ENHANCEMENT OF THE QUALITY AND MICROBIAL STABILITY OF FRESH FRUITS AND VEGETABLES WITH EDIBLE COATINGS AND OTHER SURFACE TREATMENTS
Location: Quality Improvement in Citrus and Subtropical Products Res
Title: Flavor and other quality factors of enzyme-peeled oranges treated with citric acid
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 6, 2007
Publication Date: December 10, 2007
Citation: Pinnavaia, S., Plotto, A., Narciso, J.A., Baldwin, E.A., Senesi, E. 2007. Flavor and other quality factors of enzyme-peeled oranges treated with citric acid. HortScience. 42(7):1644-1650.
Interpretive Summary: Orange slices "ready-to-eat" are pre-peeled by scoring the whole fruit, then placing in a water or enzyme solution under vacuum to split the peel from the fruit. Peeled oranges are then cut into segments. The vacuum infusion of water or enzyme may present a risk of microbial contamination, and also, enzymes can modify the quality of cut slices. Citric acid was used to prevent any potential microbial contamination. Oranges that were vacuum infused in a citric acid solution had less contamination. Also, enzyme-peeled oranges that were later dipped in citric acid had lower microbial counts. Flavor was not changed by citric acid. However, enzyme infusion resulted in softer slices for 'Valencia' oranges, which were preferred to water-infused slices by a 20-member taste panel. Enzyme infusion also improved appearance of 'Hamlin' slices, according to the panel. In addition, enzyme infusion increased the amount of methyl butanoate and methanol volatiles, but taste panel did not perceive any changes in flavor from that increase.
Oranges can be satisfactorily processed for fresh slices using a process of enzyme infiltration under vacuum. Scored 'Valencia' and 'Hamlin' oranges were placed under 90 kPa vacuum in a 0 ppm (water-infused) or 1000 ppm enzyme solution (Ultrazym) at 30 °C for 2 min, followed by 30 min incubation in air. After peeling, fruit were washed, cut, and slices were then dipped in water or 1% citric acid (CA) for 2 min. Drained slices were then placed in 454 mL deli containers and stored at 5 °C for up to 21 d. One additional treatment involved vacuum infiltrating scored oranges with 1% CA, without further dipping the cut slices. All 'Valencia' slices had <1.0 log10 (cfu•g-1) after 7 d storage, and slices from CA-infused fruit had <1.0 log10 (cfu•g-1) after 21 d storage. For 'Hamlin', CA dips controlled bacterial growth on slices from water-infused oranges, except at 14 days. Enzyme-infused oranges resulted in slices with lower counts for both cultivars. CA –treated sliced (post enzyme treatment or by infusion) oranges had higher titratable acidity initially ('Hamlin') and after 14 days ('Valencia'). When presented to a taste panel, 'Valencia' slices from enzyme-peeled fruit were preferred for texture after 2 and 8 d in storage. In contrast, slices from fruit infused with water or citric acid were least preferred, were firmer, and had thicker segment membranes. Appearance of enzyme-treated fruit was preferred for 'Hamlin' oranges. Enzyme treatments increased levels of methanol and methyl butanoate in 'Hamlin' slices, but overall sensory flavor data were not affected.