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Evaluation of dairy product quality taking into account within-lot-variation


Dairy products qualify for financial assistance under CAP provided they meet certain specifications. In many cases compositional requirements are set, these are established as limits. At present these limits are controlled by analysing a limited number of samples taken from a lot. Using this approach it is practically not possible to detect defective units in a lot containing a small number of defective units. Furthermore, evaluation of compositional quality should take into account measurement errors and the unavoidable variations in product composition within a lot. A means of collecting more information on the lot quality is required. Manufactures routinely collect data as part of process quality control. A system based on consideration of factory data, linked with a degree of official control, provides an economical way to gather the information required to assess lot quality with the required degree of assurance.

The overall objective of this project is to investigate the advantages of moving from a system of official control for analysis of dairy products based on analysis of a limited number of samples to a new control system which makes use of the data which is available from the factory.
Particular objectives are:
a) establishment of arithmetic means and standard deviations associated with manufactures within-lot variation, and sampling plans to be respected by the factory;
b) establishment of a procedure for data evaluation based on comparison of manufactures data and official control data;
c) recommendations for improved measures for control of quality of butter and skimmed milk powder submitted to meet specifications.
A survey of the current practices adopted by butter manufacturers has been undertaken and the results considered as part of the approach to sampling plans. Partners have worked with butter manufactures in order to collect factory data. Data have been collected pertaining to measurement error, factory data on within-lot variation, and comparison of factory data with official control data. These are currently being assessed and processed by the statistician.
To meet these objectives partners will liaise with manufacturers to collect data associated with production. These data will be evaluated by a statistician. Analyses will also be undertaken by control authorities, and submitted to the statistician, in order to establish how factory data can be controlled. Finally the recommendations for a practical scheme of auto-control will be made based on acceptance criteria in the light of level of variation within lot observed in practical situations, and the observed differences between results obtained in factories and official control laboratories.

Funding Scheme

CSC - Cost-sharing contracts


Woodthone, Werg's Road
WV6 8TQ Wolverhampton
United Kingdom

Participants (6)

45,Bornsesteeg 45
6700 AE Wageningen
Agrarmarkt Austria
40,Adalbert Stifter Straße
1200 Wien
Danish Veterinary Service - Ministry of Agriculture and Fisheries
2000 Frederiksberg
Danske Mejeriers Fællesorganisation
22,Frederiks Alle
8000 Arhus C
Freie Universität Berlin
14195 Berlin
Intervention Board Executive Agency
United Kingdom
33 Kings Road
RG1 3BU Reading