Modeling logistic performance in quantitative microbial risk assessment

Quality and Operations Management in Food Supply Chains: A Literature Review

We present a literature review on quality and operations management problems in food supply chains. In food industry, the quality of the food products declines over time and should be addressed in the supply chain operations management. Managing food supply chains with operations management methods not only generates economic benefit, but also contributes to environmental and social benefits. The literature on this topic has been burgeoning in the past few years. Since 2005, more than 100 articles have been published on this topic in major operations research and management science journals. In this literature review, we concentrate on the quantitative models in this research field and classify the related articles into four categories, that is, storage problems, distribution problems, marketing problems, and food traceability and safety problems. We hope that this review serves as a reference for interested researchers and a starting point for those who wish to explore it further.

Belgian and Spanish consumption data and consumer handling practices for fresh fruits and vegetables useful for further microbiological and chemical exposure assessment

A consumer survey was organized in Spain and Belgium to obtain consumption data and to gain insight into consumer handling practices for fresh vegetables consumed raw or minimally processed (i.e., heads of leafy greens, bell peppers, tomatoes, fresh herbs, and precut and packed leafy greens) and fruits to be consumed without peeling (i.e., apples, grapes, strawberries, raspberries, other berries, fresh juices, and precut mixed fruit). This information can be used for microbiological and/or chemical food safety research. After extensive cleanup of rough databases for missing and extreme values and age correction, information from 583 respondents from Spain and 1,605 respondents from Belgium (18 to 65 years of age) was retained. Daily intake (grams per day) was calculated taking into account frequency and seasonality of consumption, and distributions were obtained that can be used in quantitative risk assessment for chemical hazards with chronic effects on human health. Data also were recalculated to obtain discrete distributions of consumption per portion and the corresponding frequency of consumption, which can be used in acute microbiological risk assessment or outbreak investigations. The ranked median daily consumption of fruits and vegetables was similar in Spain and Belgium: apple > strawberry > grapes > strawberries and raspberries; and tomatoes > leafy greens > bell peppers > fresh herbs. However, vegetable consumption was higher (in terms of both portion and frequency of consumption) in Spain than in Belgium, whereas the opposite was found for fruit consumption. Regarding consumer handling practices related to storage time and method, Belgian consumers less frequently stored their fresh produce in a refrigerator and did so for shorter times compared with Spanish consumers. Washing practices for lettuce heads and packed leafy greens also were different. The survey revealed differences between these two countries in consumption and consumer handling practices, which can have an impact on outcomes of future microbiological or chemical risk assessment studies.

An educationally inspired illustration of two-dimensional Quantitative Microbiological Risk Assessment (QMRA) and sensitivity analysis

Quantitative Microbiological Risk Assessment (QMRA) is a structured methodology used to assess the risk involved by ingestion of a pathogen. It applies mathematical models combined with an accurate exploitation of data sets, represented by distributions and - in the case of two-dimensional Monte Carlo simulations - their hyperparameters. This research aims to highlight background information, assumptions and truncations of a two-dimensional QMRA and advanced sensitivity analysis. We believe that such a detailed listing is not always clearly presented in actual risk assessment studies, while it is essential to ensure reliable and realistic simulations and interpretations. As a case-study, we are considering the occurrence of listeriosis in smoked fish products in Belgium during the period 2008-2009, using two-dimensional Monte Carlo and two sensitivity analysis methods (Spearman correlation and Sobol sensitivity indices) to estimate the most relevant factors of the final risk estimate. A risk estimate of 0.018% per consumption of contaminated smoked fish by an immunocompromised person was obtained. The final estimate of listeriosis cases (23) is within the actual reported result obtained for the same period and for the same population. Variability on the final risk estimate is determined by the variability regarding (i) consumer refrigerator temperatures, (ii) the reference growth rate of L. monocytogenes, (iii) the minimum growth temperature of L. monocytogenes and (iv) consumer portion size. Variability regarding the initial contamination level of L. monocytogenes tends to appear as a determinant of risk variability only when the minimum growth temperature is not included in the sensitivity analysis; when it is included the impact regarding the variability on the initial contamination level of L. monocytogenes is disappearing. Uncertainty determinants of the final risk indicated the need of gathering more information on the reference growth rate and the minimum growth temperature of L. monocytogenes. Uncertainty in the dose-response relationship was not included in the analysis, hence the level of its influence cannot be assessed in the present research. Finally, a baseline global workflow for QMRA and sensitivity analysis is proposed.

van der Vorst J. Effective sourcing strategies for perishable product supply chains

Purpose

– The purpose of this paper is to assess whether an existing sourcing strategy can effectively supply products of appropriate quality with acceptable levels of product waste if applied to an international perishable product supply chain. The authors also analyse whether the effectiveness of this sourcing strategy can be improved by including costs for expected shelf life losses while generating order policies.

Design/methodology/approach

– The performance of sourcing strategies is examined in a prototype international strawberry supply chain. Appropriate order policies were determined using parameters both with and without costs for expected shelf life losses. Shelf life losses during transport and storage were predicted using microbiological growth models. The performance of the resulting policies was assessed using a hybrid discrete event chain simulation model that includes continuous quality decay.

Findings

– The study's findings reveal that the order policies obtained with standard cost parameters result in poor product quality and large amounts of product waste. Also, including costs for expected shelf life losses in sourcing strategies significantly reduces product waste and improves product quality, although transportation costs rise.

Practical implications

– The study shows that in perishable product supply chain design a trade-off should be made between transportation costs, shortage costs, inventory costs, product waste, and expected shelf life losses.

Originality/value

– By presenting a generically applicable methodology for perishable product supply chain design, the authors contribute to research and practice efforts to reduce food waste. Furthermore, product quality information is included in supply chain network design, a research area that is still in its infancy.

Shelf life modelling for first-expired-first-out warehouse management

In the supply chain of perishable food products, large losses are incurred between farm and fork. Given the limited land resources and an ever-growing population, the food supply chain is faced with the challenge of increasing its handling efficiency and minimizing post-harvest food losses. Huge value can be added by optimizing warehouse management systems, taking into account the estimated remaining shelf life of the product, and matching it to the requirements of the subsequent part of the handling chain. This contribution focuses on how model approaches estimating quality changes and remaining shelf life can be combined in optimizing first-expired-first-out cold chain management strategies for perishable products. To this end, shelf-life-related performance indicators are used to introduce remaining shelf life and product quality in the cost function when optimizing the supply chain. A combinatorial exhaustive-search algorithm is shown to be feasible as the complexity of the optimization problem is sufficiently low for the size and properties of a typical commercial cold chain. The estimated shelf life distances for a particular batch can thus be taken as a guide to optimize logistics.