Pear Surfaces Research Articles

Inactivation of Escherichia coli Population on Fruit Surfaces Using Ultraviolet-C Light: Influence of Fruit Surface Characteristics

Ultraviolet-C (UV-C 254 nm) light is a possible alternative for chemical disinfection of fresh fruits. However, studies on the influence of surface characteristics on the kinetics of UV-C inactivation of microorganisms on fruits are limited. In this study, UV-C inactivation of generic Escherichia coli (ATCC 23716), a nonpathogenic surrogate strain for E. coli O157:H7, was inoculated onto the skin surface intact pear, pear with surface wounds, and the skin surface of intact peach. Disc shaped (0.057 m diameter × 0.01 m height) fruit surface were exposed at room temperature to UV-C light ranging from 0 to 7.56 ± 0.52 kJ/m2 and microbial inactivation kinetics was determined. Maximum reductions of 3.70 ± 0.125 log CFU/g were achieved for E. coli on intact pear surfaces (P < 0.05), with lesser reduction on wounded pear (3.10 ± 0.329 log CFU/g) and peach surfaces (2.91 ± 0.284 log CFU/g) after 4 min UV-C exposure at 7.56 kJ/m2 UV. The Weibull scale factor (α) values of UV-C inactivation for E. coli on an intact pear surface was 0.001 ± 0.0007 min (0.235 ± 0.001 kJ/m2), wounded pear surface, 0.003 ± 0.001 min (0.240 ± 0.002 kJ/m2) and peach surface, 0.004 ± 0.0004 (0.241 ± 0.0008 kJ/m2). The time required for a 90 % reduction in E. coli cell numbers or the reliable life time (t R) calculated with the Weibull model for intact pear surfaces (0.019 ± 0.009 min, 0.268 ± 0.017 kJ/m2) was smaller than for wounded pear (0.062 ± 0.013 min, 0.348 ± 0.024 kJ/m2) and peach surfaces (0.074 ± 0.012, 0.371 ± 0.012 kJ/m2), suggesting that the wounds on pear surfaces and trichomes (100–1000 μm) on peach surfaces helped to shield and protect microorganisms from UV-C radiation. There was likely a more uniform distribution of bacterial cells onto pear surfaces due to its smaller surface roughness, spreading coefficient, and hydrophobic nature compared to peach. Fourier transform infrared spectroscopy indicate that bacterial membrane damage (phospholipids, protein secondary structures, and polysaccharides) and changes to DNA/RNA in E. coli resulted from UV-C treatment. UV-C can reduce E. coli populations on fresh fruit surfaces, but the efficacy of UV treatment is dependent upon the morphological and surface properties of the fruit and surface integrity.

Preservation of pears in water in the presence of Sinapis arvensis seeds: A Greek tradition

In this research, the microbiological and physicochemical changes during preservation of pears in water in the presence of Sinapis arvensis seeds (PWS FL) according to the traditional Greek home food manufacture were studied. Pears preserved in water served as control (PW FL). The growth of lactic acid bacteria (LAB) coming from the pear surface was enhanced in the presence of Sinapis seeds, while Enterobacteriaceae and Gram-negative bacteria declined coincidently with the lower (P<0.05) pH of the PWS FL. LAB predominated over the other microbial groups in the fermentation liquids (FLs) of both systems. All the 49 LAB isolates from one fermentation experiment were identified as Leuconostoc mesenteroides subsp. cremoris by the SDS–PAGE of whole-cell proteins, while RAPD-PCR fingerprinting and partial 16S rRNA sequence determination of selected isolates did not discriminate them at the subspecies level.Fruit preserved in PWS FL had higher titratable or volatile acidity, phenolic compounds or antioxidant capacity as well as lower pH and firmness than the control fruit. All physicochemical parameters of the FLs increased except of the pH which decreased. Coincidently with higher population of LAB in PWS FL the levels of citric, lactic and acetic acid were higher than in control. Oxalic acid and related unknown substances were found at higher levels in PWS FL than the control and may be the agent(s) enhancing the growth of LAB and/or contributing partially to the decline of Enterobacteriaceae. The organoleptic test showed that fruit preserved in PWS FL had better overall acceptance than the control, and that it retained most of the positive traits.

사육상에서 까치, 물까치, 직박구리의 과실먹이 섭식행동

조류 종별로 과수원의 과실을 가해하는 행동 특성을 확인하고자 본 연구를 수행하였다. 각 조류별로 특징적인 경향을 확인할 수 있었는데, 까치는 부리로 과피를 수직으로 쪼며 물까치와 직박구리는 큐티클층에 부리가 미끄러진 흔적과 과실 내부에 주머니 모양으로 원형 흔적을 남겼다. 봉지재배를 하는 배와 사과 과실은 조류의 종류에 따라 다른 섭식행동을 유발시킬 수 있다. 까치의 경우 봉지의 존재 여부를 떠나 과실을 가해 할 수 있으나 물까치와 직박구리는 건전한 봉지로 씌워져 있을 경우 가해하지 않았다. 그리고 사육상 시험에서 물까치와 직박구리는 온주밀감과 사과 과실보다는 배 과실을 더 선호하였다. 물까치와 직박구리의 피해를 경감시키기 위해서 봉지재배를 하는 과실의 경우 봉지가 훼손되지 않도록 할 필요가 있다. 또한 제주지역에 물까치가 유입되지 않도록 해서 감귤 과실피해를 막아야 한다. To investigate the bird's dieting behavior for several fruits in orchards, this study was carried out in 2008. Black-billed magpies (Pica pica), azure-winged magpies (Cyanopica cyanus), and brown-eared bulbuls (Hypsipetes amaurotis) made their unique marks on the surface of pear and apple fruits; black-billed magpies pecked fruits strongly and left round holes with perpendicular angle, whereas those of azure-winged magpies and brown-eared bulbuls were sack-shaped with narrow neck and marked unique stripes on the skin. For the fruits of pear and apple from bagging practices, the birds showed different foraging behavior; black-billed magpies could injure all kinds of fruits whether with paper bags or not, but azure-winged magpies and brown-eared bulbuls could not attack the fruits with paper bag. Azure-winged magpies and brown-eared bulbuls preferred pear fruits to those of apples and satsuma mandarins in the cage trials. To reduce the injuries by azure-winged magpies and brown-eared bulbuls on pear and apple fruit, wrapping bag should not be impaired. Introducing azure-winged magpies to Cheju should be prohibited for the potential citrus injury by them.

Preliminary prospection of the yeast biodiversity on apple and pear surfaces from Northern Italy orchards

Apples and pears of four different cultivars from nine companies located in northern Italy have been submitted to the isolation of the blastomycetic flora before and after industrial washing, in order to individuate and isolate the resident yeasts, particularly those resistant to the industrial washing. Cultures of the following species were isolated: Aureobasidium pullulans, Candida oleophila, Debaryomyces hansenii, Hanseniaspora uvarum, Metschnikowia fructicola, Metschnikowia pulcherrima, Wickerhamyomyces anomalus, Meyerozyma guilliermondii, Pichia kluyveri and Rhodotorula glutinis. The most diffuse species was M. guilliermondii, found on all cultivars after washing. Species of the Metschnikowia gender and A. pullulans were also very common. Identification through rDNA 26 S and FTIR characterization made it possible to trace some strains and to establish that these were resistant to the washing treatment. The presence and distribution of superficial microbiota on apples was also shown by scanning electronic microscopy. This preliminary study has shown that the yeast cultures on the surfaces can be differentiated for their resistance to industrial treatments and that an increase of the yeast flora can be easily obtained.

EFFICACY OF NEUTRAL AND ACIDIC ELECTROLYZED WATER FOR REDUCING MICROBIAL CONTAMINATION ON FRESH-CUT FRUITS

Consumption of fresh-cut fruit has increased in the latest years. This type of product is more susceptible to microbial contamination. For this reason disinfection is a very important step in fresh-cut processing. Chlorine is the most common disinfectant in the fresh-cut industry but due to environmental and health risks caused by the use of this disinfectant there is a demand to develop new sanitizers. Electrolyzed water appears to be a promising alternative to chlorine sanitizers showing to be a broad spectrum microbial decontamination agent. Neutral electrolyzed water (NEW) and acidic electrolyzed water (AEW) can be used as microbial decontamination agents on fresh-cut fruits. The biocidal activity of NEW, AEW and sodium hypochlorite were evaluated to inactivate pure cultures of foodborne pathogens on the surface of fresh-cut apples, pears and oranges. Fruits were inoculated with Listeria innocua or Escherichia coli O157:H7 and treated with NEW, AEW at different concentrations and different times of exposure. The NEW and AEW treatments were compared with sodium hypochlorite and deionised water (control). The bacterial population was significantly reduced in all fruits treated with AEW at 200 ppm of free chlorine. Treatments with the AEW with 100 ppm free chlorine resulted in reductions higher or similar to NEW or sodium hypochlorite at the same content of free chlorine, and in general the effect of NEW was similar to H In conclusion, AEW or NEW seems to be a promising disinfection technique to reduce the amount of free chlorine used for the disinfection of fresh-cut fruits representing a safer way to ensure food safety in these products.

Fumigation of Stored Pome Fruit with Hexanal Reduces Blue and Gray Mold Decay

Stored apples and pears are subject to blue and gray mold decay incited by Penicillium expansum and Botrytis cinerea respectively. Hexanal, a C6 carbon aldehyde, used as a vapor provided effective control of both blue and gray molds in laboratory experiments on apple slices. A preliminary trial with ‘Anjou’ pears in bins showed that hexanal was not corrosive and could reduce gray mold in pears stored for 7 months. However details on the correct procedure for fumigating pome fruit were lacking, and further studies were needed to develop a reliable fumigation strategy. In trials with inoculated fruit, hexanal inactivated conidia of B. cinerea contaminating the pear surface when used at a rate of 2 mg·L−1 for 24 hours or 4 mg·L−1 for 18 hours. It was less effective on ‘Gala’ apples inoculated with conidia of P. expansum, but reduced blue mold decay to low levels at 15 ºC. On the other hand, hexanal increased gray and blue molds when used after wounds were made in inoculated fruit. The use of a preharvest treatment with cyprodinil (0.62 g·L−1) reduced both blue and gray molds in wounds with or without hexanal fumigation. Thus a strategy for controlling postharvest decay was developed by which fruit were treated 2 weeks before harvest with cyprodinil, followed by fumigation with hexanal immediately after harvest. The use of this strategy on ‘Anjou’ pears produced the highest number of mold-free fruit in 2003 and the least amount of gray and blue mold decay in 2003 and 2004 on pears stored for 4 months. Wounded apples only developed 1% rot compared with 10% in the control, indicating that hexanal fumigation of stored apples reduced contamination. Monitoring hexanal during fumigation showed that hexanal concentration declined slowly over a 24-hour period and could accurately be described by a third-order polynomial equation. Hexanal fumigation at low rates (2–3 mg·L−1) was not phytotoxic and improved aroma in ‘Anjou’ pears and ‘Gala’ apples with no harmful effects on apple or pear firmness, pH, titratable acidity, or soluble solids.

Microbial interactions affecting stem-end blue mold decay of ‘d’Anjou’ pears

Stem-end decay of ‘d’Anjou’ pears caused by Penicillium expansum is the common decay of fruit kept in cold storage for extended periods of time. The succulent thick stems of ‘d’Anjou’ pear are prone to colonization by these fungi. We isolated bacteria and yeasts from surface of pear and apple fruits and evaluated them for their ability to colonize pear stem tissue. Populations of the best bacterial and yeasts colonizers increased by more than 2 log units within 3 d at 24 °C. They were then evaluated in cold storage at 1 °C for their ability to prevent infection of pear stems by a very aggressive strain of P. expansum, and a weakly pathogenic strain of a Penicillium sp. isolated from a pear stem. Only few isolates reduced stem-end decay. Two bacteria, Pseudomonas chlororaphis and Enterobacter sp. promoted fungal infection of the stem and subsequent fruit decay. The abundance of decay promoting bacteria in some years may be responsible for the high incidence of stem-end decay in those years.

Determination of O2 and CO2 permeance, internal respiration and fermentation for a batch of pears (cv. Conference)

Abstract By combining an existing gas exchange model with the diffusion of respiratory gases over the barrier of the fruit skin, a new gas exchange model was developed. Parameters describing O2 and CO2 permeance, internal respiration and fermentation for a batch of pears (Pyrus communis L. cv. Conference) were estimated using this new gas exchange model. The model was calibrated using data on gas exchange, internal and external gas composition and the surface of individual pears. The surface area was calculated using a computer imaging method. The absence of internal O2 gradients in the aqueous phase of a pear, a prerequisite for using a three-compartment model set up based on Fick’s first law, was confirmed using an O2-electrode probe. Data analysis using the combined gas exchange model resulted in estimated parameters indicating an increased internal affinity for O2 and increased internal fermentative CO2 production compared to data analysis using a traditional gas exchange model, based on external gas composition. The O2 and CO2 permeances were also derived using Ne efflux data. The estimated permeances using the combined gas exchange model were lower than those found with the Ne method. The lower permeances can be explained assuming that the Ne method only assesses the skin permeance, while the permeances for O2 and CO2 from the combined gas exchange model represent all the barriers between mitochondria, where respiration actually occurs, and the external atmosphere. The lower CO2 permeance found using the new model might also be explained by the relatively high pH of the cytosol.

Survival of Erwinia amylovora on pears and on fruit containers in cold storage and outdoors

The survival of Erwinia amylovora during cold storage or outdoors may be a relevant factor in the spread of fireblight. The survival of E. amylovora was studied in cold storage on pear fruits, on container materials and on packaging paper, and outdoors on wood (oak and poplar) and on polyethylene. The samples were contaminated with a bacterial suspension of a mutant strain, washed, concentrated by centrifugation, and the final concentrates were used for plate counting. In cold storage, reisolation from the calyx was successful even after 101 days, whereas on pear surfaces, it was unsuccessful after just 1 day. On oak and poplar wood, reisolation was obtained up to 77 days in cold storage for both types of wood, but only up to 27 and 55 days, respectively, outdoors. Reisolation from packaging paper in cold storage was successful up to 14 days. Reisolation from polyethylene outdoors was unsuccessful after 24 h. Survival curves were calculated for each material. On the basis of a model of inoculum transmission, and using the survival curves, a phytosanitary risk period for the different types of materials was estimated.

Extending shelf-life of peach and pear by using CMC from sugar beet pulp cellulose as a hydrophilic polymer in emulsions

Peach and pear were treated with different compositions of emulsions to extend shelf-life of fruits and to preserve the fruit quality. Paraffin wax, beeswax and soybean oil; carboxymethyl cellulose (CMC) with degree of substitution of 0.6670; Emulgin PE, triethanolamine, oleic acid and sodium oleate were used as hydrophobic phases, hydrophilic polymer and emulsifying agents in the coatings of peach and pear, respectively. The CMC obtained by etherification of the sugar beet pulp cellulose was used as a hydrophilic polymer. To investigate the post-harvest water loss of peach and pear, fruits were observed during storage while being subjected to dehydrating conditions in storage chamber at 25 °C and 75% relative humidity level. The changes in weight, pH, soluble solids, titratable acidity and ascorbic acid of the coated samples with storage time were measured at regular intervals throughout the storage period to evaluate the effect of storage period on fruit quality. The modified drying models describing the storage time dependence of weight loss were fitted to the experimental data and the model parameters in equations were determined by multiple regression analysis. Some of the coatings decreased the soluble solids, titratable acidity and ascorbic acid losses in comparison to the uncoated peaches and pears. The coating of peach and pear surfaces with emulsions containing CMC from sugar beet pulp cellulose as a hydrophilic polymer extended the shelf-lives of peach and pear to 12 and 16 days, respectively. It was found that a combination using beeswax as hydrophobic phase, triethanolamine and oleic acid as emulsifying agent, CMC as hydrophilic polymer and the emulsion containing soybean oil as hydrophobic phase, sodium oleate as emulsifying agent, CMC as hydrophilic polymers were suitable for the coating of peaches and pears, respectively.

Absorption and Translaminar Activity of Abamectin in Apple and Pear Foliage as Determined by Spider Mite (Acari: Tetranychidae) Mortality

Translaminar activity of abamectin was studied during 1992-1994 on apple. Malus X domestica Borkhauser, and pear, Pyrus communis L. Field-aged residues were bioassayed from the top or bottom leaf surface of apple and pear after atomizer application to the top or bottom surface, or handgun application to both surfaces. Tetranychus urticae Koch was used as the test organism with the exception of 1 experiment, which included Panonychus ulmi (Koch). Abamectin showed little translaminar activity on apple regardless of the leaf surface to which it was applied. There was preferential absorption by the bottom leaf surface, which resulted in higher levels of mortality for mites feeding on the bottom surface when this was also the treated surface (bottom/bottom [surface treated/surface assayed]). Mortality caused by other combinations (bottom/top, top/bottom, top/top) was minimal. Mortality from assays conducted on the bottom surface was also higher in the apple/handgun experiments. Translaminar activity was greater on pear, but primarily through the bottom leaf surface. The degree of translaminar movement was sufficient to cause comparable levels of mortality on both the top and bottom surfaces when applied solely to the bottom surface. There was no difference in mortality between the 2 mite species when assayed on the same leaf surface. However, based on control mortality and runoff, the bottom leaf surface of apple and pear is a more favorable habitat for T urticae than the top surface, whereas the opposite is true for P ulmi. The implications of mite host preference, feeding behavior, and differential absorption of abamectin are discussed.

Scanning electron microscopy of colonization of pear leaves by Pseudomonas syringae pv. syringae

A scanning electron microscope study was undertaken to determine how Pseudomonas syringae pv. syringae van Hall colonizes the surface of pear leaves and enters leaf tissue. Bacteria multiplied on the leaf surface, particularly on trichomes and in depressions of the cuticular layer. Masses of bacteria were associated with leaf spots, which appeared 9 days after inoculation under favorable conditions. The pathogen entered leaf tissue through the open base of trichomes and through microscopic fissures in depressions of the cuticular layer. The resident phase of P. syringae pv. syringae probably survives on trichomes of pear leaves.

In-line Application of Porous Wax Coating Materials to Reduce Friction Discoloration of ‘Bartlett’ and ‘d’Anjou’ Pears1,2

Abstract ‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) were passed through several brushrollers during washing, rinsing, waxing, and drying sequences of a simulated packing process. In-line application of Fresh-Cote, a wax coating formula with porosity, to the pear surface at waxing location of the packing line reduced peel discoloration of ‘Bartlett’, but not ‘d’Anjou’, due to brush friction. Fruits also were subjected to a return flow belt for 5 minutes to simulate the sorting sequence during packing. Fresh-Cote substantially reduced the susceptibility of both ‘Bartlett’ and ‘d’Anjou’ pears to peel discoloration due to belt friction.

Foliar Penetration of Naphthaleneacetic Acid: Enhancement by Light and Role of Stomata

Light enhanced the penetration of naphthaleneacetic-1-14C acid (NAA) into the stomatous lower surface of pear (Pyrus communis L. cv. Bartlett) leaf discs. The light effect was rapidly lost on transfer to the dark and was diminished by pretreatment of leaf discs with a Hill reaction inhibitor (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine). The effect of light on NAA penetration was isolated from its effect on stomatal opening. A similar stimulation of NAA penetration was obtained with stomata opened and closed, providing evidence that penetration did not take place by mass movement into the substomatal chamber.

FOLIAR PENETRATION OF NAPHTHALENEACETIC ACID: ENHANCEMENT BY LIGHT AND ROLE OF STOMATA

Light enhanced the penetration of naphthaleneacetic‐1‐14C acid (NAA) into the stomatous lower surface of pear (Pyrus communis L. cv. Bartlett) leaf discs. The light effect was rapidly lost on transfer to the dark and was diminished by pretreatment of leaf discs with a Hill reaction inhibitor (2‐chloro‐4‐ethylamino‐6‐isopropyl‐amino‐s‐triazine). The effect of light on NAA penetration was isolated from its effect on stomatal opening. A similar stimulation of NAA penetration was obtained with stomata opened and closed, providing evidence that penetration did not take place by mass movement into the substomatal chamber.