have antibrowning effect on produce.

Edible films and coatings may extend the shelf life of fresh-cut produce by providing a semipermeable barrier to gases and water vapor. This barrier would reduce respiration, enzymatic browning and the loss of water from the product. For the most part, the development of edible films and coatings has focused upon creating barriers containing proteins, polysaccharides and lipids.

Coating performance depends, among other factors, on composition. So it is important to study the composition of a coating before incorporating additives, such as antioxidants or antimicrobials, into it. This would facilitate the ability to economically optimize a coating's performance on fresh-cut produce.

The objective of Spanish scientists was to study the effectiveness of polysaccharide-lipid and proteinlipid-based edible composite coatings, without the incorporation of antibrowning agents, in postponing the enzymatic browning of freshly cut apples. It appears that whey proteins exert an antibrowning effect and can be beneficial in reducing browning.

Edible composite coatings were prepared from whey protein isolate (WPI), whey protein concentrate (WPC) or hydroxypropylmethyl cellulose (HPMC) as the hydrophilic phase, and from beeswax or carnauba wax as the hydrophobic phase. The researchers cut golden apples, immersed them in citric acid and sanitized them in sodium hypochlorite solution. Apple pieces were dip-coated with the emulsion coatings and stored for one day at 20 C or for seven days at 5 C in open and sealed trays. Weight loss and color (CIE L*, a*, b* and browning index) were measured during the products' storage.

The results show that apples coated with whey protein-based coatings had higher L*, and presented lower b*, a* and browning index values than HPMC-based coated and uncoated apples. Coatings containing beeswax were more effective in inhibiting enzymatic browning than coatings containing carnauba wax. Applying the coatings did not reduce weight loss in freshly cut apples, which indicates that these coatings were not effective as moisture barriers under these storage conditions.

Further information. M. B. Perez-Gago, Postharvest Department, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Spain; phone: [phone]; fax: [phone]; URL: www.ivia.es.