James P. Mattheis

Inhibition of ethylene action by 1-methylcyclopropene prolongs storage life of apricots.

Abstract ‘Perfection’ apricot fruit (Prunus armeniaca L.) were treated with 1 μl l−1 1-methylcyclopropene (MCP) for 4 h at 20°C then stored at 0 or 20°C. The onset of ethylene production was delayed and respiration rate was reduced following MCP treatment. MCP treatment resulted in less firmness and titratable acidity loss during storage at both temperatures and delayed production of volatile alcohols and esters during ripening at 20°C. MCP treated fruit also exhibited less color change and were greener than controls. The effects of MCP were less pronounced following treatment of fruit at a more advanced stage of development.

Preharvest factors influencing flavor of fresh fruit and vegetables

Abstract Perception of fruit and vegetable flavor is a composite of sensory responses in the nose and mouth to aroma and taste. A diverse array of fruit and vegetable constituents including acids, sugars, volatiles and many other compounds individually elicit sensory responses that are recognized in total as flavor. Accumulation of these compounds during development as well as dynamic changes during ripening and/or senescence are determined in large part by the genetics of each species as well as developmental stage at harvest. However, other factors that influence development prior to harvest subsequently impact flavor. For horticultural crops, environment, cultural practices, agrichemicals and nutrition are some of the factors impacting flavor through effects on plant development.

Formulation of zein coatings for apples (Malus domestica Borkh)

High gloss coatings are used to improve apple fruit (Malus domestica , Borkh) appearance and sales. The industry standard has been shellac-based formulations, which have problems with whitening, low gas permeability, and association with non-food uses. Zein, a natural corn protein, was used to formulate alternative, shiny coatings by dissolving zein in aqueous alcohol with propylene glycol (PG). Gloss levels on ‘Gala’ apple surfaces varied due to zein and PG content in coating formulations from that of controls to levels observed for shellac-coated fruit. At least 4% (by weight) PG was necessary for adequate gloss. However, increasing levels of both compounds resulted in increased gloss. Whitening, which occurred on the coated fruit surface upon wetting, was reduced by decreasing zein content to less than 11%. Permeability to CO2 ,O 2, and water vapor was strongly dependent on the zein content in the coating. Internal CO2 and O2 in zein-coated ‘Gala’ fruit ranged 4 � /11 and 19 � /6 kPa, respectively, by increasing zein content in the coatings. An optimum formulation with 10% zein and 10% PG was developed, applied to ‘Gala’ apple, and was found to maintain overall fruit quality comparable to a commercial shellac coating. # 2002 Published by Elsevier Science B.V.

Ester biosynthesis in “Rome” apples subjected to low-oxygen atmospheres

Abstract The relationship between acetate ester-forming activity of acetyl CoA alcohol transferase (ACAT), non-ethylene volatile emission, and flesh volatile content of “Rome” apples ( Malus domestica Borkh.) after removal from 9 months storage in low-oxygen environments was investigated. Apple samples held at 0–1°C were removed from refrigerated air (RA) or controlled-atmosphere (CA) storage at 1.0 or 0.5% v/v O 2 /1% CO 2 and placed in ambient laboratory conditions. Every three days fruit flesh and headspace were analyzed for volatile compounds using capillary gas chromatography. Acetate ester forming activity was assayed spectrophotometrically on partially-purified extracts of cortical tissue. Patterns of acetate ester formation depended upon storage environment and alcohol moiety precursor. Ethyl acetate content was always higher in the headspace and flesh of RA fruit, regardless of time after storage. Propyl acetate concentrations in CA stored apple flesh were higher until post-storage day 12 when they decreased. Headspace propyl acetate levels were higher in RA controls until days 9–15 when more emanated from CA fruit. Butyl acetate concentrations were lower in flesh and headspace of CA fruit until day 15, when RA fruit headspace levels decreased. Headspace and flesh concentrations of 2-methyl-1-butyl acetate were higher in CA apples. Acetate ester-forming activity was detectable at day 0 in 1.0% oxygen-stored fruits, but not in 0.5% oxygen-stored fruits. By post-storage day 9, ACAT activity in CA apples reached maximal levels, only to decrease by day 15. RA-stored apples had more ACAT activity at day 0, but did not substantially increase in activity like the 0.5% oxygen-stored apples removed from CA storage. It is unknown whether the ACAT protein is reactivated by exposure to ambient oxygen or synthesized de novo.

1-Methylcyclopropene and storage temperature influence responses of ‘Gala’ apple fruit to gamma irradiation

Abstract ‘Gala’ apple ( Malus x domestica Borkh.) fruit pre-treated with 0.5 μL L −1 1-methylcyclopropene (MCP) or air (control) for 12 h at 20 °C were exposed to gamma radiation at doses of 0, 0.44, 0.88 or 1.32 kGy at 23 °C. The fruit were then stored at 20 °C for 3 weeks or at 0 °C for 8 weeks plus 7 days at 20 °C. Fruit treated with MCP had higher firmness and titratable acidity (TA) than control fruit after storage at either temperature. During the post-irradiation storage at 20 °C, irradiation promoted respiration of MCP-treated fruit throughout the 3-week period but had no consistent effect on respiration of control fruit. Fruit firmness and TA decreased with increased radiation dose after 3 weeks storage at 20 °C regardless of MCP treatment. Compared to non-irradiated fruit, irradiated fruit had lower TA and similar firmness after storage at 0 °C for 8 weeks plus 7 days at 20 °C. Some irradiated fruit stored at 20 °C for 3 weeks developed internal browning, and MCP-treated fruit had more injury than control fruit. Storage at 0 °C after irradiation greatly reduced development of internal browning. Production of volatile esters, alcohols and 6-methyl-5-hepten-2-one by fruit stored at 0 °C was reduced. The magnitude of reduction directly increased with radiation dose. It appears that some responses of apple fruit to gamma radiation are influenced by ethylene action and post-irradiation storage temperature.

Ripening and quality of 'Laetitia' plums following harvest and cold storage as affected by inhibition of ethylene action

Abstract – The inhibition of ethylene action by 1-methylcyclopropene (1-MCP) extends shelf and storagelife of many climacteric fruits. However, 1-MCP appears to have limited effects on stone fruit dependingon specie and cultivar. The effects of 1-MCP on ripening and quality of ‘Laetitia’ plums were determinedduring ripening at 23 o C following harvest and cold storage. Japanese plums ( Prunus salicina , cv. Laetitia)were harvested at mature pre-climacteric stage, cooled to 2 o C within 36 hours of harvest and then treatedwith 0, 0.05, 0.10, 0.50 or 1.00 µL L -1 of 1-MCP at 1°C for 24 hours. Following treatment, fruits wereeither held at 23 o C for 16 days or stored at 1 o C for 50 days. Fruits were removed from cold storage at 10-day intervals and allowed to ripe at 23°C for five days. A delay of climacteric respiration and ethyleneproduction by 1-MCP treatment during ripening following harvest and cold storage was associated to aslow rate of fruit softening. 1-MCP treatment also delayed the loss of titratable acidity and changes of fleshand skin color, whereas it had little or no effect on soluble solids content. 1-MCP effects were concentration-and storage duration-dependent and, generally, a saturation fruit response to 1-MCP occurred between 0.5and 1.0 µL L

Combination of Hot-Water Surface Pasteurization of Whole Fruit and Low-Dose Gamma Irradiation of Fresh-Cut Cantaloupe

Improvements in methods for disinfecting fresh-cut cantaloupe could reduce spoilage losses and reduce the risk of foodborne illness from human pathogen contamination. The objective of this study was to investigate the feasibility of using hot-water treatment in combination with low-dose irradiation to reduce native microbial populations while maintaining the quality of fresh-cut cantaloupe. Whole cantaloupes were washed in tap water at 20 or 76 degrees C for 3 min. Fresh-cut cantaloupe cubes, prepared from the washed fruit, were then packaged in clamshell containers, and half the samples were exposed to 0.5 kGy of gamma radiation. Native microflora populations and sensory qualities were evaluated during the subsequent 7 days of storage at 4 degrees C. The hot-water surface pasteurization reduced the microflora population by 3.3 log on the surface of whole fruits, resulting in a lower microbial load on the fresh-cut cubes compared with cubes cut from fruit treated with cold water. Irradiation of cubes prepared from untreated fruit to an absorbed dose of 0.5 kGy achieved a low microbial load similar to that of cubes prepared from hot-water-treated fruit. The combination of the two treatments was able to further reduce the microflora population. During storage, the headspace atmosphere of the packages was not significantly influenced by any of the treatments. Color, titratable acidity, pH, ascorbic acid, firmness, and drip loss were not consistently affected by treatment with irradiation, hot water, or the combination of the two. Cubes prepared from hot-water-treated whole fruit had slightly lower soluble solids content. The combination of hot-water pasteurization of whole cantaloupe and low-dose irradiation of packaged fresh-cut melon can reduce the population of native microflora while maintaining the quality of this product.

Responses of ‘Fuji’ apples to short and long duration exposure to elevated CO2 concentration

Abstract Fruit maturity, diphenylamine (DPA) treatment and controlled atmosphere (CA) storage regimes were evaluated as factors affecting development of ‘Fuji’ apple CO 2 injury. The incidence and severity of CO 2 injury (brown-heart) increased with advanced maturity and greater watercore severity at harvest. The development of CO 2 injury during storage was prevented by DPA treatment. The severity of CO 2 injury was higher in fruit exposed to 20 kPa CO 2 after harvest than in fruit exposed to 20 kPa CO 2 after 8 months of CA storage. Ethanol, acetaldehyde and methanol concentrations increased during short- and long-term exposure to high CO 2 , however, DPA reduced ethanol and acetaldehyde accumulation. Storage in low O 2 (0.5 kPa O 2 , 0.05 kPa CO 2 ) also stimulated accumulation of ethanol, acetaldehyde and methanol however, no internal disorders developed with or without the use of DPA. The harvest date effect on severity of CO 2 -injury following short-term exposure to 20 kPa CO 2 was related to severity of CO 2 -injury after long-term CA storage with 3 kPa CO 2 .

Use of chemical sanitizers to reduce microbial populations and maintain quality of whole and fresh-cut cantaloupe.

Whole cantaloupes either not inoculated or inoculated with Salmonella Poona were submerged in water, 180 ppm of chlorine, acidified calcium sulfate (ACS: 1.2% Safe(2)O-ACS50), 1,000 ppm of acidified sodium chlorite (ASC), 80 ppm of peroxyacetic acid (PAA), and a combination of ACS and PAA for 10 min. Although only ASC and the combination of ACS and PAA significantly reduced the aerobic plate count of samples taken from the surface of whole cantaloupe (compared with samples taken from cantaloupe submerged in water only), all treatments reduced yeast and mold counts on the whole cantaloupe. However, none of the treatments of whole cantaloupes consistently reduced yeast and mold counts for the samples of fresh-cut cantaloupes. The aerobic plate counts for fresh-cut cantaloupe were reduced by 1 to 2 log CFU/g by sanitization of whole fruit with ASC, ACS, and the combination of ACS and PAA. The low bacterial population on the fresh-cut fruit was maintained during 14 days of storage at 4 degrees C. All treatments had a limited effect on the population of Salmonella, achieving no more than a 1.5-log reduction of the pathogen inoculated on the surface of the whole cantaloupes. Salmonella was nondetectable via direct plating (with a detection limit of 0.4 log CFU/g) in fresh-cut cantaloupes prepared from whole cantaloupes treated with any of the sanitizers. However, after enrichment, Salmonella often was detectable. Color, texture, soluble solids, pH, ascorbic acid, and drip loss of cut cantaloupes were not consistently affected by any of the whole-fruit treatments. Overall, treatments of whole cantaloupe with ASC, ACS, and the combination of ACS and PAA at the concentrations tested permitted a significant reduction in Salmonella and native microflora of whole and cut fruit; however, Salmonella still could be found in cut cantaloupes from all treatments.

Natural surface coating to inactivate Salmonella enterica serovar Typhimurium and maintain quality of cherry tomatoes.

The objective of the present study was to investigate the effectiveness of zein-based coatings in reducing populations of Salmonella enterica serovar Typhimurium and preserving quality of cherry tomatoes. Tomatoes were inoculated with a cocktail of S. Typhimurium LT2 plus three attenuated strains on the smooth skin surface and stem scar area. The zein-based coatings with and without cinnamon (up to 20%) and mustard essential oil or a commercial wax formulation were applied onto tomatoes and the treated fruits were stored at 10 °C for up to 3 weeks. Populations of S. Typhimurium decreased with increased essential oil concentration and storage duration. S. Typhimurium populations on the smooth skin surface were reduced by 4.6 and 2.8 log colony forming units(CFU)/g by the zein coatings with 20% cinnamon and 20% mustard oil, respectively, 5h after coating. The same coating reduced populations of S. Typhimurium to levels below detection limit (1.0 log CFU/g) on the stem scar area of tomato during 7 days of storage at 10 °C. Salmonella populations were not reduced on fruit coated with the commercial wax. All of the coatings resulted in reduced weight loss compared with uncoated control. Compared with the control, loss of firmness and ascorbic acid during storage was prevented by all of the coatings except the zein coating with 20% mustard oil which enhanced softening. Color was not consistently affected by any of the coating treatments during 21 days of storage at 10°C. The results suggest that the zein-based coating containing cinnamon oil might be used to enhance microbial safety and quality of tomato.