Acceptance sampling for food quality assurance : this dissertation is submitted for the degree of Doctor of Philosophy in Statistics, Institute of Fundamental Sciences, Massey University
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Date
2017
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Massey University
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Abstract
Acceptance sampling plays a crucial role in food quality assurance. However, safety inspection
represents a substantial economic burden due to the testing costs and the number of quality
characteristics involved. This thesis presents six pieces of work on the design of attribute and
variables sampling inspection plans for food safety and quality. Several sampling plans are
introduced with the aims of providing a better protection for the consumers and reducing the
sample sizes. The effect of factors such as the spatial distribution of microorganisms and the
analytical unit amount is discussed. The quality in accepted batches has also been studied,
which is relevant for assessing the impact of the product in the public health system. Optimum
design of sampling plans for bulk materials is considered and different scenarios in terms of
mixing efficiency are evaluated. Single and two-stage sampling plans based on compressed
limits are introduced. Other issues such as the effect of imperfect testing and the robustness
of the plan have been also discussed. The use of the techniques is illustrated with practical
examples. We considered numerous probability models for fitting aerobic plate counts and
presence-absence data from milk powder samples. The suggested techniques have been found to
provide a substantial sampling economy, reducing the sample size by a factor between 20 and 80%
(when compared to plans recommended by the International Commission on Microbiological
Specification for Food (ICMSF) and the CODEX Alimentarius). Free software and apps have
been published, allowing practitioners to design more stringent sampling plans.
Keywords:
Bulk material, Composite samples, Compressed limit, Consumer Protection, Double sampling
plan, Food safety, Measurement errors, Microbiological testing, Sampling inspection plan.
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Keywords
Food, Quality, Analysis, Sampling, Sampling (Statistics), Research Subject Categories::MATHEMATICS::Applied mathematics::Mathematical statistics, Bulk material, Composite samples, Compressed limit, Consumer protection, Double sampling plan, Food safety, Measurement errors, Microbiological testing, Sampling inspection plan