Statistical Distributions Describing Microbial Quality of Surfaces and Foods in Food Service Operations

Abstract

Data on the microbial quality of food service kitchen surfaces and ready-to-eat foods were collected over a period of 10 years in Rutgers University dining halls. Surface bacterial counts, total aerobic plate counts, and total and fecal coliform counts were determined using standard methods. Analysis was performed on foods tested more than 50 times (primarily lunch meats and deli salads) and on surfaces tested more than 500 times (36 different surfaces types, including pastry brushes, cutting boards, and countertops). Histograms and statistical distributions were determined using Microsoft Excel and Palisades Bestfit, respectively. All data could be described by lognormal distributions, once data above and below the lower and upper limits of detection were considered separately. Histograms for surfaces counts contained one peak near 1 CFU/4 cm2. Surfaces with higher levels of contamination tended to be nonmetal, with the exception of buffalo chopper bowls, which commonly had high counts. Mean counts for foods ranged from 2 to 4 log CFU/g, with shrimp salad, roast beef, and bologna having higher means. Coleslaw, macaroni salad, and potato salad (all commercially processed products, not prepared in the dining halls) had lowest overall means. Coliforms were most commonly found in sealeg salad (present in 61% of samples) and least commonly found in coleslaw (present in only 7% of samples). Coliform counts (when present) were highest on average in shrimp salad and lowest in coleslaw. Average coliform counts for most products were typically between 1 and 2 log most probable number per gram. Fecal coliforms were not typically found in any deli salads or lunch meats.

Evaluation of Food Handler Practices and Microbiological Status of Ready-to-Eat Foods in Long-Term Care Facilities in the Andalusia Region of Spain

“…In another study, Sneed et al (49) proposed a standard for food contact surfaces of less than 20 CFU/cm 2 for MAB and less than 10 CFU/cm 2 for Enterobacteriaceae. These authors reported high levels of MAB on durable resin cutting boards (.20 CFU/cm 2 ), similar to those found in our study at facilities B, D, and E. Other researchers (35) reported lower average levels for MAB in cutting boards (10.16 CFU/4 cm 2 ), but 6.7% of samples analyzed had levels above 50 CFU/4 cm 2 . Microorganisms can become lodged in cracks and crevices of cutting boards that are not properly sanitized (53), and the humidity of cutting boards may favor detachment of bacteria from these food contact surfaces when they are swab sampled, enhancing bacterial recovery (32).…”

Microbiological Quality and Risk Factors Related to Sandwiches Served in Bakeries, Cafés, and Sandwich Bars in South Korea

“…Food operation environments have major effects on the microbial contam ination of final food products (7,36), but most previous studies have been concerned with commercially manufac tured and prepacked products sold in retail markets or with RTE foods from street vendors (11,14,17,27,28,39). The present study was conducted to evaluate the microbiological quality of sandwiches prepared on site and served in bakeries, cafes, and sandwich bars.…”

Framework for Microbial Food‐Safety Risk Assessments Amenable to Bayesian Modeling

“…If the dose at the point of consumption is assumed to fit a parametric distribution, then predictive Monte Carlo models can be avoided. While the appropriateness of any parametric distribution must be assessed on a case‐by‐case basis, numerous studies have demonstrated theoretically and empirically that it is reasonable to assume that microbial counts vary according to a lognormal ( 20,31‐33 ) or Poisson‐lognormal distribution. ( 34 ) Furthermore, the lognormal distribution is mathematically convenient and appropriate for modeling the effects of cooking, ( 34 ) growth, ( 35 ) and cross‐contamination.…”