Search

During postharvest, table grapes are often spoiled by molds. Aspergillus sp., Alternaria sp., Botrytis sp., Cladosporium sp. and Penicillium sp. are different mold genera frequently related to table grape rot. Fungal spoilage affects nutritional value and organoleptic properties while also producing health hazards, such as mycotoxins. Traditionally, synthetic fungicides have been employed to control fungal diseases. However, possible negative effects on health and the environment are a serious concern for consumers and government entities. This review summarized data on innovative strategies proposed to diminish postharvest losses and extend table grape shelf life. Among physical, chemical, and biological strategies, either alone or in combination, the integrated management of fungal diseases is a sustainable alternative to synthetic fungicides. However, to date, only a few alternative technologies have succeeded on a commercial scale. Recent research aimed at increasing the competitiveness of alternative technologies has led to the development of integrated management strategies to prevent postharvest decay and increase the safety and quality of table grapes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Alternaria alternata is a common fungal pathogen causing postharvest decay in table grapes. This study addressed the potential of autochthonous yeasts and bioactive compounds of natural sources to act as biocontrol agents (BCAs) against A. alternata in cold-stored table grapes. With this purpose, 19 yeast capable of growing at 0-1 °C were isolated from the surface of Red Globe table grapes. These isolates, along with the pre-isolated strain Metschnikowia pulcherrima RCM2, were evaluated as BCAs in wounded berries. From these results, six yeast isolates were pre-selected to be combined with bioactive compounds of natural sources, like phenolic compounds (PCs) of side streams of wine industry, including bunch stem extract (BSE) (5-25 %), and cane extract (CE) (5-25 %), and functional polysaccharides from shrimp waste such as chitosan (CH) (0.5 %). Then, the biocontrol efficacy of combined treatments beyond individual ones was compared. The results revealed that 4 yeast isolates, namely M. pulcherrima RCM2 and ULA146, and Aureobasidium pullulans FUL14 and FUL18, were the most effective. However, when combined with the natural bioactive compounds, their efficacy against A. alternata did not increase significantly. Notably, ULA146 and FUL18 demonstrated a biocontrol efficacy of 36-37 %, comparable to that of the treatment with commercial doses of SO 2 , which only showed a 27 % reduction in the lesion diameter. These findings highlight the potential of using psychrotrophic yeasts as BCAs against A. alternata in cold-stored table grapes. Combining these yeast strains with BSE, CE and CH did not increase BCAs efficacy against this pathogen at the concentrations tested. The development of effective biocontrol strategies for A. alternata could contribute to reducing reliance on chemically synthesized fungicides, promoting sustainable practices, aiming to improve the quality and safety of cold-stored table grapes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The utilization of grape juice from low oenological value grape varieties for bioethanol production represent an alternative for diversification and value addition in viticulture. Optimizing Very High Gravity (VHG) fermentation can significantly increase ethanol productivity while reducing water and energy consumption. In this study, the impact of different nitrogen sources on growth and fermentative performance of locally selected yeast strains was investigated. Five yeast strains of species Saccharomyces cerevisiae and Zygosaccharomyces rouxii were cultured in both synthetic culture media and natural grape juice supplemented with ammonium sulfate (NH), yeast extract (YE), Fermaid K (FERM), and urea (U) at varying concentrations. Due to the very low fermentation rate, the Z. rouxii strain was excluded from the selection. The results obtained in synthetic medium showed that nitrogen sources that promoted growth (NH and YE) had minimal effects on fermentative performance and were highly dependent on the specific yeast strain. However, the combination of urea and ammonium favored the rate of sugar consumption. When validated in natural grape juice, urea combined with ammonium (U + NH 300 + 75 mg/L) improved both growth parameters and ethanol yield. Doubling the concentration (U + NH 600 + 150 mg/L) further enhanced sugar consumption and ethanol production while reducing unwanted by-products. The combined use of urea and ammonium exhibited a synergistic effect, making it a cost-effective nitrogen supplement for VHG fermentations., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Previous researches have showed that Lachancea thermotolerans strains RCKT4 and RCKT5 inhibited the growth of Aspergillus. However, currently, there are no data on their nutritional preferences, as a possible substrate competitor against Saccharomyces cerevisiae, and their effects on fermentation. In this work, we observed that the biocontrol yeasts and S. cerevisiae BSc203, based on the utilization of 16 carbonate sources, revealed significant differences in the nutritional profile (biocontrol yeasts NS:0·25, BSc203 NS:0·56). Lachancea thermotolerans strains did not occupy the same niche as that of BSc203 (NOI:0·44). The biocontrol agents and BSc203 presented similar competitive attitude in terms of the sugar, ethanol and sulphite tolerances. During fermentation, the biocontrol yeasts were found to tolerate up to 12% v/v ethanol, 250 mg ml -1 of total SO 2 and 30° Brix sugar. In mixed cultures, L. thermotolerans strains did not negatively affect the growth of BSc203 and the wine quality, except when RCKT4 was initially inoculated at a high proportion in the mixed culture 1MSK4 (1%BSc203/99%RCKT4), resulting in a lower production of CO 2 and ethanol, in comparison with pure BSc203. RCKT5, at a high proportion, in 1MSK5 (1%BSc203/99%RCKT5) presented promising oenological properties. This fermentation showed lower acetic acid contents and higher total acidity than pure BSc203., Significance and Impact of the Study: Generally it is not evaluated if the biofungicide yeasts sprayed on vegetables alter the quality of the fermented products. This work focused on the importance of assessing the possible effects of yeast-based fungicides used in vineyards on grape fermentation, especially on Saccharomyces cerevisiae growth. In this context, the competition between biofungicide yeasts and S. cerevisiae under winemaking conditions is investigated., (© 2018 The Society for Applied Microbiology.)

Zygosaccharomyces rouxii is the main spoilage yeast of grape juice concentrates. Detection and identification of Z. rouxii during the production of grape juice concentrate is critical to prevent spoilage in the final product. In this work, three grape juice concentrate processing plants were assessed by identifying osmophilic yeasts in juices and surfaces during different stages of a complete production line. Subsequently, molecular typing of Z. rouxii isolates was done to determine the strain distribution of this spoilage yeast. Osmotolerant yeast species, other than Z. rouxii, were mainly recovered from processing plant environments. Z. rouxii was only isolated from surface samples with grape juice remains. Z. rouxii was largely isolated from grape juice samples with some degree of concentration. Storage of grape juice pre-concentrate and concentrate allowed an increase in the Z. rouxii population. A widely distributed dominant molecular Z. rouxii pattern was found in samples from all three processing plants, suggesting resident microbes inside the plant., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Mycotoxins including aflatoxins, deoxynivalenol, fumonisins and ochratoxin A are among the main fungal secondary metabolites detected as natural contaminants in South America in different commodities such as peanuts (aflatoxins), cereals (deoxynivalenol and fumonisins) or grapes (ochratoxin A). Different strategies including crop rotation, tillage practices, fungicide application and planting less susceptible cultivars are used in order to reduce the impact of these mycotoxins in both food and feed chains. The development of fungicide resistance in many fungal pathogens as well as rising of public concern on the risks associated with pesticide use led to the search for alternative environmentally friendly methods. Biological control of plant pathogens and toxigenic fungi offers an alternative that can complement chemical control in the frame of an integrated pest management to reduce the impact of mycotoxins in the food and feed chains. The advances made in Argentina on reducing the impact of toxigenic fungi and mycotoxins in peanut, grapes and cereals using the biocontrol strategy are summarised. Native bacteria, yeasts and filamentous fungi have been selected to evaluate them as potential biocontrol agents. Field trials showed that Bacillus subtilis RC 218 and Brevibacillus sp. RC 263 were effective at reducing deoxynivalenol accumulation in wheat. The application of Clonostachys rosea isolates on wheat stubble reduced Fusarium colonisation on the stubble. Bacillus amyloliquefaciens and Microbacterium oleovorans showed good activity to control both Fusarium verticillioides growth and the accumulation of fumonisins at pre-harvest stage in maize. Control of toxigenic Aspergillus flavus and aflatoxin accumulation in peanuts was achieved using a native atoxigenic Aspergillus flavus strain based on competitive exclusion of the toxigenic strains. Kluyveromyces thermotolerans strains were used as biocontrol agents to reduce the impact of Aspergillus section Nigri and ochratoxin A accumulation in grapes.

Aspergillus section Nigri are described as the main source of ochratoxin A (OTA) contamination in grapes and wine worldwide. The knowledge of the factors affecting grape contamination by species included in this section and OTA production is essential to be able to reduce their presence, not only to improve wine quality, but also to maintain their safety. Therefore, the aims of this study were to determine the incidence of Aspergillus section Nigri species harvested in different grape-growing regions from Argentina, their ability to produce OTA, to correlate with meteorological conditions and geographical coordinates with their prevalence and to evaluate the OTA natural occurrence in grapes and wines. The morphological identification showed that Aspergillus niger aggregate species were the most prevalent ones, followed by Aspergillus carbonarius and Aspergillus uniseriate. These populations were confirmed through using AFLP markers and sequencing and, Aspergillus tubingensis was separated from A. niger aggregate. Climatic factors, altitude, longitude and latitude have influenced on the distribution of species included in the section. A. carbonarius and A. niger were OTA producers but differed in their OTA producing ability. Temperature was the factor which influenced the most over the highest incidence of A. carbonarius in La Rioja and San Juan regions. The trellis system in vineyards and drip irrigation also influenced the species isolation. The OTA levels detected in grapes and wines were low, but grape variety was more important in susceptibility to fungal infection and OTA levels., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Ochratoxin A (OTA) is a mycotoxin commonly present in cereals, grapes, coffee, spices, and cocoa. Even though the main objective of the food and feed chain processors and distributors is to avoid the extended contamination of plant-derived foods and animal feeds with mycotoxins, until now, complete OTA removal from foods and feedstuffs is not feasible. Prevention through pre-harvest management is the best method for controlling mycotoxin contamination. However, in the case that the contamination occurs after this stage, the hazards associated with OTA must be managed through post-harvest strategies. Due to the increasing number of fungal strains resistant to chemical fungicides and the impact of these pesticides on the environment and human health, maximum levels of chemical residues have been regulated in many products. Alternative methods are necessary to substitute or complement treatments with fungicides to control fungi under field or storage conditions. Yeasts are considered one of the most potent biocontrol agents due to their biology and non-toxic properties. Epiphytic yeasts are the major component of the microbial community on the surface of grape berries and they are evolutionarily adapted to this ecological niche. Nowadays, several yeast species included in different genera are considered as potential biocontrol agents to control both, growth of ochratoxigenic Aspergillus species and OTA accumulation.

Aim:   To maximize biomass production of an ochratoxigenic mould-controlling strain of Lachancea thermotolerans employing response surface methodology (RSM)., Methods and Results:   Using Plackett-Burman screening designs (PBSD) and central composite designs (CCD), an optimized culture medium containing (g l(-1) ): fermentable sugars (FS), 139·2, provided by sugar cane molasses (CMz), (NH(4) )(2) HPO(4) (DAP), 9·0, and yeast extract (YE), 2·5, was formulated. Maximal cell concentration obtained after 24 h at 28°C was 24·2 g l(-1) cell dry weight (CDW). The mathematical model obtained was validated in experiments performed in shaken-flask cultures and also in aerated bioreactors. Maximum yield and productivity values achieved were, respectively, of 0·23 g CDW/g FS in a medium containing (g l(-1) ): FS, 87·0; DAP, 7·0; YE, 1·0; and of 0·96 g CDW l(-1) h(-1) in a medium containing (g l(-1) ): FS, 150·8 plus DAP, 6·9., Conclusions:   Optimized culture conditions for maximizing yeast biomass production determined in flask cultures were applicable at a larger scale. The highest yield values were attained in media containing relatively low-CMz concentrations supplemented with DAP and YE. Yeast extract would not be necessary if higher productivity is the aim., Significance and Impact of the Study:   Cells of L. thermotolerans produced aerobically could be sustainably produced in a medium just containing cheap carbon, nitrogen and phosphorus sources. Response surface methodology allowed the fine-tuning of cultural conditions., (© 2012 The Authors. Letters in Applied Microbiology © 2012 The Society for Applied Microbiology.)

The efficacy of two strains of Kluyveromyces thermotolerans in preventing the growth and ochratoxin A (OTA) accumulation of ochratoxigenic fungi both "in vitro" and "in situ" was evaluated. The data from this study showed that both yeast strains were able to control Aspergillus carbonarius and A. niger aggregate species growth and ochratoxin A accumulation. The inhibitory effects were dependent on the ochratoxigenic species, yeast strains, a(w) and temperature evaluated and their interactions. Over all conditions assayed, ochratoxin A accumulation was reduced from 3% to 100% and the growth rate from 11% to 82.5%, depending on conditions. These results are promising for future development of a bio-pesticide., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In this study, ochratoxin A (OTA) occurrence in Argentinean musts, wines and dried vine fruits was evaluated, alongside with the performance of OchraStar(TM) columns for OTA extraction. In all the three matrices analyzed, the OchraStar(TM) columns showed good performance. The analysis of natural occurrence of OTA in the red must and the red wine samples showed low incidence with low levels of mean OTA contamination (0.12 ng/mL and 0.37 ng/mL, respectively), while 60% of the dried vine fruit samples were contaminated with OTA, in levels ranging from 0.26 to 20.28 ng/g.

Aim: The aim of this work was to evaluate the effect of Planococcus ficus infection in red wine grapes on Aspergillus section Nigri and ochratoxin A (OTA) contamination., Methods and Results: During 2006/2007 and 2008/2009 vintages, Merlot, Malbec and Cabernet Sauvignon varieties divided into two categories of grape samples (undamaged and damaged by P. ficus) were evaluated. Regardless of the grape variety and the harvest season evaluated, Aspergillus section Nigri incidence and the mean OTA concentration in damaged berries were significantly higher than that in the undamaged ones (P < 0.05; P < 0.001). The Merlot variety showed the highest level of black aspergilli contamination in damaged grapes during the 2006/2007 vintage (53.5% of infection), whereas Malbec presented the highest incidence during the 2008/2009 vintage (57.6% of infection). The Cabernet Sauvignon variety showed the highest OTA levels, ranging from 0.1 to 140 microg kg(-1)., Conclusions: The presence of P. ficus in vineyards increased the risk of OTA occurrence in grapes, suggesting the need to implement insect control at preharvest stage to reduce the entry of OTA in the wine production chain., Significance and Impact of the Study: This study is the first report on the influence of P. ficus on the potential risk of OTA contamination in grapes.

Vineyards located in eight grape growing regions of Argentina during the harvest season 2006/07 were evaluated. The aims of this study were to determine the incidence of Aspergillus section Nigri, their ability to produce ochratoxin A (OTA) and to evaluate the OTA natural occurrence in grapes. Bunches of grapes at maturation stage were collected, and grapes (50 per sample) were plated on Petri dishes containing dichloran-glycerol 18% agar (DG18) and dichloran-rose bengal-chloramphenicol agar (DRBC) media. After an incubation period of 7 days at 25 degrees C, the mycoflora belonging to Aspergillus section Nigri was identified. OTA occurrence and the toxicogenic ability of the strains were analyzed by HPLC. A. niger aggregate strains were dominant showing the highest infection percentage (81%), followed by A. carbonarius (11%) and Aspergillus uniseriate (8%). A. carbonarius strains presented the highest percentage of OTA-producer strains (82%) and the highest toxin levels (mean 202 ng/g). A positive correlation between the isolation percentage of A. carbonarius in grapes and temperature was found. The warmest regions showed the highest A. carbonarius incidence. OTA was detected at low levels in grapes during the survey. OTA levels in grapes and rain at harvest time correlated positively.

The aim of this work was to evaluate the fate of ochratoxin A (OTA) content from must to wine during the red wine making process in a pilot scale vinification. The study was done using musts obtained from two red grape varieties (Bonarda and Tempranillo) artificially contaminated with two OTA levels. A duplicate set of tanks of 100 I each was established for each must (Bonarda and Tempranillo). The fermentations were initiated by inoculation of two Saccharomyces spp. strains having different fermentation performance. The must from the Tempranillo variety was spiked with 6 microg/I of OTA while that from the Bonarda variety with 0.3 microg/I of the toxin. Samples were collected at different stages of the process. Performance of the alcoholic and malolactic fermentations was monitored. Titratable and volatile acidity, pH, ethanol, sugar and SO2 concentrations were determined following standard methods proposed by the Office International de la Vigne et du Vin (OIV). OTA analysis was done by HPLC. Detection and quantification limits were 0.01 and 0.1 ng/ml, respectively. The OTA levels during the vinification trials dropped to an average of about 86.5%. The type of Saccharomyces strains used showed no effect on toxin reduction.

Peanut is an important food commodity in Argentina. Last year Córdoba Province accounted for approximately 96% of the total Argentinian production. Few surveys of peanuts for the natural occurrence of ochratoxins and ochratoxin-producing fungi have been reported. The objectives of this study were to investigate the occurrence of Aspergillus section Nigri and ochratoxin A (OTA) in storage peanuts during a three-month-period. The capacity to produce OTA by Aspergillus section Nigri was also studied. A total of 100 samples were collected from May to July 2004. The frequency of contaminating fungi were determined by surface-disinfection the seeds and plating onto several agar types. Detection of OTA in seed samples was performed using an HPLC method. Strains belonging to Aspergillus section Nigri or Flavi were detected in all seeds samples. From the section Nigri, the species belonging to A. niger aggregate were isolated in 100% of the samples. The main ochratoxigenic specie, A. carbonarius, was present at low levels throughout the study period. OTA was found in 50% of the peanut samples, with mean levels ranging from 5.6 to 130 ng g(-1). The mean value of OTA obtained after the first month of storage (30 ng g(-1)) was significantly higher from those obtained after the second (6.5 ng g(-1)) and third (13 ng g(-1)) month (p<0.0001). One hundred and four (32%) of 322 strains of Aspergillus section Nigri, were OTA producers. The levels of toxin produced ranged from 2 to 24 ng ml(-1) of culture medium (mean level: 12.7 ng ml(-1)). These results indicate that humans and animals being may be frequently exposed to OTA in Argentina through the ingestion of peanut seed and foods based on peanuts. The presence of this toxin in peanuts might be an appropriate focus for future studies to estimate exposure through normal consumption of this commodity. These data are important in formulating guidelines for quality control of peanuts in Argentina.

The evolution of contamination with Aspergillus section Nigri and ochratoxin A occurrence was evaluated in four vineyards located at Mendoza province, Argentina during 2003-2004. The survey included two grape varieties, one of late maturation (Bonarda) and the other of early maturation (Tempranillo). The vineyards were set under non-organic and organic cropping systems. Bunches of grapes at different growth stages were collected, and berries (50 by sample) were plated on Petri dishes containing Dichloran 18% Glycerol Agar (DG18) and Dichloran Rose Bengal Chloramphenicol Agar (DRBC) media. After an incubation period of 7 days at 25 degrees C+/-1 degrees C, the mycoflora belonging to Aspergillus section Nigri was identified. The ability to produce ochratoxin A (OTA) by the potential ochratoxigenic species was evaluated on YES (2% yeast extract, 15% sucrose) medium. The cultures were incubated at 30 degrees C+/-1 degrees C for 10 days in darkness. The OTA content of the grapes was determined by HPLC. Through the different growth stages, from setting to harvest, grape contamination by the Aspergillus species, section Nigri increased. The main species isolated belonged to the A. niger aggregate. From 246 strains evaluated 24% was ochratoxigenic. OTA was not detected in grapes during the survey.