Modelling the effect of temperature and water activity on the growth of two ochratoxigenic strains of Aspergillus carbonarius from Greek wine grapes

The aim of this study was to determine the effects of water activity (aw; 0.85 to 0.98) and temperature (10 to 40°C) on the radial growth rate and ochratoxin A (OA) production of two Aspergillus carbonarius isolates in vitro. The isolates were obtained from wine grapes cultivated in Greece, and the trial was conducted with a synthetic grape juice medium similar in composition to grapes between veraison (beginning of color change) and ripeness. Fungal growth and OA production data were collected for 55 days. Response surface curves and cardinal values for aw and temperature were obtained using multiple regression analysis. The lag phase lasted from less than 1 to 10 days. Both isolates grew optimally at 30 to 35°C and 0.96 aw, but maximum OA production occurred under suboptimal growth conditions (15 to 20°C and 0.93 to 0.96 aw). Growth also was observed at 0.85 aw and 25°C, however at this same aw the fungus failed to produce mycelium at any other temperatures tested. The isolates produced OA at 15 to 30°C and 0.90 to 0.98 aw. Maximum OA production was detected after 25 days of incubation at 20°C and 0.96 aw and was 3.14 and 2.67 μgg−1, respectively, for the two strains. The isolated strains used in this study were more xerotolerant than others from the Mediterranean basin. These data will allow producers to identify and thus monitor critical environmental conditions effectively in wine grapes. These data also increase the knowledge base concerning the ability of A. carbonarius to grow and produce toxin under different ecological conditions and can contribute to the development of secondary models for the prediction and risk assessment of OA in wine production.

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Effect of Temperature, Water Activity, and pH on Growth and Production of Ochratoxin A by Aspergillus niger and Aspergillus carbonarius from Brazilian Grapes

Journal of Food Protection ◽

10.4315/0362-028x.jfp-13-495 ◽

2014 ◽

Vol 77 (11) ◽

pp. 1947-1952 ◽

Cited By ~ 32

Author(s):

FABIANA REINIS FRANCA PASSAMANI ◽

THAIS HERNANDES ◽

NOELLY ALVES LOPES ◽

SABRINA CARVALHO BASTOS ◽

WILDER DOUGLAS SANTIAGO ◽

...

Keyword(s):

Aspergillus Niger ◽

Ochratoxin A ◽

Water Activity ◽

Fungal Growth ◽

Grape Juice ◽

Effect Of Temperature ◽

Aspergillus Carbonarius ◽

Optimal Conditions ◽

Wide Range ◽

Temperature Water

The growth of ochratoxigenic fungus and the presence of ochratoxin A (OTA) in grapes and their derivatives can be caused by a wide range of physical, chemical, and biological factors. The determination of interactions between these factors and fungal species from different climatic regions is important in designing models for minimizing the risk of OTA in wine and grape juice. This study evaluated the influence of temperature, water activity (aw), and pH on the development and production of OTA in a semisynthetic grape culture medium by Aspergillus carbonarius and Aspergillus niger strains. To analyze the growth conditions and production of OTA, an experimental design was conducted using response surface methodology as a tool to assess the effects of these abiotic variables on fungal behavior. A. carbonarius showed the highest growth at temperatures from 20 to 33°C, aw between 0.95 and 0.98, and pH levels between 5 and 6.5. Similarly, for A. niger, temperatures between 24 and 37°C, aw greater than 0.95, and pH levels between 4 and 6.5 were optimal. The greatest toxin concentrations for A. carbonarius and A. niger (10 μg/g and 7.0 μg/g, respectively) were found at 15°C, aw 0.99, and pH 5.35. The lowest pH was found to contribute to greater OTA production. These results show that the evaluated fungi are able to grow and produce OTA in a wide range of temperature, aw, and pH. However, the optimal conditions for toxin production are generally different from those optimal for fungal growth. The knowledge of optimal conditions for fungal growth and production of OTA, and of the stages of cultivation in which these conditions are optimal, allows a more precise assessment of the potential risk to health from consumption of products derived from grapes.

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Development of a model describing the effect of temperature, water activity and (gel) structure on growth and ochratoxin A production by Aspergillus carbonarius in vitro and evaluation in food matrices of different viscosity

Food Microbiology ◽

10.1016/j.fm.2010.06.001 ◽

2011 ◽

Vol 28 (4) ◽

pp. 727-735 ◽

Cited By ~ 18

Author(s):

Anastasia E. Kapetanakou ◽

Anna Ampavi ◽

Stavrianos Yanniotis ◽

Eleftherios H. Drosinos ◽

Panagiotis N. Skandamis

Keyword(s):

Ochratoxin A ◽

Water Activity ◽

Effect Of Temperature ◽

Aspergillus Carbonarius ◽

Gel Structure ◽

Food Matrices ◽

Temperature Water

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Effect of temperature and water activity on growth and ochratoxin A production by Australian Aspergillus carbonarius and A. niger isolates on a simulated grape juice medium

International Journal of Food Microbiology ◽

10.1016/j.ijfoodmicro.2006.04.005 ◽

2006 ◽

Vol 110 (3) ◽

pp. 209-216 ◽

Cited By ~ 66

Author(s):

Su-lin L. Leong ◽

Ailsa D. Hocking ◽

Eileen S. Scott

Keyword(s):

Ochratoxin A ◽

Water Activity ◽

Grape Juice ◽

Effect Of Temperature ◽

Aspergillus Carbonarius

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Aspergillus carbonarius growth and ochratoxin A production on irradiated dried grapes under different water activity and temperature conditions

World Mycotoxin Journal ◽

10.3920/wmj2009.1164 ◽

2010 ◽

Vol 3 (2) ◽

pp. 175-182 ◽

Cited By ~ 12

Author(s):

A. Astoreca ◽

C. Barberis ◽

C. Magnoli ◽

A. Dalcero

Keyword(s):

Ochratoxin A ◽

Water Activity ◽

Lag Phase ◽

Human Consumption ◽

Aspergillus Carbonarius ◽

Phase Growth ◽

Wine Grapes ◽

Wine Production ◽

Dried Grapes ◽

Temperature Ranges

Grapes have different destinations. The most important in the national and international market is wine production, but another is dehydration to produce raisins. Dried vine fruits are at greater risk of ochratoxin A (OTA) contamination than wine grapes because the ratio of Aspergillus carbonarius to Aspergillus niger aggregate increases during drying. The growth of these species, and consequently OTA production, can be influenced by different environmental factors, the two most important being water activity (aW) and temperature. The objective of the present work was to evaluate the lag phase, growth rate and OTA production by two A. carbonarius isolates on irradiated dried grapes at different aW (0.910, 0.928, 0.955, 0.973 and 0.995), temperatures (15, 25 and 30 °C) and incubation times (7, 14 and 21 days). Growth was observed at all aW and temperature ranges assayed. No significant differences between the growth rates reached at 25 °C and 30 °C by both isolates were observed. At the assayed conditions, OTA production occurred over the whole range of temperatures (15-30 °C), with the maximum at 25 and 30 °C depending on the aW. In general, OTA concentration increased as aW increased with no statistically significant differences at the tested incubation times. This work provides information that can be used by companies for the purpose of preventing A. carbonarius and OTA contamination during storage on this and other substrates (e.g. dried prunes, figs and apricots) destined for human consumption.

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