A helicase-dependent isothermal DNA amplification (HDA) assay was developed for the rapid and accurate detection of Gluconacetobacter in yogurt.A pair of specific oligonucleotide primers according to the 16S ribosomal RNA gene (GenBank accession number:HQ677466.1) of Gluconacetobacter was designed,and the optimal concentration of UvrD helicase and T4 gp32 in the reaction system were determined.The HAD method enabled direct detection of Gluconacetobacter in yogurt.The specificity of the method was tested by amplification and electrophoresis of various strains in yoghurt using the HAD system.The amplification product by HDA was the same as the designed gene fragment (101 bp).The sensitivity of HDA was 102 CFU/g.The optimal reaction system was established by the use of 0.1 μg of UvrD helicase and 5.0 μg of T4 gp32.In conclusion,the method was sensitive and time saving.

Lactulose as a prebiotic is widely used in milk-based products, especially in infant formula as an important component. For regulation, the Chinese national standard Food Additive-Lactulose Liquid GB8816—1988 has been relatively backward. And there is no regulation regarding the analysis of lactulose in foods. How to discriminate lactulose from other carbohydrates, especially from lactose, is a problem we are faced with and an obstacle for application. The chromatographic techniques for the determination of lactulose in milk-based products, including thin-layer chromatography, gas chromatography and liquid chromatography, are summarized. This work could provide a reference for lactulose detection in milk-based product by researchers.

A gas chromatography-mass spectrometry (GC-MS) method was developed for determining β-sitosterol in milk by optimizing important sample pretreatment parameters such as saponification temperature, extraction solvent, extraction number, shaking method during extraction and rotary evaporation temperature. The feasibility of the developed method was examined. This method exhibited a wide linear range and could meet the requirements for routine quantitative analysis of β-sitosterol in milk samples with high precision, good repeatability, accurate results and high reliability.