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Joseph L. Smilanick

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David Obenland, Dennis Margosan, Joseph L. Smilanick, and Bruce Mackey

Navel oranges (Citrus sinensis) were sorted into four groups under ultraviolet illumination in commercial packinghouse black light rooms based upon the amount of fluorescence visible on each fruit to determine if fluorescence was predictive of peel quality. The groups corresponded to fruit with 1) little or no fluorescence (group 0), 2) low fluorescence (group 1), 3) moderate fluorescence (group 2), and 4) large fluorescent areas (group 3) that were indicative of developing decay lesions. Identification and elimination of group 3 fruit in black light rooms is a common practice now, but the other groups pass through these rooms. Six tests were conducted over a 2-year period during different times in the mid to late navel orange season. Fruit were visually evaluated for peel quality within 24 hours of their initial segregation into fluorescence groups and again following 3 weeks of storage at 15 °C. Peel quality assessment was based upon commercial grading practices, and the fruit were placed into fancy, choice, juice, or decay classes. Fruit with low to no peel fluorescence (groups 0 and 1) had numerous fancy-grade fruit and few juice- and decay-grade fruit in comparison with the other two groups. In contrast, fruit with moderate fluorescence (group 2) were of poor peel quality. In the initial evaluation, this group had 28% fewer fancy fruit and 19% more juice fruit than did group 0. During storage, group 2 fruit declined markedly in quality and numerous fruit of group 2 in the choice and juice classes decayed; the percentage of decayed fruit increased from 1% initially to 29% after 3 weeks of storage. Navel oranges in group 3, with numerous and obvious fluorescent decay lesions, mainly consisted of either juice grade or decayed fruit; 70% of group 3 decayed after 3 weeks. In addition to removing fluorescing fruit that have obvious indications of decay (group 3), it would be advantageous to remove or otherwise recognize that fruit with moderate levels of fluorescence (group 2) are also of lower quality and that they should not be selected for long storage or distant transport. Their identification may be most practical with an automated system using machine vision and ultraviolet illumination.

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Gilbert F. Simmons, Roger Rij, Joseph L. Smilanick, and Shama John

Refrigerated fresh-cut fruit and vegetables are the most rapidly expanding area in produce sales. Shelf life for minimally processed produce depends on natural product senescence or spoilage organism decay. Shelf life limits, near-aseptic cutting facilities, refrigerated transportation, and refrigerated storage make it possible to ship precut cantaloupe coast to coast on a year-round basis. Thorough cantaloupe surface disinfection reduces potential spoilage organisms and harmful pathogens. We compared using vapor hydrogen peroxide and sulfur dioxide to the current practice of hypochlorite (HOCL) washing to reduce cantaloupe microbial load. After treatment, cantaloupe were stored in unsealed polyethylene bags at 2.2°C for 4 weeks. The HOCL treated fruit were scrubbed and soaked for 5 minutes in a commercial HOCL solution. After 4 weeks, the HOCL washed fruit had reduced visible molds compared to controls. Cantaloupes fumigated for 60 minutes with 5000 or 10,000 ppm sulfur dioxide developed sunken lesions but no significant decay after 4 weeks storage. Cantaloupes, treated 60 minutes with 3 mg·L–1 volume vapor hydrogen peroxide, did not show injury or significant decay after 4 weeks storage. Sulfur dioxide and vapor hydrogen peroxide show promise as alternatives to HOCL.

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Gilbert F. Simmons, Joseph L. Smilanick, Nuria Denis-Arrue, Dennis A Margosan, and Shama John

A new vapor phase hydrogen peroxide (VPHP) technology that uses relatively dry hydrogen peroxide pulses is a promising method for the disinfection of surface-borne bacteria, yeasts, and molds on walnut nutmeats. The number of colony forming units per gram (cfu/g) on untreated nutmeats was compared to those VPHP treated. Three culture media; dichloran rose bengal chloramphenicol agar base (DRBC, Oxoid), aerobic plate count agar (APC, Oxoid), and potato dextrose agar (PDA, Sigma), were utilized to evaluate cfu/g. Similar numbers of cfu/g of product were observed on APC and PDA. The more selective DRBC had lower cfu/g. Microorganisms washed from untreated walnut nutmeats purchased at retail outlets ranged between 17,000-29,000 cfu/g depending upon the culture medium used. The number of cfu/lg on nutmeats after VPHP treatments was reduced to 500-1400, a 95% reduction. VPHP may offer an alternative to propylene oxide fumigation. The moisture content of nutmeats was not significantly altered by VPHP. The Food and Drug Administration lists hydrogen peroxide as a “generally recognized as safe substance” (GRAS). Hydrogen peroxide is already produced in a food grade for aseptic packaging.

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Joseph L. Smilanick, David Sorenson, Monir Mansour, Jonah Aieyabei, and Pilar Plaza

A brief (15 or 30 seconds) high-volume, low-pressure, hot-water drench at 68, 120, 130, 140, or 145 °F (20.0, 48.9, 54.4, 60.0, or 62.8 °C) was applied over rotating brushes to `Eureka' lemons (Citrus limon) and `Valencia' oranges (Citrus sinensis). The impact of this treatment on populations of surface microbes, injury to the fruit, the incidence of green mold (Penicillium digitatum)or sour rot (Geotrichum citri-aurantii), when inoculated into wounds one day prior to treatment, and temperatures required to kill the spores of these fungi and P. italicum suspended in hot water were determined. Fruit microbial populations were determined immediately after treatment. Decay and injuries were assessed after storage for 3 weeks at 55 °F (12.8 °C). The efficacy of the hot water treatments was compared to immersion of fruit in 3% wt/vol sodium carbonate at 95 °F (35.0 °C) for 30 seconds, a common commercial practice in California. Initial yeast and mold populations, initially log10 6.0 per fruit, were reduced to log10 3.3 on lemons and log10 4.2 on oranges by a 15-second treatment at 145 °F. Green mold control improved with increasing temperature and treatment duration. Green mold incidence was reduced from 97.9% and 98.0% on untreated lemons and oranges, respectively, to 14.5% and 9.4% by 30 seconds treatment with 145 °F water. However, immersion of lemons or oranges in 3% wt/vol sodium carbonate was superior and reduced green mold to 8.0% and 8.9%, respectively. Sour rot incidence on lemons averaged 84.3% after all water treatments, and was not significantly reduced, although arthrospores of G. citriaurantii died at lower water temperatures than spores of P. digitatum and P. italicum in in vitro tests. Sodium carbonate treatment for 30 seconds at 95 °F reduced sour rot to 36.7%. None of the treatments caused visible injuries to the fruit.

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Charles F. Forney, Roger E. Rij, Ricardo Denis-Arrue, and Joseph L. Smilanick

The potential use of vapor phase hydrogen peroxide (VPHP) to prevent decay caused by Botrytis cinerea Pers. ex Fr. in table grapes (Vitis vinifera L.) was investigated. `Thompson Seedless' and `Red Globe' grapes, inoculated with Botrytis cinerea spores, were placed in polyethylene bags and flushed for 10 minutes with VPHP generated from a 30% to 35% solution of liquid hydrogen peroxide at 40C. Immediately after treatment, bags were sealed and held at 10C. Vapor phase hydrogen peroxide significantly reduced the number of terminable Botrytis spores on grapes. The number of terminable spores on `Thompson Seedless' and `Red Globe' grapes had been reduced 81% and 62%, respectively, 24 hours following treatment. The incidence of decay on inoculated `Thompson Seedless' and `Red Globe' grapes was reduced 33% and 16%, respectively, after 8 days of storage at 10C compared with control fruit. Vapor phase hydrogen peroxide reduced the decay of noninoculated `Thompson Seedless' and `Red Globe' grapes 73% and 28%, respectively, after 12 days of storage at 10C. Treatment with VPHP did not affect grape color or soluble solids content.

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Gilbert F. Simmons, Joseph L. Smilanick, Shama John, and Dennis A. Margosan

Moisture is raised in dehydrated prunes to improve palatability before packaging and potassium sorbate is added to inhibit microbial growth. Vapor phase hydrogen peroxide (VPHP) technology uses hydrogen peroxide pulses to disinfect dried prunes. Dried prunes were obtained from dehydrators. The number of colony-forming units per 10 prunes (cfu/p) was compared between untreated and VPHP treated. Three culture media—dichloran rose bengal chloramphenicol agar base (DRBC, Oxoid), aerobic plate count agar (PCA), and potato dextrose agar (PDA)—were used to evaluate cfu/p. Similar mean microbe populations were observed on DRBC (67) and PDA (70); PCA had higher cfu/p (99). Microbes washed from untreated prunes obtained from dehydrators were 58 to 112 cfu/p, depending on the culture medium used. The number of cfu/p assessed on all media on VPHP-treated prunes was near 0 after 100 min exposure. Unlike potassium sorbate, hydrogen peroxide is a microbiocide rather than a microbiostat.