Reduction of L. monocytogenes due to smoking brined or dry-salted fish

The function sfSmoking() describes the combined effect of smoking brined or salted fish fillets and maturing for 18-24 hours. Based on the literature, different reduction factors of L. monocytogenes are applied to brine-injected fish fillets and dry-salted fillets. Lot-specific log10 reduction values are sampled from normal distributions, attending to the type of salting.

Usage

sfSmoking(
  data = list(),
  saltingType = NULL,
  nLots = NULL,
  sizeLot = NULL,
  rBrineMean = 0.871,
  rBrineSd = 0.807,
  rDrysaltMean = 1.093,
  rDrysaltSd = 0.532
)

Arguments

data

See Lot2LotGen() function.

saltingType

Salting method employed in each of the lots: brined or salted (vector).

nLots

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

sizeLot

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

rBrineMean

(log10) mean of the normal distribution about the log10 reduction in L. monocytogenes in brine-injected fish fillets due to smoking and 18-24-h maturation (scalar).

rBrineSd

(log10) standard deviation of the normal distribution about the log10 reduction in L. monocytogenes in brine-injected fish fillets due to smoking and 18-24-h maturation (scalar).

rDrysaltMean

(log10) mean of the normal distribution about the log10 reduction in L. monocytogenes in dry-salted fish fillets due to smoking and 18-24-h maturation (scalar).

rDrysaltSd

(log10) standard deviation of the normal distribution about the log10 reduction in L. monocytogenes in dry-salted fish fillets due to smoking and 18-24-h maturation (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 fillets after smoking and 18-24-h maturation

pSurvSmoking

Probability of a microbial cell to survive the smoking treatment (vector).

Note

The suggested parameters rBrineMean=0.871 and rBrineSd=0.807 defining the normal distribution about the variability in the log10 reduction in L. monocytogenes in brined-injected fish were modelled using data extracted from Eklund et al. (1995) and Porsby et al. (2008) ; where these authors inoculated L. monocytogenes in smoked salmon through brine injection; submitted samples to cycles of cold-smoking between 6-8 hours; and determined the microbial concentrations after 18-24 hours maturation. The suggested parameters rDrysaltMean=1.093 and rDrysaltSd=0.532 characterising the normal distribution about the variability in the log10 reduction in L. monocytogenes in dry-salted fish were modelled using data from Eklund et al. (1995) , Neunlist et al. (2005) and Porsby et al. (2008) , who performed experiments inoculating inoculated L. monocytogenes on the surface of dry-salted salmon, and quantified the pathogen concentrations after 18-24 hours maturation.

References

Eklund MW, Poysky FT, Paranjpye RN, Lashbrook LC, Peterson ME, Pelroy GA (1995). “Incidence and Sources of Listeria monocytogenes in Cold-Smoked Fishery Products and Processing Plants.” Journal of food protection, 58, 502-508. Wolodzko T (2020). extraDistr: Additional Univariate and Multivariate Distributions. R package version 1.9.1, https://CRAN.R-project.org/package=extraDistr. Neunlist MR, Ralazamahaleo M, Cappelier J, Besnard V, Federighi M, Leroi F (2005). “Effect of salting and cold-smoking process on the culturability, viability, and virulence of Listeria monocytogenes strain Scott A.” Journal of food protection, 68, 85-91. Porsby CH, Vogel BF, Mohr M, Gram L (2008). “Influence of processing steps in cold-smoked salmon production on survival and growth of persistent and presumed non-persistent Listeria monocytogenes.” International Journal of Food Microbiology, 122(3), 287-295. doi:10.1016/j.ijfoodmicro.2008.01.010 . Team RC (2022). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/.

Author

Ursula Gonzales-Barron ubarron@ipb.pt

Examples

dat <- Lot2LotGen(
                  nLots = 50,
                  sizeLot = 100,
                  unitSize = 500,
                  betaAlpha = 0.5112,
                  betaBeta = 9.959,
                  C0MeanLog = 1.023,
                  C0SdLog = 0.3267,
                  propVarInter = 0.7
                  )
smokedfish <- sfSmoking(dat,
                        rBrineMean = 0.871, 
                        rBrineSd = 0.807,
                        rDrysaltMean = 1.093, 
                        rDrysaltSd = 0.532,
                        saltingType = "salted"
                        )
hist(smokedfish$N)