###### Abstract
For this reason, to protect consumer health, the Commission of the European Communities imposed more stringent quality requirements specifying maximum admissible mycotoxin contamination levels for cereal grain and their processing products, i.e., at 3 ug-kg\({}^{-1}\) for processed grain or for grain for direct human consumption, as well as 5 ug-kg\({}^{-1}\) for unprocessed cereal grain (Commission Regulation No. 466/2001 of 8 March 2001 with later amendments). Despite the fact that the standards of postharvest grain treatment have improved substantially, the deterioration of cereal grain quality at this first stage of food processing still remains a serious problem for producers of plant-origin raw materials. According to the Food and Agriculture Organization of the United Nations, 25-33% of world cereal crops are lost each year during storage (FAO, 2018). In view of the data, proper postharvest grain preservation and storage appear to be key stages of the production and processing chain for the safety of food products derived from it. In practice, to protect crop grain against adverse changes in its bulk, grain after harvest is usually subjected to respective preservation operations consisting in the effective reduction of its moisture content (in the drying process) and then maintaining it at a safe level. One of the methods to reduce excess moisture content in plant raw materials is high-temperature drying, i.e., ventilation with heated air. This approach, within a relatively short time, protects grain against spoilage. However, on the other hand, it introduces a risk of its quality deterioration (e.g., reduction of germination capacity and energy or degradation of labile nutrients), resulting from the application of high temperature [12]. The detrimental effects of high temperatures mean that not all raw materials can be preserved by this method. In view of specific requirements for malting barley resulting from the need to retain high grain germination capacity and energy [1], near-ambient drying (in which unheated air is the drying agent [13]) seems to be better for its postharvest treatment. This preservation method ensures mild drying conditions and, thus, low energy consumption. However, on the other hand, in temperate climates (as in most countries of Central and northern Europe, as well as agricultural regions in Canada and the USA), due to the relatively low drying potential of air determined by weather conditions, this process is long term and may last from several to over a dozen days [13; 14; 15]. As a result, in the course of near-ambient drying for a relatively long time, the moisture content of barley grain found in the upper layer of the silo is close to its initial value, which poses a risk of mold growth in the bulk of preserved raw materials. Hence,this grain preservation method, despite its advantages, requires continuous monitoring, particularly in terms of the activity of mycobiota inhabiting the grain. In the practice of storing raw plant materials, new, effective, and rapid methods involving tools based on near infrared spectroscopy (NIR) [16] or the e-nose technique [9; 17] are being investigated to monitor the microbiological status of grain. The proposed solutions provide promising results. However, their applicability is limited to the detection of fungi that are already present in the grain mass. Meanwhile, universal, simple, and rapid solutions are more needed, enabling producers to estimate the hazard related to fungal growth in advance and, thus, undertake preemptive actions to protect the grain mass against contamination with mycoflora and the formation of mycotoxins. The answer to this demand can be provided by predictive models that would facilitate the assessment of threats related to the deterioration of plant material quality, and it might be applied as elements supporting decision-making processes in advanced management systems for postharvest grain preservation.