Transport, Marketing, and Retail
90 7.3.2.
Retail Time at Retail
The duration of storage at retail was determined by expert elicitation CFSAN 2008. The minimum, most likely and maximum time that soft-ripened cheese is displayed in the retail
display cabinet were estimated as 1 day, 5 days and 14 days, respectively. This was modeled as:
14 ,
5 ,
~ 1
, ~
tr r
tr
m Triangular
t Uniform
m
.
Temperature at Retail
The temperature of the cheese while on display at retail was taken from measurements collected by the EcoSure network of auditors EcoSure 2008. A description of the study design and the
raw data are available on the FoodRisk.org website.
13
Briefly, trained shoppers were asked to purchase products at retail and to measure the temperatures of these products at the store. A
number of different products were purchased and tested, including cottage cheese, yogurt, and pre-packaged lunch meat or sliced meat. The data collected for semi-solid cottage cheese
displayed in dairy cases at supermarkets were used to derive the parameters for this model, because this is the tested product that was most similar to soft-ripened cheese. To evaluate
product temperature in the display cases, the shoppers were asked to insert a pre-calibrated thermometer into the product immediately after removing it from the display case EcoSure
2008. The summary statistics for the cottage cheese dataset are shown in Table 27.
Table 27 Summary statistics for storage temperature °F for retail semi-solid cottage cheese dairy product, supermarket.
N Mean
Var. Min.
Perc 1
Perc 5
Perc 10
Perc 25
Perc 50
Perc 75
Perc 90
Perc 95
Perc 99
Max
751 39.3
17.8 22
30 32
34 37
39 41
44 46
50 64
EcoSure 2008.
Between store temperature variability was modeled using a lognormal distribution, ignoring the Ecosure 2008 design. The temperatures were converted to T
r
°C from T
rF
°F and the distribution was modeled as:
13
http:foodrisk.orgexclusivesEcoSure assessed 4112012.
91
8 .
60 ,
5 .
28 ,
, ~
ln 32
9 5
σ µ
ormal TruncatedN
T T
T
rF rF
r
− =
where TruncatedNormal µ, σ, 28.5, 60.8 is the normal distribution with a mean µ, a standard
deviation σ, truncated at [28.5; 60.8]°F i.e. [-1.94; 16]°C; µ and σ were estimated from raw
data using a maximum likelihood method.
The description of the sampling design provided with this data set EcoSure 2008 is somewhat brief. This prevents both accurate extrapolation from the sampling data to the corresponding
target population and evaluation of the associated uncertainties. Therefore, an equal unknown weight was assumed for each observation. Moreover, to evaluate the uncertainty of the estimates,
it was assumed that the sample design was as follows: stratification by U.S. state; a random city
× location within state selection with equal probabilities, and a random store type and participant within state
× city × location selection with equal probabilities. The simple random sample standard error for the parameter estimate was scaled by the square root of the design
effect, and the effective degrees of freedom DEFF, number of independently selected clusters, number of strata was used in place of the number of observations in setting the shape and scale
parameter for the sampling distribution for the
µˆ
2
ˆ σ
parameter estimate. Using these assumptions, values for the maximum likelihood estimates and their associated uncertainty are shown in Table
28.
Table 28: Specification of the temperature T
rF
ºF at retail. DEFF
Maximum likelihood estimate Uncertainty distribution ºF
420 µ = 3.6647
σ
2
= 0.01143 µ~Normal3.665, 0.005203
2
σ
2
~[Gamma210, [2.394]
-1
]
-1
ρ µ, σ
2
=0.000022 T
rF
is specified using lnT
rF
~ TruncatedNormal µ, σ
2
, 28.5, 60.8.
Note that no specific information is available on temperature at retail for artisanal or farmstead cheeses.
Contamination at Retail
The microbiological literature suggests that contamination can occur at retail, such as when larger cheeses are cut into portions and repackaged. However, the literature does not describe the
92 frequency and level of contamination that would inform model inputs for that source of
contamination. The soft-ripened cheeses that are this report’s main focus are rarely repackaged at retail.