Osmotic dehydration of apple slices using a sucrose/CaCl2 combination to control spoilage caused by Botrytis cinerea, Colletotrichum acutatum, and Penicillium expansum

The efficacy of sucrose combined with CaCl2 during osmotic dehydration (OD) was tested for the control of Botrytis cinerea, Colletotrichum acutatum, and Penicillium expansum growth on lightly processed apple slices. The objective of this work was to determine whether the addition of CaCl2 in the osmotic solutions would limit the proliferation of fungal decay organisms. Slices were submitted to OD for 1 h at 25 degrees C in solutions containing 5 to 65% sucrose. Calcium chloride was added to a similar set of sucrose solutions at 0 to 8%. Control slices were made of untreated slices, and slices were processed in water. The mass ratio of the slices did not vary when fruit pieces were processed in solutions containing 5 to 65% sucrose. These slices showed a high susceptibility to spoilage compared to the control slices not submitted to OD: a significant twofold and 60% increase in decay area caused by B. cinerea and P. expansum, respectively, was observed when slices were processed in 50% sucrose/0% CaCl2; C. acutatum showed a significant 50% increase in decay area when slices were processed in 20% sucrose/0% CaCl2. Calcium uptake was significantly increased when slices were processed in CaCl2 solutions, and the highest Ca content was observed when processed in 8% CaCl2, reaching 40 times that of the control slices processed in water. Calcium-treated slices were less susceptible to spoilage by all three pathogens, and the most effective combination in reducing apple slice spoilage was 20 to 30% sucrose combined with 2% CaCl2.     

l-glutamate inhibits blue mould caused by Penicillium expansum in apple fruits by altering the primary nitrogen and carbon metabolisms

Although several studies have shown the ability of l -glutamate (glutamate) to mitigate the stress imposed by pathogens, the underlying mechanism is still in its infancy. To gain further knowledge, this study focussed on the effect of glutamate on primary nitrogen and carbon metabolisms during apple-Penicillium expansum interaction. The obtained result showed that glutamate could effectively restrict blue mould rot development in apples, but had no direct impact on fungal growth in vitro. The application of glutamate increased the level of nitrogen in apples, resulting in a disrupted balance of carbon and nitrogen. Consistently, the key enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT) involved in the GS/GOGAT cycle, and the deaminating activity of glutamate dehydrogenase (GDH), forming 2-oxoglutarate and ammonium from glutamate, were promptly stimulated by glutamate. Interestingly, glutamate led to considerable consumption of the tricarboxylic acid (TCA) cycle intermediates, such as isocitric acid and citric acid, accompanied by the enhancement of malate dehydrogenase and succinate dehydrogenase activities. Collectively, exogenous application of glutamate might confer blue mould resistance in apples, at least in part, by redirecting host’s primary nitrogen and carbon metabolisms, such as the activation of the GS/GOGAT cycle, deaminating activity of GDH and the TCA cycle.     

扩展青霉利用苹果渣发酵产果胶酶条件的优化

通过单因素及二次旋转正交实验,对扩展青霉YL-9固体发酵产果胶酶的培养条件进行了探索。结果表明:最佳培养基组成为:麸皮8.15%、苹果渣16.5%、(NH4)2SO40.86%、MnSO40.3%、KCl0.15%、0.04%的吐温80、加水量74.0%。采用最佳培养基配方,在250mL三角瓶中于28℃下恒温培养96h,果胶酶酶活可达到752.29U/g干曲。     

Osmotic dehydration of apple slices with CaCl2 and sucrose limits decay caused by Penicillium expansum, Colletotrichum acutatum, and Botrytis cinerea and does not promote Listeria monocytogenes or total aerobic population growth.

The interaction of Penicillium expansum Link, Colletotrichum acutatum, and Botrytis cinerea Pers.:Fr. with Listeria monocytogenes on osmotically dehydrated apple slices was evaluated. In mineral analyses of the slices, the calcium content of the peel and flesh tissues increased by 4- and 11-fold, respectively, when processed in 2% CaCl2. These slices also exhibited less decay by P. expansum, C. acutatum, and B. cinerea. Inoculation of slices with P. expansum resulted in a decrease in the pH of the flesh tissue at the infection site, while the pHs of slices infected with C. acutatum and B. cinerea increased and remained stable, respectively. Total mold population increased in wounds inoculated with P. expansum or C. acutatum. The presence of L. monocytogenes in the wounds did not significantly affect mold growth. The association of P. expansum and L. monocytogenes on apple slices resulted in a decrease in the bacterial population, whereas L. monocytogenes survived when slices were inoculated with C. acutatum. When associated with B. cinerea, there was a fourfold decrease in the L. monocytogenes population when slices were treated with 2% CaCl2. The total aerobic population was not significantly affected by the type of microorganism added to the wounds or by the osmotic treatment. These data show that osmotic dehydration with 2% CaCl2 combined with 20% sucrose limits decay of apple slices and does not promote bacterial or total aerobic population growth.     

Effects of the origins of Botrytis cinerea on earthy aromas from grape broth media further inoculated with Penicillium expansum

Earthy “off” aromas from wine and grape juice are highly detrimental to the production of quality grape products. These volatile compounds are produced on grapes by Botrytis cinerea, Penicillium expansum and/or a combination of P. expansum and B. cinerea strains. B. cinerea strains were isolated from different (a) vineyards in Spain and Portugal, (b) grape varieties (c) bunches (i.e., sound and botrytized) and (d) positions in the botrytized bunch (i.e., interior or exterior). A novel Headspace-Phase Microextraction (SPME) followed by Gas Chromatrography/Mass Spectrometry (GC-MS) dedicated to analyze geosmin, methylisoborneol (MIB), 1-octen-3-ol, fenchone and fenchol in grape broth medium was used. Approximately 50% of the B. cinerea strains induced detectable geosmin. One strain accumulated significant amounts of anisoles, demonstrating that this contamination might already occur in the vineyard. Strains from the interior of Cainho grape bunches induced more geosmin and hence it may be possible to reduce this volatile in wine by avoiding using these grapes in case of B. cinerea attack.     

Control of Penicillium expansum and Botrytis cinerea on apples and pears with the combination of Candida sake and Pantoea agglomerans.

The effectiveness of Candida sake (CPA-1) in combination with Pantoea agglomerans (CPA-2) for controlling Penicillium expansum and Botrytis cinerea on pears and apples was determined. The concentrations tested were 2 x 10(6) and 2 x 10(7) CFU/ml for C. sake and 2 x 10(7) and 8 x 10(7) CFU/ml for P. agglomerans. At room temperature, the two antagonists were combined in proportions of 0 to 100% in 25% increments. At the proportion of 50:50, no rot development was observed in pears, and the greatest control of blue mold in apples was observed at this proportion for all the tested concentrations. Under cold temperature on pears, the highest effectiveness of the mixture was observed when C. sake at 2 x 10(7) CFU/ml was combined with P. agglomerans at 2 x 10(7) or at 8 x 10(7) CFU/ml at the proportion 50:50. Under these conditions, no rot development of blue mold was reported, and gray mold lesion size was reduced by more than 95%. On apples, the mixture of C. sake at 2 x 10(7) CFU/ml and P. agglomerans at 8 x 10(7) CFU/ml at the proportion 50:50 reduced blue and gray mold incidence by 90%. Populations of the two antagonists had the same growth pattern at 20 degrees C when they were applied individually or in combination, but the population level was always higher when they grew alone. In contrast, at 1 degrees C, the population of both antagonists in combination formed a stable community with the same levels as individual application during the first 30 days; after that, C. sake dominated, and P. agglomerans decreased on apples and pears. At both temperatures, the maximum population level of C. sake was observed in apples, and themaximum population level of P. agglomerans was observed in pears.     

Biological control of Penicillium digitatum by Trichoderma viride on postharvest citrus fruits

In previous studies it was shown that Trichoderma viride, isolated from Spanish citrus packing houses, showed antagonistic activity against Penicillium digitatum in in vitro laboratory tests. In the present in vivo studies Navelina oranges, protected with aqueous suspension of T. viride (2.5 x 10(6) to 2.5 x 10(9) spores per ml), showed an increase in resistance toward P. digitatum. Oranges, inoculated with P. digitatum, did not produce lesions after 5 days when T. viride was applied 48 h or 72 h before inoculation.     

Transmission of Botrytis cinerea by lightbrown apple moth larvae on grapes

Larvae of lightbrown apple moth, Epiphyas postvittana Walker (Lepidoptera: Tortricidae) (LBAM) transmitted Botrytis cinerea Pers. Fr. (Bc) on veraison bunches in a field experiment at Lenswood, South Australia. The presence of Bc-contaminated LBAM larvae at veraison resulted in up to 59% of bunches infected with Bc at harvest, compared with 27% of bunches with uncontaminated larvae and 18% when no larvae were added. Under these field conditions, up to an additional 13% by weight of berry damage could be attributed to LBAM transmission, compared with controls. There was little evidence that the presence of contaminated LBAM larvae on bunches at flowering increased the incidence of infected bunches at harvest. Surveys of LBAM larvae collected from vines during the 1996/97 season showed up to 32% of larvae at Eden Valley were naturally contaminated with Bc, while the frequency at Padthaway and Coonawarra did not exceed 5%. Laboratory experiments demonstrated that LBAM larvae carry conidia of Bc on their cuticle, which explains the transmission within bunches observed in the field. Viable propagules of Bc were recovered from faecal pellets of LBAM. The habit of faecal dispersal by LBAM larvae may contribute to the build-up of Bc inoculum in a vineyard.     

Effects of apple and pear varieties and pH on patulin accumulation by Penicillium expansum

BACKGROUND: Accumulation of patulin in apples and pears and subsequently in their by‐products is caused mostly by Penicillium expansum which causes blue mould. Fruit pH and other parameters are sometimes characteristic of a certain variety and thus the use of particular varieties might affect patulin content in the final products. The aim of this study was to evaluate the influence of fruit variety and pH on patulin accumulation. Patulin accumulation in both apple and pear juices at different pH and also in different apple varieties (Golden, Gala and Fuji) and pear varieties (Blanquilla and Conference) was assessed. RESULTS: The pH of juices significantly influenced patulin accumulation, especially in apple juice in which the highest amounts of patulin were detected at pH 3.5. In fruits, the pH values of the substrate were determinant only under cold storage. Thus, Golden apples, which presented a lower pH, accumulated more patulin at 1 °C. However, this trend was not observed at other temperatures in which varieties with higher amounts of organic acids (Golden and Fuji apples) accumulated most patulin. In the pear varieties, significant differences in pH did not lead to significant differences in patulin accumulation. CONCLUSION: Although pH influences patulin accumulation, other factors such as organic acid content may play an important role. Concerning the apple and pear varieties we studied, it seems that rather than variety, other parameters like pH or acidic content may be more important. These parameters vary significantly depending on the degree of ripeness of the fruit. Gala apple, which is used in Spanish juice production, was the only variety that accumulated dramatically higher amounts of patulin. Copyright © 2008 Society of Chemical Industry     

Biological control of postharvest pear diseases using a bacterium, Pantoea agglomerans CPA-2.

Epiphytic microorganisms isolated from the fruits and leaf surfaces of apples and pears were screened for antagonistic activity against Penicillium expansum on pears. From 247 microorganisms tested for antagonistic properties against P. expansum, a bacterium strain identified as Pantoea agglomerans (CPA-2) was selected. This bacterium was very effective against Botrytis cinerea, P. expansum and Rhizopus stolonifer. Complete control at the three tested concentrations (2 x 10(7), 8 x 10(7) and 1 x 10(8) CFU ml(-1)) was obtained on wounded pears inoculated with 10(3), 10(4) and 10(5) conidia ml(-1) of P. expansum and R. stolonifer. At 8 x 10(7) CFU ml(-1), Pan. agglomerans reduced B. cinerea decay by more than 80% at the three concentrations of the pathogen. In over 3 years of experiments in semicommercial trials, Pan. agglomerans provided excellent control against B. cinerea and P. expansum under cold storage, either in air or in low oxygen atmospheres. Equal control was obtained with Pan. agglomerans at 8 x 10(7) CFU ml(-1), as with the fungicide imazalil at commercial doses, against both pathogens. Pan. agglomerans grew well inside wounds on pears at both room and cold temperatures and under modified atmospheres. In contrast, it grew poorly on the surface of intact fruit.     

朝鲜辣白菜中抗扩展青霉乳酸菌的筛选与鉴定

该研究采用菌饼法从朝鲜辣白菜中筛选抗扩展青霉（Penicillium expansum）的乳酸菌,采用形态观察、生理生化试验及分子生物学技术进行菌种鉴定,并对乳酸菌抗扩展青霉的机理进行初步研究。结果表明,经过筛选和鉴定,获得1株对扩展青霉抑制效果最佳的清酒乳杆菌（Lactobacillus sakei）PC-3,抑菌率为68.62%。菌株PC-3无细胞上清液（CFS）的抗真菌活性随pH的升高呈现先升高后降低的趋势;随温度的升高逐渐下降。初步判定菌株PC-3 CFS中抗扩展青霉的有效成分是乳酸和乙酸,其对扩展青霉抑菌率分别为67.58%和66.73%。经扫描电镜观察发现,菌株PC-3 CFS抗扩展青霉的机制为破坏其细胞结构,导致胞内物质泄漏。     

纳他霉素对葡萄采后灰霉病菌的毒力及其防腐保鲜效果

以常用食品防腐剂山梨酸钾为对照研究了纳他霉素对葡萄采后灰霉菌的抑制毒力以及防腐保鲜效果。通过测定不同浓度的抑菌液对灰霉菌菌丝生长的抑制活性,以确定其抑制毒力。通过采前浸果处理,分别从感官指标、内在品质和代谢生理三方面研究纳他霉素对葡萄采后灰霉病的抑制效果。结果表明:纳他霉素抑菌液对葡萄采后灰霉菌的抑菌中浓度值(EC50=433.96 mg/L)明显小于山梨酸钾对照防腐液(EC50=5 753.65 mg/L);与对照相比,纳他霉素采前处理可有效抑制葡萄果实霉烂率和果梗褐变指数的增加,并较好的保持果实中可溶性固形物、可滴定酸和Vc含量,明显抑制贮藏后期果粒呼吸强度、果实质膜透性以及MDA含量的增加。综上,纳他霉素对葡萄采后灰霉菌的生长具有非常明显的抑制毒力,在鲜食葡萄的采后生物保鲜领域具有较好的应用前景。     

Inactivation of Penicillium expansum spores in apple juice by contact glow discharge electrolysis and its related mechanism

Penicillium expansum spores in apple juice were treated with contact glow discharge electrolysis (CGDE), and the effect of different parameters on the efficiency of spore inactivation and the related mechanism were investigated. We found that CGDE effectively inactivated spores of P. expansum in the clarified apple juice. CGDE achieved a 3.71 log inactivation of spores in the juice with 1 cm electrode gap, at 520 V, and discharge time for 15 min. CGDE produced hydrogen peroxide in the juice, and the concentration reached 58.1 mg/L after discharged for 30 min. CGDE destroyed the integrity of the cell membrane in the spores, and reduced the activities of superoxide dismutase, catalase, and peroxidase by 68.1%, 81.8%, and 68.0% after discharged for 30 min. In addition, CGDE inhibited mycelial growth, reduced colony diameter by 18.9%, and decreased the lesion diameter by 41.4% in apples surface-inoculated with P. expansum. Taken together, CGDE could inactivate the spores of P. expansum in apple juice by inducing reactive oxygen species accumulation and disrupting the integrity of cell membrane of spores.Industrial relevanceCGDE can effectively inactivate the spores of P. expansum in apple juice. The device of CGDE is composed of a high voltage DC power supply, electrodes and a reaction vessel, which is connected easily with material pipeline, and suitable for handling liquids. Therefore, CGDE can be applicated in treating liquids contaminated with fungal spores in the food industry.     

温度对苹果汁中扩展青霉生长和产毒的影响

在苹果汁培养基静置培养条件下,研究了培养温度为28、25、20、16、12、4℃时扩展青霉的生长和产毒情况。结果表明,在各贮藏温度下,扩展青霉均可在苹果汁中生长,并产生大量毒素。温度越高,生长速率和产毒速率越快,但生长高峰期和产毒高峰期发生的先后顺序差别很大。其中25℃是扩展青霉的最适生长和产毒温度,最大生物量和产毒量分别达到4.35 g/L和570.53 mg/L,在冷藏温度4℃时菌体仍能生长和产毒。因此在苹果汁的生产和贮藏过程中要充分考虑温度的影响,以减少果汁中展青霉素污染的风险。     

Reduction of nectarine decay caused by Rhizopus stolonifer, Botrytis cinerea and Penicillium digitatum with Aloe vera gel alone or with the addition of thymol

Two nectarine cultivars (‘Flavela’ and ‘Flanoba’) were treated with Aloe vera gel alone, or with the addition of thymol, and then inoculated with Rhizopus stolonifer, Botrytis cinerea and Penicillium digitatum. Both treatments were effective in reducing the decay incidence caused by the 3 fungi species, although the addition of thymol did not generally improve the efficacy of Aloe vera gel on reducing the infection damage. The coatings were clearly effective in reducing the postharvest ripening process of both nectarine cultivars manifested by a delay in ethylene production and respiration rate, weight loss and softening. Interestingly, these coatings showed effectiveness on reducing decay development in inoculated fruits and thus Aloe vera could be considered as natural antifungal compound and might serve as alternative of synthetic fungicides.     

苹果组织pH值对扩展青霉生长及棒曲霉素分泌的影响研究

目的 探究苹果组织pH值对扩展青霉生长及棒曲霉素(patulin, Pat)分泌的影响。方法 选取3种不同酸度的苹果(红富士、青金帅、国光, pH值分别为3.83、3.61、3.43)作为实验材料, 分析扩展青霉在苹果不同部位上的生长规律, 以及毒素的分泌情况。结果 苹果组织pH值能够影响扩展青霉的致病力, 苹果病斑直径、相同部位扩展青霉数量及Pat含量与苹果组织pH值呈正相关; 苹果果实硬度也对扩展青霉的生长和Pat分布有一定影响, 硬度较低的青金帅苹果健康组织中扩展青霉菌落数量和Pat含量高于红富士和国光苹果。 结论 苹果组织pH值能够影响扩展青霉菌的致病力, 品种对扩展青霉侵染及毒素产生也有较大的影响。     

Biological control of postharvest decays of apple can prevent growth of Escherichia coli O157:H7 in apple wounds

Fresh cells of the antagonist Pseudomonas syringae at 2.4 x 10(8) CFU/ml inoculated into wounds of 'Golden Delicious' apple prevented Escherichia coli O157:H7 (concentrations ranging from 2.4 x 10(5) to 2.4 x 10(7) CFU/ml) from growing in the wounds. This occurred when the two microorganisms were co-inoculated or inoculation with E. coli O157:H7 was conducted 1 or 2 days after inoculation with the antagonist. In similar tests, application of the commercial formulation of this antagonist prevented the growth of E. coli O157:H7 in wounds when inoculated 1 or 2 days after application of the antagonist. Populations of E. coli O157:H7 in wounds treated with water (control) before inoculation with this pathogen increased approximately 2 log units during the first 48 h after inoculation. These results indicate that biocontrol agents developed for controlling storage decays of fruits may have the additional benefit of preventing the growth of foodborne pathogens in freshly wounded tissue of intact and fresh-cut fruits.     

Isolation and characterization of antagonists for the biocontrol of the postharvest wound pathogen Botrytis cinerea on strawberry fruits

Antagonistic bacteria and yeasts were isolated from the epiphytic flora of stored strawberry fruits and evaluated for their ability to protect strawberry fruit wounds after harvest against Botrytis cinerea. Among selected potential antagonists, three strains of Candida reukaufii (5L3, 10CL4, 10L2) and one strain of Candida pulcherima (10L8) still protected fruit wounds when applied at 10(3) CFU/wound, reducing lesion or conidiophore development. In the same conditions, two Enterobacteriaceae (10B1, 5B4) highly reduced pathogen development. Strain 5B4 was still highly inhibitory when inoculated at 10(2) CFU/wound. The six strains applied on fruits did not produce any significant change in color, brightness, and firmness of fruits. The two yeasts, 5L3 and 10L8, and particularly the two bacteria, 5B4 and 10B1, were selected for further studies. The four antagonists effectively colonized fruit wounds and strongly inhibited spore germination of B. cinerea in vitro. The bacterial cells surrounded the germinating spores of B. cinerea and attachment of 5L3 cells on germinating spores were additionally observed. Bacterial antagonists, particularly the strain 5B4, multiplied and rapidly used carbohydrates in strawberry fruit juice despite the low pH (pH 3.5). The efficiency of the bacterial antagonists on fruit wounds was related to their growth and nutritional properties.