Abstract:
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/m3) 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 N2, CO2 , 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/m3) 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.
