A method for the determination of phytol enantiomers in plant-based dairy products was established by gas chromatography-mass spectrometry (GC-MS). The pretreatment process was optimized, and the figures of merit of the proposed method such as linear relationship, precision, spiked recovery, limit of detection (LOD) and limit of quantitation (LOQ) were investigated. Results showed that in the concentration range of 0.0–1.0 μg/mL, the linearity of the method was good (r > 0.999). The LODs of E- and Z-phytanol were 0.03 and 0.04 mg/kg, respectively, and the respective LOQs were 0.09 and 0.10 mg/kg. The recoveries of E- and Z-phytanol in spiked samples were 78.6%–93.5% and 79.5%–94.7%, respectively with relative standard deviations (RSDs) less than 10%. This method is sensitive, accurate and repeatable, and can be used for the determination of phytol enantiomers in plant-based dairy products.

An analytical method for the determination of ethyl carbamate in fermented milk was established by gas chromatography-mass spectrometry (GC-MS). Sample pretreatment conditions were optimized. The analytical figures of merit of the proposed method including linear relationship, precision, spiked recovery, detection limit and quantitation limit were evaluated. Ethyl carbamate was quantitated using an external standard. The linearity of this method was good in the range of 0–200 ng/mL (r > 0.999), and the detection limit and quantitation limit of ethyl carbamate were 2.0 and 5.0 μg/kg, respectively. The recovery of the added ethyl carbamate ranged from 89.9% to 105.2%, with relative standard deviation (RSD) less than 10%. This method is sensitive, accurate and repeatable, and can meet the requirements for the determination of ethyl carbamate in fermented milk.

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.

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%.