The histamine content in commercial fermented dairy products was determined by high performance liquid chromatography (HPLC) with precolumn derivatization. Four derivatization conditions, dosage of derivatizing agent (dansyl chloride, Dns-Cl), pH value, time and temperature were optimized using one-factor-at-a-time method and response surface methodology (RSM). The results showed that the optimized derivatization conditions were easy to manipulate and allowed for efficient, accurate and precise determination of histamine. The method met the requirements for accurate determination of histamine dairy products.

The major free middle-chain fatty acids (hexanoic acid, octanoic acid, decanoic acid) in raw milk and dairy products are regarded as important compounds that affect liquid milk quality and safety due to their strong flavor characteristics. This article provides an analytical method using headspace solid phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) with an internal standard for the quantitative determination of free middle-chain fatty acids in liquid milk. The method was verified as an approach with high accuracy, simple operation and high extraction efficiency.

Milk fermented by Leuconostoc mesenteroides Leuco4 or yoghurt starter culture YO-MIX465 (consisting of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus) and their mixture at a mass ratio of 1:4 were evaluated for viscosity, syneresis, texture properties and sensory quality. Compared with YO-MIX465-fermented milk, fermented milk containing Leuconostoc mesenteroides Leuco4 had better water-holding capacity and viscosity and desired viscosity, taste and stability and could meet the requirement of clean-label products due to not containing any food additives.