Title: COMBINING CALCIUM CHLORIDE WITH SUCROSE FOR OSMOTIC DEHYDRATION OF APPLE SLICES AND ITS EFFECT ON THE INTERACTION OF PENICILLIUM EXPANSUM, COLLETOTRICHUM ACUTATUM, AND BOTRYTIS CINEREA, WITH LISTERIA MONOCYTOGENES
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 14, 2001
Publication Date: N/A
Interpretive Summary: There has been a net increase in fresh fruit consumption during the last decade in the United States due to consumer interest in a healthy and nutritious diet. Processed produce with the qualities (flavor, texture, visual aspects) of fresh produce are gaining in popularity. Several techniques have been developed to partially remove water from fruits and vegetables in order to increase shelf-life of produce, reduce aroma losses in dried and semi-dried foodstuffs, and retain maximum quality in the final product. The advantage of dried over fresh food is that it can be stored and transported at a relatively low cost. Osmotic dehydration using concentrated sucrose solutions has been used in osmo- dehydration of raw apple material, but fungal decay can be a problem. There has also been shown to be a metabiotic association between fungi and foodborne human pathogens in that fungal decay of fruit can increase pH and increase the growth of foodborne human pathogens. We found that the osmotic dehydration of apple slices in sucrose solutions containing calcium chloride limited fungal decay and therefore did not promote the growth of foodborne human pathogens. The apple processing industry may find the combination of calcium chloride and sucrose to be an effective method of reducing losses in the osmo-dehydrated product as well as reducing the risk of human pathogen contamination.
The effect of calcium chloride combined with sucrose on the microbiological population of lightly processed apple slices was tested. The interaction of Penicillium expansum Link, Colletotrichum acutatum, and Botrytis cinerea Pers.:Fr. with Listeria monocytogenes on osmotically dehydrated apple slices was also studied. Mineral analysis of the slices showed that the calcium content of both the peel and flesh tissues increased by four- and eleven-fold, respectively, when processed in 2% calcium chloride. These slices also exhibited less decay by P. expansum, C. acutatum and B. cinerea. Inoculation of slices with P. expansum resulted in a decrease in the pH of the flesh tissue at the infection site, while the pH of slices infected with C. acutatum and B. cinerea increased and remained stable, respectively. Total mold population increased in wounds inoculated with P. expansum or C. acutatum. The presence of L. monocytogenes in the wounds did not significantly affect mold growth. The association of P. expansum and L. monocytogenes on apple slices resulted in a decrease in the bacterial population, while L. monocytogenes survived when slices were inoculated with C. acutatum. When associated with B. cinerea, there was a four- fold decrease in the L. monocytogenes population when slices were treated with 2% calcium chloride. Total aerobic population was not significantly affected by the type of microorganism added to the wounds or by the osmotic treatment. These data showed that osmotic dehydration using 2% calcium chloride combined with 20% sucrose limited decay of apple slices and did not promote bacterial or total aerobic population growth.