Cold storage also to avoid mycotoxins production in Alternaria infected apple

As an apple fruit rot disease related fungus, Alternaria spp. could bring severe hazardous risk to apple fruits during postharvest storage. In this research, cold treatment is investigated for inhibition of Alternaria infection and related mycotoxins production during postharvest storage of apple. Morphology results show that cold treatment could inhibit Alternaria rot in inoculated apple samples. Alternariol Monomethyl Ether (AME), Alternariol (AOH), and Tenuazonic Acid (TEA) are the major mycotoxins during room storage temperature at 25 ?C, while only AOH is detected after 30 d at 4 ?C storage. The results revealed that room temperature could bring hazardous risk while toxic risks might still exist during cold storage. Metabolites of Alternaria mycotoxins are also identified in this work with metabolic pathways of glucose conjugation, hydrogenation reduction, oxidation, and dehydrogenation reaction. Cold storage treatment could lead to down-regulation of nature products in inoculated apples, including all five target Alternaria mycotoxins. This research proposed new insights into mycotoxins production in Alternaria infected apple during postharvest storage process, which will be benefit for better understanding of postharvest storage and safety control of fruits.The text before is the Abstract of the paper IntroductionApple is an economically important fruit tree species worldwide. The harvested apple fruits are usually stored under cold conditions to ensure a year-round supply (Zhao et al., 2020). Apple fruits are highly susceptible to fungi with phytopathogenic species infecting in the field and saprophytes at postharvest stage, which might result in economic losses. Moreover, apple fruits are highly vulnerable to fungus disease known as blackmould, produced by small-spored Alternaria spp. (Da Cruz Cabral et al., 2019). Temperature is one of the most important factors involved in postharvest storage. Usually, harvest is performed in Autumn at temperature about 25 ?C. Then, the fruits remain at room temperature for short-period household storage by consumers. For long-period post-harvested storage, apple fruits are usually stored at 4 ?C. Specially, retailing is usually performed at room temperature, while household storage is usually performed at cold temperature in fridge. Alternaria genus is a ubiquitously occurring plant saprophytic and pathogenic fungus which can cause postharvest decay, fruit damage, and plant-derived food safety (Dang et al., 2018; Pavicich, C?rdenas et al., 2020). Alternaria fungi can grow well on different substrates. After infection, these small-spored Alternaria spp. may produce a wide variety of secondary metabolites such as mycotoxins, including alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), tenuazonic acid (TeA), tentoxin (TEN), and altertoxins I, II, III (ATX-I, -II, -III) (Chen et al., 2021). Alternaria mycotoxins production in culture medium was investigated and the result revealed amounts of different mycotoxins were depended on temperature (Mannaa and Kim, 2017). Moreover, fungal infestation and mycotoxins production can occur during transported or stored of food in postharvest period (Morales et al., 2010; Peter Mshelia et al., 2020). For example, three major Alternaria mycotoxins, AME, AOH, and TeA could be produced at low temperature of 5 ?C (Pose et al., 2010). Fungal infestation in food could also occurred during transportation or storage in refrigerated environments. Contamination of Alternaria mycotoxins have been reported in different fruits previously, including apples (Pavicich, De Boevre et al., 2020), grapes (Guo et al., 2021), citrus fruits (Magnani et al., 2007), apple juice concentrates, and related products (Li, Zhang et al., 2020). Apples are highly susceptible fruits to fungal contamination (especially Alternaria species) due to high water activity, rich nutrients, and thin skin (Fontaine et al., 2021). AOH and AME are major Alternaria mycotoxins detected in apples and products (Lau et al., 2003, Pavicich and Patriarca, 2022). ATX-I and ATX-II have also been detected in apples infected by Alternaria species (Scott, 2001). Sulfate conjugates of Alternaria mycotoxins were also reported in previous study, and only trace amounts of glycosylated conjugates were monitored (Pavicich, C?rdenas et al., 2020; Soukup et al., 2016). Alternariol-3-glucoside was detected during apple concentrate products, while alternariol-3-sulfate was present both in raw materials and related process period (Mao et al., 2022, Puntscher et al., 2018). Alternaria fungi and related mycotoxins have been reported with severe toxic effects to humans and Alternaria spores are known to be biological contaminants and a potent source of aeroallergens (Hernandez-Ramirez et al., 2021). The European Food Safety Authority (EFSA) carried out a risk assessment about Alternaria mycotoxins since 2011 (EFSA, 2011). Alternaria mycotoxins were reported with genotoxicity, cytotoxicity, and reproductive toxicity (Meena and Samal, 2019). TeA was reported with acutely toxic effect effects (Kumari Tirkey, 2019), ATXs were considered as the prominent mutagen (Panigrahi, 2020), and AOH, AME, and ATXs exhibited cytotoxicity in vitro (Aichinger et al., 2021; Del Favero et al., 2018). Conjugates and metabolites of Alternaria mycotoxins were also reported with severe toxic effects as well (Dellafiora et al., 2018; Pavicich, C?rdenas et al., 2020). These conjugated mycotoxins and metabolites might be converted to free Alternaria mycotoxins in animal?s digestive tract. Thereby, the contamination of Alternaria mycotoxins and metabolites in food becomes an important public health problem. With regard to postharvest storage of apple fruits, it is important to discern storage temperature related Alternaria mycotoxins production. An essential insight into quantitation of Alternaria mycotoxins formation has been investigated for evaluation of food safety during cold and room temperature storage. Over the years, Alternaria conjugated metabolites were detected and reported in plant-derived food in previous studies (Kelman et al., 2015, Zhang et al., 2020). This work aims to illustrate cold storage temperature enhancing the resistance of Alternaria mycotoxins and metabolites production during postharvest of apple fruits, which could provide theoretical guidance for apple preservation after harvest. ? SourceNew insights into in mycotoxins production in Alternaria infected apple during postharvest storageXin Mao, Anqi Chen, Jingyao Qu, Pengjie Luo, Yanli You, Yonglin Gao, Fengguang Dong, Yongning Wu & Yanshen LiPostharvest Biology and Technology, Volume 198, April 2023, 112238https://www.sciencedirect.com/science/article/abs/pii/S0925521422004069https://doi.org/10.1016/j.postharvbio.2022.112238Picture is the graphical abstract