Enzyme-peeling of Valencia oranges for fresh-cut slices

Simona Pinnavaia, Elizabeth A. Baldwin, Anne Plotto, Jan Narciso, Emilio Senesi

Abstract


In spite of the booming market for fresh cut fruit, fresh cut citrus products have not been successfully commercialized due to technical difficulties in peeling the fruit and concerns over microbial contamination and juice leakage. The USDA and the Florida Department of Citrus have developed processes using enzyme infiltration under vacuum as well as water infusion to facilitate citrus peeling. However, the enzymes (cellulase and/or pectinase) continue their lytic action on the slices after the peeling process, reportedly degrading the slices during storage, and likely contributing to objectionable softening and juice leakage. There is also a perceived fear of microbial contamination in the process of enzyme infiltration or water infusion. The objective of the present study was to investigate low level enzyme concentrations and use of an acid solution (0.1 N HCl) rinse and cold conditioning (2C for 24 hours) to slow down enzymatic activity after peeling of 'Valencia' oranges. In addition, the infiltration system was used to compare two commercial enzymes and water infusion for efficacy of peeling and effect on microbial contamination. Quality factors including juice leakage, firmness, pH, titratable acidity, soluble solids, and surface microbial counts were evaluated over three different harvests. Water infusion resulted in less attractive slices and a tougher texture compared to enzymetreated fruit slices. Microbial counts were highest in water-infused fruit compared to those treated with enzymes or manually peeled, which in both cases were very low. Of the two enzymes tested, Ultrazym resulted in firmer slices and generally less juice leakage, although leakage was minimal for both enzymes within a two-week storage period at the enzyme concentrations used. Juice leakage, however, was not affected by the acid treatment or temperature conditioning.

Keywords


Citrus sinensis; fresh cut fruit; enzyme peeling

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283