Modelling the Radial Growth of Geotrichum candidum: Effects of Temperature and Water Activity

Abstract

Modelling the growth of microorganisms in relation to environmental factors provides quantitative knowledge that can be used to predict their behaviour in foods. For this reason, the effects of temperature and water activity (aw) adjusted with NaCl on the surface growth of two isolates and one culture strain of Geotrichum candidum were studied. A dataset of growth parameters obtained from almost 600 growth curves was employed for secondary modelling with cardinal models (CMs). The theoretical minimal temperature resulting from the modelling of the mycelium proliferation rate ranged from −5.2 to −0.4 °C. Optimal and maximal temperatures were calculated and found to have narrow ranges of 25.4 to 28.0 °C and 34.2 to 37.6 °C, respectively. Cardinal aw values associated with radial growth (awmin from 0.948–0.960 and awopt from 0.992–0.993) confirmed the salt sensitivity of the species. Model goodness-of-fit was evaluated by the coefficient of determination R2, which ranged from 0.954 to 0.985, and RMSE, which ranged from 0.28 to 0.42. Substantially higher variability accompanied the lag time for growth modelling than the radial growth rate modelling despite the square root transformation of the reciprocal lag phase data (R2 = 0.685 to 0.808). Nevertheless, the findings demonstrate that the outputs of growth modelling can be applied to the quantitative evaluation of the roles of G. candidum in fresh cheese spoilage as well as the ripening of Camembert-type cheeses or various artisanal cheeses. Along with validation, the interactions with lactic acid bacteria can be included to improve the predictions of G. candidum in the future.

Quantitative Characterization of Geotrichum candidum Growth in Milk

“…These results indicate the slower growth of G. candidum at 1% NaCl, which is in accordance with the findings of Eliskases-Lechner et al [7] and Uraz and Özer [51]. However, strain-dependent sensitivity of G. candidum on salt concentration should also generally be considered [2,4,44]. T min -minimum temperature (theoretical value); T opt -optimal temperature; T max -maximum temperature; 1/λ opt -reciprocal lag phase duration at the optimal temperature; µ opt -maximum specific growth rate at the optimal temperature; CM 1/λ -cardinal model applied to its lag phase data; CM µ -cardinal model applied to its specific growth rate.…”

Ginger and parsley essential oils: chemical composition, antimicrobial activity, and evaluation of their application in cheese preservation

“…Antifungal activity of both EOs was also detected against G. candidum and P. roqueforti, which, if on one hand are used as starter cultures in many blue, semi-fresh, soft and semi-hard cheeses, on the other, they can also spoil food and feed (Flórez et al 2007). The occurrence of G. candidum in certain dairy products such as butter, cream and fresh cheese is undesirable and can determine spoilage (Koňuchová and Valík 2021) as well as certain strains of P. roqueforti which can contaminate silages (Boysen et al 2000). In detail, against P. roqueforti, EO-P showed intermediate antifungal activity at 2 % and weak at 1 % while EO-G had an intermediate antifungal activity at 2 % and weak both at 1 % and 0.5 %.…”

Modelling the Effect of Temperature on the Initial Decline during the Lag Phase of Geotrichum candidum

“…This fungus positively affects appearance, texture, taste and aroma of cheeses, due to its metabolic activity [4][5][6]. On the other hand, G. candidum is also considered as a frequent spoilage organism [7][8][9][10]. If G. candidum is present in excessive quantities on the surface of raw soft-ripened cheeses, (camembert type), it is considered to be responsible for many defects, such as unstable or slippery rind and unequal covering of the cheese surface [7,8,11].…”

“…If G. candidum is present in excessive quantities on the surface of raw soft-ripened cheeses, (camembert type), it is considered to be responsible for many defects, such as unstable or slippery rind and unequal covering of the cheese surface [7,8,11]. In addition, G. candidum can cause degradation of milk fat and protein which results in creating undesirable cheese organoleptic properties and appearance [6,10,12]. In terms of shelf life and the microbial Appl.…”

“…This ascomycetous yeast can grow in a wide range of environmental conditions, notably temperature and pH values. G. candidum can grow in the temperature range from 5 to 38 • C, but its optimum growth temperature is around 25-30 • C [7,10,13,14]. Although it remains active over a wide pH interval (pH 3.0-11.5), its growth is stimulated by an acidic environment (pH 5.0-5.5).…”