Verifying apple cider plant sanitation and hazard analysis critical control point programs: Choice of indicator bacteria and testing methods

The objectives of this study were (i) to evaluate the survival of coliforms , Escherichia coli, and enterococci in refrigerated apple cider; (ii) to de velop simple and inexpensive presumptive methods for detection of these bac teria; (iii) to perform a field survey to determine the prevalence of these bacteria on apples and in apple cider; and (iv) based on our results, to r ecommend the most useful of these three indicator groups for use in verifyi ng apple cider processing plant sanitation and hazard analysis critical con trol point (HACCP) programs. Eight of 10 coliform strains (5 E coli, 1 Ente robacter aerogenes, and 2 Klebsiella spp.) inoculated into preservative-fre e apple cider (pH 3.4, 13.3 degrees Brix) survived well at 4 degrees C for 6 days (less than or equal to 3.0 log(10) CFU/ml decrease). Of 21 enterococ ci strains (Enterococcus faecalis, E. faecium, and E. durans), only 2 E. du rans and 3 E. faecium strains survived well. Simple broth-based colorimetri c methods were developed that detected the presence of similar to 10 cells of coliforms or enterococci. In three field studies, samples of unwashed ap ples (drops and picked), washed apples, and freshly pressed cider were pres umptively analyzed for total coliforms, E. coli, and enterococci using qual itative and/or quantitative methods. Drop apples were more likely than pick ed apples to be contaminated with E. coli (26.7% vs. 0%) and enterococci (2 0% vs. 0%). Washing had little effect on coliform populations and in one fi eld study was associated with increased numbers. Total coliform populations in cider ranged from <1 CFU/ml to >738 most probable number/ml, depending on the enumeration method used and the sample origin. E. coli was not recov ered from washed apples or cider, but enterococci were present on 13% of wa shed apple samples. The qualitative coliform method successfully detected t hese bacteria on apples and in cider. Based on its exclusively fecal origin , good survival in apple cider, and association with drop apples, we conclu de that E. coli is the most useful organism for verifying apple cider sanit ation and HACCP programs.