Mould Growth Models Research Articles

Risk Assessment of Mycotoxins and Predictive Mycology in Sri Lankan Spices: Chilli and Pepper

This research contributes to a better understanding of the mycotoxin problem associated with two important spices in world trade;, chilli and pepper by a multidisciplinary approach including analytical chemistry, risk assessment, food chemistry and predictive mycology. More specifically, this work provides important insights in mycotoxin contamination of these spices and associated risks in Sri Lanka. Firstly, a simple extraction method based on the QuEChERS approach was developed and successfully validated for the simultaneous determination of multiple mycotoxins using an advanced chromatographic technique, LC-MS/MS. The method was applied on complex spices for quantitative screening of seventeen mycotoxins. In addition to the classical aflatoxins and ochratoxin A, the spices were also found to be contaminated with several other toxicologically significant mycotoxins. Chilli samples (87%) were more frequently contaminated with mycotoxins than peppers (65%). Subsequently, the mycotoxins screening results and the collected consumption data were integrated in a quantitative risk assessment study. The results showed that AFB1 exposure via chilli consumption is of a public health concern in Sri Lanka, pepper is of lesser extent a risk due to the lower consumption. The toxigenic mould characterization in black peppers showed that Aspergillus flavus and/or Aspergillus parasiticus were the predominant moulds (73%) found, with considerable contamination (60%) of Penicillium spp. and A. niger. Furthermore, predictive mould growth models on peppercorns were developed at three temperatures and seven water activity levels for both A. flavus and A. parasiticus isolates. Based on the research, suitable storage conditions for black peppercorns were suggested and the way forward in managing the risk towards mycotoxins posed by the consumption of these two spices in Sri Lanka.

The Role of Transient Wetting on Mould Growth on Wooden Claddings

Mold growth on the surface of wooden façades is usually dealt with by using surface treatment such as paint with fungicides. However, new developments in architecture are moving towards less use of coating, and more use of untreated wooden claddings. Mould growth is well understood and described, and several models for predicting mould growth on building materials exist. It is commonly known that mould growth is directly controlled by the climate which the wood is exposed to. Several authors identify humidity, temperature and time as the main drivers of mould growth. However, most of the current growth models developed are based on laboratory measurements at stable climatic conditions. Consequently, these models are less suitable for prediction of mould growth on exterior surfaces exposed to rapidly changing weather conditions. This paper analyses the effect of variations of meteorological data on the mould growth on wooden claddings. An experimental setup of wood samples was exposed to outdoor conditions and hourly weather conditions as well as the mould growth at different intervals were measured. The measurements were supplied with 1-D Heat And Moisture (HAM) simulations to provide a more accurate estimate of the conditions on the surface of the samples. The purpose of the analysis was to evaluate if an existing mould growth model might be applicable also for predicting outdoor mould growth. Several profiles of temperature and moisture were continuously monitored on different locations of an eight-story building made from Cross Laminated Timber (CLT). The results from the analysis of the samples of wood cladding were used to model the mould growth on different locations of the building. Also the drying effect of wind around the building was studied. The study shows that there is large variation of potential mould growth on the façade of the building.

Assessment of hygrothermal performance and mould growth risk in ventilated attics in respect to possible climate changes in Sweden

Most of the last 20 years in Sweden have been mild and wet compared to the 1961–1990 climate reference period. After a few relatively cold years in the mid-1980s, practically all years have been warmer than the preceding 30 years average. During the indicated period, an increase of moisture-related problems (mould growth) was observed in ventilated attics, a moisture sensitive building part.This work investigates hygrothermal performance of ventilated attics in respect to possible climate change. Hygrothermal simulations of attics were performed numerically in Matlab. Four attic constructions are investigated – a conventional attic and three alternative constructions suggested by practitioners. Simulations were done for the period of 1961–2100 using the weather data of RCA3 climate model. Effects of three different emissions scenarios are considered. Hygrothermal conditions in the attic are assessed using a mould growth model. Based on the results the highest risk of mould growth was found on the north roof of the attic in Gothenburg, Sweden. Results point to increment of the moisture problems in attics in future. Different emissions scenarios do not influence the risk of mould growth inside the attic due to compensating changes in different variables. Assessing the future performance of the four attics shows that the safe solution is to ventilate the attic mechanically, though this solution inevitably requires extra use of electrical energy for running the fan. Insulating roofs of the attic can decrease the condensation on roofs, but it cannot decrease the risk of mould growth considerably, on the wooden roof underlay.