Cross-contamination during slicing of raw fish or processed fillets

The function sfSlicer() mimics the transfer of L. monocytogenes during the slicing process of raw whole fish or of processed fish fillets, using the compartmental model published in Hoelzer et al. (2012) , which is defined by two variability distributions: a, the transfer rate between slicer blade and product, and e, the transfer rate from the original contamination to the slicing system. Transfer coefficients are sampled for every lot.

Usage

sfSlicer(
  data = list(),
  nLots = NULL,
  sizeLot = NULL,
  wSlices,
  initSlicer = 10,
  aParamLoc = 0.07,
  aParamScale = 0.03,
  aParamMax = 0.5,
  eMean = -2.12,
  eSd = 0.85
)

Arguments

data

a list of

N

(CFU) A matrix of size nLots lots by sizeLot units containing the numbers of L. monocytogenes in/on the pre-slicing units;

workDone

Work done is optional (scalar, vector or matrix).

nLots

Number of lots sampled or size of the Monte Carlo simulation (scalar).

sizeLot

Number of units or portions produced in a lot (scalar).

wSlices

Weight of a slice that can be obtained from one unit (scalar).

initSlicer

(CFU) Initial contamination of the slicer (scalar or vector). Default is 0.

aParamLoc

Location parameter of the logistic distribution of a, the major parameter of the system (scalar).

aParamScale

Scale parameter of the logistic distribution of a, the major parameter of the system (scalar).

aParamMax

Maximum value used to truncate the logistic distribution of a, the major parameter of the system (scalar).

eMean

Mean of the log10 distribution of the e parameter (scalar)

eSd

Standard deviation of the log10 distribution of the e parameter (scalar).

Value

A list of two elements:

N

(CFU) A matrix of size nLots lots by sizeLot units containing the numbers of L. monocytogenes in salted fish;

workDone

Updated work done (scalar, vector or matrix).

Note

The parameters of the distributions about the slicer transfer coefficients a and e are set to the values determined in Hoelzer et al. (2012) ; although the user can alter or update any of them. The number of columns of the input matrix N is increased by a factor of nbSlices. The code is written so that if a workDone object is element of data, it is updated as needed. When this function is used for slicing processed fillets, nbSlices can be assumed to be 40 (slices per fillet), according to Aarnisalo (2007) .

References

Aarnisalo KSSRLTM (2007). “Modelling transfer of Listeria monocytogenes during slicing of 'gravad' salmon.” International Journal of Food Microbiology, 118(1), 69--78. ISSN 0168-1605 0168-1605, doi:10.1016/j.ijfoodmicro.2007.06.017 .

Wolodzko T (2020). extraDistr: Additional Univariate and Multivariate Distributions. R package version 1.9.1, https://CRAN.R-project.org/package=extraDistr.

Hoelzer K, Pouillot R, Gallagher D, Silverman MB, Kause J, Dennis SB (2012). “Estimation of Listeria monocytogenes transfer coefficients and efficacy of bacterial removal through cleaning and sanitation.” International Journal of Food Microbiology, 157, 267-77. doi:10.1016/j.ijfoodmicro.2012.05.019 .

Team RC (2022). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/.

Author

Regis Pouillot rpouillot.work@gmail.com

Examples

nLots <- 1000
sizeLot <- 1000
N <- matrix(1E5, nc = nLots, nr = sizeLot)
data <- list(N = N, unitSize = 1300)

wSlices <- 20 # slice/fillet Aarnisalo 2007
Res <- sfSlicer(data, wSlices = wSlices, initSlicer = 0)
#> Warning: argument is not numeric or logical: returning NA
plot(log10(Res$N[1, ]), ylab = "log10 bacteria on each slices")