Effectiveness of spraying with tween 20 and lactic acid in decontaminating inoculated Escherichia coli O157:H7 and indigenous Escherichia coli biotype I on beef

Beef carcass quarters and fat-covered subprimal cuts were suspended vertically and inoculated with a bovine manure slurry, containing a five-strain mixture of Escherichia coli O157:H7 to deliver about 4 to 5 log(10) CFU/cm(2). To identify treatments that would improve the effectiveness of spraying with lactic acid (LA), the inoculated quarters and cuts were treated as follows: experiment A, (i) not treated (control), (ii) sprayed with 2% (vol/vol) LA, (iii) tempered at 21degreesC for 4 h. and (iv) tempered and then sprayed with LA; experiment B, (v) sprayed with water. (vi) sprayed with LA. (vii) sprayed with LA containing 0.5% (vol/vol) sodium benzoate (SB), and (viii) sprayed with LA containing SB and 5% (vol/vol) Tween 20 (TW20): and experiment C, (ix) sprayed with water (no prespray), (x) presprayed with TW20 and then sprayed with LA. and (xi) presprayed with T-W20 and then sprayed with LA containing SB, In experiment A, praying carcasses with LA significantly (P < 0.05) reduced the numbers of E. coli Biotype I and serotype O157:H7 after I and 3 days of storage. respectively. The tempering process employed did not affect the effectiveness of the LA spray on either type of E. coli, In experiment B. there was no significant difference in the reduction of E. coli O157:H7 on subprimal cut, sprayed with water and that on cut, sprayed with LA alone or with LA in combination with SB and TWA20 after I or 3 days of storage (total reductions ranged from about 1.6 to 2.8 log(10) CFU/cm(2)). In experiment C. prespraying subprimal Cuts with TW20 significantly (P < 0.05) increased the effectiveness of LA (reductions of 2.8 and 3.2 log(10) CFU/cm(2), respectively) and that of LA with SB (reductions of 2.6 and 3.3 log(10) CFU/cm(2), respectively) compared with spraying with, water alone (reductions of ca. 1.0 and 2.0 log(10) CFU/cm(2), respectively) after I and 3 days of storage, respectively. In a separate experiment, the incorporation of T-W20 (0.1 or 0.25%) into buffered peptone water prior to the maceration of excised carcass surface samples resulted in the recovery of significantly larger numbers (ca. 5.1 to 5.2 log(10) CFU/cm2) of E. coli O157:H7 cells than did the control treatment without added TW20 (ca. 3.8 to 4.6 log(10) CFT-T/cm(2)). These results demonstrate that the treatment of beef carcasses with LA reduces the number of viable E. coli O157:H7 cells and that this inactivation or removal by LA is enhanced by prespraying of the carcass with a 5% solution of TW20.