Study On The Detection And Generation Rules Of The BTEX In Yogurt

BTEX are a class of pollutants that harmful to the environment and human health. It maily exist in air and soil. Now some studies have found that BTEX are also present in foods such as beverages, but that why they are there is stll unclear. This paper mainly studied the situation of the presence of the BTEX in yogurt. Because of the situation that dairy safety issues have become increasingly prominent, studying the regulation of the BTEX in yogurt can provide some reference factors on actual production.This paper selected the BTEX(benzene, toluene, xylene, acetophenone) as the research object to establish the qualitative and quantitative detection method of BTEX in yogurt using headspace solid-phase microextraction and gas chromatography mass spectrometry technology. Headspace solid-phase microextraction conditions:sample volume,10 mL; amount of NaCl,2.0 g; extraction time,20 min; extraction temperature,60 ℃. In this paper, we used relative correction factor quantitative method for the quantitative analysis of BTEX. We used chlorobenzene as the internal standard substance, the realative correction factors of benzene, toluene, p(m)-xylene, o-xylene, acetophenone were in turn 10.87,3.07, 0.34,0.54,4.867.The recoveries of BTEX are 82%-104%, RSD were less than 4%.The experiment shows that the content of the BTEX in yogurt femented by Streptococcus thermophilus is higher than when the yogurt are femented by Lactobacillus bulgaricus. When it is about after ripening 24h, the content of the BTEX reaches the maximun. When the proportion of the two strains changes, BTEX are detected. And considered the other factors, it shows that the optimal proportion is:Streptococcus thermophilus:Lactobacillus bulgaricus=1:1.The study shows that when adding the bifidobacteria as the strater, it can inhibit the production of the BTEX, but its inhibitory mechanism is not clear.Then we selected six kinds of commercialization of starter cultures and detected the production of the BTEX. It showes that the composition of the starter has different effects on the production of the BTEX. It can be infered that the fermented strains are a key factor to the production of the BTEX in yogurt. But overall, the content of the BTEX in yogurt is not high, it has no effect on human health.Then we discussed when it is added the amino acids with aromatic ring such as phenylalanine, tyrosine, tryptophan whether the production of the BTEX changes. It can get the preliminary conclusion that phenylalanine can promote the generation of acetophenone but tyrosine and tryptophan have no effect on it.