摘要
以涩柿为原料,结合柿饼生产工艺,研究烘制、揉捏、熏硫、贮藏等主要生产环节柿饼表面大肠杆菌的污染及消长规律,获得控制柿饼表面大肠杆菌污染和繁殖的方法。结果表明:柿果含糖量越高,柿饼出霜量越大,柿霜的形成可有效抑制大肠杆菌的生长;柿饼烘制中,热风烘制的柿饼大肠杆菌污染程度明显低于自然晾晒的柿饼;烘制前熏硫处理可有效抑制大肠杆菌在柿饼表面的生长,并起到护色、防蝇虫作用,以15 g/m~3剂量的硫熏蒸柿果20 min为宜,柿饼最终残硫量仅为13.8 mg/kg,符合国家卫生标准(残硫量不得超过100.0 mg/kg);选择50～55～50℃的变温烘制方式,不仅柿饼干制效果好,而且大肠杆菌污染程度低;采用充N_2、充CO_2和抽真空方式包装柿饼,均能很好抑制柿饼表面大肠杆菌的生长,但抽真空方式较为实用;柿饼在贮藏过程中,保持柿饼含水量约为28%,温度为-5～5℃范围内,更有利于出霜和抑制其表面大肠杆菌的污染和生长;在用热风烘制柿饼时,用10%乳酸以10 mL/m~3的用量熏蒸干燥室20 min,能减少大肠杆菌的污染;防腐剂对柿饼表面大肠杆菌有一定的抑制作用,其强弱顺序为:山梨酸>山梨酸钾>亚硫酸氢钠>苯甲酸>苯甲酸钠,使用浓度分别为山梨酸400 mg/L、山梨酸钾450 mg/L、亚硫酸氢钠500 mg/L、苯甲酸550 mg/L和苯甲酸钠600 mg/L。
To investigate with astringent persimmon as raw materials, combined with dried persimmon production technology, study baking, kneading, smoking sulfur, storing and other treatments the dynamic changes of E. coli are studied during these main working procedures, and to explore the methods how to control these microbes and prevent dried persimmons from contaminating. The results showed that the higher the total sugar content of persimmon fruits were, the more frost on the surface of dried persimmons had. The formation of frost could effectively inhibit the growth of E. coli. The contamination degrees of E. coli. on the surface of persimmons dried by hot air were obviously lower than that of persimmons dried in the shade. Hot air drying could shorten the processing time from 20 d to about 8 d, compared with shade drying. Sulfuring the persimmon fruits for 20 min(with the dosage of 15 g/m~3) before drying could not only effectively block the reproduction of E. coli, but also prevent products from browning and damaging by insects. The residual sulfur content of dried persimmons was only 13.8 mg/kg, which was in line with state health standards(no more than 100.0 mg/kg). In contrast with constant temperature drying, variable temperature drying(50～55～50 ℃) worked better, which could also reduce the pollution of E. coli. Compared with the control, the growth of E. coli was evidently suppressed no matter vacuum packaging or packaging with N_2, CO_2, while vacuum packaging was more practical than others. In order to guarantee the quality of the dried persimmons, the optimum operation was as follows: maintaining the water content of dried persimmons at about 28%, and the storage temperature at-5～5℃, under which situations the degree of frost was heavy and the growth of E. coli on the surface of dried persimmons was effectively controlled. The sanitary conditions of drying chamber could also affect the growth of E. coli. Fumigating the drying room with 10% lactic acid(with the dosage of 10 mL/m~3) for 20 min before drying could reduce the pollution of E. coli. Preservatives had a certain inhibitory effect on E. coli, with the pecking orders as follows: sorbic acid > potassium sorbate > sodium bisulfite > benzoic acid> sodium benzoate. And the working concentrations for sorbic acid, potassium sorbate, sodium bisulfite, benzoic acid, sodium benzoate were 400, 450, 500, 550, 600 mg/L, respectively.
引文
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