Investigation Of Elements, Optimization Of Coloring Process And Analysis Of Odor Components In Stinky Tofu

South stinky tofu is one of the unique snacks in China,of which Changsha fried stinky tofu is especially favored by a vast number of consumers.The production process of Changsha fried stinky tofu in the market is simple,including the centralized production of brine,unified brewing,unified packaging,distribution to the stall hawkers.However,numerous workshops are engaged in this process,but the production processes vary between diffrerent workshops,resulting in the variety of stinky tofu is qualities.Additionally,it is diffcult to exert standard and comprehensive administration rules on these street vendors.Moreover,some fraudulent sellers illegally add many unhealthy ingredients during the production process.These unfavorable phenomenon mentioned above may seriously prevent the development of stinky tofu industry.In order to promote the development of fried tofu industry in Changsha,this paper investigated the partial element concentration and odor components of stinky tofu and brine,and made preliminary optimization on the coloring process of stinky tofu.The results are summarized as follows:1?The concentration of different chemical elements such as Pb,Cr,Ca,Mg,Al,Cu,Mn,Zn,Fe in Changsha stinky tofu before frying and after from 11 different workshops and the five different levels of brine in Changsha were determined by inductively coupled plasma mass spectrometry(ICP-MS).The results showed that the detection concentrations of As,Pb,Cr,three kinds of health indicators(?GB 2711-2003 non-fermented soybean products and gluten hygiene standards?)exceeded the standard concentration.Among them,Pb did not exceed the standard concentration;As exceeded the standard: No.4 before and after frying,No.5 fried;Cr exceeded the standard: No.1,No.2 before and after frying,No.3 before and after frying,No.4,No.9 before and after frying,No.11 fried and No.13 fried.The average level of Ca and Mg in the human body was 1375.78 mg/Kg and 447.08 mg/Kg;the average level of trace elements Zn,Fe,Cu and Mn were 24.51 mg/Kg,411.68 mg/Kg,4.79 mg/Kg,and 14.86 mg/Kg,respectively;the average content of non-essential element Al is 8.33mg/Kg.Determination of the concentration of elements showed that the normal consumption of stinky tofu did not exceed the limits of the daily intake of the human body.The elements in brines were mainly derived from the raw materials of brine formula: Calcium concentration in raw materials of tofu and snail meat was high,resulting in the high Calcium concentration in brine.For example,Calcium concentration in No.2 brine was as high as1110.32 mg/Kg.2?In this paper,the single factor and orthogonal optimization experiments on the tofu of the color process were investigated.The results showed that the best conditions for the color of stinky tofu could be set up as following:adding ferrous sulfate at the concentration of 0.15 g/L,tea powder dosage 4 g,temperature 90 ?,constant temperature soaking time30 min.Under these conditions,the different of the color of the stinky tofu before and after the ?L is 0.31,while can achieve the best color effect.3?The volatile components of stinky tofu and brine were identified by solid phase microextraction(GC-MS),and the volatile components of brine in different fermentation stages were investigated before and after brine soaking.The results showed that after the soaking of dipped in brine,the ester composition disappeared.The volatile components of tofu the volatile ingredients of the tofu that were not soaked in brine,such as n-hexane,n-hexanol and ethyl butyrate.The stinky tofu volatile components after soaking mainly contained n-hexanol,n-hexane,and chloroform.The main material in brine at different stages of fermentation of were different: the main volatile component in the brine at the former medium-term included naphthalene and benzene substances,specifically 2-methyl naphthalene,1-methyl naphthalene,phenol,2-methyl naphthalene,1-methyl naphthalene,and pentamethyl while that in brine at the late stage included Hexanoic acid,phenol,4-methylphenol.All brines at different stages contained 3-methyl indole,indicating it may be an important component of volatile substances in brine.