Development of loop-mediated isothermal amplification assay for rapid screening of fungal contamination in pepper and paprika powder

Abstract

Fungi cause hazards such as mildew, spoilage, and mycotoxins, so the Chinese government has formulated maximum level limits (MLs) for fungi in spices. However, the current standard culture-based detection method is timeconsuming (5-7 days) and unsuitable for the rapid on-site screening of fungal contamination to facilitate immediate control measures. Therefore, we developed a loop-mediated isothermal amplification (LAMP) assay for the rapid (<4 h) screening of fungi at levels greater than or equal to those of Chinese MLs (104 cfu/g) in spices, without requiring any expensive instruments. Contaminated samples could be identified based on colour change that was visible to the naked eye. The specificity based on spiked sample experiments and comparisons with the traditional culture-based method demonstrated that this LAMP method could be applicable to the on-site testing of pepper and paprika powder samples, and it could also be used by laymen. Furthermore, this method could be applied to the rapid screening of fungal contamination in other spices, foods and feeds. In addition, Tween-20 was included in the assay to enhance the collection of fungus from sample suspensions.