The monosaccharide composition and antioxidant activity of extracellular polysaccharides from Lactobacillus plantarum were analyzed. Crude polysaccharides were obtained from the fermentation broth of Lactobacillus plantarum by water extraction and alcohol precipitation and were fractionated into two fractions (DZ-1 and DZ-2) by DEAE-52 cellulose column chromatography. The monosaccharide components of DZ-1 and DZ-2 were analyzed by gas chromatography, and their antioxidant activity was tested using 1,1-diphenyl-2-picrylhy drazyl (DPPH), hydroxyl radical, and 2,2’-diazo bis-3-ethyl benzothiazoline-6-sulfonic acid (ABTS) cation radical scavenging assays. DZ-1 was a homopolysaccharide composed of only glucose units, while DZ-2 was a heteropolysaccharide composed of arabinose and galactose with a content ratio of 46.03:53.89. Both DZ-1 and DZ-2 had the ability to scavenge DPPH, hydroxyl and ABTS cation radicals.

To quickly and accurately evaluate the risk of ochratoxin A (OTA) pollution in dairy products, a method to detect fungi capable of producing OTA in dairy products was developed using gene probe scanning technology. According to the elucidated biosynthesis pathway of OTA, the halogenase gene related to OTA production was selected to design degenerate primers to establish a polymerase chain reaction (PCR) method for the detection of OTA-producing fungi. One OTAproducing strain (Aspergillus ochraceus) and five strains not able to produce OTA (Aspergillus cristatus, Aspergillus flavus, Fusarium moniliforme, Issatchenkia terricola, and Saccharomyces cerevisiae) were selected to test the PCR method. It was found that DNA from the OTA-producing strain but not the non-OTA producers could be amplified by PCR. Moreover, this method had high accuracy and sensitivity for detecting polluted dairy products.

A high performance liquid chromatography (HPLC) method was established for the simultaneous determination of the contents of three fumonisins in infant formula. Under optimized experimental conditions, the fumonisins were quantified by an external standard method. The analytical figures of merit such as linear relationship, recovery, precision, limit of detection and limit of quantitation of the method were examined. The results showed that the linearity of the method was good in a certain concentration range (r > 0.999). The detection limits of fumonisin B1, B2 and B3 were 10, 5, and 5 μg/kg, respectively. The limits of quantitation were 30, 15 and 15 μg/kg, respectively. The average recoveries of the fumonisins were 91.6% –95.7%, 89.5%–94.4% and 88.6%–92.3% at three different spiked levels, respectively, and the relative standard deviations (RSDs) for precision were less than 10%.