Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2005
Publication Date: 1/24/2006
Citation: Plotto, A., Bai, J., Narciso, J.A., Brecht, J., Baldwin, E.A. 2006. Ethanol vapor prior to processing extends fresh-cut mango storage by decreasomg spoilage, but does not always delay ripening. Postharvest Biology and Technology. 39:134-145. Interpretive Summary: Fresh-cut fruit are healthy and convenient to eat, but have a short shelf life after the fruit tissue has been cut. In this work, ethyl alcohol (grain alcohol or ethanol) vapors, known to delay fruit ripening, were applied to whole mangoes prior to cutting, and conditions of treatment were optimized. Ethanol effect on slice shelf life varied and depended on factors such as maturity stage, and whether or not fruit had been prior subjected to a quarantine heat treatment, commonly done on imported fruit. When the dose applied was too high, the treatment imparted a residual off flavor to the fruit. At lower doses, the treatment was not as effective. Whole fruit treatment with ethanol suppressed microbial growth on the slices of treated mangoes at all doses tested. Therefore, ethanol treatment of whole mangoes could be used as a safe way to block microbial spoilage of the sliced fruit.
Technical Abstract: This study was undertaken to optimize ethanol vapor application as a ripening inhibitor on whole mangoes to extend fresh-cut mango shelf-life. One half of the freshly harvested mangoes were first subjected to hot water bath (+HWB) at 46 °C for 60 or 90 min. to simulate quarantine heat treatments, and the other half remained without hot water bath (-HWB). Fruit of each batch were then exposed to ethanol vapors 0 hrs (E0), 10 hrs (E10), or 20 hrs (E20)) 4 or 7 days after the HWB treatment (maturity 1-M1 and 2-M2), respectively). Fruit were then cut into slices, packed in plastic clamshells, and stored at 7 °C for 15 days. Measurements for firmness, color with the CIE L*a*b* system, total soluble solids, titratable acidity (TA), pH, respiration rate, ethylene, and internal volatiles were done. The HWB synchronized fruit ripening, and only slices from fruit pre-treated with +HWB at M1 responded to ethanol treatments by maintaining higher firmness, hue angle, and titratable acidity (TA) in storage. Fruit pre-treated with +HWB, M2, and E10 or E20 had higher hue angle than E0, but no other maturity parameters were different. Internal ethanol and acetaldehyde were very high in slices from fruit exposed to +HWB, M1 and M2, E20. In the +HWB group, only slices from fruit that had been exposed to E20 at M2 had high internal ethanol and acetaldehyde. A sensory panel could perceive higher firmness and acidity in slices from fruit treated with ethanol. However, E20 induced off flavor, and these fruit were least preferred. The experiment was repeated with purchased mangoes, which were therefore prior subjected to a quarantine heat treatment. A second heat (38 °C, 98% RH) treatment was added. Ethanol vapors did not result in delayed ripening in store-purchased mangoes. However, microbial growth was maintained to a minimum. The second heat treatment did not improve cut mango shelf life, and further, increased microbial growth. It is concluded that ethanol vapor on whole mangoes prior to processing for fresh-cut is not a very practical approach to delay ripening because of the variable effects of harvest maturity and not water treatment, and because of the development of off flavor when exposed to more than 20 hrs. Nevertheless, ethanol at lower doses (10 hrs) could be used as a safe microbial control in a fresh cut production sanitation system.