The presence and metabolic activity of psychrotrophic microorganisms in milk and dairy products are reviewed. Problems involved in adequately defining the microorganisms and temperatures of growth are discussed. The sources and incidences of psychrotrophs in milk and dairy products and methods to control these microorganisms are presented. Methods ranging from simple plate counting techniques to detection of metabolites produced by the psychrotrophs are reviewed. Alterations of protein, lipid and carbohydrate fractions of milk and their effects on the keeping quality of milk and dairy products are discussed. Finally, additional research areas are suggested.

The genus Fusarium comprises a diverse group of fungi including several species that produce mycotoxins in food commodities. In this study, a multiplex polymerase chain reaction (PCR) assay was developed for the group-specific detection of fumonisin-producing and trichothecene-producing species of Fusarium. Primers for genus-level recognition of Fusarium spp. were designed from the internal transcribed spacer regions (ITS1 and ITS2) of rDNA. Primers for group-specific detection were designed from the TRI6 gene involved in trichothecene biosynthesis and the FUM5 gene involved in fumonisin biosynthesis. Primer specificity was determined by testing for cross-reactivity against purified genomic DNA from 43 fungal species representing 14 genera, including 9 Aspergillus spp., 9 Fusarium spp., and 10 Penicillium spp. With purified genomic DNA as a template, genus-specific recognition was observed at 10 pg per reaction; group-specific recognition occurred at 100 pg of template per reaction for the trichothecene producer Fusarium graminearum and at 1 ng of template per reaction for the fumonisin producer Fusarium verticillioides. For the application of the PCR assay, a protocol was developed to isolate fungal DNA from cornmeal. The detection of F. graminearum and its differentiation from F. verticillioides were accomplished prior to visible fungal growth at <10(5) CFU/g of cornmeal. This level of detection is comparable to those of other methods such as enzyme-linked immunosorbent assay, and the assay described here can be used in the food industry's effort to monitor quality and safety.

Fourier transform‐infrared spectroscopy (FT‐IR) methods enable chemical discrimination of intact bacterial cells and produce complex whole‐organism biochemical fingerprints (spectra), which are reproducible and distinct for different bacteria. Numerous researchers indicate that there is great potential for using FT‐IR methods in combination with multivariate statistics (chemometrics) to detect and identify bacteria in water, culture media and foods. This article presents a review of the FT‐IR techniques, sample preparation procedures and experimental conditions used in these studies, as well as advantages, disadvantages and challenges that remain for the development of FT‐IR detection methods.

Some species of Fusarium can produce mycotoxins during food processing procedures that facilitate fungal growth, such as the malting of barley. The objectives of this study were to develop a 5' fluorogenic (Taqman) real-time PCR assay for group-specific detection of trichothecene- and fumonisin-producing Fusarium spp. and to identify Fusarium graminearum and Fusarium verticillioides in field-collected barley and corn samples. Primers and probes were designed from genes involved in mycotoxin biosynthesis (TRI6 and FUM1), and for a genus-specific internal positive control, primers and a probe were designed from Fusarium rDNA sequences. Real-time PCR conditions were optimized for amplification of the three products in a single reaction format. The specificity of the assay was confirmed by testing 9 Fusarium spp. and 33 non-Fusarium fungal species. With serial dilutions of purified genomic DNA from F. verticillioides, F. graminearum, or both as the template, the detection limit of the assay was 5 pg of genomic DNA per reaction. The three products were detectable over four orders of magnitude of template concentration (5 pg to 5 ng of genomic DNA per reaction); at 50 ng template per reaction, only the TRI6 and FUM1 PCR products were detected. Barley and corn samples were evaluated for the presence of Fusarium spp. with traditional microbiological methods and with the real-time PCR assay. The 20 barley samples and 1 corn sample that contained F. graminearum by traditional methods of analysis tested positive for the TRI6 and internal transcribed spacer (ITS) PCR products. The five corn samples that tested positive for F. verticillioides by traditional methods also were positive for the FUMI and ITS PCR products. These results indicate that the described multiplex real-time PCR assay provides sensitive and accurate differential detection of fumonisin- and trichothecene-producing groups of Fusarium spp. in complex matrices.

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